Combustion System

Abstract

To reduce the cost required for treating exhaust gas generated by blasting.SOLUTION: A combustion system 100 includes a reactor 310 for pressurizing biomass at a pressure exceeding the atmospheric pressure, a heating section 320 for heating the reactor 310, a solid-gas separator 340 for separating a solid-gas mixture containing the biomass and discharged from the reactor 310 into solid and gas, a combustor (boiler 190) for burning the biomass separated by the solid-gas separator 340, a cooler 210 for cooling exhaust gas separated by the solid-gas separator 340, and an exhaust gas supply section 230 for supplying the exhaust gas after being cooled by the cooler 210 to the combustor.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to combustion systems. [Background technology]

[0002] In recent years, there has been a demand to reduce CO2 (carbon dioxide) emissions in order to prevent global warming. For this reason, technologies to burn biomass in addition to coal or instead of coal in boilers are being considered. In order to burn biomass in a boiler, the biomass needs to be pulverized.

[0003] As a technology for pulverizing biomass, a technology has been developed in which biomass and steam are introduced into a sealed container, pressurized, and then rapidly depressurized to steam explode the biomass (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 1989-1989 Summary of the Invention [Problem to be solved by the invention]

[0005] In the steam explosion technology, the exhaust gas generated by the explosion contains carbon monoxide. Carbon monoxide is toxic, so the exhaust gas needs to be treated to make it harmless. Therefore, there is a need to develop a technology that reduces the cost required to treat the exhaust gas generated by the explosion.

[0006] In view of the above problems, the present disclosure aims to provide a combustion system that can reduce the cost required for treating exhaust gas generated by explosion. [Means for solving the problem]

[0007] In order to solve the above problems, a combustion system according to one embodiment of the present disclosure includes a reactor that pressurizes biomass to a pressure higher than atmospheric pressure, a heating unit that heats the reactor, a solid-gas separator that separates a solid-gas mixture containing biomass discharged from the reactor into solid and gas, a combustor that combusts the biomass separated by the solid-gas separator, a cooler that cools the exhaust gas separated by the solid-gas separator, and an exhaust gas supply unit that supplies the exhaust gas cooled by the cooler to the combustor.

[0008] The combustion system may also include a transport path for airflow transporting the biomass separated by the solid-gas separator to the combustor, and the exhaust gas supply unit may include a buffer tank for storing exhaust gas, a communication passage connecting the buffer tank and the transport path, and a valve provided in the communication passage.

[0009] The combustor may be a boiler, and the combustion system may include a power generation device that generates electricity using steam generated by the boiler, and a control unit that controls the opening degree of the valve based on the power generation efficiency of the power generation device.

[0010] The heating section may also heat the outer wall of the reactor. [Effects of the Invention]

[0011] According to the present disclosure, it is possible to reduce the cost required for treating exhaust gas generated by explosion. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a diagram illustrating a combustion system according to this embodiment. [Figure 2] FIG. 2 is a diagram illustrating the crushing device according to this embodiment. [Figure 3] FIG. 3 is a diagram showing the weight balance of the solid-gas mixture after explosion. [Figure 4] FIG. 4 is a diagram showing the composition of exhaust gas. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. Dimensions, materials, specific numerical values, etc. shown in the embodiments are merely examples for ease of understanding and do not limit the present disclosure unless otherwise specified. In this specification and drawings, elements having substantially the same functions and configurations are designated by the same reference numerals to avoid redundant explanation, and elements not directly related to the present disclosure are not shown.

[0014] [Combustion System 100] FIG. 1 is a diagram illustrating a combustion system 100 according to this embodiment. In FIG. 1, solid arrows indicate the flow of biomass and liquid. In FIG. 1, dashed arrows indicate the flow of gas. In FIG. 1, dashed arrows indicate the flow of signals.

[0015] As shown in FIG. 1, the combustion system 100 includes a supply device 110, a pulverizer 120, a first conveying device 130, a dryer 140, a classifier 150, a second conveying device 160, a post-drying hopper 170, a conveying path 180, a boiler 190, a power generation device 200, a cooler 210, a distillation device 220, an exhaust gas supply unit 230, and a control unit 240.

[0016] The combustion system 100 grinds the biomass and combusts it in a boiler 190 .

[0017] The biomass is one or more of woody biomass, herbaceous biomass, and waste biomass. Woody biomass includes, for example, wood chips, sawdust, and bark. Herbaceous biomass includes, for example, wheat straw and rice straw. Waste biomass includes, for example, empty fruit bunches (EFBs), palm kernel shells (PKS), and grain and fruit pomace that are generated as a result of producing palm oil from palm trees.

[0018] The feeder 110 feeds biomass to the grinder 120. The feeder 110 includes an receiving conveyor 112, a receiving hopper 114, and a weigh feeder .

[0019] The receiving conveyor 112 transports the biomass to the receiving hopper 114. The receiving hopper 114 temporarily stores the biomass. The receiving hopper 114 is provided with a screw conveyor 114a. The screw conveyor 114a transports the biomass stored in the receiving hopper 114 to a weigh feeder 116. The weigh feeder 116 supplies a predetermined amount of biomass to the crushing device 120.

[0020] Fig. 2 is a diagram illustrating the pulverizer 120 according to this embodiment. In Fig. 2, solid arrows indicate the flow of biomass and liquid, and dashed arrows indicate the flow of gas.

[0021] The pulverizer 120 steam explodes (steam-explodes) the biomass. As shown in FIG. 2, the pulverizer 120 includes a reactor 310, a heating section 320, a communicating pipe 330, and a solid-gas separator 340.

[0022] The reactor 310 pressurizes the biomass to a pressure in a predetermined range above atmospheric pressure. The reactor 310 includes an enclosed vessel 312 and an agitator 314.

[0023] The sealed container 312 includes a container body 312a, a lid 312b, and an on-off valve 312c. The container body 312a contains the biomass supplied by the supply device 110. The container body 312a is cylindrical. In this embodiment, the upper part of the container body 312a is cylindrical with a central axis in the vertical direction, and the lower part is conical with a central axis in the vertical direction. The central axis of the upper part (cylindrical shape) of the container body 312a coincides with the central axis of the lower part (conical shape) of the container body 312a. The top and bottom surfaces of the container body 312a are open. The biomass is supplied into the container body 312a through an upper opening formed on the top surface of the container body 312a.

[0024] The lid 312b is provided so as to be able to open and close an upper opening formed on the top surface of the container body 312a, and the on-off valve 312c is provided so as to be able to open and close a lower opening formed on the bottom surface of the container body 312a.

[0025] The upper opening of the container body 312a is closed by the lid 312b, and the lower opening of the container body 312a is closed by the on-off valve 312c, thereby sealing the inside of the sealed container 312.

[0026] The agitator 314 agitates the contents of the sealed container 312. In this embodiment, the agitator 314 includes a rotating shaft 314a, an agitator blade 314b, and a motor 314c. The rotating shaft 314a penetrates the lid 312b. The agitator blade 314b is provided on one end of the rotating shaft 314a. The agitator blade 314b is provided so as to be located inside the sealed container 312 when the lid 312b is closed. The motor 314c rotates the agitator blade 314b via the rotating shaft 314a. The motor 314c is provided so as to be located outside the sealed container 312 when the lid 312b is closed. The agitator 314 can efficiently distribute heat supplied by the heating unit 320 (described later) throughout the biomass in the sealed container 312.

[0027] The heating unit 320 heats the reactor 310 (sealed container 312). In this embodiment, the heating unit 320 heats the outer wall of the container body 312a. The heating unit 320 is configured, for example, by a trace heater. The heating unit 320 includes an enclosing unit 322, a first exhaust pipe 324, a second exhaust pipe 326, and an aspirator 328.

[0028] The surrounding portion 322 is a pipe that spirally surrounds the outside of the sealed container 312. One end of the surrounding portion 322 is connected to a supply source of the heated gas H. The heated gas H is, for example, steam or combustion exhaust gas. In this embodiment, the supply source of the heated gas H is the boiler 190, and the heated gas H is auxiliary steam for the boiler 190. The auxiliary steam has a temperature of, for example, about 280°C.

[0029] A first discharge pipe 324 is connected to the other end of the surrounding portion 322. In this embodiment, the boiler 190 is connected to the upper end of the surrounding portion 322. The first discharge pipe 324 is connected to the lower end of the surrounding portion 322.

[0030] The first exhaust pipe 324 connects the surrounding portion 322 and the dryer 140. The second exhaust pipe 326 connects the dryer 140 and the suction side of the aspirator 328. The aspirator 328 aspirates the heated gas H. The aspirator 328 is, for example, a fan, a compressor, or a pump.

[0031] Therefore, the heated gas H passes through the surrounding portion 322, the first discharge pipe 324, and the dryer 140, and is then sucked into the aspirator 328 through the second discharge pipe 326. The heated gas H sucked by the aspirator 328 is returned to the boiler 190.

[0032] When the heating unit 320 heats the sealed container 312, the water contained in the biomass inside the sealed container 312 turns into steam. As a result, the pressure inside the sealed container 312 becomes a predetermined range above atmospheric pressure (for example, 1.5 MPa to 2.8 MPa). The temperature inside the sealed container 312 becomes 200°C to 220°C. For example, the temperature inside the sealed container 312 becomes 220°C and 2.3 MPa.

[0033] The communication pipe 330 is a pipe that connects the on-off valve 312c and the solid-gas separator 340.

[0034] The solid-gas separator 340 separates the solid-gas mixture containing biomass discharged from the reactor 310. The solid-gas separator 340 is, for example, a cyclone. In this embodiment, the solid-gas separator 340 includes a main body 342 and an exhaust pipe 344.

[0035] The main body 342 is a cylindrical container. The top and bottom surfaces of the main body 342 are sealed. In this embodiment, the main body 342 has a cylindrical shape. A receiving port 342a is formed in the upper part of the side wall of the main body 342. The communicating pipe 330 is connected to the receiving port 342a provided in the main body 342. In addition, a solid discharge port 342b is formed in the bottom surface of the main body 342. The main body 342 is at a lower pressure (approximately atmospheric pressure) than the sealed container 312 in a pressurized state. In addition, the main body 342 is at a lower temperature (for example, room temperature (25°C)) than the sealed container 312 in a pressurized state.

[0036] The exhaust pipe 344 is a pipe that penetrates the upper surface of the main body 342. An upper end 344a of the exhaust pipe 344 is connected to the cooler 210, which will be described later. A lower end of the exhaust pipe 344 is located below the inlet 342a.

[0037] The screw conveyor 346 is provided in the lower part of the main body 342. The screw conveyor 346 transports the biomass that has fallen in the solid-gas separator 340 to the solid discharge port 342b and collects it.

[0038] When steam exploding biomass, first, the lower opening of the container body 312a is closed by the on-off valve 312c. Next, biomass is supplied into the sealed container 312 (container body 312a) by the supply device 110, and then the upper opening of the container body 312a is closed by the lid 312b. Then, the sealed container 312 is heated by the heating unit 320, so that the water contained in the biomass in the sealed container 312 turns into steam, and the inside of the sealed container 312 becomes pressurized.

[0039] After that, the lower opening of the container body 312a is opened by the on-off valve 312c. Then, the biomass in the sealed container 312 is led to the solid-gas separator 340 and depressurized, and the water vapor contained in the biomass explodes due to adiabatic expansion. This causes the biomass to explode. In this way, a solid-gas mixture containing exploded (pulverized) biomass and exhaust gases such as water vapor is produced.

[0040] FIG. 3 is a diagram showing the weight balance of the solid-gas mixture after explosion. In FIG. 3, the vertical axis indicates the weight ratio [wt%]. In FIG. 3, white indicates the weight ratio of solids contained in the solid-gas mixture. In FIG. 3, hatching indicates the weight ratio of liquids contained in the solid-gas mixture. In FIG. 3, black indicates the weight ratio of gases contained in the solid-gas mixture. The weight ratios are based on the biomass (dry raw material) supplied to the crushing device 120 (100 wt%).

[0041] As shown in Figure 3, the solid-gas mixture after explosion contains approximately 72.6 wt% solids (biomass). The solid-gas mixture after explosion also contains approximately 18.4 wt% liquids (e.g., water, furfural). The solid-gas mixture after explosion also contains approximately 9 wt% gases (e.g., water vapor, carbon monoxide (CO), carbon dioxide (CO2)).

[0042] Returning to FIG. 2 , the solid-gas mixture is separated into solid and gas in the solid-gas separator 340. The biomass (solid, for example, approximately 72.6 wt%) separated in the solid-gas separator 340 is deposited in the lower part of the main body 342. The deposited biomass is guided by the screw conveyor 346 through the solid discharge port 342b to the first conveying device 130. Meanwhile, the exhaust gas separated in the solid-gas separator 340 contains the above-mentioned gas (for example, approximately 9 wt%) and atomized liquid (for example, approximately 18.4 wt%). The exhaust gas separated in the solid-gas separator 340 is then exhausted to the cooler 210 through the exhaust pipe 344.

[0043] 1, the first conveying device 130 conveys the biomass pulverized by the pulverizing device 120 to the dryer 140. The first conveying device 130 is configured by, for example, a conveyor.

[0044] The dryer 140 dries the pulverized biomass. In this embodiment, the dryer 140 is a heat exchanger that exchanges heat between the biomass and the heating gas H. As described above, the heating gas H is introduced into the dryer 140 after passing through the surrounding portion 322 that constitutes the heating section 320.

[0045] The classifier 150 classifies the dried biomass. For example, the classifier 150 classifies the biomass into biomass with a particle size of 2 mm or more and biomass with a particle size of less than 2 mm. The biomass with a particle size of 2 mm or more is returned to the receiving conveyor 112. The biomass with a particle size of less than 2 mm is transported by the second transport device 160 to the hopper 170 after drying.

[0046] The second conveying device 160 is configured, for example, by a conveyor. The post-drying hopper 170 temporarily stores dried biomass with a particle size of less than 2 mm. The biomass stored in the post-drying hopper 170 is transported to the conveying path 180 via a weighing feeder 172 and a slat valve 174.

[0047] The conveying path 180 conveys the biomass supplied from the slat valve 174 to the boiler 190 by airflow. The conveying path 180 connects a supply source of dry air and the burner of the boiler 190.

[0048] The boiler 190 (combustor) burns the biomass air-transported by the transport path 180 to generate steam.

[0049] The power generation device 200 generates power using the steam generated by the boiler 190. The power generation device 200 includes, for example, a steam turbine and a generator.

[0050] The cooler 210 cools the exhaust gas discharged from the solid-gas separator 340 through the exhaust pipe 344. The cooler 210 is, for example, a heat exchanger that exchanges heat between the exhaust gas and a refrigerant. The refrigerant is, for example, industrial water.

[0051] The cooler 210 cools the exhaust gas to a temperature at which the water vapor and furfural contained in the exhaust gas condense. The cooler 210 cools the exhaust gas, for example, so that the concentration of water vapor contained in the cooled exhaust gas becomes substantially equal to the concentration of water vapor contained in the dry air flowing through the transport path 180. The cooler 210 cools the exhaust gas to, for example, 1°C or higher and 10°C or lower.

[0052] The condensed liquid condensed by the cooler 210 is supplied to the distillation device 220. In addition, the exhaust gas EX from which the condensed liquid has been removed by the cooler 210 is supplied to the exhaust gas supply unit 230.

[0053] The distillation unit 220 distills the condensate to recover furfural. If the boiler 190 and the power generation unit 200 are 500 MW-class 25 cal% biomass co-firing boilers, for example, 2,800 tons of furfural can be recovered per year.

[0054] The exhaust gas supply unit 230 supplies the exhaust gas EX cooled by the cooler to the boiler 190. In this embodiment, the exhaust gas supply unit 230 includes a buffer tank 232, a communication passage 234, and a valve 236.

[0055] The buffer tank 232 is a tank that stores the exhaust gas EX. The communication path 234 is a flow path that connects the buffer tank 232 with the transfer path 180. The valve 236 is provided on the transfer path 180. The valve 236 opens and closes the transfer path 180.

[0056] FIG. 4 is a diagram showing the composition of exhaust gas EX. In FIG. 4, the vertical axis represents the weight ratio [wt%]. In FIG. 4, the white color represents the weight ratio of carbon monoxide (CO) contained in exhaust gas EX. In FIG. 4, the hatched area represents the weight ratio of carbon dioxide (CO2) contained in exhaust gas EX. In FIG. 4, the black color represents the weight ratio of gases other than carbon monoxide and carbon dioxide contained in exhaust gas EX.

[0057] As shown in Figure 4, exhaust gas EX contains approximately 3 wt% (30,000 ppm) of carbon monoxide. It also contains approximately 31.3 wt% of carbon dioxide. It also contains approximately 65.7 wt% of other gases.

[0058] Carbon monoxide contained in exhaust gas EX is toxic, so it needs to be treated to make it harmless. On the other hand, carbon monoxide is flammable, so it can be used as fuel.

[0059] Therefore, by supplying the exhaust gas EX to the boiler 190 via the transfer path 180, the carbon monoxide can be burned in the boiler 190. This makes it possible to reduce the cost required for treating carbon monoxide (exhaust gas EX). In addition, because the carbon monoxide can be used as fuel, the amount of biomass (fuel) required to ensure the same output in the boiler 190 can be reduced.

[0060] The control unit 240 is configured with a semiconductor integrated circuit including a CPU (Central Processing Unit). The control unit 240 reads programs, parameters, etc. for operating the CPU from the ROM. The control unit 240 manages and controls the entire combustion system 100 in cooperation with RAM as a work area and other electronic circuits.

[0061] In this embodiment, the control unit 240 controls the opening degree of the valve 236 based on the power generation efficiency of the power generation device 200. Specifically, the control unit 240 opens the valve 236 when the power generation efficiency of the power generation device 200 is lower than a predetermined value. On the other hand, the control unit 240 closes the valve 236 when the power generation efficiency of the power generation device 200 is higher than the predetermined value.

[0062] This makes it possible to maintain the power generation efficiency of the power generation device 200 at a predetermined value.

[0063] As described above, the combustion system 100 according to this embodiment includes the boiler 190, the cooler 210, and the exhaust gas supply unit 230. This allows the combustion system 100 to combust the carbon monoxide contained in the exhaust gas EX generated by explosion. Therefore, the combustion system 100 can reduce the cost required to treat the exhaust gas EX.

[0064] Combustion system 100 also includes a condenser 210 and a distillation unit 220. This allows combustion system 100 to recover furfural from condensate that would otherwise be discarded.

[0065] The combustion system 100 also includes a transfer path 180, a buffer tank 232, a communication path 234, and a valve 236. This enables the combustion system 100 to supply the exhaust gas EX to the boiler 190 in a stable manner.

[0066] As described above, the heating section 320 of the pulverizer 120 heats the outer wall of the reactor 310. This allows the pulverizer 120 to steam the biomass in the reactor 310 without supplying steam into the reactor 310. Therefore, the pulverizer 120 can increase the concentration of furfural contained in the liquid that constitutes the solid-gas mixture after explosion. This allows the processing load of the power generation device 200 to be reduced.

[0067] Although the embodiments have been described above with reference to the accompanying drawings, it goes without saying that the present disclosure is not limited to the above-described embodiments. It is clear that a person skilled in the art can conceive of various modifications or alterations within the scope of the claims, and it is understood that these also naturally fall within the technical scope of the present disclosure.

[0068] For example, in the above-described embodiment, the combustion system 100 is provided with the boiler 190 as the combustor. However, the configuration of the combustor is not limited as long as it can combust the biomass and exhaust gas EX separated by the solid-gas separator 340. The combustor may be, for example, a blast furnace, a water heater, or the like.

[0069] In the above embodiment, the case where the communication passage 234 is connected to the transport passage 180 has been exemplified. However, the communication passage 234 does not have to be connected to the transport passage 180. For example, the communication passage 234 may be directly connected to the burner of the boiler 190.

[0070] Furthermore, in the above embodiment, an example was given in which the combustion system 100 includes the transfer path 180, the buffer tank 232, the communication path 234, and the valve 236. However, the transfer path 180, the buffer tank 232, the communication path 234, and the valve 236 are not essential components. The combustion system 100 only needs to include at least the exhaust gas supply unit 230 that supplies the exhaust gas EX cooled by the cooler 210 to the combustor. For example, the exhaust gas supply unit 230 may include a flow path that connects the cooler 210 and the boiler 190.

[0071] Furthermore, in the above embodiment, an example has been given in which the buffer tank 232 stores the exhaust gas EX after it has been cooled by the cooler 210. However, the buffer tank 232 may store the exhaust gas separated by the solid-gas separator 340. For example, the buffer tank 232 may store the exhaust gas EX before it is cooled by the cooler 210. Furthermore, the boiler 190 may function as the buffer tank.

[0072] In the above embodiment, the control unit 240 controls the opening and closing of the valve 236. However, the control unit 240 may control the opening degree of the valve 236. For example, the control unit 240 may control the opening degree of the valve 236 so that the power generation efficiency of the power generation device 200 becomes a predetermined value. In this way, the control unit 240 can stably maintain the power generation efficiency of the power generation device 200 at a predetermined value.

[0073] In the above embodiment, the combustion system 100 includes the power generation device 200 and the control unit 240. However, the power generation device 200 and the control unit 240 are not essential components.

[0074] In the above embodiment, an example has been given in which auxiliary steam from the boiler 190 is supplied to the surrounding portion 322 that constitutes the heating portion 320. This allows the heating portion 320 to heat the reactor 310 without reducing the power generation efficiency of the power generation device 200. However, there is no limitation on the steam supplied to the surrounding portion 322. For example, instead of or in addition to the auxiliary steam, one or both of the main steam (e.g., about 450°C) and extraction steam (e.g., about 350°C) from the boiler 190 may be supplied to the surrounding portion 322.

[0075] In the above embodiment, the heating unit 320 is a trace heater. However, the configuration of the heating unit 320 is not limited as long as it can heat the sealed container 312 from the outside. For example, the heating unit 320 may be an electric heater.

[0076] In the above embodiment, the agitator 314 includes the rotating shaft 314a, the agitator blade 314b, and the motor 314c. However, the agitator 314 is not limited to any particular configuration as long as it can agitate the contents inside the sealed container 312. The agitator 314 may be, for example, a mechanism that reciprocates the sealed container 312 itself.

[0077] In the above embodiment, the crushing device 120 is provided with the agitating unit 314. However, the agitating unit 314 is not an essential component.

[0078] In the above embodiment, the combustion system 100 is exemplified as including the distillation device 220. However, the distillation device 220 is not an essential component.

[0079] This disclosure can contribute, for example, to Sustainable Development Goals (SDGs) Goal 7: "Ensure access to affordable, reliable, sustainable and modern energy" and Goal 13: "Take urgent action to combat climate change and its impacts." [Explanation of symbols]

[0080] 100 Combustion System 180 Transport Path 190 Boiler (combustor) 200 Power Generation Equipment 210 Cooler 230 Exhaust gas supply unit 232 Buffer Tank 234 Communication path 236 Valve 240 Control Unit 310 Reactor 320 Heating section 340 Solid-gas separator

Claims

1. a reactor for pressurizing the biomass to above atmospheric pressure; a heating unit that heats the reactor; a solid-gas separator that separates the solid-gas mixture containing the biomass discharged from the reactor into solid and gas; a combustor that combusts the biomass separated by the solid-gas separator; a cooler that cools the exhaust gas separated by the solid-gas separator; an exhaust gas supply unit that supplies the exhaust gas cooled by the cooler to the combustor; A combustion system comprising:

2. a transport path for airflow transporting the biomass separated by the solid-gas separator to the combustor; The exhaust gas supply unit a buffer tank for storing the exhaust gas; a communication passage that communicates the buffer tank with the conveying path; a valve provided in the communication passage; The combustion system of claim 1 , comprising:

3. the combustor is a boiler, a power generation device that generates electricity using the steam generated by the boiler; a control unit that controls the opening degree of the valve based on the power generation efficiency of the power generation device; The combustion system of claim 2 , comprising:

4. The combustion system according to claim 1 , wherein the heating section heats an outer wall of the reactor.

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