WO2024149434A1

WO2024149434A1 - System and method for optimizing combustion in a boiler

Info

Publication number: WO2024149434A1
Application number: PCT/EP2023/025477
Authority: WO
Inventors: Allan Gunn Ferry; Oleg KUKAR
Original assignee: General Electric Technology Gmbh
Priority date: 2023-01-13
Filing date: 2023-11-13
Publication date: 2024-07-18

Abstract

A system (62) and method for optimizing combustion in boiler (12) is described. The optimization of the combustion in the boiler (12) involves obtaining various data relating to the flow of fuel and air to burners of the boiler and the flame in the burner zone (21) of the boiler (12) that is generated from the introduction of the fuel and air into the burner zone. The data is used to determine air flows to the burners. The data and air flows are used to balance air and fuel at individual burners by manipulating air to match the fuel flow. The balancing of air and fuel at individual burners by manipulating air to match the fuel flow uses a guided search optimization algorithm that mixes stoichiometry determinations with a custom search algorithm that accounts for measurement inaccuracies and unexpected interactions between burners.

Description

SYSTEM AND METHOD FOR OPTIMIZING COMBUSTION IN A BOILER

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR

DEVELOPMENT

[0001] This invention was made with government support under DE- FE0031546 awarded by the U.S. Department of Energy. The government has certain rights in the invention.

BACKGROUND

TECHNICAL FIELD

[0002] Embodiments of this disclosure relate generally to combustion systems and, more particularly, to a system and method for optimizing combustion in a boiler such as for example, a tangentially-fired (T-fired) boiler and a wall-fired boiler.

DISCUSSION OF ART

[0003] In general, a boiler includes a furnace in which fuel is burned to create thermal energy or heat. The fuel, which can be pulverized solid fuel such as coal, or liquid or gaseous fuels, is typically provided to the furnace as a mix of fuel and air.

Burners located on one or more walls of the boiler such as at the comers in the case of a T-fired boiler or on a single or opposing walls in the case of a wall-fired boiler, introduce the mix of the fuel and air into the furnace for combustion and generation of a flame. The flame resulting from the combustion of the fuel and air creates the thermal energy. The thermal energy is used to heat a liquid or vapor such as water or steam in waterwall tubes that line the walls of the furnace. The heating of the liquid or vapor in the waterwall tubes leads to the generation of a steam which can be made to flow to a steam turbine to generate electricity or provide heat for other purposes.

[0004] Power plant operators that use boilers such as coal-fired boilers for steam generation face challenges on multiple fronts. With the increase of renewables on the grid, plants designed for base load operations now cycle more often with output ranges from minimum load to full capacity and in some cases, shutdown and start more frequently. Also, variations in coal and gas prices in some markets along with changing regulatory requirements are placing new demands on plant operators. Further, these power plants must maintain stable combustion for power generation at lower output levels than what was historically necessary.

[0005] With coal based power expected to continue to contribute a significant amount of the world’s electricity, power plant operators seek solutions to improve plant efficiency while controlling emissions. Combustion optimization is one approach that is used to improve efficiency and lower emissions of a boiler such as a coal-fired boiler deployed in a typical coal-fired steam plant. Given the number of variables at play in a coal-fired steam plant, combustion optimization generally involves the use of software and analytics to gain an understanding of the many variables and their dependencies, process states, performance impacts and costs. [0006] Typical combustion optimization solutions that are available to plant operators implement this understanding in a model and use it with an optimization search engine. The boiler model is frequently a neural network model, but other model types are used. The optimization search engine often relies on well-known search techniques that can include linear programming, particle swarm optimization, or genetic algorithm searching among others. In operation, the optimization search engine tries different combinations of boiler settings using the model to generate a listing of settings that give good results on the model. The boiler settings that give good results on the model are then applied to the boiler controls.

[0007] There are several issues with these combustion optimization approaches that rely on a boiler model and an optimization search engine. For example, there can be accuracy issues with the boiler model due to changes in boiler equipment condition, fuel, or other environmental conditions. Consequently, the boiler model needs to undergo retuning to account for these changes that can lead to inaccuracy in the model. In addition, these conventional combustion optimization approaches typically manipulate primary and secondary air flows, air flow by elevation and/or corner, and burner tilts, but do not manipulate individual air dampers for consistent stoichiometry at individual burners because the boiler models do not include this level of detail. Decreasing the amount of excess air available for combustion typically decreases nitrous oxides (NOx) emissions while simultaneously increasing carbon monoxide (CO) emissions Conversely, increasing the amount of excess air available for combustion typically increases NOx emissions while decreasing CO emissions. This occurs because localized combustion zones that are low in oxygen from the air partially combust carbon to carbon monoxide (CO) instead of carbon dioxide (CO2). Combustion zones that are high in air convert a larger part of the nitrogen and oxygen in the air to nitrogen oxides (NOx) at high temperatures. Moreover, these combustion optimization approaches typically focus on nitrous oxides (NOx) emissions or boiler efficiency and not on low boiler loads and flame stability. Also, these combustion optimization approaches require a wide range of historical operating data to construct and tune the boiler model. [0008] Other combustion optimization approaches have been tried but they are not widely in use as compared to those that rely on a boiler model and an optimization search engine. One such approach entails coal flow balancing systems, but these systems suffer from erosion issues and require significant maintenance.

BRIEF DESCRIPTION

[0009] The following presents a simplified summary of the disclosed subject matter in order to provide a basic understanding of some aspects of the various embodiments described herein. This summary is not an extensive overview of the various embodiments. It is not intended to exclusively identify key features or essential features of the claimed subject matter set forth in the Claims, nor is it intended as an aid in determining the scope of the claimed subject matter. Its sole purpose is to present some concepts of the disclosure in a streamlined form as a prelude to the more detailed description that is presented later.

[0010] The aforementioned issues associated with combustion optimization approaches that rely on a boiler model and an optimization search engine create the need for a different methodology for optimizing the combustion of a boiler used in a power plant or even in an industrial plant that uses a boiler for steam generation. Embodiments described herein provide a solution that obviate the concerns with combustion optimization approaches that rely on a conventional boiler model and an optimization search engine. The solution provided by the embodiments includes a system and a method for combustion optimization in a boiler such as a T-fired boiler and a wall-fired boiler that fire fuels such as for example coal, or liquid or gaseous fuels in a power plant and an industrial plant. [0011] In the various embodiments, measured fuel flows, air flows, air flow control device data, flame scan data and flue gas properties data can be used to identify a local stoichiometry (air-to-fuel ratio) near each of the burners. Air flows are adjusted per determined biases for attaining more even local stoichiometry near each burner as they all contribute to a single merged fireball in the case of a T-fired boiler or multiple flames in the case of a wall-fired boiler. In one embodiment, a guided search optimization algorithm can be utilized to perform the combustion optimization. The guided search optimization algorithm combines a physics-based approach that involves a mix of measured and/or calculated stoichiometry of the burners in the boiler with a search algorithm customized to find operational biases that can be applied to one or more of the burners to yield better combustion operation results for the boiler while accounting for measurement inaccuracies, equipment condition changes, and unexpected interactions between burners as the operational biases are determined and evaluated. The combustion before and after each adjustment is evaluated using a variety of higher level combustion measurements including one or more of the level and distribution of combustion gas species, temperature profile, and flame stability measurements. More even local stoichiometry results in simultaneous lowering of carbon monoxide (CO) and NOx emissions by reducing localized combustion zones that are significantly higher or lower in air compared to the fuel available. More even local stoichiometry also results in better flame stability, especially at low boiler loads.

[0012] In addition to simultaneous lowering of CO and NOx emissions and providing for better flame stability, the system and method of the various embodiments provide other advantages. For example, these embodiments can help reduce minimum boiler load in response to intermittent renewable energy with better low-load flame stability. Also, the embodiments can help increase efficiency at higher boiler loads to reduce operating costs and emissions by reducing excess air. In addition, fuel flow sensors, air flow sensors, flue gas sensors, and flame scanners that can be used in the embodiments can provide more accurate measurements of fuel flow and air flow supporting even burner stoichiometry. By using a guided search optimization algorithm, the embodiments can provide an improved response to unexpected boiler behavior, fuel changes, and operating modes. Additionally, because a physics-based approach is used with the embodiments and not a boiler- model-based methodology, periodic retuning of the boiler model to account for inaccuracies in the model that arise over time can be avoided.

[0013] In accordance with a first embodiment, a system is provided. The system of this embodiment comprises: a boiler having a furnace with a burner zone for combustion of fuel and air from which flue gases are produced, the boiler including one of a tangentially-fired (T-fired) boiler and a wall-fired boiler; a plurality of burners located about the boiler that define an arrangement of fuel and air introduction locations for introducing a mix of primary fuel and air into the burner zone to generate a flame therein, each of the burners including a fuel nozzle operative to provide a stream of the primary fuel and air into the burner zone; a plurality of auxiliary air nozzles located about the plurality of burners that are operative to supply a stream of auxiliary air into the burner zone for contribution in the combustion with the primary fuel and air; a plurality of air flow control devices to control the supply of selected streams of auxiliary air into the burner zone by the plurality of auxiliary air nozzles; a plurality of fuel flow sensors to obtain measurements of the flow of the primary fuel to the plurality of burners, each of the fuel flow sensors operative to obtain real-time measurements of the flow of the primary fuel that is supplied to one of the plurality of burners via a corresponding fuel nozzle; one or more auxiliary air flow sensors to obtain measurements of the flow of the auxiliary air supplied into the burner zone by one or more of the plurality of auxiliary air nozzles, each of the auxiliary air flow sensors operative to obtain realtime measurements of the flow of the auxiliary air that is supplied into the burner zone by the one or more of the plurality of auxiliary air nozzles; a plurality of flame scanners to obtain flame scan data of the flame in the burner zone; a plurality of flue gas sensors operative to obtain measurements of a plurality of properties associated with the flue gases, the measurements of the plurality of properties indicative of the combustion that occurred in the burner zone, each of the flue gas sensors operative to obtain measurements of at least one of the properties; and a controller operative to optimize the combustion of the fuel and air in the burner zone as a function of information provided by the plurality of fuel flow sensors, the one or more auxiliary air flow sensors, the plurality of flame scanners, the plurality of flue gas sensors and the plurality of air flow control devices, wherein the controller includes a guided search optimization algorithm that is configured to mix measured and/or calculated stoichiometry of the burners in the boiler with a search algorithm customized to find operational biases that are applied to one or more of the burners to yield better combustion operation results for the boiler, while accounting for measurement inaccuracies and unexpected interactions between burners as the operational biases are determined and evaluated.

[0014] In accordance with a second embodiment, a method for optimizing combustion in a boiler is provided. The boiler includes a furnace with a burner zone for combustion of fuel and air from which flue gases are produced, a plurality of burners with each including a fuel nozzle operative to provide a stream of primary fuel and air into the burner zone to generate a flame therein, a plurality of auxiliary air nozzles located about the plurality of burners that are operative to supply a stream of auxiliary air into the burner zone for contribution in the combustion with the primary fuel and air, a plurality of air flow control devices to control the supply of selected streams of auxiliary air into the burner zone by the plurality of auxiliary air nozzles, a plurality of fuel flow sensors to obtain measurements of the flow of the fuel to the plurality of burners, one or more auxiliary air flow sensors to obtain measurements of the flow of the auxiliary air supplied into the burner zone by one or more of the plurality of auxiliary air nozzles, a plurality of flame scanners to obtain flame scan data of the flame in the burner zone, a plurality of flue gas sensors operative to obtain measurements of a plurality of properties associated with the flue gases, a controller operative to perform the method for optimizing the combustion of the boiler as a function of fuel flow, air flows, flame data, flue gas data and information relating to plurality of air flow control devices. In this embodiment, the method comprises: determining an amount of air near each of the burners; determining air-to-fuel ratios near each of the burners; determining operational biases that redistribute air through or near one or more burners to be more consistent with the air-to-fuel ratios with other burners while maintaining approximately the same amount of air at each elevation level of a vertical furnace in the T-fired boiler or each longitudinal distance from the burners of a horizontal furnace in a wall-fired boiler; and applying the operational biases to or near one or more of the burners.

DRAWINGS [0015] The present invention will be better understood from reading the following description of non-limiting embodiments, with reference to the attached drawings, wherein below:

[0016] FIG. 1 is a simplified schematic representation of a fuel-fired boiler system that produces steam that can be used in power generation applications, of which a system and method for optimizing combustion in a boiler according to the various embodiments of the invention can be deployed;

[0017] FIG. 2 is a schematic representation of further details of a furnace of a boiler like that depicted in FIG.1 with an example of a configuration of windboxes on the walls having air and fuel compartments that inject a mix of air and fuel into the furnace for combustion, of which the combustion can be optimized according to the various embodiments of the invention;

[0018] FIG. 3 is a schematic representation of a system for optimizing combustion in a boiler like that depicted in FIGS. 1 and 2 according to an embodiment of the invention;

[0019] FIG. 4 is a block diagram showing more of the details of the controller depicted in FIG. 3 according to an embodiment of the invention;

[0020] FIG. 5 is a flow chart describing a method for optimizing combustion in a T-fired boiler according to an embodiment of the invention;

[0021] FIG. 6 is a flow chart describing a method for optimizing combustion in a wall-fired boiler according to an embodiment of the invention;

[0022] FIG. 7 is an example computing environment in which the various embodiments of the invention may be implemented; and

[0023] FIG. 8 is an example networking environment in which the various embodiments may be implemented. DETAILED DESCRIPTION

[0024] Example embodiments of the present invention will be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all embodiments are shown. Indeed, the present invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. For like numbers may refer to like elements throughout.

[0025] Turning now to the figures, FIG. 1 shows a schematic of a fuel-fired boiler system 10 having a boiler 12 with a furnace 14 and combustion chamber therein that combusts a mixture of a fuel with air to generate a flame that is used to produce steam that can be utilized in power generation applications with a steam driven generator. The boiler 12 may include T-fired boilers and wall-fired boilers. Although the description of the various embodiments of the invention is directed to T- fired boilers and wall-fired boilers, it is not meant to be limiting as aspects of the embodiments can have applicability with other types of boilers that can include, but are not limited to, suspension burners for biomass boilers, dutch oven boilers, hybrid suspension grate boilers, and fire tube boilers.

[0026] Referring back to FIG. 1 , the fuel-fired boiler system 10 can include a fuel source such as, for example, a pulverizer 16 that is configured to grind fuel such as coal to a desired degree of fineness. The pulverized coal can be passed from the pulverizer 16 to the boiler 12 using primary air. An air source 18 such as for example a fan, supplies auxiliary air or combustion air to the boiler 12 where it is mixed with the fuel and air provided by the pulverizer 16 and combusted in the furnace 14 as discussed below in more detail.

[0027] Although the fuel-fired boiler system 10 is described as a coal-based boiler system, it is understood that other boiler systems can use other types of pulverized fuel, as well as liquid or gaseous fuels. Examples of other types pulverized solid fuel that can be used with the fuel-fired boiler system 10 can include, but are not limited to, biomass, wood, peat, grains, and coke, while liquid or gaseous fuels can include, but are not limited to, oil, natural gas, producer gas, and chemical byproducts from industrial processes. Like pulverized coal-fired boiler systems, these other types of pulverized solid fuel-fired boilers as well as liquid or gaseous fuel fired boilers can have a need for combustion optimization, and thus the system and method of combustion optimization provided by the various embodiments may have utility with such non-coal based boiler systems.

[0028] As shown in FIG. 1 , the boiler 12 can have a burner zone 21 that includes a main burner zone 22 and a burnout zone 24 above the main burner zone to form the combustion chamber of the furnace 14. The main burner zone 22 receives the mixture of fuel with air from the pulverizer 16 and the auxiliary air from the air source 18. The mixture of fuel and air is ignited by burners (not shown) as it is introduced into the main burner zone 22. The ignition of mixture of fuel and air leads to combustion and flame generation.

[0029] A hopper zone 20 can be located below the main burner zone 22 for the removal of ash that results from the combustion of the fuel and air, while the burnout zone 24 above the main burner zone 22 can combust any air or fuel that is not combusted in the main burner zone 22 with the aid of overfire air introduced above the main burner zone 22 and the fuel and air added into the main burner zone via the pulverizer 16 and the air source 18. [0030] The flame resulting from the combustion of the fuel and air in the main burner zone 22 and the burnout zone 24 creates thermal energy. The thermal energy is used to heat a liquid or vapor such as water or steam in waterwall tubes (not shown) that line the walls of the furnace 14. The heating of the water in the waterwall tubes creates saturated water which can be separated into water and steam in a boiler drum (not shown) or the water may be converted to steam in the waterwall tubes. A superheater zone 26 with superheater circuits can superheat the steam for supply to a steam turbine (not shown) to generate electricity or provide heat for other purposes.

[0031] Combustion of the fuel and air within the boiler 12 produces a stream of flue gases that are ultimately treated and exhausted through a stack downstream from an economizer zone 28 which contains an economizer that can be used to preheat feedwater supplied to the boiler drum of the boiler with flue gases. As used herein, directions such as “downstream” means in the general direction relative to the flue gas flow, while the term “upstream” refers to a direction of the flue gas that is opposite the “downstream” direction relative to the flow of the flue gas.

[0032] The fuel-fired boiler system 10 of FIG. 1 can include an array of sensors, actuators and monitoring devices to monitor and control the combustion process. For example, the pulverized solid fuel-fired boiler system 10 may include a plurality of air flow control devices 30 associated with a conduit that supplies the auxiliary air from the air source 18 to the boiler 12 for introduction into the main burner zone 22 by auxiliary air nozzles (not shown) for combustion with the fuel and air introduced and ignited into the main burner zone 22 by the burners (not shown). In an embodiment, the air flow control devices 30 may be electrically or pneumatically actuated air dampers that can be adjusted to vary the amount of air that is provided to each of the auxiliary air nozzles that are associated with respective burners. Other examples of air flow control devices can include, but are not limited to, variable orifices, flow diverters, baffles, sliding gates, or turning vanes and blades as well as multiple designs of dampers. Each of the air flow control devices 30 can be individually controllable by a control unit 100 to ensure that desired air-to-fuel ratios and flame temperatures are achieved for each burner or fuel nozzle location.

[0033] The fuel-fired boiler system 10 of FIG. 1 can further include a plurality of flame scanners 46 associated with each burner and corresponding fuel nozzle that provides a stream of the fuel and air into the main burner zone 22. The flame scanners can perform a number of operations. In general, the flame scanners 46 can be used to determine if a flame is present in the main burner zone 22 and the overall quality of the flame. In addition, the flame scanners 46 can calculate a number of characteristics of the flame including but not limited to, the average intensity of the flame, the variation in the brightness of the flame, the frequency that the brightness of the flame changes, and the temperature of the flame. The flame scanners 46 may provide the characteristics for one or more different ranges of optical wavelengths. The flame scanners 46 can be electrically connected or otherwise communicatively coupled to the control unit 100 for communication of this information. Although the flame scanners 46 are described about the main burner zone 22, other configurations are possible. For example, as shown in FIG. 1 , the flame scanners 46 can be positioned in an upper portion of the furnace for monitoring and assessing further flame characteristics (e.g., temperature). In one embodiment, the flame scanners 46 can comprise two-dimensional optical flame scanners such as an in-furnace camera or optical thermography system. In general, the flame scanners 46 can include any commercially available flame scanner like the Perfecta or Exacta flame scanner systems provided by the General Electric Company or functionally equivalent flame scanner systems from other suppliers.

[0034] In addition to the flame scanners 46, the fuel-fired boiler system 10 can also include a flame stability monitor 34 located, for example, just above the burnout zone 24 that can be configured to measure or otherwise assess fireball stability within the boiler 12. The flame stability monitor 34 can also be electrically connected or otherwise communicatively coupled to the control unit 100 for communication of this information for further analysis and assessment of the combustion stability.

[0035] In one embodiment as shown in FIG. 1 , in the backpass 38 of the boiler 12, upstream from the economizer zone 28, a monitoring device 40 can be situated to monitor flue gases. In an embodiment, the monitoring device 40, which can include a plurality of flue gas sensors, can be configured for measurement and assessment of gas species that include, but are not limited to, carbon monoxide (CO), carbon dioxide (CO2), mercury (Hg), sulfur dioxide (SO2), sulfur trioxide (SO3), nitrogen dioxide (NO2), nitric oxide (NO) and oxygen (O2) within the backpass 38. SO2 and SO3 can be collectively referred to as SOx, while NO2 and NO can be collectively referred to as NOx.

[0036] In one embodiment, the monitoring device 40 can include a laserbased monitoring device such as, for example, a tunable diode laser flue-gas monitoring device. The monitoring device 40 may include one or more optical sources that may, for example, pass through a portion of a flue gas duct defined by the backpass 38. The optical sources can provide optical beams that pass through the flue gases within the backpass 38 and are detected by a corresponding plurality of optical detectors (not shown). As the beams pass through the flue gases, there is absorption of various wavelengths characteristic of the constituents within the flue gases. The optical sources can be coupled to a processor to provide for characterization of received optical signals and identification of the constituents, their concentrations and other physical properties or parameters of substances in the flue gases. In other embodiments, such analysis may be performed internally by the control unit 100.

[0037] The fuel-fired boiler system 10 of FIG. 1 can further include a plurality of flue gas sensors 42 downstream from the economizer zone 28 that are operative to obtain measurements of a plurality of properties associated with the flue gases. The measurements of the plurality of properties can provide information that is indicative of the combustion that occurred in the burner zone. In one embodiment, the plurality of flue gas sensors 42 can be configured to detect gas species that include, but are not limited to, CO, CO2, Hg, SOx, NOx and O2 within the flue gases that are downstream of the economizer zone 28. The plurality of flue gas sensors 42 can include laser-based detectors, although other types of detectors capable of detecting the amount gas species in the flue gas may also be utilized without departing from the broader aspects of the invention. These flue gas sensors may, for example, alternately extract samples of the flue gas through probes inserted into the economizer outlet duct. The extracted flue gas samples are then transported to one or more chemical analyzers located outside the flue gas duct. The plurality of flue gas sensors 42 may likewise be electrically or communicatively coupled to the control unit 100 for transmitting data relating to the measurements obtained by the sensors 42.

[0038] In one embodiment, one or more temperature sensors 43 can be deployed about the flue gas to detect the temperature of the flue gas in this section of the boiler 12. The temperature sensors 43 can also be electrically or communicatively coupled to the control unit 100 for transmitting data relating to the temperature measurements obtained by the sensors 43.

[0039] It is understood that the plurality of flue gas sensors 42 and the temperature sensors 43 can be disposed in other locations about the boiler 12 in addition to or in place of those located downstream of the economizer zone 28. For example, it may be desirable to have flue gas sensors 42 and temperature sensors 43 located about the superheater zone 26 or a reheater zone if a reheater is deployed with the boiler. To this extent, in one embodiment, the information provided by the flue gas sensors 42 and the temperature sensors 43 at this section can be used to obtain an understanding of the combustion in the boiler based on the heat exchange that occurs at the superheater zone 26 and reheater zone.

[0040] FIG. 1 further shows that the fuel-fired boiler system 10 can include an oxygen sensor 44 arranged within the outlet to the stack that is configured to monitor the concentration of oxygen within the flue gas. In one embodiment, the sensor 44 may be a paramagnetic sensor. The sensor 44 may also be communicatively coupled to the control unit 100 for relaying the detected oxygen concentration to the control unit 100.

[0041] While the array of sensors and monitoring devices discussed above may be utilized to detect, for example, CO, NOx and other emissions, O2 distribution, flame information, temperatures and the like, various other sensors and monitoring devices may also be utilized within the fuel-fired boiler system 10. Other examples of sensors that can be deployed include but are not limited to pressure sensors to measure pressure drop between various locations within the boiler 12 or high frequency pressure pulsations caused by uneven combustion, and temperature sensors located at other locations within the boiler to measure temperature. In one embodiment, the stack may be configured with an opacity monitor to assess the degree to which visibility of a background (i.e. , blue sky) is reduced by particulates for use in determining the amount or concentration of particulates within the flue gases exiting the stack. In one embodiment, wall condition sensors can be deployed about the waterwall of the boiler to assess heat flux and furnace wall conditions such as corrosion and/or deposit buildup.

[0042] It is understood that the components of the boiler 12 depicted in FIG. 1 do not represent all of the elements that can be part of a boiler. Those skilled in the art will appreciate that a boiler can have other components depending on the type and purpose such as for example sub-critical steam generation or super-critical steam generation. For sake of clarity and for a general understanding of the various embodiments, the components depicted in FIG. 1 are for purposes of providing a basic understanding of a steam boiler. The components and operation are not meant to limit the various embodiments as it is understood that the components and operation of the boiler can vary.

[0043] As noted above, the fuel and air provided by the pulverizer 16 mix with the auxiliary air provided by the air source 18 and the overfire air added above the fuel and air and combust in the burner zone of the furnace 14 which leads to flame generation. FIG. 2 shows a schematic representation of this portion of the boiler 12 depicted in FIG. 1 with further details of the combustion of fuel and air in the furnace according to an embodiment of the invention.

[0044] In the schematic of FIG. 2, one or more windboxes 48, which may be positioned on one or more walls of the furnace 14 such as at the corners in the case of a T-fired boiler or on a single or opposing walls in the case of a wall-fired boiler. In the embodiment depicted in FIG. 2, the windboxes 48 are positioned in the corners of the boiler 12 and thus can correspond to a T-fired boiler. Each windbox 48 can have a plurality of air compartments 50 through which auxiliary air supplied from the air source 18 is injected into the burner zone 21 (i.e., the main burner zone). Also disposed in each windbox 48 is a plurality of fuel compartments 52, through which fuel and air provided from the one or more pulverizers 16 is injected into the main burner zone via a plurality of fuel ducts 54. The one or more pulverizers 16 can be operatively connected to an air source (e.g., a fan), such that the air stream generated by the air source transports the fuel from the pulverizers 16 through the fuel ducts 54, through the fuel compartments 52, and into the main burner zone of the burner zone 21 in a manner which is well known to those skilled in the art.

[0045] In this arrangement, the plurality of fuel compartments 52 and the plurality of air compartments 50 define an elevated arrangement of fuel and air introduction locations along the walls of the furnace 14 for introducing a mix of the fuel and air into the main burner zone to generate a flame therein. In this arrangement, each of the plurality of fuel compartments 52 can include a burner having a fuel nozzle operative to provide a stream of the fuel and air into the main burner zone, while the plurality of air compartments 50 can each include one or more auxiliary air nozzle(s) that is operative to supply a stream of auxiliary air into the burner zone for contribution in the combustion with the fuel and air provided by the fuel nozzles.

[0046] The burners and the corresponding fuel nozzles, as well as the auxiliary air nozzles can include any common assembly for these components that is well known to those skilled in the art. Further, it is understood that burners for liquid or gas fuels such as natural gas are more likely to have separate nozzles for air and fuel, compared to burners designed for pulverized solid fuel where the air is used to transport the pulverized fuel. As used herein, a fuel nozzle that provides a stream of the fuel and air into the burner zone embraces both a fuel nozzle operative to provide a stream of the fuel and air into the burner zone such as with a pulverized solid fuel where the air is used to transport the pulverized fuel, and closely coupled fuel and air nozzles performing a similar function like that associated with burners configured for liquid or gas fuels.

[0047] With the elevated arrangement of fuel and air introduction locations at the comers as depicted in FIG. 2, each elevation will correspond to a firing elevation level with one or more burners, with each level separated by an air compartment 50. In this manner, the burners and air compartments can generate a swirling and rotating fireball that meet just off-center of the furnace combustion chamber 14, filling most of its cross section. It is understood that the schematic representation depicted in FIG. 2 is representative of one configuration for a T-fired boiler and is not meant to be limiting. For example, there can be more firing elevation levels than that what is depicted in FIG. 2, or the boiler furnace can be wider with 8 burners per elevation arranged to create two swirling fireballs from each group of 4 burners. Further, those skilled in the art will appreciate that a T-fired boiler can include for example 4, 5, 6, 7, or 8 levels. To this extent, a T-fired boiler can have a number of burners disposed at the four or eight comers of the furnace that range for example from 16 to 64.

Furthermore, it is understood that in this configuration for a T-fired boiler, there can be one or more pulverizers 16 for supplying the fuel and air to the burners. For example, it is possible to have a separate pulverizer to feed the burners at each firing elevation level for each of the four or eight comers of the furnace.

[0048] Referring back to FIG. 2, in order to aid the combustion of any air or fuel that is not combusted in the main burner zone, one or more discrete levels of Separated OverFire Air (SOFA) can be incorporated in each corner of the boiler 12 so as to be located between the top of each windbox 48 and a boiler outlet plane 56 of the boiler, for example providing a low level of separated overfire air 58 and a high level of separated overfire air 60.

[0049] FIG. 3 is a schematic representation of a system 62 for optimizing combustion in a boiler like that depicted in FIGS. 1 and 2. As shown in FIG. 3, the system 62 includes a plurality of fuel flow sensors 64 to obtain measurements of the flow of the fuel and air provided to the plurality of burners in the plurality of fuel compartments (described above with respect to FIG. 2). In one embodiment, each of the fuel flow sensors 64 is operative to obtain real-time measurements of the flow of the fuel and air that is supplied to the burners. The fuel flow sensors 64 can take the form of any of the commercially available fuel flow sensors that are known in the art. Non-limiting examples of fuel flow sensors include those provided by doppler radar, triboelectric, or ultrasonic measurement technologies. Further, it is well known to those versed in the art that some fuel flow manufacturers may recommend that more than one sensor be installed in each pipe to achieve the most accurate measurement results. Further references to the fuel flow sensors 64 in each pipe herein may refer to a plurality of sensors in each pipe interchangeably with a single fuel flow sensor per pipe.

[0050] One or more auxiliary air flow sensors 66 can obtain measurements of the flow of the auxiliary air (combustion air) supplied into the burner zone by one or more of the plurality of auxiliary air nozzles in the plurality of air compartments (FIG.

2) that can be located about (i.e. , above, below or around) the plurality of burners. In one embodiment, each of the auxiliary air flow sensors 66 is operative to obtain real- time measurements of the flow of the auxiliary air that is supplied into the burner zone by one or more of the plurality of auxiliary air nozzles. The auxiliary air flow sensors 66 can take the form of any of the commercially available air flow sensors that are known in the art. Non-limiting examples of auxiliary air flow sensors include those using technologies such as hot wire, moving vane(s), vortex, coriolis, or differential pressure across an orifice plate.

[0051] Where individual air flow sensors for each air nozzle are not practical, the air flow can be calculated from the air flow in a larger duct or windbox 48 (FIG. 2) and the positions of individual dampers or air flow control devices 30 leading to each air compartment 50 and nozzle (FIG. 2). The effective free flow area through each damper has a non-linear relationship with the damper position. The non-linear relationship varies with the mechanical design of the air compartments 50 and their nozzles and with the mechanical design of the air damper vanes in the case that the air flow control devices 30 are air dampers. Published scientific literature provides multiple examples of these non-linear relationships which can be used to determine the effective free flow cross-sectional area of each air compartment 50 and nozzle with its air flow control device 30 in a known position. Alternatively, scaled physical flow models or Computational Fluid Dynamics models can be used to determine the non-linear relationship for a particular air compartment 50 and nozzle and air control damper design. The air flow through each air compartment 50 and nozzle is approximately proportional to the total air flow through the windbox 48 times the effective free flow area of a particular air compartment 50 and nozzle divided by the total effective free flow area of all air compartments 50 and their nozzles fed by the windbox 48.

[0052] FIG. 3 also shows that the system 62 can further include a plurality of flame scanners 46 to obtain flame scan data of the flame in the burner zone 21 (FIG. 2) of the boiler 12. The scan data of the flame obtained by the flame scanners 46 can include any of the aforementioned information discussed previously with respect to the flame scanners.

[0053] A plurality of flue gas sensors 42 can obtain measurements of a plurality of properties associated with the flue gases. The measurements of the plurality of properties obtained by the flue gas sensors 42 can provide information that is indicative of the combustion that occurred in the burner zone. For example, the flue gas sensors 42 can be configured to detect, measure and assess gas species that include, but are not limited to, CO, CO2, Hg, SOx, NOx and O2 within the flue gases that are downstream of the economizer zone 28 (FIG. 2). The flue gas sensors can take the form of any of the aforementioned gas sensors.

[0054] The system 62 can collect other information about the boiler in addition to the measurements obtained by the fuel flow sensors 64, the auxiliary air flow sensors 66, the flame scanners 46 and the flue gas sensors 42. For example, because the actual air flow near each burner may be affected by air flow control devices 30, information associated with these devices can be collected as utilized as part of the combustion optimization described herein. As shown in FIG. 3, the plurality of air flow control devices 30 can control the supply of the streams of auxiliary air into the burner zone by the plurality of auxiliary air nozzles (not shown). In one embodiment, the plurality of air flow control devices 30 can include electrically or pneumatically actuated air dampers, however, any of the aforementioned air flow control devices can be deployed in alternative embodiments.

[0055] In operation, each of the air flow control devices 30 can be coupled to one of the plurality of auxiliary air nozzles, such that each air flow control device is operative to control a flow of the auxiliary air through a correspondingly coupled auxiliary air nozzle into the burner zone. The information of the position of each of the air flow control devices 30, as well as their operational status can be collected as these items can have relevance to the actual air flow near the burners. In one embodiment, this information associated with the air flow control devices 30 can be collected by the plant control unit 100 which can provide the overall control to the boiler 12.

[0056] In one embodiment, as shown in FIG. 3, one or more pressure sensors 70 can obtain pressure measurements about the furnace of the boiler 12. For example, the pressure sensors 70 can measure high-frequency pulsations caused by variations in combustion or pressure drop between various locations within the boiler 12.

[0057] As shown in FIG. 3, a controller 72 can receive the information provided by the fuel flow sensors 64, the auxiliary air flow sensors 66 if present, the flame scanners 46, the flue gas sensors 42, the air flow control devices 30, and the pressure sensors 70. In one embodiment, the controller 72 is operative to optimize the combustion of the fuel and air in the burner zone as a function of information provided by the fuel flow sensors 64, the auxiliary air flow sensors 66 or calculated air flows as described above, the flame scanners 46, the flue gas sensors 42 and the air flow control devices 30. Details of the optimization that are performed by the controller 72 are described with reference to FIGS. 4-6, however in general, the controller determines air-to-fuel ratios near each of the burners based on the collected data from the fuel flow sensors 64, the auxiliary air flow sensors 66 or calculated air flows, the flame scanners 46, the flue gas sensors 42 and the air flow control devices 30. The controller 72 then determines operational biases that redistribute air near one or more burners to be more consistent with the air-to-fuel ratios with other burners while maintaining approximately the same amount of air at each elevation of a vertical furnace if the boiler is a T-fired boiler or vertical wall fired boiler, or each longitudinal distance from the burners of a furnace if the boiler is a horizontal wall-fired boiler. The operational biases determined by the controller 72 can then be conveyed to the plant control unit 100 via a communications network 74. The control unit 100 can apply the operational biases to one or more of the burners at a controlled rate via the air flow control devices 30. The controller 72 evaluates the combustion operation of the boiler after applying the operational biases to the one or more of the burners to determine if the applied operational biases resulted in better combustion operation results than combustion operation results obtained prior to applying the operational biases.

[0058] If the operational biases applied to the one or more of the burners did not yield better combustion operation results, then the controller 72 can roll back the operational biases applied to the one or more of the burners, collect more data, and repeat the same operations (e.g., determine the amount of air near each of the burners, determine the air-to-fuel ratios of each of the burners, determine another set of operational biases, apply those biases to another one or more of the burners, and evaluate the combustion operation results). These operations can continue until there is a balancing of the air-to-fuel ratios between each of the burners or until no further combustion improvement is observed, resuming again when operational changes such as for example, a change in energy generated or the selection of burners in service occurs.

[0059] It is understood that the communications between the controller 72, the plant control unit 100 and a remote control unit 76 (which can perform any of a number of activities including but not limited to, performing remote monitoring and diagnostics of the controller and the plant control unit, reviewing boiler operation and the effects of the optimization biases applied, or updating limits and tuning parameters in the application logic, via the communications network 74) can include any of the well-known communication networks and data communication protocols used to communicate information between such networks. For example, wide area networks (WAN) and local area networks (LAN) can be used with the communications network 74 to enable communications between the controller 72, the plant control unit 100 and the remote control unit 76, while using a data communication protocol such as Modbus TCP/IP or other communication protocols such as Remote Desktop Protocol (RDP) to facilitate the communication of information between each of these components.

[0060] Further, the implementation depicted in FIG. 3 represents only one approach to deploying the system 62, and is not meant to be limiting as those skilled in the art will appreciate that the system 62 can take the form of other configurations. For example, the controller 72 may be localized on one computer and/or distributed between two or more computers. Also, the controller 72 and plant control unit 100 may be distributed to one or more control units in different arrangements and still operate in accordance with the various embodiments of the invention. For example, instead of having the controller 72 and the plant control unit 100 configured as separate components, it is understood that these components can be merged into a single unit or split into 3 or more units. In one embodiment, the controller 72 can be integrated in the plant control unit 100, such that the data from the various sensors and devices is provided to the plant control unit, and optimization aspects of the various embodiments can be performed by a combustion optimization component within the plant control unit. Further, it is understood that the system 62 depicted in FIG. 3 is applicable to operate with the boilers depicted in FIGS. 1 and 2. Moreover, as noted above, the boilers depicted in FIGS. 1 and 2 are representative of only one boiler arrangement and is not meant to be limiting to the various embodiments, as those skilled in the art will appreciate that the system 62 and its operation has applicability with other boiler configurations.

[0061] FIG. 4 is a block diagram showing more of the details of the controller 72 depicted in FIG. 3 that includes a combustion optimization component for performing combustion optimization of a boiler according to an embodiment of the invention. Aspects of the controller 72 including methods, processes, and operations performed thereby can constitute machineexecutable components embodied within machine(s), e.g., embodied in one or more computer-readable mediums (or media) associated with one or more machines. Such components, when executed by one or more machines, e.g., computer(s), computing device(s), automation device(s), virtual machine(s), etc., can cause the machine(s) to perform the operations described.

[0062] Further, the description that follows for the controller 72 in FIG. 4, as well as the description associated with other figures may use the terms “object,” “module,” “interface,” “component,” “system,” “platform,” “engine,” “selector,” “manager,” “unit,” “store,” “network,” “generator” and the like to refer to a computer- related entity or an entity related to, or that is part of, an operational machine or apparatus with a specific functionality. These entities can be either hardware, a combination of hardware and firmware, firmware, a combination of hardware and software, software, or software in execution. In addition, entities identified through the above terms are herein generically referred to as “functional elements.” As an example, a component can be, but is not limited to being, a process running on a processor, a processor, an object, an executable, a thread of execution, a program, and/or a computer. By way of illustration, both an application running on a server and the server can be a component. One or more components may reside within a process and/or thread of execution, and a component may be localized on one computer and/or distributed between two or more computers. Also, these components can execute from various computer-readable storage media having various data structures stored thereon. The components may communicate via local and/or remote processes such as in accordance with a signal having one or more data packets (e.g., data from one component interacting with another component in a local system, distributed system, and/or across a network such as the Internet with other systems via the signal). As an example, a component can be an apparatus with specific functionality provided by mechanical parts operated by electric or electronic circuitry, which is operated by software, or firmware application executed by a processor, wherein the processor can be internal or external to the apparatus and executes at least a part of the software or firmware application. As another example, a component can be an apparatus that provides specific functionality through electronic components without mechanical parts. The electronic components can include a processor therein to execute software or firmware that confers at least in part the functionality of the electronic components. Interface(s) can include input/output (I/O) components as well as associated processor(s), application(s), or API (Application Program Interface) component(s). While examples presented hereinabove are directed to a component, the exemplified features or aspects also apply to object, module, interface, system, platform, engine, selector, manager, unit, store, network, and the like. [0063] Referring again to FIG. 4, the controller 72 can include a data acquisition and preprocessing component 78, a combustion optimization component 80 (which can also be referred to as the “optimizer”), an interface component 82, one or more processors 84, and memory 86 that may include Static or Dynamic Random Access Memory (RAM), Flash memory, rotating magnetic disk memory, Solid State Disks (SSDs), or optical storage such as Compact Disc (CD) or Digital Versatile Disk (DVD). Memory 86 stores data 88 that can include, but is not limited to, time history of sensor data, time history of processed sensor data, time history of calculated burner stoichiometry data, time history of calculated biases, time history of data communicated between controller 72 and control unit 100, program executable code for controller 72, alerts or messages generated by the executable program(s), and configuration data used by the executable program(s) performing the above-described actions and those with reference to FIG. 5 and FIG. 6.

[0064] In various embodiments, one or more of the data acquisition and preprocessing component 78, the combustion optimization component 80, the interface component 82, the one or more processors 84, and t h e memory 86 can be electrically and/or communicatively coupled to one another to perform one or more of the functions of the controller 72. In some embodiments, one or more of the data acquisition and preprocessing component 78, the combustion optimization component 80, and the interface component 82 can comprise software instructions stored on the memory 86 and executed by processor(s) 84. In addition, the controller 72 may interact with other hardware and/or software components not depicted in FIG. 4. For example, processor(s) 84 may interact with one or more external user interface devices, such as a keyboard, a mouse, a display monitor, a touchscreen, a printer, a network communication controller, removable storage devices such as a flash drive, or other such interface devices. [0065] The data acquisition and preprocessing component 78 can be configured to acquire the measurements obtained by the fuel flow sensors 64, the auxiliary air flow sensors 66, the flame scanners 46, and the flue gas sensors 42, the pressure sensors 70, as well as the position and status information from the air flow control devices 30. In one embodiment, the data acquisition and preprocessing component 78 can include a plurality of analog to digital converters (A/D), with each A/D converter operatively coupled to one of the fuel flow sensors 64, the auxiliary air flow sensors 66, the flame scanners 46, the flue gas sensors 42, and the air flow control devices 30.

[0066] In another embodiment, some or all of the sensors listed in the previous sentence may communicate with the data acquisition and preprocessing component 78 via one or more digital communication interfaces including, but not limited, to communication networks and protocols such as Modbus/TCP or Modbus RTU, wireless communication systems, including but not limited, to WiFi, Bluetooth, or Zigbee, or analog electrical signals such as 4-20ma current loops or 0V-to-10V electrical signals. In another embodiment, some or all of the sensors listed in this paragraph may communicate electrical signals to one or more separate Input/Output devices which can then communicate with data acquisition and preprocessing component 78 via a digital communication interface including, but not limited to, Modbus/TCP or Modbus RTU. In another embodiment, some or all of the sensors may communicate with the plant control unit 100 which then can communicate the measurements via a digital communication interface including, but not limited, to Modbus/TCP, Modbus RTU, or OLE for Process Control (OPC). In this manner, the A/D converters can convert physical condition signals that are provided to the controller 72 by the fuel flow sensors 64, the auxiliary air flow sensors 66, the flame scanners 46, the flue gas sensors 42, and the air flow control devices 30 into digital form for further storage and analysis.

[0067] The data acquisition and preprocessing component 78 can further include a data preprocessor that is configured to eliminate the noise embedded in the signals obtained from the fuel flow sensors 64, the auxiliary air flow sensors 66, the flame scanners 46, the flue gas sensors 42, and the air flow control devices 30, and extract key-feature related information from these elements. In general, the data preprocessing can include segmentation of the data received from the fuel flow sensors 64, the auxiliary air flow sensors 66, the flame scanners 46, the flue gas sensors 42, and the air flow control devices 30, cleaning of the data, and extracting key-feature related information. In one embodiment, the data preprocessing can include time averaging of the data obtained from the fuel flow sensors 64, the auxiliary air flow sensors 66, the flame scanners 46, the flue gas sensors 42 and the air flow control devices 30. In this manner, the time-averaged pre-processed data can give representative data values that are indicative of the combustion conditions in the boiler while accounting for unsteady operation and noisy measurements in the boiler.

[0068] In one embodiment, the data preprocessing can include performing other mathematical processing or statistical operations on the data in order to obtain an indication of the combustion conditions. These mathematical processing and statistical operations can include, but are not limited to, averaging, range checking of sensor values to exclude unrealistic values based on the boiler process conditions, using sensor status or measurement quality information to exclude sensor measurement values which are known to be bad or inaccurate, excluding sensor values which vary too much from the previous measurement in time and are therefore known to be in error, excluding one or more of a group of similar measurement values which vary too much from the median or average of the sensor values, or other forms of data preprocessing.

[0069] To this extent, a representation of the combustion conditions can be obtained by performing any of these mathematical processing operations. For example, a doppler radar based fuel flow sensor may be influenced by an increase in turbulent air flow and report a fuel flow value much higher than the expected fraction of the pulverizer fuel flow, for example significantly above one fourth or one eight of the total pulverizer fuel flow in a T-fired boiler. In another example, the measurement quality reported by a fuel flow sensor may be bad if the sensor was unable to complete a measurement successfully. Any measurement values from that sensor when the corresponding measurement quality was bad should be excluded from the data set used for combustion optimization. In another example, the measurement data may be discarded if the controller loses communication with a sensor or I/O device.

[0070] With the data acquired and preprocessed by the data acquisition and preprocessing component 78, the combustion optimization component 80 can use this information to optimize the combustion of the fuel and air in the burner zone as a function of information provided by the fuel flow sensors 64, the auxiliary air flow sensors 66 or equivalent calculated air flows, the flame scanners 46, the flue gas sensors 42, and the air flow control devices 30, and the pressure sensors 70. In one embodiment, the combustion optimization component 80 can include a guided search optimization algorithm that mixes measured and/or calculated stoichiometry of the burners in the boiler with a search algorithm customized to find operational biases that can be applied to one or more of the burners to yield better combustion operation results for the boiler, while accounting for measurement inaccuracies and unexpected interactions between burners as the operational biases are determined and evaluated.

[0071] In general, the guided search optimization algorithm of the combustion optimization component 80 optimizes the combustion of the fuel and air in the burner zone of the boiler by performing and facilitating certain operations. These operations can include determining air-to-fuel ratios near each of the burners based on the acquired and preprocessed data provided by the data acquisition and preprocessing component 78. Operational biases are then determined that redistribute air near one or more burners to be more consistent with the air-to-fuel ratios with other burners while maintaining approximately the same amount of air at each elevation of a vertical furnace if the boiler is a vertical T-fired or a vertical wall fired boiler or each longitudinal distance from the burners of a horizontal furnace if the boiler is a horizontal wall-fired boiler.

[0072] The determined operational biases can then be conveyed to the plant control unit 100 via the interface component 82. The plant control unit 100 can then use air control logic that is well known in the art to apply the operational biases to one or more of the burners. The data acquisition and preprocessing component 78 can then collect data from the boiler after running it with the applied biases for a predetermined amount of time. The guided search optimization algorithm of the combustion optimization component 80 can then evaluate the data to determine if the applied operational biases resulted in better combustion operation results than combustion operation results obtained prior to applying the operational biases. [0073] If the operational biases applied to the one or more of the burners yields better combustion operation results, then the guided search optimization algorithm can determine additional operational biases for one or more additional burners. Alternatively, if the operational biases applied to the one or more of the burners did not yield better combustion operation results, then the guided search optimization algorithm can roll back the operational biases applied to the one or more of the burners, collect more data, and repeat the same operations (e.g., determine the amount of air near each of the burners, determine the air-to-fuel ratios near each of the burners, determine another set of operational biases, apply those biases to another one or more of the burners, and evaluate the combustion operation results). These operations performed by the guided search optimization algorithm can continue until there is a balancing of the air-to-fuel ratios between each of the burners or until no further combustion improvement is observed, resuming again when the boiler operation changes, for example with a change in boiler fuel or air flow or a change in the selection of burners in service. Further details of the optimization that is performed by the guided search optimization algorithm of the combustion optimization component 80 for a T-fired boiler and a wall-fired boiler are described with reference to FIGS. 5 and 6, respectively.

[0074] As noted above, the interface component 82 can convey the determined operational biases to the plant control unit 100 via the communications network component 74 (FIG. 3), however the interface component can be used to perform other functions. These functions include, but are not limited to, storing data such as time series sensor and calculation data or application program messages and alerts to memory 86 as part of the stored data 88. Interface component 82 may also communicate with other plant control, data communication and display, or data storage systems such as a plant data historian.

[0075] The one or more processors 84 can perform one or more of the functions described herein with reference to the operations associated with the data acquisition and preprocessing component 78, the combustion optimization component 80, and the interface component 82. The memory 86 can be a computer-readable storage medium that can store computer-executable instructions and/or information for performing the functions described herein with reference to the systems and/or methods disclosed that are associated with the data acquisition and preprocessing component 78, the combustion optimization component 80, and the interface component 82.

[0076] FIG. 5 is a flow chart 102 describing a method for optimizing combustion in a T-fired boiler according to an embodiment of the invention. In general, a T-fired boiler utilizes burners located on one or more walls of the boiler such as in particular, at the corners of the walls. The burners at the corners of the boiler can define an elevated-arrangement of fuel and air introduction locations for introducing a mix of a fuel and air into the furnace of the boiler, and in particular to, a burner of the furnace to generate a flame. The elevated arrangement of fuel and air introduction locations at the corners typically include multiple firing elevation levels with each firing elevation level having one or more burners with 4 or 8 burners per elevation most common. Each of the burners include a fuel nozzle operative to provide a stream of the fuel and air into the burner zone at a specified firing elevation level within the elevated arrangement. In this manner, the burners can generate a swirling and rotating fireball that meet just off-center of the furnace, filling most of its cross section. The number of firing elevation levels that can be lined vertically up the corners of the walls can include, for example 4, 5, 6, 7, or 8 levels. To this extent, a T-fired boiler can have a number of burners disposed at the corners of the furnace that range from 16 to 64, assuming 4 or 8 corners and 4 to 8 levels. Other combinations of elevations and comers are also possible and are not excluded from optimization using the various embodiments of this invention.

[0077] The method for optimizing combustion in a T-fired boiler as described in the flow chart 102 of FIG. 5 can begin by collecting sensor data at 104. In one embodiment, the data acquisition and preprocessing component 78 of the controller 72 can collect measurements obtained by the fuel flow sensors 64, the auxiliary air flow sensors 66, the flame scanners 46, and the flue gas sensors 42, as well as the position and status information from the air flow control devices 30. This data that is collected can include the individual fuel flows to each burner, any of the aforementioned flame data that is generated by the flame scanners 46, O2, CO, and NOx amounts in the flue gas (e.g., downstream of the economizer outlet), positions of the air flow control devices 30, flows of the auxiliary air to the auxiliary nozzles. It is understood that the data acquisition and preprocessing component 78 can collect other types of data and thus embodiments of the invention are not meant to be limited to any particular data, and data that is only obtained by the aforementioned sensors. For example, the data acquisition and preprocessing component 78 can collect the temperature of the primary air flows that is associated with the fuel supplied to the fuel nozzles, as well as the temperature of the auxiliary air flows in the windboxes that are provided to the burner zone. Other data can include, but is not limited to, pressure measurements, fuel pulverizer motor amps or electrical power consumed, steam temperatures from the superheater or reheater heat exchanger tubes or headers, or air and fuel velocity measurements. [0078] The collecting of this data can occur for a predetermined amount of time that is sufficient to obtain an average amount of data that accounts for the fluctuations that arise in the boiler process due to factors that can include, but are not limited to, variation in the delivery of the fuel to the burners, variation in the ability of the sensors to measure data, and sensor signal or measurement noise from multiple causes. In one embodiment, the data acquisition and preprocessing component 78 can collect data from the fuel flow sensors 64, the auxiliary air flow sensors 66, the flame scanners 46, the flue gas sensors 42, and the air flow control devices 30 for ten minutes. Those skilled in the art will appreciate that other time periods can be utilized to obtain a good average of representative data and thus the ten minute period is not meant to be limiting.

[0079] The flow chart 102 continues at 106 where the collected data is preprocessed to eliminate the noise embedded in the signals obtained from the fuel flow sensors 64, the auxiliary air flow sensors 66, the flame scanners 46, the flue gas sensors 42, and the air flow control devices 30, and extract key-feature related information from these signals. In one embodiment, the data preprocessing can include time averaging the data obtained from the fuel flow sensors 64, the auxiliary air flow sensors 66, the flame scanners 46, the flue gas sensors 42 and the air flow control devices 30. To this extent, the time-averaged data can provide values of data that is representative of the combustion conditions in the boiler while accounting for unsteady operation and noisy measurements in the boiler.

[0080] In one embodiment, the data preprocessing can include performing other mathematical processing or statistical operations on the data in order to obtain an indication of the combustion conditions. As mentioned above, these mathematical processing and statistical operations can include, but are not limited to, using sensor measurement quality or status values to identify and disqualify known bad or suspected bad measurement data, and some or all of other techniques mentioned above may also be employed in pre-processing the measurement data to provide the most accurate assessment of the current boiler combustion. To this extent, a representation of the combustion conditions can be obtained by performing any of these mathematical processing operations.

[0081] If there are any major operational changes in the boiler as noted in 108, then the operations of the flow chart 102 can collect more sensor data at 104 and preprocess that data at 106. As used herein, major operational changes in the boiler can include, but are not limited to, significant changes in boiler fuel flow rate or energy output, firing elevations starting or stopping operation, change in fuel properties, or communication errors with critical sensors.

[0082] If no major operational changes occurred as ascertained at 108, then the operations of the flow chart continue at 110 where the air near each of the burners from the primary and secondary air flows is determined. In general, the air near each of the burners from the primary air flows that carries the fuel to the boiler can be determined as a function of primary air flow through a fuel pulverizer, mill air flow tests, effective nozzle free flow areas based on nozzle I damper geometry and non-linear damper opening I air flow relationships. As used herein, “near each of the burners” means air which is injected into the furnace with the fuel or from nearby air inlet nozzles where the air is expected to react with fuel from that burner nozzle.

[0083] In one embodiment, the air near each of the burners from the primary air flows is determined by dividing the primary air flowing through the fuel pulverizer by the number of burners fed by that pulverizer. For example each elevation typically has 4 or 8 burners in a tangentially fired furnace. If pulverizer air flow test data is available, then it is used to determine the different percentages of the air flowing through the pulverizer that flows through each burner nozzle instead of simply dividing the total flow by the number of burners. If individual air nozzle flows are not separately measured, then they may be calculated as described above. The measured or calculated air flow from auxiliary air nozzles directly above the burner in a tangentially fired furnace and fuel air nozzles supplying air directly around the primary fuel/air stream are added to the primary air flow transporting the fuel through the burner to determine the air flow near each burner. If additional air inlets are present near the burner, for example Fuel Air, Close-Coupled Overfire Air (CCOFA), Concentric Firing System (CFS) air nozzles, or crotch air nozzles then the calculated or measured air flow from these nozzles may be included in the total air near the burner. This adding of all the various levels of air are reflected in FIG. 5 at operation 112.

[0084] With this estimation of the total air that is near each of the nozzles, the operations of the flow chart 102 continue at 114 where the air-to-fuel ratios (i.e. , stoichiometry) near each of the burners can be determined. In particular, the preprocessed average of the air flows through or near each burner as described above are divided by the preprocessed average fuel flow through that burner to determine the current air-to-fuel ratio over the time period. In one embodiment, the time period for sampling data can be 10 minutes.

[0085] Operational biases that redistribute air through or near one or more of the burners at an elevation level to be more consistent with the air-to-fuel ratios with other burners around that elevation level while maintaining approximately the same amount of air at each elevation level are determined at 116 while respecting various limits such as minimum and maximum permitted biases, for example -10% to +10% of the damper operating range, or a minimum opening value for each fuel air damper to ensure that sufficient cooling air is provided to the burner nozzle tip. As used herein, “more consistent” means that the optimizer may bias air flows part of the amount required to achieve perfectly balanced air-to-fuel ratios on the burners being optimized, and “maintaining approximately the same amount of air at each elevation level” means bias limits applied to some but not all air nozzles at an elevation may result in the total amount of air flowing through burners or nozzles at that elevation being slightly increased or decreased because equal mass flows of air flow were not added and removed near the burners at that elevation.

[0086] In one embodiment, the operational bias are determined by calculating the mass flow of air needed to achieve perfectly balanced air-to-fuel ratios at each burner at the elevation being optimized while maintaining the same total air flow at that elevation, calculating a new desired air flow which may include some fraction of the change in mass flow of air needed to achieve perfectly balanced air-to-fuel ratios, calculating the change in damper position needed to achieve the desired air flow, then limiting the damper bias if the allowed bias limit is smaller than the damper adjustment required to achieve the desired air flows. Bias limits are then applied, for example, if the requested change in damper position exceeds the bias limit for that damper, or if the resulting position of a fuel air damper would not supply sufficient cooling air to the burner nozzle tip. If bias limits are applied to some but not all burners at an elevation, then the total amount of air flowing through burners or nozzles at that elevation may be slightly increased or decreased because equal amounts of air flow were not added and removed from the burners. Optionally, the optimizer may be configured to intentionally increase the total air flow at an elevation if some dampers are relatively closed and cannot be further closed sufficiently to achieve the desired mass air flow, or conversely, the total air flow at an elevation may be decreased if some dampers are relatively open and cannot be further opened sufficiently to achieve the desired mass air flow.

[0087] Depending on the success or failure of previous optimization biases at that elevation, the desired air flow as a fraction of the air flow needed to achieve perfect air-to-fuel ratio balance among the burners at that elevation may be changed on subsequent optimization steps. That is, optimization of that elevation may be skipped after repeated optimization failures, or the desired air flow fraction may be calculated so that the desired air-to-fuel ratios are apparently more different after the biases are applied. Temporarily skipping optimization biases for an elevation or biasing in apparently the “wrong direction” may improve combustion in cases of significant measurement errors, or unexpected interactions between air and fuel injected near different burners for example caused by broken burner and air nozzle tilt mechanisms in a T-fired boiler. As used herein, the “biasing in the wrong direction” means biasing air flows to increase instead of decrease the range of air-to- fuel ratios of the burners being optimized based on the various air and fuel flow measured or calculated values. This can help the optimizer achieve better overall combustion even when faced with inaccurate measurements or unexpected interactions between air and fuel inlets in the furnace that would not be correctly predicted by most boiler models.

[0088] The determined operational biases can then be applied at 118 to or near one or more of the burners at the elevation level at a controlled rate to avoid significant boiler transients. As used herein, “significant boiler transients” mean disruptions in air or fuel flows, steam temperature changes that potentially exceed operating temperature or rate-of-change limits, or control system oscillation caused by poorly tuned control loops. In one embodiment, the determined operational biases are conveyed to the plant control unit 100 via the interface component 82. The plant control unit 100 can then use air control logic to apply the operational biases to one or more of the burners at the elevation level at a controlled rate via the air flow control devices 30 (FIG. 3).

[0089] The data acquisition and preprocessing component 78 can then collect and preprocess data from the boiler at 119 after running it with the applied biases for predetermined amount of time. The combustion operation of the boiler is then evaluated at 120 to determine whether the applied operational biases lead to better combustion operation results than combustion operation results obtained prior to applying the operational biases. As used herein, “better combustion operation results” means an overall improvement considering factors including, but not limited to, pollutant emissions, evenness of the resulting O2 across the furnace or economizer outlet resulting from high or low local stoichiometry near different burners, evenness of flue gas temperatures across the furnace or economizer outlet or of the resulting steam temperature variations in heat exchanger tubes, and flame stability as determined from the flame scanners, furnace pressure pulsation, or other flame stability indications. Depending on the operational and emissions limits for a boiler, these factors may be considered with a higher or lower weighting factors when determining if combustion has improved overall.

[0090] In one embodiment, the evaluating of the combustion operation of the boiler comprises assessing one or more combustion operation parameters. These combustion operation parameters can include, but are not limited to, CO, NOx, O2, flame stability as determined from the flame scanners or other sensors, and temperature distribution of the flue gases or of steam temperatures leaving heat exchanger tubes that may vary due to variations in the flue gas temperatures. This assessing of the one or more combustion operation parameters can include applying a weighting factor to each of the combustion operation parameters. To this extent, each weighting factor can be assigned a lighter or heavier degree of importance with respect to the evaluating of the combustion operation of the boiler. For example, the weighting factor applied to increased NOx emissions may be increased if the boiler typically operates close to or sometimes over its permitted level of NOx emissions, or the expense of ammonia required to reduce NOx emissions through Selective Catalytic Reduction (SCR) or Selective No-Catalytic Reduction (SNCR) emissions control systems causes a financial burden to the boiler operator. In another example, boilers which more frequently experience burner trips due to unstable combustion may have a higher weighting factor applied to the minimum and/or average flame stability and lower weighting factors applied to other evaluated criteria.

[0091] If the operational biases applied to the one or more of the burners yields better combustion operation results as determined at 122, then the operations of the flow chart 102 continues at 124 where additional operational biases for the next elevation level of burners are determined and applied at 118 and evaluated at 120 after collecting data at 119. The process of calculating biases at steps 116 and 124 may be identical, with the understanding that step 124 includes the calculations performed in steps 110, 112, 114, and 116. Alternatively, if the operational biases applied to the one or more of the burners did not yield better combustion operation results as determined at 122, then the operations of the flow chart 102 continue at 126 where the operational biases applied to the one or more of the burners are rolled back and then optimization at the next elevation level can begin at 128. In one embodiment, this optimization at the next elevation level can begin after collecting more data for a predetermined time period in order to establish a baseline. Then operations 106-128 can be repeated. In general, these operations noted in the flow chart 102 can continue until there is a balancing of the air-to-fuel ratios between each of the burners, until no further combustion improvement is observed, and may resume when the boiler operation changes and optimization again becomes helpful. [0092] While, for purposes of simplicity of explanation, the operations shown in FIG. 5 are described as a series of acts. It is to be understood and appreciated that the subject innovation associated with FIG. 5 is not limited by the order of acts, as some acts may, in accordance therewith, occur in a different order and/or concurrently with other acts from that shown and described herein. For example, those skilled in the art will understand and appreciate that a methodology or operations depicted in FIG. 5 could alternatively be represented as a series of interrelated states or events, such as in a state diagram. Moreover, not all illustrated acts may be required to implement a methodology in accordance with the innovation. Furthermore, interaction diagram(s) may represent methodologies, or methods, in accordance with the subject disclosure when disparate entities enact disparate portions of the methodologies. Further yet, two or more of the disclosed example methods can be implemented in combination with each other, to accomplish one or more features or advantages described herein

[0093] To this extent, it is understood that the guided search optimization algorithm can be used to optimize elevation levels of the T-fired boiler in a different sequence than that described with respect to FIG. 5. For example, the guided search optimization algorithm can determine and apply operational biases to burners at one or more elevation levels at a time. Further, because sometimes on boiler loads certain elevation levels of burners are not running, the guided search optimization algorithm can be configured to skip those levels in a combustion optimization. In one embodiment, instead of directing the flow of operations to step 124 after determining an improved combustion at step 122, the flow can be directed to step 110 for a determination of air through each of the burners and the subsequent steps thereafter.

[0094] FIG. 6 is a flow chart 130 describing a method for optimizing combustion in a wall-fired boiler according to an embodiment of the invention. In general, a wall-fired boiler includes burners located perpendicularly on one wall or opposing walls of the boiler. As a result of this configuration of burners, a wall-fired boiler typically does not generate a swirling and rotating fireball like that in a T-fired boiler. Instead, the wall-fired boiler generates multiple flames from the burners into the burner zone where the flames move around one another. Also, because there may be a smaller number of burners in comparison to a T-fired boiler one pulverizer may feed a smaller number of the burners.

[0095] The method for optimizing combustion in a wall-fired boiler as described in the flow chart 130 of FIG. 6 has similarities with the flow chart 102 described with respect to T-fired boilers. For example, the flow chart 130 of FIG. 6 collects sensor data at 132, preprocesses the data at 134, checks for major operational changes at 136, determines the air near each of the burners from the primary air flows at 138, adds the primary air, secondary air, and tertiary air through the burner if present in the burner design. If auxiliary air or closely coupled overfire air is present above or near each of the burners, it may be added to the air flow near that burner to ascertain the local combustion air near each burner at 140, and determines the air-to-fuel ratios (i.e. , stoichiometry) near each of the burners at 142. The operations in FIG. 6 are performed in substantially the same manner as described with reference to the flow chart in FIG. 5 and are not repeated for brevity. In general, the differences in the flow chart 130 of FIG. 6 with the flow chart of FIG. 5 is due to the mechanical distinctions between the wall-fired boiler and the T-fired boiler. These difference result in a variation in how the operational biases are determined, applied, and evaluated.

[0096] In one embodiment, the group of burners selected for optimization may include those with the highest and lowest air-to-fuel ratios, with subsequent optimization groups including the burners with the next highest and next lowest air- to-fuel ratios. This embodiment addresses the burners farthest away from the average air-to-fuel ratio first with the understanding that they are likely to make the biggest improvement in overall combustion. In another embodiment, all burners fed by a single pulverizer are selected for optimization together, with subsequent groups of burners fed by different pulverizers. This embodiment is more similar to that for tangentially fired boilers where all burners fed by a single pulverizer may be optimized together. Many wall-fired boiler designs feed a group of burners across the width of the boiler from each pulverizer, so this embodiment may produce more even combustion side-to-side across the furnace. Those skilled in the art will recognize that additional methods of grouping burners for optimization are possible and these methods are not excluded from the embodiments of the invention.

[0097] These aspects of the optimization of the burners of a wall-fired boiler are depicted in FIG. 6 as follows. Operational biases that redistribute air through or near one or more of the burners at a wall of the boiler to be more consistent with the air-to-fuel ratios with other burners around that wall are determined at 144 while maintaining approximately the same amount of air at each longitudinal distance from the burners. As used herein “at each longitudinal distance” means the distances in the direction of flue gas flow from the burner at which secondary air from the burner, tertiary air from the burner if present, and any air from any additional nozzles near the burner if present are expected to join the primary air and fuel from the burner to join in combusting the fuel. For a horizontal wall fired boiler such as many industrial sized boilers, the longitudinal distance will be measured along a straight line emitted from the center-line of the burner. As the burners in a typical vertical wall fired boiler are pointed horizontally across the furnace while the flue gasses flow upward, these longitudinal distances may be measured along a curve rather than a straight line.

[0098] The determined operational biases can then be applied at 146 to one or more burners at a controlled rate to avoid significant boiler transients. In one embodiment, the determined operational biases are conveyed to the plant control unit 100 via the interface component 82. The plant control unit 100 can then use air control logic to apply the operational biases to the one burner at a controlled rate via the air flow control devices 30 (FIG. 3).

[0099] The data acquisition and preprocessing component 78 can then collect and preprocess data from the boiler at 1 7 after running it with the applied biases for a predetermined amount of time. The combustion operation of the boiler is then evaluated at 148 to determine whether the applied operational biases lead to better combustion operation results than combustion operation results obtained prior to applying the operational biases.

[00100] If the operational biases applied to the one or more burner(s) yields better combustion operation results as determined at 150, then the operations of the flow chart 130 continues at 152 where additional operational biases for the burner having the next highest air-to-fuel ratio imbalance or the burners fed from a different pulverizer is determined and applied at 146 and evaluated at 148 after collecting sensor data at 147. Alternatively, if the operational biases applied to the one burner did not yield better combustion operation results as determined at 150, then the operations of the flow chart 130 continue at 154 where the operational biases applied to the one or more burners are rolled back and then optimization of the next one or more burners can begin at 156. In one embodiment, this optimization of the next one or more burners can begin after collecting more data for a predetermined time period in order to establish a baseline. Then operations 134-156 can be repeated. In general, these operations noted in the flow chart 130 can continue until there is a balancing of the air-to-fuel ratios between each of the burners, until no further combustion improvement is observed, resuming again when boiler operations such as the energy generated or the selection of burners in service changes.

[00101] While, for purposes of simplicity of explanation, the operations shown in FIG. 6 are described as a series of acts. It is to be understood and appreciated that the subject innovation associated with FIG. 6 is not limited by the order of acts, as some acts may, in accordance therewith, occur in a different order and/or concurrently with other acts from that shown and described herein. For example, those skilled in the art will understand and appreciate that a methodology or operations depicted in FIG. 6 could alternatively be represented as a series of interrelated states or events, such as in a state diagram. Moreover, not all illustrated acts may be required to implement a methodology in accordance with the innovation. Furthermore, interaction diagram(s) may represent methodologies, or methods, in accordance with the subject disclosure when disparate entities enact disparate portions of the methodologies. Further yet, two or more of the disclosed example methods can be implemented in combination with each other, to accomplish one or more features or advantages described herein. To this extent, instead of sequencing through the burners starting with the highest and lowest air-to-fuel ratios or grouping all burners fed from the same pulverizer together as discussed in FIG. 6, it is possible to sequence through multiple burner groups at a time. Those skilled in the art will recognize that other methods of grouping and sequencing pulverizers for optimization, including larger or smaller groups, are possible in addition to the two embodiments described above. These additional grouping and sequencing methods are not excluded from the various embodiments of the invention.

[00102] Although the flow charts depicted in FIGS. 5 and 6 describe in general an iterative process of determining additional operational biases upon improved combustion or rolling back biases that did not improve combustion and determining new biases to apply, other approaches can be considered in scenarios where multiple iterations fail to result in improved combustion after the air-to-fuel balancing of the one or more burners, or to provide additional combustion improvements after all burners have been evaluated for optimization. For example, in one embodiment, the optimizer sequence may try different air flow adjustments designed to achieve air-to-fuel ratio imbalances that are in between the currently calculated air-to-fuel ratio imbalances and the calculated air flows required for perfect air-to-fuel ratio balances between all the burners being optimized, i.e., stepping part way towards the target of perfect air-to-fuel ratio balance. In another embodiment, the optimization sequence may temporarily skip optimization of an elevation where the previous optimization biases have failed to improve combustion after one or more optimization attempts.

[00103] In another embodiment, the calculated air flow biases may be calculated to further increase the calculated air-to-fuel ratio imbalances after one or more previous optimization steps did not result in improved combustion. This embodiment is intended to accommodate inaccurate sensor measurements of air and or fuel flows, and account for unexpected interactions between burners in different corners or elevations of a tangentially fired furnace or between different burners on the front and/or rear wall of a wall fired furnace. For example, excess air supplied near one burner might reduce CO emissions from another nearby burner or might contribute to NOx emissions from another nearby burner or slag formed from the combustion of solid fuels may partially block air or fuel flow into the combustion chamber through one or more nozzles.

[00104] Another enhancement to the flow charts depicted in FIGS. 5 and 6 can include adding steps at the end of the procedures that include adjusting secondary air and flue gas recirculation rates after adjusting individual burners. For example, in one embodiment, the overall excess air setpoint which controls the total amount of air provided for combustion may be increased to reduce CO emissions and potentially reduce the amount of un-bumed carbon from the solid fuel remaining in the ash, or the total amount of combustion air may be reduced to lower NOx emissions and improve boiler efficiency. In another embodiment for boilers equipped with Flue Gas Recirculation (FGR) systems, the volume of recirculated flue gas may be increased to reduce NOx emissions or may be reduced to improve flame stability. In another embodiment, the fraction of combustion air injected into the burner zone of a tangentially fired or wall fired boiler may be decreased while increasing the fraction of Secondary Over-Fired Air (SOFA) to further stage combustion and reduce NOx emissions, or the fraction of combustion air injected into the burner zone may be increased and the fraction of combustion air injected into the SOFA zone decreased to improve flame stability. In another embodiment the amount of Close- Coupled Overfire Air (CCOFA) in a tangentially fired furnace may be adjusted to reduce NOx or CO emissions. In another embodiment, the burner tilts in a tangentially fired furnace may be adjusted to better balance the amount of energy absorbed in the furnace walls versus the amount of energy absorbed in superheater, reheater, and economizer heat exchangers.

[00105] The embodiments listed above are not shown in the flowcharts in FIGS. 5 or FIGS. 6, however, those skilled in the art will recognize that the embodiments listed above, or similar adjustments not listed here, may be applied after individual groups of burners have been optimized, may be applied after all burners have been selected for optimization, or may be applied based on the results of specific criteria used for evaluating boiler combustion. All of these alternatives, while not shown in FIGS. 5 or FIGS. 6, are not excluded from the various embodiments of the invention.

[00106] In order to provide a context for the various aspects of the disclosed subject matter, FIGS. 7 and 8 as well as the following discussion are intended to provide a brief, general description of a suitable environment in which the various aspects of the disclosed subject matter may be implemented.

[00107] With reference to FIG. 7, an example environment 1000 for implementing various aspects of the aforementioned subject matter includes a computer 1012. The computer 1012 includes a processing unit 1014, a system memory 1016, and a system bus 1018. The system bus 1018 couples system components including, but not limited to, the system memory 1016 to the processing unit 1014. The processing unit 1014 can be any of various available processors. Multi-core microprocessors and other multiprocessor architectures also can be employed as the processing unit 1014. [00108] The system bus 1018 can be any of several types of bus structure(s) including the memory bus or memory controller, a peripheral bus or external bus, and/or a local bus using any variety of available bus architectures including, but not limited to, 8-bit bus, Industrial Standard Architecture (ISA), Micro-Channel Architecture (MSA), Extended ISA (EISA), Intelligent Drive Electronics (IDE), Serial Advanced Technology Attachment (SATA), IEEE 1394 FireWire, VESA Local Bus (VLB), Peripheral Component Interconnect (PCI) and PCI Express, Universal Serial Bus (USB), Advanced Graphics Port (AGP), Personal Computer Memory Card International Association bus (PCMCIA), and Small Computer Systems Interface (SCSI).

[00109] The system memory 1016 includes volatile memory 1020 and nonvolatile memory 1022. The basic input/output system (BIOS), containing the basic routines to transfer information between elements within the computer 1012, such as during start-up, is stored in nonvolatile memory 1022. By way of illustration, and not limitation, nonvolatile memory 1022 can include read only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable PROM (EEPROM), or flash memory. Volatile memory 1020 includes random access memory (RAM), which acts as external cache memory. By way of illustration and not limitation, RAM is available in many forms such as synchronous RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), double data rate SDRAM (DDR SDRAM), enhanced SDRAM (ESDRAM), Synchlink DRAM (SLDRAM), and direct Rambus RAM (DRRAM).

[00110] Computer 1012 also includes removable/non-removable, volatile/non- volatile computer storage media. FIG. 7 illustrates, for example a disk storage 1024. Disk storage 1024 includes, but is not limited to, devices like a magnetic disk drive, floppy disk drive, tape drive, Jaz drive, Zip drive, LS-100 drive, flash memory card, or USB memory stick. In addition, disk storage 1024 can include storage media separately or in combination with other storage media including, but not limited to, an optical disk drive such as a compact disk ROM device (CD-ROM), CD recordable drive (CD-R Drive), CD rewritable drive (CD- RW Drive) or a digital versatile disk ROM drive (DVD-ROM). To facilitate connection of the disk storage 1024 to the system bus 1018, a removable or non-removable interface is typically used such as interface 1026.

[00111] It is to be appreciated that FIG. 7 describes software that acts as an intermediary between users and the basic computer resources described in suitable operating environment 1000. Such software includes an operating system 1028. Operating system 1028, which can be stored on disk storage 1024, acts to control and allocate resources of the computer 1012. System applications 1030 take advantage of the management of resources by operating system 1028 through program modules 1032 and program data 1034 stored either in system memory 1016 or on disk storage 1024. It is to be appreciated that one or more embodiments of the subject disclosure can be implemented with various operating systems or combinations of operating systems.

[00112] A user enters commands or information into the computer 1012 through input device(s) 1036. Input devices 1036 include, but are not limited to, a pointing device such as a mouse, trackball, stylus, touch pad, keyboard, microphone, joystick, game pad, satellite dish, scanner, TV tuner card, digital camera, digital video camera, web camera, and the like. These and other input devices connect to the processing unit 1014 through the system bus 1018 via interface port(s) 1038. Interface port(s) 1038 include, for example, a serial port, a parallel port, a game port, and a universal serial bus (USB). Output device(s) 1040 use some of the same type of ports as input device(s) 1036. Thus, for example, a USB port may be used to provide input to computer 1012, and to output information from computer 1012 to an output device 1040. Output adapters 1042 are provided to illustrate that there are some output devices 1040 like monitors, speakers, and printers, among other output devices 1040, which require special adapters. The output adapters 1042 include, by way of illustration and not limitation, video and sound cards that provide a means of connection between the output device 1040 and the system bus 1018. It should be noted that other devices and/or systems of devices provide both input and output capabilities such as remote computer(s) 1044.

[00113] Computer 1012 can operate in a networked environment using logical connections to one or more remote computers, such as remote computer(s) 1044. The remote computer(s) 1044 can be a personal computer, a server, a router, a network firewall, a network PC, a workstation, a microprocessor based appliance, a peer device or other common network node and the like, and typically includes many or all of the elements described relative to computer 1012. For purposes of brevity, only a memory storage device 1046 is illustrated with remote computer(s) 1044. Remote computer(s) 1044 is logically connected to computer 1012 through a network interface 1048 and then physically connected via communication connection 1050. Network interface 1048 encompasses communication networks such as local-area networks (LAN) and wide-area networks (WAN). LAN technologies include Fiber Distributed Data Interface (FDDI), Copper Distributed Data Interface (CDDI), Ethernet/IEEE 802.3, Token Ring/IEEE 802.5 and the like. WAN technologies include, but are not limited to, point-to-point links, circuit switching networks like Integrated Services Digital Networks (ISDN) and variations thereon, packet switching networks, and Digital Subscriber Lines (DSL).

[00114] Communication connection(s) 1050 refers to the hardware/software employed to connect the network interface 1048 to the system bus 1018. While communication connection 1050 is shown for illustrative clarity inside computer 1012, it can also be external to computer 1012. The hardware/software necessary for connection to the network interface 1048 includes, for exemplary purposes only, internal and external technologies such as, modems including regular telephone grade modems, cable modems and DSL modems, ISDN adapters, wireless networks such as WiFi or Bluetooth, and Ethernet cards. [00115] FIG. 8 is a schematic block diagram of a sample computing environment 1100 with which the disclosed subject matter can interact. The sample computing environment 1100 includes one or more client(s) 1102. The client(s) 1102 can be hardware and/or software (e.g., threads, processes, computing devices). The sample computing environment 1100 also includes one or more server(s) 1104. The server(s) 1104 can also be hardware and/or software (e.g., threads, processes, computing devices). The servers 1104 can house threads to perform transformations by employing one or more embodiments as described herein, for example. One possible communication between a client 1102 and servers 1104 can be in the form of a data packet adapted to be transmitted between two or more computer processes. The sample computing environment 1100 includes a communication framework 1106 that can be employed to facilitate communications between the client(s) 1102 and the server(s) 1104. The client(s) 1102 are operably connected to one or more client data store(s) 1108 that can be employed to store information local to the client(s) 1102. Similarly, the server(s) 1104 are operably connected to one or more server data store(s) 1110 that can be employed to store information local to the servers 1104.

[00116] From the foregoing description, it should be clear that the system and method for optimizing combustion in boiler per the various embodiments has many technical effects and improvements that equate to technical distinctions over conventional approaches used to optimize a boiler. For example, the fuel flow sensors 64, which can comprise coal flow sensors in embodiments in which a pulverized solid fuel such as coal is provided to a boiler, provide new real-time measurements of the fuel flow to each individual burner. Typically, these fuel flow sensors are only used temporarily for a manual pulverizer or boiler tuning. Another technical distinction with the various embodiments, is the air flows through and near each individual burner can be calculated using a number of data that includes, but is not limited to, auxiliary air flow sensors, plant control data, air flow control device information (e.g., status, geometry, positioning), and mill test data if available. To this extent, this provides a matching air flow near each burner which are combined with the fuel flow measurements to calculate the local stoichiometry near each burner.

[00117] The various embodiments also differ in that a guided search optimization algorithm can be utilized to perform the combustion optimization. The guided search optimization algorithm, which mixes a physics-based approach that involves measured and/or calculated stoichiometry of the burners in the boiler that can include a T-fired boiler and a wall-fired boiler, with a search algorithm customized to find operational biases that can be applied to one or more of the burners to yield better combustion operation results for the boiler while accounting for measurement inaccuracies and unexpected interactions between burners as the operational biases are determined and evaluated.

[00118] By more effectively balancing the local stoichiometry near each burner, pockets of high or low oxygen in the fireball or furnace volume can be reduced. The low oxygen pockets create CO and may contribute to increased un-burned carbon in the ash, while the high oxygen pockets increase NOx. More even local burner stoichiometry has been seen to reduce CO and NOx simultaneously. In contrast, model based low-NOx combustion optimization approaches typically reduce NOx while increasing CO until it’s just below the maximum allowed value. After balancing individual burners, overall air flow may be reduced to improve efficiency and further reduce NOx if desired.

[00119] Another technical distinction of the various embodiments in comparison to conventional approaches used to optimize a boiler is that no boiler model is included in the embodiments. This eliminates issues with boiler model accuracy under changing equipment and process conditions. It also does not require a wide range of historical operating data to construct and tune the boiler model.

[00120] With these technical distinctions, the various embodiments have several advantages over conventional approaches used to optimize a boiler. For example, these embodiments can help reduce minimum boiler load in response to intermittent renewable energy with better low-load flame stability. Also, the embodiments can help increase efficiency at higher boiler loads to reduce operating costs and emissions by reducing excess air while maintaining CO and NOx emissions within the environmental permit limits. In particular, NOx and CO emissions can be reduced simultaneously. In addition, fuel flow sensors, air flow sensors, flue gas sensors, and flame scanners that can be used in the embodiments can provide more accurate measurements of fuel flow and air flow supporting even burner stoichiometry. By using a guided search optimization algorithm, the embodiments can provide an improved response to unexpected boiler behavior, fuel changes, and operating modes. Additionally, because a physics-based approach is used with the embodiments and not a model-based methodology, periodic retuning of the model to account for inaccuracies in the model that arise over time can be avoided.

[00121] The above description of illustrated embodiments of the subject disclosure, including what is described in the Abstract, is not intended to be exhaustive or to limit the disclosed embodiments to the precise forms disclosed. While specific embodiments and examples are described herein for illustrative purposes, various modifications are possible that are considered within the scope of such embodiments and examples, as those skilled in the relevant art can recognize. For example, parts, components, steps and aspects from different embodiments may be combined or suitable for use in other embodiments even though not described in the disclosure or depicted in the figures. Therefore, since certain changes may be made in the above-described invention, without departing from the spirit and scope of the invention herein involved, it is intended that all of the subject matter of the above description shown in the accompanying drawings shall be interpreted merely as examples illustrating the inventive concept herein and shall not be construed as limiting the invention.

[00122] In this regard, while the disclosed subject matter has been described in connection with various embodiments and corresponding figures, where applicable, it is to be understood that other similar embodiments can be used or modifications and additions can be made to the described embodiments for performing the same, similar, alternative, or substitute function of the disclosed subject matter without deviating therefrom. Therefore, the disclosed subject matter should not be limited to any single embodiment described herein, but rather should be construed in breadth and scope in accordance with the appended claims below. For example, references to “one embodiment” of the present invention are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features.

[00123] In the appended claims, the terms “including” and “in which” are used as the plain-English equivalents of the respective terms “comprising” and “wherein.” Moreover, in the following claims, terms such as “first,” “second,” “third,” “upper,” “lower,” “bottom,” “top,” etc. are used merely as labels, and are not intended to impose numerical or positional requirements on their objects. The terms “substantially,” “generally,” and “about” indicate conditions within reasonably achievable manufacturing and assembly tolerances, relative to ideal desired conditions suitable for achieving the functional purpose of a component or assembly. Further, the limitations of the following claims are not written in means-plus-function format and are not intended to be interpreted as such, unless and until such claim limitations expressly use the phrase “means for” followed by a statement of function void of further structure.

[00124] What has been described above includes examples of systems and methods illustrative of the disclosed subject matter. It is, of course, not possible to describe every combination of components or methodologies here. One of ordinary skill in the art may recognize that many further combinations and permutations of the claimed subject matter are possible. Furthermore, to the extent that the terms "includes," "has," "possesses," and the like are used in the detailed description, claims, appendices and drawings, such terms are intended to be inclusive in a manner similar to the term "comprising" as "comprising" is interpreted when employed as a transitional word in a claim. That is, unless explicitly stated to the contrary, embodiments “comprising,” “including,” or “having” an element or a plurality of elements having a particular property may include additional such elements not having that property.

[00125] This written description uses examples to disclose several embodiments of the invention, including the best mode, and also to enable one of ordinary skill in the art to practice the embodiments of invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to one of ordinary skill in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.

[00126] Further aspects of the invention are provided by the subject matter of the following clauses:

[00127] A system, comprising: a boiler having a furnace with a burner zone for combustion of fuel and air from which flue gases are produced, the boiler including one of a tangentially-fired (T-fired) boiler and a wall-fired boiler; a plurality of burners located about the boiler that define an arrangement of fuel and air introduction locations for introducing a mix of primary fuel and air into the burner zone to generate a flame therein, each of the burners including a fuel nozzle operative to provide a stream of the primary fuel and air into the burner zone; a plurality of auxiliary air nozzles located about the plurality of burners that are operative to supply a stream of auxiliary air into the burner zone for contribution in the combustion with the primary fuel and air; a plurality of air flow control devices to control the supply of selected streams of auxiliary air into the burner zone by the plurality of auxiliary air nozzles; a plurality of fuel flow sensors to obtain measurements of the flow of the primary fuel to the plurality of burners, each of the fuel flow sensors operative to obtain real-time measurements of the flow of the primary fuel that is supplied to one of the plurality of burners via a corresponding fuel nozzle; one or more auxiliary air flow sensors to obtain measurements of the flow of the auxiliary air supplied into the burner zone by one or more of the plurality of auxiliary air nozzles, each of the auxiliary air flow sensors operative to obtain real-time measurements of the flow of the auxiliary air that is supplied into the burner zone by the one or more of the plurality of auxiliary air nozzles; a plurality of flame scanners to obtain flame scan data of the flame in the burner zone; a plurality of flue gas sensors operative to obtain measurements of a plurality of properties associated with the flue gases, the measurements of the plurality of properties indicative of the combustion that occurred in the burner zone, each of the flue gas sensors operative to obtain measurements of at least one of the properties; and a controller operative to optimize the combustion of the fuel and air in the burner zone as a function of information provided by the plurality of fuel flow sensors, the one or more auxiliary air flow sensors, the plurality of flame scanners, the plurality of flue gas sensors and the plurality of air flow control devices, wherein the controller includes a guided search optimization algorithm that is configured to mix measured and/or calculated stoichiometry of the burners in the boiler with a search algorithm customized to find operational biases that are applied to one or more of the burners to yield better combustion operation results for the boiler, while accounting for measurement inaccuracies and unexpected interactions between burners as the operational biases are determined and evaluated.

[00128] The system of the preceding clause, where the guided search optimization algorithm is configured to perform operations including: determining an amount of air near each of the burners; determining air-to-fuel ratios near each of the burners; determining operational biases that redistribute air through or near one or more burners to be more consistent with the air-to-fuel ratios with other burners while maintaining approximately the same amount of air at each elevation level of a vertical furnace in the T-fired boiler or each longitudinal distance from the burners of a horizontal furnace in a wall-fired boiler; and applying the operational biases to or near one or more of the burners.

[00129] The system of any of the preceding clauses, wherein the guided search optimization algorithm is configured to further perform operations including: evaluating combustion operation of the boiler after applying the operational biases to or near the one or more of the burners to determine if the applied operational biases resulted in better combustion operation results than combustion operation results obtained prior to applying the operational biases, the evaluating includes assessing one or more combustion operation parameters according to a weighting factor applied to each of the combustion operation parameters, wherein each weighting factor is assigned a lighter or heavier degree of importance with respect to the evaluating of the combustion operation of the boiler; if the operational biases applied to or near the one or more of the burners yield better combustion operation results, determining additional operational biases and applying to or near one or more additional burners; and if the operational biases applied to or near the one or more of the burners did not yield better combustion operation results, rolling back the operational biases applied to or near the one of the burners, collecting more data from the plurality of fuel flow sensors, the one or more auxiliary air flow sensors, the plurality of air flow control devices, the plurality of flue gas sensors and the plurality of flame scanners, and repeating the determining of the amount of air near each of the burners, the determining of the air-to-fuel ratios near each of the burners, determining another set of operational biases, applying the another set of operational biases to or near another one or more of the burners, and evaluating the combustion operation results yielded from the another set of operational biases applied to or near the another one or more of the burners.

[00130] The system of any of the preceding clauses, wherein the determined amount of air near each of the burners comprises the air in the stream of the primary fuel and air provided to the burner, the auxiliary air provided near the burner or as part of the burner but separate from the primary fuel and air stream, and if present closely coupled overfire air introduced into the burner zone above the plurality of burners for contribution in the combustion with the primary fuel and air and the auxiliary air.

[00131] The system of any of the preceding clauses, wherein the determined amount of air near each of the burners takes into account effective free flow areas of each of the plurality of auxiliary air nozzles, each of the effective free flow areas determined as a function of the nozzle and air flow control device designs and geometries.

[00132] The system of any of the preceding clauses, wherein the air-to-fuel ratios determined for near each of the burners is based on the fuel flow measurements of the fuel to the plurality of burners and the determined amount of air near each of the burners.

[00133] The system of any of the preceding clauses, wherein the evaluating of the combustion operation of the boiler comprises assessing one or more combustion operation parameters to determine if combustion operation with the operational biases applied to the one or more of the burners is better than combustion operation results obtained prior to applying the operational biases.

[00134] The system of any of the preceding clauses, wherein the guided search optimization algorithm is further configured to skip additional optimization after repeated optimization failures or intentionally biasing in a wrong direction to improve combustion in cases of significant measurement errors or unexpected interactions between air and fuel injected near or through different burners.

[00135] The system of any of the preceding clauses, wherein the controller is configured to facilitate changes in an amount air in the burner zone, the changes include one or more of: increasing or decreasing excess air; increasing or decreasing a percentage of air in Secondary Over-Fired Air (SOFA) or Close- Coupled Overfire Air (CCOFA) in the T-fired boiler; changing burner tilt angles; and biasing air from side to side in the furnace, from top to bottom in the furnace, or from corner to corner in the furnace.

[00136] A method for optimizing combustion in a boiler having a furnace with a burner zone for combustion of fuel and air from which flue gases are produced, a plurality of burners with each including a fuel nozzle operative to provide a stream of primary fuel and air into the burner zone to generate a flame therein, a plurality of auxiliary air nozzles located about the plurality of burners that are operative to supply a stream of auxiliary air into the burner zone for contribution in the combustion with the primary fuel and air, a plurality of air flow control devices to control the supply of selected streams of auxiliary air into the burner zone by the plurality of auxiliary air nozzles, a plurality of fuel flow sensors to obtain measurements of the flow of the fuel to the plurality of burners, one or more auxiliary air flow sensors to obtain measurements of the flow of the auxiliary air supplied into the burner zone by one or more of the plurality of auxiliary air nozzles, a plurality of flame scanners to obtain flame scan data of the flame in the burner zone, a plurality of flue gas sensors operative to obtain measurements of a plurality of properties associated with the flue gases, a controller operative to perform the method for optimizing the combustion of the boiler as a function of fuel flow, air flows, flame data, flue gas data and information relating to plurality of air flow control devices, the method comprising: determining an amount of air near each of the burners; determining air-to-fuel ratios near each of the burners; determining operational biases that redistribute air through or near one or more burners to be more consistent with the air-to-fuel ratios with other burners while maintaining approximately the same amount of air at each elevation level of a vertical furnace in the T-fired boiler or each longitudinal distance from the burners of a horizontal furnace in a wall-fired boiler; and applying the operational biases to or near one or more of the burners.

[00137] The method of the preceding clause, further comprising: evaluating combustion operation of the boiler after applying the operational biases to or near the one or more of the burners to determine if the applied operational biases resulted in better combustion operation results than combustion operation results obtained prior to applying the operational biases, the evaluating includes assessing one or more combustion operation parameters according to a weighting factor applied to each of the combustion operation parameters, wherein each weighting factor is assigned a lighter or heavier degree of importance with respect to the evaluating of the combustion operation of the boiler; if the operational biases applied to or near the one or more of the burners yield better combustion operation results, determining additional operational biases and applying to or near one or more additional burners; and if the operational biases applied to or near the one or more of the burners did not yield better combustion operation results, rolling back the operational biases applied to or near the one of the burners, collecting more data from the plurality of fuel flow sensors, the one or more auxiliary air flow sensors, the plurality of air flow control devices, the plurality of flue gas sensors and the plurality of flame scanners, and repeating the determining of the amount of air near each of the burners, the determining of the air-to-fuel ratios near each of the burners, determining another set of operational biases, applying the another set of operational biases to or near another one or more of the burners, and evaluating the combustion operation results yielded from the another set of operational biases applied to or near the another one or more of the burners.

[00138] The method of any of the preceding clauses, wherein the determined amount of air near each of the burners comprises the air in the stream of the fuel and air provided to the burner, the auxiliary air provided near the burner or as part of the burner but separate from the primary fuel and air stream, and if present closely coupled overfire air introduced into the burner zone above the plurality of burners for contribution in the combustion with the primary fuel and air and the auxiliary air.

[00139] The method of any of the preceding clauses, wherein the determined amount of air near each of the burners takes into account effective free flow areas of each of the fuel nozzles and the plurality of auxiliary air nozzles, each of the effective free flow areas determined as a function of nozzle and air flow control device designs and geometries.

[00140] The method of any of the preceding clauses, further comprising skipping additional optimization after repeated optimization failures or intentionally biasing in a wrong direction to improve combustion in cases of significant measurement errors or unexpected interactions between air and fuel injected near or through different burners.

[00141] The method of any of the preceding clauses, further comprising facilitating changes in an amount air in the burner zone, the changes include one or more of: increasing or decreasing excess air; increasing or decreasing a percentage of air in Secondary Over-Fired Air (SOFA) or Close-Coupled Overfire Air (CCOFA) in the T-fired boiler; changing burner tilt angles; and biasing air from side to side in the furnace, from top to bottom in the furnace, or from corner to corner in the furnace.

Claims

WHAT IS CLAIMED IS:

1. A system (62), comprising: a boiler (12) having a furnace (14) with a burner zone (21 ) for combustion of fuel and air from which flue gases are produced, the boiler (12) including one of a tangentially-fired (T-fired) boiler and a wall-fired boiler; a plurality of burners located about the boiler (12) that define an arrangement of fuel and air introduction locations for introducing a mix of primary fuel and air into the burner zone (21 ) to generate a flame therein, each of the burners including a fuel nozzle operative to provide a stream of the primary fuel and air into the burner zone (21 ); a plurality of auxiliary air nozzles located about the plurality of burners that are operative to supply a stream of auxiliary air into the burner zone (21 ) for contribution in the combustion with the primary fuel and air; a plurality of air flow control devices (30) to control the supply of selected streams of auxiliary air into the burner zone (21 ) by the plurality of auxiliary air nozzles; a plurality of fuel flow sensors (64) to obtain measurements of the flow of the primary fuel to the plurality of burners, each of the fuel flow sensors (64) operative to obtain real-time measurements of the flow of the primary fuel that is supplied to one of the plurality of burners via a corresponding fuel nozzle; one or more auxiliary air flow sensors (66) to obtain measurements of the flow of the auxiliary air supplied into the burner zone (21 ) by one or more of the plurality of auxiliary air nozzles, each of the auxiliary air flow sensors (66) operative to obtain real-time measurements of the flow of the auxiliary air that is supplied into the burner zone (21 ) by the one or more of the plurality of auxiliary air nozzles; a plurality of flame scanners (46) to obtain flame scan data of the flame in the burner zone (21 ); a plurality of flue gas sensors (42) operative to obtain measurements of a plurality of properties associated with the flue gases, the measurements of the plurality of properties indicative of the combustion that occurred in the burner zone (21 ), each of the flue gas sensors (42) operative to obtain measurements of at least one of the properties; and a controller (72) operative to optimize the combustion of the fuel and air in the burner zone (21 ) as a function of information provided by the plurality of fuel flow sensors (64), the one or more auxiliary air flow sensors (66), the plurality of flame scanners (46), the plurality of flue gas sensors (42) and the plurality of air flow control devices (30), wherein the controller (72) includes a guided search optimization algorithm that is configured to mix measured and/or calculated stoichiometry of the burners in the boiler (12) with a search algorithm customized to find operational biases that are applied to one or more of the burners to yield better combustion operation results for the boiler (12), while accounting for measurement inaccuracies and unexpected interactions between burners as the operational biases are determined and evaluated.

2. The system (62) of claim 1 , where the guided search optimization algorithm is configured to perform operations including: determining an amount of air near each of the burners; determining air-to-fuel ratios near each of the burners; determining operational biases that redistribute air through or near one or more burners to be more consistent with the air-to-fuel ratios with other burners while maintaining approximately the same amount of air at each elevation level of a vertical furnace in the T-fired boiler or each longitudinal distance from the burners of a horizontal furnace in a wall-fired boiler; and applying the operational biases to or near one or more of the burners.

3. The system (62) of claim 2, wherein the guided search optimization algorithm is configured to further perform operations including: evaluating combustion operation of the boiler (12) after applying the operational biases to or near the one or more of the burners to determine if the applied operational biases resulted in better combustion operation results than combustion operation results obtained prior to applying the operational biases, the evaluating includes assessing one or more combustion operation parameters according to a weighting factor applied to each of the combustion operation parameters, wherein each weighting factor is assigned a lighter or heavier degree of importance with respect to the evaluating of the combustion operation of the boiler (12); if the operational biases applied to or near the one or more of the burners yield better combustion operation results, determining additional operational biases and applying to or near one or more additional burners; and if the operational biases applied to or near the one or more of the burners did not yield better combustion operation results, rolling back the operational biases applied to or near the one of the burners, collecting more data from the plurality of fuel flow sensors (64), the one or more auxiliary air flow sensors (66), the plurality of air flow control devices (30), the plurality of flue gas sensors (42) and the plurality of flame scanners (42), and repeating the determining of the amount of air near each of the burners, the determining of the air-to-fuel ratios near each of the burners, determining another set of operational biases, applying the another set of operational biases to or near another one or more of the burners, and evaluating the combustion operation results yielded from the another set of operational biases applied to or near the another one or more of the burners.

4. The system (62) according to claim 2, wherein the determined amount of air near each of the burners comprises the air in the stream of the primary fuel and air provided to the burner, the auxiliary air provided near the burner or as part of the burner but separate from the primary fuel and air stream, and if present closely coupled overfire air introduced into the burner zone (21 ) above the plurality of burners for contribution in the combustion with the primary fuel and air and the auxiliary air.

5. The system (62) according to claim 2, wherein the determined amount of air near each of the burners takes into account effective free flow areas of each of the plurality of auxiliary air nozzles, each of the effective free flow areas determined as a function of the nozzle and air flow control device designs and geometries.

6. The system (62) according to claim 2, wherein the air-to-fuel ratios determined for near each of the burners is based on the fuel flow measurements of the fuel to the plurality of burners and the determined amount of air near each of the burners.

7. The system (62) according to claim 3, wherein the evaluating of the combustion operation of the boiler (12) comprises assessing one or more combustion operation parameters to determine if combustion operation with the operational biases applied to the one or more of the burners is better than combustion operation results obtained prior to applying the operational biases.

8. The system (62) according to claim 3, wherein the guided search optimization algorithm is further configured to skip additional optimization after repeated optimization failures or intentionally biasing in a wrong direction to improve combustion in cases of significant measurement errors or unexpected interactions between air and fuel injected near or through different burners.

9. The system (62) according to claim 1 , wherein the controller (72) is configured to facilitate changes in an amount air in the burner zone (21 ), the changes include one or more of: increasing or decreasing excess air; increasing or decreasing a percentage of air in Secondary Over-Fired Air (SOFA) or Close-Coupled Overfire Air (CCOFA) in the T-fired boiler; changing burner tilt angles; and biasing air from side to side in the furnace, from top to bottom in the furnace (14), or from corner to corner in the furnace (14).

10. A method for optimizing combustion in a boiler (12) having a furnace (14) with a burner zone (21 ) for combustion of fuel and air from which flue gases are produced, a plurality of burners with each including a fuel nozzle operative to provide a stream of primary fuel and air into the burner zone (21 ) to generate a flame therein, a plurality of auxiliary air nozzles located about the plurality of burners that are operative to supply a stream of auxiliary air into the burner zone (21 ) for contribution in the combustion with the primary fuel and air, a plurality of air flow control devices (30) to control the supply of selected streams of auxiliary air into the burner zone (21 ) by the plurality of auxiliary air nozzles, a plurality of fuel flow sensors (64) to obtain measurements of the flow of the fuel to the plurality of burners, one or more auxiliary air flow sensors (66) to obtain measurements of the flow of the auxiliary air supplied into the burner zone (21 ) by one or more of the plurality of auxiliary air nozzles, a plurality of flame scanners (46) to obtain flame scan data of the flame in the burner zone (21 ), a plurality of flue gas sensors (42) operative to obtain measurements of a plurality of properties associated with the flue gases, a controller (72) operative to perform the method for optimizing the combustion of the boiler (12) as a function of fuel flow, air flows, flame data, flue gas data and information relating to plurality of air flow control devices, the method comprising: determining an amount of air near each of the burners; determining air-to-fuel ratios near each of the burners; determining operational biases that redistribute air through or near one or more burners to be more consistent with the air-to-fuel ratios with other burners while maintaining approximately the same amount of air at each elevation level of a vertical furnace in the T-fired boiler or each longitudinal distance from the burners of a horizontal furnace in a wall-fired boiler; and applying the operational biases to or near one or more of the burners.

11 . The method of claim 10, further comprising: evaluating combustion operation of the boiler (12) after applying the operational biases to or near the one or more of the burners to determine if the applied operational biases resulted in better combustion operation results than combustion operation results obtained prior to applying the operational biases, the evaluating includes assessing one or more combustion operation parameters according to a weighting factor applied to each of the combustion operation parameters, wherein each weighting factor is assigned a lighter or heavier degree of importance with respect to the evaluating of the combustion operation of the boiler (12); if the operational biases applied to or near the one or more of the burners yield better combustion operation results, determining additional operational biases and applying to or near one or more additional burners; and if the operational biases applied to or near the one or more of the burners did not yield better combustion operation results, rolling back the operational biases applied to or near the one of the burners, collecting more data from the plurality of fuel flow sensors (64), the one or more auxiliary air flow sensors (66), the plurality of air flow control devices (30), the plurality of flue gas sensors (42) and the plurality of flame scanners (46), and repeating the determining of the amount of air near each of the burners, the determining of the air-to-fuel ratios near each of the burners, determining another set of operational biases, applying the another set of operational biases to or near another one or more of the burners, and evaluating the combustion operation results yielded from the another set of operational biases applied to or near the another one or more of the burners.

12. The method of claim 10, wherein the determined amount of air near each of the burners comprises the air in the stream of the fuel and air provided to the burner, the auxiliary air provided near the burner or as part of the burner but separate from the primary fuel and air stream, and if present closely coupled overfire air introduced into the burner zone above the plurality of burners for contribution in the combustion with the primary fuel and air and the auxiliary air.

13. The method of claim 10, wherein the determined amount of air near each of the burners takes into account effective free flow areas of each of the fuel nozzles and the plurality of auxiliary air nozzles, each of the effective free flow areas determined as a function of nozzle and air flow control device designs and geometries.

14. The method of claim 11 , further comprising skipping additional optimization after repeated optimization failures or intentionally biasing in a wrong direction to improve combustion in cases of significant measurement errors or unexpected interactions between air and fuel injected near or through different burners.

15. The method of claim 11 , further comprising facilitating changes in an amount air in the burner zone (21 ), the changes include one or more of: increasing or decreasing excess air; increasing or decreasing a percentage of air in Secondary Over-Fired Air (SOFA) or Close-Coupled Overfire Air (CCOFA) in the T-fired boiler; changing burner tilt angles; and biasing air from side to side in the furnace, from top to bottom in the furnace, or from corner to corner in the furnace.