Process and apparatus for treating methane-containing gas

Abstract

The invention relates to a process for treating methane-containing gas comprising CO2 and at least one compound from the group of volatile organic compounds (VOC), wherein the latter is selected from the group consisting of ketones, sulfur-containing hydrocarbons and terpenes and the VOC concentration in the gas mixture is 10 - 10 000 ppm. The methane-containing gas mixture is compressed and cooled and then supplied to an absorption apparatus, wherein the absorption apparatus comprises an absorption means which absorbs liquid VOC reversibly. In the absorption apparatus, at least a portion of the VOC and not more than 55% by volume of the CO2 is absorbed from the methane-containing gas mixture, thereby yielding a methane-containing and VOC- and CO2-reduced gas mixture and a VOC- and CO2-loaded absorption means. Thereafter, the VOC- and CO2-loaded absorption means is transported from the absorption apparatus to a desorption apparatus. Furthermore, the methane-containing and VOC-reduced gas mixture is supplied from the absorption apparatus to a separation apparatus in which CO2 is removed. In the desorption apparatus, a regeneration gas stream comprising at least a portion of the CO2-enriched gas stream is utilized for regeneration of the VOC- and CO2-loaded absorption means. Thereafter, the exhaust gas stream is discharged from the desorption apparatus and the at least partially regenerated absorption means is transported from the desorption apparatus into the absorption apparatus.

Description

[0001] Method and device for the treatment of methane-containing gas

[0002] The present invention relates to a process for the treatment of methane-containing gas according to claim 1 and to a device for carrying out said process.

[0003] In light of advancing global warming, CO2-neutral energy sources are becoming increasingly important for today's society. One proven method for obtaining such a CO2-neutral energy source is the fermentation of food waste in fermenters to produce biogas. Since foods such as fruit and vegetables absorb CO2 from the atmosphere during growth, the biogas produced during the fermentation of these foods and the methane it contains are CO2- and climate-neutral. In this application, biogas is understood to be a methane-containing gas mixture of natural origin. In addition to fermentatively produced biogas, for example from fermenters or landfills, biogas can also be of non-fermentative origin, for example in the form of natural gas, mine gas, or coal seam methane.

[0004] To make such methane-containing gas mixtures or biogases usable for energy generation, the methane concentration in the gas mixture must be increased by removing or at least reducing as many other compounds (so-called impurities) as possible. For this reason, fermentation-produced biogas, in particular, is usually purified to increase the methane content.

[0005] The use of suitable adsorbers is well known for the purification of gas mixtures, for example in industrial exhaust gas purification or in domestic applications, such as in extractor hoods. By adhering to the inner surface of porous adsorber materials, air pollutants, especially hydrocarbons, are removed from the gas mixture to be purified. Adsorbers can be classified as fixed-bed, moving-bed, rotor, fluidized-bed, and entrained-flow adsorbers. In multi-stage exhaust gas purification systems, adsorbers are often also used as the final purification stage, as so-called "police filters."

[0006] Today, contaminants in biogas can be removed using various biological, chemical, and physical processes, which is generally referred to as "(bio)gas upgrading" and represents an important application area of ​​gas purification. High-boiling-point compounds can be removed by adsorption, for example, on an activated carbon filter, while low-boiling-point compounds can be removed by condensation, and water-soluble compounds can be removed using a scrubber. Contaminants commonly present in biogas include carbon dioxide (CO2), hydrogen sulfide (H2S), ammonia (NH3), and volatile organic compounds (VOCs).

[0007] VOC is a collective term for organic substances, i.e., carbon-containing substances, that are volatile at room temperature or higher temperatures by evaporation (colloquially "evaporation"). Examples of VOC compounds are terpenes, ketones, amines, aldehydes, sulfur-containing hydrocarbons (S-HC), and others. Methane (CH4) is not considered a component of the VOC group for the purposes of this application.

[0008] The removal of VOCs is becoming increasingly important in exhaust gas purification, as reducing VOC emissions in industry and commerce is important for two reasons: firstly, for health reasons, as VOCs in the ambient air can cause people to develop certain symptoms such as headaches, hypersensitivity reactions, fatigue, reduced performance, sleep disturbances, and respiratory irritation, which are also summarized under the term "sick building syndrome." Secondly, the presence of VOCs in industrially used gas mixtures can lead to failures, damage, and reduced efficiency in treatment or injection plants, which have a rapid financial impact.In membrane systems used for gas purification, condensed terpenes can impair filter capacity, while ketones can damage seals, resulting in shorter maintenance intervals and earlier and more frequent membrane replacement. Therefore, special processes have been developed for both exhaust air purification and biogas upgrading to remove VOCs from gas mixtures at an early stage.

[0009] US 2019 / 0001263 A1 discloses a process for removing CO2, O2, N2, and VOCs from biogas. In a first step, the gas is compressed, and then the VOCs are removed successively using a first adsorber (preferably a pressure-temperature swing absorption device, or "PTSA" for short). Subsequently, the CO2 is removed using a cryogenic membrane, and finally, O2 and N2 are separated using a second adsorber (preferably a PTSA) to obtain purified biogas. This process, with three separate separation media (two PTSAs and one membrane), is relatively complex and therefore costly and maintenance-intensive. In particular, the two parallel PTSAs must be heated to regenerate the adsorption medium and then cooled back down to operating temperature to ensure a continuous process.

[0010] WO 2017099581 A2 discloses a process for purifying a feed gas. The feed gas is compressed, and water is removed from the compressed gas. VOCs, carbon dioxide, and any water are then removed from the gas using an absorber. The aim of the process described in WO 2017099581 A2 is, among other things, to extract the maximum amount of carbon dioxide from the feed gas in order to further use this carbon dioxide. The process has been optimized in such a way that the absorber is recycled using two absorption devices connected in series, and the components extracted from the feed gas are partially fed back into the purification process to minimize carbon dioxide loss. A disadvantage of the described process is that VOCs with a low boiling point cannot be removed; they remain in the cycle due to recirculation and therefore accumulate in the plant.In this context, low-boiling-point VOCs are understood to mean compounds with a boiling point below 50 °C. The present invention therefore aims to eliminate the above-described disadvantages of the prior art and to provide an improved process for removing contaminants, in particular CO2 and VOCs, from a methane-containing gas mixture, which allows for an efficient and effective reduction of the CO2 and VOC content.

[0011] The object is achieved according to the invention with a method according to claim 1 and a device according to claim 16. Preferred embodiments of the invention are recited in the dependent claims.

[0012] In the process according to the invention, in a first step a), a methane-containing gas mixture comprising CO2 and at least one compound from the group of volatile organic compounds (VOCs) is provided. Hereinafter, instead of the term "compound from the group of volatile organic compounds (VOCs), the term "VOC compound" is optionally used. According to the invention, the at least one VOC compound is selected from the group consisting of ketones, sulfur-containing hydrocarbons, and terpenes. Furthermore, according to the invention, the VOC concentration in the methane-containing gas mixture is 10-10,000 ppm. In a second step b), the methane-containing gas mixture is compressed and cooled. In a third step c), the compressed, cooled methane-containing gas mixture is fed to an absorption device, wherein the absorption device comprises a liquid VOC-reversibly absorbing absorbent.In a fourth step d), at least a portion of the VOC compound and a maximum of 5 vol.% of the CO2 is absorbed from the methane-containing gas mixture by the absorption medium in the absorption device, thereby obtaining a methane-containing, VOC- and CO2-reduced gas mixture and a VOC- and CO2-laden absorption medium. In a fifth step e), the VOC- and CO2-laden absorption medium from the absorption device is fed to a desorption device. In a sixth step f), the methane-containing, VOC- and CO2-reduced gas mixture from the absorption device is fed to a separation device comprising a membrane, in which the methane-containing, VOC- and CO2-reduced gas mixture is separated into a pressure-reduced, CO2-enriched gas stream and an isobaric methane-enriched gas stream.In a seventh step g), a regeneration gas stream comprising at least a portion of the CO2-enriched gas stream from step f) is fed to the desorption device for regenerating the VOC- and CO2-laden absorbent, thereby obtaining an exhaust gas stream containing CO2 and the at least one VOC compound, as well as an at least partially regenerated absorbent. In an eighth step h), the exhaust gas stream from the seventh step is discharged from the desorption device to a regenerative afterburner, and the at least partially regenerated absorbent from the desorption device is fed to the absorption device.

[0013] For the purposes of the invention, the term "liquid" refers to a liquid state under standard conditions, i.e., at 1 bar ambient pressure and 20°C. For the purposes of the invention, the term "reversibly absorbing" refers to a reversible interaction between an absorbent and a compound to be absorbed, whereby said compound reversibly binds to the absorbent and can also be released from it. It is not excluded that, for example, a VOC-reversibly absorbing absorbent can also reversibly absorb other compounds such as CO2.

[0014] For the purposes of the invention, the term “absorbent” is understood to mean a material which can at least temporarily bind a compound to be absorbed.

[0015] The process according to the invention preferably uses a drip-capable absorbent, i.e. an absorbent capable of forming droplets or small liquid droplets. For example, for water, a droplet volume (i.e. the volume of a typical droplet) of approximately 50 μl is assumed. It will be clear to those skilled in the art that the droplet volume must be determined individually for each absorbent. The example of water is merely a guide. The formation of droplets increases the surface area of ​​the absorbent, which in turn increases its efficiency. A commercially available liquid distributor is preferably used to generate droplets. Furthermore, random packings or structured packings can also preferably be used to better distribute the gas and thus optimize the contact between gas and absorbent.The design of the absorption device is chosen so that it operates below the flood point of a packing or absorbent to prevent it from being forced out of the absorption device by the gas flow. Physical barriers can also be installed to prevent this entrainment. Droplet traps and grids are conceivable.

[0016] For the purposes of the invention, the term “pressure-reduced” means that the pressure of a gas is reduced, for example by expanding the pressure of a gas.

[0017] Furthermore, for the purposes of the invention, the term "isobaric" means that the pressure conditions do not change or change only insignificantly. A change of up to ± 5% is considered insignificant.

[0018] Although the steps in the process according to the invention are numbered, it is clear to those skilled in the art that certain steps can also be performed in parallel. For example, steps e) and f) can take place in parallel.

[0019] The method according to the invention has the advantage over known methods from the prior art that, due to the spatial separation of the absorption and desorption of VOCs, the devices - in particular the containers in the devices in which the above-mentioned absorption and desorption take place - are not exposed to changing loads and thus their service life is extended.

[0020] Replacing the loaded absorbent with a less loaded absorbent requires only a short amount of time and enables continuous purification of the methane-containing gas mixture. Furthermore, the process according to the invention reduces the production costs for purified biogas, as the process requires only one absorption device, which can also be operated more cost-effectively because the absorbent is regenerated and not consumed, as would be the case with activated carbon as an absorbent, for example.

[0021] A further advantage of the process according to the invention over the prior art is that it uses a liquid absorbent. This can therefore be pumped from a first container to a second container and is easier to handle than the adsorbents disclosed in the prior art, which are usually in bulk form.

[0022] The use of a membrane in the process according to the invention also has the advantage that the separation of CO2 can be carried out continuously and, in contrast to other separation devices such as a PTSA, the membrane is less complex to maintain.

[0023] The use of CO2, which originates from the membrane, as the regeneration gas has the advantage of being virtually pressureless and virtually VOC-free. This reduces costs that would be incurred if a separate regeneration gas were provided, as this gas is continuously consumed. During the desorption of VOCs from the absorbent, the absorbent is loaded with CO2 in the desorption device and leaves the desorption device as a CO2-laden absorbent. Cooling the absorbent before entering the absorption device frees up additional absorption sites in the absorbent, allowing it to absorb CO2 again in the absorption device.

[0024] However, it will be clear to the person skilled in the art that the regeneration gas may also be provided separately, for example if the CO2 gas stream from the membrane is used for another purpose or if it is preferred to purify the absorbent with another regeneration gas, for example N2.

[0025] In a preferred embodiment of the process, a single absorption device is used in step d). An advantage of using only one absorption device instead of two absorption devices connected in series, as disclosed in the prior art, is that a process with only one absorption device is more cost-effective to build and maintain than a plant with multiple absorption devices.

[0026] In a further preferred embodiment of the process, the absorption device in step d) comprises at least four stages. Stages, as defined in the application, are understood to be intermediate floors in the absorption device that divide the absorption process into separate subprocesses. The use of at least four stages in the absorption device enables the absorption of the highest possible concentration of a VOC compound, as shown later in Figures 3-11.

[0027] Preferably, in step h), the exhaust gas stream generated in step g) from the desorption device is fed to a regenerative afterburner for oxidation. This allows both the VOC compound and any methane components present to be oxidized, allowing the exhaust gas stream to be released into the environment. The destruction of the VOCs eliminates additional disposal costs, increasing the profitability of the entire biogas upgrading plant. By using the CO2-enriched permeate as regeneration gas, which is subjected to oxidation after use, the so-called methane slip in the CO2-enriched permeate is also simultaneously subjected to oxidation, preventing its emission into the atmosphere.

[0028] A regenerative afterburner usually consists of a mixing device in which the gas mixture to be burned is mixed with air as an oxygen source, a heat exchanger device in which the gas mixture to be burned, mixed with air, is heated by the heat of the burned gas mixture, whereby the burned gas mixture is cooled, a combustion chamber in which the organic components of the gas mixture are completely oxidized and a chimney through which the burned gas mixture is released into the atmosphere.

[0029] In a preferred embodiment, at least steps f) and h), particularly preferably steps c) to h), are carried out continuously. This has the advantage that the process for processing methane-containing gas can be operated more efficiently and economically than if the gas is only processed in batches. Furthermore, the continuous operation is less prone to errors, in contrast to the cyclical switching normally proposed in the prior art, since no error-prone fittings are required to monitor the

[0030] Switching is required. In a preferred embodiment, in step c) in the absorption device, 2 to 10 liters of absorbent per Bm 3 methane-containing gas mixture from step b) is used.

[0031] The unit Bm 3, which stands for operating cubic meters, defines, for the purposes of the application, the actual volume of the gas in the operating state. The operating volume of the gas can be determined with sufficient accuracy as a first approximation using the ideal gas equation.

[0032] Preferably, in step g) in the desorption device, 1 to 3 liters of VOC-laden absorbent from step d) are mixed with 1 Bm 3 regenerated from CO2-enriched gas from step f).

[0033] In a preferred embodiment, the VOC-adsorbing absorbent has a boiling point of >250°C at 1013.25 mbar and comprises a compound selected from the group consisting of polyethylene glycol (PEG), mineral oil, esters or combinations thereof, with polyethylene glycol being particularly preferred.

[0034] Absorbents with the above-mentioned properties are particularly well suited for the process according to the invention because they efficiently absorb and desorb VOCs – under clearly separated conditions, without requiring particularly complex conditions to achieve. This means that these absorbents can ensure a cost-effective and efficient treatment process.

[0035] Preferably, the VOC-reversibly absorbing absorbent comprises a compound according to formula (I):

[0036] I) R1-O-(CH2CH2O) n -R2, where n = 3 to 8 and

[0037] R1 and R2 independently selected linear C1- C 10 are alkyls.

[0038] Based on formula (I), the VOC-reversibly absorbing absorbent is particularly preferably a compound (Ia) with R1-O-(CH2CH2O) n -R2, where n = 11 and R1 and R2 = CH3.

[0039] The preferred compound (la) is therefore CH3-O-(CH2CH2O) 11 -CH3.

[0040] Another preferred absorbent is known under the name Genosorb 300 with CAS No. 24991-55-7.

[0041] It has surprisingly been found that the absorbents according to formula (I) are particularly suitable for the process according to the invention for the reasons stated above.

[0042] Another preferred absorbent is the stabilized reaction product of 5,8,11,14-tetraoxaoctadecane and 5,8,11,14,17-pentaoxaheneicosane - also known as Genosorb 1843.

[0043] In a preferred embodiment, the at least one VOC compound has a vapor pressure of at least 0.1 mbar at 20 °C and / or a boiling point of at most 240 °C at 1013.25 mbar.

[0044] In a preferred embodiment, the at least one VOC compound is selected from the group consisting of acetone, 2-butanone, 3-methyl-2-butanone, 2-pentanone,

[0045] 3-pentanone, 3,3-dimethyl-2-butanone, 2-methyl-3-pentanone,

[0046] 4-Methyl-2-pentanon, 3-Methyl-2-pentanon, 3-Hexanon, 2- Hexanon, 5-Methyl-3-hexanon, 3-Methyl-2-hexanon, 2- Heptanon, 4-0ctanon, 3-0ctanon, 2-Octanon, 2,9- Decandion, α-Thujen, α-Pinen, Camphen, Sabinen, ß-Pinen, Myrcen, 3-Caren, Thujanon, Thujopsen, Thymol, α- Terpinen, ß-Caryophyllen, 1,4-Cineol, Eucalyptol, Fenchon, Y-Terpinen, Terpinoien, Limonen, Tricyclen, Linalool, Menthon, Nopinon, p-Menthan-2-on, p-Menthan-2- ol, Campher, Carvomenthon, 3,3-Dimethyl-2-bornanon, Carbonylsulfid, Methylmercaptan, Ethylmercaptan, Dimethylsulfid, Kohlenstoffdisulfid, 2-Propanthiol, 2- Methyl-2-propanthiol, 1-Propanthiol, Thiophen, 2- Butanthiol, Isobutylmercaptan, Methyl-Allyl-Sulfid, Methylpropylsulfid, Butanthiol, Dimethyldisulfid, 2- Methylthiophen, 3-Methylthiophen, Tetrahydrothiophen, 1- Pentanthiol, Thiophenol, Dimethyltrisulfid, Diisopropyldisulfid, Dimethyltetrasulfid, Methylpropyldisulfid und Methylisopropyldisulfid.It goes without saying that mixtures of the compounds mentioned can also be used.

[0047] It has been shown that the process according to the invention is also suitable for processing a gas mixture comprising at least two VOC compounds. Preferably, the gas mixture accordingly comprises at least one further VOC compound selected from the group consisting of aldehydes, alcohols, amines, BTEX, esters, ethers, CFCs, and siloxanes.

[0048] In a preferred embodiment, the at least one further VOC compound is selected from the group consisting of linear or branched C1-C5 alcohols, sulfides and terpenes.

[0049] Preferably, the at least one further VOC compound is selected from the group consisting of 2-methylbutyraldehyde, acetaldehyde, decanal, formaldehyde, hexanal, isobutyraldehyde, isopentanal, n-butyraldehyde, propylaldehyde, 1-butanol, 1-propanol, 2-butanol, 2-ethylhexanol, 2-methyl-l-butanol, 2-methyl-l-propanol, 2-methyl-2-butanol, 2-methyl-3-pentanol, 3-methyl-l-butanol, 3-pentanol, ethanol, isopropanol, methanol, 4,4-dimethyloxazolidine, 1,4-dimethylpiperazine, 1-methylpiperazine, 1-methylpyrrole, 4-methylpiperazine-l-ethanol, dimethylaminoethanol, dimethylpiperazine, Methyldiethanolamine, N-aminoethanol-piperazine, piperazine, pyridine, 1,2,3-trimethylbenzene, 1,2,4-trimethylbenzene, 1,3,5-trimethylbenzene, benzene, ethylbenzene, ethyltoluene, m-xylene, o-xylene, propylbenzene, p-xylene, styrene, toluene, 6,6-Dimethyl-tetrahydropyran-2-one, butyric acid ethyl ester, butyric acid methyl ester, butyric acid propyl ester, dimethyl carbonate, ethyl acetate, heptanoic acid ethyl ester, hexanoic acid methyl ester,Isobuttersäureethylester, Isobuttersäuremethylester, Isopropylacetat, Methylacetat, Methylf ormiat, n-Butylacetat, n- Propylacetat, n-Propylpropionat, Pentansäureethylester, Pentansäuremethylester, Propionsäureethylester, Propionsäuremethylester, sek. Butylacetat, 1,3-Dioxan, 1,3-Dioxolan, 2,4,5-Trimethyl-l,3-dioxolane, 2- Butylfuran, 2-Ethyl-2-methyl-l,3-dioxolan, 2-Ethyl-4- methyl-1,3-dioxolan, 2-Ethyl-5-methylfuran, 2- Ethylfuran, 5,6-Dihydro-2-methyl-2H-Pyran, 2- Methylfuran, 2-Propylfuran, 3-Methylfuran, Diethylether, Dimethylfuran, Methyl-1,3-Dioxan, Pentylfuran, Tetrahydrofuran, Trimethyldioxolan, 1,1,2,2- Tetrachloroethan, 1,1,2-Trichloroethan, 1,2-Dibromethan,

[0050] 1.2-Dichlorbenzol, 1,2-Dichlorethan, 1,2-Dichlorpropan,

[0051] 1.3-Dichlorbenzol, 1,4-Dichlorbenzol, Benzylchlorid, Chlorethan, Chlormethan, Chloroform, Dichlormethan, Tetrachlorethen, Trichlorfluormethan, Trichlorfluormethan, Vinylchlorid, 2,3-Butandion, 2,4- Dimethylpentan-3-on, 2-Methylhexan-3-one, 3,3-Dimethyl- 2-butanon, 3-Ethylcyclopentanone, 3-Heptanon, 4- Ethylcyclohexanon, 4-methylhexan-3-one, 6-Methylheptan- 2-one, Cyclohexanon, Cyclopentanon, 2-methyl- Cyclopentanone, 3-methyl-Cyclopentanone, Hydroxybutanon, 1,4-Pentadien, 2-Methyl-l-buten, 1,1~ Dimethylcyclopropan, 1,3-Butadien, 1-Nonen, 1-Octen, 1- Penten, 2,2,4-Trimethylpentan, 2,2-Dimethylbutan, 2,3- Dimethyloctan, 2,4-Hexadien, 2,6-Dimethyloctan, 2- Methyl-2-buten, 2-Methylbutan, 2-Methylhexan, 2- Methylpentan, 2-Nonen, 2-Octen, 3-Methyl-l-buten, 3- Methylhexan, 3-Methyloctan, 3-Methylpentan, 4- Methyloctan, 4-0cten, Butan, Buten, Cumol, Cyclohexan, Cyclopenten, trans-1,2-Dimethylcyclopropane, Decan, Dimethylocten, Heptan, Hexan, Isobutan, Methylcyclohexan, Methylcyclohexen,Methylcyclopentan, Naphthalin, n-Dodecan, Nonan, Nonen, n-Tetradecan, n- Tetradecan, n-Tridecan, n-Tridecan, Getan, Pentan, Propan, Propen, Tetramethylbenzol, Undecan, Decamethylcyclopentasiloxan, Decamethyltetrasiloxan, Dodecamethylcyclohexasiloxan, Dodecamethylpentasiloxan, Ethoxytrimethylsilan, Fluortrimethylsilan, Hexamethylcyclotrisiloxan, Hexamethyldisiloxan, Hydroxytrimethylsilan, Octamethylcyclotetrasiloxan, Octamethyltrisiloxan, 1-Ethyl-lH-pyrrole , Acetonitril, Isobuttersäure, Methylpropannitril, 1- (Methylthio)-1- propene, 2-Ethyl-5-methylthiazole, 2-Ethylthiophene, 2- Propylthiophen, 3-Pentanethiol, Dipropyldisulfid, Dipropyltrisulfid, Methylethyldisulfid, Methylpropyldisulfid, Methylthiirane, Methylthiopropane, 1- (Methylthio)-pentane, sec. Butylpropyldisulfid, 2,6- Dimethyl-2,6-octadien, 2,6-Dimethyl-4-octen, 2-Caren, 3,3,5-Trimethyl-l,5-heptadien, 3,6,6-Trimethylbicyclo- [3.1.1]-heptan-2-on, 3,7-Dimethyl-2,4-octadien, Alloaromadendren, α-Phellandren, α-Terpineol,α-Copaene, α-Cubebene, α-Gurjunene, α-Pinocarvone, α-Terpineol acetate, β-Elemene, Caran, Dihydromyrcene, Dihydroumbellulone, Isomenthol, Myrtanol, p,α,α-Trimethylbenzyl alcohol, p-Cymene, Phellandrene, Pinocamphone, p-Menth-3-ene, Terpinen-4-ol, α-Caryophyllene and γ-Cadinene.

[0052] Preferably, the methane-containing gas mixture in step b) is compressed to 6 to 24 bar (g), preferably 10 to 20 bar (g), and particularly preferably to 14 to 18 bar (g), since in these pressure ranges, the methane-containing gas can be processed particularly efficiently.

[0053] In a preferred embodiment, the methane-containing gas mixture in step b) is cooled to 0°C to 20°C, preferably to 2°C to 10°C, since at these temperature ranges the VOCs are efficiently absorbed by the absorbent.

[0054] Preferably, the VOC-laden absorbent from step d) is heated to 30°C to 90°C, particularly preferably to 50°C to 70°C, before transport to the desorption device. Heating the absorbent allows it to be regenerated more easily and efficiently in the desorption device.

[0055] In a preferred embodiment, the regenerated absorbent from step g) is cooled before being returned to the absorption device, preferably to 0°C to 20°C, particularly preferably to 2°C to 10°C.

[0056] In a preferred embodiment, in step c) the liquid VOC-reversibly absorbing absorbent of the absorption device is supplied with a mass flow of at least 6 kg / Bm 3 , preferably at least 7 kg / Bm 3 and particularly preferably at least 7.8 kg / Bm 3 Gas mixtures are fed in. The mass flow of at least 6 kg / Bm 3, preferably at least 7 kg / Bm 3 and particularly preferably at least 7.8 kg / Bm 3 Gas mixtures for the liquid VOC-reversibly absorbing absorbent allow even VOCs with a low boiling point (below 50°C) to be absorbed and thus removed from the gas mixture. For example, a volume flow of 7.8 kg of absorbent per operating cubic meter of gas mixture has been shown to be ideal for removing the VOC substance dimethyl sulfide, which has a boiling point of 37°C at standard pressure. The density of the absorbent in this embodiment is approximately 0.9 to 1.1 kg / l.

[0057] A further aspect of the invention relates to a device for processing methane-containing gas according to the method according to the invention. Said device comprises the following components: a gas source, a cooling device, a compressor, an absorption device with an upper end and a lower end, a desorption device with an upper end and a lower end, a separation device, a first connecting line connecting the lower end of the desorption device to the upper end of the absorption device, a second connecting line connecting the lower end of the absorption device to the upper end of the desorption device, a third connecting line connecting the upper end of the

[0058] Absorption device with the separation device, a fourth connecting line which connects the separation device with the lower end of the desorption device.

[0059] The invention is explained in more detail below using the accompanying exemplary embodiments. They show, purely schematically:

[0060] Fig. 1 is a schematic representation of a preferred embodiment of the process according to the invention for purifying methane-containing gas;

[0061] Fig. 2 the structure of an in silico simulation model;

[0062] Fig. 3 a step diagram for the VOC connection

[0063] Methyl mercaptan;

[0064] Fig. 4 a step diagram -for the VOC compound

[0065] Dimethyl sulfide;

[0066] Fig. 5 a step diagram for the VOC connection

[0067] Acetone;

[0068] Fig. 6 a step diagram for the VOC compound 2-butanone;

[0069] Fig. 7 a step diagram for the VOC compound 1-propanol;

[0070] Fig. 8 a step diagram for the VOC connection

[0071] Toluene;

[0072] Fig. 9 a step diagram for the VOC connection

[0073] limonene;

[0074] Fig. 10 shows a diagram of measured VOC concentrations in plants producing biogas from renewable resources; and

[0075] Fig. 11 shows a diagram of measured VOC concentrations in plants producing biogas from waste.

[0076] Fig. 12 the structure of an in silico simulation model.

[0077] In the preferred embodiment of the process according to the invention, schematically illustrated in Fig. 1, a methane-containing gas mixture is provided from a gas source 101 in a first step. The gas mixture 103 comprises CO2 and at least one compound from the group of volatile organic compounds (VOCs). The methane-containing gas mixture 103 is compressed in a compressor 105 to 14-18 bar (g) and subsequently cooled to 2-10 °C in a cooling device 107.

[0078] The methane-containing gas mixture 103 is then fed to an absorption device 109. The methane-containing gas mixture 103 is introduced at a lower end 111 of the absorption device 109 and rises upward to an upper end 113 of the absorption device 109.

[0079] The terms "top" and "bottom" refer to the orientation of the respective devices shown in the figures.

[0080] Furthermore, a liquid absorbent 117 is supplied to the absorption device 109 via a first connecting line 115, which opens into the absorption device 109 in the region of the upper end 113. This liquid absorbent 117 flows in droplet form from the upper end 113 to the lower end 111 of the absorption device 109 and comes into contact with the counterflowing methane-containing gas mixture 103. Through the contact of the absorbent 117 with the methane-containing gas mixture 103, the VOCs contained in the gas mixture are reversibly bound in the absorbent 117, whereby a methane-containing, VOC-reduced gas mixture 119 is obtained at the upper end 113 of the absorption device 109, while a VOC-laden absorbent 121 collects at the lower end 111 of the absorption device 109.The methane-containing, VOC-reduced gas mixture 119 is conveyed via a second connecting line 123 from the upper end 113 of the absorption device 109 to a separation device 125. The VOC-laden absorbent 121 is pumped via a third connecting line 127 from the lower end 111 of the absorption device 109 by means of a pump (not shown) to a heat exchanger device 129, where it is heated to 50-70°C. The VOC-laden absorbent 121 is then pumped further to an upper end 133 of a desorption device 135 and fed to the desorption device 135. In the separation device 125, the methane-containing, VOC-reduced gas mixture 119 is separated into a pressure-reduced, CO2-enriched gas stream 137 (pressure -0.5 to +0.5 bar (g)) and an isobaric methane-enriched gas stream 139 (pressure 14 - 18 bar (g)).The CO2-enriched gas stream 137 is then introduced via a fourth connecting line 143 at a lower end 141 of the desorption device 135 and rises to the upper end 133 of the desorption device 135. As the liquid VOC-laden absorbent 121 flows in droplet form from the upper end 133 to the lower end 141 of the desorption device 135, it comes into contact with the counterflowing CO2-enriched gas stream 137. By heating the liquid VOC-laden absorbent 121, the bound VOCs are reversibly dissolved and flow with the CO2-enriched gas stream 137 to the upper end 133 of the desorption device 135. This creates a purified absorbent 145, which collects at the lower end 141 of the desorption device 135.Through a fifth connecting line 147, the purified absorbent 145 is conveyed by a pump (not shown) to the heat exchanger device 129, where it is cooled to 2-10°C and then pumped via the supply line 115 to the upper end 113 of the absorption device 109. The heat exchanger device 129 can comprise several separate heat exchangers 131, 131', 131''. At the upper end 133 of the desorption device 135, a gas stream 149 enriched with CO2 and VOC is discharged and fed to a regenerative post-combustion device 151 to reduce the environmental impact of the process.

[0081] For the use of methane-containing gases as a natural gas substitute, sulphur-containing components in the product gas must be below a limit of 6 mg / m 3 Sulfur equivalent. The limit value is listed, for example, in the DVGW standard G260.

[0082] For other VOCs, for example, there are limits for the use of gas permeation membranes. In these cases, a total VOC concentration of less than 10 ppm must be maintained to meet the conditions of use of Evonik (manufacturer of a gas permeation membrane).

[0083] Another reason for discussion about limiting VOCs in biogas is the foreign odors that can be caused by VOCs. Figure 2 shows an in silico simulation model of a preferred embodiment of the process according to the invention. The simulation model comprises an absorption device 201 and a desorption device 203. The absorption medium—here PEG—enters the absorption device 201 as a liquid 205. The absorption medium leaves the absorption device 201 as a VOC-laden liquid 207 and is heated in a heat exchanger 209. The heated, VOC-laden absorption medium 211 thus obtained is transported from the heat exchanger 209 to another heat exchanger 213 and further heated there. External heat 215 is supplied to the heat exchanger 213. A strongly heated, VOC-laden absorption medium 217 leaves the heat exchanger 213 and is expanded in a control valve 219.The heated, expanded, VOC-laden absorbent 221 enters the desorption device 203, where it releases the VOCs. The largely regenerated, heated, expanded absorbent 223 is compressed by a pump 225 and transported as a compressed, heated, largely regenerated absorbent 227 to the heat exchanger 209. In the heat exchanger 209, it transfers some of its heat to the VOC-laden absorbent 207. The cooler, compressed, largely regenerated absorbent 229 is then transported to another heat exchanger 231 and further cooled therein. For this purpose, external cooling 233 is supplied to the heat exchanger 231. The cooled, compressed, largely regenerated absorbent 205 reenters the absorption device 201, thus closing the absorbent cycle.A compressed biogas 235 to be purified is cooled in a heat exchanger 237 using external refrigeration 239 and then freed of condensate in a condensate separator 241. The resulting cooled, compressed biogas 243 is fed to the absorption device 201, where it comes into contact with the cooled, compressed, largely regenerated absorbent 205, releasing its VOCs to the absorbent 205. A purified biogas 245 exits the absorption device 201 and can subsequently be used for further processes 247. A regeneration gas 249, for example, a lean gas from the biogas treatment 251, is fed to a heat exchanger 253 and heated therein. A heated regeneration gas 255 enters the desorption device 203 and detaches the VOC from the heated, expanded, VOC-laden absorbent 221.A VOC-laden regeneration gas 257 then exits the desorption device 203 and transfers its heat to the regeneration gas 249 in the heat exchanger 253. A cooled, VOC-laden regeneration gas 259 is conveyed to a post-treatment unit 263 by means of a suction fan 261.

[0084] In the computer simulation described above, the solubility of a specific VOC compound in the absorption medium, in this case PEG, was simulated using Henry's law. In a first step, the equilibrium line is constructed at which the gas phase and the liquid phase are in equilibrium; the slope of the equilibrium line corresponds to the Henry's law coefficient of the compound at the respective temperature. In a second step, the balance line is constructed, which results from the mass balance of the VOC compound in the absorption device. The starting point of the balance line is at the VOC concentration at the upper end of the absorption device (purified biogas 245) and the concentration of the liquid phase at the upper end of the absorption device (regenerated PEG 205).The end point of the balance line is determined by the gas phase concentration at the lower end of the absorption device (VOC-laden biogas 243) and the liquid phase concentration at the lower end of the absorption device (VOC-laden PEG 207). The start and end points of the balance line are connected by a straight line (balance line). This only applies under the assumption that a constant temperature exists in the absorption device. With a temperature gradient, both the balance line and the equilibrium line would be represented as a balance curve and an equilibrium curve. A stage construction can be drawn between the balance line and the equilibrium line. Each stage represents a theoretical plate of the column. The number of stages is a measure of the required height of the absorption device. With absorption, the balance line always lies above the equilibrium line.If the balance line is below the equilibrium line, then desorption is occurring.

[0085] Figure 3a shows an analogous step diagram for the VOC compound methyl mercaptan (CAS 74-93-1) and PEG as the absorption agent in the absorption device. The balance line (dashed line) is positioned above the equilibrium line (dash-dotted line), and the step structure (solid line) is shown in between. Figure 3b shows a step diagram analogous to the one described above for the VOC compound methyl mercaptan (CAS 74-93-1) and PEG as the absorption agent in the desorption device. The equilibrium line (dash-dotted line) is positioned above the balance line (dashed line), and the step structure (solid line) is shown in between. Figure 3a shows that a step structure is not practical for methyl mercaptan, since a large residue of methyl mercaptan remains in the purified biogas if the flow of absorption agent was too small (in the simulation model).Figure 3b shows that the absorbent in the desorption device is almost completely regenerated by methyl mercaptan.

[0086] Figures 4a and 4b show a step diagram analogous to the step diagrams described above for the VOC compound dimethyl sulfide (CAS 75-18-3) and PEG as absorbent in the absorption device (Figure 4a) and in the desorption device (Figure 4b). Figure 4a shows that several steps are necessary to purify the biogas, yet a residue of dimethyl sulfide remains in the biogas. Figure 4b shows that the absorbent in the desorption device is almost completely regenerated by dimethyl sulfide.

[0087] Figures 5a and 5b show, analogous to the stage diagrams described above, the same ones for the VOC compound acetone (CAS 67-64-1) and PEG as absorbent in the absorption device (Figure 5a) and in the desorption device (Figure 5b). Figure 5a shows that several stages are necessary to purify the biogas, yet a very small residue of acetone remains in the biogas. Figure 5b shows that the absorbent in the desorption device is almost completely regenerated by acetone.

[0088] Figures 6a and 6b show, analogous to the stage diagrams described above, the same ones for the VOC compound 2-butanone (GAS 78-93-3) and PEG as absorbent in the absorption device (Figure 6a) and in the desorption device (Figure 6b). Figure 6a shows that only a few stages are required to purify the biogas, and no residue of 2-butanone remains in the biogas. Figure 6b shows that the absorbent in the desorption device is regenerated by means of multiple stages of 2-butanone, but a small portion of 2-butanone remains in the regenerated absorbent.

[0089] Figures 7a and 7b show, analogous to the diagrams described above, stage diagrams for the VOC compound 1-propanol (GAS 71-23-8) and PEG as absorbent in the absorption device (Figure 7a) and in the desorption device (Figure 7b). Figure 7a shows that only a few stages are required to purify the biogas, and a very small residue of 1-propanol remains in the biogas. Figure 7b shows that, despite several stages, the absorbent in the desorption device is not completely regenerated from 1-propanol.

[0090] Figures 8a and 8b show stage diagrams analogous to the diagrams described above for the VOC compound toluene (GAS 108-88-3) and PEG as absorbent in the absorption device (Figure 8a) and in the desorption device (Figure 8b). Figure 8a shows that only a few stages are necessary to purify the biogas, but a residue of toluene remains in the biogas because it was incompletely regenerated. Figure 8b shows that, despite several stages, the absorbent in the desorption device is not completely regenerated from toluene. Since the balance line and the equilibrium line run parallel, complete regeneration is not possible.

[0091] Figures 9a and 9b show analogous stage diagrams for the VOC compound limonene (GAS 7705-14-8) and PEG as absorbent in the absorption device (Figure 9a) and in the desorption device (Figure 9b). Figure 9a shows that only a few stages are required to purify the biogas, but a residue of limonene remains in the biogas because it was incompletely regenerated. Figure 9b shows that, despite several stages, the absorbent in the desorption device is not completely regenerated from limonene because the material flow of the absorbent is too high (in the simulation model).

[0092] Based on the simulation shown in Figures 2 to 9, it can be determined that VOCs with a boiling point between 35°C and 100°C can be almost completely removed from the biogas in the absorption device and almost completely removed from the absorbent in the desorption device. VOCs with a boiling point higher than 100°C are almost completely removed from the biogas. However, the regeneration of the absorbent is incomplete. VOCs with a boiling point below 35°C are incompletely removed from the biogas. The gas components CO2 and methane remain almost entirely in the gas phase.

[0093] Figure 10 shows a graph based on 48 VOC measurements in biogas samples produced from renewable raw materials (NaWaRo). The VOC concentration in the biogas ranges from 5 to 20 ppm. Some values ​​are higher. VOCs in biogas from renewable raw materials do not pose any problems during further processing.

[0094] Figure 11 shows a graph based on 138 VOC measurements in biogas samples produced from waste. The VOC concentration in the biogas ranged from 10 to 250 ppm. Higher concentrations were also achieved in numerous cases. VOCs in waste-derived biogas often cause problems during further processing, so targeted VOC removal is necessary.

[0095] Experimental data

[0096] Figure 12 shows the in silico simulation model of the preferred embodiment of the inventive method described in Figure 2. Various parameters for the biogas, absorbent, and regeneration gas were added to the simulation model to demonstrate the amount of CO2 and VOC absorbed. The simulation model comprises three gas streams at different stages. A compressed methane-containing gas BG1 is fed to a heat exchanger 1201 and leaves it as a cooled, compressed methane-containing gas BG2. The methane-containing gas BG2 is fed to an absorption device 1203, where the CO2 and VOC components present in the methane-containing gas BG2 are absorbed. A CO2- and VOC-reduced methane-containing gas BG3 leaves the absorption device 1203. In the absorption device 1203, the methane-containing gas BG2 comes into contact with a cooled, regenerated absorbent ABI.The cooled, regenerated absorbent AB1 absorbs CO2 and VOC in the absorption device 1203 and leaves the absorption device 1203 as absorbent AB2 loaded with CO2 and VOC. In a heat exchanger 1205, the absorbent AB2 loaded with CO2 and VOC is heated and leaves this as heated absorbent AB3 loaded with CO2 and VOC. In a further heat exchanger 1207, the heated absorbent AB3 loaded with CO2 and VOC is further heated and leaves this as heated absorbent AB4 loaded with CO2 and VOC. The heated absorbent AB4 loaded with CO2 and VOC is fed to a control valve 1209 and expanded and leaves this as heated, expanded absorbent AB5 loaded with CO2 and VOC. The heated, expanded absorbent AB5 loaded with CO2 and VOC is fed to a desorption device 1211.

[0097] A regeneration gas RG1 is heated in a heat exchanger 1213 and leaves it as heated regeneration gas RG2. The regeneration gas RG1 is a gas stream with CO2 as its main component. The heated regeneration gas RG2 is fed to the desorption device 1211, where it comes into contact with the heated, expanded absorption medium AB5 loaded with CO2 and VOC. The heated regeneration gas RG2 dissolves CO2 and VOC from the absorption medium AB5, yielding a regeneration gas RG3 loaded with CO2 and VOC and a largely regenerated, heated, expanded absorption medium AB6. The largely regenerated, heated, expanded absorption medium AB6 is compressed in a pump 1215 and fed to the heat exchanger 1205 as compressed, heated, largely regenerated absorption medium AB7.In heat exchanger 1205, the compressed, heated, largely regenerated absorption medium AB7 transfers its heat to the CO2- and VOC-laden absorption medium AB2 and leaves heat exchanger 1205 as a cool, compressed, largely regenerated absorption medium AB8. The cool, compressed, largely regenerated absorption medium AB8 is fed to a heat exchanger 1217, cooled, and leaves it as a cooled, regenerated absorption medium AB1. The CO2- and VOC-laden regeneration gas RG3 is fed to heat exchanger 1213, transfers its heat to the regeneration gas RG1, and leaves heat exchanger 1213 as a cooled CO2- and VOC-laden regeneration gas RG4. The cooled CO2 and VOC-laden regeneration gas RG4 is conveyed in a suction fan 1219 as cooled CO2 and VOC-laden regeneration gas RG5 to a post-treatment unit 1221.

[0098] Table 1 below shows parameters for the simulation model using the PEG1843 absorbent. This absorbent absorbs only 2.5 kg / h of methane (0.4%), while absorbing 36.6 kg / h of CO2 (3.6%) and over 98% of VOCs (dimethyl sulfide (DMS), acetone, 2-butanone, and terpene). It should be noted that low-boiling point VOCs such as DMS (boiling point 37°C), medium-boiling point VOCs such as acetone (boiling point 56°C) and 2-butanone (boiling point 79.6°C), as well as high-boiling point VOCs such as terpenes (boiling point 140-230°C) are absorbed.

[0099] This is evident from the mass differences between BG2 and BG3. The 36.6 kg / h of CO2 and VOCs are released from the methane-containing gas BG2 to the absorbent ABI, which is evident in the increase in CO2 and VOC concentrations from ABI to AB5. The VOC- and CO2-laden absorbent then transfers the 36.6 kg / h of CO2 and VOCs to the regeneration gas RG1, which is evident in the increase in CO2 and VOC concentrations from RG1 to RG3.

[0100] Table 1

[0101] Tables 2 to 4 show similar parameter configurations as Table 1 and differ from Table 1 only in that the temperature of the regeneration gases RG1 and RG3 and the absorbent AB5 as well as the mass flow of RG1, RG3, AB1 and AB5 were changed.

[0102] Tables 5 to 8 show the same parameter configurations as Tables 1 to 4, except that the absorbent in the simulation model was changed from PEG1843 (Tables 1 - 4) to PEG300 (Tables 5 - 8).

[0103] Table 2

[0104] Table 3 Table 4

[0105] Table 5 Table 6 Table 7

[0106] Table 8 For all parameter configurations in the simulation model, it is evident that only approximately 3.6 vol.% of the CO2 present in BG1 is absorbed by the absorbent. It should be noted that in Tables 2 and 6, the terpene concentrations in ABI and AB5 are higher than in Tables 1, 3-5, and 7-8. In all

[0107] The terpenes could not be completely removed from the absorbent under these parameter configurations (see ABI). Surprisingly, the terpenes present in the methane-containing biogas BG2 can nevertheless be largely removed from it, see BG3.

Claims

Claims 1. A process for processing methane-containing gas comprising the steps of: a) providing a methane-containing gas mixture (103) comprising 20-60 vol% CO2 and at least one compound from the group of volatile organic compounds (VOCs), wherein the at least one VOC compound is selected from the group consisting of ketones, sulfur-containing hydrocarbons and terpenes, wherein the concentration of the VOC compound in the gas mixture is 10-10,000 ppm; b) compressing and cooling the methane-containing gas mixture (103) from step a); c) feeding the compressed, cooled methane-containing gas mixture to a Absorption device (109), wherein the absorption device (109) comprises a liquid VOC-reversibly absorbing absorbent (117); d) absorption of at least a part of the VOC compound and a maximum of 5 vol% of the CO2 by the absorbent (117), resulting in a methane-containing, VOC- and CO2-reduced gas mixture (119) and a VOC- and CO2-loaded absorbent (121); e) supply of the VOC- and CO2-loaded absorbent (121) from the Absorption device (109) for a Desorption device (135); f) Feeding the methane-containing, VOC and CO2-reduced gas mixture (119) from the absorption device (109) to a separation device (125) comprising a membrane, in which the methane-containing, VOC and CO2-reduced gas mixture (119) is separated into a pressure-reduced, CO2-enriched gas stream (137) and an isobaric, methane-enriched gas stream (139); g) supplying a regeneration gas stream (138) comprising at least a part of the CO2-enriched gas stream (137) from step f) to the desorption device (135) for regeneration of the VOC and CO2-loaded absorbent (121), whereby an exhaust gas stream (149) containing CO2 and the VOC compound as well as an at least partially regenerated absorbent (145) is obtained; h) Discharge of the exhaust gas stream (149) from the desorption device (135) and return the at least partially regenerated absorption medium (145) from the desorption device (135) to the absorption device (109).

2. Method according to claim 1, characterized in that in step h) the exhaust gas stream (149) of a regenerative The afterburning device (151) is supplied for oxidation.

3. Method according to one of claims 1 or 2, characterized in that at least steps c) to h) are carried out continuously.

4. A method according to one of claims 1 to 3, characterized in that in step c) in the Absorption device: 2 to 10 liters of absorbent per cubic meter 3 The methane-containing gas mixture from step b) can be used.

5. Method according to any one of claims 1 to 4, characterized in that in step g) 1 to 3 liters of VOC-loaded absorbent from step d) is added to the desorption device with 1 Bm 3 CO2-enriched gas from step f) is regenerated.

6. Method according to any one of claims 1 to 5, characterized in that the VOC-absorbing absorbent (117, 145) has a boiling point of more than 250°C at 1013.25 mbar and comprises a compound selected from the group consisting of polyethylene glycol (PEG), mineral oil, esters or combinations thereof, preferably polyethylene glycol.

7. Method according to any one of claims 1 to 6, characterized in that the VOC-absorbing absorbent (117, 145) comprises a compound according to formula (I): I) R1-O-(CH2CH2O) n -R2, where n = 3 to 11 and R1 and R2 are independently selected linear C1- C 10 Alkyls are.

8. Method according to any one of claims 1 to 7, characterized in that the VOC compound has a vapor pressure of at least 0.1 mbar at 20 °C and / or a boiling point of at most 240 °C at 1013.25 mbar.

9. Method according to any one of claims 1 to 8, characterized in that the at least one VOC compound is selected from the group consisting of acetone, 2-butanone, 3-methyl-2-butanone, 2-pentanone, 3-pentanone, 3,3-dimethyl-2-butanone, 2-methyl-3-pentanone, 4-methyl-2-pentanone, 3-methyl-2-pentanone, 3-hexanone, 2-hexanone, 5-methyl-3-hexanone, 3-methyl-2-hexanone, 2-heptanone, 4-Octanone, 3-Octanone, 2-Octanone, 2,9-Decanedione, α- Thujen, α-Pinen, Camphen, Sabinen, ß-Pinen, Myrcen, 3-Caren, Thujanon, Thujopsen, Thymol, α-Terpinen, ß-Caryophyllen, 1,4-Cineol, Eucalyptol, Fenchon, y- Terpinen, Terpinoien, Limonen, Tricyclen, Linalool, Menthon, Nopinon, p-Menthan-2-on, p-Menthan-2-ol, Campher, Carvomenthon, 3,3-Dimethyl-2-bornanon, Carbonylsulfid, Methylmercaptan, Ethylmercaptan, Dimethylsulfid, Kohlenstoffdisulfid, 2-Propanthiol, 2-Methyl-2-propanthiol, 1-Propanthiol, Thiophen, 2- Butanthiol, Isobutylmercaptan, Methyl-Allyl-Sulfid, Methylpropylsulfid, Butanthiol, Dimethyldisulfid, 2-MethyIthiophen, 3-MethyIthiophen, Tetrahydrothiophen, 1-Pentanthiol, Thiophenol, Dimethyltrisulfid, Diisopropyldisulfid, Dimethyl tetrasulfide, methyl propyl disulfide, and methyl isopropyl disulfide. A process according to any one of claims 1 to 9, characterized in that the methane-containing gas mixture (103) is compressed in step b) to 6 to 24 bar (g), preferably 10 to 20 bar (g), and particularly preferably to 14 to 18 bar (g). A process according to any one of claims 1 to 9, characterized in that the methane-containing gas mixture (103) is cooled in step b) to 0°C to 20°C, preferably to 2°C to 10°C. A process according to any one of claims 1 to 10, characterized by the fact that the VOC-laden The absorbent (121) from step d) is heated before being transported to the desorption device (135), preferably to 30°C to 90°C, particularly preferably to 50°C to 70°C. A method according to any one of claims 1 to 11, characterized in that the regenerated absorbent (145) from step g) is cooled before being returned to the absorption device (109), preferably to 0°C to 20°C, particularly preferably to 2°C to 10°C. A method according to any one of claims 1 to 13, characterized in that in step c) the liquid VOC-reversibly absorbent (117) of the absorption device (109) is supplied with a volume flow rate of at least 7.8 kg / m³. 3Gas mixture (103) is supplied. Device (100) for processing methane-containing gas (103) according to the method of any one of claims 1 to 14, comprising a gas source (101), a cooling device (107), a compressor (105), an absorption device (109) with an upper end (113) and a lower end (111), a desorption device (135) with an upper end (133) and a lower end (141), a separation device (125) comprising a membrane, a first connecting line (115, 147) which connects the lower end (141) of the desorption device (135) to the upper end (113) of the absorption device (109), a second connecting line (127) which connects the lower end (111) of the absorption device (109) to the upper end (133) of the desorption device (135), a third connecting line (123) which connects the upper end of the absorption device (109) to the separation device (125), and a fourth connecting line (143) which connects the separation device (125) to the lower end (141) of the desorption device (135).

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