KR890000326B1 - Split nozzle tip for pulverized coal burner - Google Patents

Abstract

The nozzle tip comprises open-ended inner and outer shells mounted to the fuel delivery pipe and defining a flow passageway within the inner shell through which the pulverized fuel is directed into the furnace and an annular flow passageway between the inner and outer shells through which additional air is directed into the furnace. A pair of diverging splitter plates are disposed within the inner shell to divide the flow passageway to two separate, diverging subpassages so that the pulverized fuel stream discharging from the fuel delivery pipe is split into first and second streams which pass from the nozzle tip into the furnace in a diverging manner thereby establishing an ignition stabilizing pocket in the low pressure zone created between the diverging fuel streams.

Description

Nozzle tip and vortex breaker plate of fine fuel burner

1 is a schematic plan view of a furnace in tangential combustion.

FIG. 2 shows, in a set of three injection devices, an upper char-air injection device with a nozzle tip according to the invention and two char-air injection devices with a nozzle tip of the prior art in the set of three injection devices. Sectional drawing which cut the line 2-2 of FIG.

3 is a cross-sectional view of one shot-nozzle injection device having a nozzle tip according to the present invention.

4 is a cross-sectional view of the nozzle tip according to the present invention.

5 is a cross-sectional view taken along the line 5-5 of FIG. 4, which is a nozzle tip according to the present invention.

6 is a cross-sectional view of another embodiment in a nozzle tip according to the present invention.

* Explanation of symbols for main parts of the drawings

1: to 3: virtual circle

10: injection device 12: bullet powder pipe

14 second air conduit 16 axis

18: wind box 20: compartment

26: shield plate 28: conventional nozzle tip

30: nozzle tip of the present invention 32: the inner

34: outer 36: exit end

38: inlet end 40: plate means

41: first vortex preventing plate 42: second vortex preventing plate

43: introduction end 44: track end

45: first part 46: spacing plate

47: second part 50: annular flow passage

52: first flow passage 54: second flow passage

56: center space 60, 70: carbon-air

80: low pressure range

The present invention improves the low load operation of a fuel burner for a pulverized coal combustion furnace, and in particular, a fuel-air injection device operating at a low load for injecting a fine fuel-air mixture into a furnace by a known method such as tangential combustion. will be.

In view of the fluctuating demand for electricity today, the demand peaks during the day and falls to a minimum during the day and on weekends.The demand for electricity demands a full load when demand peaks and lowers the load when demand falls. By operating, the cycle of a conventional coal fired steam boiler was achieved.

As this type of operation continues, the air flow generated from the carbon dioxide steam generator in electricity use requires the stability of the carbonate when operating at low loads, so that natural gas or oil can be supplied incidentally during low load operation. It has been used in large quantities. It is important to ignite the fuel in the axial direction to stabilize, and 11,000 gallons of oil are required daily to maintain a 500 megawatt steam generator at 10-15 percent load while electrical demand is at a minimum.

One common method of burning fine fuel, such as coal, in a conventional steam generator is the well known tangential injection method. In this way pulverized coal is introduced into the furnace as primary air through a burner, a fuel-air injection device located at the corner of the furnace. The fuel-air flow discharged from the injection device is injected tangentially to form a virtual circle in the middle of the furnace. This forms a flame hole that acts as a source for continuously burning incoming coal. Each fuel-air injector has a nozzle tip pivotally mounted at the outlet end of the fuel distribution plate which feeds the pulverized coal mixed with air to the furnace, the second air-conducting pipe which surrounds the fuel distribution pipe which sends the air incidentally to the furnace, and the fuel distribution plate. It consists of.

A typical nozzle tip includes inner and outer axially arranged in isolation from each other and includes a first flow passage and a second air passage in the interior through which a mixture of fine fuel and air discharged from the fuel distribution pipe into the furnace. It is defined as the second flow path in the annular space between the interior and the exterior through the secondary air emitted into the interior. Typically one or more vortex barriers are disposed in an interior parallel to the axis of the nozzle tip such that the flow passage in the interior diverges into multiple side passages. The nozzle tip is tilted upward or downward so that the direction of the fuel and air mixture is upward or downward as a means of adjusting the temperature of the superheated steam generated at the heat exchange surface typically arranged at the outlet of the surface in the manner described in US Pat. No. 2,863,875. It is discharged from the fuel distribution pipe into the furnace.

During normal operation of the tangential combustion furnace, flames form at one corner, supplying combustion energy to stabilize the flame radiated from the corners downstream of the corners and laterally adjacent to the corners. As the load drops, the flame radiated at each corner is shortened, and the combustion energy required downstream downstream of the corner is reduced. As a result, auxiliary fuels, such as natural gas or oil, must be injected into each corner adjacent to the pulverized coal-air stream to supply incidental combustion energy, so that the flame suddenly stops and no unit trip occurs.

Another problem associated with the use of coal-burning burners at low loads is that the mill typically operates with continuous supply of airflow at all-weather loads. As the load on the furnace drops, the amount of coal pulverized in the grinder decreases proportionally, while the amount of main air used to transport the pulverized coal from the grinder into the furnace through the injection device is nearly constant, resulting in a small fuel / air ratio. If the load in the furnace drops to the desired level during low electricity demand, the fuel / air ratio is reduced to such an extent that the mixture of pulverized coal and main air is too weak to stabilize the combustion and is not stable without the need to support combustion energy.

One method of burning auxiliary fuel while operating a coal-burning boiler at low load is described in US Pat. No. 4,252,069. The patent relates to an improved fuel-air injector using branched carbon buckets, which proposes pulverized coal-fired furnaces that can be operated at low loads without the need for auxiliary fuel for stabilization. In that context, the branched tanbucket aligns independent upper and lower nozzles pivotally installed in the coal distribution pipe, which can be inclined independently. When the furnace is operated at low load while electricity demand is at its lowest, the main paper and pulverized coal discharged from the coal distribution pipe branch to the upper and lower nozzles so that the upper nozzle is inclined upward and the lower nozzle is inclined downward. Is injected into. At this time, the combustion stabilizing pocket is formed in the local low pressure region generated in the space between the coal-air which is spread far away. The hot combustion product is recycled into the low pressure region, whereby the incoming fuel stabilizes the flame with sufficient auxiliary combustion energy.

The secondary nozzle tip described in US Pat. No. 2,608,168 improves the stability of combustion, although it relates to the combustion of low volatility coal rather than combustion in low load operation. The patent describes a tanbucket pivotally installed in a coal distribution pipe having a flow passage that is defined in two in parallel but separated from the side flow passage. The secondary air is discharged into the furnace from the second air conduit surrounding the coal flue pipe through a central channel formed between the flow passage between the inner and outer and parallel and isolated sub-paths in the inner. Combustion is improved by increasing the area of contact between the coal-air mixtures released from the inner isolated flow passages and blocking secondary airflow.

However, the problem still remains with the nozzle tip. There is a need for a nozzle tip with a relatively simple design that exhibits improved combustion stability at low load operation. In addition, such a nozzle tip should be able to be easily manufactured or cast.

The present invention allows the nozzle tip for the burner on the differential fuel combustion furnace to improve combustion stability during furnace operation at low load. The nozzle tip of the present invention is limited to a flow path through which a mixture of fine fuel and conveying air flowing from the burner flows through the opening, and an annular flow path between the burner and the combustion auxiliary air flowing into the furnace. The inner passage to divide the flow passage leading into the first and second flow passages extending from the inlet of the inner portion to the outlet of the inner portion in a manner formed in the space formed between the surrounding open end and the flow inhibited passageway in an isolated state. And plate means disposed therein. The mixture of carbon-air exiting the burner is split by plate means into the primary flow into the furnace through the first flow passage leading to the interior and into the furnace through the internal second flow passage. The coal-air mixture is thus split into two streams and injected into the furnace. At this time, the combustion stabilizing pocket is formed in the local low pressure region generated between the spreading and split coal-air flow in the furnace just below the known well formed between the first and second flow passages branching through the inside of the nozzle tip. The coal is concentrated in the pocket and the hot combustion product is returned from the flame into the pocket so that the subcombustion energy by the incoming fuel stabilizes the flame.

The plate means comprise suitable first and second vortex breakers disposed in the interior with an inlet end disposed across the inner flow passage at the inlet and an orbital end extending across the inner flow passage at the outlet. The first and second vortex baffles extend along the line at the inlet end of the inner cage and branch out toward the outlet end of the inner cage. In this way, the first and second vortex baffles guide the flow passage through the interior into the first flow path coupled by the first vortex baffle and the interior and the second flow path coupled by the second vortex baffle and the interior. Branch The first and second flow passages are separated by a space formed between the first and second branched vortex blocking plates whose flow is inhibited toward the direction through the nozzle tip. The low pressure recirculation zone is thus formed in the furnace just below the space of the nozzle tip between the fuel-air streams diverging as it is released into the furnace from the first and second flow passages branching through the interior.

According to the present invention, combustion stability can be further improved by installing a scalloped raceway end on the vortex barrier. The orbital end of the vortex barrier plate traverses the flow passage through the inner edge of the vortex barrier plate of a plurality of longitudinally elongated strips extending in the longitudinal direction from the inlet side of the vortex barrier plate to the outside in a lateral to side relationship. By appropriately capturing. The first portion of the raceway end alternately disposed between the second portions of the raceway strip bends radially away from the guide end of the vortex baffle in one direction, while the second portion of the raceway strip is vortexed It is bent away from the leading end of the vortex blocking plate in the direction opposite to the bending direction away from the leading end of the preventing plate. In this way, the skipped end is formed along the orbital end of the vortex barrier plate, which serves to generate turbulence along the boundary between the fuel-air flow and the space formed between the boundary and the fuel-air stream discharged from the branched flow passage. The mixture of hot combustion products is led into a low pressure recycle zone formed in the furnace just below the space of the nozzle tip, further improving combustion stability.

A number of different burners are applied within the spirit and scope of the present invention in various combustion methods commonly used in boiler furnaces that generate steam by burning conventional fine fuel, as shown in FIG. The pulverized coal-air injection device, which is a form adopted in a pulverized coal combustion furnace utilized for, will be described in detail as an embodiment. In tangential combustion, pulverized coal and air are introduced into the furnace through the coal-air injection device 10 disposed at four corners in the furnace 1. The coal-air injector 10 is oriented such that the pulverized coal and the air stream tangential to the virtual circle 3 in the center of the furnace 1 so as to generate a vortex flame called a flame hole.

As shown in FIG. 2, a plurality of coal-air injectors 10 are disposed at the corners of the furnace in a vertical column isolated by large axial compartments 20, 20 '. One or more axial air compartments, such as compartment 20 ', are adapted to accommodate oil or gas burners, and conventionally require additional ignition energy to stabilize the carbides when operating the furnace at low loads. Thus used for starting and preheating the boiler.

Each coal-air injector 10 is connected to an injection tube 12 extending through the apparatus, a passage into the furnace, and an air supply plenum 18 which surrounds the passage and the bullet injection tube 12 and is called a wind box. And a second air-conduit 14 connected thereto. The pulverized coal introduced into the air supply is charged into the furnace through the coal-injection pipe 12 from a source such as a crusher for drying and replacing the coal. Secondary air is introduced into the furnace through the second air-conducting pipe 14 as the air flow surrounds the pulverized coal and the supply air flow discharged from each coal injection pipe 12. Incidentally, combustion air flows into the furnace from the wind box 18 through the axial air compartment 20.

Each shot pipe 12 is provided with a nozzle tip, often associated as a ball bucket, which is arranged pivotally on the shot-jet 12 and traverses the lengthwise side of the shot pipe 12. Inclined with respect to the shaft, a mixture of pulverized coal and air is introduced into the furnace from a downward or angled position as a means of adjusting the position of the flame holes in the furnace, the temperature of which generates superheated steam in a steam generator (not shown). A method of adjustment is described in US Pat. No. 2,363,875, entitled "Combustion Zone Adjustment," which was granted to many of Singer. The nozzle tip 28 shown in FIG. 2 is a typical example of a conventional nozzle tip typically disposed in a coal pipeline 12.

A typical nozzle tip 28 of the prior art includes an open end, which is limited to a flow passage through a furnace in which a mixture of pulverized coal and supply air is enclosed by an open end inside that is isolated from the coal dust pipe 12. The secondary air is confined to the annular flow passage between the passages passing from the second airway pipe 14 into the furnace. The inner and outer sides are arranged at the outlet end of the carbon distribution pipe 12 by turning pins so as to be inclined with respect to the shaft 16. Typically one or more shield plates 26 are disposed in the interior of a conventional nozzle tip 28 along an axis parallel to the nozzle tip and the coal flute pipe 12 and subdivided into one or more parallel and continuous base streams. As a single air flow, two or more parallel flow passages are formed in the inner circumference of the pulverized coal and air passages from the coal dust pipe 12 into the furnace. As mentioned above, operation of a furnace with a nozzle tip of the prior art at low loads causes combustion to become unstable and safe combustion of a single coal-air stream from which auxiliary fuels, such as natural gas or oil, are discharged from the nozzle tip 28. It had to combust with sufficient incidental ignition.

In accordance with the present invention stable combustion at low loads can be achieved using a nozzle tip 30 which has an inherently improved ignition capability during low load operation. The nozzle tip 30 has a plate means 40 disposed in the inner part for dividing the inner part of the open part 32, the open part outer part 34 surrounding the inner part, and the inner part of the inner part into the first and second flow passages. It includes. The inner shell 32 has an outlet end 36 opened into the furnace and an inlet end 38 suitably installed around the outlet end of the coal dust pipe 12 to receive pulverized coal and released air. The annular flow passage 50 is defined between the inner shell 32 and the outer shell 34, through which the secondary combustion air passes from the second air pipe 14 to the furnace. The plate means 40 according to the invention extends from the inlet end 38 of the inner shell 32 to the outlet end 36 of the outer shell 34 in a branching manner, avoiding the area formed therebetween through the point where the flow is disturbed. It is arranged in the interior 32 to divide the flow passage into respective first and second flow passages 52, 54. The nozzle tip is intended to be used in low load operation as two separate and separate parts which diverge the flow passages 52 and 54 through the inner portion 32 separated from the upper and lower portions of the central space 56 where the flow is suppressed. Achieves improved ignition performance. As can be clearly seen in the figure, the flow of pulverized coal and air discharged from the coal dust pipe 12 to the nozzle tip 30 is divided into two parts. One part is connected into the furnace through the first flow passage 52 of the nozzle tip 30 which is discharged upward into the furnace, while the other part of the pulverized coal and the supply air flow is downward as shown in FIG. It is connected to the furnace through the second flow passage 54 of the nozzle tip 30 discharged into the furnace.

The low pressure region 80 acting as a region for stabilizing combustion is formed in the furnace at the outlet of the nozzle tip 30 downstream of the central space 56 between the branched ball air streams 60 and 70. The suppressors from the air streams 60, 70 are led from the branched coal-air streams 60, 70 to the low pressure region 80. Since part of the hot combustion product formed during combustion recycles in the low pressure zone 80, the ignition is stable and the combustion carbon particles continuously flow into the low pressure zone 80 from the branched coal-air streams 60 and 70. Sufficient combustion energy is generated for

In a preferred embodiment of the present invention, the plate means 40 is the first vortex prevention plate 41, the inner circumference 32 is coupled to the inner side of the inner circumference 32 by the second swirl prevention plate 42 and the inner rim 32 And first and second vortex breakers disposed in the interior 32 to be divided into a first flow passage 52 coupled by a second flow passage 54. Each of the vortex barriers 41, 42 traverses the flow passage of the inner end 32 at the inlet end 43 and the outlet end 36 arranged across the flow passage of the inner end 32 at the inlet end 38. It has a track end 44 that extends. The first and second vortex baffles 41, 42 assemble along a line and extend outwardly from the inlet end 38 of the inner shell 32, about 20 toward the outlet end 36 of the inner shell 32. ˚ and is confined between the central space 56 where the flow is suppressed.

In order to improve the ignition capability, as shown in FIGS. 4, 5 and 6, the track ends 44 of the first and second vortex blocking plates 41 and 42 are scalloped to further improve the ignition capability. For scalloping the track ends 44 of the first and second vortex breakers 41, 42, the track ends 44 traverse the flow passages of the inner periphery 32 and in the plane-to-face vortex barrier plate. It includes a plurality of longitudinally stretched strips extending in the longitudinal direction of the outside from the leading end 43 of the. In the strip of the raceway end extending in the longitudinal direction outside from the leading end of the first and second vortex breakers, the first part 45 alternately crosses the interior between the second part 47 of the raceway end strip. The track ends are arranged and are bent radially from the second portion 47 of the track end strips to be suitably scalloped on the first and second vortex breakers 41, 42. The first portion 45 of the raceway strip is radially suitably bent from the leading end 43 of each vortex baffle in one direction, while the first portion 47 of the raceway strip is the first portion 45. It bends suitably from the introduction end part 43 of each vortex blocking plate in the direction opposite to this bending direction.

By forming a scalloped orbital end on each of the vortex breakers 41, 42, a shared region between each of the coal-air streams 60, 70 is formed in the low pressure recirculation region 80 formed therebetween. Formed accordingly. The turbulent sharing zone is carbon and air are drawn from the coal and air flow and completely mixed with the high-temperature combustion products in the low pressure recirculation zone 80 to further improve the ignition performance.

Also suitably extended elongated spacing plates 46 traversing between adjacent first and second portions 45, 47 of the raceway strip along the shared area between the raceway ends as shown in FIGS. 5 and 6. ) So that the atomized fuel and the supply air cannot flow across the shared area formed between the orbital end strips 45 and 47 which are adjacent to each other. When a significant amount of atomized fuel and feed air flow through the orbital end strips (45, 47) into the central space (56), a low pressure recirculation zone between the branched coal-air streams (60, 70) is formed. It is going back. In other words, the vortex blocking plates 41 and 42 are arranged in the inner edge 32 of the nozzle tip 30 so that the scallop orbital end portions are arranged in the line array as shown in FIG. Is placed.

As shown in the figure, the swirl preventing plates 41 and 42 can also be easily manufactured by a known casting method as they are made of various pieces of sheet metal welded to each other. In addition, the service life of the vortex baffle in the coal stream flowing through the inner shell 32 is in accordance with US Pat. No. 4,356,975, issued Nov. 2, 1982, to Chapshay, entitled "Nozzle Tip for Pulverized Coal Burner." Improvement is made by manufacturing the vortex barrier plates 41 and 42 with the induction end 43 made of a relatively wear resistant material such as silicon carbide or nitrogen hardening and the raceway end 44 made of a relatively high temperature resistant material such as well known stainless steel. do.

Although the present invention using a coal-air injection device in a tangential combustion furnace has been described in detail through suitable embodiments, it is not limited thereto. The nozzle tip of the present invention can be easily modified by those skilled in the art within the spirit and scope of the present invention and can use pulverized coal or other pulverized solids.

Claims (8)

Nozzle tip for burner of fine fuel combustion furnace, in which the fine fuel and conveying air are defined between the flow passage from the burner into the furnace and surround the inside and inside of the open end with the inlet end and the outlet end in an isolated state. The first and second flow passages extending from the inlet end of the inner to the outlet end of the inner in such a way as to branch into the space formed between the open end and the flow restricting passage defined between the annular flow passage from the burner into the furnace. A nozzle tip and a vortex preventing plate of a fine fuel burner, characterized in that it comprises a plate means disposed in the interior for branching the flow passage through. 2. The plate means according to claim 1, wherein the plate means comprise first and second vortex breakers disposed within the interior, wherein the first and second vortex breakers each have an induction end disposed across the flow passage of the interior at the inlet end. It has an orbital end extending from the outlet end across the inner flow passage, extending along the line at the inlet of the inner end and branching out toward the outlet end of the inner side, coupled by the first swirl preventing plate and the inner side. The nozzle tip of the fine fuel burner characterized in that it is isolated from the space area as a means for branching the flow passage flowing through the inner flow into the second flow passage coupled by the first flow passage and the second vortex preventing plate and the inner Vortex Vane. 2. The nozzle tip and vortex breaker of claim 1, wherein the first and second vortex breakers branch at an angle of about 20 degrees. 3. The nozzle tip and the vortex breaker of claim 1, wherein the track ends of the first and second vortex breakers are scalloped. 5. The plurality of lengths of claim 4 wherein the raceway ends of the first and second vortex breakers extend in an outer longitudinal direction from each guide end of the first and second vortex breakers in parallel across the inner flow passage. And a first portion of the orbital end strip being alternately disposed between the second portions of the orbital end strips and radially bent away from each guide end of the first and second vortex breakers to form a first strip. And a scallop orbit end of the second vortex breaker plate, respectively. 6. The method of claim 5, wherein the second portion of the raceway end strips comprises: first and second in a direction opposite to the direction in which the first portion of the raceway strip is radially bent away from each guide end of the first and second vortex breakers. A nozzle tip and a vortex breaker plate of a fine fuel burner, characterized in that it is bent radially away from each guide end of the vortex breaker plate. 7. The method of claim 6, further comprising: a plurality of spacing plates disposed transversely between adjacent first and second portions of the raceway strip along the common area such that the fuel and conveying air are branched adjacent to the raceway strip; And a nozzle tip and a vortex preventing plate of the fine fuel burner, characterized in that they do not flow across the shared area formed between the second portions. 8. The nozzle tip and vortex breaker of claim 7, wherein the guide ends of the first and second vortex breakers branch at an angle of about 20 degrees.

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