CN111947133B - Boiler and combustion system and use method thereof - Google Patents

Abstract

The invention discloses a boiler, a combustion system and a using method thereof, wherein the system comprises: the device comprises a separator, a primary air-powder pipeline, a waste gas utilization pipeline and a multi-layer thick-thin burner; the separator comprises: the separation body is provided with an inlet communicated with the primary air powder pipeline, a first outlet communicated with the multi-layer thick-thin burner and a second outlet communicated with the exhaust gas utilization pipeline; the multi-layer rich-lean burner comprises: one end of the communication mechanism with the gas-solid separation function is communicated with the first outlet, a plurality of isolated circulation cavities are arranged along the gravity direction and are communicated with the other end of the communication mechanism, and an adjusting piece which is at least partially positioned in the circulation cavities and can at least adjust the circulation area of the circulation cavity of the multilayer thick-thin burner positioned at the uppermost part; the exhaust gas utilization pipeline comprises a first exhaust gas outlet valve for controlling the on-off of the exhaust gas utilization pipeline. The invention can flexibly adjust the concentration of the pulverized coal according to the load demand and ensure the stable combustion of the burner.

Description

Boiler, combustion system and method of use thereof

Technical Field

The invention relates to the technical field of pulverized coal combustion, and in particular to a boiler and a combustion system and a use method thereof.

Background technique

At present, my country's thermal power units are showing the characteristics of structural surplus and increasingly higher requirements for flexible operation. Therefore, many thermal power plants have to consider the stable combustion performance of boilers when the units are under low load or ultra-low load.

Thermal power units use a large number of direct current pulverized coal burners. Specifically, a coal mill has four burners per layer. When in use, the burners and coal mills have multiple layers, and one or more layers of coal mills and burners can be switched on and off to adapt to changes in load.

However, the inventors found that the existing technology for adjusting the number of layers of the coal mill and the burner is restricted by the primary wind duct's requirements for the primary wind speed. The main reason is that in order to keep the coal powder carried by the primary wind from being deposited, the primary wind speed must be greater than the critical value. When the unit load is reduced, the coal powder flow rate and the primary wind speed are required to be reduced at the same time according to the combustion requirements. However, the restriction requirement of the critical value of the primary wind speed makes it impossible to reduce the wind speed after it drops to the critical value, that is, the primary wind speed always needs to be guaranteed to be greater than or equal to the critical wind speed. When the primary wind speed cannot be reduced any further, as the coal powder flow rate decreases, the proportion of the primary air volume (air volume/(air volume + coal powder volume)) becomes higher and higher, which can easily lead to the flameout of the burner, that is, the ignition and stable combustion performance decreases, and even the environmental protection performance gradually decreases due to the increase in NOx emissions. On the whole, the lower limit of the performance of the above-mentioned burner (including ignition and stable combustion performance and environmental protection performance) limits the peak-shaving depth of the boiler load. For the peak-shaving unit, its peak-shaving capacity is limited by the boiler's ability to adapt to high and low loads, and the minimum operating load is one of the most important indicators of the unit's peak-shaving.

In the history of burner technology development, PM burners, wide-ratio pulverized coal burners, and A-PM burners have appeared, which can reduce the lower limit of load regulation to a certain extent. However, this type of regulation technology belongs to passive regulation, and passively regulated burners are still insufficient within the load variation range of current thermal power units. The performance lower limit of a single burner still limits the peak regulation depth of boiler load.

At present, Chinese patent CN108413387A provides a two-way dual-stage combustion technology for pulverized coal boilers. This technology adds a baffle to the thick and thin type burner to adjust the flow area, thereby improving the low-load stable combustion capability of the boiler. However, after analysis, the inventor found that the patent has the following defects: after setting the baffle, not only does it not reduce the proportion of the primary air volume, but also because the cross-sectional area of the flow is reduced, the wind speed will be greatly increased, which makes the burner's stable combustion capability worse overall.

Summary of the invention

In order to overcome at least one defect in the prior art, the present invention provides a boiler and a combustion system and a use method thereof, which can flexibly adjust the coal powder concentration according to load demand and ensure the stable combustion of the burner.

The above-mentioned purpose of the present invention can be achieved by adopting the following technical solutions:

A combustion system comprises: a separator, a primary air-powder pipeline, an exhaust gas utilization pipeline and a multi-layer thick-lean burner;

The separator comprises: a separation body, the separation body is provided with an inlet connected to the primary air-powder pipeline, a first outlet connected to the multi-layer thick-lean burner, and a second outlet capable of being connected to the exhaust gas utilization pipeline;

The multi-layer thick-lean burner comprises: a connecting mechanism with a gas-solid separation function, one end of the connecting mechanism is connected to the first outlet, a plurality of isolated flow cavities are connected to the other end of the connecting mechanism and are arranged along the gravity direction, and an adjusting member at least partially located in the flow cavity, the adjusting member can at least adjust the flow area of the flow cavity located at the top of the multi-layer thick-lean burner;

The exhaust gas utilization pipeline includes a first exhaust gas outlet valve for controlling the on-off of the exhaust gas utilization pipeline. When the first exhaust gas outlet valve is in an open state, part of the air-powder separated by the separator flows through the exhaust gas utilization pipeline and can flow to the furnace.

Furthermore, the exhaust gas utilization pipeline includes a main pipe section connected to the second outlet of the separator, and the first exhaust gas outlet valve is arranged on the main pipe section. Along the exhaust gas flow path, the exhaust gas utilization pipeline also includes at least one branch pipe, and the branch pipe can directly or indirectly introduce the exhaust gas into the furnace.

Furthermore, the branch pipe includes a waste gas recirculation branch pipe connected to the main pipe section, one end of the waste gas recirculation branch pipe is connected to the main pipe section, and the other end is connected to the flow cavity located at the top of the multi-layer rich-lean burner, and the connection position between the waste gas recirculation branch pipe and the flow cavity is located downstream of the regulating member.

Furthermore, the branch pipe comprises an exhaust gas guide branch pipe connected to the main pipe section, one end of the exhaust gas guide branch pipe is connected to the main pipe section, and the other end is an exhaust gas direct combustion nozzle for guiding the exhaust gas to the furnace.

Furthermore, the connecting mechanism is a turning inlet section arranged between the first outlet of the separator and the inlet of the multi-layer rich-lean burner, the flow cavity of the separator extends as a whole along the horizontal direction, and a predetermined angle is formed between the overall extension direction of the turning inlet section and the horizontal direction.

Furthermore, the combustion system also includes a secondary air main circuit and a secondary air branch circuit connected to the secondary air main circuit, the outlet end of the secondary air main circuit is a secondary air nozzle; one end of the secondary air branch circuit is connected to the secondary air main circuit, and the other end is at least connected to the flow cavity located at the bottom of the multi-layer thick and thin burner.

Furthermore, a mixer is provided in the secondary air main path, the end of the secondary air main path is a secondary air nozzle, an extension section extending to the mixer is provided at one end of the main pipe section away from the separator, and a second exhaust gas outlet valve is provided on the extension section. When the second exhaust gas outlet valve is opened, the exhaust gas entering the mixer from the main pipe section and the extension section is mixed with the wind entering the mixer from the secondary air main path, and then sprayed toward the furnace through the secondary air nozzle of the secondary air main path.

Furthermore, the multi-layer rich-lean burner includes an extremely dilute phase layer at the top and a dilute phase layer below the extremely dilute phase layer, and a separator is provided between the extremely dilute phase layer and the dilute phase layer at the junction near the nozzle.

Furthermore, a first safety valve is provided on the exhaust gas recirculation branch pipe near the multi-layer rich-lean burner, and a first switch valve is provided between the first safety valve and the main pipe section.

A boiler comprises: a plurality of coal mills, at least one outlet of which is connected to any of the above-mentioned combustion systems.

A method for using the boiler comprises:

When the power generation load is higher than the first preset value, the output of the grinding machine and the air volume of the fan are adjusted to adjust the input of the fuel amount and the flow rates of the primary air and the secondary air to match the unit load;

When the power generation load is higher than the second preset value and lower than the first preset value, the output of the grinding mill is adjusted, and the adjustment member of the thick and thin multi-layer burner and the exhaust gas outlet ratio of the first outlet and the second outlet of the separator are adjusted to match the unit load;

When the power generation load is lower than the second preset value, the number of coal mills in use, the number of burner layers and the corresponding proportions of primary air and secondary air flow are adjusted to match the unit load.

In the combustion system provided in the embodiment of the present application, when in use, the primary air powder flows to the separator through the primary air powder pipeline, and the air powder with very low coal powder content is separated as exhaust gas. When the air powder with very low coal powder content is separated from the primary air powder, the proportion of air volume can be effectively reduced. And since this method does not directly reduce the circulation area of the air powder, it will not increase the flow rate of the air powder and will not affect the stable combustion performance of the multi-layer thick and thin burner.

The pulverized coal airflow concentrated by the separator flows through a turning inlet section with a certain inclination, and is led to the flow cavities corresponding to the multi-layer thick-thin separation burners according to their different concentrations. An adjusting member (baffle) for adjusting the flow area is installed in the extremely dilute phase layer of the multi-layer thick-thin burner, which is used to adjust the flow area at low load, thereby maintaining the flow rate of the gas-solid two-phase flow at the burner nozzle and the stiffness of the flame, thereby improving the combustion effect.

In addition, in the extremely dilute phase layer of the multi-level rich-lean burner, there is an exhaust gas guide branch pipe connected to the downstream of the baffle; when the unit is under low load, a portion of the exhaust gas separated by the separator returns to the flow cavity at the top through the exhaust gas recirculation branch pipe, which is used to purge the corresponding flow cavity and exhaust gas reburning. At the same time, the ejected exhaust gas can exert a force on the flame ejected from the adjacent area, preventing the flame in the adjacent area from backfired to the top flow cavity (extremely dilute phase layer).

A secondary air branch inlet is also provided on the wall of the turning section facing the dense phase layer. The secondary air is introduced into the dense phase layer through the secondary air branch to prevent the problems of excessive concentration of coal powder in the dense phase layer, deposition in the circulation cavity and incomplete combustion.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is further described below in conjunction with the accompanying drawings and implementation modes.

FIG1 is a schematic structural diagram of a combustion system provided in an embodiment of the present application;

FIG2 is a schematic structural diagram of another combustion system provided in an embodiment of the present application;

FIG3 is a flowchart of the steps of a method for using a boiler provided in an embodiment of the present application.

Description of reference numerals:

1. Primary air and powder pipeline;

2. Separator;

3. Turning entrance section;

4. Multi-layer thick-thin burner; 40. Primary air nozzle; 41. Dense phase layer; 42. Dilute phase layer; 43. Very dilute phase layer;

5. Baffle;

6. Exhaust gas recirculation branch pipe;

7. The first switch valve;

8. First safety valve;

9. Exhaust gas guide branch pipe; 90. Exhaust gas direct combustion nozzle; 91. Second switch valve;

10. Mixer;

11. Secondary air main road;

12. Secondary air nozzle;

13. Secondary air branch;

14. Second safety valve;

15. The third switch valve;

16. The first exhaust gas outlet valve;

17. Second exhaust gas outlet valve.

Detailed ways

The technical solution of the present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention. After reading the present invention, various equivalent forms of modifications to the present invention by those skilled in the art all fall within the scope defined by the claims attached to this application.

It should be noted that when an element is referred to as being "disposed on" another element, it may be directly on the other element or there may be a central element. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be a central element at the same time. The terms "vertical", "horizontal", "upper", "lower", "left", "right" and similar expressions used herein are for illustrative purposes only and are not intended to be the only implementation method.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art to which the present application belongs. The terms used herein in the specification of the present application are only for the purpose of describing specific embodiments and are not intended to limit the present application. The term "and/or" used herein includes any and all combinations of one or more of the related listed items.

Please refer to Figures 1 and 2 for a comprehensive description of a combustion system provided in the embodiments of the present application specification. The combustion system can be applied to the combustion field of a gas-solid two-phase mixed fluid, such as the field of coal powder combustion. Of course, the combustion system can also be applied to other gas-solid two-phase mixed fluid scenarios. In the present application specification, coal powder combustion is used as an example for illustration, and other scenarios can be referred to by analogy. The present application will not give examples one by one here.

The combustion system provided in the present application mainly includes: a separator 2, a primary air powder pipeline 1, an exhaust gas utilization pipeline and a multi-layer thick-lean burner 4.

In this embodiment, the separator 2 may include: a separation body having an inlet connected to the primary air-powder pipeline 1 , a first outlet connected to the multi-layered dense-lean burner 4 , and a second outlet capable of connecting to the exhaust gas utilization pipeline.

Specifically, the separator 2 may include: a cyclone separator 2, a louver separator 2, a trough separator 2, etc. Among them, the cyclone separator 2 has a very good separation effect, and can even completely separate the gas-solid two-phase flow. Since in the present application, it is not necessary to completely separate the gas-solid two-phase, the cyclone separator 2 with too good separation effect is not suitable for the present invention. The separation effect of the louver separator 2 is worse than that of the cyclone separator 2. After the gas-solid two-phase flow (i.e., coal powder and wind) enters the louver separator 2, it can be divided into different fluids according to the different solid particle contents, for example, it can be divided into two fluids, a dilute phase and a dense phase; and the dense phase is not too concentrated (the solid particle content is too high). Because too much concentration will cause the coal powder to lack oxygen and be difficult to burn. Preferably, the air volume ratio of the first outlet and the second outlet of the separator 2 can be adjusted as needed, so as to better use the unit load regulation requirements.

In this embodiment, one end of the primary air powder pipeline 1 is connected to the inlet of the separator 2 , and the other end is connected to the outlet of the coal mill, so that the primary air powder flowing out of the outlet of the coal mill is introduced into the separator 2 .

In this embodiment, the multi-layer thick-lean burner 4 may include: a connecting mechanism with a gas-solid separation function. One end of the connecting mechanism is connected to the first outlet, and the other end of the connecting mechanism is connected to a plurality of isolated flow cavities arranged along the gravity direction, and an adjusting member at least partially located in the flow cavity, and the adjusting member can at least adjust the flow area of the flow cavity located at the top of the multi-layer thick-lean burner 4.

Among them, the multi-layer thick-lean burner 4 can be connected to the first outlet of the separator 2 through a connecting mechanism with a gas-solid separation function, so that the gas-solid fluid flowing out of the first outlet of the separator 2 is layered according to different solid particle concentrations to be introduced into the corresponding flow cavities. For example, a turning inlet section 3 is set between the first outlet of the separator 2 and the inlet of the multi-layer thick-lean burner 4, and the flow cavity of the separator 2 extends in the horizontal direction as a whole, and a predetermined angle is formed between the overall extension direction of the turning inlet section 3 and the horizontal direction. Among them, the size of the predetermined angle can be designed accordingly according to specific usage requirements. On the whole, by setting the turning inlet section 3 with a predetermined angle, it is used to ensure that when entering each isolated flow cavity, the proportion of coal powder and wind increases successively along the gravity direction, and prevent the coal powder concentration in the flow cavity at a lower position from being too high.

The specific number of layers (i.e., the number of circulation cavities) of the multi-layer thick-thin burner 4 can be adaptively designed according to actual use requirements, for example, it can be 2 layers, 3 layers or even more layers. As shown in Figure 1 or Figure 2, the multi-layer thick-thin burner 4 can include: a very dilute phase layer 43, a dilute phase layer 42, and a dense phase layer 41 along the gravity direction. The inlet end of each layer of the circulation cavity is connected to the turning inlet section 3, which is used to receive the wind and powder separated by the turning inlet section 3. The outlet end is provided with a primary air nozzle 40, which is used to spray the wind and powder into the furnace for combustion.

In this embodiment, an adjusting member may be provided in at least part of the flow cavity of the multi-layer thick-lean burner 4. The adjusting member can at least adjust the flow area of the flow cavity of the multi-layer thick-lean burner 4 located at the top. For example, as shown in Figure 1 or Figure 2, the adjusting member can be movably arranged in the extremely rare phase layer 43. Of course, in other embodiments, it is not excluded that the adjusting member can be movably arranged in the extremely rare phase layer 43 and the rare phase layer 42 at the same time. Specifically, the adjusting member can be in the form of a baffle 5. The baffle 5 can be movably arranged in the flow cavity, thereby changing the flow area of the flow cavity. Specifically, the multi-layer thick-lean burner 4 can also be provided with a driving mechanism for driving the baffle 5. When the number of flow cavities needs to be reduced, the position of the baffle 5 can be changed by the driving mechanism, thereby achieving the blocking of the flow cavity. Among them, the driving mechanism can drive the baffle 5 by rotating or moving. The specific structure and driving method of the driving mechanism are not specifically limited in this application.

In this embodiment, the exhaust gas utilization pipeline includes a first exhaust gas outlet valve 16 for controlling the on-off of the exhaust gas utilization pipeline. When the first control valve is in an open state, part of the air powder separated by the separator 2 flows through the exhaust gas utilization pipeline and can flow to the furnace.

The airflow separated by the separator 2 is called exhaust gas. This part of the airflow is the air powder with very low coal powder content obtained after the primary air powder is separated by the separator 2. When the air powder with very low coal powder content is separated from the primary air powder, the proportion of air volume can be effectively reduced. And since this method does not directly reduce the circulation area of the air powder, it will not increase the flow rate of the air powder.

In one embodiment, the exhaust gas utilization pipeline may include a main exhaust gas pipe section connected to the second outlet of the separator 2. The first exhaust gas outlet valve 16 is arranged on the main exhaust gas pipe section to control the opening and closing of the main exhaust gas pipe section. Along the exhaust gas flow path, the exhaust gas utilization pipeline also includes at least one branch pipe, which can directly or indirectly introduce the exhaust gas into the furnace.

In the embodiment where the branch pipe indirectly introduces the exhaust gas into the furnace, the branch pipe includes an exhaust gas recirculation branch pipe 6 connected to the main pipe section. One end of the exhaust gas recirculation branch pipe 6 is connected to the main pipe section, and the other end is connected to the flow cavity of the multi-layer rich-lean burner 4 located at the top.

When the unit is at low load, a portion of the exhaust gas separated by the separator 2 returns to the flow cavity located at the top through the exhaust gas recirculation branch pipe 6, for example, the very dilute phase layer 43 in Figure 1 or 2, to purge the very dilute phase layer 43 and reburn the exhaust gas. At the same time, the ejected exhaust gas can exert a force on the flame ejected from the adjacent area (for example, the primary air nozzle 40 of the dense phase layer 41 and the dilute phase layer 42), thereby preventing the flame in the adjacent area from backfired to the very dilute phase layer 43.

Two valves are arranged on the exhaust gas recirculation pipeline. Among them, the valve close to the multi-layer thick-lean burner 4 is the first safety valve 8, and the first safety valve 8 can specifically be a stop valve or a check valve, which is used to cut off the fluid and even prevent the backflow of coal powder. The valve far away from the multi-layer thick-lean burner 4 is the first switch valve 7, which is mainly used to control the on-off of the exhaust gas recirculation pipeline. Of course, the specific form of the first switch valve 7 is not specifically limited in this application. For example, it can be an electrical switch valve, which can be automatically opened or closed after receiving an electric control signal. In addition, it can also be a manually adjusted switch valve. By operating its operating part, the flow area of the exhaust gas recirculation pipeline can be adjusted.

Among them, for the implementation method in which the branch pipe directly guides the exhaust gas into the furnace, the branch pipe includes an exhaust gas guide branch pipe 9 connected to the main pipe section. One section of the exhaust gas guide branch pipe 9 is connected to the main pipe section, and the other end is an exhaust gas direct combustion nozzle 90 for guiding the exhaust gas to the furnace. A second switch valve 91 is provided on the exhaust gas guide branch pipe 9, and the second switch valve 91 is mainly used to control the on and off of the exhaust gas guide branch pipe 9. Specifically, the form of the second switch valve 91 can refer to the form of the above-mentioned first switch valve 7, and the present application does not make a specific limitation here.

In one embodiment, the combustion system further includes: a secondary air main path 11 and a secondary air branch path 13 connected to the secondary air main path 11. The outlet end of the secondary air main path 11 is a secondary air nozzle 12; one end of the secondary air branch path 13 is connected to the secondary air main path 11, and the other end is at least connected to the flow cavity of the multi-layer thick-lean burner 4 located at the bottom.

Two valves may also be provided on the secondary air branch 13. Among them, the valve close to the multi-layer thick-lean burner 4 is the second safety valve 14, and the second safety valve 14 may specifically be a stop valve or a check valve, which is used to cut off the fluid and even prevent the backflow of coal powder. The valve away from the multi-layer thick-lean burner 4 is the third switch valve 15, which is mainly used to control the on-off of the secondary air branch 13. Of course, the specific form of the third switch valve 15 is not specifically limited in this application. For example, it may be an electrical switch valve, which can be automatically opened or closed after receiving an electric control signal. In addition, it may also be a manually adjusted switch valve. By operating its operating part, the flow area of the exhaust gas recirculation pipeline can be adjusted.

Preferably, the third switch valve 15 is a regulating valve with adjustable opening. In addition to the secondary air flowing to the secondary air nozzle 12 through the secondary air main path 11, the secondary air branch path 13 can be used to direct the secondary air to the regulating valve near the circulation cavity (e.g., dense phase layer 41) with a high coal powder concentration of the multi-layer dense-lean burner 4. By adjusting the opening and closing state or the opening of the regulating valve, a certain flow of air is introduced into the corresponding circulation cavity (e.g., dense phase layer 41), thereby adjusting the coal powder concentration of the dense phase layer 41 to prevent the coal powder concentration of the dense phase layer 41 from being too high, depositing in the circulation cavity, and incomplete combustion.

As shown in FIG2 , in one embodiment, a mixer 10 is provided in the secondary air main path 11. The end of the secondary air main path 11 is a secondary air nozzle 12, and an extension section extending to the mixer 10 is provided at one end of the main pipe section away from the separator 2, and a second exhaust gas outlet valve 17 is provided on the extension section. When the second exhaust gas outlet valve 17 is opened, the exhaust gas entering the mixer 10 from the main pipe section and the extension section is mixed with the wind energy entering the mixer 10 from the secondary air main path 11, and then sprayed toward the furnace through the secondary air nozzle 12 of the secondary air main path 11.

In this embodiment, the separator 2 separates the primary air powder, and the exhaust gas in the extremely dilute phase separated when concentrating the coal powder has three flow directions, one of which is to the exhaust gas recirculation branch pipe 6 and returns to the extremely dilute phase layer 43 downstream of the adjustment baffle 5 of the multi-layer thick-thin burner 4, one of which is to the exhaust gas direct combustion nozzle 90 through the exhaust gas guide branch pipe 9, and one of which is to mix with the secondary air through the mixer 10 and flow to the secondary air nozzle 12. The exhaust gas extension branch where the exhaust gas guide branch pipe 9 and the mixer 10 are located are two different exhaust gas flow paths. When in use, one can be selected to open according to needs to transport excess exhaust gas to the furnace.

In one embodiment, the multi-layer rich-lean burner 4 includes an extremely rarefied phase layer 43 at the top and a rarefied phase layer 42 below the extremely rarefied phase layer 43, and a separator is provided between the extremely rarefied phase layer 43 and the rarefied phase layer 42 at the junction near the nozzle.

In this embodiment, taking the multi-layer thick-lean burner 4 as a three-layer thick-lean burner as an example, a separator can be provided at the junction of the outlets of the extremely dilute phase layer 43 and the dilute phase layer 42. The separator is mainly used to prevent the flames ejected from the dense phase and the dilute phase combustion from rushing to the extremely dilute phase nozzle and burning the extremely dilute phase nozzle. In addition, the separator can also be used to prevent the flue gas from flowing back and improve the stable combustion performance. Specifically, the separator can be in the form of a Y-shaped separation cone. Of course, the separator can also be in other forms, and the present application does not make specific limitations here.

When in use, the primary air powder at the outlet of the coal mill flows to the separator 2 through the primary air powder pipeline 1, and the air powder with very low coal powder content is separated as exhaust gas. When the air powder with very low coal powder content is separated from the primary air powder, the proportion of air volume can be effectively reduced. And since this method does not directly reduce the circulation area of the air powder, it will not increase the flow rate of the air powder and will not affect the stable combustion performance of the multi-layer thick and thin burner 4.

The pulverized coal airflow concentrated by the separator 2 flows through the turning inlet section 3 with a certain inclination, and is respectively led to the flow chambers corresponding to the multi-layer thick-thin separation burners according to different concentrations. Among them, an adjusting member (baffle 5) for adjusting the flow area is installed in the extremely dilute phase layer 43 of the multi-layer thick-thin burner 4, which is used to adjust the flow area at low load, so as to maintain the flow rate of the gas-solid two-phase flow at the burner nozzle and the stiffness of the flame, thereby improving the boiler's stable combustion ability and combustion effect. In addition, in the extremely dilute phase layer 43 of the multi-layer dense-lean burner 4, there is also an exhaust gas guide branch pipe 9 located downstream of the baffle 5; when the unit is under low load, a portion of the exhaust gas separated by the separator 2 returns to the flow cavity located at the top through the exhaust gas recycling branch pipe 6, for example, the extremely dilute phase layer 43 as shown in Figure 1 or Figure 2, which is used to purge the extremely dilute phase layer 43 and reburn the exhaust gas. At the same time, the ejected exhaust gas can exert a force on the flame ejected from the adjacent area (for example, the primary air nozzle 40 of the dense phase layer 41 and the dilute phase layer 42), so as to prevent the flame in the adjacent area from backfired to the extremely dilute phase layer 43.

A secondary air branch 13 inlet is also provided on the wall of the turning section facing the dense phase layer 41. The secondary air branch 13 introduces the secondary air into the dense phase layer 41 to prevent the problems of excessive concentration of pulverized coal in the dense phase layer 41, deposition in the circulation cavity, and incomplete combustion.

Based on the combustion system provided in the above-mentioned embodiments of the present application, the present application also provides a boiler provided with the above-mentioned combustion system. The boiler is also provided with a plurality of coal mills. For each coal mill, it can be provided with the combustion system of the above-mentioned embodiment. In addition, the combustion system can also be provided for several of the coal mills. The specific configuration of the combustion system can be selected and set accordingly according to the load conditions of the unit, and the present application does not make specific limitations here.

The boiler provided with the combustion system provided in the present application can better adapt to the low-load operating conditions of the unit, thereby expanding the peak-shaving depth of the boiler load.

When the unit load is reduced, the output of the coal mill can be reduced first; in addition, the multi-layer thick-lean burner 4 can passively achieve a reduction in ignition heat demand, an increase in volatile matter concentration, and an enhancement of local heat release intensity in a small range, thereby passively achieving stable combustion of the burner; further, the baffle 5 of the multi-layer thick-lean burner 4 can be adjusted, the opening of the multi-layer thick-lean burner 4 can be adjusted, and the separator 2 and the exhaust gas can be used to separate a part of the excess primary air through the exhaust gas recycling branch 6, the exhaust gas guide branch 9, and the mixer 10, so as to continue to cooperate with the load reduction demand of reducing the amount of coal burned; when the unit load continues to decrease, the fuel regulation requirements under low load can be achieved by reducing the number of coal mills used and the corresponding number of burner layers used.

On the whole, the combustion system can, on the one hand, passively adapt to the reduction of load in a small range through the multi-layer rich-lean burners 4, and on the other hand, actively adjust the stable combustion performance of the combustion system through the baffle 5 and the exhaust gas recirculation branch 6, the exhaust gas guide branch 9 and the mixer 10 of the multi-layer rich-lean burners 4, thereby adapting to the reduction of unit load at both active and passive levels.

As shown in FIG3 , based on the boiler provided in the embodiment of the present application, the present application further provides a method for using the boiler, which may include the following steps:

Step S10: When the power generation load is higher than the first preset value, the output of the grinding machine and the air volume of the fan are adjusted, and the input of the fuel amount and the flow rates of the primary air and the secondary air are adjusted to match the unit load;

Step S12: when the power generation load is lower than a second preset value, the adjustment member of the thick-thin multilayer burner and/or the exhaust gas outlet ratio of the first outlet and the second outlet of the separator 2 are adjusted by adjusting the output of the grinding machine, and the first preset value is greater than the second preset value;

Step S14: When the power generation load is lower than a third preset value, adjust the number of coal mills in use, the number of burner layers and the corresponding proportions of primary air and secondary air flow to match the unit load, and the third preset value is less than the second preset value.

In this embodiment, when the power generation load is high, higher than the first preset value, the output of each coal mill can be adjusted to adjust the input of the fuel amount. Specifically, the first preset value can be determined comprehensively based on the adjustment capacity of the coal mill output, the lower limit of the primary wind speed, etc., and the value is not specifically limited in this application. For example, the first preset value can be 70%.

In this embodiment, when the power generation load is reduced to a certain level, for example, higher than the first preset value and higher than the second preset value, and has affected the lower limit of the primary wind speed, the variable load adaptive adjustment can be performed by adjusting the baffle 5 of the extremely dilute phase of the dense and thin multi-layer burner and adjusting the exhaust gas outlet ratio of the first outlet and the second outlet of the separator 2; the specific numerical value of the second preset value can be comprehensively determined according to the specific scenario.

In this embodiment, when the power generation load is lower than the second preset value, for example, when it is reduced to near the lower limit of the use of the multi-layer thick-lean burner 4, variable load regulation is performed by adjusting the number of coal mills used and the number of burner layers.

On the whole, the above three methods can be used to adjust the power generation load to different conditions, which can better adapt to the low-load conditions of the unit, thereby expanding the peak load regulation depth of the boiler load.

It should be noted that, in the description of this application, the terms "first", "second", etc. are only used for descriptive purposes and to distinguish similar objects. There is no order of precedence between the two, and they cannot be understood as indicating or implying relative importance. In addition, in the description of this application, unless otherwise specified, the meaning of "plurality" is two or more.

The above-mentioned various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referenced to each other. Each embodiment focuses on the differences from other embodiments.

The above are only several embodiments of the present invention. Although the embodiments disclosed by the present invention are as above, the above contents are only embodiments adopted for facilitating the understanding of the present invention and are not used to limit the present invention. Any technician in the technical field to which the present invention belongs can make any modification and change in the form and details of the embodiments without departing from the spirit and scope disclosed by the present invention, but the patent protection scope of the present invention shall still be subject to the scope defined by the attached claims.

Claims (7)

1. A combustion system, characterized by comprising: a separator, a primary air and powder pipeline, an exhaust gas utilization pipeline and a multi-layer thick and thin burner; The separator comprises: a separation body, the separation body is provided with an inlet connected to the primary air-powder pipeline, a first outlet connected to the multi-layer thick-lean burner, and a second outlet capable of being connected to the exhaust gas utilization pipeline; The multi-layer thick-lean burner comprises: a connecting mechanism with a gas-solid separation function, one end of the connecting mechanism is connected to the first outlet, a plurality of isolated flow cavities are connected to the other end of the connecting mechanism and are arranged along the gravity direction, and an adjusting member at least partially located in the flow cavity, the adjusting member can at least adjust the flow area of the flow cavity located at the top of the multi-layer thick-lean burner; The exhaust gas utilization pipeline includes a first exhaust gas outlet valve for controlling the on-off of the exhaust gas utilization pipeline. When the first exhaust gas outlet valve is in an open state, part of the air powder separated by the separator flows through the exhaust gas utilization pipeline and can flow to the furnace; The exhaust gas utilization pipeline includes a main pipe section connected to the second outlet of the separator, the first exhaust gas outlet valve is arranged on the main pipe section, and along the exhaust gas flow path, the exhaust gas utilization pipeline also includes at least one branch pipe, and the branch pipe can directly or indirectly introduce the exhaust gas into the furnace; The combustion system further comprises a secondary air main path and a secondary air branch path connected to the secondary air main path, wherein the outlet end of the secondary air main path is a secondary air nozzle; One end of the secondary air branch is connected to the secondary air main path, and the other end is at least connected to the flow cavity located at the bottom of the multi-layer thick-lean burner; A mixer is provided in the secondary air main path, the end of the secondary air main path is a secondary air nozzle, an extension section extending to the mixer is provided at one end of the main pipe section away from the separator, and a second exhaust gas outlet valve is provided on the extension section. When the second exhaust gas outlet valve is opened, the exhaust gas entering the mixer from the main pipe section and the extension section is mixed with the wind entering the mixer from the secondary air main path, and then sprayed toward the furnace through the secondary air nozzle of the secondary air main path; The multi-layer rich-lean burner includes an extremely dilute phase layer located at the top and a dilute phase layer located below the extremely dilute phase layer. A separation piece is provided between the extremely dilute phase layer and the dilute phase layer at a junction close to the nozzle. 2. The combustion system according to claim 1 is characterized in that the branch pipe includes a spent gas recirculation branch pipe connected to the main pipe section, one end of the spent gas recirculation branch pipe is connected to the main pipe section, and the other end is connected to the flow cavity located at the top of the multi-layer rich-lean burner, and the connection position between the spent gas recirculation branch pipe and the flow cavity is located downstream of the regulating member. 3. The combustion system as described in claim 1 is characterized in that the branch pipe includes an exhaust gas guide branch pipe connected to the main pipe section, one end of the exhaust gas guide branch pipe is connected to the main pipe section, and the other end is an exhaust gas direct combustion nozzle for guiding the exhaust gas to the furnace. 4. The combustion system as described in claim 1 is characterized in that the connecting mechanism is a turning inlet section arranged between the first outlet of the separator and the inlet of the multi-layer rich-lean burner, the flow cavity of the separator extends in a horizontal direction as a whole, and a predetermined angle is formed between the overall extension direction of the turning inlet section and the horizontal direction. 5. The combustion system according to claim 2, characterized in that a first safety valve is provided on the exhaust gas recirculation branch pipe near the multi-layer rich-lean burner, and a first switch valve is provided between the first safety valve and the main pipe section. 6. A boiler, characterized in that it comprises: a plurality of coal mills, at least one outlet of which is connected to a combustion system as claimed in any one of claims 1 to 5. 7. A method for using the boiler according to claim 6, characterized by comprising: When the power generation load is higher than the first preset value, the output of the grinding machine and the air volume of the fan are adjusted to adjust the input of the fuel amount and the flow rates of the primary air and the secondary air to match the unit load; When the power generation load is higher than the second preset value and lower than the first preset value, the output of the grinding mill is adjusted, and the exhaust gas flow rate ratio of the first outlet and the second outlet of the regulating member of the thick and thin multi-layer burner and the separator is adjusted to match the unit load; When the power generation load is lower than the second preset value, the number of coal mills in use, the number of burner layers and the corresponding proportions of primary air and secondary air flow are adjusted to match the unit load.