Production device and production method for concentrated gas

Abstract

Provided is a device for producing a concentrated gas obtained by concentrating methane gas in a biogas that contains the methane gas, carbon dioxide gas, and moisture, the device including: a compressor for compressing the biogas; a cooling device for cooling the biogas compressed by the compressor and thereby removing some of the moisture as condensate water; a heating device for heating the biogas cooled by the cooling device; and a separation device for separating at least some of the carbon dioxide gas and at least some of the residual moisture from the biogas heated by the heating device.

Description

Concentrated gas production device and production method

[0001] The present disclosure relates to an apparatus and method for producing concentrated gas.

[0002] In recent years, biogas derived from livestock manure such as dairy and beef cattle has been attracting attention due to issues such as global warming and the depletion of fossil fuels. Biogas is primarily composed of methane gas and carbon dioxide, and is expected to be an alternative energy source to fossil fuels.

[0003] Biogas was mainly generated by generators at large ranches and sold as electricity. However, small and medium-sized ranches that did not have generators were unable to fully utilize biogas. In addition, due to a lack of power transmission networks, even if electricity could be generated, it was difficult to sell the electricity.

[0004] Therefore, in order to fully utilize the collected biogas, methods for removing impurities such as carbon dioxide from the biogas are being considered at each ranch. Patent Document 1 (JP 2017-18917 A) discloses a method for recovering methane gas by separating volatile organic compounds, carbon dioxide, hydrogen sulfide, etc. from biogas using an adsorbent. Patent Document 2 (JP 2014-91766 A) discloses a method for recovering methane gas by separating carbon dioxide, etc. from biogas using a separation membrane.

[0005] JP 2017-18917 A JP 2014-91766 A

[0006] However, the method described in Patent Document 1 has problems such as the device becoming larger and being more costly.The method described in Patent Document 2 has problems such as a reduction in the recovery rate of methane gas because a pressurization / depressurization method is performed before the recovery of methane gas, which reduces the pressure of the methane gas.

[0007] An object of the present disclosure is to provide an apparatus capable of efficiently producing concentrated biogas gas, and an efficient method for producing concentrated biogas gas.

[0008] [1] An apparatus for producing concentrated gas by concentrating methane gas in biogas containing methane gas, carbon dioxide gas, and moisture, the apparatus comprising: a compressor for compressing the biogas; a cooling device for removing a portion of the moisture as condensed water by cooling the biogas compressed by the compressor; a heating device for heating the biogas cooled by the cooling device; and a separation device for separating at least a portion of the carbon dioxide gas and at least a portion of the residual moisture from the biogas heated by the heating device.

[0009] [2] The concentrated gas production apparatus according to [1], wherein the separation device is at least one device selected from the group consisting of a membrane separation device and an adsorption separation device.

[0010] [3] The concentrated gas production apparatus according to [1] or [2], wherein the separation device includes a plurality of types of separation devices.

[0011] [4] The concentrated gas production apparatus according to any one of [1] to [3], wherein the heating device is a heat exchanger or a heater.

[0012] [5] The concentrated gas production device according to any one of [1] to [4], wherein the biogas is derived from at least one selected from the group consisting of livestock manure and food waste.

[0013] [6] The biogas contains 50% by volume or more and 65% by volume or less of the methane gas, 25% by volume or more and 40% by volume or less of the carbon dioxide gas, and 0.01% by volume or more and 10% by volume or less of the moisture, [1] to [5]. A concentrated gas manufacturing apparatus according to any one of [1] to [5].

[0014] [7] A method for producing concentrated gas by concentrating methane gas in biogas containing methane gas, carbon dioxide gas, and moisture, the method comprising: a compression step of compressing the biogas; a cooling step of cooling the biogas after the compression step to remove some of the moisture as condensed water; a heating step of heating the biogas after the cooling step; and a separation step of separating at least some of the carbon dioxide gas and at least some of the remaining moisture from the biogas after the heating step.

[0015] [8] The method for producing a concentrated gas according to [7], wherein the separation step is carried out by at least one method selected from the group consisting of a membrane separation method and an adsorption separation method.

[0016] [9] The method for producing concentrated gas according to [7] or [8], wherein the separation step is carried out by a combination of a plurality of separation methods.

[0017]

[10] The method for producing a concentrated gas according to any one of [7] to [9], wherein the biogas is heated by a heat exchanger or a heater in the heating step.

[0018]

[11] The method for producing concentrated gas according to any one of [7] to

[10] , wherein the biogas is derived from at least one selected from the group consisting of livestock manure and food waste.

[0019]

[12] The method for producing concentrated gas described in any one of [7] to

[11] , wherein the biogas contains 50% by volume or more and 65% by volume or less of the methane gas, 25% by volume or more and 40% by volume or less of the carbon dioxide gas, and 0.01% by volume or more and 10% by volume or less of the moisture.

[0020] According to the present disclosure, it is possible to provide an apparatus capable of efficiently producing concentrated biogas gas, and an efficient method for producing concentrated biogas gas.

[0021] FIG. 1 is a schematic diagram showing an example of the configuration of an apparatus for producing concentrated gas in this embodiment. FIG. 2 is a schematic diagram showing another example of the configuration of an apparatus for producing concentrated gas in this embodiment. FIG. 3 is a schematic diagram showing another example of the configuration of an apparatus for producing concentrated gas in this embodiment. FIG. 4 is a schematic diagram showing another example of the configuration of an apparatus for producing concentrated gas in this embodiment. FIG. 5 is a schematic diagram showing another example of the configuration of an apparatus for producing concentrated gas in this embodiment. FIG. 6 is a schematic diagram showing another example of the configuration of an apparatus for producing concentrated gas in this embodiment. FIG. 7 is a schematic diagram showing another example of the configuration of an apparatus for producing concentrated gas in this embodiment. FIG. 8 is a schematic diagram showing the configuration of the apparatus for producing concentrated gas used in Example 1.

[0022] Hereinafter, embodiments of the present disclosure will be described, but the following description does not limit the scope of the claims.

[0023] 1 , the concentrated gas production apparatus 10 in this embodiment is an apparatus for producing concentrated gas by concentrating methane gas in biogas containing methane gas, carbon dioxide gas, and moisture, and includes a compressor 2 for compressing the biogas, a cooling device 3 for cooling the biogas compressed by the compressor 2 to remove a portion of the moisture as condensed water, a heating device 5 for heating the biogas cooled by the cooling device 3, and a separation device 6 for separating at least a portion of the carbon dioxide gas and at least a portion of the remaining moisture from the biogas heated by the heating device 5. The concentrated gas production apparatus 10 in this embodiment will be described below.

[0024] In the present embodiment, the term "biogas" refers to a gas derived from at least one selected from the group consisting of livestock manure and food waste, and contains at least methane, carbon dioxide (CO ２ The methane concentration in the biogas is, for example, 50% by volume or more and 65% by volume or less, and the CO ２The concentration of nitrogen in the biogas may be, for example, 25% by volume or more and 40% by volume or less, and the concentration of water in the biogas may be, for example, 0.01% by volume or more and 10% by volume or less. The biogas may also contain other gases such as nitrogen and oxygen. The concentration of nitrogen in the biogas may be, for example, 5% by volume or more and 15% by volume or less, and the concentration of oxygen in the biogas may be, for example, 0.1% by volume or more and 5% by volume or less.

[0025] When the biogas is derived from livestock manure, it contains hydrogen sulfide. In this case, it is preferable to remove hydrogen sulfide from the biogas. This is because hydrogen sulfide contained in the biogas may cause problems such as corrosion of the equipment included in the concentrated gas production apparatus 10.

[0026] <<Concentrated Gas>> In this embodiment, the “concentrated gas” refers to a gas that is a mixture of at least CO2 and CO2 from biogas. ２ The methane gas concentration in the concentrated gas is, for example, 80% by volume or more and 95% by volume or less, and the CO ２ The concentration of the hydrogen in the concentrated gas is, for example, 3.0% by volume or less, and the concentration of the water in the concentrated gas is, for example, 0.5% by volume or less.

[0027] <<Compressor>> The compressor 2 compresses the biogas. The biogas compressed by the compressor 2 is transferred to equipment downstream of the concentrated gas production apparatus 10.

[0028] The biogas may be compressed to, for example, 0.7 MPaG or more and 1.4 MPaG or less. The biogas is preferably compressed to 0.8 MPaG or more and less than 1.0 MPaG. When the compressed biogas has a pressure of 0.8 MPaG or more and less than 1.0 MPaG, it can be handled safely and efficiently transferred to downstream equipment of the concentrated gas production apparatus 10.

[0029] The compressor 2 is not particularly limited as long as it has the performance to compress the biogas to the above pressure, and a conventionally known compressor can be used.

[0030] <<Cooling Device>> The cooling device 3 cools the biogas compressed by the compressor 2. As a result, part of the moisture contained in the biogas is removed as condensed water.

[0031] The temperature of the compressed biogas has risen to, for example, 50 to 400°C. This biogas is cooled to a temperature at which the moisture in the biogas condenses, and some of the moisture is removed as condensed water. This prevents damage to downstream equipment of the concentrated gas production apparatus 10, such as the separation device 6.

[0032] The biogas may be cooled to, for example, 30° C. or less, 20° C. or less, 10° C. or less, 0° C. or less, −10° C. or less, or −20° C. or less. However, from the viewpoints of cost and energy efficiency, it is preferable that the biogas be cooled to 0 to 30° C.

[0033] The cooling device 3 is not particularly limited as long as it has the ability to cool the compressed biogas, and any conventionally known device can be used. An example of the cooling device 3 is a heat exchanger, and examples of the cooling source for the heat exchanger include a chiller, a refrigerator, and a cooling tower.

[0034] <<Heating Device>> The heating device 5 heats the biogas cooled by the cooling device 3. In this way, moisture contained in the biogas is retained as gas (water vapor).

[0035] The biogas cooled by the cooling device 3 contains moisture that was not completely removed by cooling. The moisture in the cooled biogas is saturated, and if biogas in this state is supplied to the separation device 6, which is a downstream facility, the moisture may damage the separation device 6. Therefore, by heating the biogas in this state and making it unsaturated, it is possible to prevent such a situation from occurring.

[0036] The extent to which the biogas is heated depends on the cooling temperature. However, since excessive heating of the biogas may reduce the recovery rate of concentrated gas, it is preferable not to heat the cooled biogas above a certain temperature. For example, it is preferable to heat the cooled biogas by 5 to 15°C. For example, if the biogas is cooled to 25°C by the cooling device 3, it is preferable to heat it to 30 to 40°C by the heating device 5.

[0037] The heating device 5 is not particularly limited as long as it has the ability to heat the cooled biogas, and any conventionally known device can be used. Examples of the heating device 5 include a heat exchanger and a heater (see FIGS. 2 and 3). From the viewpoint of energy efficiency, a heat exchanger is preferred as the heating device 5.

[0038] With reference to FIG. 2 , a case where the heating device 5 is a heat exchanger 5a will be described. The biogas compressed by the compressor 2 is introduced into the heat exchanger 5a, then introduced into the cooling device 3, and then introduced into the heat exchanger 5a again. As described above, the biogas compressed by the compressor 2 has a high temperature. Meanwhile, the biogas is cooled to a predetermined temperature by the cooling device 3 and then heated by the heat exchanger 5a. That is, the biogas compressed by the compressor 2 is used as a heat medium in the heat exchanger 5a to heat the biogas cooled by the cooling device 3. In this way, by using the heat exchanger 5a as the heating device 5, the biogas itself is used as a heat medium, and the cooled biogas can be efficiently heated. Note that the biogas compressed by the compressor 2 is cooled by being used as a heat medium in the heat exchanger 5a. That is, the biogas compressed by the compressor 2 is used as a heat medium, and at the same time, the biogas cooled by the cooling device 3 is used as a refrigerant.

[0039] The heat exchanger 5a is not particularly limited, and examples thereof include a plate heat exchanger, a plate fin heat exchanger, a coil heat exchanger, and a double pipe heat exchanger.

[0040] Referring to FIG. 3, when the heating device 5 is a heater 5b, the biogas cooled to a predetermined temperature by the cooling device 3 is heated by the heater 5b.

[0041] The separator 6 separates CO from the biogas heated by the heating device 5. ２ and at least a portion of the residual moisture are separated. This results in a concentrated gas in which the methane gas in the biogas is concentrated.

[0042] The separation device 6 may be at least one device selected from the group consisting of a membrane separation device and an adsorption separation device (see FIGS. 4 and 5). Examples of the adsorption separation device include a temperature swing adsorption separation device and a pressure swing adsorption separation device.

[0043] (Membrane Separation Device) A case where the separation device 6 is a membrane separation device 6a will be described with reference to Fig. 4. The membrane separation device 6a is a membrane separator for separating CO contained in biogas. ２ The biogas is led to the separation membrane in the membrane separation device 6a, and the CO contained in the biogas is separated. ２ and water are separated by the partial pressure difference across the membrane. ２ and moisture may contain methane gas, so the separated CO ２ The water may be returned to the membrane separation device 6a to recover and recycle methane gas.

[0044] The separation membrane ２ The membrane may be either organic or inorganic, as long as it is capable of selectively transmitting water and oxygen. Examples of organic membranes include polyethylene-based, polypropylene-based, polyimide-based, and cellulose acetate-based membranes. Examples of inorganic membranes include alumina-based and zeolite-based membranes.

[0045] (Temperature Swing Adsorption Separator) A case where the separator 6 is a temperature swing adsorption separator 6b will be described with reference to Fig. 5. The temperature swing adsorption separator 6b is a separator for separating CO contained in biogas. ２The adsorption tower is equipped with an adsorption tower that adsorbs CO and moisture. ２ The temperature swing adsorption separation device 6b is used to perform each step by the temperature swing adsorption method, thereby separating CO from the biogas. ２ and water is separated.

[0046] The temperature swing adsorption method involves sequentially repeating an adsorption cycle consisting of, for example, (1) an adsorption step, (2) a thermal regeneration step, (3) a purging step, and (4) a pressure recovery step.

[0047] (1) Adsorption process The adsorption process involves supplying biogas to an adsorption tower and ２ and moisture are absorbed by the adsorbent, and CO is extracted from the biogas. ２ and a process of separating water.

[0048] The adsorbent is CO ２ and moisture, and the adsorbed CO ２ and regenerative adsorbents whose adsorption performance is restored when moisture is released. Examples of such adsorbents include activated carbon, silica gel, and hydrophobic zeolite.

[0049] (2) Thermal regeneration step The thermal regeneration step is a step of heating and supplying a gas inert to the adsorbent (hereinafter simply referred to as "inert gas") to the adsorption tower after the adsorption step, or directly heating the adsorbent to remove CO from the adsorbent. ２ In other words, the thermal regeneration step is a step of making the adsorbent packed in the adsorption tower reusable.

[0050] The inert gas may be, for example, CO 2 extracted from biogas by an adsorption process. ２ The gases are heated and brought into contact with the adsorbent packed in the adsorption tower, thereby increasing the temperature of the adsorbent surface and reducing the CO2 adsorbed on the adsorbent. ２ The adsorbent is then heated to a temperature of, for example, 170°C or higher.

[0051] (3) Purging Process The purging process is a process for removing the inert gas from the adsorption tower after the thermal regeneration process. In this process, the inert gas is removed by introducing a gas into the adsorption tower. When the inert gas is nitrogen gas, the gas introduced is, for example, CO2 removed from the biogas in the adsorption process. ２ This process is preferably carried out until the inert gas is completely removed. ２ If the gas is one from which moisture has been removed, this step is unnecessary.

[0052] (4) Pressure Reinstatement Step In the pressure reinstatement step, for example, high-pressure gas is introduced into the adsorption tower after the adsorption step to restore the pressure to the pressure required for the adsorption step. ２ and gas from which moisture has been removed.

[0053] In the temperature swing adsorption method, it is preferable to use a plurality of adsorption towers. For example, when two adsorption towers are used, while an adsorption step is being performed in one adsorption tower, a thermal regeneration step, a purging step, and a pressure recovery step are being performed in the other adsorption tower. By operating the two adsorption towers while switching between them in this way, CO2 can be continuously and efficiently removed from the biogas. ２ and water separation.

[0054] The temperature swing adsorption separation device 6b is preferably equipped with a heating means (not shown). The heating means heats the inert gas used in the thermal regeneration step to a temperature at which the adsorbent packed in the adsorption tower can be reused. The heating means is not particularly limited, and examples thereof include a heater.

[0055] (Pressure Swing Adsorption Separator) A case where the separator 6 is a pressure swing adsorption separator 6c will be described with reference to Fig. 5. The pressure swing adsorption separator 6c is a separator for separating CO contained in biogas. ２ The adsorption tower is equipped with an adsorption tower that adsorbs CO and moisture. ２The pressure swing adsorption separation device 6c is used to perform each step by pressure swing adsorption, thereby separating CO from biogas. ２ and water is separated.

[0056] In the pressure swing adsorption method, for example, an adsorption cycle of (1) adsorption step, (2) purging step, (3) desorption step, and (4) pressure recovery step is repeated in sequence. Note that the (2) purging step and (4) pressure recovery step are the same as the (3) purging step and (4) pressure recovery step in the temperature swing adsorption method described above, and therefore a description thereof will be omitted.

[0057] The adsorption process involves supplying biogas to an adsorption tower and ２ and moisture are absorbed by the adsorbent, and CO is extracted from the biogas. ２ The adsorbent used in this process is the same as the adsorbent that can be used in the temperature swing adsorption method described above, and therefore a detailed description thereof will be omitted.

[0058] In the desorption step, the adsorption tower after the adsorption step is depressurized to atmospheric pressure (0 MPaG), and the CO adsorbed on the adsorbent is desorbed. ２ In the desorption step, the pressure in the adsorption tower may be reduced to −0.1 MPaG by using a vacuum pump, for example.

[0059] 6, separation device 6 preferably includes a plurality of types of separation devices. For example, when separation device 6 includes two separation devices, it is preferable that the separation devices be a combination of a membrane separation device and a temperature swing adsorption separation device or a pressure swing adsorption separation device.

[0060] 7, the separator 6 is connected to a dehumidifier 8 and a CO ２ The separator 9 may include:

[0061] The dehumidifier 8 may be a membrane separator or an adsorption separator. When the dehumidifier 8 is a membrane separator, a dehumidifying membrane (not shown) is installed in the membrane separator. When the dehumidifier 8 is an adsorption separator, an adsorption tower that adsorbs moisture contained in the biogas is installed in the adsorption separator. Examples of adsorbents that can be filled in the adsorption tower include zeolite, activated carbon, and activated alumina.

[0062] CO ２ The CO separation device 9 may be a membrane separation device or an adsorption separation device. ２ When the separator 9 is a membrane separator, the membrane separator contains CO ２ A separation membrane (not shown) is provided to selectively allow CO to pass through. Examples of such a separation membrane include an organic membrane. Examples of the organic membrane include the same as those described above. ２ When the separator 9 is an adsorption separator, the adsorption separator contains CO ２ The adsorption tower is equipped with an adsorption agent such as activated carbon, silica gel, or hydrophobic zeolite.

[0063] <<Tank>> The tank 7 stores concentrated gas. The tank 7 has a pressure-resistant structure.

[0064] The tank 7 is filled with an adsorbent. The adsorbent used is one capable of adsorbing methane gas. For example, activated carbon is used as such an adsorbent. Activated carbon is made from, for example, coconut shell, coal, charcoal, phenolic resin, etc. The activated carbon may be, for example, powdered activated carbon, crushed carbon, granulated carbon, etc. The particle size of the activated carbon may be, for example, 0.3 mm or more and 0.8 mm or less. In this embodiment, crushed carbon is preferably used.

[0065] Others The concentrated gas production apparatus 10 in this embodiment may include a buffer tank 1 and a discharge tank 4. The buffer tank 1 temporarily stores the biogas before compression. The discharge tank 4 temporarily stores the biogas after cooling.

[0066] <Method for Producing Concentrated Gas> The method for producing concentrated gas in this embodiment is a method for producing concentrated gas by concentrating methane gas in biogas containing methane gas, carbon dioxide gas, and moisture, and includes a compression process for compressing the biogas, a cooling process for cooling the biogas after the compression process to remove some of the moisture as condensed water, a heating process for heating the biogas after the cooling process, and a separation process for separating at least some of the carbon dioxide gas and at least some of the remaining moisture from the biogas after the heating process. The method for producing concentrated gas will be described below. Note that explanations that overlap with those described in the above <Apparatus for Producing Concentrated Gas> will be omitted.

[0067] (Compression Step) The compression step is a step of compressing the biogas. In the compression step, the biogas is compressed to, for example, 0.7 MPaG or more and 1.2 MPaG or less.

[0068] (Cooling step) The cooling step is a step of removing a portion of the moisture as condensed water by cooling the biogas after the compression step. In the cooling step, the biogas is cooled to a temperature at which the moisture in the biogas condenses. In the cooling step, the biogas is cooled to, for example, 30°C or below.

[0069] (Heating Step) The heating step is a step of heating the biogas after the cooling step. The heating step keeps the moisture contained in the biogas in a gaseous state (water vapor). The heating step heats the biogas, for example, by 5 to 15°C higher than the temperature after the cooling step.

[0070] When the heating process is performed using a heat exchanger, the biogas compressed in the compression process is introduced into the heat exchanger, undergoes a cooling process, and is then introduced into the heat exchanger again. The biogas compressed in the compression process has a high temperature (50 to 400°C). On the other hand, the biogas is cooled to a predetermined temperature in the cooling process and then heated in the heat exchanger. In other words, the biogas compressed in the compression process is used as a heat medium in the heat exchanger to heat the biogas cooled in the cooling process. In this way, when the heating process is performed using a heat exchanger, the biogas itself is used as a heat medium, and the biogas after the cooling process can be efficiently heated. Note that the biogas compressed in the compression process is cooled by being used as a heat medium in the heat exchanger. In other words, the biogas compressed in the compression process is used as a heat medium, and the biogas cooled in the cooling process is also used as a refrigerant.

[0071] (Separation process) The separation process is a process for separating CO from biogas after the heating process. ２ and at least a portion of the remaining moisture are separated. By the separation step, a concentrated gas in which the methane gas in the biogas is concentrated is obtained.

[0072] The separation step is carried out by at least one method selected from the group consisting of membrane separation and adsorption separation, such as temperature swing adsorption and pressure swing adsorption.

[0073] In the membrane separation method, CO ２ Biogas is introduced into a separation membrane that selectively allows the permeation of CO and water. ２ In membrane separation, separation occurs due to the partial pressure difference across the membrane.

[0074] In the temperature swing adsorption method, CO ２ The biogas is introduced into an adsorption tower filled with an adsorbent that adsorbs water and CO ２ As described above, the temperature swing adsorption process involves sequentially repeating an adsorption cycle consisting of (1) the adsorption step, (2) the thermal regeneration step, (3) the purging step, and (4) the pressure recovery step.

[0075] In the pressure swing adsorption method, CO ２ The biogas is introduced into an adsorption tower filled with an adsorbent that adsorbs water and CO ２ As described above, the pressure swing adsorption process sequentially repeats an adsorption cycle of (1) adsorption step, (2) purging step, (3) desorption step, and (4) pressure recovery step.

[0076] The separation step is preferably carried out by a combination of a plurality of separation methods. For example, when the separation step includes two separation methods, a combination of a membrane separation method and a temperature swing adsorption method or a pressure swing adsorption method is preferred. In this case, from the viewpoint of power consumption, it is more preferred to carry out the membrane separation method followed by the temperature swing adsorption method or the pressure swing adsorption method.

[0077] The separation process also includes a dehumidification process and a CO ２ In this case, after the dehumidification step, ２ The dehumidification step may be a membrane separation step or an adsorption separation step. ２ The separation step may be a membrane separation step or an adsorption separation step.

[0078] The following examples are provided to illustrate, but are not intended to limit the scope of the claims.

[0079] Example 1 A concentrated gas production apparatus having the configuration shown in Figure 8 was prepared. Biogas derived from livestock manure was prepared. The biogas contained 51.4% by volume of methane gas and 1.0% by volume of CO ２The biogas contained 34.1 vol% of sodium, 7.0 vol% of water, 6.0 vol% of nitrogen gas, and 1.5 vol% of oxygen gas. The biogas discharged from the buffer tank 1 was compressed to 0.8 MPaG by the compressor 2. The biogas, which had risen to 300°C by compression, was cooled to 25°C by the cooling device 3. After cooling, the biogas was temporarily stored in the discharge tank 4 and heated to 35°C by the heater 5b. The heated biogas was concentrated by the membrane separation device 6a and stored in the tank 7 as concentrated gas. The membrane separation device 6a used an organic membrane as the separation membrane. The composition of the biogas was analyzed by gas chromatography (GL Sciences, MicroGC CP-4000).

[0080] <Evaluation> The composition of the concentrated gas was measured at point 1 in Fig. 8. The analysis of the composition at point 1 was carried out by the gas chromatography described above. The pressure of the obtained concentrated gas was 0.8 MPaG, and the temperature was 35°C.

[0081] <Results> In Example 1, the concentrated gas at point 1 in FIG. 8 was 91.9% by volume of methane gas and 91.9% by volume of CO ２ The mixture contained 0.2% by volume of water, 0.00137% by volume of moisture, 7.6% by volume of nitrogen gas, and 0.3% by volume of oxygen gas.

[0082] In this way, by using the concentrated gas production device and production method described in the present disclosure, CO ２ The present disclosure also makes effective use of livestock manure that would otherwise be discarded, thereby contributing to some of the Sustainable Development Goals (SDGs).

[0083] The embodiments and examples disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims.

[0084] 1 Buffer tank, 2 Compressor, 3 Cooling device, 4 Discharge tank, 5 Heating device, 5a Heat exchanger, 5b Heater, 6 Separation device, 6a Membrane separation device, 6b Temperature swing adsorption separation device, 6c Pressure swing adsorption separation device, 7 Tank, 8 Dehumidification device, 9 Carbon dioxide separation device, 10 Concentrated gas production device.

Claims

1. An apparatus for producing concentrated gas by concentrating methane gas in biogas containing methane gas, carbon dioxide gas, and moisture, comprising: a compressor for compressing the biogas; a cooling device for cooling the biogas compressed by the compressor to remove a portion of the moisture as condensed water; a heating device for heating the biogas cooled by the cooling device; and a separation device for separating at least a portion of the carbon dioxide gas and at least a portion of the remaining moisture from the biogas heated by the heating device.

2. The concentrated gas production system according to claim 1, wherein the separation device is at least one device selected from the group consisting of a membrane separation device and an adsorption separation device.

3. The apparatus for producing concentrated gas according to claim 1 or 2, wherein the separation device includes a plurality of types of separation devices.

4. The concentrated gas production apparatus according to any one of claims 1 to 3, wherein the heating device is a heat exchanger or a heater.

5. A concentrated gas production apparatus according to any one of claims 1 to 4, wherein the biogas is derived from at least one material selected from the group consisting of livestock manure and food waste.

6. A concentrated gas manufacturing apparatus according to any one of claims 1 to 5, wherein the biogas contains 50% by volume or more and 65% by volume or less of the methane gas, 25% by volume or more and 40% by volume or less of the carbon dioxide gas, and 0.01% by volume or more and 10% by volume or less of the moisture.

7. A method for producing concentrated gas by concentrating methane gas in biogas containing methane gas, carbon dioxide gas, and moisture, the method comprising: a compression step of compressing the biogas; a cooling step of cooling the biogas after the compression step to remove some of the moisture as condensed water; a heating step of heating the biogas after the cooling step; and a separation step of separating at least some of the carbon dioxide gas and at least some of the remaining moisture from the biogas after the heating step.

8. The method for producing concentrated gas according to claim 7, wherein the separation step is carried out by at least one method selected from the group consisting of membrane separation and adsorption separation.

9. The method for producing concentrated gas according to claim 7 or 8, wherein the separation step is carried out by a combination of a plurality of separation methods.

10. A method for producing concentrated gas according to any one of claims 7 to 9, wherein the biogas is heated by a heat exchanger or a heater in the heating step.

11. A method for producing concentrated gas according to any one of claims 7 to 10, wherein the biogas is derived from at least one material selected from the group consisting of livestock manure and food waste.

12. A method for producing concentrated gas described in any one of claims 7 to 11, wherein the biogas contains 50% by volume or more and 65% by volume or less of the methane gas, 25% by volume or more and 40% by volume or less of the carbon dioxide gas, and 0.01% by volume or more and 10% by volume or less of the moisture.

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