JP2018188594A - Biogas refining system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the biogas refining system that can effectively utilize sulfide and carbon dioxide contained in biogas.SOLUTION: A provided biogas refining system comprises methane conversion means for producing methane from sulfide and carbon dioxide contained in the biogas.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a biogas purification system.

  The expansion of the use of renewable energy is expected, and efforts to effectively use biogas generated from biomass, which is a kind of renewable energy, are becoming more active. Biogas contains about 60% methane, about 40% carbon dioxide, and trace impurities such as hydrogen sulfide and siloxane.

  As mentioned above, biogas also includes gases other than methane, so in order to use biogas without purification, equipment dedicated to biogas is required, which is problematic in terms of cost and versatility. .

  Therefore, in recent years, various studies have been made on biogas purification systems that separate and purify methane using biogas purification technology.

  Various methods such as a high-pressure water absorption method, a PSA method, and a membrane separation method are known as biogas purification techniques. A configuration example of a biogas purification system using the high-pressure water absorption method is shown in FIG.

  As shown in FIG. 1, the conventional biogas purification system 10 pressurizes the biogas supplied from the biogas supply means 11 with the compressor 12 and supplies it to the absorption tower 13.

  Circulating water is supplied to the absorption tower 13 through a water supply pipe 131. Of the biogas supplied to the absorption tower 13, carbon dioxide other than methane gas and sulfide are absorbed into the circulating water. On the other hand, of the biogas, methane gas that has not been absorbed by the circulating water is recovered from the methane gas recovery pipe 132. The recovered methane gas can be recovered and stored in the tank 15 after being dehumidified by the dehumidifier 14, for example.

  Then, in the absorption tower 13, the absorption-treated water 133 mainly absorbing gas other than methane gas is sent to the decompression / deaeration tower 16, and is subjected to decompression and deaeration treatment, whereby the absorption-treated water 133 is converted into the absorption-treated water 133. The absorbed methane gas is recovered from the methane gas recovery pipe 161 for the decompression / deaeration tower. Further, the gas containing carbon dioxide or sulfide that has been absorbed in the absorption-treated water 133 is sent to the adsorption tower 17 using activated carbon or the like, and part of the gas is adsorbed by the adsorption tower 17 and the remainder Off-gas is released into the atmosphere.

  Further, the residual water 162 after being depressurized and degassed by the depressurization / deaeration tower 16 is recovered, and after adjusting the temperature by the heat exchanger 18 as necessary, the water supply pipe 131 is supplied with a predetermined pressure. Pressurized, sent, and used as circulating water.

  However, in the conventional biogas purification system 10, since most of the sulfides contained in the biogas are absorbed by the adsorption tower 17, the adsorbent such as activated carbon used in the adsorption tower 17 is used in the industry. It had to be treated as waste. Moreover, since most of the carbon dioxide contained in biogas is also released into the atmosphere, it cannot be said that the environmental load can be sufficiently reduced. For this reason, it has been demanded that sulfides contained in biogas and carbon dioxide are also effectively used to suppress the generation of industrial waste and to further reduce the environmental load.

  Then, in view of the problem which the said prior art has, it aims at providing the biogas refinement | purification system which can utilize the sulfide and carbon dioxide contained in biogas effectively in one side of this invention.

  According to one aspect of the present invention, there is provided a biogas purification system having methane conversion means for generating methane from sulfides contained in biogas and carbon dioxide.

  According to one embodiment of the present invention, a biogas purification system that can effectively utilize sulfides and carbon dioxide contained in biogas can be provided.

It is a figure which shows the structural example of the conventional biogas refinement | purification system. It is a figure which shows the structural example of the biogas purification system in the 1st Embodiment of this invention. It is a figure which shows the structural example of the biogas purification system in the 2nd Embodiment of this invention. It is a figure which shows the structural example of the biogas refinement | purification system in the 3rd Embodiment of this invention. It is a figure which shows the structural example of the biogas refinement | purification system in the 4th Embodiment of this invention.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. However, the present invention is not limited to the following embodiments, and the following embodiments are not departed from the scope of the present invention. Various modifications and substitutions can be made.

  The biogas purification system of the present embodiment can have methane conversion means for generating methane from sulfides contained in biogas and carbon dioxide.

  As described above, in the conventional biogas purification system, sulfides contained in biogas and carbon dioxide are not effectively used, and sulfides are adsorbed in an adsorption tower for the purpose of deodorization. The adsorbent used in the adsorption tower was treated as industrial waste. Carbon dioxide has been released to the atmosphere.

  Therefore, the inventors of the present invention have intensively studied the configuration of a biogas purification system that can effectively use sulfide and carbon dioxide, that is, as an energy source. As a result, it has been found that sulfides and carbon dioxide contained in biogas can be effectively utilized by providing a methane conversion means that generates methane from sulfides contained in biogas and carbon dioxide. Completed the invention.

  Below, the structural example of the biogas purification system of this embodiment is demonstrated, using drawing.

[First Embodiment]
A configuration example of the biogas purification system of the present embodiment will be described with reference to FIG.

  The biogas purification system 20 of this embodiment shown in FIG. 2 can have a methane conversion means 29 that generates methane from sulfides contained in the biogas and carbon dioxide.

  The methane conversion means 29 only needs to be configured to generate methane from sulfides contained in biogas and carbon dioxide, and the configuration is not particularly limited. According to the study by the inventors of the present invention, a methane conversion means using an anaerobic sulfur oxidation reaction can be preferably used as a methane conversion means for producing methane from sulfide and carbon dioxide. As a methane conversion means using such anaerobic sulfur oxidation reaction, specifically, for example, a reactor (reaction tank) using bacteria, bacteria or the like that can oxidize sulfur compounds even in the absence of oxygen. It is done. In such a reactor, bacteria and / or bacteria that can oxidize sulfur compounds even in the absence of oxygen are placed in the reactor in advance, and the sulfides and carbon dioxide in biogas are dissolved in the reactor. By supplying the generated water, sulfides can be oxidized, and at this time, methane can be generated.

  Bacteria and bacteria that can oxidize sulfur compounds even in the absence of oxygen are not particularly limited. For example, bacteria belonging to genus Smithella and phylum Caldiserica, and archaebacteria include Methanosaeta spp. Etc. As bacteria and bacteria that can oxidize sulfur compounds even in the absence of oxygen, for example, one or more selected from the above-mentioned archaea and bacteria can be used.

  Although it is not clear about the reaction in the reactor using bacteria, bacteria, or the like that can oxidize sulfur compounds even in the absence of oxygen, the inventors of the present invention have, for example, the following chemical formula (1). It is estimated that the reaction will proceed.

HS ⁻ + HCO ₃ ⁻ + H ₂ O → CH ₄ + SO ₄ ²⁻ (1)
As shown in Chemical Formula (1), HS sulfide ^- is being _SO ^{4 2-is} generated oxidized, this time, together with carbonate (HCO ₃ ^-) methane (CH ₄₎ is generated from.

  The reaction conditions in the methane conversion means are not particularly limited, and can be arbitrarily selected according to the configuration of the methane conversion means, the required conversion efficiency to methane, and the like. For example, from the viewpoint of particularly improving the conversion efficiency to methane, the temperature of the reactant in the reactor of the methane conversion means is preferably 10 ° C. or higher and 20 ° C. or lower. Further, the pH of the reactant in the reactor of the methane conversion means is preferably 7.0 or more and 8.5 or less.

  The methane conversion means can have a heating means and a cooling means in order to bring the temperature of the reactant in the reactor into a desired range. In addition, in order to set the pH of the reactant in the reactor of the methane conversion means within a predetermined range, a means for supplying a pH adjusting agent in the reactor of the methane conversion means or on a pipe connected to the methane conversion means, a pH value A pH detecting means for detecting the above can also be provided.

  In addition, when using an anaerobic sulfur oxidation reaction as mentioned above as a methane conversion means, it is preferable that the inside of the reactor of a methane conversion means is maintained in the atmosphere which does not contain oxygen. For this reason, it is preferable that the reactor of the methane conversion means is configured to have hermeticity in a portion other than the pipe connected to other reactors or the like so as to prevent air from entering from the outside. The atmosphere in the reactor of the methane conversion means can be controlled in advance before starting the biogas purification system, but when the reaction of the above chemical formula (1) starts, the reactor is replaced by the generated methane. Therefore, before the biogas purification system is started up, the atmosphere in the reactor need not be controlled in advance.

  As shown in FIG. 2, the methane produced by the methane conversion means 29 can be recovered and stored by a methane gas recovery pipe 291 for methane conversion means.

  As described above, when a methane conversion means using an anaerobic sulfur oxidation reaction is used as the methane conversion means 29, a part of the biogas, mainly a gas other than methane gas, is dissolved in water. It is preferable to supply water in which a part of the biogas is absorbed and dissolved. For this reason, the biogas purification system of this embodiment further includes an absorption tower that absorbs part of the biogas into water, and supplies the water that has absorbed part of the biogas to the methane conversion means. It is preferable to configure as described above.

  Specifically, as shown in FIG. 2, the biogas supplied from the biogas supply means 21 is purified and a methane gas is recovered on a piping path, and the biogas supply means 21 and the methane conversion means 29 are connected to each other. An absorption tower 23 can be provided therebetween.

  The absorption tower 23 only needs to be configured to absorb a part of the biogas into water, but the absorption tower 23 is preferably a high-pressure absorption tower in order to increase the absorption efficiency into water.

  Therefore, a compressor 22 for pressurizing biogas can be disposed between the biogas supply means 21 and the absorption tower 23. The pressure of the biogas pressurized by the compressor 22 is not particularly limited. For example, it is preferably higher than normal pressure (atmospheric pressure), that is, higher than 0.1 MPa, and particularly 0.9 MPa or higher. It is more preferable. For this reason, the high-pressure absorption tower is preferably an absorption tower that absorbs, for example, a gas of 0.5 MPa or more into water, and more preferably an absorption tower that absorbs a gas of 0.9 MPa or more into water.

  The absorption tower 23 is not limited to a high-pressure absorption tower, and an atmospheric pressure absorption tower or the like can be used as will be described later in the fourth embodiment. When an atmospheric pressure absorption tower is used instead of the high pressure absorption tower, for example, a biogas of normal pressure or higher supplied from the biogas supply means 21 can be supplied to the absorption tower without providing the compressor 22 as described later.

  By absorbing a part of the biogas in water by the absorption tower 23, a gas mainly composed of methane gas and sulfides absorbed in water, carbon dioxide, and the like can be separated. The methane gas can be recovered by the methane gas recovery pipe 232 connected to the absorption tower 23 as shown in FIG. About the collect | recovered methane gas, after dehumidifying, for example with the dehumidifier 24, it can collect | recover to the tank 25, and can be stored.

  Then, the absorption-treated water 233 that has absorbed a part of the biogas, for example, mainly gas other than methane gas, in the absorption tower 23 can be sent to the methane conversion means 29.

  Since the reaction in the methane conversion means 29 is already described, the description thereof is omitted. As described above, the methane gas generated in the methane conversion means 29 can be recovered by the methane gas recovery pipe 291 for the methane conversion means. About the collect | recovered methane gas, after dehumidifying, for example with the dehumidifier 24, it can collect | recover to the tank 25, and can be stored.

  The water treated in the methane conversion means 29 can be sent to, for example, the decompression / deaeration tower 26 via the treated water pipe 292 and decompressed and deaerated to be separated into off-gas and residual water. it can. In the decompression / deaeration tower 26, for example, when methane gas is generated when decompression processing is performed, a methane gas recovery pipe for decompression / deaeration tower (not shown) is connected to the decompression / deaeration tower, The methane gas can also be recovered from the methane gas recovery pipe 161 for the decompression / deaeration tower.

  About off-gas, since the content of sulfide and carbon dioxide can be sufficiently reduced, it can be discharged directly from the off-gas pipe 261 into the atmosphere.

  Residual water 262 after being depressurized and degassed by the depressurization / deaeration tower 26 is recovered, cooled by the heat exchanger 28 as necessary, the temperature is adjusted, and then the water supply pipe 231 of the absorption tower 23 is used. Can be pressurized to a predetermined pressure and sent to be used as circulating water. If necessary, new water can be added to the residual water 262 and mixed, and then supplied to the water supply pipe 231 to supply water to the absorption tower 23. In addition, since the circulating water can be supplied to the absorption tower 23 in this way, the water used in the absorption tower 23 is not limited to pure water. For example, the circulating water in which a part of biogas is dissolved is used. be able to.

  The biogas supply means 21 for supplying biogas to the biogas purification system of the present embodiment is not particularly limited. For example, sludge, sewage, garbage, biological excrement, organic fertilizer, biodegradable substances, etc. Biogas production means for producing biogas by fermentation and anaerobic digestion can be used. When using a biogas generating means as a biogas supply means, the biogas generating means only needs to be configured so as to ferment and anaerobically digest sludge and the like as raw materials and generate biogas. The configuration is not particularly limited. The biogas generation means includes, for example, a tank for fermenting and digesting the raw material, a raw material supply means for conveying and supplying the raw material to the tank as indicated by an arrow in FIG. 2, and a raw material in the tank. It can have a configuration equipped with a stirring means for stirring, a biogas exhaust means for taking out the generated biogas, and the like.

  Moreover, as the biogas supply means 21, for example, a biogas tank storing biogas generated elsewhere can be used.

  Also in the following other embodiments, the biogas supply means is not particularly limited, and for example, the above-described biogas generation means, a biogas tank, or the like can be used.

  In the biogas purification system 20 of the present embodiment, sulfides that have been conventionally discarded, and carbon dioxide are generated by using methane conversion means 29 that generates methane from sulfides contained in biogas and carbon dioxide. Can be effectively used as an energy source.

  Another configuration example of the biogas purification system will be described below with reference to the drawings. In addition, unless otherwise indicated, each reactor etc. can be comprised similarly to what was demonstrated in 1st Embodiment. For this reason, a part of the description overlapping with the already described contents is omitted.

[Second Embodiment]
The structural example of the biogas purification system of 2nd Embodiment is shown in FIG.

  In the biogas purification system 30 shown in FIG. 3, the components up to the absorption tower 33 can be configured in the same manner as in the case of the biogas purification system 20 shown in FIG. That is, the biogas supplied from the biogas supply means 31 can be compressed by, for example, the compressor 32 and supplied to the absorption tower 33, and a part of the biogas can be absorbed by water in the absorption tower 33. As the absorption tower 33, a high-pressure absorption tower can be preferably used as described above.

  Further, the methane gas separated in the absorption tower 33 can be recovered by a methane gas recovery pipe 332 connected to the absorption tower 33 as shown in FIG. About the collect | recovered methane gas, after dehumidifying, for example with the dehumidifier 34, it can collect | recover to the tank 35, and can be stored.

  In the biogas purification system 30, the absorption-treated water 333 in which a part of the biogas is absorbed by the absorption tower 33 is once sent to the decompression / degasification tower 36, and the absorption-treated water after the decompression process is finished, The methane conversion means 39 can be supplied.

  About the methane gas produced | generated in the methane conversion means 39, it can be collect | recovered by the methane gas collection | recovery piping 391 for methane conversion means. About the collect | recovered methane gas, after dehumidifying, for example with the dehumidifier 34, it can collect | recover to the tank 35, and can be stored.

  The water treated in the methane conversion means 39 can be sent again, for example, to the decompression / deaeration tower 36 via the treated water pipe 392 to carry out the deaeration process.

  The methane gas separated by the decompression / deaeration tower 36 can be recovered by the methane gas recovery pipe 361 for the decompression / deaeration tower. About the collect | recovered methane gas, after dehumidifying, for example with the dehumidifier 34, it can collect | recover to the tank 35, and can be stored.

  In the decompression / deaeration tower 36, the gas can be further separated into off-gas and residual water 362.

  About off-gas, since the content of sulfide and carbon dioxide can be sufficiently reduced, it can be released into the atmosphere from the off-gas pipe 363.

  Treatment is performed by the methane conversion means 39, and it is returned again to the decompression / deaeration tower 36. The residual water 362 after the deaeration treatment by the decompression / deaeration tower 36 is recovered, and cooled by the heat exchanger 38 as necessary. After adjusting the temperature and the like, it is sent to the water supply pipe 331 of the absorption tower 33 while being pressurized to a predetermined pressure, and can be used as circulating water. In addition, after adding new water and mixing to the residual water 362 as needed, water can also be supplied to the absorption tower 33 by the water supply piping 331. In addition, since the circulating water can be supplied to the absorption tower 33 in this way, the water used in the absorption tower 33 is not limited to pure water. For example, the circulating water in which a part of biogas is dissolved is used. be able to.

  As described above, when a reactor using bacteria, bacteria, or the like that can oxidize sulfur compounds even under conditions without oxygen as described above is used as the methane conversion means 29, depending on the type of bacteria, etc., When pressurized water is supplied, the conversion efficiency to methane may not be sufficiently high. In such a case, as shown in the biogas purification system 30 of the present embodiment, by supplying the water once decompressed to the methane conversion means 39, it is possible to efficiently convert to methane.

  Moreover, in the biogas purification system 30 of this embodiment, since the decompressed water is supplied to the methane conversion means 39, the methane conversion means 39 can use a reactor having a low pressure resistance.

[Third Embodiment]
An example of the configuration of the biogas purification system of the third embodiment is shown in FIG.

  In the biogas purification system 40 illustrated in FIG. 4, the components up to the absorption tower 43 can be configured in the same manner as the biogas purification system 20 illustrated in FIG. 2. That is, the biogas supplied from the biogas supply means 41 is compressed by the compressor 42 and supplied to the absorption tower 43, and a part of the biogas can be absorbed by water in the absorption tower 43. As the absorption tower 43, a high-pressure absorption tower can be preferably used as described above.

  Further, the methane gas separated in the absorption tower 43 can be recovered by a methane gas recovery pipe 432 connected to the absorption tower 43 as shown in FIG. About the collect | recovered methane gas, after dehumidifying, for example with the dehumidifier 44, it can collect | recover to the tank 45, and can be stored.

  In the biogas purification system 40, the absorption-treated water 433 that has absorbed a part of the biogas in the absorption tower 43 is sent to the decompression / degasification tower 46, and the decompression / degasification tower 46 performs decompression and degassing treatment can do.

  The methane gas separated by the decompression / degassing tower 46 can be recovered by the methane gas recovery pipe 461 for the decompression / degassing tower. About the collect | recovered methane gas, after dehumidifying, for example with the dehumidifier 44, it can collect | recover to the tank 45, and can be stored.

  In the biogas purification system 40 of the present embodiment, the residual water 462 after being depressurized and degassed by the depressurization / degassing tower 46 still contains sulfide and carbon dioxide. Can be supplied to the methane conversion means 49. About the methane gas produced | generated in the methane conversion means 49, it can be collect | recovered by the methane gas collection | recovery piping 491 for methane conversion means. About the collect | recovered methane gas, after dehumidifying, for example with the dehumidifier 44, it can collect | recover to the tank 45, and can be stored.

  The water treated in the methane conversion means 49 can be connected to a water supply pipe 431 connected to the absorption tower 43, pressurized to a predetermined pressure, and then supplied to the absorption tower 43 as circulating water. As in the case of the biogas purification system shown in the other embodiments, a heat exchanger (not shown) is provided, cooled, and the temperature is adjusted, and then water is supplied to the water supply pipe 431 of the absorption tower 43. It can also be supplied. Further, if necessary, water can be supplied to the absorption tower 43 through the water supply pipe 431 after adding and mixing fresh water with the water treated by the methane conversion means 49. Since the circulating water can be supplied to the absorption tower 43 in this way, the water used in the absorption tower 43 is not limited to pure water. For example, circulating water in which a part of biogas is dissolved may be used. it can.

  In the biogas purification system 40 of this embodiment, since the sulfide and carbon dioxide are not recovered from the absorption-treated water 433 supplied to the decompression / degasification tower 46, the biogas shown in the other embodiments Compared to the case of the purification system, the concentration of sulfide and carbon dioxide contained in the off-gas separated from the water 433 that has been subjected to the absorption treatment in the decompression / deaeration tower 46 is higher. For this reason, it is preferable to provide the adsorption tower 47 and release the off-gas to the atmosphere after adsorbing sulfides or the like in the adsorption tower 47.

  In the biogas purification system 40 of the present embodiment, the residual water 462 that has been subjected to the depressurization and deaeration treatment in the decompression / deaeration tower 46 is supplied to the methane conversion means 49 and absorbed into the residual water 462. Methane can be generated from the sulfides and carbon dioxide, and can be effectively used as an energy source.

[Fourth Embodiment]
The structural example of the biogas purification system of 4th Embodiment is shown in FIG.

  In the biogas purification system 50 shown in FIG. 5, an atmospheric pressure absorption tower is used as the absorption tower 53.

  For this reason, the biogas supplied from the biogas supply means 51 can be directly supplied to the absorption tower 53 without passing through the compressor. In the absorption tower 53, a part of biogas can be absorbed in water. Further, the methane gas separated in the absorption tower 53 can be recovered by a methane gas recovery pipe 532 connected to the absorption tower 53 as shown in FIG. About the collect | recovered methane gas, after dehumidifying, for example with the dehumidifier 54, it can collect | recover to the tank 55, and can be stored.

  In the absorption tower 53, the absorption-treated water 533 in which part of the biogas is absorbed can be supplied to the methane conversion means 59.

  About the methane gas produced | generated in the methane conversion means 59, it can be collect | recovered by the methane gas collection | recovery piping 591 for methane conversion means. About the collect | recovered methane gas, after dehumidifying, for example with the dehumidifier 54, it can collect | recover to the tank 55, and can be stored.

  The water treated in the methane conversion means 59 can be supplied to a water supply pipe 531 connected to the absorption tower 53, pressurized to a predetermined pressure, and then supplied to the absorption tower 53 as circulating water. As in the case of the biogas purification system shown in the other embodiments, a heat exchanger (not shown) is provided, cooled, and the temperature is adjusted, and then water is supplied to the water supply pipe 531 of the absorption tower 53. It can also be supplied. Moreover, after adding new water to the water treated by the methane conversion means 59 and mixing it, the water can be supplied to the absorption tower 53 through the water supply pipe 531. Thus, since the circulating water can be supplied to the absorption tower 53, the water used in the absorption tower 53 is not limited to pure water. For example, the circulating water in which a part of biogas is dissolved may be used. it can.

  In the biogas purification system 50 of this embodiment, since the atmospheric pressure absorption tower is used as the absorption tower 53, a compressor etc. can be abbreviate | omitted and the structure of a system can be simplified more. For this reason, methane can be produced | generated from the sulfide contained in biogas and a carbon dioxide, suppressing cost and an installation area especially, and can be utilized effectively as an energy source.

  As mentioned above, although the various structural examples were demonstrated about the biogas refinement | purification system, it is not limited to the above-mentioned 4 types of embodiment. For example, a system in which the elements described in the above-described four types of embodiments are combined can be used. Specifically, for example, in the biogas purification system 20 shown in the first embodiment, similar to the case of the biogas purification system 40 of the third embodiment, the residual water 262 generated in the decompression / deaeration tower 26. The methane conversion means provided separately may be supplied to further generate methane from sulfides and carbon dioxide contained in a very small amount in the residual water.

  In the biogas purification system of each embodiment, arbitrary members and means can be provided as necessary. For example, in the biogas purification system 20 shown in the first embodiment, an adsorption tower is provided on the offgas pipe 261, the offgas from the decompression / degasification tower 26 is supplied to the adsorption tower, and the sulfide concentration in the offgas It can also be configured to further reduce.

  Moreover, about each means demonstrated in the biogas refinement | purification system of each embodiment demonstrated so far, it can also replace with the member and means which have the same function. For example, in the depressurization / deaeration tower, the means for depressurization and the means for degassing may be provided separately.

Furthermore, the gas supplied to the biogas purification system described in the embodiments so far is not limited to biogas, and a mixed gas containing, for example, sulfide and carbon dioxide can also be used. Examples of the sulfide include hydrogen sulfide (H ₂ S).

  According to the biogas purification system described above, methane can be generated from sulfides contained in biogas and carbon dioxide. Therefore, according to the biogas purification system described in each of the above embodiments, sulfides and carbon dioxide in biogas that has been conventionally discarded can be effectively used as an energy source.

  Furthermore, according to the biogas purification system described in each of the above embodiments, carbon dioxide that has been conventionally exhausted to the atmosphere can be fixed, so that the biogas purification system can be a carbon negative system. .

  Conventionally, since sulfides in biogas are adsorbed on the adsorbent, the disposal cost of the adsorbent is necessary. In the biogas purification system described in each of the above embodiments, adsorption of sulfide by the adsorbent is performed. Or the amount of sulfide adsorbed on the adsorbent can be reduced, so that the disposal cost of the adsorbent can be eliminated or reduced, and the running cost of the biogas purification system can be suppressed. Become.

  As described with reference to FIG. 1, the conventional biogas purification system 10 supplies the biogas supplied from the biogas supply means 11 to the absorption tower 13 after being pressurized by the compressor 12. . And among the biogas supplied to the absorption tower 13, the carbon dioxide other than methane gas and sulfide were mainly absorbed in the circulating water. For this reason, an aeration process may be performed in order to process the sulfide absorbed in the circulating water. However, according to the biogas purification described in the above embodiments, the aeration process is unnecessary. The power load required for the aeration process can be reduced.

  And since the biogas purification system demonstrated by said each embodiment has a comparatively simple structure, a space-saving biogas purification system is realizable.

20, 30, 40, 50 Biogas purification system 23, 33, 43, 53 Absorption tower 29, 39, 49, 59 Methane conversion means

Claims (3)

  A biogas purification system having a methane conversion means for generating methane from sulfides contained in biogas and carbon dioxide. It further has an absorption tower for absorbing a part of the biogas into water,
The biogas purification system of Claim 1 which supplies the water which absorbed a part of biogas in the said absorption tower to the said methane conversion means.   The biogas purification system according to claim 2, wherein the absorption tower is a high-pressure absorption tower.

Images