EP4284535A1 - Method for removing co2 from a methane-containing gas - Google Patents

Abstract

The invention relates to a method for removing CO₂ from a methane-containing gas, having the steps of providing a methane-containing gas (103) containing at least CO₂ as an impurity, cooling the gas (103) in order to separate CO₂ from the methane-containing gas (103) by freezing out same, and additionally reducing the CO₂ concentration of the gas (103) using a PTSA (111), whereby a methane-enriched product gas (117) is obtained. At least a part (127) of the product gas (117) is then conducted through the PTSA (111) as a preparation gas (129), whereby CO₂ is absorbed by the preparation gas (129) and is removed from the PTSA (111) as a CO₂-enriched preparation gas (133). The preparation gas (133) conducted through the PTSA (111) is then mixed with the methane-containing gas (103).

Description

Process for removing CO2 from a methane-containing gas

The invention relates to a method and a device for removing CO2 from a methane-containing gas.

Due to global warming, CCh-neutral energy sources are becoming increasingly important for today's society. A popular method of obtaining such an energy carrier is the fermentation of food waste in fermenters to produce biogas. Since foods such as fruit or vegetables bind CO2 from the atmosphere during growth, the biogas produced during the fermentation of these foods and the methane it contains are climate-neutral.

In addition to methane, biogas usually also contains various impurities, sometimes significant amounts of CO2. Since CO2 is non-flammable, its presence in the biogas prevents the methane from being burned efficiently and lowers the energy density of the biogas. For this reason, biogas produced by fermentation is usually cleaned to increase the methane content. The methane-enriched product gas obtained after purification - often also called biomethane - can either be used directly for the purpose of generating energy, fed into the gas network or liquefied with a view to intermediate storage or transport.

For liquefaction, the product gas is usually cooled down considerably. In this process, impurities contained in the product gas, in particular CO2, have a disadvantageous effect: if the product gas contains a significant CCh concentration, it freezes in the course of the Cooling necessary for liquefaction and can block valves in the liquefaction plant, for example. In this respect, the lowest possible CCh concentration in the product gas is not only important with regard to its use as an energy source, but also with regard to its liquefaction for storage or. desirable for transportation. It has been shown that in the case of liquefaction, a CCh concentration in the product gas of below 215 ppm is ideal. However, such low CCh concentrations can only be achieved with the known methods - if at all - by using time-consuming and costly purification processes.

For the distance or Reduction of CO2 from biogas are various separation processes and separation devices, such as amine scrubbing, pressure swing adsorption ("Pressure Swing Adsorption" - in short: "PSA"), pressure-temperature swing adsorption ("Pressure Thermal Swing Adsorption" - in short: " PTSA" ) or membranes. Many of these processes have the disadvantage that the separating devices involved (membranes, adsorbers, filters) have to be reprocessed or regenerated or replaced at great expense, since their separating performance decreases steadily without regeneration. In addition, there are often multi-stage processes - i.e. cascaded separators or separation steps - are necessary to achieve a significant CO2 reduction in the product gas Each separation stage is usually associated with additional cost and loss of product gas (the so-called "methane slip" ) These problems are common in today's Procedure still present.

US 2019/0001263 Al, for example, describes a method for producing biomethane in which the gas mixture to be cleaned is compressed in a first step and In a second step, gaseous impurities (volatile organic compounds - VOC) are removed from the gas mixture by means of a PSA. Then, in a third step, part of the CO2 and oxygen are separated from the gas mixture by means of a membrane. Further CCh reduction is achieved in a fourth step using PTSA, while residual oxygen and nitrogen are removed by cryogenic separation in a fifth step. At the end of this complex process, a methane-enriched, cleaned product gas or obtained biomethane. For the regeneration of the PTSA, a methane-containing regeneration gas is passed through the PTSA in a known manner, which is then fed to a downstream recovery plant for methane recovery. Despite the complex and cost-intensive cleaning steps, the CCh reduction achieved by means of this process is insufficient with regard to efficient liquefaction of the product gas. Another disadvantage is that in the course of the various processing steps, part of the biomethane contained in the gas mixture is lost (methane slip), which reduces the efficiency of the process in terms of the highest possible biomethane yield.

WO 2016/126159 A2 discloses a system for processing methane-containing gas with a methane content of at least 50 vol. % and includes a compression unit and a pre-treatment unit with a membrane separator to reduce the CO2 content to below 2 vol. % and increasing the methane content to over 85 vol. % . The system also includes a liquefaction unit and a decanting device with a container in which a flash gas is generated. US 5062270 discloses a process for starting up a distillation column with a controlled freezing zone, in which process a CO2-enriched gas stream is produced - with a preferred CCh content of 60% - 85%.

The methods in the prior art have the disadvantage that the CO 2 content of the methane-containing gas cannot be reduced enough without a considerable part of the methane also being lost.

The present invention therefore has the task of eliminating the above-described disadvantages of the prior art and providing an improved method for removing CO2 from a methane-containing gas mixture that efficiently and effectively reduces the CCh content while minimizing the methane slip allowed.

The object is achieved according to the invention with a method according to claim 1 and a device according to claim 17 . Preferred embodiments of the invention are set out in the dependent claims.

In the process according to the invention, a methane-containing gas containing at least CO 2 as an impurity is provided in a first step (step a).

In a second step, CO2 is separated from the gas by freezing (step b). For this purpose, the methane-containing gas is cooled, preferably to or under -78 . 5 °C at atmospheric pressure.

Then, in a third step, the CO2 concentration of the methane-containing gas is measured in a pressure and Temperature swing adsorption (English: presure temperature swing adsorption (PTSA)) further reduced, whereby a methane-enriched product gas is obtained (step c).

In a fourth step, at least part of the product gas is used as treatment gas for treatment or Regeneration of the PTSA passed through the PTSA, whereby CO2 is picked up by the treatment gas and removed with the latter from the PTSA (step d).

In a fifth step, the treatment gas loaded with CO2 in the course of the treatment of the PTSA is mixed with the methane-containing gas from the first step a) (step e).

Within the meaning of the invention, a gas containing methane is defined as a methane-containing gas. In addition to methane, the methane-containing gas also includes CO2 and usually also other compounds, in particular impurities such as e.g. B. "volatile organic compounds" (VOC) .

Within the meaning of the invention, a methane-enriched product gas is defined as a gas which has a higher methane concentration and a lower CCh concentration than the initially provided methane-containing gas.

In the context of the invention, a treatment gas is defined as a gas which is separated from the product gas or from a gas based on the product gas and is passed through the PTSA for treatment of the PTSA. The conditioning gas may be altered in temperature and/or pressure prior to passage through the PTSA are, in particular, it can be previously heated and / or relaxed.

For the purposes of the invention, freezing off is understood as meaning a process in which the temperature of a gas is cooled below the pressure-dependent sublimation point of CO2. At atmospheric pressure, this is -78. 5ºC.

Surprisingly, it was found that the energy consumption of the PTSA can be reduced by using product gas as the treatment gas for the treatment of the PTSA. Specifically, it can be avoided that an external gas has to be used to prepare the PTSA.

It was also surprisingly found that the efficiency of the process can be increased by recycling the treatment gas and adding it to the initially provided methane-containing gas, since the freezing step allows a large part of the CO2 to be reliably and efficiently separated from the gas . At the same time, the methane slip when it freezes out is very low. The recirculation of the regeneration gas loaded with CCh into the methane-containing gas provided in step a) before the freezing step b) relieves the PTSA in step c). Overall, the number of separation steps or Separation stages in step c) are reduced and the methane slip of the process is minimized.

The method according to the invention thus has the advantage over the prior art that the upstream freezing step in combination with the use and recycling of the treatment gas to or after the preparation of the PTSA, the latter much cheaper, can be operated in a more energy-efficient and environmentally friendly manner.

The methane-containing gas initially provided in step a) can sometimes be produced by fermentation, for example in biogas plants, and preferably comprises biogas, landfill gas and/or gas from the pyrolysis of organic material. More preferably, the gas can also be of non-fermentative origin, for example in the form of natural gas, mine gas or coal bed methane. The gas containing methane can also be provided by an upstream gas treatment plant.

As mentioned above, a methane-enriched product gas is provided by reducing the CCh content and the associated increase in the methane content of the methane-containing gas. At least part of the latter is passed through the PTSA as a treatment gas in order to regenerate the PTSA.

The product gas or at least part of it is preferably liquefied before the treatment gas is separated off. The product gas can be liquefied in a known manner by cooling and/or compression. Since increasing the pressure of the cold product gas is very complex, the product gas is preferably liquefied by reducing the temperature. The product gas is preferably cooled to −140° C. to −100° C., preferably −130° C. to −110° C. and particularly preferably −125° C. to −115° C. for liquefaction. These temperatures are preferred in combination with a pressure of 15 bar. The 15 bar corresponds to the preferred pressure of the product gas when it is received after the CCh separation in the PTSA. Liquefied product gas with a high proportion of methane can be produced almost without pressure at approx. - 160 °C can be stored. It is also possible to store the liquefied product gas at elevated pressure and higher temperature.

After liquefaction, the liquefied methane-enriched product gas can be a simplified storage to be decompressed. In a preferred embodiment, the liquefied methane-enriched product gas is decompressed to preferably 1 bar—before part of the product gas is branched off for use as treatment gas. Due to the decompression of the liquefied product gas, the refrigeration requirement of the system is reduced accordingly and the subsequent storage and transport containers are not exposed to high pressures.

The decompressed, liquefied product gas preferably passes through a particle filter, which particularly preferably has a pore size of <10 μm and which removes solids from the decompressed, liquefied product gas. The removal of residues from the preferably decompressed liquefied product gas increases its quality with regard to its use as an energy carrier and prevents the solids from settling in transport containers or valves and causing deposits there.

During decompression, at least part of the liquefied product gas also becomes gaseous again. This part is referred to as "flash gas" within the meaning of the invention. The flash gas is therefore preferably cooled methane-enriched product gas, which is preferably Atmospheric pressure (usually approx. 1 bar) is present. In the context of the invention, this flash gas can be passed through the PTSA as a treatment gas or as part of the treatment gas for the treatment of the latter.

For the process according to the invention, at least part of the flash gas produced during the decompression of the liquefied product gas is preferably used as treatment gas in order to particularly increase the efficiency of the process. However, it is also conceivable that the processing gas is separated from the product gas directly before the liquefaction, ie without prior liquefaction and decompression with the associated receipt of a flash gas.

According to the invention, in the course of the processing of the PTSA, CO 2 is removed from the PTSA by means of the processing gas. In the context of the present application, the regeneration or processing of the PTSA includes the removal of CO2. The need for processing Regeneration of the PTSA results from the fact that the CO2 removed or separated from the methane-containing gas by means of the PTSA usually accumulates in the PTSA. In the PTSA, the methane-containing gas is separated in flow direction by an adsorbent or passed to an adsorber, where the adsorbent adsorbs the CO2 and the methane-enriched product gas accumulates on the other (downstream) side of the adsorbent. When the adsorber is saturated with CO2, the adsorbed CO2 has to be released from the adsorber to prepare it for further use, i. H . to regenerate . Several possibilities are known for regeneration. Usually For this purpose, either the pressure in the PTSA can be reduced, the adsorbent can be heated and/or the adsorbent can be flowed through by a treatment gas in or against the flow direction of the gas to be cleaned. Combinations of the regeneration steps mentioned are also possible. Such a regeneration process of a PTSA usually takes place at regular intervals. In practice, this means that the PTSA can either have several adsorbers or adsorber tanks, which adsorb alternately and are then regenerated, or that the PTSA is not constantly in operation and the separation process is paused during the regeneration time of the adsorber.

The treatment gas is particularly preferably expanded—ie decompressed—and optionally heated before it is passed through the PTSA, since this promotes the release of CO 2 into the treatment gas.

Within the meaning of the invention, a heated treatment gas is defined as a treatment gas which preferably has a temperature of -20° C. to 30° C., more preferably from -10° C. to 20° C. and particularly preferably from -5° C. to 15° C. and quite particularly preferably from 0° C. to 10° C. in order to detach the CO2 from the adsorber as efficiently as possible.

In a specific preferred embodiment of the method according to the invention, the PTSA comprises an adsorber through which the preferably heated processing gas flows in or counter to the flow direction of the methane-containing gas after the pressure in the PTSA has been reduced to the pressure of the processing gas. The heated treatment gas releases the adsorbed CO2 from the adsorber, which is thus regenerated. The treatment gas, which is now loaded with CO2, is then routed out of the PTSA, which means that the latter is again ready for the methane-containing gas to flow through in the direction of flow and to remove CO2 from the methane-containing gas by means of the regenerated adsorber.

As mentioned above, the treatment gas is recycled according to the invention after regeneration of the PTSA has taken place and is mixed with or combined with the methane-containing gas stream from the first step a) of the method according to the invention. Depending on the pressure of the methane-containing gas, the make-up gas is preferably increased or decreased to the same pressure by using a compressor to allow efficient mixing of the two gas streams. As a rule, one third of its volume (measured as the volume of methane-containing gas supplied per second) is preferably added to the methane-containing gas in step a) as treatment gas. According to the invention, in a second step b) the removal of CO2 from the methane-containing gas—which contains the recirculated processing gas—is carried out by freezing out CO2.

In the course of freezing, the methane-containing gas is preferably at a pressure of 5 to 25 bar, particularly preferably 10 to 20 bar and very particularly preferably 14 to 17 bar (the "bar" specification here is always bar (a), i.e absolute, given) to -130°C to -80°C, more preferably -120°C to -100°C, most preferably -116°C to -110°C. In a preferred embodiment, the methane-containing gas is brought into contact with a surface for cooling, which is cooled down to the temperature ranges mentioned above or has been . The CO2 contained in the methane - containing gas crystallizes out on this surface , so that a layer of solid CO2 -- also known as dry ice -- is formed on the surface . The dry ice is usually removed from the surface at regular intervals, for example by scraping it off with a scraper, so that new CO2 can crystallize out on the cooled surface.

The freezing step preferably reduces the CO2 content of the methane-containing gas (including the added processing gas) to below 6000 ppm. A further reduction in the CO2 content of the methane-containing gas is achieved according to the invention in the downstream PTSA. Freezing out CO2 generally has the advantage that a large amount of CO2 can be removed from the gas with relatively little effort. As a rule, the maintenance effort of a corresponding freezing unit (cooling unit) is also lower compared to other separating devices, such as a PTSA. In addition to CO2, other contaminants can also be removed from the methane-containing gas in the course of freezing. A further advantage is that no methane is lost in the freezing process since methane does not condense on the surface at the preferred temperatures given above. By freezing out CO2, the methane concentration in the methane-containing gas can be increased without methane loss. Depending on whether and in what concentration other impurities condense on the surface together with the CO2, the frozen CO2 can then be released into the environment or used as dry ice for cooling.

In the PTSA, the CO 2 concentration of the methane-containing gas is preferably below 5200 ppm, preferably below 830 ppm, more preferably below 215 ppm, particularly preferably below 100 ppm and very particularly preferably below 50 ppm.

A low CCk concentration in the product gas is preferred, particularly with regard to liquefaction of the product gas, since this prevents CO 2 from freezing out in valves or pipelines. A maximum CCh concentration of 50 ppm at atmospheric pressure is particularly preferred for the product gas, since CO 2 in these concentrations remains dissolved in the liquefied product gas at temperatures below −162° C. and does not crystallize out. If the pressure in the product gas is higher than atmospheric pressure, the CCh concentration can also be higher.

A low CCh concentration in the product gas has additional advantages for the further use of the product gas: From a CO2 concentration of more than approx. 215 ppm in the product gas, CO2 may crystallize out during the decompression of the liquefied product gas and this has to be removed - for example by means of sieving.

At least part of the product gas from the third step c) or at least part of the CO2-laden treatment gas from the fourth step d) is preferably used to cool the methane-containing gas in the second step b) (freezing step). For this purpose, the product gas or the processing gas and the methane-containing gas are preferably passed through a heat exchanger, preferably using the countercurrent principle.

The product gas from the third step c) (and in this respect also the part separated from the product gas, which is used as the treatment gas is used) preferably has a temperature of -162 ° C to - 130 ° C, while the methane-containing gas from the first step a) preferably has a temperature of 0 ° C to 40 ° C. Due to the heat exchange in the heat exchanger, the product gas or the treatment gas is heated and the methane-containing gas is cooled at the same time. The product or processing gas is preferably brought to a temperature below, preferably from -20°C to 30°C, more preferably from -10°C to 20°C, particularly preferably from -5°C to 15°C and very particularly preferably from 0°C to 10°C, while the methane-containing gas is preferably cooled to below 10°C, more preferably to below 0°C and most preferably to below -30°C. The cooled methane-containing gas from the heat exchanger is generally further cooled for the subsequent freezing (in the second step b)). The previous exchange of energy between the treatment or product gas and the methane-containing gas makes it possible to reduce the energy requirement for cooling the methane-containing gas, as a result of which the gas treatment can be operated more efficiently and economically.

In a preferred embodiment, the heated product gas from the heat exchanger is used as the treatment gas for the removal of CO2 from the PTSA. If appropriate, the heated product gas is preferably decompressed (ie relaxed) to a pressure of 1 bar before it is passed through the PTSA.

As explained above, when using a PTSA, the CO2 is adsorbed or bound by an adsorbent or an adsorber (usually zeolites or carbon molecular sieves). After the adsorbent is saturated, it must be regenerated or replaced in order to reduce the PTSA to make it operational again. As described above, regeneration of the adsorbent can be achieved, for example, by flowing through the treatment gas in combination with heating and/or expansion of the adsorbent. The regeneration process can be accelerated if the treatment gas flows through the adsorbent against the direction of flow of the methane-containing gas. The combination of heated and expanded treatment gas, which heats the adsorbent to dissolve the CO2 and at the same time flows through the adsorbent to transport the dissolved CO2 away, has proven to be very efficient for the regeneration of the PTSA. With a view to making the process as energy-efficient as possible, no external energy is used to heat the processing gas, but rather the heating takes place - as described above - preferably via the heat exchange between the "cold" product gas and the "warm" methane-containing gas in the heat exchanger. The heated product gas exiting the heat exchanger can then be passed into the PTSA as make-up gas for regeneration of the PTSA.

As described above, heating the adsorbent also contributes to the regeneration of the PTSA. However, after the regeneration of the adsorbent by means of a heated treatment gas, the regenerated adsorbent must be cooled again in order to efficiently adsorb the CO 2 molecules from the methane-containing gas. This cooling can be done using part of the product gas from step c): When it is made available after the CO 2 has been removed in the PTSA, the product gas preferably has a temperature of -130°C to -80°C, more preferably from -120°C to -100°C and most preferably -116°C to -110°C. While part of the product gas is heated - preferably in the heat exchanger described above - to preferably -20°C to 30°C, more preferably -10°C to 20°C and particularly preferably -5°C to 10°C, and then is passed through the adsorbent as heated treatment gas, another part of the product gas from step c) can be used at its original temperature to cool the adsorbent of the PTSA back to operating temperature after regeneration. Thus, cooling of the PTSA adsorbent by means of an external cold source can be avoided, which saves energy and costs.

Before being fed to the PTSA, the methane-containing gas is preferably compressed to 5 to 25 bar, particularly preferably to 10 to 20 bar and very particularly preferably to 14 to 17 bar. With the preferred pressure conditions mentioned, separation of CO2 from the methane-containing gas in the PTSA is particularly efficient.

In a preferred embodiment, the methane-containing gas is used in the PTSA at a temperature of from -130°C to -80°C, more preferably from -120°C to -100°C and most preferably from -116°C to -110° C, fed. The temperatures described are particularly suitable for efficient separation of CO2 from the methane-containing gas in the PTSA.

The methane-containing gas in the first step a) preferably has a CCh concentration of at most 60%, preferably at most 6% and particularly preferably at most 2.5%. The CO2 Concentration here refers to the point in time before the admixture of the CO2-laden treatment gas.

With the method according to the invention it is possible to purify methane-containing gas mixtures with a CCh content of up to 60%, even if this makes little sense from an economic point of view. For this reason, the aim is to keep the CO2 content as low as possible in order to keep the purification effort as low and efficient as possible.

In a further aspect, the invention relates to a device for carrying out the method described above for removing CO2 from a methane-enriched gas. Said device comprises a gas feed line, a compression unit, at least one cooling unit for freezing out CO2, a PTSA, a line for removing a methane-enriched product gas and a treatment gas line, which connects the PTSA and the gas feed line.

The device according to the invention has the advantage over known devices from the prior art that the processing gas line, which connects the PTSA and the gas feed line, can be used to feed the CO2 removed in the PTSA back into the gas feed line, in order to then largely separate by freezing. Because of this, such a device is very efficient in removing CO2 from a methane-containing gas, creating a methane-enriched one

Product gas can be obtained. The invention is explained in more detail below using one of the exemplary embodiments illustrated. It shows in each case purely schematically:

Fig. 1 shows a schematic representation of a preferred embodiment of the method according to the invention for removing CO2 from a methane-containing gas using a PTSA.

In the case of FIG. 1 schematically illustrated preferred embodiment of the method according to the invention, a methane-containing gas 103 containing at least CO 2 as an impurity is provided in a first step a) from a gas feed line 101 .

The methane-containing gas 103 is provided at a pressure of 15 bar and, in a second step b) in a first heat exchanger 105, is cooled down to a temperature TG (temperature in gaseous form) of −32° C. The compressed and cooled methane-containing gas 103 is further cooled down in a second heat exchanger 107 to a temperature TF (temperature freeze) of -114 ° C, at which the CO2 contained in the methane-containing gas 103 is trapped in a lock 109 of the heat exchanger on a surface that is not shown freezes out and is periodically scraped or otherwise removed from said surface. Freezing out allows rapid removal of large amounts of CO2 from the methane-containing gas 103, reducing the CO2 concentration in the gas 103 to below 2100 ppm can . The gas 103 containing methane (and now with a reduced CCh content) is then fed to a PTSA 111 . The PTSA 111 generally comprises a plurality of adsorber containers 115 (only two are shown here), which are operated in parallel, overlapping or alternating with one another.

After the CO2 has been frozen and the methane-containing gas 103 has been fed to the PTSA 111, in a third step c) the remaining CO2 is removed from the methane-containing gas 103 by adsorption on an adsorber 115 present in the PTSA 111, resulting in a methane-enriched product gas 117 is obtained. After purification by the PTSA 111, the methane-enriched product gas 117 has a CCh content of preferably a maximum of 215 ppm. The methane-enriched product gas 117 is transported to a third heat exchanger 119 and liquefied by cooling to -120 °C. It is then fed via a valve 121 into a flash container 123 and decompressed to 1 bar, preferably atmospheric pressure, as a result of which the product gas cools down to preferably −162° C. and at the same time some of it becomes gaseous again. In addition to a decompressed, liquefied product gas 126, a flash gas 127 is generally produced, ie part of the product gas 117 remains gaseous or part of the decompressed, liquefied product gas 126 becomes gaseous again. The flash gas 127 is used as the treatment gas 129 (dashed line) in the method illustrated here. The treatment gas 129 from the flash tank 123 has a CO2 content of preferably less than 215 ppm and a temperature of preferably -162.degree. At least a part of the processing gas 129 (corresponds to the product gas 117 in its composition) is first routed back to the first heat exchanger 105 in order to to cool the methane-containing gas 103 . The treatment gas 129 is preferably heated to 0° C. in the process. The now heated make - up gas 131 is then directed to the PTSA 111 where it is heated and passed through the CO 2 - saturated adsorbers 115 to release the CO 2 from the adsorbers 115 . A treatment gas 133 (dotted line), now enriched with CCh, is transported from the PTSA 111 to a compressor 135, where it is compressed to 15 bar, i.e. the outlet pressure of the methane-containing gas 103.

The compressed treatment gas 133 enriched with CO 2 is then transported through a treatment gas line 134 to the gas feed line 101 and mixed there with the gas 103 containing methane. After the adsorbers 115 of the PTSA 113 have been reprocessed, they are cooled back to operating temperature in order to be able to efficiently adsorb CO2 from the methane-containing gas 103. To cool the adsorber 115, either -162° C. cold product gas 117 or Process gas 129 used.

The decompressed liquefied product gas 126 passes through a particle filter 138 with a pore size of <10 μm, whereby solids in the product gas are removed. The cleaned product gas is then made available to the consumer with a pump 139 . Since the two adsorbers 115 of the PTSA 111 shown can be operated alternately, one adsorber 115 can be processed while the other adsorber 115 adsorbs CO2 from the methane-containing gas 103 . In this way, a constant purification process can be guaranteed.

Claims

patent claims 1. Process for removing CO2 from a methane-containing Gas comprising the steps of: a) providing a methane-containing gas (103) containing at least CO2 as an impurity; b) cooling the methane-containing gas (103) to separate CO2 from the methane-containing gas (103) from step a) by freezing; c) Further reduction of the CCh concentration of the methane-containing gas (103) from step b) by means of a pressure and temperature swing adsorption device (PTSA) (111) , whereby a methane-enriched product gas (117) is obtained; d) Use of at least part (127) of the product gas (117) from step c) as treatment gas (129), which is passed through the PTSA (111) to treat the PTSA (111), whereby CO2 is absorbed by the treatment gas (129). and as a CO2-enriched one removing make-up gas (133) from the PTSA (111); and e) recycling of the processing gas (133) enriched with CO2 that has been routed through the PTSA (111) and admixed to the methane-containing gas (103) in step a). 2. The method according to claim 1, characterized in that the product gas (117) before step d) by cooling entirely or at least partially liquefied, whereby a liquefied product gas (125) is obtained. Process according to Claim 2, characterized in that the product gas (117) for at least partial liquefaction is heated to -140°C to -100°C, preferably -130°C to -110°C and particularly preferably -125°C to -115° C is cooled. Method according to claim 2 or 3, characterized in that the liquefied product gas (125) is decompressed, preferably to approx. 1 bar, whereby a flash gas (127) and a decompressed liquefied product gas (126) are obtained, the flash gas (127) is passed as a treatment gas (129) through the PTSA (111). Method according to one of Claims 1 to 4, characterized in that in step b) the CCh concentration of the methane-containing gas (103) is reduced to below 6000 ppm. Method according to one of claims 1 to 5, characterized in that in step c) the CCh concentration of the product gas (117) to below 5200 ppm, preferably below 830 ppm, more preferably below 215 ppm, particularly preferably below 100 ppm and is most preferably lowered to below 50 ppm. Method according to one of Claims 1 to 6, characterized in that the treatment gas (129) is expanded and preferably heated before it is discharged as expanded and passing optionally heated processing gas (131) through the PTSA (111) in step d). The method according to claim 7, characterized in that the expanded and optionally heated processing gas (131) after its passage through the PTSA (111) in step d) and before its return in step e) or admixture to the methane-containing gas (103) on the Pressure of the methane-containing gas (103) is compressed. Method according to one of Claims 1 to 8, characterized in that at least part of the product gas (117) from step c), or at least part of the processing gas (129) before it is fed to the PTSA (111) in step d) for cooling the provided methane-containing gas (103) is used, preferably by the product gas (117) or the treatment gas (129) and the methane-containing gas (103), preferably in the countercurrent principle, are passed through a heat exchanger (115). Method according to one of Claims 7 or 8, characterized in that at least part of the product gas (117) from step c) is used to cool the methane-containing gas (103) provided, in that the product gas (117) and the methane-containing gas (103) , preferably in the countercurrent principle, are passed through a heat exchanger (115), and that at least part of the heat exchanger (115) exiting heated product gas (117) expands and as a treatment gas (131) for the regeneration of PTSA (111) is used. Method according to one of Claims 1 to 10, characterized in that at least part of the product gas (117) from step c) is used to cool the PTSA (111) after it has been regenerated. Process according to one of Claims 1 to 11, characterized in that the methane-containing gas (103) is fed to the PTSA (111) at a pressure of 5-25 bar, preferably 10-20 bar and particularly preferably 14-17 bar. Process according to Claim 12, characterized in that the methane-containing gas (103) of the PTSA (111) has a temperature of -130°C to -80°C, preferably -120°C to -100°C, particularly preferably -116° C to -110°C, is supplied. Method according to one of Claims 1 to 13, characterized in that the product gas (117) or the liquefied product gas (125) is decompressed before the treatment gas is branched off, preferably to about 1 bar. Method according to one of Claims 1 to 14, characterized in that the methane-containing gas (103) in step a) has a CCh concentration of at most 60%, preferably at most 6% and particularly preferably at most 2.5%. Method according to one of Claims 4 to 15, characterized in that the decompressed liquefied product gas (126) preferably has a particle filter (138). with a pore size of <10 pm, which removes solids from the decompressed liquefied product gas (126). Device for carrying out a method for removing CO2 from a methane-enriched gas according to one of claims 1 to 16, comprising a gas feed line (101), a compression unit (135), at least one cooling unit (105) for freezing out CO2, a PTSA ( 111), a line for removing a methane-enriched product gas (117) and a Make-up gas line (134) connecting the PTSA (111) and the gas feed line (101).