Gasification furnace system and method for controlling gasification furnace system

Abstract

Provided is a gasification furnace system that allows continuous operation over a long period of time. The present invention comprises: a gasification furnace that generates a synthesis gas from a biomass raw material; a high-temperature scrubber (70) to which the synthesis gas generated in the gasification furnace is introduced; a medium-temperature scrubber (80) to which the synthesis gas discharged from the high-temperature scrubber (70) is introduced; and a control device which performs control such that the temperature of scrubber water (W1) stored in the high-temperature scrubber (70) is 80°C to 95°C. The control device performs control such that the temperature of scrubber water (W2) stored in the medium-temperature scrubber (80) is 20°C to 40°C.

Description

Gasification furnace system and method for controlling gasification furnace system

[0001] The present disclosure relates to a gasifier system and a method for controlling a gasifier system.

[0002] BACKGROUND ART A gasification furnace is known in which a biomass raw material is supplied into a furnace, and the biomass raw material is combusted and gasified in the furnace to produce a synthesis gas of carbon monoxide and hydrogen (see, for example, Patent Document 1).

[0003] The system described in Patent Document 1 includes a biomass supply device that dries and supplies biomass raw materials, a gasification furnace that gasifies the supplied biomass raw materials to produce synthesis gas, an air preheater that cools the synthesis gas produced in the gasification furnace, a filter device that collects foreign matter in the synthesis gas that has passed through the air preheater, and a scrubber device.

[0004] Patent No. 6345139

[0005] Biomass raw materials include, for example, wood chips, wood pellets, agricultural residues, and forest residues, which contain not only C, H, and O, which are the raw materials for synthesis gas, but also impurities. Therefore, synthesis gas obtained by gasifying biomass raw materials contains a certain amount of tar. To remove tar from synthesis gas, filters and scrubbers are generally used.

[0006] However, tar treatment using filters and scrubbers can pose maintenance problems, such as stable operation and running costs. For example, when tar passes through a scrubber using room-temperature water, most tar components with relatively high boiling points can be removed. However, tar components with particularly high melting points become viscous as they cool in the scrubber water, which can cause them to adhere to the drainage system and cause blockages. This requires frequent shutdowns and cleaning. Furthermore, many tar components with relatively low boiling points adhere to the filter, necessitating frequent replacement.

[0007] As described above, synthesis gas derived from biomass feedstock contains tar components with a wide range of boiling points, which necessitates cleaning of the scrubber and replacement of the filters, making it difficult to operate continuously for long periods of time.

[0008] The present disclosure has been made in consideration of the above circumstances, and aims to provide a gasification furnace system capable of continuous operation over long periods of time, and a method for controlling a gasification furnace system.

[0009] A gasification furnace system according to one aspect of the present disclosure includes a gasification furnace that produces synthesis gas from biomass feedstock, a first scrubber to which the synthesis gas produced in the gasification furnace is introduced, a second scrubber to which the synthesis gas discharged from the first scrubber is introduced, and a control device that controls the temperature of scrubber water stored in the first scrubber to be at least 80°C and below the boiling point.

[0010] A control method for a gasification furnace system according to one aspect of the present disclosure is a control method for a gasification furnace system including a gasification furnace that produces synthesis gas from biomass feedstock, a first scrubber to which the synthesis gas produced in the gasification furnace is introduced, and a second scrubber to which the synthesis gas discharged from the first scrubber is introduced, and the method controls the temperature of scrubber water stored in the first scrubber to be at least 80°C and below the boiling point.

[0011] The gasification furnace system and the control method thereof according to the present disclosure enable continuous operation over long periods of time.

[0012] 1 is a schematic diagram illustrating a gasification furnace system according to an embodiment of the present disclosure.

[0013] An embodiment of the present disclosure will be described below with reference to the drawings. A gasification furnace system 1 according to this embodiment is a system that generates synthesis gas (a mixture of carbon monoxide and hydrogen) from biomass feedstock. The generated synthesis gas can be used as fuel for power generation equipment such as gas turbines and gas engines, or as a raw material for synthetic liquid fuels (e.g., aviation fuel) such as biofuels produced using the Fischer-Tropsch process (FT process).

[0014] As shown in FIG. 1 , the gasification furnace system 1 includes a gasification furnace 10, a high-temperature gas cooler 20, an ash removal section 30, a low-temperature gas cooler (gas cooler) 40, a scrubber 50, and a control device 60.

[0015] Oxygen, steam, and biomass raw materials are fed into the gasifier 10. The gasifier 10 reacts the fed oxygen, steam, and biomass raw materials to raise the temperature, and produces synthesis gas (carbon monoxide (CO) and hydrogen (H ２ The gasifier 10 discharges the generated synthesis gas. The temperature of the synthesis gas discharged from the gasifier 10 is set to about 800°C or higher and 1200°C or lower.

[0016] Examples of biomass raw materials that can be fed into the gasifier 10 include wood chips, wood pellets, agricultural residues, and forest residues. These biomass raw materials contain not only carbon (C), hydrogen (H), and oxygen (O), which are the raw materials for synthesis gas, but also impurities. Among the impurities, ash (mainly composed of silicon (Si), calcium (Ca), etc.) may melt in the gasifier depending on its properties, but most of it remains as ash and is transported downstream with the flow of synthesis gas. In other words, the synthesis gas discharged from the gasifier 10 contains ash and the like.

[0017] Each device (not shown) that feeds oxygen, steam, and biomass feedstock into the gasifier 10 is provided with an adjustment unit (not shown) that adjusts the amount of feed. The gasifier system 1 controls the amount, temperature, and composition (ratio of hydrogen to carbon monoxide) of the synthesis gas discharged from the gasifier 10 by adjusting the amounts of oxygen, steam, and biomass feedstock fed using the control device 60. Adjusting the amounts of oxygen, steam, and biomass feedstock fed optimizes the efficiency of, for example, a liquid fuel synthesis device (a device that produces liquid fuel from synthesis gas, not shown) provided downstream of the scrubber 50.

[0018] The gasifier 10 and the high-temperature gas cooler 20 are connected by a first synthesis gas pipe L1. Synthesis gas flows inside the first synthesis gas pipe L1. The first synthesis gas pipe L1 guides the synthesis gas discharged from the gasifier 10 to the high-temperature gas cooler 20. The first synthesis gas pipe L1 is provided with a gas thermometer 11 that measures the temperature of the synthesis gas flowing inside. The gas thermometer 11 transmits the measured information to the control device 60.

[0019] The synthesis gas discharged from the gasifier 10 is introduced into the high-temperature gas cooler 20. The high-temperature gas cooler 20 cools the supplied synthesis gas by exchanging heat with a cooling medium (steam or water in this embodiment).

[0020] The high-temperature gas cooler 20 has a first high-temperature heat exchange section 21 provided therein and a second high-temperature heat exchange section 22 provided downstream of the first high-temperature heat exchange section 21 in the flow of synthesis gas.

[0021] The first high-temperature heat exchange unit 21 has a plurality of heat transfer tubes (not shown) provided inside the high-temperature gas cooler 20. Steam flows inside the heat transfer tubes. The first high-temperature heat exchange unit 21 cools the synthesis gas and heats the steam by exchanging heat between the steam flowing inside the heat transfer tubes and the synthesis gas. The steam discharged from the first high-temperature heat exchange unit 21 is supplied to the gasifier 10 via the first cooling medium pipe L11.

[0022] The second high-temperature heat exchange unit 22 has a plurality of heat transfer tubes (not shown) provided inside the high-temperature gas cooler 20. Water vapor flows inside the heat transfer tubes. The second high-temperature heat exchange unit 22 cools the synthesis gas and heats the water vapor by exchanging heat between the water vapor flowing inside the heat transfer tubes and the synthesis gas. Water vapor is supplied to the second high-temperature heat exchange unit 22 via a third cooling medium pipe L13. In addition, the water vapor discharged from the second high-temperature heat exchange unit 22 is supplied to the first high-temperature heat exchange unit 21 via a second cooling medium pipe L12.

[0023] The second cooling medium pipe L12 is supplied with spray water from the spray water pipe L20. The spray water pipe L20 branches off from the fourth cooling medium pipe L14 (see *1 in the figure). That is, the spray water pipe L20 connects the fourth cooling medium pipe L14 and the second cooling medium pipe L12. The spray water pipe L20 supplies a portion of the water and steam discharged from a second low-temperature heat exchanger 42 of the low-temperature gas cooler 40 (described later) to the steam circulating in the second cooling medium pipe L12. The spray water pipe L20 is provided with an adjustment mechanism (not shown) that adjusts the amount of water and steam supplied to the steam circulating in the second cooling medium pipe L12. The adjustment mechanism is controlled by the control device 60.

[0024] A gas bypass pipe L8 is also connected to the high-temperature gas cooler 20. The gas bypass pipe L8 extracts a portion of the synthesis gas from between the first high-temperature heat exchange section 21 and the second high-temperature heat exchange section 22, and guides the extracted synthesis gas to the downstream side of the second high-temperature heat exchange section 22. In other words, the gas bypass pipe L8 is provided so as to bypass the second high-temperature heat exchange section 22. A flow rate adjustment damper 27 is provided in the gas bypass pipe L8. The flow rate adjustment damper 27 adjusts the opening degree to adjust the flow rate of the synthesis gas circulating therethrough. The opening degree of the flow rate adjustment damper 27 is controlled by the control device 60.

[0025] The high-temperature gas cooler 20 and the gasifier 10 are connected by a first cooling medium pipe L11. Heated steam flows through the first cooling medium pipe L11. The first cooling medium pipe L11 guides steam discharged from the high-temperature gas cooler 20 (more specifically, the first high-temperature heat exchange section 21) to the gasifier 10. The first cooling medium pipe L11 is provided with a cooling medium thermometer 23 that measures the temperature of the steam flowing therethrough, a cooling medium pressure gauge 24 that measures the pressure of the steam flowing therethrough, and a cooling medium flowmeter 25 that measures the flow rate of the steam flowing therethrough. The cooling medium thermometer 23, the cooling medium pressure gauge 24, and the cooling medium flowmeter 25 transmit measured information to the control device 60.

[0026] The high-temperature gas cooler 20 and the ash removal section 30 are connected by a second synthesis gas pipe L2. Synthesis gas flows through the second synthesis gas pipe L2. The second synthesis gas pipe L2 guides the synthesis gas discharged from the high-temperature gas cooler 20 to the ash removal section 30. A gas thermometer 26 that measures the temperature of the synthesis gas flowing through the second synthesis gas pipe L2 is provided in the second synthesis gas pipe L2. The gas thermometer 26 transmits the measured information to the control device 60. The second synthesis gas pipe L2 branches at its downstream portion so as to be connected to multiple ash removal sections 30. A first on-off valve 28 is provided in each of the branched second synthesis gas pipes L2. The first on-off valve 28 is controlled by the control device 60.

[0027] The high-temperature gas cooler 20 cools the supplied synthesis gas to a temperature of approximately 350° C. or higher and 500° C. or lower. The gasification furnace system 1 uses the control device 60 to adjust the amount of spray fluid introduced into the high-temperature gas cooler 20 via the spray water piping L20, the bypass flow rate of synthesis gas through the gas bypass piping L8, and the like, thereby adjusting the temperature of the synthesis gas discharged from the high-temperature gas cooler 20.

[0028] The high-temperature gas cooler 20 is provided with a soot blower (not shown). The soot blower sprays a blowing medium onto the surfaces of the heat transfer tubes of the first high-temperature heat exchange section 21 and the second high-temperature heat exchange section 22 provided inside the high-temperature gas cooler 20, thereby removing ash that has adhered to and accumulated on the surfaces of the heat transfer tubes. The blowing medium is supplied from the outside of the high-temperature gas cooler 20 via a blowing medium line L21. The soot blower also plays a role in assisting in regulating the temperature of the synthesis gas by adjusting the amount of heat exchanged in the first high-temperature heat exchange section 21 and the second high-temperature heat exchange section 22. Examples of the blowing medium include nitrogen, steam, and carbon dioxide.

[0029] The synthesis gas discharged from the high-temperature gas cooler 20 is guided to the ash removal section 30. The ash removal section 30 collects ash contained in the supplied synthesis gas. A plurality of ash removal sections 30 (two in this embodiment) are provided in parallel in the synthesis gas flow. Since the structures of the plurality of ash removal sections 30 are substantially identical, the following description will be given of one ash removal section 30 as a representative.

[0030] The ash removal section 30 includes a gas filter 31 that collects ash contained in the synthesis gas, a housing 32 that houses the gas filter 31 inside, a backwash pipe L25 that backwashes the gas filter 31, and a discharge pipe L26 that discharges the ash.

[0031] The gas filter 31 is a mesh member made of sintered metal, ceramic, glass fiber, or the like. The gas filter 31 allows the synthesis gas to pass through and collects ash contained in the synthesis gas. The heat resistance temperature of the gas filter 31 is set to a temperature corresponding to the temperature of the synthesis gas to be supplied (for example, approximately 350°C to 500°C).

[0032] A backwash gas (for example, an inert medium such as steam, nitrogen, or carbon dioxide gas) supplied from the backwash pipe L25 is sprayed onto the gas filter 31. This causes the ash captured on the gas filter 31 to fall from the gas filter 31. The fallen ash temporarily accumulates on the bottom of the housing 32. A backwash valve 33 is provided in the backwash pipe L25. The opening and closing of the backwash valve 33 is controlled by the control device 60.

[0033] A discharge pipe L26 is connected to the bottom of the housing 32. The discharge pipe L26 discharges ash accumulated on the bottom of the housing 32 to the outside of the system. A discharge valve 34 is provided on the discharge pipe L26. The opening and closing of the discharge valve 34 is controlled by the control device 60.

[0034] A plurality of ash removal units 30 are provided in parallel to prevent ash from adhering to the surface of the gas filter 31 and causing clogging during long-term operation. The control device 60 switches the system through which the synthesis gas flows using the first on-off valve 28, and backwashes the gas filter 31 in the system through which the synthesis gas is not flowing with backwash gas to remove ash adhering to the filter surface.

[0035] The ash removal unit 30 and the low-temperature gas cooler 40 are connected by a third synthesis gas pipe L3. Synthesis gas flows through the third synthesis gas pipe L3. The third synthesis gas pipe L3 guides the synthesis gas discharged from the ash removal unit 30 to the low-temperature gas cooler 40.

[0036] The third synthesis gas pipe L3 has an upstream portion that branches off to connect to multiple ash removal units 30. That is, the branch pipes extending from the ash removal units 30 join together to form a single third synthesis gas pipe L3 that is connected to the low-temperature gas cooler 40. Each of the branched third synthesis gas pipes L3 is provided with a second on-off valve 35. The second on-off valve 35 is controlled by the control device 60.

[0037] The synthesis gas discharged from the ash removal section 30 is guided to the low-temperature gas cooler 40. The low-temperature gas cooler 40 cools the supplied synthesis gas by exchanging heat with a cooling medium (steam or water in this embodiment).

[0038] The synthesis gas flows through the low-temperature gas cooler 40. The low-temperature gas cooler 40 has a first low-temperature heat exchanger 41 provided therein, a second low-temperature heat exchanger 42 provided downstream of the first low-temperature heat exchanger 41 in the synthesis gas flow direction, a steam drum 43 that separates water (cooling water) from steam, and a water supply pump 44 that supplies water to the second low-temperature heat exchanger 42.

[0039] The first low-temperature heat exchanger 41 has a plurality of heat transfer tubes (not shown) provided inside the low-temperature gas cooler 40. Water and steam flow through the heat transfer tubes. The first low-temperature heat exchanger 41 exchanges heat between the synthesis gas and the water and steam flowing through the heat transfer tubes, thereby cooling the synthesis gas and heating the water and steam. Water (cooling water) stored in the liquid phase of the steam drum 43 is supplied to the first low-temperature heat exchanger 41. The water and steam discharged from the first low-temperature heat exchanger 41 are guided to the steam drum 43 via a fifth cooling medium pipe L15.

[0040] The second low-temperature heat exchanger 42 has a plurality of heat transfer tubes (not shown) provided inside the low-temperature gas cooler 40. Water and water vapor flow through the heat transfer tubes. The second low-temperature heat exchanger 42 exchanges heat between the synthesis gas and the water and water vapor flowing through the heat transfer tubes, thereby cooling the synthesis gas and heating the water and water vapor. Water (cooling water) is supplied to the second low-temperature heat exchanger 42 from a water supply pump 44. The water and water vapor discharged from the second low-temperature heat exchanger 42 are guided to the steam drum 43 via a fourth cooling medium pipe L14.

[0041] The steam in the steam drum 43 is supplied to the high-temperature gas cooler 20 (more specifically, the second high-temperature heat exchange section 22) via the third cooling medium pipe L13. The steam drum 43 is provided with a level meter 45 that detects the liquid level of the water stored therein.

[0042] The low-temperature gas cooler 40 is provided with a soot blower (not shown). The soot blower sprays a spray medium onto the surfaces of the heat transfer tubes of the first low-temperature heat exchange section 41 and the second low-temperature heat exchange section 42 provided inside the low-temperature gas cooler 40, removing ash and tar that has adhered to or accumulated on the surfaces of the heat transfer tubes. The spray medium is supplied from outside the low-temperature gas cooler 40 via a spray medium line L22. The soot blower also plays a role in assisting in temperature regulation of the synthesis gas by adjusting the amount of heat exchanged in the first low-temperature heat exchange section 41 and the second low-temperature heat exchange section 42. Examples of the spray medium include nitrogen, steam, and carbon dioxide.

[0043] In the low-temperature gas cooler 40, the synthesis gas is cooled to, for example, 200° C. or higher and 350° C. or lower. The cooling temperature in the low-temperature gas cooler 40 is determined according to the boiling points of the tar components contained in the synthesis gas. This is because tar components with high boiling points become more viscous as the temperature decreases, making them difficult to remove with a soot blower.

[0044] A first tar pipe L23 for discharging tar is connected to the low-temperature gas cooler 40. The first tar pipe L23 discharges the tar removed from the surface of the heat transfer tube by the soot blower to the outside of the system.

[0045] The low-temperature gas cooler 40 and the scrubber 50 are connected by a fourth synthesis gas pipe L4. The synthesis gas flows through the fourth synthesis gas pipe L4. The fourth synthesis gas pipe L4 guides the synthesis gas discharged from the low-temperature gas cooler 40 to the scrubber 50.

[0046] The synthesis gas discharged from the low-temperature gas cooler 40 is introduced into the scrubber 50. The scrubber 50 cleans the supplied synthesis gas and removes tar in the synthesis gas that was not removed by the low-temperature gas cooler 40. The scrubber 50 cools the synthesis gas by bringing cooling water (cleaning water) into contact with the synthesis gas, and collects tar contained in the synthesis gas together with the cooling water. The specific configuration of the scrubber 50 will be described later.

[0047] A fifth synthesis gas pipe L5 that discharges synthesis gas is connected to the scrubber 50. The fifth synthesis gas pipe L5 supplies the synthesis gas discharged from the scrubber 50 to a supply destination. Examples of the supply destination include a power generation facility and a liquid fuel synthesis unit that produces liquid fuels such as biofuels.

[0048] The fifth synthesis gas pipe L5 is provided with a gas flow meter 51 that measures the flow rate of the synthesis gas flowing therethrough and a gas analyzer 52 that analyzes the components of the synthesis gas flowing therethrough. The gas analyzer 52 measures carbon monoxide (C), hydrogen (H ２ ), oxygen (O ２ ), carbon dioxide (CO ２ The gas flow meter 51 and the gas analyzer 52 transmit the measured information to the control device 60.

[0049] The control device 60 controls each operation of the gasification furnace system 1. The control device 60 includes, for example, a CPU (Central Processing Unit), a main memory, and a secondary storage. The control device 60 may further include a communication unit for transmitting and receiving information to and from other devices. The main memory is configured with, for example, a writable memory such as a cache memory or a RAM (Random Access Memory), and is used as a working area for reading the CPU's execution program and writing processing data by the execution program. The secondary storage is a non-transitory computer-readable storage medium. Examples of secondary storage devices include magnetic disks, magneto-optical disks, CD-ROMs, DVD-ROMs, and semiconductor memories. For example, a series of processes for realizing various functions is stored in the secondary storage device in the form of a program, and the CPU reads this program into the main storage device and executes information processing and arithmetic operations to realize various functions. The program may be pre-installed in the secondary storage device, provided in a state stored in a computer-readable storage medium, or distributed via wired or wireless communication means. Examples of computer-readable storage media include magnetic disks, magneto-optical disks, CD-ROMs, DVD-ROMs, and semiconductor memories.

[0050] <Specific Configuration of Scrubber 50> Fig. 2 shows a specific configuration of the scrubber 50. Note that although the low-temperature gas cooler 40 is shown in a simplified manner in Fig. 2, the detailed configuration of the low-temperature gas cooler 40 is as described in Fig. 1.

[0051] The scrubber 50 includes a plurality of wet scrubbers, specifically a high-temperature scrubber (first scrubber) 70, a medium-temperature scrubber (second scrubber) 80, and a low-temperature scrubber (third scrubber) 90.

[0052] The high-temperature scrubber 70 is connected via a fourth synthesis gas pipe L4 downstream of the low-temperature gas cooler 40. Synthesis gas at a temperature of, for example, 200°C or higher and 350°C or lower is introduced into the high-temperature scrubber 70.

[0053] The high-temperature scrubber 70 includes a container 71 into which synthesis gas is guided from the fourth synthesis gas pipe L4, an injection section 72 that injects cooling water into the container 71, and a cooling water supply pipe 73 that supplies cooling water to the injection section 72.

[0054] A cooling water tank 75 is connected to the cooling water supply pipe 73 via a cooling water pump 74 whose flow rate is adjustable. The flow rate discharged from the cooling water pump 74 is controlled by the control device 60. The cooling water tank 75 stores water at room temperature.

[0055] Cooling water supplied from a cooling water tank 75 by a cooling water pump 74 is sprayed from a spray unit 72 into the container 71. The sprayed cooling water absorbs tar from the synthesis gas in the container 71 and is stored in the lower part of the container 71 as scrubber water W1.

[0056] A portion of the scrubber water W1 is discharged to the outside together with the tar through a drain pipe 76. A water temperature sensor 77 that measures the temperature of the drain water is provided in the drain pipe 76. The measurement value of the water temperature sensor 77 is sent to the control device 60 (see FIG. 1).

[0057] A high-temperature scrubber syngas pipe L41 is connected to the gas phase part of the vessel 71. The high-temperature scrubber syngas pipe L41 is connected to the medium-temperature scrubber 80. A gas temperature sensor 79 that measures the temperature of the syngas is provided in the high-temperature scrubber syngas pipe L41. The measurement value of the gas temperature sensor 79 is sent to the control device 60.

[0058] The control device 60 controls the flow rate of the cooling water pump 74 based on the measurement values ​​of the water temperature sensor 77 and / or the gas temperature sensor 79, and controls the temperature of the scrubber water W1 to be, for example, 80°C or higher and 95°C or lower.

[0059] The intermediate-temperature scrubber 80 is connected via a high-temperature scrubber synthesis gas pipe L41 downstream of the high-temperature scrubber 70. Synthesis gas at a temperature of, for example, 80°C or higher and 95°C or lower is introduced into the intermediate-temperature scrubber 80.

[0060] The medium-temperature scrubber 80 comprises a container 81 into which synthesis gas is guided from the high-temperature scrubber synthesis gas pipe L41, an injection section 82 that injects cooling water into the container 81, and a cooling water supply pipe 83 that supplies cooling water to the injection section 82.

[0061] A cooling water tank 85 is connected to the cooling water supply pipe 83 via a cooling water pump 84 whose flow rate is adjustable. The flow rate discharged from the cooling water pump 84 is controlled by the control device 60. The cooling water tank 85 stores water at room temperature.

[0062] Cooling water supplied from a cooling water tank 85 by a cooling water pump 84 is sprayed into the container 81 from the spray unit 82. The sprayed cooling water absorbs tar from the synthesis gas in the container 81 and is stored as scrubber water W2 in the lower part of the container 81. A portion of the scrubber water W2 is discharged to the outside together with the tar via a drain pipe 86. A water temperature sensor 87 that measures the temperature of the drained water is provided in the drain pipe 86. The measurement value of the water temperature sensor 87 is sent to the control device 60.

[0063] The intermediate-temperature scrubber syngas pipe L42 is connected to the gas phase part of the vessel 81. The intermediate-temperature scrubber syngas pipe L42 is connected to the low-temperature scrubber 90. The intermediate-temperature scrubber syngas pipe L42 is provided with a gas temperature sensor 89 that measures the temperature of the syngas. The measurement value of the gas temperature sensor 89 is sent to the control device 60.

[0064] The control device 60 controls the flow rate of the cooling water pump 84 based on the measurement values ​​of the water temperature sensor 87 and / or the gas temperature sensor 89, and controls the temperature of the scrubber water W2 to be, for example, between 20°C and 40°C (around atmospheric temperature).

[0065] The low-temperature scrubber 90 is connected via a medium-temperature scrubber synthesis gas pipe L42 downstream of the medium-temperature scrubber 80. To the low-temperature scrubber 90, synthesis gas at a temperature of, for example, 20°C or higher and 40°C or lower is introduced.

[0066] The low-temperature scrubber 90 comprises a container 91 into which synthesis gas is guided from the medium-temperature scrubber synthesis gas pipe L42, an injection section 92 that injects cooling water into the container 91, and a cooling water supply pipe 93 that supplies cooling water to the injection section 92.

[0067] A cooling water tank 95 is connected to the cooling water supply pipe 93 via a cooling water pump 94 and a chiller 100. The chiller 100 is controlled by the control device 60, and the cooling water is cooled to a desired temperature. The flow rate of the cooling water pump 94 may also be adjusted by the control device 60. The cooling water tank 95 stores water at room temperature.

[0068] Cooling water supplied from a cooling water tank 95 by a cooling water pump 94 and cooled by a chiller 100 is sprayed from the spray unit 92 into the container 91. The sprayed cooling water absorbs tar from the synthesis gas in the container 91 and is stored as scrubber water W3 in the lower part of the container 91. A portion of the scrubber water W3 is discharged to the outside via a drain pipe 96. The drain pipe 96 is provided with a water temperature sensor 97 that measures the temperature of the drained water. The measurement value of the water temperature sensor 97 is sent to the control device 60.

[0069] A fifth synthesis gas pipe L5 is connected to the gas phase part of the vessel 91. A gas temperature sensor 99 that measures the temperature of the synthesis gas is provided in the fifth synthesis gas pipe L5. The measurement value of the gas temperature sensor 99 is sent to the control device 60.

[0070] The control device 60 controls the chiller 100 based on the measurement values ​​of the water temperature sensor 97 and / or the gas temperature sensor 99, and controls the temperature of the scrubber water W3 to be, for example, 10°C or lower.

[0071] <Control Method of Gasification Furnace System 1> Next, a control method of the above-described gasification furnace system 1 will be described.

[0072] The synthesis gas produced in the gasifier 10 is introduced into the high-temperature gas cooler 20 via a first synthesis gas pipe L1. The synthesis gas produced in the gasifier 10 contains ash. The temperature of the synthesis gas flowing through the first synthesis gas pipe L1 is set to about 800°C or higher and 1200°C or lower due to the gasification reaction in the gasifier 10.

[0073] The synthesis gas introduced into the high-temperature gas cooler 20 is cooled by exchanging heat with a cooling medium (steam) in the first high-temperature heat exchange section 21 and the second high-temperature heat exchange section 22. A portion of the synthesis gas is guided via gas bypass piping L8 to the downstream side of the second high-temperature heat exchange section 22 without passing through the second high-temperature heat exchange section 22.

[0074] The synthesis gas cooled by the high-temperature gas cooler 20 is discharged from the high-temperature gas cooler 20. The synthesis gas discharged from the high-temperature gas cooler 20 is introduced into the ash removal section 30 via the second synthesis gas pipe L2. The temperature of the synthesis gas flowing through the second synthesis gas pipe L2 is set to approximately 300°C or higher and 550°C or lower by heat exchange in the high-temperature gas cooler 20.

[0075] The synthesis gas introduced into the ash removal section 30 passes through the gas filter 31. When passing through the gas filter 31, the ash contained in the synthesis gas is collected by the gas filter 31. In this way, the ash is removed while the synthesis gas is at a high temperature.

[0076] The melting point of ash is approximately 800°C or higher, and below that temperature it becomes sticky ash, and below about 600°C it becomes loose ash. Backwashing with the gas filter 31 of the ash removal unit 30 is effective for loose ash with low viscosity, so it is preferable that the gas filter 31 is always installed at a temperature below which the ash becomes easily removable by the gas filter 31, and above which tar does not precipitate. For this reason, it is preferable that the high-temperature gas cooler 20 keep the synthesis gas temperature at the outlet of the gas filter 31 at 500°C or lower.

[0077] The synthesis gas discharged from the ash removal section 30 mainly contains CO, H2, CO2, and H2O, and also contains small amounts of components derived from trace components such as S and N contained in the raw material.

[0078] The synthesis gas produced using biomass raw materials contains gaseous tar, and when the gas temperature drops below approximately 450°C, the components that make up the tar will precipitate in order as they reach their respective freezing points.

[0079] Tar is derived mainly from aromatic organic components contained in biomass raw materials. The five types shown in Table 1 are representative, but actual tar varies greatly due to bonds between C and H, etc. Tars with similar compositions have similar boiling points, so it is preferable to set and manage the boiling point range as shown below.

[0080]

[0081] The lower the boiling point of a tar, the greater its content in synthesis gas, and in the above table, the order is (1) > (2) > (3) > (4) > (5). These precipitate as liquid or solid matter as synthesis gas is cooled, and most of them are (1) to (3).

[0082] The vapor pressure of tars tends to be the same as that of their boiling points. The lower the boiling point, the higher the vapor pressure. For example, the theoretical maximum tar content that can be contained in synthesis gas at 30°C is approximately 1 g / Nm3 for tar (1) and several mg / Nm3 for tar (2).

[0083] The synthesis gas from which ash has been removed in the ash removal unit 30 is discharged from the ash removal unit 30. The synthesis gas discharged from the ash removal unit 30 is introduced into the low-temperature gas cooler 40 via the third synthesis gas pipe L3. The temperature of the synthesis gas flowing through the third synthesis gas pipe L3 is set to about 300°C or higher and 550°C or lower (preferably a maximum of 500°C).

[0084] The synthesis gas introduced into the low-temperature gas cooler 40 is cooled by heat exchange with a cooling medium (water or steam) in the first low-temperature heat exchange section 41 and the second low-temperature heat exchange section 42. At this time, some tar adheres to the heat transfer tubes of the first low-temperature heat exchange section 41 and the second low-temperature heat exchange section 42 and is removed from the synthesis gas.

[0085] In the low-temperature gas cooler 40, the synthesis gas is cooled to a relatively high temperature of around 300°C if the synthesis gas contains a large amount of the tar components (3), (4), and (5) above, or to a temperature of 200°C to 250°C if the synthesis gas contains a small amount of these tar components. This is because tar components with high boiling points become more viscous as the temperature decreases, making them more difficult to remove with a soot blower. As a result, the tar is roughly removed in the low-temperature gas cooler 40.

[0086] The synthesis gas cooled by the low-temperature gas cooler 40 is discharged from the low-temperature gas cooler 40. The synthesis gas discharged from the low-temperature gas cooler 40 is introduced into the high-temperature scrubber 70 of the scrubber 50 via the fourth synthesis gas pipe L4.

[0087] In the high-temperature scrubber 70, the control device 60 controls the temperature of the scrubber water W1 to be approximately 80°C or higher and 95°C. Specifically, the flow rate of the cooling water pump 74 is controlled using the measurement results of the water temperature sensor 77 and / or the gas temperature sensor 79. This is to keep the tar recovered in the high-temperature scrubber 70 almost liquid (with a portion solid), making it easier to separate the tar from the wastewater using centrifugation, a decanter, or the like. The separated tar can be used as a heat source, fertilizer, or the like, and separating the tar can reduce the load on wastewater treatment.

[0088] In the high-temperature scrubber 70, all of the tars (3), (4), and (5) above (although the absolute amount is small) and most of the tars (1) and (2) above are collected. In the scrubber water W1, the tars (3), (4), and (5) are mostly solid but present in small amounts, while the tars (1) and (2) are present in large amounts in liquid form. In contrast, if the temperature of the scrubber water W1 is not maintained high as in this embodiment, the tars (1) and (2) mainly solidify in the high-temperature scrubber 70 and the drainage pipe, causing blockages.

[0089] Tars (1) and (2) maintain their fluidity in the scrubber water W1, which is heated to a temperature of approximately 80°C to 95°C. Tars (3), (4), and (5) are small relative to the water volume and are therefore discharged to the wastewater without solidification. The synthesis gas discharged from the high-temperature scrubber 70 contains tar equivalent to the saturated vapor pressure at the gas temperature. Tars (3), (4), and (5) are almost completely removed from the synthesis gas, leaving tar (1) at a maximum of approximately 500 to 1,000 mg / Nm3 and tar (2) at a maximum of approximately several tens of mg / Nm3. The synthesis gas then heads to the intermediate-temperature scrubber 80. At this time, the synthesis gas contains not only H2 and CO, but also H2O (steam) and CO2. When H2O reaches steam temperature at atmospheric pressure, it becomes water and migrates to the scrubber water W1 in the high-temperature scrubber 70. This increases the volume of the scrubber water W1 and decreases the volume of the synthesis gas.

[0090] The synthesis gas discharged from the high-temperature scrubber 70 is introduced into the medium-temperature scrubber 80 via the high-temperature scrubber synthesis gas pipe L41.

[0091] In the medium-temperature scrubber 80, the synthesis gas containing the tars (1) and (2) in an amount corresponding to the saturated vapor pressure that has passed through the high-temperature scrubber 70 is subjected to secondary scrubbing. The temperature of the scrubber water W2 in the medium-temperature scrubber 80 is set to about atmospheric temperature (for example, about 20°C or higher and 40°C or lower).

[0092] Tars (1) and (2) are removed from the synthesis gas and collected in scrubber water W2. The synthesis gas at the outlet of the intermediate-temperature scrubber 80 contains tars equivalent to the saturated vapor pressure at the gas temperature at maximum. Tar (1) is less than several hundred mg / Nm3, and tar (2) is less than several mg / Nm3. Tars (1) and (2) in scrubber water W2 have high viscosity in water at room temperature, but because the amount is small compared to the amount of water, they can be discharged relatively easily without adhesion or blockage.

[0093] Since the H2O (vapor) in the gas can be liquefied and removed in the high-temperature scrubber 70, the amount of synthesis gas introduced into the medium-temperature scrubber 80 is reduced, thereby reducing the amount of cooling water used in the medium-temperature scrubber 80.

[0094] The medium-temperature scrubber 80 controls the flow rate of the cooling water pump 84 using the measurement results of the water temperature sensor 87 and / or the gas temperature sensor 89 to maintain the temperature of the scrubber water W2 preferably at room temperature +5°C or lower. This aims to recover as much tar as possible in the medium-temperature scrubber 80, efficiently minimize the downstream outflow of tar equivalent to the saturated vapor pressure corresponding to the temperature of the exhaust gas system, and reduce the power required for the chiller 100 of the low-temperature scrubber 90. When the wastewater temperature measured by the water temperature sensor 87 or the exhaust gas temperature measured by the gas temperature sensor 89 reaches a specified value or higher (room temperature +5°C), the control device 60 increases the amount of cooling water to lower the temperature of the scrubber water W2. When the temperature drops below the specified value (e.g., room temperature to room temperature +2°C), the control device 60 reduces the amount of cooling water consumed, raising the temperature of the scrubber water W2 and reducing running costs. However, since tar in this temperature range becomes solid in the scrubber water W2, it is preferable to set a lower limit value for the amount of cooling water to prevent solidification.

[0095] The synthesis gas discharged from the intermediate-temperature scrubber 80 is introduced into the low-temperature scrubber 90 via the intermediate-temperature scrubber synthesis gas pipe L42.

[0096] The low-temperature scrubber 90 performs final scrubbing of the synthesis gas containing tar (1) at a saturated vapor pressure level that has passed through the intermediate-temperature scrubber 80. The control device 60 controls the chiller 100 using the measurement results of the water temperature sensor 97 and / or the gas temperature sensor 99 to adjust the temperature of the scrubber water W3 to 10°C or less. This reduces the saturated vapor pressure of the tar as much as possible, minimizing the amount of tar flowing out of the exhaust gas system. For example, the amount of tar (1) contained in the synthesis gas at the outlet of the low-temperature scrubber 90 is reduced to several tens of mg / Nm3 or less, completing tar removal from the synthesis gas. Because the synthesis gas is cooled to approximately room temperature in the intermediate-temperature scrubber 80, the temperature difference between the intermediate-temperature scrubber 80 and the low-temperature scrubber 90 is reduced, allowing for reduced power consumption of the chiller 100.

[0097] The synthesis gas from which tar has been removed in the low-temperature scrubber 90 is supplied to various destinations via a fifth synthesis gas pipe L5.

[0098] Table 2 summarizes the outlet temperatures and tar component amounts at the low-temperature gas cooler 40, high-temperature scrubber 70, medium-temperature scrubber 80 and low-temperature scrubber 90 described above.

[0099]

[0100] The effects of the present embodiment described above are as follows: The temperature of the scrubber water W1 stored in the high-temperature scrubber 70 is controlled to be equal to or higher than 80°C and lower than the boiling point (preferably equal to or lower than 95°C), which prevents the tar removed from the synthesis gas from becoming highly viscous due to being cooled by the scrubber water W1, thereby reducing the frequency of cleaning the drainage system. This makes it easier to treat the scrubber water W1, enabling the gasifier system 1 to operate continuously for long periods of time.

[0101] By controlling the temperature of the scrubber water W2 in the medium-temperature scrubber 80 to be equal to or higher than 20°C and equal to or lower than 40°C, it is possible to remove low-boiling-point tar contained in the synthesis gas discharged from the high-temperature scrubber 70. Low-boiling-point tar becomes viscous in the scrubber water W2 at a temperature of 20°C or higher and 40°C or lower, but the amount of tar is small because most of the tar has been removed in the high-temperature scrubber 70. This makes it easier to treat the scrubber water W2 in the medium-temperature scrubber 80, and enables continuous operation of the gasification furnace system 1 over long periods of time.

[0102] By controlling the temperature of the scrubber water W3 in the low-temperature scrubber 90 to 10°C or less, low-boiling-point tar contained in the synthesis gas discharged from the medium-temperature scrubber 80 can be further removed.

[0103] The synthesis gas is cooled to a temperature of 200° C. or higher and 350° C. or lower by the low-temperature gas cooler 40. This makes it possible to remove high-boiling-point tar from the synthesis gas that is guided to the high-temperature scrubber 70.

[0104] By providing the ash removal unit 30 upstream of the low-temperature gas cooler 40, the ash is removed before the synthesis gas is cooled by the low-temperature gas cooler 40. This prevents the tar, which has become highly viscous as a result of the synthesis gas being cooled in the low-temperature gas cooler 40, from mixing with the ash, thereby preventing the ash from adhering to and accumulating on downstream equipment.

[0105] The gasification furnace system and the control method for the gasification furnace system described in each of the above-described embodiments can be understood, for example, as follows.

[0106] A gasification furnace system (1) according to a first aspect of the present disclosure includes a gasification furnace (10) that produces synthesis gas from biomass feedstock, a first scrubber (70) to which the synthesis gas produced in the gasification furnace (10) is introduced, a second scrubber (80) to which the synthesis gas discharged from the first scrubber (70) is introduced, and a control device (60) that controls the temperature of scrubber water (W1) stored in the first scrubber (70) to be 80°C or higher and lower than the boiling point.

[0107] The temperature of the scrubber water stored in the first scrubber is controlled to be at least 80°C and below the boiling point (preferably at most 95°C). This prevents the tar removed from the synthesis gas from being cooled by the scrubber water and becoming highly viscous, thereby reducing the frequency of cleaning the drainage system. This facilitates treatment of the scrubber water and enables long-term continuous operation of the gasifier system. The control device may control the temperature of the scrubber water by detecting the temperature of the scrubber water in the first scrubber, or may control the temperature of the scrubber water by detecting the temperature of the synthesis gas discharged from the first scrubber. The temperature control by the control device is performed, for example, by adjusting the flow rate of room-temperature water injected by the first scrubber.

[0108] In the gasification furnace system (1) according to the second aspect of the present disclosure, in the first aspect, the control device (60) controls the temperature of the scrubber water (W2) stored in the second scrubber (80) to be not less than 20°C and not more than 40°C.

[0109] By controlling the temperature of the scrubber water in the second scrubber to between 20°C and 40°C, low-boiling-point tar contained in the synthesis gas discharged from the first scrubber can be removed. Low-boiling-point tar becomes viscous in scrubber water at between 20°C and 40°C, but the amount of tar is small because most of the tar has been removed in the first scrubber. This makes it easier to treat the scrubber water, enabling long-term continuous operation of the gasifier system. The control device may control the temperature of the scrubber water by detecting the temperature of the scrubber water in the second scrubber, or may control the temperature of the scrubber water by detecting the temperature of the synthesis gas discharged from the second scrubber. Temperature control by the control device is performed, for example, by adjusting the flow rate of room-temperature water injected in the second scrubber.

[0110] The gasification furnace system (1) according to a third aspect of the present disclosure is the first or second aspect, and includes a third scrubber (90) to which the synthesis gas discharged from the second scrubber (80) is introduced, and the control device (60) controls the temperature of the scrubber water (W3) stored in the third scrubber (90) to be 10°C or less.

[0111] By controlling the temperature of the scrubber water in the third scrubber to 10°C or less, low-boiling-point tar contained in the synthesis gas discharged from the second scrubber can be further removed. The control device may control the temperature of the scrubber water by detecting the temperature of the scrubber water in the third scrubber, or may control the temperature of the scrubber water by detecting the temperature of the synthesis gas discharged from the third scrubber. Temperature control by the control device is performed, for example, by controlling a chiller that cools the room-temperature water injected by the third scrubber.

[0112] A gasification furnace system (1) according to a fourth aspect of the present disclosure is any one of the first to third aspects, and further includes a gas cooler (40) that is provided upstream of the synthesis gas flow of the first scrubber (70) and cools the temperature of the synthesis gas to 200°C or more and 350°C or less.

[0113] The synthesis gas is cooled to 200°C or higher and 350°C or lower by the gas cooler. This makes it possible to remove high-boiling-point tar from the synthesis gas introduced into the first scrubber. The gas cooler preferably includes a heat transfer tube through which a cooling medium such as water or steam flows, and a soot blower that removes tar adhering to the heat transfer tube.

[0114] The gasification furnace system (1) according to a fifth aspect of the present disclosure is the fourth aspect described above, and is provided with an ash removal section (30) that is provided upstream of the synthesis gas flow of the gas cooler (40) and removes ash contained in the synthesis gas.

[0115] By providing an ash removal section upstream of the gas cooler, the ash is removed before the gas cooler cools it. This prevents the tar, which becomes highly viscous when the synthesis gas is cooled downstream of the gas cooler, from mixing with the ash, thereby preventing the ash from adhering to and accumulating on downstream equipment.

[0116] A control method for a gasification furnace system (1) according to a first aspect of the present disclosure is a control method for a gasification furnace system (1) including a gasification furnace (10) that produces synthesis gas from biomass feedstock, a first scrubber (70) to which the synthesis gas produced in the gasification furnace (10) is introduced, and a second scrubber (80) to which the synthesis gas discharged from the first scrubber (70) is introduced, and the control method controls the temperature of scrubber water (W3) stored in the first scrubber (70) to be equal to or higher than 80°C and lower than the boiling point.

[0117] REFERENCE SIGNS LIST 1: Gasification furnace system 10: Gasification furnace 11: Gas thermometer 20: High-temperature gas cooler 21: First high-temperature heat exchange section 22: Second high-temperature heat exchange section 23: Cooling medium thermometer 24: Cooling medium pressure gauge 25: Cooling medium flow meter 26: Gas thermometer 27: Flow rate control damper 28: First on-off valve 30: Ash removal section 31: Gas filter 32: Housing 33: Backwash valve 34: Discharge valve 35: Second on-off valve 40: Low-temperature gas cooler (gas cooler) 41: First low-temperature heat exchange section 42: Second low-temperature heat exchange section 43: Steam drum 44: Feedwater pump 45: Level gauge 50: Scrubber 51: Gas flow meter 52: Gas analyzer 60: Control device 70 : High temperature scrubber (first scrubber) 71 : Container 72 : Injection unit 73 : Cooling water supply piping 74 : Cooling water pump 75 : Cooling water tank 76 : Drain pipe 77 : Water temperature sensor 79 : Gas temperature sensor 80 : Medium temperature scrubber (second scrubber) 81 : Container 82 : Injection unit 83 : Cooling water supply piping 84 : Cooling water pump 85 : Cooling water tank 86 : Drain pipe 87 : Water temperature sensor 89 : Gas temperature sensor 90 : Low temperature scrubber (third scrubber) 91 : Container 92 : Injection unit 93 : Cooling water supply piping 94 : Cooling water pump 95 : Cooling water tank 96 : Drain pipe 97 : Water temperature sensor 99 : Gas temperature sensor 100 : Chiller L1 : First synthesis gas pipe L11 : First cooling medium pipe L12 : Second cooling medium pipe L13 : Third cooling medium pipe L14 : Fourth cooling medium pipe L15 : Fifth cooling medium pipe L2 : Second synthesis gas pipe L20 : Spray water pipe L21 : Spray medium line L22 : Spray medium line L23 : First tar pipe L25 : Backwash pipe L26 : Discharge pipe L3 : Third synthesis gas pipe L4 : Fourth synthesis gas pipe L41 : High temperature scrubber synthesis gas pipe L42 : Medium temperature scrubber synthesis gas pipe L5 : Fifth synthesis gas pipeL8: Gas bypass piping W1: Scrubber water W2: Scrubber water W3: Scrubber water

Claims

1. A gasification furnace system comprising: a gasification furnace that produces synthesis gas from biomass feedstock; a first scrubber to which the synthesis gas produced in the gasification furnace is guided; a second scrubber to which the synthesis gas discharged from the first scrubber is guided; and a control device that controls the temperature of scrubber water stored in the first scrubber so that it is at least 80°C and below the boiling point.

2. A gasification furnace system as described in claim 1, wherein the control device controls the temperature of the scrubber water stored in the second scrubber to be between 20°C and 40°C.

3. A gasification furnace system as described in claim 2, further comprising a third scrubber to which the synthesis gas discharged from the second scrubber is guided, and the control device controls the temperature of the scrubber water stored in the third scrubber to be 10°C or lower.

4. A gasification furnace system as described in claim 3, further comprising a gas cooler provided upstream of the synthesis gas flow from the first scrubber for cooling the temperature of the synthesis gas to 200°C or higher and 350°C or lower.

5. A gasification furnace system according to claim 4, further comprising an ash removal section provided upstream of the synthesis gas flow from the gas cooler for removing ash contained in the synthesis gas.

6. A control method for a gasification furnace system comprising: a gasification furnace that produces synthesis gas from biomass feedstock; a first scrubber to which the synthesis gas produced in the gasification furnace is guided; and a second scrubber to which the synthesis gas discharged from the first scrubber is guided, the control method for a gasification furnace system controlling the temperature of scrubber water stored in the first scrubber to be at least 80°C and below the boiling point.

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