JP2013108717A - Biomass burner and boiler device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a biomass burner and a boiler device which can supply a large amount of woody biomass to furnace with a simple structure.SOLUTION: The biomass burner includes: a nozzle part 31 which is provided in the furnace wall 28 of the furnace 1; and a burner support part 29 which supports the nozzle part. The biomass is conveyed to the nozzle part by a biomass conveyance medium in which primary air is mixed with an exhaust gas. Moreover, the biomass is flowed into the nozzle part 31 from a tangent direction. Furthermore, a swirler is provided at the end of the nozzle part.

Description

  The present invention relates to a biomass burner and a boiler device that are provided on the wall surface of a boiler furnace and burn wood-based biomass fuel such as wood pellets and wood chips.

Currently, coal is mainly used as solid fuel for boilers, but as a measure to reduce CO ₂ , diversification of fuels such as wood-based biomass that is renewable and has a low environmental impact is considered. Has been.

  Conventionally, when wood-based biomass is used as fuel, coal and wood-based biomass are mixed and pulverized by a mill, and a pulverized product obtained by mixing coal and wood-based biomass is supplied to a burner as fuel. In recent years, it has been required to increase the mixing ratio of woody biomass fuel.

  However, in the case of mixed pulverization, there is a limit to increasing the mixing ratio, and a large amount of woody biomass cannot be crushed, so that woody biomass cannot be sufficiently supplied as fuel for the burner. Furthermore, since combustion characteristics differ between coal and woody biomass, there is a risk that combustion will become unstable if the ratio of woody biomass is increased.

  In Patent Document 1, biomass is pulverized by a roller mill alone, and the pulverized biomass is mixed with pulverized coal separately pulverized using a roller mill, or the biomass is separately supplied to a burner separate from pulverized coal. A burner for burning is disclosed.

JP 2010-242999 A

  In view of such circumstances, the present invention provides a biomass burner and a boiler device that can supply a large amount of woody biomass to a furnace with a simple structure.

  The present invention includes a nozzle part that is provided on a furnace wall of a furnace and ejects biomass, and a burner support part that supports the nozzle part, and the biomass is a biomass transport medium in which exhaust gas is mixed with primary air. The present invention relates to a biomass burner conveyed to the nozzle part.

  The present invention also relates to a biomass burner in which biomass flows into the nozzle portion from a tangential direction, and a swirler is provided at the tip of the nozzle portion, and the biomass is diffused by the swirler.

  In the present invention, the biomass burner and the pulverized coal burner for burning the pulverized coal are provided in at least two upper and lower stages, and a part of the primary air is fed to the pulverized coal burner. A primary air supply system that supplies the other part of the primary air to the biomass burner and a part of the exhaust gas discharged from the furnace are extracted and mixed with the other part of the primary air. The present invention relates to a boiler device including an exhaust gas circulation system as a biomass transport medium for feeding biomass to the biomass burner.

  The present invention also relates to a boiler apparatus in which the pulverized coal burner is provided in the upper stage and the biomass burner is provided in the lower stage.

  The present invention further includes a control device for controlling the combustion ratio of the biomass burner and the pulverized coal burner, and the control device maintains the combustion ratio of the furnace and responds to an increase in the combustion ratio of the biomass burner. The present invention also relates to a boiler apparatus that reduces the combustion ratio of the pulverized coal burner, and further relates to a boiler apparatus further provided with an over air port provided on the furnace wall and capable of supplying secondary air into the furnace.

  According to the present invention, it is provided on a furnace wall of a furnace and includes a nozzle part for ejecting biomass and a burner support part for supporting the nozzle part, and the biomass is transported for biomass in which exhaust gas is mixed with primary air. Since it is conveyed to the nozzle part by the medium, a mechanism for supplying combustion air for burning the biomass is not required, and the structure can be simplified and the manufacturing cost can be reduced.

  Further, according to the present invention, the biomass burner and the pulverized coal burner for burning the pulverized coal are provided in at least two upper and lower stages, and the pulverized coal for supplying a part of the primary air to the pulverized coal burner. A primary air supply system that supplies the other part of the primary air to the biomass burner and a part of the exhaust gas discharged from the furnace, and mixes with the other part of the primary air And having an exhaust gas circulation system as a biomass transport medium for feeding biomass to the biomass burner, the oxygen concentration of the biomass transport medium is set to an oxygen concentration to prevent biomass ignition, Excellent in that biomass can be transported safely, biomass combustion can be performed in a reducing atmosphere, and NOx reduction of exhaust gas discharged from the furnace can be achieved. It is effective.

It is a schematic block diagram which shows the boiler apparatus which concerns on the Example of this invention. It is a schematic sectional drawing which shows an example of the biomass burner used for this boiler apparatus. It is a perspective view of this biomass burner, (A) shows the perspective view of the biomass burner seen from back, and (B) shows the perspective view of the biomass burner seen from the front. (A) is a graph showing the volatilization process of woody biomass and pulverized coal under a predetermined condition, and (B) is a graph showing the combustion process of woody biomass and pulverized coal under a predetermined condition.

  Embodiments of the present invention will be described below with reference to the drawings.

  First, referring to FIG. 1, a boiler apparatus 10 according to an embodiment of the present invention will be described.

  In FIG. 1, 1 indicates a furnace. On the furnace wall of the furnace 1, a plurality of burners are arranged in the vertical direction, for example, four stages, and the burners are arranged at a predetermined pitch in a horizontal direction (a direction perpendicular to the paper surface in FIG. 1). The upper two stages are biomass burners 2 and the lower two stages are pulverized coal burners 3. Further, the furnace wall of the furnace 1 has a predetermined number of places in the furnace 1 at predetermined places, for example, between the upper pulverized coal burner 3 and the lower biomass burner 2 and above the upper biomass burner 2. An over air port 4 for directly supplying secondary air is provided.

  In the boiler device 10 according to the embodiment of the present invention, for example, 25 cal. % Combustion ratio and 12.5 cal. Per biomass burner 2. % Combustion ratio can be ensured, and only 100 cal. % Combustion ratio can be secured. Further, 50 cal. % Combustion ratio can be obtained.

  The biomass burner 2 and the pulverized coal burner 3 may be arranged in three or more stages in the upper and lower directions.

  In FIG. 1, 5 is a heat exchanger using the residual heat of the exhaust gas as a heat source, 6 is a biomass mill, 7 is a pulverized coal mill, 8 is a primary air blower that sends out primary air 20, and 9 is secondary air. A secondary air blower to be sent out, 11 an exhaust gas blower for discharging exhaust gas, and 12 a control device.

  The primary air blowing duct 13 is connected to the biomass mill 6 and the pulverized coal mill 7 through the heat exchanger 5, and the primary air 20 heated to a predetermined temperature, for example, 200 °, by the heat exchanger 5. It leads to the biomass mill 6 and the pulverized coal mill 7.

  The primary air blower 8 is provided at the upstream end of the primary air blowing duct 13 and branches into a biomass mill side duct 13a and a pulverized coal mill side duct 13b on the way. The downstream end of the biomass mill side duct 13a is connected to the biomass mill 6 and is further downstream of the biomass mill side duct 13a downstream from the branch point between the biomass mill side duct 13a and the pulverized coal mill side duct 13b. One flow rate adjustment valve 14 is provided. The downstream end of the pulverized coal mill side duct 13 b is connected to the pulverized coal mill 7. The primary air blower 8 and the primary air blow duct 13 constitute a primary air supply system.

  The biomass mill 6 pulverizes woody biomass such as wood chips and wood pellets into fine powder, uses a mixed flow of primary air 20 and exhaust gas as a carrier medium for biomass, and uses the crushed biomass as a biomass supply pipe 15. To the biomass burner 2 individually. The biomass supply pipe 15 is provided with a first cut damper 17, and the biomass supply pipe 15 can be individually cut off and opened by the first cut damper 17. The supply of wood biomass can be stopped independently.

  In FIG. 1, woody biomass crushed by one biomass mill 6 is supplied to both of the two stages of the biomass burners 2, 2. The biomass mill 6 is provided, and the biomass burner 2 is connected to the biomass supply pipe 15 and the biomass mill 6, respectively.

  The pulverized coal mill 7 pulverizes massive coal into pulverized coal, and individually feeds the pulverized coal mixed stream to the pulverized coal burner 3 through the pulverized coal supply pipe 18 using the primary air 20 as a carrier for pulverized coal. To pay. Further, the pulverized coal supply pipe 18 is provided with a second cut damper 19, and the pulverized coal supply pipe 18 can be individually cut off and opened by the second cut damper 19. In contrast, the supply of pulverized coal can be stopped independently.

  In FIG. 1, the pulverized coal pulverized by one pulverized coal mill 7 is supplied to both of the two stages of the pulverized coal burners 3, 3. The pulverized coal mill 7 is provided corresponding to each of the pulverized coal burners 3, and the pulverized coal supply pipe 18 and the pulverized coal mill 7 are individually connected to the pulverized coal burner 3, respectively.

  The secondary air blowing duct 21 which is a supply path for secondary air has an upstream end connected to the secondary air blower 9 via the heat exchanger 5 and a downstream end connected to each pulverized coal burner 3. . The secondary air sent from the secondary air blower 9 is supplied to the pulverized coal burner 3 through the secondary air blow duct 21 as combustion air.

  Although not shown, the secondary air blower 9 and each over air port 4 are connected via a pipe so that secondary air can be supplied from the over air port 4 into the furnace 1.

  A second flow rate adjustment valve 22 is provided on the downstream side of the heat exchanger 5 in the secondary air blower duct 21, and the second flow rate adjustment valve 22 is supplied to the plurality of pulverized coal burners 3. Secondary air supply is stopped and the flow rate is adjusted all at once.

  Further, an upstream end of an exhaust gas conduit 24 is connected to the flue 23 of the furnace 1, and a downstream end of the exhaust gas conduit 24 is connected to a downstream side of the first flow rate adjusting valve 14 of the biomass mill side duct 13a. ing. The exhaust gas conduit 24 is provided with a third flow rate adjusting valve 25, and the exhaust gas conduit 24 and the third flow rate adjusting valve 25 constitute an exhaust gas circulation system. The exhaust gas conduit 24 extracts high temperature and low oxygen concentration exhaust gas from the flue 23 before heat exchange by the heat exchanger 5 and mixes it with the primary air 20 flowing through the biomass mill side duct 13a. It has become.

  Here, the temperature of the primary air 20 before the exhaust gas is mixed, that is, the temperature of the primary air 20 heated by the heat exchanger 5 is about 200 ° C., and the oxygen concentration is about 21%. The temperature of the extracted exhaust gas is about 150 ° C. to 300 ° C., and the oxygen concentration is about 3.5%.

  A combustion control command for requesting a combustion state corresponding to the boiler load state is input to the control device 12 from a main control device (not shown) that performs comprehensive control of the main body of the boiler device 10, and the control device 12 Based on the combustion control command, the biomass mill 6, the pulverized coal mill 7, the first flow rate adjustment valve 14, the first cut damper 17, the second cut damper 19, the second flow rate adjustment valve 22, and the third flow rate. The regulating valve 25 is driven and opened / closed at a predetermined timing to control the combustion state of the biomass burner 2 and the pulverized coal burner 3.

  A temperature detector 26 and an oxygen concentration detector 27 are provided on the downstream side of the joining point of the biomass mill side duct 13a and the exhaust gas conduit 24. The temperature detector 26 detects the temperature of the biomass transport medium flowing through the biomass mill side duct 13a, the oxygen concentration detector 27 detects the oxygen concentration of the biomass transport medium, and each detection result is the control. Sent to the device 12. Based on the signals from the temperature detector 26 and the oxygen concentration detector 27, the control device 12 is set to a predetermined temperature, for example, about 200 ° C. to 300 ° C., and a predetermined oxygen concentration, for example, an oxygen concentration of 14 is set. The opening degree of the first flow rate adjustment valve 14 and the third flow rate adjustment valve 25 is controlled so as to be less than%.

  2, FIG. 3 (A) (B) has shown an example of the said biomass burner 2 used for a present Example. Hereinafter, the outline of the biomass burner 2 will be described with reference to FIGS. 2, 3 </ b> A and 3 </ b> B.

  A cylindrical or substantially cylindrical burner support portion 29 is attached to the anti-furnace side of the furnace wall 28 of the furnace 1, and the biomass burner 2 is connected to the burner support portion 29 so as to penetrate the inside of the burner support portion 29. Concentric. The biomass burner 2 has a cylindrical nozzle portion 31 that gradually decreases in diameter toward the tip. The nozzle portion 31 is supported by the burner support portion 29 in the middle, and the tip opens into the furnace 1. Yes. Further, a biomass conduction space 32 having an open end on the furnace 1 side is formed in the nozzle portion 31.

  Further, the biomass supply pipe 15 communicates with the base portion (end portion on the side of the counter-fired furnace) of the biomass burner 2, and a swirler 33 is provided at the tip portion. A biomass flow 16, which is a mixed flow of the biomass transport medium and the fine biomass powder, flows into the biomass conduction space 32 from the tangential direction via the biomass supply pipe 15. The biomass stream 16 flows to the tip side while swirling in the biomass conduction space 32, is further diffused by the swirler 33, and is ejected into the furnace 1.

  Next, the operation of the embodiment according to the present invention will be described.

  First, the second flow rate adjusting valve 22 is opened by the control device 12, and an auxiliary combustion burner (not shown) of the pulverized coal burner 3, such as an oil burner or a gas burner, is used for oil combustion or gas. Preheating by combustion is performed, and the temperature in the furnace 1 is raised.

  After the temperature in the furnace 1 has risen sufficiently, the control device 12 stops combustion by the auxiliary combustion burner, drives the pulverized coal mill 7, opens the second cut damper 19, The pulverized coal is supplied to the pulverized coal burner 3 by the charcoal transport medium. Thereafter, the combustion state of the pulverized coal burner 3 is switched to pulverized coal combustion with pulverized coal and secondary air.

  At this time, pulverized coal combustion is performed in all the pulverized coal burners 3 in the furnace 1, and 100 calc. % Combustion ratio is secured.

  In this state, the biomass transport medium that is a mixed flow of the exhaust gas mixed with the primary air 20 through the exhaust gas conduit 24 has a temperature of 150 ° C. to 300 ° C. and an oxygen concentration of less than 14%. Similarly, the opening degree of the first flow rate adjusting valve 14 and the third flow rate adjusting valve 25 is adjusted by the control device 12 and supplied to the biomass mill 6.

  Further, the biomass mill 6 is driven by the control device 12 and the first cut damper 17 is opened, and the woody biomass pulverized into fine biomass powder by the biomass mill 6 is transferred to the biomass. It is conveyed by a medium and supplied to the biomass burner 2 as the biomass stream 16.

  The biomass stream 16 supplied to the biomass burner 2 flows into the biomass conduction space 32 from a tangential direction, flows while flowing in the biomass conduction space 32 toward the tip, and turns to the tip of the biomass conduction space 32. Then, it is diffused by the swirler 33 and ejected into the furnace 1.

  At this time, pulverized coal combustion is performed by the pulverized coal burner 3 in the lower stage of the furnace 1, and the biomass fine powder is instantaneously gasified by ejecting the biomass fine powder to a high temperature region. It reacts with the carrier medium for biomass and the air left by pulverized coal combustion and burns (biomass combustion).

  At this time, since the biomass transport medium is as high as 150 ° C. to 300 ° C., even if the woody biomass contains water, the pulverization process in the biomass mill 6 or the biomass supply The fine biomass powder can be sufficiently dried in the course of transporting through the pipe 15 and being supplied to the biomass burner 2, and can be transported safely.

  The temperature of the biomass transport medium may be adjusted according to the moisture content of the woody biomass pulverized by the biomass mill 6.

  In addition, since the biomass transport medium has a low oxygen concentration of less than 14%, the biomass fine powder is prevented from spontaneously igniting in the biomass mill 6 or the biomass supply pipe 15. The

  After the biomass combustion by the biomass burner 2 is started, 100 cal. %, The combustion ratio of the pulverized coal burner 3 is gradually decreased in accordance with the combustion ratio of the biomass burner 2, and finally a part of the pulverized coal burner 3 is extinguished.

  When the supply of secondary air for pulverized coal combustion is stopped by extinguishing the pulverized coal burner 3, oxygen for performing biomass combustion in the furnace 1 may be insufficient. In this case, the amount of oxygen necessary for biomass combustion is ensured by supplying secondary air separately from the over air port 4. Moreover, you may make it supply oxygen required for biomass combustion by continuing the secondary air supply from the said pulverized coal burner 3 partially.

  FIG. 4A is a graph showing the volatilization process of the woody biomass 34 and pulverized coal 35 at 1400 ° C. in a 0% oxygen atmosphere. The woody biomass 34 is about 300 msec and almost all is vaporized (gas You can see that

  FIG. 4B is a graph showing the combustion process of the woody biomass 34 and the pulverized coal 35 in a 1200 ° C., 7.4% oxygen atmosphere until the pulverized coal 35 is completely burned out. While it takes 1300 msec or more, it can be seen that the woody biomass 34 is completely burned out in about 350 msec.

  Accordingly, the fine biomass powder injected into the furnace 1 that has been sufficiently heated is gasified in the furnace 1 in a short time, and the gasified biomass fine powder is reduced to a low oxygen atmosphere, for example, 7.4. Even in a% oxygen atmosphere, it can be burned completely in a short time.

  That is, since the biomass fine powder can be burned in the reducing atmosphere by the oxygen remaining in the secondary air after the pulverized coal burner 3 performs the pulverized coal combustion, In addition, it is not necessary to provide a mechanism for supplying secondary air for combustion, and the biomass burner 2 can be simplified and the manufacturing cost can be reduced.

  Further, since the biomass burner 2 is structured to supply only the biomass stream 16 into the furnace 1, it is not necessary to consider the difference in combustion characteristics between the pulverized coal 35 and the woody biomass 34, and the woody system The biomass 34 can be ejected in a large amount into the furnace 1.

  Further, by providing the biomass burner 2 on the upper stage side of the furnace 1 and providing the pulverized coal burner 3 on the lower stage side of the furnace 1, the amount of oxygen necessary for pulverized coal combustion and the pulverized coal 35 are completely burned. Biomass combustion can be performed while ensuring the necessary residence time until exhaustion.

  Further, in the boiler device 10 of the present embodiment, 100 cal. % Combustion ratio is gradually switched from pulverized coal combustion to biomass combustion with less NOx emission, so that the exhaust gas discharged from the furnace 1 can be reduced in NOx.

  In this example, 100 cal. % Pulverized coal combustion is gradually shifted to biomass combustion after the combustion ratio is secured. After preheating by oil combustion or gas combustion is completed, pulverized coal combustion and biomass combustion are started in parallel. Needless to say.

  In this embodiment, the biomass burner 2 is arranged in the upper stage and the pulverized coal burner 3 is arranged in the lower stage in order to ensure a sufficient amount of oxygen and residence time. When a large amount of oxygen and residence time are required for combustion of woody biomass, such as a large combustion ratio of pulverized coal is large, the pulverized coal burner 3 is disposed in the upper stage, and the biomass burner 2 is disposed in the lower stage. You may arrange.

DESCRIPTION OF SYMBOLS 1 Furnace 2 Biomass burner 3 Pulverized coal burner 4 Over-air port 6 Biomass mill 7 Pulverized coal mill 10 Boiler device 12 Controller 13 Primary air blowing duct 14 First flow control valve 15 Biomass supply pipe 20 Primary air 23 Flue 24 Exhaust gas Conduit 25 Third flow regulating valve 29 Burner support 31 Nozzle 33 Swirler

Claims (7)

  Provided on the furnace wall of the furnace, and having a nozzle part for ejecting biomass and a burner support part for supporting the nozzle part, the biomass is transferred to the nozzle part by a biomass transport medium in which exhaust gas is mixed with primary air. A biomass burner that is conveyed.   The biomass burner according to claim 1, wherein the biomass flows into the nozzle portion from a tangential direction.   The biomass burner according to claim 1 or 2, wherein a swirler is provided at a tip portion of the nozzle portion, and biomass is diffused by the swirler.   The biomass burner according to any one of claims 1 to 3 and a pulverized coal burner for burning pulverized coal are provided in at least two upper and lower stages, and a part of primary air is supplied to the pulverized coal burner. A primary air supply system that supplies the other part of the primary air to the biomass burner, and a part of the exhaust gas discharged from the furnace is extracted, and the primary air is extracted. A boiler apparatus comprising: an exhaust gas circulation system that is mixed with the other part and serves as a biomass transport medium for feeding biomass to the biomass burner.   The boiler apparatus according to claim 4, wherein the pulverized coal burner is provided in an upper stage, and the biomass burner is provided in a lower stage.   The apparatus further comprises a control device for controlling the combustion ratio of the biomass burner and the pulverized coal burner, and the control device maintains the combustion ratio of the furnace while increasing the combustion ratio of the biomass burner. The boiler apparatus of Claim 4 or Claim 5 which reduces the combustion ratio of.   The boiler device according to any one of claims 4 to 6, further comprising an over air port provided on the furnace wall and capable of supplying secondary air into the furnace.

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