Concentrated gas production apparatus and production method

Abstract

To provide an apparatus capable of efficiently producing concentrated gas of biogas and an efficient production method of concentrated gas of biogas.SOLUTION: An apparatus for producing concentrated gas obtained by concentrating methane gas in biogas comprising methane gas, carbon dioxide gas, and moisture, comprises: a compressor for compressing the biogas; a cooling device for removing part 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 part of the carbon dioxide gas and at least part of the residual moisture from the biogas heated by the heating device.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[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. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2017-18917 [Patent Document 2] Japanese Patent Application Laid-Open No. 2014-91766 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the method described in Patent Document 1 has problems such as the device becoming larger and being 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. [Means for solving the problem]

[0008] [1] An apparatus for producing concentrated gas by concentrating methane gas in biogas containing methane gas, carbon dioxide gas, and moisture, 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; 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 apparatus for producing concentrated gas 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 concentrated gas manufacturing apparatus according to any one of [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.

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

[0017]

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

[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. [Effects of the Invention]

[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. [Brief explanation of the drawings]

[0021] [Figure 1] FIG. 1 is a schematic diagram showing an example of the configuration of a concentrated gas production apparatus according to this embodiment. [Figure 2] FIG. 2 is a schematic diagram showing another example of the configuration of the concentrated gas production apparatus according to this embodiment. [Figure 3] FIG. 3 is a schematic diagram showing another example of the configuration of the concentrated gas production apparatus according to this embodiment. [Figure 4] FIG. 4 is a schematic diagram showing another example of the configuration of the concentrated gas production apparatus according to this embodiment. [Figure 5] FIG. 5 is a schematic diagram showing another example of the configuration of the concentrated gas production apparatus according to this embodiment. [Figure 6] FIG. 6 is a schematic diagram showing another example of the configuration of the concentrated gas production apparatus according to this embodiment. [Figure 7] FIG. 7 is a schematic diagram showing another example of the configuration of the concentrated gas production apparatus according to this embodiment. [Figure 8] FIG. 8 is a schematic diagram showing the configuration of the concentrated gas production apparatus 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] <Concentrated gas manufacturing equipment> 1, 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 biogas, a cooling device 3 for cooling the biogas compressed by compressor 2 to remove a portion of the moisture as condensed water, a heating device 5 for heating the biogas cooled by 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 heating device 5. The concentrated gas production apparatus 10 in this embodiment will be described below.

[0024] Biogas In this embodiment, "biogas" refers to a gas derived from at least one selected from the group consisting of livestock manure and food waste, and containing at least methane, carbon dioxide (CO2), and moisture. The methane concentration in the biogas is, for example, 50% to 65% by volume, the CO2 concentration in the biogas is, for example, 25% to 40% by volume, and the moisture concentration in the biogas is, for example, 0.01% to 10% by volume. The biogas may also contain other gases, such as nitrogen and oxygen. The nitrogen concentration in the biogas may be, for example, 5% to 15% by volume, and the oxygen concentration in the biogas may be, for example, 0.1% to 5% by volume.

[0025] When the biogas is derived from livestock manure, it contains hydrogen sulfide. In this case, it is preferable to remove the 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 term "enriched gas" refers to a gas obtained by removing at least CO2 and moisture from biogas and concentrating methane gas. The concentration of methane gas in the enriched gas is, for example, 80% to 95% by volume, the concentration of CO2 in the enriched gas is, for example, 3.0% by volume or less, and the concentration of moisture in the enriched 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 is 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] There are no particular limitations on the cooling device 3, and any conventionally known device can be used as long as it has the ability to cool the compressed biogas. 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. This keeps the moisture contained in the biogas in the form of 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 the 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 to 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. The biogas compressed by the compressor 2 has a high temperature, as described above. 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 also 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] 《Separation device》 The separator 6 separates at least a portion of the CO2 and at least a portion of the residual moisture from the biogas heated by the heater 5. 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 equipment) With reference to Figure 4, a case will be described in which the separation device 6 is a membrane separation device 6a. The membrane separation device 6a is equipped with a separation membrane (not shown) that selectively allows CO2 and moisture contained in the biogas to permeate. The biogas is directed to the separation membrane in the membrane separation device 6a, and the CO2 and moisture contained in the biogas are separated due to the partial pressure difference across the membrane. Note that the CO2 and moisture separated by the membrane separation device 6a may contain methane gas, so the separated CO2 and moisture may be directed back to the membrane separation device 6a to recover and recycle the methane gas.

[0044] The separation membrane is not particularly limited as long as it can selectively transmit CO2 and moisture, and may be an organic membrane or an inorganic membrane. 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 Separation Device) With reference to Figure 5, a case will be described in which the separator 6 is a temperature swing adsorption separator 6b. The temperature swing adsorption separator 6b is equipped with an adsorption tower that adsorbs CO2 and moisture contained in the biogas. The adsorption tower is filled with an adsorbent for adsorbing CO2 and moisture. The temperature swing adsorption separator 6b is used to perform each step using the temperature swing adsorption method, thereby separating CO2 and moisture from the biogas.

[0046] In the temperature swing adsorption method, for example, an adsorption cycle consisting of (1) an adsorption step, (2) a thermal regeneration step, (3) a purging step, and (4) a pressure recovery step is repeated in sequence.

[0047] (1) Adsorption process The adsorption process is a process in which biogas is supplied to an adsorption tower and the CO2 and moisture are adsorbed onto an adsorbent, thereby separating the CO2 and moisture from the biogas.

[0048] The adsorbent is a regenerative adsorbent that can adsorb CO2 and moisture and recovers its adsorption capacity by being heated to release the adsorbed CO2 and moisture. Examples of such adsorbents include activated carbon, silica gel, and hydrophobic zeolite.

[0049] (2)Heating regeneration process The thermal regeneration process is a process in which the adsorbent is heated and supplied to the adsorption tower after the adsorption process with an inert gas (hereinafter simply referred to as "inert gas"), or the adsorbent is directly heated, thereby desorbing CO2 and moisture from the adsorbent. In other words, the thermal regeneration process is a process in which the adsorbent filled in the adsorption tower is made reusable.

[0050] Examples of inert gases include gas obtained by removing CO2 and moisture from biogas in an adsorption process, and nitrogen gas. Such gases are heated and brought into contact with the adsorbent packed in the adsorption tower, thereby increasing the temperature of the adsorbent surface and desorbing the CO2 and moisture adsorbed on the adsorbent. This process regenerates the adsorbent. The heating temperature is, for example, 170°C or higher.

[0051] (3) Purging process The purging process is a process for removing the inert gas remaining in 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 introduced gas is, for example, a gas obtained by removing CO2 and moisture from biogas in the adsorption process. This process is preferably carried out until the inert gas is completely removed. Note that this process is unnecessary when the inert gas is a gas obtained by removing CO2 and moisture from biogas in the adsorption process.

[0052] (4) Repressurization process In the pressure recovery process, the adsorption tower after the adsorption process is restored to the pressure required for the adsorption process by introducing, for example, high-pressure gas. For example, gas obtained by removing CO2 and moisture from biogas in the adsorption process is used as the high-pressure gas.

[0053] In the temperature swing adsorption method, it is preferable to use multiple adsorption towers. For example, when two adsorption towers are used, while the adsorption step is being carried out in one adsorption tower, the thermal regeneration step, purging step, and pressure recovery step are being carried out in the other adsorption tower. By operating the two adsorption towers while switching between them in this way, it is possible to continuously and efficiently separate CO2 and water from biogas.

[0054] The temperature swing adsorption separation apparatus 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 Separation Unit) Referring to Figure 5, a case where the separator 6 is a pressure swing adsorption separator 6c will be described. The pressure swing adsorption separator 6c is equipped with an adsorption tower that adsorbs CO2 and moisture contained in the biogas. The adsorption tower is filled with an adsorbent for adsorbing CO2 and moisture. The pressure swing adsorption separator 6c is used to perform each step using the pressure swing adsorption method, thereby separating CO2 and moisture from the biogas.

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

[0057] The adsorption process is a process in which the biogas is supplied to an adsorption tower and the CO2 and moisture are separated from the biogas by adsorbing them onto an adsorbent. Note that the adsorbent is the same as the adsorbent that can be used in the temperature swing adsorption method described above, so a detailed explanation is omitted.

[0058] The desorption step is a step in which the pressure in the adsorption tower after the adsorption step is reduced to atmospheric pressure (0 MPaG) to desorb the CO2 and moisture adsorbed by the adsorbent. In the desorption step, the pressure in the adsorption tower may be reduced to -0.1 MPaG, for example, using a vacuum pump.

[0059] 6, separation device 6 preferably includes multiple 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 may include a dehumidifier 8 and a CO2 separator 9.

[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] The CO2 separator 9 may be a membrane separator or an adsorption separator. When the CO2 separator 9 is a membrane separator, the membrane separator is provided with a separation membrane (not shown) for selectively allowing CO2 contained in the biogas to permeate. Examples of such a separation membrane include organic membranes. Examples of organic membranes include the same as those described above. When the CO2 separator 9 is an adsorption separator, the adsorption separator is provided with an adsorption tower that adsorbs CO2 contained in the biogas. Examples of adsorbents filled in the adsorption tower include activated carbon, silica gel, and hydrophobic zeolite.

[0063] "tank" The tank 7 stores the concentrated gas and has a pressure-resistant structure.

[0064] The tank 7 is filled with an adsorbent. The adsorbent is capable of adsorbing methane gas. An example of such an adsorbent is activated carbon. Activated carbon is made from raw materials such as coconut shell, coal, charcoal, and phenolic resin. The activated carbon may be, for example, powdered activated carbon, crushed carbon, or granulated carbon. 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 of 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 <Concentrated gas production apparatus> will be omitted.

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

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

[0069] (Heating process) 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, then undergoes a cooling process, and is 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. That is, 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. That is, 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 step involves separating at least a portion of the CO2 and at least a portion of the residual moisture from the biogas after the heating step. The separation step results in a concentrated gas in which the methane gas in the biogas is concentrated.

[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 membrane separation, biogas is introduced into a membrane that selectively allows CO2 and water to pass through, and the CO2 and water are separated. In membrane separation, separation proceeds due to the partial pressure difference across the membrane.

[0074] In the temperature swing adsorption method, biogas is introduced into an adsorption tower filled with an adsorbent that adsorbs CO2 and water, and the CO2 and water are separated. As described above, the temperature swing adsorption method involves sequentially repeating the adsorption cycle 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, biogas is introduced into an adsorption tower filled with an adsorbent that adsorbs CO2 and water, and the CO2 and water are separated. As described above, the pressure swing adsorption method involves sequentially repeating the 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 temperature swing adsorption method or the pressure swing adsorption method after carrying out the membrane separation method.

[0077] The separation step may also include a dehumidification step and a CO2 separation step. In this case, it is preferable to perform the CO2 separation step after the dehumidification step. The dehumidification step may be a membrane separation step or an adsorption separation step. The CO2 separation step may be a membrane separation step or an adsorption separation step. [Example]

[0078] The following examples are provided to illustrate, but not 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 vol% methane, 34.1 vol% CO, 7.0 vol% water, 6.0 vol% nitrogen, and 1.5 vol% oxygen. The biogas discharged from buffer tank 1 was compressed to 0.8 MPaG by compressor 2. The biogas, which had risen to 300°C by compression, was cooled to 25°C by cooling device 3. After cooling, the biogas was temporarily stored in discharge tank 4 and heated to 35°C by heater 5b. The heated biogas was concentrated by membrane separation device 6a and stored in tank 7 as concentrated gas. An organic membrane was used as the separation membrane in membrane separation device 6a. The biogas composition was analyzed by gas chromatography (GL Sciences, MicroGC CP-4000).

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

[0081] <Result> In Example 1, the concentrated gas at point 1 in Figure 8 contained 91.9 vol% methane gas, 0.2 vol% CO2, 0.00137 vol% moisture, 7.6 vol% nitrogen gas, and 0.3 vol% oxygen gas.

[0082] In this way, by using the concentrated gas production device and production method described in the present disclosure, it is possible to remove CO2 and moisture from biogas and efficiently concentrate methane gas. Furthermore, since the present disclosure makes effective use of livestock manure that would otherwise be discarded, it can contribute to some of the activities 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. [Explanation of symbols]

[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 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; 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.

2. 2. The apparatus for producing concentrated gas 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 , wherein the separator includes a plurality of types of separators.

4. 2. The apparatus for producing concentrated gas according to claim 1, wherein the heating device is a heat exchanger or a heater.

5. 2. The concentrated gas producing apparatus according to claim 1, wherein the biogas is derived from at least one selected from the group consisting of livestock manure and food waste.

6. 2. The concentrated gas manufacturing apparatus according to claim 1, 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 a concentrated gas by concentrating methane gas in biogas containing methane gas, carbon dioxide gas, and moisture, comprising: a compression step of compressing the biogas; a cooling step of removing a portion of the moisture as condensed water by cooling the biogas after the compression step; a heating step of heating the biogas after the cooling step; a separation step of separating at least a portion of the carbon dioxide gas and at least a portion of the residual moisture from the biogas after the heating step.

8. The method for producing a concentrated gas according to claim 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.

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

10. The method for producing a concentrated gas according to claim 7 , wherein the biogas is heated by a heat exchanger or a heater in the heating step.

11. 8. The method for producing concentrated gas according to claim 7, wherein the biogas is derived from at least one selected from the group consisting of livestock manure and food waste.

12. 8. The method for producing concentrated gas according to claim 7, 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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