Desulfurization apparatus and desulfurization method

Abstract

To provide a desulfurization apparatus capable of treating hydrogen sulfide while suppressing a decrease in methane gas concentration in biogas.SOLUTION: A desulfurization apparatus 16 biologically treats hydrogen sulfide in biogas generated by methane fermentation processing of organic wastewater or organic waste using sulfur-oxidizing bacteria, and includes: a reaction tank 20 to which the biogas is supplied; a non-porous hollow fiber membrane 22 installed in the reaction tank 20; an oxygen-containing gas supply device 24 that supplies an oxygen-containing gas to the hollow fiber membrane 22; an oxygen-containing gas exhaust pipe 26 that exhausts the oxygen-containing gas from the hollow fiber membrane 22 to the outside of the reaction tank 20; and a water spraying device 28 that sprays water onto an outer surface of the hollow fiber membrane 22. The hollow fiber membrane 22 allows oxygen in the oxygen-containing gas to permeate into the reaction tank 20 and supplies the oxygen to a biofilm including the sulfur-oxidizing bacteria formed on the outer surface of the hollow fiber membrane 22.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a desulfurization device and a desulfurization method for treating hydrogen sulfide contained in biogas. [Background technology]

[0002] Toward achieving carbon neutrality, the application of technologies for recovering energy from organic wastewater and organic waste is expanding. One of the main technologies is methane fermentation, which decomposes the organic matter in organic wastewater and organic waste to produce biogas. Biogas contains approximately 60-80% methane, approximately 20-40% carbon dioxide, and several hundred ppm to tens of thousands of ppm hydrogen sulfide.

[0003] Biogas is used as fuel gas, for example, in gas engines for power generation, gas turbines, fuel cells, and boilers for producing hot water and steam. However, if hydrogen sulfide is present in biogas, it will turn into sulfur oxides upon combustion, causing problems such as corrosion of machinery and components. Therefore, it is necessary to remove the hydrogen sulfide from the biogas.

[0004] Methods for removing hydrogen sulfide include dry desulfurization, which uses adsorbents such as iron oxide, and wet desulfurization, which absorbs hydrogen sulfide into an aqueous solution using alkali, but these methods have high running costs and also pose problems in the disposal of the absorbents and absorption solutions. Therefore, biological desulfurization using microorganisms has been proposed as a useful method.

[0005] For example, Patent Document 1 proposes a method of removing hydrogen sulfide by providing a layer supporting sulfur-oxidizing bacteria in a reaction tank, passing biogas through this layer to bring it into contact with the sulfur-oxidizing bacteria, and oxidizing the hydrogen sulfide contained in the biogas to form sulfuric acid. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-305328 Summary of the Invention [Problem to be solved by the invention]

[0007] Since oxygen is required for sulfur-oxidizing bacteria to oxidize hydrogen sulfide to sulfuric acid, an oxygen-containing gas (usually air) must be introduced into the reaction tank. To improve the activity of sulfur-oxidizing bacteria, it is desirable to introduce a sufficient amount of oxygen-containing gas into the reaction tank. However, the more oxygen-containing gas is introduced into the reaction tank, the lower the methane gas concentration in the biogas after treatment becomes. If the methane gas concentration falls below a certain level, the biogas-using equipment may stop operating.

[0008] Therefore, an object of the present disclosure is to provide a desulfurization device and a desulfurization method that can treat hydrogen sulfide while suppressing a decrease in the concentration of methane gas in biogas. [Means for solving the problem]

[0009] A desulfurization apparatus according to one aspect of the present disclosure is a desulfurization apparatus that uses sulfur-oxidizing bacteria to biologically treat hydrogen sulfide in biogas generated by methane fermentation of organic wastewater or organic waste, and includes a reaction tank to which the biogas is supplied, a non-porous oxygen-permeable membrane installed within the reaction tank, an oxygen-containing gas supply means for supplying an oxygen-containing gas to the oxygen-permeable membrane, piping for exhausting the oxygen-containing gas from the oxygen-permeable membrane to the outside of the reaction tank, and a water spray means for spraying water onto the outer surface of the oxygen-permeable membrane, wherein the oxygen-permeable membrane allows oxygen in the oxygen-containing gas to permeate into the reaction tank and supply the oxygen to a biofilm containing the sulfur-oxidizing bacteria that is formed on the outer surface of the oxygen-permeable membrane.

[0010] Furthermore, the desulfurization apparatus preferably includes an alkaline agent addition means for adding an alkaline agent to the water, and a first control device for controlling the alkaline agent addition means, and the first control device preferably controls the alkaline agent addition means so that the amount of alkaline agent added is adjusted based on the oxygen concentration in the oxygen-containing gas supplied to the oxygen-permeable membrane, the oxygen concentration in the oxygen-containing gas exhausted from the oxygen-permeable membrane to the outside of the reaction tank, and the flow rate of the oxygen-containing gas supplied to the oxygen-permeable membrane.

[0011] Furthermore, the desulfurization apparatus preferably includes a nutrient source adding means for adding a nutrient source to the water, and a second control device for controlling the nutrient source adding means, and the second control device preferably controls the nutrient source adding means so that the amount of the nutrient source added is adjusted based on the oxygen concentration in the oxygen-containing gas supplied to the oxygen-permeable membrane, the oxygen concentration in the oxygen-containing gas exhausted from the oxygen-permeable membrane to the outside of the reaction tank, and the flow rate of the oxygen-containing gas supplied to the oxygen-permeable membrane.

[0012] Furthermore, the above-mentioned desulfurization apparatus preferably includes a peeling means for peeling the biofilm from the oxygen-permeable membrane and a third control device for controlling the peeling means, and the third control device preferably activates the peeling means when a cumulative oxygen consumption calculated from the oxygen concentration in the oxygen-containing gas supplied to the oxygen-permeable membrane, the oxygen concentration in the oxygen-containing gas discharged from the oxygen-permeable membrane to the outside of the reaction tank, and the flow rate of the oxygen-containing gas supplied to the oxygen-permeable membrane exceeds a predetermined value.

[0013] Furthermore, a desulfurization method according to one aspect of the present disclosure is a desulfurization method in which hydrogen sulfide in biogas generated by methane fermentation of organic wastewater or organic waste is biologically treated by sulfur-oxidizing bacteria, and includes a biogas supply step of supplying the biogas to a reaction tank having a non-porous oxygen-permeable membrane installed therein; an oxygen-containing gas supply step of supplying an oxygen-containing gas to the oxygen-permeable membrane; and a water spray step of spraying water onto the outer surface of the oxygen-permeable membrane, wherein the oxygen-permeable membrane allows oxygen in the oxygen-containing gas to permeate into the reaction tank and supply the oxygen to a biofilm containing the sulfur-oxidizing bacteria that is formed on the outer surface of the oxygen-permeable membrane.

[0014] Furthermore, the above-described desulfurization method preferably includes an alkaline agent addition step of adding an alkaline agent to the water, and in the alkaline agent addition step, the amount of the alkaline agent added is preferably adjusted based on the oxygen concentration in the oxygen-containing gas supplied to the oxygen-permeable membrane, the oxygen concentration in the oxygen-containing gas exhausted from the oxygen-permeable membrane to the outside of the reaction vessel, and the flow rate of the oxygen-containing gas supplied to the oxygen-permeable membrane.

[0015] Furthermore, the above-described desulfurization method preferably includes a nutrient source adding step of adding a nutrient source to the water, and in the nutrient source adding step, the amount of the nutrient source added is adjusted based on the oxygen concentration in the oxygen-containing gas supplied to the oxygen-permeable membrane, the oxygen concentration in the oxygen-containing gas exhausted from the oxygen-permeable membrane to the outside of the reaction vessel, and the flow rate of the oxygen-containing gas supplied to the oxygen-permeable membrane.

[0016] Furthermore, the above-described desulfurization method preferably includes a peeling step of peeling the biofilm from the oxygen-permeable membrane, and the peeling step is performed when a cumulative oxygen consumption calculated from the oxygen concentration in the oxygen-containing gas supplied to the oxygen-permeable membrane, the oxygen concentration in the oxygen-containing gas discharged from the oxygen-permeable membrane to the outside of the reaction tank, and the flow rate of the oxygen-containing gas supplied to the oxygen-permeable membrane exceeds a predetermined value. [Effects of the Invention]

[0017] According to the present disclosure, it is possible to provide a desulfurization device and a desulfurization method that can treat hydrogen sulfide while suppressing a decrease in the concentration of methane gas in biogas. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a schematic diagram illustrating an example of a treatment system including a desulfurization device according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0019] The following describes an embodiment of the present disclosure. The embodiment is an example of implementing the present disclosure, and the present disclosure is not limited to the embodiment.

[0020] FIG. 1 is a schematic diagram showing an example of a treatment system including a desulfurization apparatus according to this embodiment. The treatment system 1 shown in FIG. 1 includes a raw water tank 10, a methane fermentation tank 12, an aerobic treatment tank 14, a desulfurization apparatus 16, and a dry desulfurization tower 18. The desulfurization apparatus 16 includes a reaction tank 20, a non-porous hollow fiber membrane 22 installed in the reaction tank 20, an oxygen-containing gas supply device 24, an oxygen-containing gas exhaust pipe 26, a water spray device 28, a stripping device 30, an alkaline agent addition device 32, a nutrient source addition device 34, and a control device 36. Note that while the treatment system 1 shown in FIG. 1 is an example of a treatment system 1 that treats organic wastewater by methane fermentation, it may also be a treatment system 1 that treats organic waste by methane fermentation.

[0021] A plurality of hollow fiber membranes 22 are arranged in parallel so as to extend in the vertical direction of the reaction vessel 20. The hollow fiber membranes 22 are gas permeable and can selectively allow oxygen in an oxygen-containing gas (e.g., air) to pass through. The upper ends of the hollow fiber membranes 22 are connected to a hollow tubular upper header 38, and the lower ends of the hollow fiber membranes 22 are connected to a hollow tubular lower header 40. The interiors of the hollow fiber membranes 22 are in communication with the interiors of the upper header 38 and the lower header 40. When hydrogen sulfide is treated by the desulfurization device 16, a biofilm containing sulfur-oxidizing bacteria is formed on the outer surfaces of the hollow fiber membranes 22.

[0022] The oxygen-containing gas supply device 24 is a device that supplies an oxygen-containing gas to the hollow fiber membranes 22, and includes, for example, a blower 42 and an oxygen-containing gas supply pipe 44, as shown in Fig. 1. The oxygen-containing gas supply pipe 44 is connected to the lower header 40. The oxygen-containing gas supply pipe 44 is provided with the blower 42, an oxygen concentration sensor 46a, and a flow meter 48.

[0023] The oxygen-containing gas exhaust pipe 26 is connected to the upper header 38. The oxygen-containing gas exhaust pipe 26 is provided with an oxygen concentration sensor 46b.

[0024] The water spraying device 28 is a device that sprays water onto the outer surfaces of the hollow fiber membranes 22, and includes, for example, a storage tank 50 for storing water, a water supply pipe 52, a pump 54, and a spray nozzle 56, as shown in Fig. 1. One end of the water supply pipe 52 is connected to the storage tank 50, and the other end extends into the reaction tank 20. The spray nozzle 56 is installed on the other end of the water supply pipe 52.

[0025] The alkaline agent adding device 32 is a device that adds an alkaline agent to the water to be sprayed onto the hollow fiber membranes 22. The alkaline agent adding device 32 shown in Fig. 1 is configured to add an alkaline agent to the water stored in a storage tank 50. Examples of alkaline agents include sodium hydroxide, potassium hydroxide, and sodium carbonate.

[0026] The nutrient source adding device 34 is a device that adds nutrient sources to the water to be sprayed onto the hollow fiber membranes 22. The nutrient source adding device 34 shown in FIG. 1 is configured to add nutrient sources to water stored in a storage tank 50. Examples of nutrient sources include nitrogen sources, phosphorus sources, and trace metals such as alkali metals such as sodium, potassium, calcium, and magnesium, and metals such as iron, manganese, and zinc. Examples of nitrogen sources include urea and ammonium salts. Examples of phosphorus sources include phosphates and phosphoric acid.

[0027] The peeling device 30 is a device that peels off the biofilm formed on the outer surface of the hollow fiber membrane 22, and examples thereof include a vibrator that vibrates the hollow fiber membrane 22, a cleaning device that sprays water or gas onto the biofilm, or a scraper that scrapes off the biofilm.

[0028] A drainage pipe 58a is installed between the water outlet of the raw water tank 10 and the water inlet of the methane fermentation tank 12, a drainage pipe 58b is installed between the water outlet of the methane fermentation tank 12 and the water inlet of the aerobic treatment tank 14, and a treated water pipe 60 is installed at the water outlet of the aerobic treatment tank 14. In addition, a gas pipe 62a is installed between the gas outlet of the methane fermentation tank 12 and the gas inlet of the reaction tank 20, a gas pipe 62b is installed between the gas outlet of the reaction tank 20 and the gas inlet of the dry desulfurization tower 18, and a gas pipe 62c is installed at the gas outlet of the dry desulfurization tower 18.

[0029] The dry desulfurization tower 18 is filled with a desulfurization agent containing, for example, iron oxide as a main component.

[0030] The methane fermentation tank 12 holds, for example, sludge containing methanogenic bacteria and the like, and performs methane fermentation treatment using the sludge under anaerobic conditions. The aerobic treatment tank 14 holds, for example, sludge containing aerobic microorganisms and the like, and performs organic matter treatment using the sludge under aerobic conditions.

[0031] The control device 36 is composed of, for example, a microcomputer and electronic circuits, which are composed of a CPU that executes a predetermined program, and ROM and RAM that store the program, calculation results, etc. Although not shown, the control device 36 is connected, for example, by wire or wirelessly, to oxygen concentration sensors 46a and 46b, a flow meter 48, the alkaline agent addition device 32, the nutrient source addition device 34, and the stripping device 30. The control device 36 functions as a first control device that controls the operation and stop of the alkaline agent addition device 32, a second control device that controls the operation and stop of the nutrient source addition device 34, and a third control device that controls the operation and stop of the stripping device 30. The first control device, second control device, and third control device may be integrated into the control device 36, or may exist separately.

[0032] An example of the operation of the processing system 1 shown in FIG. 1 will be described.

[0033] The organic wastewater in the raw water tank 10 is wastewater containing organic matter discharged from, for example, a food manufacturing plant, an electronics factory, a pulp manufacturing plant, a chemical plant, etc. The organic wastewater is supplied from the raw water tank 10 to the methane fermentation tank 12 through the wastewater pipe 58a. In the methane fermentation tank 12, the organic wastewater is biologically treated under anaerobic conditions using sludge containing methanogenic bacteria. This biological treatment decomposes the organic matter in the organic wastewater, generating biogas containing methane gas and other substances. As mentioned above, the biogas contains hydrogen sulfide, an impurity. The treated water from the methane fermentation tank 12 is supplied through the wastewater pipe 58b to the aerobic treatment tank 14, where the remaining organic matter is decomposed by aerobic microorganisms under aerobic conditions. The treated water from the aerobic treatment tank 14 may be discharged from the treatment system 1 through the treated water pipe 60 or may be supplied to the storage tank 50 of the water spray device 28.

[0034] Biogas generated by the methane fermentation process described above is supplied to the reaction tank 20 through the gas piping 62a (biogas supply step). Air (oxygen-containing gas) supplied by the blower 42 is supplied to the hollow fiber membranes 22 through the lower header 40 (oxygen-containing gas supply step). The oxygen in the air permeates through the membrane surface of the hollow fiber membranes 22 and is introduced into the reaction tank 20. The oxygen that permeates from the hollow fiber membranes 22 into the reaction tank 20 is utilized by sulfur-oxidizing bacteria in a biofilm formed on the outer surface of the hollow fiber membranes 22, and hydrogen sulfide in the biogas is biologically treated. The hydrogen sulfide is oxidized primarily to sulfuric acid by the sulfur-oxidizing bacteria. The oxygen-containing gas passing through the hollow fiber membranes 22 is discharged outside the tank through the upper header 38 and the oxygen-containing gas exhaust piping 26.

[0035] In this embodiment, the amount of oxygen required for the sulfur-oxidizing bacteria to treat hydrogen sulfide is supplied through the hollow fiber membrane 22, which reduces the amount of oxygen wasted by the sulfur-oxidizing bacteria compared to when an oxygen-containing gas is directly introduced into the reaction vessel 20. As a result, hydrogen sulfide can be treated while suppressing a decrease in the concentration of methane gas in the biogas.

[0036] Furthermore, the pump 54 is operated to supply water from the storage tank 50 through the water supply pipe 52 to the spray nozzle 56, and the water is sprayed from the spray nozzle 56 onto the outer surface of the hollow fiber membrane 22 (water spraying process). This prevents the sludge containing sulfur-oxidizing bacteria from drying out, maintaining the activity of the sulfur-oxidizing bacteria. The temperature of the sprayed water is preferably adjusted to a range of 20 to 35°C in order to maintain the activity of the sulfur-oxidizing bacteria. A heating device may be installed in the storage tank 50 or the water supply pipe 52 to adjust the sprayed water to the above temperature. The water sprayed from the spray nozzle 56 accumulates at the bottom of the reaction tank 20 and is discharged from a drain pipe 64 installed at the bottom of the reaction tank 20. The water discharged from the drain pipe 64 may be returned to the storage tank 50 or supplied to the aerobic treatment tank 14.

[0037] When hydrogen sulfide is oxidized to sulfuric acid by sulfur-oxidizing bacteria, the pH in the reaction tank 20 decreases, which may result in a decrease in the activity of the sulfur-oxidizing bacteria. The pH in the reaction tank 20 is preferably in the neutral range, for example, in the range of 6.0 to 8.5, and more preferably in the range of 6.5 to 7.5, in order to maintain good activity of the sulfur-oxidizing bacteria. Therefore, it is preferable to operate the alkaline agent addition device 32 to add an alkaline agent to the water in the storage tank 50 (alkaline agent addition step). This allows water containing the alkaline agent to be sprayed from the spray nozzle 56, thereby suppressing a decrease in pH in the reaction tank 20 due to sulfuric acid production and maintaining the pH in the neutral range. The pH in the reaction tank 20 may be maintained in the neutral range by increasing the amount of water sprayed.

[0038] It is preferable to operate the nutrient source adding device 34 to add the nutrient source to the water in the storage tank 50 (nutrient source adding step). This causes the water containing the nutrient source to be sprayed from the spray nozzle 56, thereby suppressing a decrease in the activity of the sulfur-oxidizing bacteria.

[0039] The control device 36 may control the alkaline agent addition device 32 to adjust the amount of alkaline agent added, or may control the nutrient source addition device 34 to adjust the amount of nutrient added, based on the oxygen concentrations detected by the oxygen concentration sensors 46a and 46b and the flow rate of the oxygen-containing gas detected by the flow meter 48. The oxygen concentration detected by the oxygen concentration sensor 46a is the oxygen concentration in the oxygen-containing gas supplied to the hollow fiber membranes 22, and the oxygen concentration detected by the oxygen concentration sensor 46b is the oxygen concentration in the oxygen-containing gas exhausted from the hollow fiber membranes 22 to the outside of the reaction vessel 20. The flow rate of the oxygen-containing gas detected by the flow meter 48 is the flow rate of the oxygen-containing gas supplied to the hollow fiber membranes 22.

[0040] For example, the control device 36 acquires the oxygen concentration and the flow rate of the oxygen-containing gas from the oxygen concentration sensors 46a and 46b and the flow meter 48, and calculates the hourly oxygen consumption rate from these data. The control device 36 then adjusts the amount of alkaline agent and nutrient additives added based on the calculated hourly oxygen consumption rate. Because an increase or decrease in the hourly oxygen consumption rate is proportional to the amount of hydrogen sulfide treated by the sulfur-oxidizing bacteria, the control device 36 controls the alkaline agent addition device 32 and the nutrient source addition device 34 to increase the amount of alkaline agent and nutrient additives added based on an increase in the hourly oxygen consumption rate. Furthermore, the control device 36 controls the alkaline agent addition device 32 and the nutrient source addition device 34 to decrease the amount of alkaline agent and nutrient additives added based on a decrease in the hourly oxygen consumption rate. This control prevents a decrease in the activity of sulfur-oxidizing bacteria due to fluctuations in the hydrogen sulfide concentration in the biogas. It is also possible to perform control similar to that described above by calculating the amount of hydrogen sulfide treated per hour from the hydrogen sulfide concentration in the biogas, the hydrogen sulfide concentration after treatment, and the biogas flow rate to the reaction tank 20, but this involves the risk of the hydrogen sulfide concentration meter coming into contact with sulfuric acid and corroding the sensor. Therefore, in terms of stable measurement and control, the measurement of oxygen concentration described above is preferable.

[0041] Furthermore, the control device 36 may operate the peeling device 30 when the cumulative oxygen consumption calculated from the oxygen concentration detected by the oxygen concentration sensors 46a, 46b and the flow rate of the oxygen-containing gas detected by the flow meter 48 exceeds a predetermined value (peeling process). Specifically, the control device 36 sequentially acquires the oxygen concentration and the flow rate of the oxygen-containing gas from the oxygen concentration sensors 46a, 46b and the flow meter 48, and sequentially calculates the oxygen consumption per hour from these data. The control device 36 then integrates the sequentially calculated oxygen consumption per hour, compares the integrated value (i.e., the cumulative oxygen consumption) with a predetermined value, and operates the peeling device 30 when the integrated value exceeds the predetermined value. Since a certain amount of biofilm accumulated in excess on the outer surface of the hollow fiber membrane 22 can be peeled off, clogging of the hollow fiber membrane 22 can be avoided. Since the cumulative oxygen consumption rate is proportional to the cumulative hydrogen sulfide treatment rate, for example, the cumulative oxygen consumption rate may be multiplied by a predetermined coefficient to convert it into a cumulative hydrogen sulfide treatment rate, and the stripping device may be operated when the converted cumulative hydrogen sulfide treatment rate exceeds a predetermined value.

[0042] The oxygen-containing permeable membrane is not limited to the hollow fiber membrane 22, and may be a flat membrane, a spiral membrane, or the like. However, the hollow fiber membrane 22 is preferred because it allows for efficient treatment by forming a biofilm over a wide area on the outer surface of the membrane. Materials that can be used for the gas-permeable membrane include polypropylene, polyethylene, polysulfone, polyvinylidene fluoride, Teflon (registered trademark), silicone, and the like, which are commonly used in MABRs (Membrane Aerated Biofilm Reactors). In addition, it is preferable that the surface of the oxygen-containing permeable membrane is hydrophilized to increase its affinity for microorganisms.

[0043] The biogas desulfurized in the reaction tank 20 is supplied to the dry desulfurization tower 18 through the gas pipe 62b. In the dry desulfurization tower 18, hydrogen sulfide remaining in the biogas is adsorbed by a desulfurization agent. The biogas desulfurized in the dry desulfurization tower 18 is discharged from the gas pipe 62c and supplied to, for example, a device that uses the biogas.

[0044] [Note] (1) A desulfurization device that biologically treats hydrogen sulfide in biogas generated by methane fermentation of organic wastewater or organic waste using sulfur-oxidizing bacteria, A reaction tank to which the biogas is supplied; a non-porous oxygen-permeable membrane installed in the reaction vessel; an oxygen-containing gas supply means for supplying an oxygen-containing gas to the oxygen-permeable membrane; a pipe for discharging the oxygen-containing gas from the oxygen-permeable membrane to the outside of the reaction vessel; and a water spraying means for spraying water onto the outer surface of the oxygen permeable membrane. a desulfurization apparatus, characterized in that the oxygen-permeable membrane allows oxygen in the oxygen-containing gas to permeate into the reaction tank and supply it to a biofilm containing the sulfur-oxidizing bacteria that is formed on the outer surface of the oxygen-permeable membrane. (2) an alkaline agent adding means for adding an alkaline agent to the water; a first control device that controls the alkaline agent adding means; The desulfurization apparatus described in (1) above, wherein the first control device controls the alkaline agent addition means so that the amount of alkaline agent added is adjusted based on the oxygen concentration in the oxygen-containing gas supplied to the oxygen-permeable membrane, the oxygen concentration in the oxygen-containing gas exhausted from the oxygen-permeable membrane to outside the reaction vessel, and the flow rate of the oxygen-containing gas supplied to the oxygen-permeable membrane. (3) a nutrient source adding means for adding a nutrient source to the water; a second control device that controls the nutrient source adding means, The desulfurization apparatus according to (1) or (2) above, wherein the second control device controls the nutrient source adding means so that the amount of the nutrient source added is adjusted based on the oxygen concentration in the oxygen-containing gas supplied to the oxygen-permeable membrane, the oxygen concentration in the oxygen-containing gas exhausted from the oxygen-permeable membrane to outside the reaction vessel, and the flow rate of the oxygen-containing gas supplied to the oxygen-permeable membrane. (4) a peeling means for peeling the biofilm from the oxygen permeable membrane; a third control device that controls the peeling means, The desulfurization apparatus according to any one of (1) to (3), wherein the third control device activates the peeling means when a cumulative oxygen consumption calculated from the oxygen concentration in the oxygen-containing gas supplied to the oxygen-permeable membrane, the oxygen concentration in the oxygen-containing gas discharged from the oxygen-permeable membrane to the outside of the reaction vessel, and the flow rate of the oxygen-containing gas supplied to the oxygen-permeable membrane exceeds a predetermined value. (5) A desulfurization method for biologically treating hydrogen sulfide in biogas generated by methane fermentation of organic wastewater or organic waste using sulfur-oxidizing bacteria, a biogas supplying step of supplying the biogas to a reaction tank having a non-porous oxygen-permeable membrane installed therein; an oxygen-containing gas supply step of supplying an oxygen-containing gas to the oxygen-permeable membrane; a water spraying step of spraying water on the outer surface of the oxygen permeable membrane, a desulfurization method, characterized in that the oxygen-permeable membrane allows oxygen in the oxygen-containing gas to permeate into the reaction vessel and supply the oxygen to a biofilm containing the sulfur-oxidizing bacteria formed on the outer surface of the oxygen-permeable membrane. (6) An alkaline agent addition step of adding an alkaline agent to the water, The desulfurization method according to (5) above, wherein in the alkaline agent addition step, the amount of the alkaline agent added is adjusted based on the oxygen concentration in the oxygen-containing gas supplied to the oxygen-permeable membrane, the oxygen concentration in the oxygen-containing gas exhausted from the oxygen-permeable membrane to the outside of the reaction vessel, and the flow rate of the oxygen-containing gas supplied to the oxygen-permeable membrane. (7) A nutrient source adding step of adding a nutrient source to the water is provided, The desulfurization method according to (5) or (6), wherein the nutrient source adding step adjusts the amount of the nutrient source added based on the oxygen concentration in the oxygen-containing gas supplied to the oxygen-permeable membrane, the oxygen concentration in the oxygen-containing gas discharged from the oxygen-permeable membrane to the outside of the reaction vessel, and the flow rate of the oxygen-containing gas supplied to the oxygen-permeable membrane. (8) a peeling step of peeling the biofilm from the oxygen permeable membrane, The desulfurization method according to any one of (5) to (7), characterized in that the peeling step is performed when a cumulative oxygen consumption calculated from the oxygen concentration in the oxygen-containing gas supplied to the oxygen-permeable membrane, the oxygen concentration in the oxygen-containing gas discharged from the oxygen-permeable membrane to the outside of the reaction vessel, and the flow rate of the oxygen-containing gas supplied to the oxygen-permeable membrane exceeds a predetermined value. [Explanation of symbols]

[0045] 1 Treatment system, 10 Raw water tank, 12 Methane fermentation tank, 14 Aerobic treatment tank, 16 Desulfurization device, 18 Dry desulfurization tower, 20 Reaction tank, 22 Hollow fiber membrane, 24 Oxygen-containing gas supply device, 26 Oxygen-containing gas exhaust piping, 28 Water spray device, 30 Stripping device, 32 Alkaline agent addition device, 34 Nutrient source addition device, 36 Control device, 38 Upper header, 40 Lower header, 42 Blower, 44 Oxygen-containing gas supply piping, 46a, 46b Oxygen concentration sensor, 48 Flow meter, 50 Storage tank, 52 Water supply pipe, 54 Pump, 56 Spray nozzle, 58a, 58b Drainage pipe, 60 Treated water pipe, 62a-62c Gas pipe, 64 Drainage pipe.

Claims

1. A desulfurization device that biologically treats hydrogen sulfide in biogas generated by methane fermentation of organic wastewater or organic waste using sulfur-oxidizing bacteria, A reaction tank to which the biogas is supplied; a non-porous oxygen-permeable membrane installed in the reaction vessel; an oxygen-containing gas supply means for supplying an oxygen-containing gas to the oxygen-permeable membrane; a pipe for discharging the oxygen-containing gas from the oxygen-permeable membrane to the outside of the reaction vessel; and a water spraying means for spraying water onto the outer surface of the oxygen permeable membrane. a desulfurization apparatus, characterized in that the oxygen-permeable membrane allows oxygen in the oxygen-containing gas to permeate into the reaction tank and supply it to a biofilm containing the sulfur-oxidizing bacteria that is formed on the outer surface of the oxygen-permeable membrane.

2. an alkaline agent adding means for adding an alkaline agent to the water; a first control device that controls the alkaline agent adding means, 2. The desulfurization apparatus according to claim 1, wherein the first control device controls the alkaline agent adding means so that the amount of alkaline agent added is adjusted based on the oxygen concentration in the oxygen-containing gas supplied to the oxygen-permeable membrane, the oxygen concentration in the oxygen-containing gas exhausted from the oxygen-permeable membrane to outside the reaction vessel, and the flow rate of the oxygen-containing gas supplied to the oxygen-permeable membrane.

3. a nutrient source adding means for adding a nutrient source to the water; a second control device that controls the nutrient source adding means, 3. The desulfurization apparatus according to claim 1, wherein the second control device controls the nutrient source adding means so that the amount of the nutrient source added is adjusted based on the oxygen concentration in the oxygen-containing gas supplied to the oxygen-permeable membrane, the oxygen concentration in the oxygen-containing gas exhausted from the oxygen-permeable membrane to outside the reaction vessel, and the flow rate of the oxygen-containing gas supplied to the oxygen-permeable membrane.

4. a peeling means for peeling the biofilm from the oxygen permeable membrane; a third control device that controls the peeling means, 3. The desulfurization apparatus according to claim 1, wherein the third control device activates the stripping means when a cumulative oxygen consumption calculated from the oxygen concentration in the oxygen-containing gas supplied to the oxygen-permeable membrane, the oxygen concentration in the oxygen-containing gas discharged from the oxygen-permeable membrane to outside the reaction vessel, and the flow rate of the oxygen-containing gas supplied to the oxygen-permeable membrane exceeds a predetermined value.

5. A desulfurization method for biologically treating hydrogen sulfide in biogas generated by methane fermentation of organic wastewater or organic waste using sulfur-oxidizing bacteria, a biogas supplying step of supplying the biogas to a reaction tank having a non-porous oxygen-permeable membrane installed therein; an oxygen-containing gas supply step of supplying an oxygen-containing gas to the oxygen-permeable membrane; a water spraying step of spraying water on the outer surface of the oxygen permeable membrane, a desulfurization method, characterized in that the oxygen-permeable membrane allows oxygen in the oxygen-containing gas to permeate into the reaction vessel and supply the oxygen to a biofilm containing the sulfur-oxidizing bacteria formed on the outer surface of the oxygen-permeable membrane.

6. An alkaline agent addition step of adding an alkaline agent to the water, 6. The desulfurization method according to claim 5, wherein in the alkaline agent addition step, the amount of the alkaline agent added is adjusted based on the oxygen concentration in the oxygen-containing gas supplied to the oxygen-permeable membrane, the oxygen concentration in the oxygen-containing gas exhausted from the oxygen-permeable membrane to outside the reaction vessel, and the flow rate of the oxygen-containing gas supplied to the oxygen-permeable membrane.

7. a nutrient source adding step of adding a nutrient source to the water; 7. The desulfurization method according to claim 5, wherein in the nutrient source adding step, the amount of the nutrient source added is adjusted based on the oxygen concentration in the oxygen-containing gas supplied to the oxygen-permeable membrane, the oxygen concentration in the oxygen-containing gas exhausted from the oxygen-permeable membrane to the outside of the reaction vessel, and the flow rate of the oxygen-containing gas supplied to the oxygen-permeable membrane.

8. a peeling step of peeling the biofilm from the oxygen permeable membrane, 7. The desulfurization method according to claim 5, wherein the peeling step is performed when a cumulative oxygen consumption calculated from the oxygen concentration in the oxygen-containing gas supplied to the oxygen-permeable membrane, the oxygen concentration in the oxygen-containing gas discharged from the oxygen-permeable membrane to outside the reaction vessel, and the flow rate of the oxygen-containing gas supplied to the oxygen-permeable membrane exceeds a predetermined value.

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