JP2012112595A - Biomass and coal co-combustion system, and method of biomass and coal co-combustion - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a biomass and coal co-combustion system and a method of biomass and coal co-combustion, capable of efficiently discharging pulverized biomass powder to the outside.SOLUTION: This biomass and coal co-combustion system 10A includes a coal pulverizer 13 for pulverizing coal 16 to obtain the pulverized coal, a biomass and coal pulverizer 14 for mixing and pulverizing biomass 41 and coal 16 so that a mixing ratio of the coal 16 to biomass 41 satisfies that a mass of the coal 16 to the sum of mass of biomass 41 and coal 16 becomes 20 mass% or less to obtain biomass and coal mixture powder 42, a boiler furnace 15 to which the pulverized coal obtained by the coal pulverizer 13 and the biomass and coal mixture powder 42 obtained by the biomass and coal pulverizer 14 are supplied, and a combustion exhaust gas branch pipe 72 for supplying at least a part of a combustion exhaust gas 35 generated in the boiler furnace 15 to the biomass and coal pulverizer 14 from a combustion exhaust gas reflux pipe 71 for supplying the combustion exhaust gas to the boiler furnace 15.

Description

  The present invention relates to a biomass / coal co-firing system and a biomass / coal co-firing method including a co-firing boiler using biomass powder obtained by pulverizing biomass such as wood chips as fuel.

In recent years, CO ₂ emission reduction has been promoted from the viewpoint of global warming. In particular, fossil fuels such as coal and heavy oil are often used as fuel in combustion facilities such as power generation boilers, but this fossil fuel causes global warming due to the problem of CO ₂ emissions, thus preserving the global environment. Its use is being regulated from the viewpoint of In addition, from the viewpoint of depletion of fossil fuels, the development and commercialization of alternative energy resources are required. Therefore, as an alternative to fossil fuels, the use of fuel using biomass has been promoted. Biomass is an organic substance resulting from photosynthesis, and includes biomass such as wood, vegetation, crops, and moss. By converting this biomass into a fuel, the biomass can be effectively used as an energy source or an industrial raw material.

  From the viewpoint of highly efficient use of biomass, which is renewable energy, biomass is used as a fuel. One of the methods used as fuel is a method in which biomass solids are pulverized and pulverized and supplied to a pulverized coal-fired boiler for use as fuel. This is known as a single pulverization method in which coal and biomass are separately pulverized, and a mixed pulverization method in which coal and biomass are mixed and then pulverized.

  As an example of a coal-biomass mixed combustion system that pulverizes conventional biomass into a particle size for a coal-fired boiler and uses it as a fuel, a first pulverizer that performs single pulverization of biomass and single pulverization of coal or mixing of coal and biomass A second pulverizer that performs pulverization is provided, and pulverization is enabled while suppressing the pulverizer power while performing stable operation regardless of changes in biomass properties (see, for example, Patent Document 1).

In both the single pulverization method and the mixed pulverization method, when biomass solids such as woody biomass are pulverized and burned in a burner, there is a high possibility of spontaneous ignition, so normal temperature air or exhaust gas with low O ₂ concentration Had to be used. In addition, since the pulverization power of biomass solids is high, pulverized coal is usually pulverized to an average of several tens of μm, whereas in the case of biomass, it is the limit to pulverize biomass from 0.5 mm to 2 mm. there were. Therefore, when the biomass is burned with a burner, the ignitability of the biomass becomes poor, and normally the biomass is stably ignited and burned in the boiler by a flame of pulverized coal nearby.

JP 2008-82651 A

  However, in the conventional coal / biomass mixed combustion system, when the coal and biomass contain moisture, the coal and biomass conveyed to the boiler cannot be sufficiently dried, so that the boiler can stably ignite and burn. There is a problem that is difficult.

  The present invention has been made in view of the above, and an object of the present invention is to provide a biomass / coal mixed combustion system and a biomass / coal mixed combustion method capable of stably igniting and burning biomass with a boiler. .

  The first invention of the present invention for solving the above-described problems is a coal pulverization apparatus for pulverizing coal to obtain coal powder, and the mixing ratio of the coal to biomass is the mass of the biomass and the coal. The biomass and the coal are mixed and pulverized so that the mass of the coal is 20% by mass or less with respect to the sum, and a biomass / coal pulverization apparatus to obtain a biomass / coal mixed powder, and the coal pulverization apparatus A boiler furnace to which the obtained coal powder and the biomass / coal mixed powder obtained by the biomass / coal pulverizer are supplied, and the coal powder and the biomass / coal mixed in the boiler furnace. At least a part of flue gas generated by mixing and burning powder has a flue gas branch pipe fed to the biomass / coal pulverizer It is a biomass-coal co-firing system.

  2nd invention is the said coal powder with respect to the sum of the mass of the coal pulverization apparatus which pulverizes the said coal, and obtains coal powder, and the mixing ratio of the coal powder with respect to biomass is the said biomass and the said coal powder. Biomass / coal pulverization to obtain biomass / coal mixed powder by mixing and pulverizing the biomass and a part of the coal powder obtained by the coal pulverization apparatus so that the mass of the body becomes 20% by mass or less A boiler furnace supplied with the apparatus, the biomass-coal mixed powder obtained by the biomass-coal pulverizing apparatus, and the coal powder obtained by the coal-pulverizing apparatus, and the coal in the boiler furnace At least a part of the flue gas generated by mixing and burning the powder and the biomass / coal mixed powder has a flue gas branch pipe fed to the biomass / coal pulverizer. Is a biomass-coal co-firing system which is characterized.

  3rd invention has the biomass-coal mixed powder storage apparatus which stores the said biomass-coal mixed powder sent from the said biomass-coal crushing apparatus in 1st or 2nd invention, The said biomass The ratio (A / F) of the mass of air for conveying the biomass / coal mixed powder to the boiler furnace with respect to the mass of the biomass / coal mixed powder discharged from the coal mixed powder storage device is 0 It is a biomass and coal co-firing system that is .5 or less.

  A fourth invention is the biomass / coal mixed combustion system according to any one of the first to third inventions, wherein the coal powder is further mixed with coal ash.

  5th invention grind | pulverizes the said coal, obtains coal powder, and the mixing ratio of the said coal with respect to biomass will be 20 mass% or less with respect to the sum of the mass of the said biomass and the said coal. The biomass and the coal are mixed and pulverized to obtain a biomass / coal mixed powder, and the obtained coal powder and the biomass / coal mixed powder are supplied to a boiler furnace, and the boiler Supplying at least a part of combustion exhaust gas generated by mixing and burning the coal powder and the biomass-coal mixed powder in a furnace to the mixture of the biomass and the coal; It is a biomass-coal co-firing method characterized by being used for pulverization of coal.

  In a sixth aspect of the invention, the coal is pulverized to obtain coal powder, and the mixing ratio of the coal powder with respect to biomass is such that the coal powder is the sum of the mass of the biomass and the coal powder. The biomass and the coal powder are mixed and pulverized so as to be 20% by mass or less to obtain a biomass / coal mixed powder, and the obtained coal powder and the biomass / coal mixed powder are obtained. Supplying to a boiler furnace, at least a part of combustion exhaust gas generated by mixing and burning the coal powder and the biomass-coal mixed powder in the boiler furnace, the biomass and the coal powder This is a biomass-coal co-firing method characterized in that it is supplied to a mixture of the above and used for pulverization of the biomass and coal powder.

  In a fifth or sixth aspect of the invention, the seventh invention is directed to the transfer for the mass of the biomass / coal mixed powder when the biomass / coal mixed powder is transferred to the boiler furnace using transfer air. This is a biomass-coal mixed combustion method in which the air mass ratio (A / F) is 0.5 or less.

  An eighth invention is the biomass-coal mixed combustion method according to any one of the fifth to seventh inventions, wherein the coal powder is further mixed with coal ash.

  According to the present invention, biomass can be stably ignited and burned by a boiler.

FIG. 1 is a diagram simply showing the configuration of a biomass-coal mixed combustion system according to a first embodiment of the present invention. FIG. 2 is a diagram simply showing the configuration of the biomass-coal mixed combustion system according to the second embodiment of the present invention.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. The present invention is not limited by the contents described in the following examples. In addition, the constituent elements in the embodiments described below include those that can be easily assumed by those skilled in the art, those that are substantially the same, and those that are in the range of so-called averages. Furthermore, the constituent elements described below can be appropriately combined.

  A biomass-coal mixed combustion system according to a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a diagram simply showing the configuration of a biomass-coal mixed combustion system according to a first embodiment of the present invention. As shown in FIG. 1, the biomass / coal mixed combustion system 10 </ b> A includes a coal storage facility 11, a biomass storage facility 12, a coal pulverizer 13, a biomass / coal pulverizer 14, and a boiler furnace 15.

  Biomass is an organic resource derived from renewable organisms, excluding fossil resources. Examples of biomass include, but are not limited to, thinned wood, waste wood, driftwood, grass, waste, sludge, tires, and recycled fuel (pellets and chips) using these as raw materials. .

  The coal storage facility 11 stores coal 16 that is primarily crushed (coarsely crushed) to a predetermined particle size or less as necessary. Coal 16 roughly crushed in the coal storage facility 11 is fed to the coal crusher 13.

  The coal crusher 13 includes a hopper 21 a that receives the coal 16, and a crusher 22 a that crushes the coal 16 supplied from the coal storage facility 11. One or more crushers 22a are provided. The coal 16 supplied from the coal storage facility 11 is supplied to the hopper 21a. The coal 16 supplied to the hopper 21a is supplied from the hopper 21a to the pulverizer 22a through the raw material supply pipe 23a.

  The pulverizer 22a is for pulverizing the coal 16 supplied from the hopper 21a. For example, the pulverizer 22a is pulverized to a desired particle size of about several μm to several hundred μm to obtain coal powder (pulverized coal). is there. The pulverizer 22 a includes a housing 24, a pulverization table 25, a weir portion 26, and a pulverization roller 27.

  The housing 24 is formed in a cylindrical shape, and is connected to the raw material supply pipe 23a at the upper side in the vertical axis direction. In the housing 24, the coal 16 is supplied from the hopper 21a through the raw material supply pipe 23a from above in the vertical axis direction.

  The crushing table 25 is formed in a substantially circular trapezoidal shape, and is provided at the lower part of a cylindrical housing 24. The crushing table 25 is for placing the coal 16 that has passed through the raw material supply pipe 23 a and is supplied into the housing 24. Coal 16 is placed on the crushing table 25. The crushing table 25 is configured such that a motor (not shown) is connected to a drive shaft (not shown) extending from the lower side of the crushing table 25 and the crushing table 25 is driven to rotate by the motor. Yes. A reduction gear is connected to the motor, and the crushing table 25 is rotated at a low speed by the reduction gear. Further, the weir portion 26 is provided on the outer peripheral edge portion of the pulverizing table 25 so that an object to be pulverized can form a deposited layer having a predetermined thickness on the pulverizing table 25.

  The crushing rollers 27 are provided at positions that are located at equal intervals in the circumferential direction above the outer peripheral portion of the crushing table 25. The crushing roller 27 crushes the coal 16 of the crushing table 25 with a pressing force while rotating in conjunction with the rotation of the crushing table 25. The crushing roller 27 is supported so as to be rotatable around the end of the roller arm. The crushing roller 27 is connected to a variable hydraulic power source or a spring that changes the crushing load. Further, the variable hydraulic power source or the spring is connected to a control device (not shown). By adjusting the load of a variable hydraulic power source or a spring or the like by a control device, the pulverization load of the pulverization roller 27 is increased steplessly or stepwise so that the pulverization power is within a rated range, preferably substantially constant. The pressing force for pressing 16 is controlled.

  The raw material supply pipe 23 a is inserted into the top 24 a of the housing 24 in the vertical axis direction and is installed so as to drop the coal 16 onto the pulverization table 25. The coal 16 is supplied from the hopper 21a to the central portion of the crushing table 25 through the raw material supply pipe 23a. The coal 16 supplied to the central portion of the crushing table 25 moves on the crushing table 25 in the outer peripheral direction by centrifugal force, is caught by the crushing roller 27, and is crushed. By pulverizing the coal 16, pulverized coal is generated. The raw material supply pipe 23a is provided with a supply amount detector 28a for detecting the supply amount of the coal 16, and the supply amount of the coal 16 is adjusted.

  The pulverizer 22a is supplied with a carrier gas 31 from the lower part of the housing 24, and the carrier gas 31 is used for drying the pulverized coal generated in the pulverizer 22a. The pulverized coal pulverized to a desired particle size is conveyed outside the housing 24 by the carrier gas 31. The carrier gas 31 includes one or both of primary air 31a and primary air 31b. The primary air 31 a is sucked by the ventilator 33 from the outside air 32, transported by the primary air blower 34, and heat-exchanged by the combustion exhaust gas 35 discharged from the boiler furnace 15 and the air heater (AH) 36. is there. The primary air 31 b is the outside air 32 that is not heat-exchanged by the air heater 36. The bumpers 37a and 37b are air blowing means for adjusting the flow rates of the primary air 31a and 31b. The bumpers 37a and 37b form an upward flow of the carrier gas 18 from the lower side to the upper side of the pulverizing table 25 in the housing 24, and carry the pulverized coal in an air stream.

  A gap is provided between the outer peripheral edge of the pulverization table 25 and the inner peripheral surface of the housing 24, and the primary air 31 a and 31 b supplied from the lower part of the housing 24 passes through the gap to the pulverization table 25. Blows upward. A drift vane (not shown) or the like may be provided in the gap. The drift vane adjusts the blowing direction of the primary air, and may adjust the blowing direction of the primary air 31a and 31b. The angle of the drift vane may be arbitrarily controlled.

  Coarse pulverized coal among the pulverized coal conveyed to the upper portion of the housing 24 by the primary air 31a and 31b falls on the pulverization table 25 by gravity and is pulverized again. In addition, a classifier 38 is provided at the upper part of the housing 24, and the pulverized coal conveyed to the upper part of the housing 24 is classified again by the classifier 38. As the classifier 38, a fixed classifier or a rotary classifier is used. The pulverized coal having a particle size smaller than the predetermined particle size is carried out by the blown-up airflow, and is conveyed from the fuel supply nozzle 40a into the boiler furnace 15 through the discharge pipe 39a. A plurality of discharge pipes 39 a are provided in the circumferential direction of the top 24 a of the housing 24. Also, the pulverized coal larger than the predetermined particle size that has not penetrated the classifier 38 falls on the pulverization table 25 and is pulverized again to become pulverized coal smaller than the predetermined particle size, and then is conveyed into the boiler furnace 15. Is done. Thus, the pulverized coal obtained in the coal pulverizer 13 is conveyed to the boiler furnace 15.

  In the present embodiment, a case where a vertical grinder is used as the grinder 22a has been described. However, the present embodiment is not particularly limited to this, and for example, a crusher such as a tube mill, a ball mill, or a roller mill. Any type of coal that can pulverize the coal 16 can be used.

  In the present embodiment, only the coal 16 is supplied to the pulverizer 22a and the coal 16 is pulverized. However, the present embodiment is not limited to this. For example, the pulverizer 22a includes: In addition to the coal 16, coal ash such as clinker ash, cinder ash, fly ash, or the like may be supplied, and pulverized coal may be further mixed with coal ash. Thereby, pulverized coal and coal ash are conveyed from the grinder 22a to the boiler furnace 15. Further, the coal ash may be supplied to the discharge pipe 39 a and mixed with the pulverized coal conveyed to the boiler furnace 15.

  The biomass storage facility 12 stores the biomass 41 that is a primary solid (coarse) or dried biomass solid to a predetermined particle size or less as necessary. The biomass 41 stored in the biomass storage facility 12 is fed to the biomass / coal crusher 14. A part of the coal 16 stored in the coal storage facility 11 is fed to the biomass / coal crusher 14.

  The biomass / coal pulverization apparatus 14 includes a hopper 21b to which the biomass 41 and the coal 16 are supplied, and a pulverizer 22b for pulverizing the biomass 41 supplied from the biomass storage facility 12. The pulverizer 22b has the same configuration as the pulverizer 22a, and is a pulverizer that mixes and pulverizes the biomass 41 and the coal 16. One or a plurality of crushers 22b are provided.

  Coal 16 and biomass 41 are supplied to hopper 21b such that the mixing ratio of coal 16 to biomass 41 is 20% by mass or less of coal 16 with respect to the sum of the mass of biomass 41 and coal 16. Is done. The mixing ratio of the coal 16 with respect to the biomass 41 is preferably 16% by mass or less, and more preferably 10% by mass or less, with respect to the sum of the masses of the biomass 41 and the coal 16.

  When the biomass 41 and the coal 16 are mixed and pulverized at the same time, the coal 16 is easily pulverized and is pulverized more finely than the biomass 41 into pulverized coal. Biomass 41 is fibrous and soft, and is a hard-to-grind fuel compared to coal 16. However, since the coal 16 functions as an auxiliary agent when pulverizing the biomass 41 and the coal 16 improves the cutting efficiency of the biomass 41, the generation efficiency of biomass powder obtained by pulverizing the biomass 41 can be improved. it can. Therefore, by setting the mixing ratio of the coal 16 to the biomass 41 within the above range, when the biomass 41 and the coal 16 are mixed and pulverized at the same time, the coal 16 is pulverized into finer pulverized coal, Generation efficiency can be improved. Therefore, when the coal / biomass mixed powder 42 is ejected from the fuel supply nozzle 40 b into the boiler furnace 15, the pulverized coal is easily subjected to radiation in the boiler furnace 15, and the fine powder in the coal / biomass mixed powder 42. Charcoal and biomass powder can be easily ignited, and the flame can be stabilized. Moreover, since the temperature rise of biomass powder and discharge | release of the volatile matter contained in biomass powder can be accelerated | stimulated, combustion of biomass powder itself can also be accelerated | stimulated. Furthermore, the pulverization power required for pulverizing the biomass 41 and the coal 16 by the pulverization roller 27 in the hopper 21b can be reduced.

  The mixture of biomass 41 and coal 16 supplied to the hopper 21b is supplied from the hopper 21b to the grinder 22b. The pulverizer 22b has the same configuration as the pulverizer 22a. By supplying the mixture of biomass 41 and coal 16 to the pulverizer 22b, the mixture of biomass 41 and coal 16 supplied to the pulverizer 22b is mixed and pulverized by the pulverization table 25 and the pulverization roller 27. Biomass 41 becomes biomass powder, coal 16 becomes pulverized coal, and a coal / biomass mixed powder 42 containing biomass powder and pulverized coal is obtained. In addition, the raw material supply pipe 23b is provided with a supply amount detector 28b for detecting the supply amount of the mixture of the biomass 41 and the coal 16, and the supply amount of the mixture of the biomass 41 and the coal 16 is adjusted.

  The coal / biomass mixed powder 42 is fed from the pulverizer 22b to the biomass / coal mixed powder storage device 43 via the discharge pipe 39b. The biomass / coal mixed powder storage device 43 stores the coal / biomass mixed powder 42 supplied from the pulverizer 22b. The coal / biomass mixed powder 42 stored in the biomass / coal mixed powder storage device 43 is supplied into the boiler furnace 15 from the fuel supply nozzle 40 b through the discharge pipe 39 c using the transfer air 45. A plurality of fuel supply nozzles 40b are provided in the height direction of the furnace body 51 in the boiler furnace 15 in accordance with the number of pulverizers 22b. In this way, the coal / biomass mixed powder 42 obtained in the biomass / coal pulverizer 14 is conveyed to the boiler furnace 15. By supplying the coal / biomass mixed powder 42 into the boiler furnace 15, the biomass powder and pulverized coal contained in the coal / biomass mixed powder 42 are mixed and burned in the boiler furnace 15.

  The ratio of the mass of the conveying air 45 to the mass of the biomass / coal mixed powder 42 (A (air) / F (fuel)) is preferably 0.5 or less, more preferably 0.4 or less. More preferably, it is 0.3 or less. In the present embodiment, F (fuel) is a combination of biomass 41 and a coal raw material such as pulverized coal or coal. Usually, when only pulverized coal is used as pulverized fuel and transported to a boiler using transport air, the ratio of the mass of transport air to the mass of pulverized coal (A / F) is in the range of 2 to 3. is there. On the other hand, since the ratio of the mass of the carrier air 45 to the mass of the coal / biomass mixed powder 42 is 0.5 or less, the cooling by the carrier air 45 at normal temperature can be reduced. As a result, it is possible to easily raise the temperature using the primary air 31c.

  By setting the mixing ratio of the coal 16 to the biomass 41 within the above range, when the biomass 41 is pulverized, a predetermined amount of pulverized coal is included, and the pulverized coal is pulverized simultaneously with the biomass 41 to easily pulverize the coal 16. Is further finely pulverized, and when the coal / biomass mixed powder 42 is ejected into the boiler furnace 15 from the fuel supply nozzle 40b, the biomass powder in the coal / biomass mixed powder 42 is received by radiation in the boiler furnace 15. Can easily ignite and stabilize the flame. Moreover, the temperature rise of biomass powder, volatile matter discharge | release can be accelerated | stimulated, and subsequent combustion can also be accelerated | stimulated. Furthermore, the pulverization power of the mixture of the biomass 41 and the coal 16 by the pulverization roller 27 in the hopper 21b can be reduced.

  The coal / biomass mixed powder 42 remaining in the biomass / coal mixed powder storage device 43 is fed to the bag filter 46 by the combustion exhaust gas 35 a discharged from the boiler furnace 15 and remains in the bag filter 46. The mixed powder 42 is separated and removed from the combustion exhaust gas 35a. The coal / biomass mixed powder 42 separated by the bag filter 46 is supplied to the transfer air 45 and is supplied to the boiler furnace 15 along with the transfer air 45. Further, the combustion exhaust gas 35 a discharged from the bag filter 46 is mixed with the combustion exhaust gas 35 a discharged from the boiler furnace 15 and fed to the boiler furnace 15 as will be described later.

  The bag filter 46 only needs to separate the coal / biomass mixed powder 42 remaining in the combustion exhaust gas 35a from the combustion exhaust gas 35a, and examples of the bag filter 46 include a cyclone dust collector. Examples are not particularly limited thereto.

  In this embodiment, the pulverizer 22b is supplied with the coal 16 and the biomass 41, and the coal 16 and the biomass 41 are pulverized. However, the present embodiment is not limited to this example. In addition to the coal 16 and the biomass 41, coal ash such as clinker ash, cinder ash, and fly ash may be further supplied to the machine 22b, and the pulverized coal may be further mixed with coal ash. Thereby, pulverized coal, biomass 41, and coal ash are conveyed to the boiler furnace 15 from the grinder 22b. Further, the coal ash may be supplied to the discharge pipe 39b or the discharge pipe 39c and mixed with the pulverized coal conveyed to the boiler furnace 15.

  In the present embodiment, the coal / biomass mixed powder 42 is conveyed from the pulverizer 22b by the combustion exhaust gas 35a discharged from the boiler furnace 15, but the present embodiment is not limited to this. Instead of a part of the combustion exhaust gas 35a with the primary air 31a, 31b, the coal / biomass mixed powder 42 is conveyed from the pulverizer 22b by the combustion exhaust gas 35a and the primary air 31a, 31b. Good.

  The boiler furnace 15 includes a furnace body 51, combustion burners 52a and 52b, a wind box 53, a flue 54, and a heat transfer tube group 55. A plurality of combustion burners 52b are provided in the height direction of the furnace body 51 in accordance with the number of fuel supply nozzles 40b.

  In the present embodiment, the fuel supply nozzles 40a and 40b are provided corresponding to the pulverizers 22a and 22b, and are connected to the discharge pipes 39a and 39c, respectively. The fuel supply nozzles 40a and 40b are provided in the combustion burners 52a and 52b, respectively. The pulverized coal obtained by the pulverizer 22a is supplied into the boiler furnace 15 from the combustion burner 52a via the fuel supply nozzle 40a, and the coal / biomass mixed powder 42 obtained by the pulverizer 22b is supplied to the fuel supply nozzle 40b. To the boiler furnace 15 from the combustion burner 52b. Moreover, the primary air 31c heat-exchanged with the air heater 36 is supplied to the wind box 53, and is supplied in the boiler furnace 15 from each combustion burner 52a, 52b.

  The coal / biomass mixed powder 42 obtained in the biomass / coal pulverizing apparatus 14 and the pulverized coal obtained in the coal pulverizing apparatus 13 are separately supplied from the combustion burners 52a and 52b together with the primary air 31c in the boiler furnace 15. The coal / biomass mixed powder 42 and the pulverized coal are mixed and burned in the boiler furnace 15. The pulverized coal and the coal / biomass mixed powder 42 supplied into the boiler furnace 15 are combusted to generate combustion exhaust gas 35.

  A flue 54 is connected to the upper portion of the furnace body 51. The combustion exhaust gas 35 generated by combustion in the boiler furnace 15 is sent to the flue 54. A heat transfer tube group 55 is provided in the flue 42. The heat transfer tube group 55 is a convection heat transfer unit for recovering heat from the combustion exhaust gas 35. In the present embodiment, the heat transfer tube group 55 includes heaters 56a and 56b, evaporators 57a and 57b, and economizers 58a, 58b, and 58c. The combustion exhaust gas 35 generated by combustion in the boiler furnace 15 is heat-exchanged with water in the heat transfer tube group 55 to heat the heat transfer tube group 55.

  The flue 54 is connected to an exhaust gas pipe 60 from which the combustion exhaust gas 35 subjected to heat exchange is discharged. The exhaust gas pipe 60 is provided with a denitration device 61, an air heater 36, and an exhaust gas treatment facility 62. The combustion exhaust gas 35 subjected to heat exchange in the heat transfer tube group 55 is supplied to the denitration device 61. The denitration device 61 includes a reducing denitration catalyst. The combustion exhaust gas 35 is fed to the air heater 36 after harmful substances such as NOx contained in the combustion exhaust gas 35 are removed by the denitration device 61. In the air heater 36, the combustion exhaust gas 35 is heat-exchanged with the outside air 32 and is supplied to the exhaust gas treatment facility 62. The outside air 32 is desirably heated to a temperature in the range of 200 ° C. to 300 ° C. as the combustion air supplied to the primary air 31a and the combustion burners 52a and 52b supplied to the pulverizer 22b.

  The exhaust gas treatment facility 62 removes particulate matter and sulfur content contained in the combustion exhaust gas 35. In the present embodiment, the exhaust gas treatment facility 62 includes an electric dust collector 63 and a desulfurization device 64. The electric dust collector 63 is for removing particulate matter contained in the combustion exhaust gas 35. The combustion exhaust gas 35 is fed to the desulfurization device 64 by the blower 65 after the particulate matter contained in the combustion exhaust gas 35 is removed by the electric dust collector 63.

  The desulfurization device 64 is for removing sulfur contained in the combustion exhaust gas 35. Examples of the sulfur content include sulfur compounds such as hydrogen sulfide and carbonyl sulfide. The desulfurization device 64 may be any device that can remove sulfur contained in the combustion exhaust gas 35. As the desulfurization device, for example, the desulfurization device 64 is brought into contact with water and is contained in the combustion exhaust gas 35. An absorption tower that collects the sulfur content in water. After the sulfur content contained in the combustion exhaust gas 35 is removed by the desulfurization device 64, the combustion exhaust gas 35 is released from the chimney 66 into the atmosphere.

  In the present embodiment, the exhaust gas treatment facility 62 is configured to include the electric dust collector 63 and the desulfurization device 64, but the present embodiment is not limited to this, and according to the components contained in the combustion exhaust gas 35. An apparatus for removing components contained in the combustion exhaust gas 35 is appropriately provided. When the combustion exhaust gas 35 includes other components such as Hg, the exhaust gas treatment facility 62 may include a device that removes other components such as Hg.

  The primary air 31a generated by heating the outside air 32 by the air heater 36 and the primary air 31b not heated by the air heater 36 are supplied to the pulverizer 22a and used for classification and drying of pulverized coal. .

  A combustion exhaust gas recirculation pipe 71 is provided between the boiler furnace 15 and the denitration device 61. A part of the combustion exhaust gas 35 a discharged from the boiler furnace 15 is supplied to the boiler furnace 15 via the combustion exhaust gas recirculation pipe 71 and used for combustion of the coal / biomass mixed powder 42. The combustion exhaust gas recirculation pipe 71 is provided with a control valve V11. The supply amount of the combustion exhaust gas 35a to be fed is adjusted by opening / closing the control valve V11. Further, the combustion exhaust gas 35 a discharged from the bag filter 46 is supplied to the combustion exhaust gas recirculation pipe 71, mixed with the combustion exhaust gas 35 a, supplied to the boiler furnace 15, and used for combustion of the coal / biomass mixed powder 42. .

  The combustion exhaust gas recirculation pipe 71 is provided with a combustion exhaust gas branch pipe 72 that connects the combustion exhaust gas recirculation pipe 71 and the pulverizer 22b. Part or all of the combustion exhaust gas 35 a in the combustion exhaust gas recirculation pipe 71 is supplied to the pulverizer 22 b through the combustion exhaust gas branch pipe 72 by the combustion exhaust gas branch pipe 72. The combustion exhaust gas branch pipe 72 is provided with a control valve V12. The supply amount of the combustion exhaust gas 35a to be fed is adjusted by the opening / closing state of the control valve V12.

The combustion exhaust gas 35a supplied to the pulverizer 22b is used for pulverizing the coal 16 and the biomass 41, and for classifying and drying the coal / biomass mixed powder 42. If oxygen is contained in the carrier gas used for drying and transportation, spontaneous combustion may occur when the coal 16 and the biomass 41 are pulverized. Moreover, if the coal 16 and the biomass 41 contain moisture, the coal 16 and the biomass 41 may not be sufficiently dried even if air at room temperature is used. In contrast, the combustion exhaust gas 35a is a gas having a high temperature of 300 ° C. to 350 ° C. and containing a low concentration of O ₂ . A part or all of the combustion exhaust gas 35a is used for pulverizing the biomass 41 and the coal 16 and, when used for classification and drying of the coal / biomass mixed powder 42, spontaneous combustion is caused due to the biomass 41. In addition, the biomass 41 can be pulverized, and even if the coal 16 and the biomass 41 contain moisture, the pulverized coal and the biomass powder can be sufficiently dried.

  Thus, according to the biomass-coal mixed combustion system 10A according to the present embodiment, a predetermined amount of coal 16 is mixed with the biomass 41, and the combustion exhaust gas 35 discharged from the boiler furnace 15 is dried and the biomass 41 and the coal 16 are dried. By using the pulverized coal and biomass powder to be conveyed to the boiler furnace 15, it is possible to stably burn the biomass powder in the boiler furnace 15 regardless of the types and properties of the coal 16 and the biomass 41, and the coal 16 and The power required for pulverizing the biomass 41 can be reduced. For this reason, when operating the boiler furnace 15 using the coal 16 and the biomass 41 as fuel, the stability and reliability of the biomass-coal mixed combustion system 10A according to the present embodiment can be improved.

  A biomass / coal mixed combustion system according to a second embodiment of the present invention will be described with reference to the drawings. FIG. 2 is a diagram simply showing the configuration of the biomass-coal mixed combustion system according to the second embodiment of the present invention. In addition, the same code | symbol is attached | subjected to the same member as the structure of the biomass grinding | pulverization apparatus which concerns on Example 1, and the description is abbreviate | omitted. As shown in FIG. 2, the biomass / coal mixed combustion system 10 </ b> B according to the present embodiment uses the biomass / coal mixed combustion system 10 </ b> A according to the first embodiment to replace the pulverized coal discharged from the pulverizer 22 a with biomass 41 instead of the coal 16. And the hopper 21b. That is, the biomass-coal mixed combustion system 10B according to the present embodiment includes the pulverized coal feeding pipe 73 that feeds the pulverized coal discharged from the pulverizer 22a to the hopper 21a.

  Since pulverized coal is a finely pulverized powder than coal 16, when pulverized coal is mixed with biomass 41 and biomass 41 is mixed and pulverized simultaneously with pulverized coal, the pulverized coal is further improved in pulverization efficiency. In addition, the production efficiency of biomass powder can be further improved.

  For this reason, when pulverized coal and biomass powder are mixed and burned in the boiler furnace 15, the pulverized coal is a powder having a smaller particle size, so that the pulverized coal and biomass powder can be ignited more easily. The flame can be further stabilized. Moreover, since the temperature rise of biomass powder and discharge | release of the volatile matter contained in biomass powder are accelerated | stimulated, combustion of biomass powder itself can further be accelerated | stimulated. Furthermore, the pulverization power required for pulverizing the biomass 41 and the coal 16 in the hopper 21b can be further reduced.

  In each of the above embodiments, a system for co-firing biomass 41 and coal 16 has been described. However, the present invention is not limited to this, and a system for co-firing biomass 41 and pulverized fuel other than coal 16 is also applicable. The same applies.

  As described above, the biomass / coal mixed combustion system according to the present invention is a biomass / coal mixed combustion system that uses a mixed raw material in which biomass and coal are mixed, which facilitates ignition of the biomass raw material and enables power reduction of the pulverizer. Is suitable.

10A, 10B Biomass / coal co-firing system 11 Coal storage facility 12 Biomass storage facility 13 Coal crusher 14 Biomass / coal crusher 15 Boiler furnace 16 Coal 21a, 21b Hopper 22a, 22b Crusher 23a Raw material supply pipe 24 Housing 25 Crushing table 26 Weir part 27 Crushing rollers 28a, 28b Supply amount detector 31 Carrier gas 31a-31c Primary air 32 Outside air 33 Ventilator 34 Primary air blower 35, 35a Combustion exhaust gas 36 Air heater (AH)
37a, 37b Bumper 38 Classifier 39a, 39b Discharge piping 40a, 40b Fuel supply nozzle 41 Biomass 42 Coal / biomass mixed powder 43 Biomass / coal mixed powder storage device 45 Air for transport 46 Bag filter 51 Furnace body 52a, 52b Combustion Burner 53 Wind box 54 Flue 55 Heat transfer tube group 56a, 56b Heater 57a, 57b Evaporator 58a, 58b, 58c Eco-friendly economizer 60 Exhaust gas piping 61 Denitration device 62 Exhaust gas treatment equipment 63 Electric dust collector 64 Desulfurization device 65 Blower 71 Combustion exhaust gas Reflux pipe 72 Combustion exhaust gas branch pipe 73 Pulverized coal feed pipe S Coal B Biomass V11, V12 Control valve

Claims (8)

A coal crusher for crushing coal to obtain coal powder;
The biomass and the coal are mixed and pulverized so that the mixing ratio of the coal to the biomass is 20% by mass or less with respect to the sum of the masses of the biomass and the coal. A biomass-coal pulverizer to obtain coal-mixed powder;
A boiler furnace to which the coal powder obtained by the coal pulverizer and the biomass / coal mixed powder obtained by the biomass / coal pulverizer are supplied;
Combustion exhaust gas branching in which at least a part of the combustion exhaust gas generated by mixing and burning the coal powder and the biomass / coal mixed powder in the boiler furnace is fed to the biomass / coal pulverizer A biomass-coal co-firing system characterized by having a pipe. A coal crusher for crushing the coal and obtaining coal powder;
The mixing ratio of the coal powder to the biomass is obtained by the biomass and the coal pulverizer so that the mass of the coal powder is 20% by mass or less with respect to the sum of the mass of the biomass and the coal powder. And a part of the coal powder mixed and pulverized to obtain a biomass / coal mixed powder,
A boiler furnace to which the biomass / coal mixed powder obtained by the biomass / coal pulverization apparatus and the coal powder obtained by the coal pulverization apparatus are supplied;
Combustion exhaust gas branching in which at least a part of the combustion exhaust gas generated by mixing and burning the coal powder and the biomass / coal mixed powder in the boiler furnace is fed to the biomass / coal pulverizer A biomass-coal co-firing system characterized by having a pipe. In claim 1 or 2,
A biomass / coal mixed powder storage device for storing the biomass / coal mixed powder fed from the biomass / coal pulverization device;
The ratio (A / F) of the mass of air for conveying the biomass / coal mixed powder to the boiler furnace with respect to the mass of the biomass / coal mixed powder discharged from the biomass / coal mixed powder storage device is The biomass and coal co-firing system is 0.5 or less. In any one of Claims 1 thru | or 3,
A biomass / coal co-firing system in which coal ash is further mixed with the coal powder. The coal is pulverized to obtain a coal powder, and the mixing ratio of the coal with respect to biomass is 20% by mass or less with respect to the sum of the mass of the biomass and the coal. Coal and pulverize to obtain biomass / coal mixed powder,
Supply the obtained coal powder and the biomass-coal mixed powder to a boiler furnace,
Supplying at least a part of combustion exhaust gas generated by mixing and burning the coal powder and the biomass-coal mixed powder in the boiler furnace to the mixture of the biomass and the coal; And a method of co-firing biomass and coal, which is used for pulverizing coal. The coal is pulverized to obtain coal powder, and the mixing ratio of the coal powder to biomass is 20% by mass or less with respect to the sum of masses of the biomass and the coal powder. So that the biomass and the coal powder are mixed and pulverized to obtain a biomass-coal mixed powder,
Supply the obtained coal powder and the biomass-coal mixed powder to a boiler furnace,
Supplying at least a part of combustion exhaust gas generated by mixing and burning the coal powder and the biomass-coal mixed powder in the boiler furnace to the mixture of the biomass and the coal powder; A method for co-firing biomass and coal, which is used for pulverizing the biomass and coal powder. In claim 5 or 6,
When transferring the biomass-coal mixed powder to the boiler furnace using transfer air,
A biomass-coal mixed combustion method in which a ratio (A / F) of the mass of the conveying air to the mass of the biomass-coal mixed powder is 0.5 or less. In any one of Claims 5 thru | or 7,
A biomass-coal co-firing method in which coal ash is further mixed with the coal powder.

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