JP2008045819A - Burner having central air jet port - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem related to delayed burning generated by a typical NO<SB>x</SB>burner, and to further reduce NO<SB>x</SB>emission in an industrial and public boiler. <P>SOLUTION: This invention provides a new burner device and a method for burning fossil fuel for commercial and industrial application. The new burner device achieves low NO<SB>x</SB>emission by supplying oxygen in the center of a burner flame in a mode of generating a fuel rich internal combustion region in the burner flame. A central jet burner includes an axial region concentrically surrounded by a first annular region, a feeder duct disposed in the radial direction between a part of the first annular region and the axial region to supply gas containing oxygen to the axial region, and a means for regulating the flow of gas passing through the feeder duct. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

The present invention relates generally to fuel burners, in particular, it creates a fuel rich internal combustion zone in the burner flame, so as to accelerate the fuel combustion, the supply of oxygen to the center of the burner flame directly, low NO _X emissions The present invention relates to a new and useful pulverized coal burner and a combustion method.

NO _X is a by-product generated during the combustion of coal and other fossil fuels. Environmental issues influence of the NO _X is, in several countries including the United States, and promote plant and laws of the NO _X emission regulations that require a significant reduction of the NO _X emissions from utility power plants. Current industrial methods and apparatus for reducing NO _X emissions have been successful in reducing the NO _X emissions than the level that has been discharged previously. However, further development beyond the progress of currently known methods and equipment is desired to maintain compliance with current NO _x emission regulations.

Various low NO _X burners are commercially available, the burner are widely used to ignite pulverized coal (PC) and other fossil fuels in a manner which reduces the NO _X compared to conventional burners . Examples of such burners are The Babcock & Wilcox Company's DRB-XCL® burner and DRB-4Z® burner. These and common ones to other low NO _X burner designs is an axial coal nozzle surrounded by multiple air space supplies secondary air (SA). During operation, the PC suspended in the primary air (PA) stream is passed through the axial coal nozzle as an axial jet with little or no radial deflection. It is injected into. The ignition of the PC is accomplished by swirling the SA (turning the SA), thereby causing hot gas recirculation along the incoming fuel jet.

In general, a very small amount of SA is supplied to an air nozzle that is very close to the coal nozzle and vortexed to a relatively greater extent than the SA that is supplied to other air regions to perform ignition. The The remaining SA from the burner is further mixed (radially) in the burner using fewer vortices so as to mix slowly into the burner flame, thereby providing a fuel rich condition at the root of the flame. It is introduced through the outside air area. Such a condition promotes the generation of hydrocarbons, which compete for available oxygen, destroy (disappear) NO _x , and / or fuel-bound nitrogen and nitrogen molecules to NO _x . It plays a role in suppressing oxidation.

NO _x emissions can be further reduced by two-stage (staged) combustion, where the burner is supplied with less stoichiometric oxygen for complete combustion. The result is a fuel rich environment in the burner flame. The fuel-rich environment suppresses the formation of NO _x by competing NO _x precursors with unburned fuel in an oxygen lean environment. Then, combustion, excess oxygen supplied to the boiler at a point burner upward excess fuel is more combustion at a lower temperature, away from the burner flame, eliminating the generation of thermal NO _x more when the combustion at a low temperature occurs Is done step by step. Doing stepwise also helps reduce the oxygen concentration during the combustion process, which suppresses the oxidation of fuel bound nitrogen (fuel NO _x ).

Oxygen for the two-stage combustion, in a system utilizing low NO _x burners, over-fire air (Over Fire Air (OFA)) mouth and form generally called have air stage (staging) through the mouth air Usually supplied. U.S. Patent No. 5,697,306 to LaRue, incorporated herein by reference and U.S. Patent No. 5,199,355 to LaRue discloses a low NO _x burners, the burner further NO _x Can be combined with a two-stage air combustion method to reduce emissions.

Unlike conventional burners, low NO _x burners tend to form long flames and create higher levels of unburned combustibles. Long flames are not always desirable because they may not match the depth or height of the furnace, and may impair boiler operation due to flame collision, slugging, and / or boiler tube corrosion.

The long flame is due to insufficient air supply to the fuel jet as it travels into the furnace. Low NO _x SA from the outer air zone of the burner because of lack of air supply along the flame axis, as unburned fuel persists, impermeable effectively downstream fuel jet. High levels of unburned fuel are undesirable in both furnaces with and without OFA. Unburned combustibles in the form of unburned carbon and CO reduce boiler efficiency and increase operating costs, while unburned pulverized coal, due to its inherent wear properties, causes undesirable corrosive damage to the furnace itself. obtain.

Incomplete air / fuel mixing in front of the OFA system can result in excessive amounts of undesired unburned fuel that persists to the OFA port. When a large amount of unburned fuel is going Moeyo by air at OFA zone, and length increasing NO _x formation is obtained, thereby, counteracting or either to minimize the benefits of two-stage combustion by OFA. Furthermore, it becomes increasingly difficult to burn these combustibles completely at and beyond the OFA port, which increases inefficiency and difficulty of movement.

US Pat. No. 5,697,306 US Pat. No. 5,199,355

The present invention, typical NO _x burners delay combustion aforementioned problems associated with resolves created by, also, in order to further reduce NO _x emissions in industrial and public boilers, novel that burn fossil fuels Introduce burner apparatus and method.

The burner according to the invention is suitable for igniting pulverized coal (PC) or gaseous hydrocarbons. The present invention includes an axial region that is concentrically surrounded by a first annular region. The first annular zone creates a fuel jet that exits the burner and then supplies fuel to the burner at a pre-set rate to form a burner flame via combustion in an oxygen atmosphere. The axial zone creates a central air jet that penetrates the burner flame along the internal axis of the burner flame. The central air jet supplies oxygen along the central axis of the burner flame, allowing combustion from the inside of the flame to the outside, while maintaining an overall fuel-rich environment at the root of the flame, thereby Suppresses NO _x formation.

The additional oxygen supplied by the second and third annular zones concentrically surrounding the first annular zone provides a means for accelerating combustion while further reducing NO _x formation. The flow adjustment mechanisms in the second and third annular regions aerodynamically suppress fuel jet expansion. Within this aerodynamic restraint, vortices (swirl) from the air exiting the second and third annular zones create an internal recirculation zone along the outer boundary of the flame zone, which reduces NO _x formation. suppress. Internal recirculation zone (IRZ) is, NO _x is formed along the outer air-rich periphery of the flame (outer surface) is to return to the re-circulating fuel-rich flame core in. The hotter flame temperature due to exhaustive fuel through the back and front of the central air jet allows unburned hydrocarbon groups to scavenge available oxygen in the IRZ, thereby suppressing NO _x formation. , Reducing NO returning to other nitrogen species. Due to the accelerated combustion of the fuel from outside and inside to the IRZ, a wider and shorter flame envelope results as the flame temperature increases.

Another aspect of the present invention may be considered a method of reducing NO _x emissions in a center air jet burner. The method comprises the steps of providing a burner having an axial region concentrically surrounded by a first annular region and supplying a first gas containing oxygen to the axial region, wherein the first gas is about 5000 ft / ft. The step of leaving the axial region at a speed of min to about 10,000 ft / min and the step of supplying a carrier gas (carrier gas) containing pulverized coal to the first annular region, the carrier gas is about 3000 ft / min to Exiting the first annular zone at a rate of about 5000 ft / min.

Yet another aspect of the present invention may be considered a method of reducing NO _x emissions in a center air jet burner. The method comprises the step of preparing a four-zone burner, wherein the innermost region is an axial region concentrically surrounded by a first annular region, and the first annular region is concentric by a second annular region. Wherein the second annular zone is concentrically surrounded by the third annular zone, the step of supplying a first gas containing oxygen in the axial zone, and a carrier containing pulverized coal in the first annular zone A step of supplying a gas, a step of supplying a second gas containing oxygen to the second annular region, a step of supplying a third gas containing oxygen to the third annular region, and a speed exceeding about 3000 ft / min to the burner. Supplying a carrier gas to the burner, supplying a first gas to the burner at a rate exceeding the carrier gas, supplying a second gas to the burner at a rate exceeding the carrier gas, and supplying the carrier gas to the burner. Supplying a third gas at a high rate, burning the pulverized coal in the carrier gas stream from the inside with the first gas, and pulverizing the coal in the carrier gas stream with the second gas and the third gas. Combusting from the outside of the stream, utilizing a velocity gradient between the four annular zones to create a recirculation zone in the burner flame, and recirculation of unburned coal and oxygen in the burner flame, NO _x Suppressing the formation and accelerating combustion.

  Various novel features that characterize the present invention are pointed out with particularity in the claims that are appended to and form a part of this disclosure. For a better understanding of the present invention, and the advantages of operation of the present invention and specific benefits obtained by using the present invention, reference is made to the accompanying drawings and descriptive matter illustrating preferred embodiments of the invention.

  Referring to the drawings, wherein like numerals generally indicate the same or functionally similar features throughout the several views, FIG. 1 initially shows a schematic cross-sectional view of a burner drawn in accordance with the present invention. . The axial tube 6 that forms the axial region 25 inside is concentrically surrounded by the first annular tube 3, and the region between the two tubes forms the first annular region 11. A feeder duct 9 is arranged in the radial direction between a part of the first annular pipe 3 and the shaft pipe 6, so that the shaft pipe 6 and the wind box 51 communicate with both end portions of the feeder duct 9.

  Referring to FIG. 3, at least a portion of the first annular tube 3 and the shaft tube 6 (not shown in FIG. 3) are connected so that the shaft tube 6 and the wind box 51 are in fluid communication with both ends of the feeder duct 9. A top view of the feeder duct 9 disposed radially between them is given.

  Returning to FIG. 1, the secondary air is supplied by a forced draft fan (not shown), preheated in an air heater (not shown), and receives pressure to the wind box 51. The feeder duct 9 then supplies secondary air from the wind box 51 to the axial tube 6 at a speed controlled by the damper 10. The air flow measurement mechanism 12 quantifies the secondary air flowing through the feeder duct 9.

  A crusher (not shown) crushes the coal, which is conveyed with the primary air through a conduit connected to the burner elbow 2. An igniter (not shown) may be placed in the burner axis, which ignites through the elbow 2, plug 5 and through the shaft tube 6.

  The pulverized coal and primary air (PA / PC) 1 pass through a burner elbow 2. The ground coal generally travels along the outer radius of the elbow 2 and concentrates into a flow along the outer radius at the elbow outlet. The pulverized coal enters the first annular zone 11 and encounters a deflector (deflector) 4, which deflects the coal stream to the plug 5 and disperses the coal. The shaft tube 6 is attached to the downstream side portion of the plug 5. The first annular tube 3 expands in the section 3A to form a large diameter section 3B. The dispersed coal travels along the first annular zone 11 where the bars and chevrons (7) are used as fuel jets (explosions) in the first annular zone 11. Provide a more even distribution of the pulverized coal before exiting. The wedge-shaped portions 9A and 9B (FIG. 3) provide a more contoured flow path for the PA / PC 1 as the PA / PC 1 travels past the feeder duct 9.

  A flow control mechanism 30 can be used to disperse the coal and increase the speed at which the coal interacts with the secondary air. The flow control mechanism 30 may be composed of swirl vanes and / or one or more bluff bodies to block flow locally and cause vortices.

  Another flow regulating mechanism 13 can be arranged at the end of the axial tube 6 where secondary air exits the axial zone 25 into the burner throat 8 and the furnace (in the form of a central air jet). Provide a more even flow to the secondary air as it goes into (not shown). The flow control device 13 can be a vane, a perforated plate, or other commonly used mechanism that provides a more uniform flow. In some cases, the flow regulation mechanism 13 may vortex the core air to further accelerate coal ignition and reduce emissions.

  An aspect related to the operable method of the present invention is to create a central air jet in the fuel jet stream as it exits the throat 8 and enters the furnace. Preferably, the central air jet has a velocity that exceeds the velocity of the fuel jet so as to create a velocity gradient in the flame, and the velocity gradient utilizes oxygen from the central air jet to move from the inside to the outside. Promote (sufficient) fuel ignition.

  The optimal operating condition is that the PA / PC exits the first annular zone at a speed of about 3,000 ft / min to about 5,000 ft / min, more preferably about 3,500 ft / min to about 4,500 ft / min. Occurs in some cases. The optimal operating condition is when the secondary air exits the axial region 25 at a speed of about 5,000 ft / min to 10,000 ft / min, more preferably about 5,500 ft / min to 7,500 ft / min. It also occurs.

  A damper 15 controls the introduction of additional secondary air into the burner assembly. When in the open position, the damper 15 allows secondary air to flow into the second annular zone 16 concentrically surrounding the first annular zone 11. Here, the second annular region 16 is defined as a region between the tube 3 </ b> B and the barrel (body portion) 19. The damper 15 further allows secondary air to flow into the third annular region 17 concentrically surrounding the second annular region 16. Here, the third annular zone 16 is defined as the region between the barrel 19 and the outer burner zone wall 38. The damper 15 may be arranged to preferentially throttle secondary air for one zone compared to the other zone, or to supply a smaller amount of secondary air to both zones. If an igniter (not shown) does not pass through the tube 6, it can optionally be positioned in the annular zone 17.

  The optimum operating conditions for utilizing all three annular zones to supply secondary air for combustion are from about 20% to about 40% of the total oxygen that the secondary air supplies to the burner, more preferably About 25% to about 35% is provided through the axial region 25, and about 10% to about 30%, more preferably about 15% to about 25% of the total oxygen supplied by the secondary air to the burner is second. About 40% to about 70%, more preferably about 50% to about 65% of the total oxygen supplied through the annular zone 16 and secondary air to the burner is provided through the third annular air zone 17. Occurs in some cases.

  The air flow measuring mechanism 18 measures the secondary air flow passing through the second annular region 16 and the third annular region 17. The optimal operating condition is that if the secondary air exits the second annular zone 16 at a speed of about 3000 ft / min to about 4500 ft / min, more preferably about 3100 ft / min to about 3900 ft / min, then the secondary air Occurs when the third annular zone 17 is exited at a speed of about 5500 ft / min to about 7500 ft / min, more preferably about 5700 ft / min to about 6700 ft / min.

  Optimal air distribution is generally about 9 inches to about 20 inches in the inner diameter of the axial region, about 15 inches to about 30 inches in the inner diameter of the first annular region, and about 20 inches to about 30 inches in the second annular region. Occurs when 40 inches and the inner diameter of the third annular zone is about 22 inches to about 50 inches.

  An adjustable vane 21 is positioned in the second annular zone 16 to provide spiral secondary air before exiting the second annular zone 16. Other air distribution mechanisms such as perforated plates and ramps (tilts) can also be installed at the end of the second annular zone 16. The fixed plurality of blades 22 </ b> A and the adjustable plurality of blades 22 </ b> B vortex the secondary air passing through the third annular region 17. As the vortex air leaves the third annular zone 17, the vanes 23, which may alternatively be located in the middle of the air zone outlet, divert part of the air away from the primary combustion zone.

  Referring now to FIG. 2, a graphical depiction is given in which the arrows identify the secondary air and PA / PC 1 flow paths.

  In another embodiment, a gas containing oxygen at a higher concentration than air may be utilized in place of all or part of the secondary air.

  In another alternative embodiment, hydrocarbon fuel other than pulverized coal may be utilized as the fuel.

  In another alternative embodiment, a central (central) conduit can be arranged in the axial region 25 such that the axial tube 6 concentrically surrounds the central conduit. In such embodiments, the central conduit is a lance for introducing an igniter, oil sprayer or gas substitute, or concentrated oxygen or additional hydrocarbon fuel into the flame core axially or by radial dispersion. Can be accommodated.

  In another alternative embodiment, a plurality of central conduits may be disposed in the axial region 25 such that the axial tube 6 concentrically surrounds each of the plurality of central conduits. In such embodiments, the plurality of central conduits may supply enriched oxygen in more than one stream, or at least one of the plurality of conduits provides additional coal or other hydrocarbon fuel for the fuel. Can do.

  In another embodiment, multiple feeder ducts and / or booster fans or conduits may be utilized to supply additional secondary air or oxygen to the axial region 25.

In another embodiment, to further reduce NO _x emissions, the two-stage combustion may be utilized in the burner and NO _x reduction process of the present invention.

  In yet another embodiment, the following alternative air ducting system may be devised. That is, in the system, secondary air is sent through the outer wall 51B of the windbox 51 and through the extended burner elbow outer radius range or elsewhere that fluidizes the axial region 25 with the windbox 51. To be supplied into the axial region 25.

  While specific embodiments of the invention have been shown and described in detail to illustrate the application of the principles of the invention, it will be appreciated by those skilled in the art that the invention departs from the scope of the invention. It will be appreciated that other methods may be implemented.

1 is a schematic cross-sectional view of the present invention. FIG. 4 is a schematic diagram of an embodiment of the present invention where arrows identify air and coal flow paths. FIG. 4 is an external view of a burner assembly embodiment of the present invention identifying the location of a supply duct 9. FIG. 2 is a schematic cross-sectional view of an embodiment of the present invention that identifies a plurality of concentric zones of the present invention.

Explanation of symbols

1 Ground coal and primary air (PA / PC)
2 Burner elbow 3 First annular tube 4 Deflector 5 Plug 6 Axial tube 9 Feeder duct 8 Burner throat 10 Damper 11 First annular region 12 Air flow measuring mechanism 13 Flow adjustment mechanism 15 Damper 16 Second annular region 17 Third annular region 25 Axial direction area 30 Flow adjustment mechanism 51 Wind box

Claims (38)

A central jet burner,
An axial region concentrically surrounded by a first annular region;
A feeder duct disposed radially between a part of the first annular region and the axial region, the feeder duct supplying a gas containing oxygen to the axial region;
A central jet burner comprising means for regulating the flow of the gas through the feeder duct.   The central jet burner of claim 1, wherein the axial region includes a flow adjustment mechanism.   The central jet burner of claim 1, wherein the first annular zone includes a flow adjustment mechanism.   The center jet burner of claim 1, wherein the first annular zone includes means for providing a more even coal distribution.   The center jet burner of claim 1, further comprising means for supplying a combustible fuel to the first annular zone.   The central jet burner according to claim 1, wherein the first annular region is concentrically surrounded by a second annular region, and the second annular region is concentrically surrounded by a third annular region.   The central jet burner of claim 6, further comprising means for supplying air to the second annular zone and means for supplying air to the third annular zone.   The center jet burner of claim 6 further comprising vanes in the second annular region.   The center jet burner according to claim 6, further comprising a blade in the third annular region.   The center jet burner of claim 8, further comprising blades in the third annular region.   8. The central jet burner of claim 7, further comprising means for adjusting the air flow to the second annular zone and means for adjusting the air flow to the third annular zone.   The central jet burner of claim 1, wherein an air box is in fluid communication with the second and third annular zones.   The center jet burner of claim 12, wherein an air box is in fluid communication with the axial region.   The central jet burner of claim 1, wherein the axial region is in fluid communication with a primary air duct.   2. A central jet burner according to claim 1, wherein an igniter is present in the axial region.   The central jet burner of claim 1, further comprising a conduit concentrically surrounded by the axial region.   17. A central jet burner as claimed in claim 16, wherein the conduit includes means for radially dispersing gas into the axial region.   17. A central jet burner as claimed in claim 16, wherein the conduit includes means for axially dispersing gas into an axial zone. A central air jet burner,
Comprising an axial region concentrically surrounded by a first annular region;
A central air jet burner having an axial zone diameter of about 9 inches to about 20 inches and a first annular zone diameter of about 15 inches to about 30 inches.   20. The central air jet burner of claim 19, further comprising a second annular region concentrically surrounding the first annular region, wherein the second annular region has a diameter of about 20 inches to about 40 inches.   21. The central air jet burner of claim 20, further comprising a third annular region concentrically surrounding the second annular region, wherein the third annular region has a diameter of about 22 inches to about 50 inches.   The burner according to claim 21, further comprising a conduit concentrically surrounded by the axial region. A method for reducing NOx emissions in a pulverized coal burner, comprising:
The innermost region is an axial region concentrically surrounded by the first annular region, the first annular region is concentrically surrounded by the second annular region, and the second annular region is concentric by the third annular region. Preparing a four-zone burner surrounded by a shape,
Supplying a first gas containing oxygen in the axial region;
Supplying a carrier gas containing pulverized coal to the first annular zone;
Supplying a second gas containing oxygen to the second annular region;
Supplying a third gas containing oxygen to the third annular region;
Supplying a carrier gas to the burner at a rate greater than about 3000 ft / min;
Supplying a first gas to the burner at a rate exceeding the carrier gas;
Supplying a second gas to the burner at a rate below the carrier gas;
Supplying a third gas to the burner at a rate exceeding the carrier gas;
Combusting ground coal in a carrier gas stream from the inside of the stream with a first gas;
Combusting ground coal in a carrier gas stream from the outside of the stream with a second gas and a third gas;
Utilizing a velocity gradient between the four annular zones to create a recirculation zone in the burner flame;
A method for reducing NOx emissions in a pulverized coal burner, including a step of suppressing NOx formation and accelerating combustion with recirculated unburned coal and oxygen in a burner flame.   The method for reducing NOx emissions in a pulverized coal burner according to claim 23, further comprising the step of swirling the second gas before reaching the burner flame.   The method for reducing NOx emissions in a pulverized coal burner according to claim 23, further comprising the step of vortexing the carrier gas before combustion.   The NOx emission reduction method for a pulverized coal burner according to claim 23, further comprising a step of making the third gas vortex before combustion.   The NOx emission reduction method for a pulverized coal burner according to claim 23, further comprising the step of vortexing the first gas before combustion.   The NOx emission reduction method for a pulverized coal burner according to claim 23, wherein the first gas contains 21% or more oxygen.   The NOx emission reduction method for a pulverized coal burner according to claim 23, wherein the second gas contains 21% or more oxygen.   The NOx emission reduction method for a pulverized coal burner according to claim 23, wherein the third gas contains 21% or more oxygen. A method for reducing NOx emissions in a pulverized coal burner, comprising:
Providing a burner having an axial region concentrically surrounded by a first annular region;
Supplying the first gas containing oxygen to the axial region, wherein the first gas exits the axial region at a speed of about 5000 ft / min to about 10,000 ft / min;
NOx in a pulverized coal burner comprising the step of supplying a carrier gas containing pulverized coal to the first annular zone, wherein the carrier gas exits the first annular zone at a rate of about 3000 ft / min to about 5000 ft / min. Emission reduction method. Providing the burner with a second annular region concentrically surrounding the first annular region and a third annular region concentrically surrounding the second annular region;
Supplying a second gas containing oxygen to the burner, wherein the second gas exits the second annular zone at a rate of about 3000 ft / min to about 4500 ft / min;
32. The method of claim 31, further comprising: supplying a third gas containing oxygen to the burner, wherein the third gas exits the third annular zone at a rate of about 5500 ft / min to about 7500 ft / min. NOx emission reduction method for pulverized coal burners.   33. The first gas exits the axial zone at a speed of about 5500 ft / min to about 7500 ft / min, and the carrier gas exits the first annular zone at a speed of about 3500 ft / min to about 4500 ft / min. The NOx emission reduction method in the pulverized coal burner described in 1.   The second gas exits the second annular zone at a rate of about 3100 ft / min to about 3900 ft / min, and the third gas exits the third annular zone at a rate of about 5700 ft / min to about 6700 ft / min. Item 34. A method for reducing NOx emissions in a pulverized coal burner according to Item 33.   Supplying oxygen to the burner flame, wherein about 20% to about 40% of the total oxygen is supplied by the first gas passing through the axial region, and about 10% to about 30% of the total oxygen is in the second annular shape. 34. The method of reducing NOx emissions in a pulverized coal burner according to claim 33, wherein the NOx emissions are provided by a second gas passing through the zone and about 40% to about 70% of the total oxygen is supplied by the third gas passing through the third annular zone.   36. NOx emissions in a pulverized coal burner according to claim 35, further comprising vortexing at least one of the group consisting of a first gas, a second gas, a third gas and a carrier gas before reaching the burner flame. Reduction method. Combusting pulverized coal in a carrier gas stream from the inside of the stream with a first gas; combusting pulverized coal in a carrier gas stream from the outside of the stream with a second gas and a third gas;
Providing means for creating a recirculation zone in the burner flame;
36. The method for reducing NOx emissions in a pulverized coal burner according to claim 35, further comprising a step of suppressing NOx formation and accelerating combustion with recirculated unburned coal and oxygen in the burner flame.   36. The method of claim 35, further comprising utilizing flow adjustment means for adjusting gas flow within at least one of the group consisting of the axial region, the first annular region, the second annular region, and the third annular region. NOx emission reduction method for pulverized coal burners.

Images