JP2012241971A - Biomass combusting boiler - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a biomass combustion boiler which improves both the safety and combustion efficiency of a boiler by decreasing uncombusted parts of biomass accumulated on a bottom hopper of a furnace in a biomass combusting boiler.SOLUTION: The biomass combusting boiler combusts using biomass as fuel, and generates steam with heat generated by combustion. The boiler has a heat conductive pipe for conducting heat generated by combustion to steam above the furnace of itself, and also has a bottom hopper at the bottom of the furnace of the boiler. A multistage burner which combusts biomass is arranged at the lower part of the furnace of the boiler, and an opening is formed on the wall face of the furnace at a position lower than the lowest stage burner of the multistage burner, and a fluid spraying apparatus equipped with a jet for spraying fluid is installed in such a manner that it can be inserted into the furnace from the opening, so that an incombustible fluid can be sprayed toward the bottom hopper at the bottom of the furnace from the fluid spraying apparatus.

Description

  The present invention relates to a biomass combustion boiler that burns biomass fuel, and a biomass combustion boiler that mixes and burns pulverized coal and biomass.

In apparatuses that produce energy by combustion, such as industrial boilers, business boilers, and various turbines, fossil fuels such as coal and heavy oil are often used as fuel. In recent years, since the reduction of CO2 emissions in terms of global warming has been promoted, the CO ₂ much discharged, fossil fuels to promote global warming, while their use is restricted from the standpoint of global environmental conservation .

  Therefore, the use of biomass is promoted as an alternative to fossil fuels. Biomass is classified as woody, vegetation, or sludge, and is a clean and recyclable carbonaceous resource. By using this biomass as a fuel, it can be effectively used as an energy source or an industrial raw material.

  Biomass fuel is significantly improved in ignitability and combustibility by drying, but is not a brittle material such as coal, so it is difficult to atomize and pulverize compared to coal. While the average particle size of pulverized coal used in conventional coal combustion equipment is several tens of μm, biomass fuel can be used even with equipment that has a pulverization capacity equivalent to or better than that of pulverization equipment that pulverizes coal. The degree of pulverization is about 1 mm in average particle size.

  Therefore, the biomass itself is sufficiently good in ignitability and combustibility if dried, but because of its large particle size, when it is supplied in large quantities as a fuel to the combustion device, it becomes less ignitable than coal particles. . Therefore, there arises a problem that the unburned portion of the biomass fuel increases in the combustion furnace, and the CO and NOx concentrations in the furnace increase.

  Moreover, since the biomass fuel has a large particle size, it falls without being able to float after being supplied to the combustion furnace. Due to the fall of the biomass to the bottom of the furnace, there arises a problem that the combustion efficiency is lowered.

  Many methods have been proposed so far to prevent unburned and falling biomass fuel.

  For example, in the technology disclosed in Japanese Patent Application Laid-Open No. 2007-101135, biomass fuel is burned by placing a burner that burns biomass above a burner that burns pulverized coal, and using the blow-up of the flame of the pulverized coal burner. The floating time in the furnace is increased.

  Ideally, even with large particle size biomass fuel, when it descends to the bottom of the furnace due to the extension of the floating time, it is ideally completely ash, but it is less than 3-5mm in size when it burns completely and becomes ash. . More particles release volatiles and moisture, and some of the fixed carbon also burns, but a significant proportion of unburned material falls to the bottom of the furnace and accumulates in the bottom hopper.

  In normal boiler operation, the temperature at the bottom of the furnace is low and the accumulated biomass fuel cannot be combusted. For this reason, the amount of unburned biomass on the bottom hopper increases with time. When the gas concentration distribution or temperature in the furnace changes due to an abnormality in the boiler equipment, a large amount of unburned biomass begins to burn rapidly, and the furnace wall may be damaged due to an increase in the thermal load at the bottom of the furnace. There is sex.

JP 2007-101135 A

  In a biomass combustion boiler that mixes and burns pulverized coal and biomass described in JP 2007-101135 A and a biomass combustion boiler that burns biomass fuel, in order to promote the use of biomass fuel, the biomass fuel is supplied to the boiler furnace. It is necessary to increase the supply amount.

  However, when the biomass fuel supply amount is increased in the biomass combustion boiler, it is inevitable that a large amount of unburned biomass accumulates in the bottom hopper of the boiler furnace. And if there is a fluctuation in the gas concentration distribution or temperature in the furnace due to some abnormality in the boiler equipment, and a large amount of unburned biomass accumulated in the bottom hopper burns rapidly, an increase in the thermal load at the bottom of the furnace It may lead to furnace wall damage.

  An object of the present invention is to provide a biomass combustion boiler that reduces both unburned biomass accumulated in the bottom hopper of a biomass combustion boiler furnace and improves both boiler safety and combustion efficiency when burning biomass fuel as fuel. It is to provide.

  The biomass combustion boiler of the present invention is a biomass combustion boiler that burns coal and biomass or only biomass as fuel and generates steam by the heat generated by the combustion, and heat generated by the combustion is generated in the upper part of the boiler furnace. A heat transfer tube is provided to transmit steam, and a bottom hopper is provided at the bottom of the boiler furnace, and a multistage burner for burning coal and biomass or biomass is installed at the bottom of the boiler furnace. An opening is provided in the furnace wall surface at a position lower than the lower burner, and a fluid spraying device having an injection port for spraying fluid is installed so as to be inserted into the furnace from the opening, and from the fluid spraying device to the bottom of the furnace It is configured to spray a nonflammable fluid toward the bottom hopper.

  According to the present invention, when biomass fuel is burned as fuel, the biomass unburned matter accumulated in the bottom hopper of the furnace of the biomass combustion boiler is effectively reduced, and both the safety and the combustion efficiency of the boiler are improved. A biomass combustion boiler can be realized.

BRIEF DESCRIPTION OF THE DRAWINGS The whole figure which shows schematic structure of the biomass combustion boiler which is 1st Example of this invention. Schematic which shows the tube which sprays the nonflammable fluid with which the fluid spraying apparatus used for the biomass combustion boiler of the Example described in FIG. 1 was equipped. Schematic which shows the condition which inserts the fluid spraying apparatus used for the biomass combustion boiler of the present Example described in FIG. 1 with respect to a furnace. Schematic which shows the part of the furnace bottom part of the biomass combustion boiler of the present Example described in FIG. The solid fuel distribution map which shows the distribution condition of the solid fuel in the bottom hopper upper end position of the biomass combustion boiler to which this invention is applied. Schematic which shows the tube which sprays the combustible fluid with which the fluid spraying apparatus used for the biomass combustion boiler which is 2nd Example of this invention was equipped. Schematic which shows the operating method of the fluid spraying apparatus in the furnace bottom part of the biomass combustion boiler of the Example shown in FIG.

  Next, a biomass combustion boiler according to an embodiment of the present invention will be described below with reference to the drawings.

  The biomass combustion boiler which is 1st Example of this invention is demonstrated using FIG.

  As shown in FIG. 1, in the biomass combustion boiler of this embodiment, the boiler body is mainly composed of a furnace 1 and a rear heat transfer surface 2 following the furnace 1. A heat transfer tube group 5 corresponding to a superheater, a reheater, and a economizer is installed from the upper part of the furnace 1 to the rear heat transfer surface 2. A soot blower 14 is provided around the heat transfer tube group 5 to remove ash adhering to the heat transfer tube group 5 during boiler operation.

  A pulverized coal burner 3 for burning pulverized coal over a plurality of stages and a biomass burner 4 for burning biomass fuel as fuel are installed on the furnace wall surface at the lower part of the furnace 1, respectively. Fuel is injected into the furnace 1 from the pulverized coal burner 3 or the biomass burner 4 together with the combustion air supplied from the combustion air supply means 6 and combusts in the furnace 1.

  And the combustion gas produced | generated by burning solid fuels, such as coal and biomass, in the furnace 1 is heat-exchanged with the heat exchanger tube group 5 in the middle of passing the rear heat-transfer surface 2 from the furnace 1, and these heat transfer is carried out. After flowing down the heat pipe group 5, it flows down from the boiler through the exhaust gas duct 7, and is discharged into the atmosphere after being subjected to exhaust gas treatment in a downstream exhaust gas treatment facility.

  The high-temperature steam generated by heat exchange in the heat transfer tube group 5 is supplied to a steam turbine (not shown) to drive the steam turbine.

  The pulverized coal supplied to the pulverized coal burner 3 installed in the furnace 1 of the pulverized coal cooking boiler apparatus is made by pulverizing the coal conveyed from the coal bunker 8 by the coal mill 9. Moreover, the biomass supplied to the biomass burner 3 installed in the furnace 1 is made by pulverizing the biomass conveyed from the biomass bunker 10 with the biomass mill 11.

  The biomass combustion boiler of the present embodiment is not limited to a biomass combustion boiler in which coal and biomass are mixed and burned, and can also be applied to a biomass-fired boiler that supplies only biomass into the furnace and burns it.

  In the biomass combustion boiler of the present embodiment, a plurality of openings 13 for inserting the fluid spraying device 12 into the furnace 1 are provided at positions on the furnace wall surface lower than the pulverized coal burner 3 installed in the furnace 1. Yes.

  Coal to be used as fuel is supplied from the coal bunker 8 to the coal mill 9, pulverized to a particle size of several tens to several hundreds μm, and then supplied into the furnace 1 from the pulverized coal burner 3 installed on the wall surface of the furnace 1. Burn. On the other hand, the biomass fuel is supplied from the biomass bunker 10 to the biomass mill 11, pulverized to a particle size of several tens of mm or less, supplied to the furnace 1 from the biomass burner 4 installed on the wall surface of the furnace 1, and burned.

  Here, only the case of using the biomass mill 11 that pulverizes the biomass alone will be described, but a coal / biomass mixed mill that pulverizes and pulverizes coal and biomass may be used. A plurality of coal mills 9, biomass mills 11, and coal / biomass mixing mills may be used.

  Of the biomass supplied from the biomass burner 4 to the furnace 1, those having a small particle size are blown up by the combustion gas in the furnace and discharged from the exhaust gas duct 7 to the outside of the furnace.

  On the other hand, biomass having a large particle size is ejected from the biomass burner 4 into the furnace 1 and then falls, and reaches the bottom hopper 15 at the bottom of the furnace 1. The falling biomass is burned by the combustion flame and radiant heat of pulverized coal and small particle size biomass, so that part of it is completely burned out to reach the bottom hopper 15 and becomes ash, but the rest is as biomass unburned 16 Deposit on the bottom hopper 15.

  The biomass unburned portion 16 deposited on the bottom hopper 15 is removed by the fluid spraying device 12 inserted into the furnace 1 through the opening 13 formed on the wall surface of the furnace 1. A method for removing the unburned biomass 16 deposited on the bottom hopper 15 will be described with reference to FIGS.

  2 and 3, the fluid spraying device 12 installed in the biomass combustion boiler of the present embodiment includes a tube 17 through which a fluid flows, an injection port 18 for spraying the fluid, and a rotation and insertion of the tube 17. It is comprised from the drive device (not shown) moved to the front and back along a direction.

  Further, the fluid spraying device 12 includes a pressure detector 19 constituting a pressure adjusting mechanism capable of adjusting the pressure and flow rate of the fluid sprayed from the ejection port 18, and the pressure and flow rate of the fluid detected by the pressure detector 19. Pressure control valve controller 21 for calculating the pressure and flow rate of the fluid sprayed from the injection port 18 and outputting a command signal for the calculated fluid pressure and flow rate to the pressure control valve 20, and the force control valve The pressure regulating valve 20 operated by the control device 21 is provided.

  The fluid spraying device 12 has a structure similar to the soot blower 14 used in a conventional pulverized coal boiler, and may be modified by diverting the soot blower 14.

  As the fluid sprayed from the tube 17 of the fluid spraying device 12, steam, air, other nonflammable fluid, or a mixed fluid of these plural fluids is used. The fluid flowing through the tube 17 constituting the fluid spraying device 12 is injected from the injection port 18 formed in the tube 17 toward the bottom hopper 15 at the bottom of the furnace 1, and the unburned biomass 16 deposited on the bottom hopper 15 is removed from the furnace 1. Remove by burning in.

  That is, by spraying a nonflammable fluid from the tube 17 of the fluid spraying device 12 toward the bottom hopper 15 at the bottom of the furnace 1, the biomass unburned portion 16 deposited on the bottom hopper 15 at the bottom of the furnace 1 has a high temperature. The gas is blown upward in the furnace 1 and the combustion of the unburned biomass 16 is promoted.

  FIG. 3 explains the configuration of the fluid spraying device 12 used in the biomass combustion boiler which is the embodiment of FIG. 1 and the state of operation thereof. The tube 17 of the fluid spraying device 12 to the furnace 1 is connected to the furnace 1. It is a perspective view which shows the state inserted in the inside.

  In the biomass combustion boiler of the present embodiment shown in FIG. 3, the fluid spraying devices 12 are respectively installed in the vicinity of the openings 13 formed in the left and right furnace walls constituting the wall surface of the furnace 1, and from both directions of the left and right furnace walls. Tubes 17 constituting the fluid spraying device 12 are respectively inserted into the furnace 1 through the openings 13.

  The fluid spraying device 12 has a structure in which an injection port 18 formed in the tube 17 can rotate around the axis of the tube 17, and the furnace 1 rotates while rotating from the furnace wall side of the furnace 1 to the center of the furnace 1. Move to the center of. Then, an incombustible fluid is injected from the injection port 18 formed in the tube 17 toward the biomass unburned portion 16 deposited on the bottom hopper 15 at the bottom of the furnace 1.

  When a plurality of the fluid spraying devices 12 are installed, each fluid spraying device 12 is configured to be capable of operation control independently.

  Since the fluid spraying device 12 is used by inserting the tube 17 for injecting the fluid into the furnace 1, there is a possibility that the tube 17 may be damaged if the tube 17 is inserted in a time zone when there are few falling objects in the furnace. Lower. The amount of falling objects in the furnace increases during operation of the soot blower 14 or during a change in plant load.

  For this reason, the fluid spraying device 12 of the present embodiment operates the soot blower 14 installed at the upper part of the furnace 1, the load change of the plant is finished, and the deposits on the heat transfer tube group 5 are transferred to the bottom of the furnace. In the time zone after falling to the furnace 1, the fluid spraying device 12 is operated through the opening 13 formed in the furnace wall of the furnace 1 to insert the tube 17 of the fluid spraying device 12 into the furnace 1. The incombustible fluid is injected from the injection port 18 toward the unburned biomass 16 deposited on the bottom hopper 15 at the bottom of the furnace 1.

  Then, by injecting an incombustible fluid from the injection port 18 of the tube 17, the unburned biomass 16 deposited on the bottom hopper 15 at the bottom of the furnace 1 is blown up above the high-temperature furnace, and the unburned biomass 16 is discharged. Burn.

  By the way, in order to insert the fluid spraying apparatus 12 of the biomass combustion boiler of the present embodiment into the furnace 1, parameters for setting a suitable position of the opening 13 provided on the wall surface of the furnace 1 are shown in FIG. .

  The position of the opening 13 into which the fluid spraying device 12 is inserted can be expressed using two parameters a and d shown in FIG. Parameter a is the distance from the slope of the bottom hopper 15 at the bottom of the furnace 1 to the opening 13, and parameter d is the horizontal distance from the upper end of the bottom hopper 15 to the opening 13.

  Next, FIG. 5 shows a solid fuel distribution diagram which is a distribution of the amount of falling solid fuel obtained from the combustion analysis in the furnace 1 of the biomass combustion boiler. In the analysis, the analysis was performed by setting a case where solid particles having a maximum particle size of 7 mm were introduced into the furnace.

  As shown in the solid fuel distribution diagram of FIG. 7, when the horizontal distance from the upper end to the lower end of the bottom hopper 15 at the bottom of the furnace 1 is D, the distribution of the solid fuel is high at the center of the furnace 1, and 0.4 <d From the numerical analysis, it was found that the fall of the solid fuel in the region of /D<1.0 is 80% or more of the total fall amount of the solid fuel.

  From this, in the biomass combustion boiler of the present embodiment, the position d of the opening 13 provided on the wall surface of the furnace 1 for inserting the fluid spraying device 12 is set in a range of 0.4D <d <D. The biomass combustion boiler is operated so that the removal effect of the unburned biomass 16 deposited on the bottom hopper 15 at the bottom of the furnace 1 is enhanced.

  Since the fluid spraying device 12 is a device similar to the soot blower 14, it is estimated that the range in which the biomass unburned portion 16 can be removed using the fluid spraying device 12 is at most within a radius of 3 m from the injection port 18. Therefore, the distance a from the slope of the bottom hopper 15 of the opening 13 is preferably set to 0 <a <3 m.

  As described above, according to this embodiment, when biomass fuel is burned as fuel, the biomass unburned matter accumulated in the bottom hopper of the furnace of the biomass combustion boiler is reduced, and the safety and combustion efficiency of the boiler are reduced. An improved biomass combustion boiler can be realized.

  Next, the biomass combustion boiler which is 2nd Example of this invention is demonstrated using FIG.6 and FIG.7.

  The biomass combustion boiler of the present embodiment has the same basic configuration as the biomass combustion boiler of the previous embodiment shown in FIGS. Only will be described.

  FIG. 6 shows the structure of the tube 17 used in the fluid spraying device 12 installed in the biomass combustion boiler according to this embodiment. In this embodiment, a flammable fluid such as oil or gas is used as the spray medium of the spray fluid device 12. The flow path in the tube 17 is divided into two, and the combustible fluid flows through the flow path (flow path 1) inside the tube 17.

  Air is passed through the flow path 2 located outside the flow path 1 to prevent the temperature of the inner flow path 1 from increasing. Two types of fluids flowing through the tube 17 are sprayed from the injection port 18 toward the biomass unburned portion 16 deposited on the bottom hopper 15 at the bottom of the furnace 1.

  The combustible fluid sprayed from the tube 17 of the spray fluid device 12 into the high-temperature furnace 1 is combusted in the furnace 1, and the unburned biomass 16 deposited on the bottom hopper 15 at the bottom of the furnace 1 is heated by the heat of the combustion flame. Burn.

  In the biomass combustion boiler of the present embodiment, FIG. 7 shows a suitable fluid spraying form sprayed from the tube 17 of the spray fluid device 12 into the furnace 1. The opening 13 formed in the furnace wall of the furnace 1 is provided at a position near the lower end of the bottom hopper 15. The tube 17 of the spray fluid device 12 is inserted into the furnace 1 with the injection port 18 oriented in a direction parallel to the inclination of the bottom hopper 15 (the direction of the arrow in FIG. 5). After that, the tube 17 of the spray fluid device 12 is not rotated, but the tube 17 is moved and inserted into the furnace 1 while the direction of the injection port 18 of the tube 17 is fixed.

  A combustible fluid sprayed from an injection port 18 formed in the tube 17 of the spray fluid device 12 toward the biomass unburned portion 16 deposited on the bottom hopper 15 at the bottom of the furnace 1 just as indicated by an arrow 25 in FIG. The combustion flame formed by the above causes the unburned biomass 16 deposited on the bottom hopper 15 to burn without contacting the furnace wall of the furnace 1.

  As described above, according to the present embodiment, when biomass fuel is burned as fuel, the unburned biomass accumulated in the bottom hopper of the furnace of the biomass combustion boiler is reduced, so that both the safety and the combustion efficiency of the boiler are achieved. An improved biomass combustion boiler can be realized.

  The present invention is applicable to a biomass combustion boiler that burns biomass fuel and a biomass combustion boiler that mixes and burns pulverized coal and biomass.

  1: furnace, 2: rear heat transfer surface, 3: pulverized coal burner, 4: biomass burner, 5: heat transfer tube group, 7: exhaust gas duct, 8: coal bunker, 9 coal mill, 10: biomass bunker, 11: biomass Mill: 12: Fluid spraying device, 13: Opening part, 14: Soot blower, 15: Bottom hopper, 16: Unburned biomass, 17: Tube, 18: Injection port, 19: Fuel supply pipe, 20: Pressure detector, 21 : Pressure regulating valve, 22: Pressure regulating valve control device.

Claims (8)

  A biomass-fired boiler that burns coal and biomass, or only biomass, as fuel, and generates steam from the heat generated by the combustion. A heat transfer tube that transfers the heat generated by the combustion to the steam is provided at the upper part of the boiler furnace. A bottom hopper at the bottom of the boiler furnace, a multistage burner for burning coal and biomass, or biomass is installed at the bottom of the boiler furnace, and the furnace at a lower position than the lowest burner of the multistage burner A fluid spraying device provided with an opening on the wall surface and provided with an injection port for spraying fluid is installed so as to be insertable into the furnace from the opening, and the fluid is sprayed from the fluid spraying device toward a bottom hopper at the bottom of the furnace. A biomass fired boiler configured as described above. In the biomass combustion boiler according to claim 1,
The fluid spraying device is provided with a tube for supplying fluid and spraying the fluid in a furnace, and a fluid injection port for spraying the fluid into the furnace is formed in the tube. The tube is configured to be movable so that the tube can be inserted into the furnace from the opening, and the tube is configured to be rotatable about the insertion direction as a central axis so that the position and direction of the injection port can be changed. A biomass-fired boiler characterized by that. In the biomass combustion boiler according to claim 1,
The fluid sprayed from the fluid spraying device uses a non-combustible fluid such as steam or air. In the biomass combustion boiler according to claim 1,
The fluid spraying device includes a pressure detector that detects a pressure of a fluid to be sprayed, an adjustment valve that can adjust a pressure and a flow rate of the fluid to be sprayed, and the adjustment based on a pressure value of the fluid detected by the pressure detector. A biomass-fired boiler comprising a control device for adjusting the opening of a valve. In the biomass combustion boiler according to claim 1,
A soot blower for removing deposits on the surface of the heat transfer tube is installed near the heat transfer tube in the upper part of the furnace of the boiler, and after the soot blower is operated in the fluid spraying device, the load of the biomass combustion boiler is changed. A biomass combustion boiler configured to insert a tube for spraying a fluid provided in the fluid spraying device into the furnace through an opening and spray the fluid into the furnace. In the biomass combustion boiler according to claim 1,
A biomass combustion boiler characterized by using a combustible fluid and air as fuel as the fluid sprayed from the fluid spraying device. In the biomass combustion boiler according to claim 1,
When the horizontal distance from the upper end to the lower end of the bottom hopper at the bottom of the furnace is D and the horizontal distance from the upper end of the bottom hopper to the opening is d, the installation position of the opening is 0.4D <d <D. A biomass-fired boiler characterized by being set to be in a range. In the biomass combustion boiler according to claim 7,
A biomass combustion boiler, wherein the installation position a of the opening is set in a range of 0 <a <3 m, where a is the distance from the bottom hopper slope at the bottom of the furnace to the opening 13.

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