Biomass power generation system

Abstract

To provide a biomass gas power generation system capable of reducing tar content.SOLUTION: A biomass power generation system 100 comprises a first power generating unit 10, a second power generating unit 20, and a heater 30 connecting the first power generating unit 10 and the second power generating unit 20. The heater 30 combusts a fuel gas F2 supplied from a second reformer 23 to supply combustion heat to a first thermal decomposition furnace 12.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a power generation system that uses biomass as fuel. [Background technology]

[0002] Biomass is a renewable organic resource and will increasingly be used for power generation as a carbon-neutral energy source. Regarding woody biomass, power generation using unused materials such as thinned wood, sawmill chips, and building demolition materials is beginning to be commercialized. Its potential as a locally produced and consumed energy source is growing. Requests for deployment are also emerging in areas where access to raw materials from forests is limited. Future applications will require expansion to accommodate a variety of raw materials, including herbaceous biomass such as rice and wheat straw, as well as food waste and combustible waste such as plastic packaging. Biomass power generation systems include direct combustion steam power generation, in which biomass is directly burned in a boiler to drive a steam turbine, and pyrolysis gasification power generation, in which biomass is pyrolyzed and gasified, and the resulting gas is then used as reformed fuel to power an engine. Steam turbine power generation methods, however, have low net generating efficiency as the scale of power generation decreases, making their practical application difficult. Gasification methods can achieve high power generation efficiency even on small-scale power generation.

[0003] In gasification power generation, biomass is fed into a pyrolysis furnace and carbonized, producing volatile components and char after the water evaporates. The volatile components include tar, which is made up of aromatic compounds, in addition to light biomass gas, which is primarily composed of hydrogen, carbon monoxide, and methane. The gas and char produced by pyrolysis are fed into a reformer in the next step and heated together with steam and a catalyst such as an alkali metal, which causes the tar and char to gasify, producing fuel gas that can be used as engine fuel. The inventor has previously explained this highly efficient production of fuel gas in Patent Document 1.

[0004] If heating is insufficient locally within the pyrolysis furnace, the resulting gas will contain a high tar fraction, and if the downstream reformer cannot maintain a high temperature, the tar will not be fully decomposed. If the tar remaining in the fuel gas at the reformer outlet liquefies or solidifies during the subsequent cooling process, it can clog gas purification filters, block pipes, cause engine spark plug misfires, or adhere to engine intake and exhaust valves, resulting in serious malfunctions. These tar-related malfunctions begin as minute deposits and grow over time, increasing the likelihood of shutdowns and significantly affecting the availability of power plants and power generation systems. Previously, gasification methods using partial combustion, external oxygen injection, and indirect heating (steaming) using an external heat source have been developed.

[0005] Patent Document 1 proposes a configuration in which the pyrolysis furnace and reformer furnace are directly connected using indirect heating (steaming method), minimizing heat radiation to the outside, and recovering and reusing the sensible heat of the fuel gas and the exhaust heat of the engine, thereby increasing thermal efficiency and preventing insufficient heating, thereby reducing tar problems. Patent Document 2 proposes a power generation system that distributes fuel gas supplied from a reformer to multiple engines so that power generation does not stop when a broken engine is serviced. This configuration allows the other engines to continue operating even if one engine is stopped to clean up tar, minimizing the decline in the power plant's operating rate. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2017-128623 A [Patent Document 2] JP 2017-8800 A Summary of the Invention [Problem to be solved by the invention]

[0007] However, not only is the work of cleaning off tar and maintaining engines, etc. a heavy burden, but the decline in annual power generation due to a lower operating rate also leads to a decline in economic efficiency. Therefore, the objective of this study is to provide a biomass power generation system that can reduce tar troubles. [Means for solving the problem]

[0008] A biomass power generation system according to one aspect of the present invention includes a first power generation facility, a second power generation facility, and a heater connecting the first and second power generation facilities. The first power generation facility includes a first pyrolysis furnace that pyrolyzes an input first biomass, a first reformer that reforms the biomass gas and carbide particles produced in the first pyrolysis furnace into a first fuel gas, and a first engine that receives the first fuel gas and drives a first generator. The second power generation facility includes a second pyrolysis furnace that pyrolyzes an input second biomass, a second reformer that reforms the biomass gas and carbide particles produced in the second pyrolysis furnace into a second fuel gas, and a second engine that receives the second fuel gas and drives a second generator. The heater combusts the second fuel gas to supply combustion heat to the first pyrolysis furnace.

[0009] According to this aspect, the gasified fuel gas from each of the multiple gasification power generation devices that make up the power generation system is supplied to multiple engines, and the engine exhaust gas is supplied to a heater to supply heat at an appropriate temperature to the pyrolysis furnace, thereby maintaining a stable reaction temperature, reducing tar troubles, and increasing the operating rate. Furthermore, the amount of auxiliary fuel supplied from outside during startup and start-up is reduced. Combustion heat can be supplied from the heater to sufficiently heat the first pyrolysis furnace. The first pyrolysis furnace can be heated to a temperature range where the tar fraction can be reduced.

[0010] In the above embodiment, the second exhaust gas may have a higher temperature than the first exhaust gas. The first pyrolysis furnace may be heated by high-temperature gas obtained by heating the second exhaust gas with a heater.

[0011] According to this embodiment, the second exhaust gas having a relatively high temperature is used as the heat medium, so that the fuel gas consumed for heating the heat medium can be saved.

[0012] In the above aspect, the first engine may be a reciprocating engine and the second engine may be a rotary engine.

[0013] The second power generation facility uses a general-purpose rotary engine, which has no intake or exhaust valves and is therefore less susceptible to breakdowns even if tar remains in the fuel gas. The use of a rotary engine minimizes noise and vibration, and its lightweight design makes maintenance easy and inexpensive. The use of this engine also broadens the range of biomass options available and allows for emergency response to wood waste during disasters, greatly reducing operating costs as a regional infrastructure. The high temperature of the rotary engine's exhaust gas allows for efficient heating of the first pyrolysis furnace. Combustion heat supplied from the heater sufficiently raises the temperature of the first pyrolysis furnace, enabling the production of products with a low tar content. Because the second reformer can fully decompose and remove the tar from the fuel gas, the second power generation facility can maintain stable, highly efficient power generation using a reciprocating engine.

[0014] In the above embodiment, the first pyrolysis furnace may dry distill the input biomass at 600 to 850°C.

[0015] According to this embodiment, a product with a small amount of tar fraction can be obtained.

[0016] In the above embodiment, the heater may supply combustion heat to the second pyrolysis furnace in addition to the first pyrolysis furnace.

[0017] According to this embodiment, it is possible to supply a sufficient amount of heat to the first pyrolysis furnace while also supplying a sufficient amount of heat to the second pyrolysis furnace.

[0018] In the above aspect, the first pyrolysis furnace may further include a drying furnace that reduces the moisture content of the biomass fed into the first pyrolysis furnace, and the drying furnace may use, as a heat source, high-temperature gas whose temperature has been reduced by heating the first pyrolysis furnace.

[0019] According to this embodiment, the moisture content of the biomass fed into the first pyrolysis furnace can be reduced by utilizing the exhaust heat from the first pyrolysis furnace. As the moisture evaporates, the temperature of the first pyrolysis furnace can be easily increased, and a product with a low tar fraction can be obtained.

[0020] One embodiment of the biomass power generation system comprises a second pyrolysis furnace that pyrolyzes input biomass, a second reformer furnace that reforms the biomass gas and carbonized material particles produced in the second pyrolysis furnace into fuel gas, a second engine that is a rotary engine that receives fuel gas from the second reformer furnace and drives a second generator, and a heater that combusts the fuel gas supplied from the second reformer furnace and supplies combustion heat to the second pyrolysis furnace.

[0021] According to this aspect, since it is configured as a single power generation facility, it can meet the needs of local production and consumption. It is equipped with a rotary engine that is resistant to breakdowns even if tar remains in the fuel gas, and a heater that can burn the fuel gas and raise the temperature to a range where the tar fraction is small, so it is possible to accept a variety of biomass materials, from wood to miscellaneous materials, as raw materials. Recently, the large amount of waste generated during disasters such as earthquakes and typhoons and the rapid disposal of such waste have become major issues, but the facility will be able to accept a wide range of waste, including materials from demolished houses, furniture, containers and packaging, and household waste. [Effects of the Invention]

[0022] According to the present invention, it is possible to provide a biomass gas power generation system capable of reducing tar fraction. [Brief explanation of the drawings]

[0023] [Figure 1] FIG. 1 is a diagram schematically illustrating an example of a power generation system according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a diagram schematically illustrating an example of a power generation system according to a second embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0024] A preferred embodiment of the present invention will be described with reference to the accompanying drawings. In each drawing, components with the same reference numerals have the same or similar configurations. A biomass power generation system 100 according to one embodiment of the present invention is characterized in that it includes two power generation systems, a first power generation system 10 and a second power generation system 20, and further includes a heater 30 that combusts fuel gas F2 generated in the second power generation system 20 to supply combustion heat to a first pyrolysis furnace 12 that constitutes the first power generation system 10.

[0025] The heater 30 is, for example, a burner that blows out fuel gas F2 from a burner nozzle and burns it, generating high-temperature gas H, which is sent to the outer casing of the first pyrolysis furnace 12, and supplies the combustion heat of the fuel gas F2 to the first pyrolysis furnace. The high-temperature gas H may be generated by heating air with the heater 30. The high-temperature gas H may be generated by supplying combustion heat to high-temperature exhaust gas E2 discharged from the second power generation facility 20. The high-temperature gas H may be generated by supplying combustion heat to mixed gases E1, E2 of exhaust gas E1 from the first power generation facility 10 and exhaust gas E2 from the second power generation facility 20. Each component will be described in detail below with reference to the drawings.

[0026] 1 is a diagram schematically illustrating an example of a biomass power generation system 100 according to a first embodiment of the present invention. As described above, the biomass power generation system 100 includes a first power generation facility 10, a second power generation facility 20, and a heater 30.

[0027] 1, the first power generation facility 10 includes a first pyrolysis furnace 12, a first reformer 13, a first engine 14, and a first generator 15. Similarly, the second power generation facility 20 includes a second pyrolysis furnace 22, a second reformer 23, a second engine 24, and a second generator 25.

[0028] The pyrolysis furnaces 12, 22 pyrolyze the input biomass B1, B2 by carbonization to produce biomass gas and char. In the illustrated example, the pyrolysis furnaces 12, 22 are horizontal furnaces configured as an extrusion system equipped with at least one of a slightly inclined rotating cylindrical lifter drum, a screw conveyor, and a screw kiln. The pyrolysis furnaces 12, 22 then flow the generated biomass gas and granular char down to the reformer furnaces 13, 23. The pyrolysis furnaces 12, 22 can reduce the tar fraction in the product. In this invention, the heater 30 can supply heat transfer gas at a maximum temperature of 950°C to the pyrolysis furnace outer casing, allowing the generated biogas to be heated to 850°C at the pyrolysis furnace outlet. For example, with wood chips, the temperature is set and maintained at approximately 600°C at the pyrolysis furnace outlet. A heat source capable of responding to increases in tar content due to fluctuations in the feedstock composition is available.

[0029] The reformer furnaces 13 and 23 reform the biomass gas and char generated in the pyrolysis furnaces 12 and 22 into fuel gases F1 and F2. In the illustrated example, the reformer furnaces 13 and 23 are configured as vertical furnaces connected to the pyrolysis furnaces 12 and 22. Inside the reformer furnaces 13 and 23, the biomass gas is heated in the upper space by partial combustion using air injection. This partial combustion allows the biomass gas to exceed 1000°C in a short period of time. In the char packed bed at the bottom of the furnace, the biogas is adsorbed onto the surface of the char particles (char) and decomposed using the activity of the surface pore structure. Further, the char and tar are gasified by a steam reforming reaction. Because steam reforming is an endothermic reaction, the temperature gradually decreases toward the bottom of the packed bed. In the present invention, the temperature is controlled to maintain approximately 850°C at the outlet of the packed bed.

[0030] The engines 14, 24 are supplied with fuel gases F1, F2 to drive generators 15, 25. In the illustrated example, the first engine 14 is a reciprocating engine, and the second engine 24 is a rotary engine. The first and second engines 14, 24 are not limited to the illustrated example, and may be other types of engines.

[0031] The exhaust gas E1 from the first engine 14, which is a reciprocating engine, is, for example, about 440°C in the case of a gas engine for private generation of 500 kW or more. The exhaust gas E2 from the second engine 24, which is a rotary engine, is, for example, about 750°C. In other words, the exhaust gas E2 from the second engine 24 is hotter than the exhaust gas E1 from the first engine 14. The rotors of the generators 15, 25 are connected to the output shafts of the engines 14, 24.

[0032] The heater 30 combusts the fuel gas F2 supplied from the second reformer 23 to generate high-temperature gas H, and supplies the combustion heat of the fuel gas F2 to the first pyrolysis furnace 12 by blowing a part or all of the high-temperature gas H into the first pyrolysis furnace 12. In the present invention, the maximum temperature of the high-temperature gas H is set to about 950°C, taking into consideration everything from the selection of heat-resistant materials to costs.

[0033] In the illustrated example, the heater 30 supplies high-temperature gas H to the second pyrolysis furnace 22 in addition to the first pyrolysis furnace 12. The combustion heat produced by the heater 30 burning the fuel gas F2 is supplied to the second pyrolysis furnace 22 using the high-temperature gas H as a medium. Of the high-temperature gas H heated by the heater 30, the portion supplied from the heater 30 to the first pyrolysis furnace 12 is referred to as high-temperature gas H1, and the portion supplied from the heater 30 to the second pyrolysis furnace 22 is referred to as high-temperature gas H2. The ratio of high-temperature gas H1 to high-temperature gas H2 is more than five times that of high-temperature gas H2. In the illustrated example, H1:H2 = 6:1.

[0034] In the illustrated example, a mixed gas E1, E2 of the exhaust gas E1 from the first power generation facility 10 and the exhaust gas E2 from the second power generation facility 20 is heated by the heater 30 to generate high-temperature gas H. As described above, the high-temperature gas H may be generated by heating the exhaust gas E2 from the second engine 24 by the heater 30, or air may be heated by the heater 30 to generate high-temperature gas H.

[0035] The first biomass B1 fed into the first pyrolysis furnace 12 is, for example, woody biomass and contains about 50% moisture. The first power generation facility 10 may further include a drying furnace 11. The drying furnace 11 reduces the moisture content of the biomass B1 fed into the first pyrolysis furnace 12 to create an environment in the first pyrolysis furnace 12 that facilitates heating. In the illustrated example, the drying furnace 11 uses high-temperature gas H1', ​​which has been cooled by heating the first pyrolysis furnace 12, as a heat source. The high-temperature gas H1' has a temperature of, for example, about 300 to 400°C.

[0036] The second engine 24, which is a rotary engine, is unlikely to break down even if tar remains in the fuel gas F2, and therefore various types of biomass B2 can be used as the raw material for the fuel gas F2. The second biomass B2 fed into the second pyrolysis furnace 22 is, for example, construction waste and contains about 20% moisture.

[0037] The biomass power generation system 100 of the first embodiment configured as described above can supply combustion heat from the heater 30 to sufficiently heat the first pyrolysis furnace 12. The first pyrolysis furnace 12 can be heated to a temperature range of, for example, 600 to 850°C, which allows the production of products with a low tar content. Because the tar in the fuel gas F1 can be sufficiently removed, power can be generated in the first power generation facility 10, which has a high rated output, using a reciprocating engine that is sensitive to tar but has excellent power generation efficiency. Furthermore, from startup to steady-state operation, auxiliary fuel (LPG) must be burned to heat the furnace and flow paths. By operating the second system first during startup, significant LPG savings can be achieved. Starting from the thermal cracking furnace of the second system (RE) system, heating is done downstream with LPG to start up the second system, and when steady-state output is reached, for example, half of the fuel gas produced from the reformer is combusted in a heater and reheated with the high-temperature engine exhaust gas of the second system. This high-temperature gas, at 950°C, is used to start up and heat the cracking furnace and other furnaces of the first system, thereby making it possible to significantly reduce the amount of LPG used in the second system.

[0038] Next, a biomass power generation system 200 according to a second embodiment of the present invention will be described. Components having the same or similar functions as those of the first embodiment will be assigned the same reference numerals, and the corresponding descriptions of the first embodiment will be referred to, and descriptions thereof will be omitted here. Figure 2 is a diagram schematically showing an example of a power generation system 200 according to the second embodiment of the present invention.

[0039] The second embodiment differs from the first embodiment in that the first power generation facility 10 is omitted. As shown in Fig. 2, the biomass power generation system 200 includes a second power generation facility 20 and a heater 30. As described in the first embodiment, the second power generation facility 20 includes a second pyrolysis furnace 22, a second reformer 23, a second engine 24, and a second generator 25.

[0040] The biomass power generation system 200 of the second embodiment eliminates the power generation facility 10, thereby satisfying the demand for local production and consumption in mountain villages where an inexpensive power generation system is required. It is equipped with a rotary engine 24 that is resistant to breakdowns even if tar remains in the fuel gas F2, and a heater 30 that burns the fuel gas F2 supplied from the reformer 23 to heat the pyrolysis furnace 22, allowing the use of miscellaneous biomass B2 as a raw material. It can obtain fuel gas F2 from disaster waste, such as dismantled furniture and household waste including plastic packaging materials, which is generated during disasters. It is also useful in responding to power outages.

[0041] The above-described embodiments are intended to facilitate understanding of the present invention and are not intended to limit the present invention. The elements of the embodiments, as well as their arrangement, materials, conditions, shapes, sizes, etc., are not limited to those illustrated and can be modified as appropriate. Furthermore, configurations shown in different embodiments can be partially substituted or combined with each other.

Claims

1. a first power generation facility, a second power generation facility, and a heater connecting the first power generation facility and the second power generation facility; The first power generation facility includes a first pyrolysis furnace that pyrolyzes an input first biomass, a first reformer that reforms the biomass gas and char generated in the first pyrolysis furnace into a first fuel gas, and a first engine that receives the first fuel gas and drives a first generator, The second power generation facility includes a second pyrolysis furnace that pyrolyzes an input second biomass, a second reformer that reforms the biomass gas and char generated in the second pyrolysis furnace into a second fuel gas, and a second engine that receives the second fuel gas and drives a second generator, The heater combusts the second fuel gas supplied from the second reformer to supply combustion heat to the first pyrolysis furnace.

2. a second exhaust gas discharged from the second engine has a higher temperature than a second exhaust gas discharged from the first engine; The first pyrolysis furnace is heated by high-temperature gas obtained by heating the second exhaust gas in the heater. The biomass power generation system according to claim 1 .

3. The first engine is a reciprocating engine and the second engine is a rotary engine. The biomass power generation system according to claim 1 or 2.

4. The first pyrolysis furnace dry distills the input first biomass at 600 to 850 ° C. The biomass power generation system according to any one of claims 1 to 3.

5. The heater supplies combustion heat to the second pyrolysis furnace in addition to the first pyrolysis furnace, and the amount of heat from the heater to the first pyrolysis furnace is five times or more of the amount of heat from the heater to the second pyrolysis furnace. The biomass power generation system according to any one of claims 1 to 4.

6. The method further includes a drying furnace that reduces the moisture content of the first biomass, and the drying furnace uses the high-temperature gas, the temperature of which has been reduced by heating the first pyrolysis furnace, as a heat source. The biomass power generation system according to claim 2 .

7. a second pyrolysis furnace that pyrolyzes an input second biomass; a second reforming furnace that reforms the biomass gas and char particles generated in the second pyrolysis furnace into a second fuel gas; a second engine that is a rotary engine that receives the second fuel gas and drives a second generator; and a heater that combusts the second fuel gas and supplies combustion heat to the second pyrolysis furnace. Biomass power generation system.

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