Cleaning method and cleaning apparatus in biomass gasification power generation system

Abstract

To provide a technology that achieves an excellent cleaning effect against tar deposited during operation of a biomass gasification power generation system and enables reduction in cleaning time or cleaning frequency.SOLUTION: This method comprises a step of stopping the inflow of biomass gas into a tar separation device 2, a step of supplying a cleaning liquid into a tar flow path in the tar separation device 2, and a step of recovering the cleaning liquid containing tar after passing through the tar flow path.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a cleaning method and a cleaning device for a biomass gasification power generation system. [Background technology]

[0002] A biomass gasification power generation system uses a gasifier to generate biomass gas from biomass (e.g., wood chips) as fuel, and supplies this gas to a gas engine generator to generate power (see, for example, Patent Document 1 below). Because biomass gas contains impurities such as tar, these impurities are removed and refined using a gas cooler and an electrostatic precipitator, and the refined gas is then supplied to the gas engine generator.

[0003] However, the tar contained in biomass gas is highly viscous, so it adheres to the pipes and equipment (such as gas coolers and electrostatic precipitators) through which the gas passes. For this reason, in order to continue to generate electricity properly, it is necessary to periodically clean and remove the tar that has adhered to the pipes and equipment.

[0004] However, during cleaning, purified gas cannot be supplied to the gas engine generator, so power generation must be stopped. If power generation is stopped for a long time, there is a problem that business income (revenue from selling electricity) of the power generation system will decrease.

[0005] Patent Document 2 below proposes preventing adhesion of deposits by introducing a purge gas into an electrostatic precipitator, but this is not intended to remove tar once it has adhered, and therefore a high removal effect cannot be expected. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 2022-67699 [Patent Document 2] Japanese Patent Application Laid-Open No. 2009-1602 Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention has been made in view of the above-mentioned circumstances, and a main object of the present invention is to provide a technology that can achieve a high cleaning effect against adhered tar and can shorten the cleaning time or reduce the cleaning frequency. [Means for solving the problem]

[0008] The present invention can be expressed as the inventions described in the following items.

[0009] (Item 1) A cleaning method for a biomass gasification power generation system that has a gasification furnace that generates biomass gas from biomass and a tar separation device that separates and purifies tar contained in the biomass gas, and generates power using the purified biomass gas, comprising: stopping the flow of the biomass gas into the tar separation device; supplying a cleaning liquid into the tar flow path in the tar separation device; recovering the cleaning liquid containing the tar by passing it through the tar flow path; A cleaning method for a biomass gasification power generation system, comprising:

[0010] (Item 2) The flow path of the biomass gas is switched while the gasification furnace continues to operate, thereby stopping the inflow of the biomass gas into the tar separation device. Item 1. A cleaning method for a biomass gasification power generation system.

[0011] (Item 3) The cleaning solution is heated to 40°C or higher. 3. A cleaning method for a biomass gasification power generation system according to item 1 or 2.

[0012] (Item 4) The cleaning solution used is an aqueous solution of caustic soda. 3. A cleaning method for a biomass gasification power generation system according to item 1 or 2.

[0013] (Item 5) The method further includes a step of circulating the recovered cleaning liquid and supplying the cleaning liquid again into the tar flow path. 3. A cleaning method for a biomass gasification power generation system according to item 1 or 2.

[0014] (Item 6) the tar separation device includes a gas cooler having a flow path for the biomass gas and a flow path for a cooling liquid that cools the biomass gas, The method further includes a step of flowing hot water of 50°C or higher through the coolant flow path instead of the continuous coolant, thereby heating the cleaning liquid with the hot water and enhancing the cleaning effect. 3. A cleaning method for a biomass gasification power generation system according to item 1 or 2.

[0015] (Item 7) A cleaning device in a biomass gasification power generation system that has a gasification furnace that generates biomass gas from biomass and a tar separation device that separates and purifies tar contained in the biomass gas, and generates power using the purified biomass gas, the gasification furnace is configured to be able to stop the inflow of the biomass gas into the tar separation device, a cleaning liquid supply device for supplying a cleaning liquid into the tar flow path in the tar separation device; a cleaning liquid recovery device that recovers the cleaning liquid supplied into the tar flow path. Cleaning equipment for biomass gasification power generation systems. [Effects of the Invention]

[0016] According to the technology of the present invention, a high cleaning effect against adhering tar can be achieved, which makes it possible to shorten the cleaning time or reduce the cleaning frequency. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is an explanatory diagram showing a schematic configuration of a biomass gasification power generation system incorporating a cleaning device according to one embodiment of the present invention. [Figure 2] 2 is a flowchart for explaining the operation during normal operation in the biomass gasification power generation system of FIG. 1. [Figure 3] 2 is a flow chart for explaining the operation during cleaning in the biomass gasification power generation system of FIG. 1. DETAILED DESCRIPTION OF THE INVENTION

[0018] A biomass gasification power generation system incorporating a cleaning device according to one embodiment of the present invention will be described below with reference to the accompanying drawings. Note that Fig. 1 is a schematic explanatory diagram, and the dimensional ratio and scale are not accurate.

[0019] (Configuration of biomass gasification power generation system) The biomass gasification power generation system (hereinafter sometimes simply referred to as the "power generation system" or "system") of this embodiment has a gasification furnace 1 that produces biomass gas (hereinafter sometimes simply referred to as "gas") from biomass fuel, a tar separation device 2 that separates and refines tar contained in the biomass gas, and a washing device 3 that washes away any adhering tar. The system also has a gas engine generator 5 and an incineration facility 6. The system generates power by sending the refined biomass gas to the gas engine generator 5.

[0020] (Gasification furnace) The gasifier 1 generates biomass gas by heating biomass fuel (e.g., wood chips, or other raw materials capable of generating biomass gas) to high temperatures under low-oxygen conditions during operation. The generated biomass gas is sent from the gasifier 1 to the tar separation device 2.

[0021] Furthermore, the gasification furnace 1 of this embodiment is configured to be able to send biomass gas to the incineration facility 6 by switching the flow path of the biomass gas. The flow path can be switched, for example, by opening and closing an appropriate valve. This makes it possible to stop the inflow of biomass gas into the tar separation device 2 while operating the gasification furnace 1 of this embodiment.

[0022] (Tar separation device) The tar separation apparatus 2 includes a first gas cooler 21, a second gas cooler 22, an electrostatic precipitator 23, a first cooling water passage 24, and a second cooling water passage 25. Furthermore, the tar separation apparatus 2 of this embodiment includes a separation tank 26, a flash tank 27, and an evaporator 28.

[0023] The first gas cooler 21 has a cooling water flow path through which the cooling water sent from the first cooling water path 24 passes, and a tar flow path through which the biomass gas and the tar contained therein sent from the gasifier 1 pass. The cooling water flow path and the tar flow path are separate but adjacent to each other, allowing heat exchange between the cooling water and the biomass gas to cool the gas. Tar mixed water (water containing tar) produced as the gas is cooled is sent to a separation tank 26.

[0024] The second gas cooler 22 has a cooling water flow path through which the cooling water sent from the second cooling water path 25 passes, and a tar flow path through which the biomass gas and the tar contained therein sent from the first gas cooler 21 pass. As with the first gas cooler 21, the cooling water flow path and the tar flow path are separate but adjacent to each other, allowing heat exchange between the cooling water and the biomass gas to cool the gas. As with the first gas cooler 21, the tar mixed water produced as the gas is cooled is sent to a separation tank 26.

[0025] The electrostatic precipitator 23 receives the biomass gas sent from the second gas cooler 22, purifies the gas by electrically collecting dust, and sends the purified gas to the gas engine generator 5. The tar-mixed water produced by the electrostatic precipitator 23 is also sent to the separation tank 26.

[0026] The first cooling water path 24 has a cooling tower 241 that cools the cooling water returned from the first gas cooler 21, a cooling water tank 242 that temporarily stores the cooling water, and cooling water pumps 243 and 244 that send the cooling water downstream. With this configuration, the first cooling water path 24 is capable of sending the cooling water to the cooling water flow path of the first gas cooler 21 and circulating it.

[0027] The second cooling water path 25 has a chiller 251 that cools the cooling water returned from the second gas cooler 22, and a cooling water pump 252 that sends the cooling water downstream. With this configuration, the second cooling water path 25 is capable of sending the cooling water to the cooling water flow path of the second gas cooler 22 and circulating it.

[0028] The separation tank 26 is used to temporarily store the tar-mixed water from the first gas cooler 21, the second gas cooler 22, and the electrostatic precipitator 23 and separate the tar content. The tar separated in the separation tank 26 is sent to the incineration facility 6.

[0029] The flash tank 27 accumulates the tar-mixed water remaining after tar has been separated in the separation tank 26. The gas in the flash tank 27 is sent to the incineration facility 6. The tar-mixed water in the flash tank 27 is also sent to the incineration facility 6 eventually.

[0030] The evaporator 28 heats the tar-mixed water accumulated in the flash tank 27 with thermal oil heated by the thermal oil boiler 281, thereby evaporating the water content of the tar-mixed water.

[0031] (Cleaning equipment) The cleaning device 3 includes a cleaning liquid supply device 31 , a cooling water heating device 32 , and a side tank 33 .

[0032] The cleaning liquid supply device 31 supplies cleaning liquid into the tar flow path (i.e., the gas flow path) in the tar separation device 2. The cleaning liquid supply device 31 includes a chemical liquid tank 311, a cleaning liquid tank 312, a chemical liquid pump 313, a cleaning liquid pump 314, and a hot water supply device 315.

[0033] The chemical tank 311 is a tank for storing the cleaning liquid before dilution. In this embodiment, an aqueous solution of caustic soda (NaOH) is used as the cleaning liquid.

[0034] The cleaning liquid tank 312 is a tank that stores the cleaning liquid sent from the chemical liquid tank 311 by the chemical liquid pump 313. The cleaning liquid tank 312 is also supplied with hot water from a hot water supply device 315. Therefore, the cleaning liquid tank 312 can store cleaning liquid diluted to a predetermined concentration. In this embodiment, the temperature of the hot water sent from the hot water supply device 315 is set to, for example, 40°C or higher, preferably 50°C or higher. This allows the concentration of the cleaning liquid in the cleaning liquid tank to be around 40°C or higher. The cleaning liquid pump 314 can send the diluted cleaning liquid in the cleaning liquid tank 312 to the tar flow paths (i.e., gas flow paths) of the first gas cooler 21, the second gas cooler 22, and the electrostatic precipitator 23 via appropriate piping. Furthermore, in this embodiment, the cleaning liquid pump 314 can send the cleaning liquid in the cleaning liquid tank 312 to the flash tank 27 by switching the piping route.

[0035] The coolant heating device 32 has a first heat exchanger 321 and a second heat exchanger 322. The first heat exchanger 321 is configured to heat the coolant flowing through the first coolant path 24. Specifically, the coolant can be heated by switching the path of the first coolant path 24 and sending the coolant to the first heat exchanger 321. The second heat exchanger 322 is configured to heat the coolant flowing through the second coolant path 25. Specifically, as in the case of the first heat exchanger 321, the coolant can be heated by switching the path of the second coolant path 25 and sending the coolant to the second heat exchanger 322. As a heat source for the first heat exchanger 321 and the second heat exchanger 322, for example, hot water generated within the system can be used.

[0036] The reside tank 33 temporarily stores the washing water used in the washing in the flash tank 27, and can be burned in the incineration facility 6 as needed.

[0037] The gas engine generator 5 is configured to generate electricity using the refined biomass gas sent from the electrostatic precipitator 23. The gas engine generator 5 can be configured in the same way as a conventional one, so a detailed description thereof will be omitted.

[0038] The incineration facility 6 incinerates gas and tar components. In the incineration facility 6 of this embodiment, the heat generated by incineration can be used to obtain hot water for use in the system.

[0039] The reside tank 33, the flash tank 27, and the evaporator 28 in this embodiment correspond to a specific example of a cleaning liquid recovery device that recovers the cleaning liquid supplied into the tar flow path.

[0040] The power generation system of this embodiment will be described in more detail below as the operation of the power generation system.

[0041] (Power generation system operation) Next, the operation of the above-described power generation system will be described with further reference to FIGS.

[0042] (During normal operation) During normal operation, biomass gas can be generated using biomass as fuel as the gasifier 1 operates (step SA-1 in FIG. 2). The generated gas is sent to a tar flow path (i.e., a gas flow path) in the first gas cooler 21. The gas in the tar flow path is cooled by cooling water sent to the cooling water flow path of the first gas cooler 21 by the first cooling water path 24 (step SA-2 in FIG. 2). As a result, a portion of the tar is separated from the gas and sent to the separation tank 26 as tar-mixed water. The gas that has passed through the first gas cooler 21 is sent to the second gas cooler 22 and cooled by the second cooling water path 25 in the same manner as in the first gas cooler 21. As a result, a portion of the tar is further recovered and sent to the separation tank 26 as tar-mixed water.

[0043] The gas that has passed through the second gas cooler 22 is sent to an electrostatic precipitator 23, where the tar is also separated and sent as tar-mixed water to a separation tank 26. The gas refined by the above steps is sent from the electrostatic precipitator 23 to a gas engine generator 5, which can thereby generate electricity (step SA-3 in FIG. 2).

[0044] In the separation tank 26, the viscous tar component is separated from the tar mixed water, and this tar component can be sent to the incineration facility 6 for incineration. The remaining tar mixed water is sent to the flash tank 27. The tar mixed water sent to the flash tank 27 is heated in the evaporator 28, and the resulting steam is sent to the incineration facility 6. The tar mixed water, which has been concentrated as a result of heating, is finally sent to the incineration facility 6.

[0045] The normal operation described above is basically the same as that of a conventional power generation system, so a more detailed explanation will be omitted.

[0046] (When cleaning) During cleaning, first, the inflow of biomass gas into the tar separation device 2 is stopped (step SB-1 in FIG. 3). In this embodiment, while continuing to operate the gasification furnace 1, the inflow of biomass gas into the tar separation device 2 can be stopped by switching the flow path of the biomass gas and sending this gas to the incineration facility 6. This flow path switching can be performed by opening and closing a valve as appropriate. In the incineration facility 6, the gas is incinerated, and heat to be used in the system of this embodiment can be obtained, for example, as hot water.

[0047] Next, a cleaning liquid is supplied into the tar flow path in the tar separation device 2 (step SB-2 in FIG. 3). Specifically, the cleaning liquid in the cleaning liquid tank 312 is supplied by the cleaning liquid pump 314 to the tar flow paths (i.e., gas flow paths) of the first gas cooler 21, the second gas cooler 22, and the electrostatic precipitator 23. As a result, the cleaning liquid passes through the tar flow paths of the first gas cooler 21, the second gas cooler 22, and the electrostatic precipitator 23 almost simultaneously (i.e., in parallel). According to this embodiment, the cleaning liquid sent into the tar flow path can exert a high cleaning effect on the adhering tar. Therefore, it is possible to shorten the cleaning time or reduce the cleaning frequency.

[0048] In this embodiment, hot water heated to 40°C or higher is used as the cleaning liquid supplied from the hot water supply device 315. By using hot water in this manner, the cleaning efficiency of the cleaning liquid against tar can be improved. Furthermore, in this embodiment, an aqueous solution of caustic soda is used as the cleaning liquid. This makes it easier to dissolve the adhering tar, further improving the cleaning efficiency.

[0049] The washing liquid supplied to the tar separation device 2 is recovered in the washing liquid tank 312. In this embodiment, the recovered washing liquid is circulated by a washing liquid pump and supplied again to the tar flow path. In this embodiment, heated washing water can be circulated and reused, which has the advantage of reducing the energy required to heat the washing water and improving energy efficiency.

[0050] Furthermore, in this embodiment, the cooling water used in the first gas cooler 21 is heated by the first heat exchanger 321. Similarly, the cooling water used in the second gas cooler 22 is heated by the second heat exchanger 322. This allows the cooling water to be heated to, for example, 50°C or higher. This warm water can then be flowed through each cooling liquid flow path. As a result, in this embodiment, the cleaning liquid sent to the first gas cooler 21 and the second gas cooler 22 is heated by heat exchange with the warm water, thereby further improving the cleaning efficiency. Here, in the first cooling water path 24, the cooling water path is switched during cleaning so that the cooling water is not sent to the cooling tower 241 and the cooling water tank 242 but is sent to the piping 323 (i.e., bypassed), thereby preventing a drop in the temperature of the cooling water.

[0051] When the tar concentration in the cleaning liquid increases due to the circulation of the cleaning liquid sent to the tar separation device 2, the flow path of the cleaning liquid is switched so that the cleaning liquid is sent to the flash tank 27 instead of the first gas cooler 21, the second gas cooler 22, and the electrostatic precipitator 23. The tar concentration may be determined automatically by an instrument or by the judgment of an operator. This allows the cleaning liquid containing tar to be recovered by passing through the tar flow path (step SB-3 in Figure 3).

[0052] The cleaning liquid sent to the flash tank 27 is heated by the evaporator 28, and the resulting gas is sent to the incineration facility 6 and incinerated. The cleaning liquid, whose tar concentration has increased due to heating, is finally sent to the incineration facility 6 and incinerated. As described above, this embodiment has the advantage that the recovered cleaning liquid is not disposed of as industrial waste, but is instead incinerated within the system to convert it into thermal energy and can be reused.

[0053] In this embodiment, the reside tank 33 is provided, so that the washing water used in the washing can be stored and burned in the incineration facility 6 as needed.

[0054] The cleaning liquid sent to the flash tank 27 etc. also functions to clean the flash tank 27 etc. and the inside of the piping along the way.

[0055] Furthermore, in this embodiment, by stopping the inflow of biomass gas into the tar separation device 2, the tar separation device 2 can be cleaned without stopping the operation of the gasification furnace 1. If the gasification furnace 1 is stopped once, a large amount of energy is lost when it is restarted. In this embodiment, there is no need to stop the operation of the gasification furnace 1 during cleaning, so the energy efficiency of the entire system can be improved. Moreover, since the biomass gas is sent to the incineration facility 6 during cleaning, the hot water obtained by the incineration process of the biomass gas can also be used for cleaning.

[0056] Once cleaning is complete, the system is returned to the normal operating state described above and normal operation is carried out.

[0057] The above-described embodiment is merely an example and does not represent essential components of the present invention. The configuration of each part is not limited to the above, as long as the gist of the present invention can be achieved. [Explanation of symbols]

[0058] 1 Gasifier 2. Tar separation equipment 23 Electrostatic Precipitator 24 First cooling water path 241 Cooling Tower 242 Cooling water tank 243·244 Cooling water pump for first cooling water path 25 Second cooling water path 251 Chiller 252 Cooling water pump for second cooling water path 26 Separation Tank 27 Flush tank (cleaning liquid recovery device) 28 Evaporator (cleaning liquid recovery device) 281 Thermal Oil Boiler 3 Cleaning equipment 31 Cleaning liquid supply device 311 Chemical tank 312 Cleaning solution tank 313 Chemical Pump 314 Cleaning liquid pump 315 Hot water supply equipment 32 Cooling water heating device 321 1st heat exchanger 322 Second heat exchanger 323 Piping 33 Reside tank (cleaning liquid recovery device) 5. Gas engine generator 6 Incineration facility

Claims

1. A cleaning method for a biomass gasification power generation system that has a gasification furnace that generates biomass gas from biomass and a tar separation device that separates and purifies tar contained in the biomass gas, and generates power using the purified biomass gas, comprising: stopping the flow of the biomass gas into the tar separation device; supplying a cleaning liquid into the tar flow path in the tar separation device; recovering the cleaning liquid containing the tar by passing it through the tar flow path; A cleaning method for a biomass gasification power generation system, comprising:

2. The flow path of the biomass gas is switched while the gasification furnace continues to operate, thereby stopping the inflow of the biomass gas into the tar separation device. The cleaning method for a biomass gasification power generation system according to claim 1.

3. The cleaning solution is heated to 40°C or higher. A cleaning method for a biomass gasification power generation system according to claim 1 or 2.

4. The cleaning solution used is an aqueous solution of caustic soda. A cleaning method for a biomass gasification power generation system according to claim 1 or 2.

5. The method further includes a step of circulating the recovered cleaning liquid and supplying the cleaning liquid again into the tar flow path. A cleaning method for a biomass gasification power generation system according to claim 1 or 2.

6. the tar separation device includes a gas cooler having a flow path for the biomass gas and a flow path for a cooling liquid that cools the biomass gas, The method further includes a step of flowing hot water of 50°C or higher through the coolant flow path instead of the continuous coolant, thereby heating the cleaning liquid with the hot water and enhancing the cleaning effect. A cleaning method for a biomass gasification power generation system according to claim 1 or 2.

7. A cleaning device in a biomass gasification power generation system that has a gasification furnace that generates biomass gas from biomass and a tar separation device that separates and purifies tar contained in the biomass gas, and generates power using the purified biomass gas, the gasification furnace is configured to be able to stop the inflow of the biomass gas into the tar separation device, a cleaning liquid supply device for supplying a cleaning liquid into the tar flow path in the tar separation device; a cleaning liquid recovery device that recovers the cleaning liquid supplied into the tar flow path. Cleaning equipment for biomass gasification power generation systems.

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