Biomass gasification device, biomass gasification plant, and method for producing biomass gas

Abstract

To provide a biomass gasification device, biomass gasification plant, and biomass gas production method, that are intended to improve energy efficiency.SOLUTION: A biomass gasification device 10 comprises: a biomass gasification furnace 11 that generates a biomass gas from a biomass fuel and a gasification agent; a filter 13 that separates char from the biomass gas discharged from the biomass gasification furnace 11; and a char cooler 16 that exchanges heat between the char that is separated by the filter 13 and at least part of the gasification agent supplied to the biomass gasification furnace 11 to heat the gasification agent.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a biomass gasifier, a biomass gasification plant, and a method for producing biomass gas. [Background technology]

[0002] A gasification apparatus equipped with a gasification furnace that supplies a carbon-containing solid fuel such as biomass fuel into the furnace and partially combusts and gasifies the carbon-containing solid fuel to produce combustible gas is known (for example, Patent Document 1).

[0003] Patent Document 1 describes a gasification system that includes a dryer that dries biomass, a biomass gasification furnace that gasifies the biomass dried in the dryer, a high-temperature heat exchanger and a low-temperature heat exchanger that exchange heat between the product gas produced in the biomass gasification furnace and steam, which is a gasifying agent, a dust removal device that is interposed between the high-temperature heat exchanger and the low-temperature heat exchanger and that removes soot and dust from the product gas, and a gas purification device that removes impurities from the product gas after the low-temperature heat exchange. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 4658980 Summary of the Invention [Problem to be solved by the invention]

[0005] In gasification systems that gasify biomass fuel, char, primarily composed of unburned carbon and ash in the biomass fuel, is generated during the gasification reaction in the gasifier. Therefore, the product gas generated in the gasifier contains char. Because char adversely affects various equipment installed downstream of the gasifier, it must be removed from the product gas. For this reason, a removal device is installed downstream of the gasifier to remove char from the product gas. The char removed by the removal device is extremely hot. Therefore, if the removed char is directly discharged into the atmosphere, it may react with oxygen in the air, generating heat or catching fire. To prevent this, the char is sent to a char cooler to cool the char before being discharged into the atmosphere.

[0006] In a char cooler, for example, char is cooled by heat exchange between the char and cooling water. The cooling water is heated by heat exchange with the char, but conventionally, this heated cooling water was discharged outside the gasifier. As a result, the waste heat of the char was not effectively utilized in the gasifier, and did not contribute to the energy efficiency of the gasifier. In recent years, gasifiers have become larger, and the waste heat generated when cooling the char has also increased.

[0007] The present disclosure has been made in consideration of the above circumstances, and aims to provide a biomass gasification apparatus, a biomass gasification plant, and a method for producing biomass gas that can improve energy efficiency. [Means for solving the problem]

[0008] In order to solve the above problems, the biomass gasification apparatus, biomass gasification plant, and biomass gas production method of the present disclosure employ the following measures. A biomass gasification apparatus according to one aspect of the present disclosure includes a gasification furnace that generates biomass gas from biomass fuel and a gasifying agent, a separation unit that separates char from the biomass gas discharged from the gasification furnace, and a heat exchange unit that exchanges heat between the char separated in the separation unit and at least a portion of the gasifying agent to be supplied to the gasification furnace, thereby heating the gasifying agent.

[0009] A method for producing biomass gas according to one aspect of the present disclosure includes a generation process for generating biomass gas from biomass fuel and a gasifying agent in a gasification furnace, a separation process for separating char from the biomass gas generated in the generation process and discharged from the gasification furnace, and a heat exchange process for exchanging heat between the char separated in the separation process and at least a portion of the gasifying agent to be supplied to the gasification furnace, thereby heating the gasifying agent, and in the generation process, biomass gas is generated using the gasifying agent heated in the heat exchange process. [Effects of the Invention]

[0010] According to the present disclosure, the energy efficiency of the entire biomass gasification system can be improved. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a schematic configuration diagram of a biomass gasification apparatus according to a first embodiment of the present disclosure. [Figure 2] FIG. 10 is a schematic configuration diagram of a biomass gasification plant according to a second embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, an embodiment of a biomass gasification apparatus, a biomass gasification plant, and a method for producing biomass gas according to the present disclosure will be described with reference to the drawings.

[0013] [First embodiment] Hereinafter, a biomass gasification apparatus according to a first embodiment of the present disclosure will be described with reference to FIG. The biomass gasification system 10 according to this embodiment is a device that produces combustible biomass gas by partially combusting and gasifying biomass fuel. Biomass fuel is a renewable organic resource derived from living organisms, and examples include thinned wood, waste wood, driftwood, grass, waste, sludge, and recycled fuels (pellets and chips) made from these materials, but are not limited to those listed here. Biomass fuel is carbon-neutral, meaning it does not emit carbon dioxide, a greenhouse gas, because it captures carbon dioxide during the biomass growth process. Therefore, various uses of biomass fuel are being considered.

[0014] As shown in FIG. 1, a biomass gasification system 10 includes a biomass gasifier 11 that generates biomass gas, a high-temperature synthesis gas cooler (high-temperature SGC) 12 to which the biomass gas discharged from the biomass gasifier 11 is guided, a filter (separation unit) 13 that removes char (mainly unburned carbon and ash) contained in the biomass gas, a char hopper 15 that stores the removed char, a char cooler (heat exchange unit) 16 that cools the removed char, a low-temperature synthesis gas cooler 14 (low-temperature SGC) to which the biomass gas from which the char has been removed is guided, a feedwater preheating unit 17 that preheats the gasifying agent that is guided to the low-temperature synthesis gas cooler 14, and a scrubber 18 that removes impurities from the biomass gas.

[0015] The biomass gasifier 11 generates biomass gas by gasifying biomass fuel supplied by a biomass supply unit (supply unit) 19. The biomass supply unit 19 transports the biomass fuel to the biomass gasifier 11 and has a feeder (not shown) that feeds the biomass fuel into the biomass gasifier 11. An oxygen line L17 is connected to the biomass gasifier 11. Oxygen supplied from an oxygen supply device (not shown) flows through the oxygen line L17. The downstream end of a fourth steam line L16 is connected to the biomass gasifier 11. Steam (gasifying agent) heated by the high-temperature synthesis gas cooler 12 or the like flows through the fourth steam line L16.

[0016] The high-temperature synthesis gas cooler (biomass gas cooling section) 12 and the low-temperature synthesis gas cooler (biomass gas cooling section) 14 exchange heat between the biomass gas and feedwater or steam (gasification agent). The high-temperature synthesis gas cooler 12 and the low-temperature synthesis gas cooler 14 use the heat of the biomass gas generated in the biomass gasifier 11 to heat the steam that is introduced to the biomass gasifier 11 as a gasification agent, and also cool the biomass gas.

[0017] The filter 13 allows the biomass gas to pass through and captures the char contained in the passing biomass gas. That is, the filter 13 separates the char from the biomass gas. The char hopper 15 has a space formed therein, and stores the char in this space. The char cooler 16 cools the char with makeup water. Make-up water at room temperature is supplied to the char cooler 16 from a makeup water supply device (not shown). The feedwater preheating section 17 heats the feedwater using a heat medium. A feedwater supply device (not shown) supplies room temperature feedwater to the feedwater preheating section 17. The scrubber 18 removes impurities (e.g., tar, ammonia, etc.) contained in the biomass gas.

[0018] Next, a description will be given of the flow of biomass gas and the like in the biomass gasification apparatus 10 according to this embodiment. Note that specific values of temperatures and the like in the following description are merely examples, and are not limited to the temperatures described. Biomass fuel is supplied to the biomass gasifier 11 by the biomass supply unit 19. Oxygen is also supplied to the biomass gasifier 11 from an oxygen line L17. A gasifying agent is also supplied to the biomass gasifier 11. The flow of the gasifying agent will be described in detail later. In the biomass gasifier 11, the supplied biomass fuel reacts with oxygen to generate carbon monoxide, and then a water-gas shift reaction occurs with a gasifying agent (steam) to generate a mixed gas (biomass gas) of carbon monoxide and hydrogen in a mixture ratio that meets the specifications of the downstream equipment (generation process). The biomass gas generated in the biomass gasifier 11 is guided to the high-temperature synthesis gas cooler 12 via the first biomass gas line L1. In the high-temperature synthesis gas cooler 12, heat exchange occurs between the biomass gas and the gasifying agent, and the biomass gas is cooled.

[0019] The biomass gas discharged from the high-temperature synthesis gas cooler 12 is guided to the filter 13 via the second biomass gas line L2. The biomass gas guided to the filter 13 passes through the filter 13. At this time, char contained in the biomass gas is captured by the filter 13. That is, the char is separated from the biomass gas (separation process). The collected char is guided to the char hopper 15 via the first char line L6. The char hopper 15 temporarily stores the char. The char stored in the char hopper 15 is discharged from the outlet of the char hopper 15 at a predetermined timing and guided to the char cooler 16 via the second char line L7. At this time, the temperature of the char guided to the char cooler 16 is approximately 300°C to 400°C. In the char cooler 16, heat exchange occurs between the char and makeup water, and the char is cooled to room temperature (heat exchange process). The cooled char is discharged to the outside of the system via the third char line L8.

[0020] Meanwhile, the biomass gas that has passed through the filter 13 (i.e., biomass gas from which char has been removed) is guided to the low-temperature synthesis gas cooler 14 via the third biomass gas line L3. In the low-temperature synthesis gas cooler 14, heat exchange occurs between the biomass gas and the gasifying agent, and the biomass gas is cooled. The biomass gas discharged from the low-temperature synthesis gas cooler 14 is guided to the scrubber 18 via the fourth biomass gas line L4. Scrubber water (not shown) is supplied to the scrubber 18, and impurities contained in the biomass gas (e.g., tar components, ammonia, etc.) are removed by the scrubber water. In addition, water vapor contained in the biomass gas (excess water vapor not consumed in the water-gas shift reaction) is also condensed and recovered in the scrubber 18. The impurities and excess water vapor removed in the scrubber 18 are discharged to the outside of the system together with the scrubber water as wastewater via the drainage line L18. On the other hand, the biomass gas from which impurities and excess water vapor have been removed is discharged from the scrubber 18 and led to the downstream equipment via the fifth biomass gas line L5. An example of the downstream equipment is a liquid fuel synthesis facility for biojet fuels, etc.

[0021] Next, the flows of makeup water, feed water, and steam in the biomass gasification apparatus 10 according to this embodiment will be described. Makeup water (gasifying agent) is introduced from a make-up water supply device (not shown) to the char cooler 16 via a first make-up water line L9. The make-up water introduced to the char cooler 16 is at room temperature. The make-up water introduced to the char cooler 16 is introduced from outside the system. This is because, as described above, the gasifying agent (steam) supplied to the biomass gasifier 11 is converted into carbon monoxide and hydrogen by the water-gas shift reaction and introduced to the downstream equipment, or condensed and recovered in the scrubber 18 and discharged outside the system via the drainage line L18, and therefore it is necessary to replenish the gasifying agent into the system. In the char cooler 16, heat exchange occurs between the char and the make-up water, and the make-up water is heated (heat exchange process). Specifically, the make-up water is heated to approximately 80°C. As will be described later, this make-up water is heated in various devices and then supplied to the biomass gasifier 11, where it is used as part of the gasifying agent when generating biomass gas.

[0022] The makeup water heated in the char cooler 16 is introduced to the biomass supply unit 19 via a second makeup water line (supply unit inlet line) L10 connecting the char cooler 16 and the biomass supply unit 19. The makeup water introduced to the biomass supply unit 19 undergoes heat exchange in a device constituting the biomass supply unit 19 (e.g., a fuel feeder that inputs biomass fuel into the biomass gasifier 11). The device (not shown) constituting the biomass supply unit 19 is heated to a high temperature by the heat of the biomass gasifier 11, and is cooled by heat exchange with the makeup water. If the temperature of the cooling medium cooling the device constituting the biomass supply unit 19 is below the dew point, condensation may occur in the biomass supply unit 19, causing problems such as biomass fuel adhesion and blockage. In this embodiment, makeup water heated to a temperature above the dew point in the char cooler 16 is used as the cooling medium, thereby suppressing the occurrence of condensation. The makeup water that has undergone heat exchange in the device constituting the biomass supply unit 19 is heated by the heat of the device. Specifically, the make-up water is heated to approximately 100°C. The make-up water discharged from the biomass supply unit 19 is guided to the first supply water line L12 via a third make-up water line L11 that connects the biomass supply unit 19 and the supply water line. The make-up water guided to the first supply water line L12 merges with the supply water circulating in the first supply water line L12 and is guided to the supply water preheating unit 17.

[0023] In the feedwater preheating section 17, heat exchange occurs between the heat medium and feedwater (a combination of feedwater introduced from the first feedwater line L12 and make-up water introduced from the third make-up water line L11). In the feedwater preheating section 17, the feedwater is heated by heat exchange with the heat medium, and some or all of it becomes steam. The feedwater is heated in the low-temperature synthesis gas cooler 14 to a temperature that does not cause problems in terms of condensation or impurity precipitation. The steam discharged from the feedwater preheating section 17 is introduced to the low-temperature synthesis gas cooler 14 via the first steam line (cooling section introduction line) L13. In the low-temperature synthesis gas cooler 14, heat exchange occurs between the biomass gas and the steam, and the steam is heated. The steam discharged from the low-temperature synthesis gas cooler 14 is introduced to the high-temperature synthesis gas cooler 12 via the second steam line (cooling section introduction line) L14. In the high-temperature synthesis gas cooler 12, heat exchange occurs between the biomass gas and the steam, and the steam is heated. The steam discharged from the high-temperature synthesis gas cooler 12 is guided as a gasifying agent to the biomass gasifier 11 via the third steam line L15. The steam (gasifying agent) guided to the biomass gasifier 11 is used to generate biomass gas. A portion of the steam (gasifying agent) supplied to the biomass gasifier 11 (excess steam not consumed in the water-gas shift reaction) circulates together with the biomass gas, is condensed and recovered from the biomass gas in the scrubber 18, and is discharged outside the system as wastewater. In addition, a fourth steam line L16 branches off from a position midway through the third steam line L15. The fourth steam line L16 guides a portion of the steam heated in the high-temperature synthesis gas cooler 12 to a steam utilization destination. An example of a steam utilization destination is the feedwater preheater 17. In this case, the steam guided to the feedwater preheater 17 is used as a heat medium to preheat the feedwater. The steam may be used in other devices, such as a biomass preheating unit (not shown) that preheats the biomass fuel to be supplied to the biomass gasifier 11. In this case, the steam introduced to the biomass preheating unit is used as a heat medium to preheat the biomass fuel.

[0024] According to this embodiment, the following advantageous effects are achieved. In this embodiment, heat exchange occurs between the char separated by the filter 13 and the gasifying agent (make-up water) supplied to the biomass gasifier 11, heating the gasifying agent. This allows the heat of the char to preheat the gasifying agent before it is supplied to the biomass gasifier 11. Therefore, in the feedwater preheating section 17 that preheats the gasifying agent to be introduced to the biomass gasifier 11, the energy required in the feedwater preheating section 17 can be reduced by the amount that the gasifying agent is heated in the char cooler 16. In this way, by using the waste heat of the char to preheat the gasifying agent, the energy efficiency of the entire biomass gasification apparatus 10 can be improved compared to when the waste heat of the char is not used.

[0025] Furthermore, the biomass supply unit 19, which supplies biomass fuel to the biomass gasifier 11, is exposed to the heat inside the biomass gasifier 11. For this reason, it is necessary to cool the biomass supply unit 19 to prevent thermal damage, but cooling the biomass supply unit 19 with a cooling medium at room temperature (below the dew point) can cause condensation in the biomass supply unit 19, which can lead to various problems. Therefore, in order to cool the biomass supply unit 19, it is necessary to supply a cooling medium at a relatively high temperature (above the dew point) (for example, about 80°C) to the biomass supply unit 19.

[0026] On the other hand, in this embodiment, heat exchange with the gasifying agent (make-up water) is performed in the biomass supply unit 19. As a result, the biomass supply unit 19 is cooled by the gasifying agent, and thermal damage to the biomass supply unit 19 can be suppressed. Furthermore, in this embodiment, the gasifying agent heated in the char cooler 16 is introduced to the biomass supply unit 19. As a result, a high-temperature gasifying agent can be introduced to the biomass supply unit 19, compared to when a gasifying agent not heated in the char cooler 16 (e.g., a gasifying agent at room temperature) is introduced to the biomass supply unit 19. Therefore, condensation can be made less likely to occur in the biomass supply unit 19. Furthermore, because the exhaust heat of the char is used to heat the gasifying agent introduced to the biomass supply unit 19, energy efficiency can be improved compared to when the exhaust heat of the char is not used.

[0027] In this embodiment, the gasifying agent heated in the biomass supply unit 19 is introduced into the biomass gasifier 11. In this way, the cooling heat of the biomass supply unit 19 is used to preheat the gasifying agent, which improves the energy efficiency of the entire biomass gasification apparatus 10 compared to when the biomass supply unit 19 is cooled with a separate cooling medium.

[0028] The biomass gas generated in the biomass gasifier 11 is extremely hot (e.g., approximately 1000°C). Therefore, the biomass gas discharged from the biomass gasifier 11 is cooled to a predetermined temperature in a biomass gas cooling unit (e.g., the high-temperature synthesis gas cooler 12 or the low-temperature synthesis gas cooler 14). If the temperature of the cooling medium used to cool the biomass gas is too low, tar components derived from the biomass fuel contained in the biomass gas will precipitate on the biomass-side heat transfer surface of the heat exchanger (e.g., a heat transfer tube through which the cooling medium flows) in the biomass gas cooling unit. In particular, in a biomass gasifier that gasifies biomass fuel, the furnace temperature tends to be lower than in, for example, a coal gasifier that gasifies coal, so tar components are more likely to precipitate in the biomass gas cooling unit. Precipitation of tar components on the heat transfer surface of the heat exchanger can cause various problems, such as impeded heat transfer and blocked flow paths. Therefore, the temperature of the cooling medium introduced into the biomass gas cooling unit needs to be relatively high (above the sublimation point of the tar components).

[0029] On the other hand, in this embodiment, the gasifying agent heated in the char cooler 16 is introduced to the low-temperature synthesis gas cooler 14. As a result, a gasifying agent at a higher temperature can be introduced to the low-temperature synthesis gas cooler 14 compared to when a gasifying agent that is not heated in the char cooler 16 is introduced to the low-temperature synthesis gas cooler 14. This makes it possible to suppress the deposition of tar components on the heat transfer surface of the low-temperature synthesis gas cooler 14. Furthermore, because the waste heat of the char is used to heat the gasifying agent introduced to the low-temperature synthesis gas cooler 14, the energy efficiency of the entire biomass gasifier 10 can be improved compared to when the waste heat of the char is not used.

[0030] In this embodiment, make-up water at room temperature is supplied to the char cooler 16. That is, the char is cooled by make-up water at room temperature. This allows the capacity of the cooling equipment to be reduced compared to, for example, a case where cooling water from a cooling equipment (not shown) such as a cooling tower is used to cool the char. Therefore, the power consumed by the cooling equipment and installation costs can be reduced.

[0031] Second Embodiment Next, a biomass gasification plant 100 according to a second embodiment of the present disclosure will be described with reference to FIG. As shown in FIG. 2, the biomass gasification plant 100 according to this embodiment includes a biomass gasification apparatus 20 and a power generation apparatus 30. The biomass gasification apparatus 20 according to this embodiment differs from the biomass gasification apparatus 10 according to the first embodiment in the distribution path of make-up water. Other points are the same as the biomass gasification apparatus 10 according to the first embodiment, so the same components are denoted by the same reference numerals and detailed description thereof will be omitted.

[0032] The biomass gasification apparatus 20 according to this embodiment includes a fourth makeup water line L21 that connects the char cooler 16 and the water supply tank .

[0033] The power generation system 30 includes a boiler 31 that generates steam by burning fuel, a steam turbine 32 that is rotationally driven by the steam generated by the boiler 31, a condenser 33 that condenses steam discharged from the steam turbine 32, a feedwater tank 34 that stores the condensed water condensed by the condenser 33, a feedwater heater 35 that heats the feedwater introduced from the feedwater tank 34, and a deaerator 36 that removes non-condensable gases contained in the feedwater. The feedwater tank 34 is connected to the downstream end of a fourth make-up water line (circulation system introduction line) L21 through which make-up water discharged from the char cooler 16 flows. The power generation system 30 also includes a generator (not shown) that is connected to the steam turbine 32 and generates electricity using the rotational force of the steam turbine 32. Biomass fuel may be used as the fuel used in the boiler 31. The electricity generated by the generator may be used in various devices that constitute the biomass gasification plant 100.

[0034] Next, we will explain the flows of makeup water, feed water, and steam in the biomass gasification system 20 according to this embodiment. Note that the flows of biomass gas, etc. in the biomass gasification system 20 according to this embodiment are substantially similar to the flows of biomass gas, etc. in the biomass gasification system 10 of the first embodiment, so explanations of similar flows will be omitted.

[0035] Make-up water is guided from a make-up water supply device (not shown) to the char cooler 16 via a first make-up water line L9. The temperature of the make-up water guided to the char cooler 16 is room temperature. In the char cooler 16, heat exchange occurs between the char and the make-up water, and the make-up water is heated. The make-up water discharged from the char cooler 16 is guided to the supply water tank 34 via a fourth make-up water line L21 that connects the char cooler 16 and the supply water tank 34.

[0036] The boiler 31 is supplied with, for example, biomass fuel by a fuel supply unit 37. The boiler 31 burns the supplied fuel to evaporate feedwater and generate steam. The steam generated by the boiler 31 is guided to the steam turbine 32 via a fifth steam line L22. The steam guided to the steam turbine 32 drives the steam turbine 32 to rotate. The steam that passes through the steam turbine 32 is guided to the condenser 33 via a sixth steam line L23. The steam guided to the condenser 33 is condensed by heat exchange with cooling water to become condensed water. The condensed water discharged from the condenser 33 is guided to a feedwater tank 34 via a condensate line L24. The feedwater tank 34 stores the condensed water guided via the condensate line L24 and the makeup water guided via the fourth makeup water line L21. In the following description, the condensate water and makeup water will be collectively referred to as feedwater.

[0037] The feedwater discharged from the feedwater tank 34 is guided to the feedwater heater 35 via the second feedwater line L25. In the feedwater heater 35, heat exchange occurs between the heat medium and the feedwater, heating the feedwater. The heat medium used in the feedwater heater 35 is, for example, steam extracted from the steam turbine 32. The feedwater discharged from the feedwater heater 35 is guided to the deaerator 36 via the third feedwater line L26. In the deaerator 36, heat exchange occurs between the heat medium and the feedwater, heating the feedwater and removing non-condensable gases contained in the feedwater. The heat medium used in the deaerator 36 is, for example, steam extracted from the steam turbine 32. A portion of the feedwater discharged from the deaerator 36 is guided to the low-temperature synthesis gas cooler 14 via the fourth feedwater line L27. The feedwater guided to the low-temperature synthesis gas cooler 14 is heated and evaporated by heat exchange with the biomass gas. As in the first embodiment, the steam discharged from the low-temperature synthesis gas cooler 14 is guided to the biomass gasifier 11 as a gasifying agent via the second steam line L14, the high-temperature synthesis gas cooler 12, and the third steam line L15. In this embodiment, the fourth steam line L16 guides a portion of the steam heated in the high-temperature synthesis gas cooler 12 (excess steam not supplied to the biomass gasifier 11 as a gasifying agent) to the fifth steam line L22. That is, the excess steam is guided to the steam turbine 32. In addition, a portion of the feedwater discharged from the deaerator 36 is guided to the boiler 31 via the fifth feedwater line L28. In this way, the steam generated in the boiler 31 is supplied to the steam turbine 32 via the fifth steam line L22, and then circulates by flowing through the sixth steam line L23, the condensate line L24, the second feedwater line L25, the third feedwater line L26, and the fifth feedwater line L28. The various devices that make up the power generation unit 30, as well as the fifth steam line L22, sixth steam line L23, condensate line L24, second feedwater line L25, third feedwater line L26 and fifth feedwater line L28 that connect the various devices, form a circulation system 38 that guides the steam (condensate, feedwater) generated in the boiler 31 and discharged from the steam turbine 32 back to the boiler 31.

[0038] According to this embodiment, the following advantageous effects are achieved. In this embodiment, the gasifying agent (steam) used in the biomass gasification system 20 and the fluid (water) circulating through the circulation system 38 of the power generation system 30 can be made common.

[0039] Furthermore, in this embodiment, the gasifying agent (make-up water) heated in the char cooler 16 is introduced into the circulation system 38. Specifically, the gasifying agent (make-up water) heated in the char cooler 16 is introduced into the feedwater tank 34. This allows the waste heat of the char to be used to heat the steam or feedwater circulating in the circulation system 38. This makes it possible to reduce the energy required to heat the feedwater in the feedwater heater 35. This therefore makes it possible to improve the energy efficiency of the entire biomass gasification plant 100 compared to when the waste heat of the char is not used.

[0040] The present disclosure is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present disclosure.

[0041] For example, in the first embodiment, the makeup water is heated in the char cooler 16 and the biomass supply unit 19 and then introduced into the first feedwater line L12, but the present disclosure is not limited to this. For example, the makeup water may be heated only in the char cooler 16 and introduced into the first feedwater line L12.

[0042] Furthermore, in the second embodiment, the make-up water is heated only in the char cooler 16 and introduced into the water supply tank 34, but the present disclosure is not limited to this. For example, similar to the first embodiment, the make-up water discharged from the char cooler 16 may be introduced into the biomass supply unit 19. In this case, the make-up water discharged from the biomass supply unit 19 is introduced into the water supply tank 34. In this way, the cooling heat of the biomass supply unit 19 can also be utilized, thereby further improving the energy efficiency of the entire biomass gasification plant 100.

[0043] Furthermore, in the first embodiment, an example in which the feedwater preheating unit 17 is provided has been described, but the present disclosure is not limited to this. For example, if the makeup water introduced into the first feedwater line L12 is sufficiently heated in the char cooler 16 and the biomass supply unit 19 and has a temperature that is acceptable for introduction into the low-temperature synthesis gas cooler 14, the feedwater preheating unit 17 may be omitted.

[0044] The biomass gasification apparatus, biomass gasification plant, and method for producing biomass gas described in the above-described embodiments can be understood, for example, as follows. A biomass gasification apparatus according to one embodiment of the present disclosure includes a gasification furnace (11) that produces biomass gas from biomass fuel and a gasifying agent, a separation section (13) that separates char from the biomass gas discharged from the gasification furnace (11), and a heat exchange section (16) that exchanges heat between the char separated in the separation section (13) and at least a portion of the gasifying agent to be supplied to the gasification furnace (11), thereby heating the gasifying agent.

[0045] In the above configuration, heat is exchanged between the char separated in the separation unit and the gasifying agent to be supplied to the gasifier, heating the gasifying agent. This allows the heat of the char to preheat the gasifying agent before it is supplied to the gasifier. Therefore, for example, if a preheating device that preheats the gasifying agent to be introduced into the gasifier is provided separately from the heat exchange unit, energy consumption in the preheating device can be reduced by the amount of energy consumed by heating the gasifying agent in the heat exchange unit. By using the waste heat of the char to preheat the gasifying agent in this way, the energy efficiency of the entire biomass gasification system can be improved compared to when the waste heat of the char is not used.

[0046] Furthermore, a biomass gasification apparatus according to one embodiment of the present disclosure includes a supply unit (19) that supplies the biomass fuel to the gasification furnace (11), and a supply unit introduction line (L10) that introduces the gasifying agent that has undergone heat exchange in the heat exchange unit (16) to the supply unit (19). The supply unit (19) exchanges heat with the gasifying agent introduced from the heat exchange unit (16), and the gasifying agent that has undergone heat exchange in the supply unit (19) is introduced to the gasification furnace (11).

[0047] The supply section, which supplies biomass fuel to the gasifier, is exposed to the heat inside the biomass gasifier. Therefore, it is necessary to cool the supply section to prevent thermal damage. However, if the supply section is cooled with a cooling medium below the dew point, condensation may occur in the supply section, causing various problems. Therefore, in order to cool the supply section, it is necessary to supply a cooling medium at a temperature above the dew point (for example, around 80°C) to the supply section. In the above configuration, the supply unit exchanges heat with the gasifying agent. As a result, the supply unit is cooled by the gasifying agent, and thermal damage to the supply unit can be suppressed. Furthermore, in the above configuration, the gasifying agent heated by the heat exchange unit is introduced to the supply unit. As a result, a high-temperature gasifying agent can be introduced to the supply unit compared to when a gasifying agent not heated by the heat exchange unit is introduced to the supply unit. Therefore, condensation can be made less likely to occur in the supply unit. Furthermore, because the exhaust heat of the char is used to heat the gasifying agent introduced to the supply unit, energy efficiency can be improved compared to when the exhaust heat of the char is not used. In addition, in the above configuration, the gasifying agent heated in the supply unit is introduced into the gasification furnace. In this way, the cooling heat of the supply unit is used to heat the gasifying agent, which improves the energy efficiency of the entire biomass gasification system compared to when the exhaust heat of the supply unit is not used.

[0048] Furthermore, a biomass gasification apparatus according to one embodiment of the present disclosure includes a biomass gas cooling unit (12, 14) that cools the biomass gas, and a cooling unit introduction line (L10) that introduces the gasifying agent heated in the heat exchange unit (16) to the biomass gas cooling unit (12, 14), and the biomass gas cooling unit (12, 14) cools the biomass gas by exchanging heat between the biomass gas and the gasifying agent.

[0049] Biomass gas generated in a biomass gasifier is extremely hot (e.g., about 1000°C). Therefore, the biomass gas discharged from the biomass gasifier is cooled to a predetermined temperature in a biomass gas cooler. If the temperature of the cooling medium used to cool the biomass gas is too low, tar components in the biomass gas will precipitate on the heat transfer surface on the biomass gas side of the heat exchanger (e.g., a heat transfer tube through which the cooling medium flows) in the biomass gas cooler. In particular, in a biomass gasifier that gasifies biomass fuel, the furnace temperature tends to be lower than in a coal gasifier that gasifies coal, for example, and tar components are more likely to precipitate in the biomass gas cooler. If tar components precipitate on the heat transfer surface of the heat exchanger, it may cause various problems, such as impeded heat transfer and blockage of the flow path. For this reason, the temperature of the cooling medium introduced into the biomass gas cooler needs to be relatively high (above the sublimation point of the tar components). In the above configuration, the gasifying agent heated in the heat exchanger is introduced to the biomass gas cooler. This allows a higher temperature gasifying agent to be introduced to the biomass gas cooler than when a gasifying agent not heated in the heat exchanger is introduced to the biomass gas cooler. Therefore, deposition of tar components on the heat transfer surface of the heat exchanger in the biomass gas cooler can be suppressed. Furthermore, because the waste heat of the char is used to heat the gasifying agent introduced to the biomass gas cooler, the energy efficiency of the entire biomass gasification system can be improved compared to when the waste heat of the char is not used.

[0050] A biomass gasification plant according to one aspect of the present disclosure includes any one of the biomass gasification apparatuses (10, 20) described above, a boiler (31) that generates steam by burning fuel, a steam turbine (32) that is rotationally driven by the steam generated in the boiler (31), a generator that generates electricity by the rotational force of the steam turbine (32), a circulation system (38) that introduces feedwater formed by condensing the steam discharged from the steam turbine (32) to the boiler (31), and a circulation system introduction line (L21) that introduces the gasifying agent heated in the heat exchange section (16) to the circulation system (38), wherein the gasifying agent is water vapor.

[0051] In the above configuration, the gasifying agent used in the biomass gasification system is steam, which allows the biomass gasification system and the circulation system to share the same fluid (supply water or steam). In addition, in the above configuration, the gasifying agent heated in the heat exchanger is introduced into the circulation system. This allows the waste heat of the char to be used to heat the steam or feedwater circulating in the circulation system. Therefore, the energy efficiency of the entire biomass gasification plant can be improved compared to when the waste heat of the char is not used.

[0052] A method for producing biomass gas according to one embodiment of the present disclosure includes a generation process for generating biomass gas from biomass fuel and a gasifying agent in a gas furnace (11), a separation process for separating char from the biomass gas generated in the generation process and discharged from the gasification furnace (11), and a heat exchange process for exchanging heat between the char separated in the separation process and at least a portion of the gasifying agent to be supplied to the gasification furnace (11) to heat the gasifying agent, and in the generation process, biomass gas is generated using the gasifying agent heated in the heat exchange process. [Explanation of symbols]

[0053] 10: Biomass gasification equipment 11: Biomass gasifier (gasifier) 12: High-temperature synthesis gas cooler (biomass gas cooling section) 13: Filter (separation part) 14: Low-temperature synthesis gas cooler (biomass gas cooling section) 15: Char hopper 16: Charcoal cooler (heat exchange section) 17: Water supply preheating section 18: Scrubba 19: Biomass Supply Department (Supply Department) 20: Biomass gasification equipment 30: Power generating equipment 31: Boiler 32: Steam turbine 33: Condenser 34: Water tank 35: Feed water heater 36: Deaerator 37:Fuel supply section 38: Circulatory system 100: Biomass gasification plant L1: First biomass gas line L2: Second biomass gas line L3: Third biomass gas line L4: 4th biomass gas line L5: 5th biomass gas line L6: 1st Char Line L7: Second Char Line L8: 3rd Char Line L9: First make-up water line L10: Second makeup water line (supply section introduction line) L11: Third make-up water line L12: First water supply line L13: First steam line (cooling section introduction line) L14: Second steam line (cooling section introduction line) L15: Third steam line L16: 4th steam line L17: Oxygen line L18: Drain line L21: 4th makeup water line (circulation system introduction line) L22: 5th steam line L23: No. 6 steam line L24: Condensate line L25: Second water supply line L26: Third water supply line L27: 4th water supply line L28: 5th water supply line

Claims

1. a gasification furnace for generating biomass gas from biomass fuel and a gasifying agent; a separation unit that separates char from the biomass gas discharged from the gasification furnace; a heat exchange unit that exchanges heat between the char separated in the separation unit and at least a portion of the gasifying agent to be supplied to the gasification furnace, thereby heating the gasifying agent.

2. a supply unit that supplies the biomass fuel to the gasification furnace; a supply section introduction line that introduces the gasifying agent that has been heat exchanged in the heat exchange section to the supply section, the supply unit performs heat exchange with the gasifying agent introduced from the heat exchange unit, The biomass gasification apparatus according to claim 1 , wherein the gasifying agent that has undergone heat exchange in the supply section is introduced into the gasification furnace.

3. a biomass gas cooling unit that cools the biomass gas; a cooling section introduction line that introduces the gasifying agent heated in the heat exchange section to the biomass gas cooling section, 3. The biomass gasification apparatus according to claim 1, wherein the biomass gas cooling unit cools the biomass gas by exchanging heat between the biomass gas and the gasifying agent.

4. The biomass gasification apparatus according to any one of claims 1 to 3; a boiler that generates steam by burning fuel; a steam turbine that is rotationally driven by the steam generated in the boiler; a generator that generates electricity using the rotational force of the steam turbine; a circulation system that introduces feedwater obtained by condensing the steam discharged from the steam turbine to the boiler; a circulation system introduction line that introduces the gasifying agent heated in the heat exchange unit into the circulation system, A biomass gasification plant, wherein the gasifying agent is water vapor.

5. a generation step of generating biomass gas from the biomass fuel and the gasifying agent in a gasification furnace; a separation step of separating char from the biomass gas generated in the generation step and discharged from the gasification furnace; a heat exchange step of exchanging heat between the char separated in the separation step and at least a part of the gasifying agent to be supplied to the gasification furnace, thereby heating the gasifying agent; A biomass gas production method in which the generating step generates the biomass gas using the gasifying agent heated in the heat exchange step.

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