WO2017212256A1

WO2017212256A1 - Burner

Info

Publication number: WO2017212256A1
Application number: PCT/GB2017/051644
Authority: WO
Inventors: Ik Soo Kim
Original assignee: Doosan Babcock Limited
Priority date: 2016-06-08
Filing date: 2017-06-07
Publication date: 2017-12-14
Also published as: KR20190025901A; GB201610008D0; GB2551167A; EP3469261A1

Abstract

A primary conduit for a burner is described having a primary conduit outlet; the primary conduit defining a primary conduit flow channel extending to the primary conduit outlet; wherein the primary conduit includes a primary conduit end pipe (3) proximal the primary conduit outlet defining a flow channel having a linear flow direction from a first inlet end to a second outlet end corresponding to the primary conduit outlet and a primary conduit elbow pipe (1) upstream of and in fluid communication with the primary conduit end portion defining a flow channel having a deviating flow direction from a first inlet end to a second outlet end corresponding to the inlet end of the primary conduit end portion. The primary conduit has in its flow channel a particle concentrator (5) comprising an elongate annular ring formation with an outer diameter less than an inner diameter of the primary conduit and disposed axially relative to the primary conduit end pipe and in the vicinity of the junction between the primary conduit elbow pipe and the primary conduit end pipe so as there to divide the primary conduit flow channel into concentric outer and inner flow channels. A burner is described incorporating such a primary conduit.

Description

BURNER

The invention relates to a burner, and in particular a burner for the combustion of particulate carbonaceous fuel. In the preferred case the invention relates to a pulverous fuel burner such as a pulverous coal fired burner. For example the invention relates to a burner for use in a power generation apparatus and to a power generation apparatus including one or more such burners. At its most general concept, the invention relates to a primary air conduit arrangement for such a burner and to a burner incorporating the same.

Introduction

In general terms, a burner for combustion of particulate carbonaceous fuel may comprise a number of components, which may include:

· a primary conduit to supply the pulverous fuel and a conveying gas which may be a comburant gas (often known as "primary" air) to the burner outlet;

• a number of channels arranged for example concentrically around the primary conduit pulverous fuel supply, through which comburant gas and other gas may be supplied to support/ control/ modify combustion at the burner outlet; in a burner for the combustion of particulate carbonaceous fuel there will typically be two or more channels for the combustion air or other comburant gas and these are often known as "secondary" air, "tertiary" air, etc;

• a core conduit or core tube disposed axially centrally within an annular primary conduit to supply for example further comburant gas to support/ control/ modify combustion at the burner outlet, and/ or to locate supplementary equipment, such as igniters, light-up burners, flame monitoring sensors, etc;

• devices to induce a swirling motion into the gas flows for example in the secondary and tertiary (etc.) channels;

• devices to stabilise the flame, often placed on the end of the fuel supply pipe and sometimes known as the "flame-holder";

• devices placed inside the fuel supply pipe to control the fuel distribution at the outlet of that pipe; • supplementary equipment, such as igniters, light-up burners, flame monitoring sensors, etc., optionally installed in a separate tube, which may be located centrally within the fuel pipe where it is known as the "core" tube; the core tube may have its own air or other gas supply; alternatively supplementary equipment may be installed in other locations in the burner or close by.

Where "air" is used herein both with reference to the prior art and with reference to the invention the skilled person will readily appreciate that other oxygen containing comburant gases and mixtures may be substituted in the familiar way for example for oxyfuel firing including a comburant gas having a reduced nitrogen content relative to air, for example comprising mixtures of pure oxygen and/ or recycled flue gas and/ or air. References to a comburant gas will be understood to include mixtures of gases including gases capable of supporting combustion and other gases.

The present invention relates to a primary conduit for a burner as above described, adapted to supply pulverous fuel and a conveying gas to a primary conduit outlet corresponding to a burner outlet, which conveying gas is typically in use a comburant gas (often known as "primary" air); and to a burner incorporating the same.

The present invention relates to a primary conduit having a primary conduit inlet disposed to receive a supply of combustible pulverous fuel and a supply of comburant gas and a primary conduit outlet in the vicinity of which combustion of the fuel is supported during use; the primary conduit defining a flow channel extending from the primary conduit inlet to the primary conduit outlet to convey a mixture of fuel and a gas such as a comburant gas in use. The primary conduit is disposed annularly around a core conduit and may be provided with secondary and tertiary channels as above described. It is known by those knowledgeable in the art that there are a number of variant burner designs available for the combustion of particulate carbonaceous fuel. Implicit in the design of any burner is the requirement to ensure that there must be sufficient comburant gas to supply sufficient oxidant in any oxidant/ fuel mix and an even distribution of fuel in the oxidant to support the consistent combustion of the fuel and to maintain the stability of the flame. Alternative arrangements of burner design which are effective in creating an even distribution of fuel in the oxidant to support the consistent combustion of the fuel and to maintain the stability of the flame are desirable.

Summary of the Invention

According to the invention there is provided a primary conduit for a burner having a primary conduit outlet in the vicinity of which combustion of the fuel is supported during use; the primary conduit defining a primary conduit flow channel extending to the primary conduit outlet to receive and convey a mixture of fuel and a gas such as a comburant gas in use;

wherein the primary conduit includes a primary conduit end pipe proximal the primary conduit outlet defining a flow channel having a linear flow direction from a first inlet end to a second outlet end corresponding to the primary conduit outlet and a primary conduit elbow pipe upstream of and in fluid communication with the primary conduit end pipe and defining a flow channel having a deviating flow direction from a first inlet end to a second outlet end corresponding to the inlet end of the primary conduit end pipe;

wherein there is within the primary conduit flow channel:

a particle concentrator comprising an elongate annular ring formation with an outer diameter less than an inner diameter of the primary conduit and disposed axially relative to the primary conduit end pipe and in the vicinity of the junction between the primary conduit elbow pipe and the primary conduit end pipe so as there to divide the primary conduit flow channel into concentric outer and inner flow channels.

The change of direction as the fuel and gas mix passes through the elbow portion may create undesirable flow concentration effects. The invention seeks to mitigate these as pulverous fuel flows into the end pipe and to the outlet by creating pulverous fuel and comburant flow distributions and concentrations that improve combustion performance.

It achieves this by providing at least a particle concentrator as above described within the primary conduit. The particle concentrator is configured to control pulverous fuel flow profiles at the elbow.

In particular in an embodiment the particle concentrator is configured to generate flow concentrated towards the centre. Advantageously to effect this, the particle concentrator may include radially projecting formations that project radially into and divert flow within an axial flow channel away from an axial direction and urge the pulverous fuel flow towards the centre. In particular in an embodiment the particle concentrator is configured to generate rotational flow. Advantageously to effect this, the particle concentrator may be partly closed, in that that one, other or both of the concentric outer and inner flow channels are occluded for an arcuate portion of the annular flow channel. For example the particle concentrator may be closed on one side. This imparts a circular flow motion to the pulverous fuel flow.

The two motions combine to distribute pulverous fuel more evenly. The flow concentrates towards the core air pipe with higher concentrations on the low side. Advantageously, the particle concentrator is located in the primary flow channel generally at the point of communication between the primary conduit end pipe and the primary conduit elbow pipe and for example extends rearwardly from an inlet region of the primary conduit end pipe into the primary conduit elbow pipe for example to cover between 15 degrees and 45 degrees of the change in flow direction in the same.

In a possible embodiment the primary conduit end pipe is disposed coaxially about a core conduit, the core conduit defining a core flow channel for conveying a further gas flow such as a further comburant gas flow to a core conduit outlet, and so disposed that the primary conduit end pipe defines an annular flow channel about the core conduit.

Other structures adapted further to modify the flow may be provided in the primary conduit, in particular downstream of the particle concentrator. Optionally a first particle diffuser may be provided comprising an axially mounted bullet formation, which bullet formation includes progressively in a downstream flow direction a first wall portion that flares in radially outwardly extending manner to provide a progressively increasing occlusion of the primary conduit flow channel, and a second wall portion that taper in radially inwardly extending manner to provide a progressively decreasing occlusion of the primary conduit flow channel.

This provides the advantage that the first particle diffuser bullet formation presents an occlusion that interacts with the circular flow motion effected by the particle concentrator to reduce the tangential motion of the more direct central flow streams and stabilise the distribution at the burner exit.

Optionally the first particle diffuser may include an untapered cylindrical third wall portion intermediate between the first and second wall portions.

Optionally the first particle diffuser may be mounted so as to be translatable axially to and fro along the burner. This provides the advantage of enabling control in use of the distribution of particles in the pulverous flow. In an embodiment comprising a core conduit, the first particle diffuser may be mounted about the core conduit for example on an outer surface of the core conduit. The first particle diffuser may be mounted to be slideably axially along the core conduit and thus axially to and fro along the burner. Optionally a particle deflector may be provided downstream of the particle concentrator and upstream of the first and/ or further particle diffuser where present, comprising an annular plate formation having an outer perimeter mounted inside the primary conduit end pipe such as to extend around an inner perimeter of the primary conduit end pipe and a radial wall portion extending into and partially occluding the primary conduit flow channel. This provides the advantage that the deflector interacts with flow from the elbow concentrator, helping to keep the particles in the pulverous flow dispersed.

Optionally a further particle diffuser may be provided to complement the effect of the bullet formation and comprising an elongate annular ring formation having an outer perimeter mounted inside the primary conduit end pipe such as to extend around an inner perimeter of the primary conduit end pipe, an defining progressively in a downstream flow direction a first wall portion that tapers in radially inwardly extending manner to provide a progressively increasing occlusion of the primary conduit flow channel, and a second wall portion that flares in radially outwardly extending manner to provide a progressively decreasing occlusion of the primary conduit flow channel. Optionally the further particle diffuser may include an untapered cylindrical third wall portion intermediate between the first and second wall portions. This provides the advantage of combining with the first particle diffuser and complementing its action in stabilising the distribution of particles in the pulverous flow at the burner exit.

The invention seeks to create pulverous fuel and comburant flow distributions and concentrations at the primary conduit outlet that improve combustion performance. It achieves this in the preferred case by providing in the primary conduit, successively in a downstream flow direction, a particle concentrator, and one or more of a particle deflector, a first particle diffuser and a further particle diffuser.

The primary conduit to which the principles of the invention applies otherwise typically comprises in familiar manner a continuous flow channel for receiving a supply of a gas such as a comburant gas and a supply of combustible pulverous fuel and conveying the same to a combustion site of a burner, which has at least a primary conduit end pipe extending along a burner axis to the burner outlet to define a linear flow direction parallel to the burner axis, and an elbow portion immediately upstream of the primary conduit end pipe to define a deviating flow direction changing in direction from an upstream flow direction upstream of the elbow portion to a downstream flow direction downstream of the elbow portion and in the end pipe.

A core conduit optionally extends through the end pipe coaxially with the end pipe on a burner axis so that an outer surface of the core conduit and an inner surface of the end pipe define an annular primary flow channel, and so that an inner surface of the core conduit defines a fluidly isolated core flow channel, in generally familiar manner. The primary conduit end pipe preferably has a length at least three times its transverse extent and in the typical case where the primary conduit end pipe is cylindrical at least three times its diameter. The primary conduit more completely includes a primary conduit inlet disposed to receive a supply of combustible pulverous fuel and a supply of a gas such as a comburant gas and a primary conduit outlet in the vicinity of which combustion of the fuel is supported during use; the primary conduit defining a primary conduit flow channel extending from the primary conduit inlet to the primary conduit outlet to convey a mixture of fuel and a gas such as a comburant gas in use; with the primary conduit elbow pipe and end pipe to which the invention principally relates being located in a downstream portion of the primary conduit consecutively adjacent towards the outlet. The primary conduit is preferably in fluid communication at the primary conduit inlet with a supply of combustible pulverous fuel and a supply of comburant gas.

In a more complete aspect, a burner is provided having a primary conduit as above described.

In this more complete aspect there is provided a burner having a burner inlet for receiving a supply of combustible pulverous fuel and a supply of comburant gas and a burner outlet in the vicinity of which combustion of the fuel is supported during use; said burner comprising:

a primary conduit for conveying a mixture of fuel and gas such as comburant gas in accordance with the above described first aspect.

The burner thus includes a primary conduit with primary end pipe that defines a flow channel for conveying a mixture of fuel and gas such as comburant gas disposed about the core conduit, for example coaxially.

The invention is characterised by the provision within the primary conduit of, successively in a flow direction, a particle concentrator, optionally a particle deflector, a first particle diffuser and optionally a second particle diffuser as above described, to create pulverous fuel flow and comburant distributions and concentrations that improve combustion performance.

Subject to these basic features, a burner of the invention admits additional elements to supply material to the burner outlet and/ or to support combustion and flame stability at the burner outlet and/ or to facilitate mixing of one or more flow streams.

In particular optionally the burner may further comprise at least one further conduit, for example one or more secondary conduits and optionally one or more tertiary or higher order conduits comprising further flow channels for the supply of further gases such as further comburant gases to the combustion site at the burner outlet. Typically such a further conduit is disposed about the primary conduit, for example coaxially therewith. Optionally such a further conduit may comprise a swirl generation device to impart a swirl to the flow of gas therein.

A conduit may comprise any suitable arrangement defining and elongate flow channel. Each of the core, primary and if applicable secondary, tertiary and higher order conduits may comprise one or more elongate structures defining elongate flow channels. Where a conduit comprises plural flow channels they are for example generally parallel. In a familiar design, core, primary, secondary and tertiary or higher order conduits may be disposed about each other for example axially to define axial flow in a burner elongate direction. For example, a core conduit may be provided along a burner axis, a primary conduit may be disposed therearound, a secondary conduit disposed further therearound, and tertiary or higher order conduits disposed further therearound to define parallel axial flow channels in a burner elongate direction. Such an arrangement will be familiar.

Typically for example concentric and/ or coaxial tubes such as concentric and/ or coaxial cylinders may define annular flow regions or sectors thereof for the primary, secondary and higher order conduits. For example, annular flow channels comprising single or plural annular sectors may make up the primary flow, secondary flow and tertiary flow as desired.

Preferably, the burner of the invention is adapted for the combustion of particulate carbonaceous fuel and in the preferred case is a pulverous fuel burner. Preferably, the burner comprises a source of particulate carbonaceous fuel to supply fuel to a burner inlet, and in particular at least to an inlet of the primary conduit.

Preferably, the pulverous fuel burner is a pulverised coal burner, for example a burner for pulverised bituminous coal or dried pulverised lower rank coal. Consequently preferably the pulverous fuel is pulverised coal, for example pulverised bituminous coal or dried pulverised lower rank coal. Alternatively, the burner of the invention may be adapted for the combustion of pulverous carbonaceous fuel such as biomass, pulverous carbonaceous waste material, etc.

In a more complete aspect of the present invention, there is provided a combustion apparatus comprising:

a combustion chamber; and

at least one and preferably a plurality of burners as hereinbefore described located so as to define combustion sites within the combustion chamber.

Preferably the combustion apparatus comprises a boiler for generating steam.

Preferably the fuel used is particulate carbonaceous fuel and in the preferred case is a pulverous fuel, most preferably pulverised coal.

Brief Description of the Drawings

Preferred embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

Figure 1 shows an example of a possible embodiment of the invention;

Figure 2 shows further detail of the elbow arrangement of figure 1 ;

Figure 3 shows flow patterns in the embodiment of figure 1 ;

Figure 4 illustrates design/ dimension considerations for the embodiment of figure 1 ; Figure 5 shows an example of a possible more simple embodiment of the invention; Figure 6 illustrates design/ dimension considerations for the embodiment of figure 5. Detailed description of the preferred embodiment(s)

Figure 1 shows an example of a possible embodiment of the invention in which a primary air elbow pipe 1 leads via a primary air end pipe 3 to a burner outlet 7. The elbow pipe defines a 90 degree change in flow direction and the end pipe provides a linear axial flow direction to the burner outlet that has a length of at least three times its diameter. These together form the downstream part of a primary conduit disposed to convey a supply of combustible pulverous fuel and a supply of comburant gas to the primary conduit outlet in the vicinity of which combustion of the fuel is supported during use. The primary conduit is disposed annularly around a core conduit 5 for the supply of core air to the burner outlet. Other conduits (not shown) may be included in familiar manner in a complete burner design.

The primary flow channel defined by the primary conduit includes moving progressively downstream a half open concentrator 1 1 that extends into the downstream portion of the elbow pipe, an annular deflector 13, and paired diffusers 15 respectively in the form of an annular structure projecting inwardly from the inside surface of the primary air end pipe and a bullet structure projecting outwardly from the outside surface of the core conduit. Each is axially mounted. The deflector and diffusers are rotationally symmetric about that axis. The concentrator 1 1 is asymmetric in the sense that one side is closed so as to create a degree of asymmetric flow. The bullet structure may be mounted about the core conduit so as to be translatable axially along the burner. Figure 2 shows three different partially cut away illustrations of the elbow region where the concentrator 11 is located, the three illustrations together intended to illustrate the partially closed inner and outer flow channels defined by the concentrator by means of which a degree of circular flow motion is effected downstream of the concentrator.

The flow pattern is illustrated in Figure 3.

In flow zone A the elbow particle concentrator changes the elbow pipe bent flow to straight flow in the PA end pipe. The flow concentrates to the surfaces of the core air pipe. There is higher flow on the low side. The closure of one side of the elbow coal concentrator creates a rotational flow which is further illustrated in figure 5. At zone B the deflector deflects the flow/ particles and interacts with the flows from the concentrator to keep the particles dispersed. Zone C comprises a recirculation zone closed by the partial occlusion created by the diffuser arrangement at D to improve balance of small particle flow. At zone D the diffuser arrangement further modifies the flow and particle distribution.

Figure 4 considers suitable design parameters. Examples are as follows.

- 0.5 < (A+B)/F < 0.8, recommend 0.7 ~ 0.75

- 0.2 < A/(A+B) < 0.6, recommend 0.4 ~ 0.5

- 0.4 < B/(A+B) < 0.8, recommend 0.5 ~ 0.6

- 0.5 < C/F < 0.8, recommend 0.6 ~ 0.7

- 0.5 < D/F < 0.8, recommend 0.6 ~ 0.7

- 0.5 < E/F < 0.8, recommend 0.6 ~ 0.7

- Area "G"≥ Area "B"

The passage area of "G" between the deflector and Elbow concentrator should be larger than "B".

- Distance/location between deflector "C" and diffuser "D" & Έ" depends on the burner applications, but might be≥ 0.5 x PA

Diameter.

- Arrangement of diffusers "D" and Έ" is changeable.

- Elbow concentrator length "L", L ~ Elbow Bend R x (15°~45°) coverage, recommend 25°~30° coverage.

• i.e. L ~ Elbow Bend Radius x sin(25° or 30°) - Angles of a and Θ can be between 0°~90°, recommend 45°~60°.

- Diffuser slopes of D and E can have various angles and shape.

- PA pipe diameter≥ 3 x PA diameter.

Figure 5 shows an example of a possible more simple embodiment of the invention and Figure 6 illustrates design/ dimension considerations for the embodiment of figure 5.

In the simplified model flow modification is by an elbow concentrator 21 and bullet diffuser 23 only. Elbow Coal Concentrator generates concentrated to centre flow profiles, "flow 2". Having one side of the elbow coal concentrator blocked creates rotational motion "flow 1". Flow 2 is diverted outwardly by the bullet 23 in order to meet flow 1. Flow 1 distributes the coal more evenly further. The interception with flow 1 & 2 will reduce the tangential motion of flow 2 and stabilise at the exit. The bullet can travel along up and down to control coal distribution.

Figure 6 considers suitable design parameters. Examples are as follows.

Elbow concentrator's inner and outer area ratio = 40%/60%

Bullet blockage = 20% of Elbow Exit Area without the concentrator

Bullet location from the elbow exit = 1 x 0ΡΑ

Elbow bend radius is fixed to be equal to PA diameter, R_Ei_bow = 0ΡΑ • PA Length = 4 x 0ΡΑ

Elbow Concentrator Step, E = REi_bow 2 x Sin(25°)

These and other combinations and variations on the principles of the invention may be optimised to mitigate undesirable flow concentration effects due to the change of direction as the fuel and gas mix passes via the elbow pipe into the end pipe creating pulverous fuel and comburant flow distributions and concentrations at the end pipe outlet that improve combustion performance.

Claims

1. A primary conduit for a burner having a primary conduit outlet; the primary conduit defining a primary conduit flow channel extending to the primary conduit outlet;

wherein there is provided within the primary conduit flow channel a particle concentrator comprising an elongate annular ring formation with an outer diameter less than an inner diameter of the primary conduit and disposed axially relative to the primary conduit end pipe and in the vicinity of the junction between the primary conduit elbow pipe and the primary conduit end pipe so as there to divide the primary conduit flow channel into concentric outer and inner flow channels.

2. A primary conduit in accordance with claim 1 wherein the particle concentrator is configured to control pulverous fuel flow profiles at the elbow in use.

3. A primary conduit in accordance with claim 2 wherein the particle concentrator includes radially projecting formations that project radially into and divert flow within an axial flow channel away from an axial direction towards the centre.

4. A primary conduit in accordance with any preceding claim wherein the particle concentrator is configured to generate rotational flow.

5. A primary conduit in accordance with claim 4 wherein the concentric outer and inner flow channels of the particle concentrator are occluded for an arcuate portion of the annular flow channel.

A primary conduit in accordance with any preceding claim wherein the primary conduit end pipe is disposed coaxially about a core conduit, the core conduit defining a core flow channel for conveying a further gas flow such as a further comburant gas flow to a core conduit outlet, and so disposed that the primary conduit end pipe defines an annular flow channel about the core conduit.

A primary conduit in accordance with any preceding claim further comprising a first particle diffuser comprising an axially mounted bullet formation, which bullet formation includes progressively in a downstream flow direction a first wall portion that flares in radially outwardly extending manner to provide a progressively increasing occlusion of the primary conduit flow channel, and a second wall portion that taper in radially inwardly extending manner to provide a progressively decreasing occlusion of the primary conduit flow channel an untapered cylindrical third wall portion intermediate between the first and second wall portions.

A primary conduit in accordance with claim 7 wherein the first particle diffuser comprises an untapered cylindrical third wall portion intermediate between the first and second wall portions.

A primary conduit in accordance with claim 7 or claim 8 wherein the first particle diffuser is mounted so as to be translatable axially along the burner.

A primary conduit in accordance with any preceding claim further comprising a particle deflector downstream of the particle concentrator and upstream of the particle diffuser, comprising an annular plate formation having an outer perimeter mounted inside the primary conduit end pipe such as to extend around an inner perimeter of the primary conduit end pipe and a radial wall portion extending into and partially occluding the primary conduit flow channel.

A primary conduit in accordance with any preceding claim further comprising a further particle diffuser comprising an elongate annular ring formation having an outer perimeter mounted inside the primary conduit end pipe such as to extend around an inner perimeter of the primary conduit end pipe, an defining progressively in a downstream flow direction a first wall portion that tapers in radially inwardly extending manner to provide a progressively increasing occlusion of the primary conduit flow channel, and a second wall portion that flares in radially outwardly extending manner to provide a progressively decreasing occlusion of the primary conduit flow channel.

12. A primary conduit in accordance with any preceding claim wherein the primary conduit end pipe has a length at least three times its transverse extent.

13. A primary conduit in accordance with any preceding claim further comprising a primary conduit inlet disposed to receive a supply of combustible pulverous fuel and a supply of a gas such as a comburant gas; the primary conduit defining a primary conduit flow channel extending from the primary conduit inlet to the primary conduit outlet to convey the mixture of fuel and gas to the outlet, wherein the primary conduit elbow pipe and end pipe are located in a downstream portion of the primary conduit consecutively adjacent towards the outlet.

14. A primary conduit in accordance with claim 13 in fluid communication at the primary conduit inlet with a supply of combustible pulverous fuel and a supply of comburant gas.

15. A burner having a burner inlet for receiving a supply of combustible pulverous fuel and a supply of comburant gas and a burner outlet in the vicinity of which combustion of the fuel is supported during use; said burner comprising a primary conduit in accordance with any preceding claim.

16. A burner in accordance with claim 15 further comprising at least one further conduit, for example one or more secondary conduits and optionally one or more tertiary or higher order conduits comprising further flow channels for the supply of further gases such as further comburant gases to a combustion site at the burner outlet. A burner in accordance with claim 15 or 16 adapted for the combustion of particulate carbonaceous fuel such as pulverised coal.