SE538348C2 - Plant comprising a membrane unit and a water scrubber unit for removing carbon dioxide from a gas - Google Patents

Abstract

Plant, where a water scrubber plant 20, mainly consisting of a absorption column 21, ash column 22 and desorption column 23 is integrated with a membrane unit 10, for purification / separation / enrichment of a gas or biogas containing significant amounts of methane and carbon dioxide, whereby the gas content is reduced, gas fl fate 1 is combined with fl ash gas fl fate 24 from fl ash column 22 and pressurized in compressor 30 and then led to a membrane unit 10 for separation of carbon dioxide in one membrane 11, if necessary also water separation or heating in unit 12, hydrogen sulphide in separation unit for particles and hydrogen separator unit pre-particles and other contaminants 14, whereby a residual gas fl desolate 3 is discharged and the purified gas 4 is passed on to a water scrubber plant 20, whereby the energy use for cooling and pumping the recirculating water genom desolate through columns 21, 22 and 23 decreases, alternatively the capacity for production of upgraded gas 5 increases.

Description

Technical field The invention relates to a plant for upgrading biogas and other methane-containing gas gas mixtures to a methane-rich gas. In order to separate carbon dioxide, hydrogen sulphide, water and particles from biogas and other methane-containing gas mixtures, upgrading processes are used that are carried out in different types of upgrading plants. After upgrading the biogas or other methane-containing gas mixtures, a gas with an enriched methane content remains. The methane-rich gas can, for example, be used as a vehicle fuel or for feed to a gas network. Common upgrade techniques today are water scrubber technology, PSA, amine scrubber and membrane technology.

Object of the invention The object of the invention is that a plant for upgrading with water scrubber technology is integrated with a plant that separates mainly carbon dioxide and, if necessary, also hydrogen sulphide, particles and water. In the integrated plant, membrane technology is used to separate the main part of the carbon dioxide and in some applications also hydrogen sulphide and water.

With the invention, the production capacity for upgraded gas from a single-upgrade plant with water scrubber technology can increase. The invention also means that the specific energy consumption per unit of volume of upgraded gas produced is significantly reduced. It is also possible to obtain a carbon dioxide-rich gas from the membranes.

Another purpose of the invention is to enable a lower pressure in the ash column without the water scrubber having a lower capacity. A lower ash pressure reduces methane losses and the recovery means that methane losses can be reduced without the specific energy use per cubic meter of upgraded gas increasing significantly. The recovery can thus be an alternative to second-treatment methods for methane in residual gas fates in countries where the requirement for the methane loss is that the loss must be lower than in the order of 0.5 vol%. An example of a treatment method for pre-gas fates that the invention may replace is RTO.

Background Art Upgrading of biogas aims to obtain a methane-rich product gas by separating mainly carbon dioxide, water and hydrogen sulfide from the biogas. Biogas is currently being upgraded with PSA, water scrubbers, amine scrubbers and membrane technology. The technologies' share of the total market is PSA (23%), water scrubbers (40%), amine scrubbers (22%) and membrane technology (8%). Other upgrade techniques are genosorb scrubbers and cryotechnology (Biogas upgrading - technology overview, comparison and perspectives for the future, Bauer et. Al, DOI: 10.1002 / bbb.1423; Biofuels, Bioprod. Bioref. 7: 499-511 (2013)).

PSA is an upgrade technique where the biogas is compressed and purified from hydrogen sulfide and the water before carbon dioxide is removed in columns containing a material that under pressure adsorbs the carbon dioxide but not methane. Methane can therefore pass through the columns while carbon dioxide is trapped. The adsorption material is then regenerated by pressure reduction, whereby the carbon dioxide is led out of the column.

With water scrubber technology, biogas is usually compressed to 6-10 bar and led to a single absorption column where carbon dioxide and hydrogen sulphide dissolve in water while methane can be taken from the top of the absorption column and then dried. The water is regenerated by pre-depressurizing in an ash column from which some of the carbon dioxide and methane that is dissolved in the gas goes back to the incoming biogas fate. The water is then led to a desorption column where mainly carbon dioxide and hydrogen sulphide are expelled from the water with air.

When upgrading with amine scrubbers, carbon dioxide is separated from biogas by a chemical reaction between carbon dioxide and, for example, activated amines, so-called aMDEA, in an absorption column. Methane does not react with the amine but can be led out from the top of the absorption column. Amine is then regenerated in a desorption column by heating the amine.

A membrane is an somlter that can separate different gas molecules because the molecules have different diffusion rates and solubility in the membrane. Membranes for biogas upgrading often have high permeability to carbon dioxide, water and hydrogen sulfide but not to methane. One-upgrade plant with membrane technology usually first purifies the gas from water and impurities such as hydrogen sulphide before the gas is compressed, normally to 5 - 20 bar, and then led next to membrane modules.

Membrane technology represents an increasing proportion of the upgrade facilities (Biogasupgrading - technology overview, comparison and perspectives for the future, Bauer et. Al, DOI: 10.1002 / bbb.1423; Biofuels, Bioprod. Bioref. (2013)). The membrane technology is under development and the patents US2012111052A1, JP2005023211 (A) and US20130098242A1 describe processes for pre-separation of gases with membrane technology. Lie et al also have the patent US20110072965A1 which describes how a certain type of membrane can be produced which are suitable for separating gases.

There are examples today of how upgrade techniques can be combined. Baker (MembraneTechnology and Applications, ISBN 0-470-85445-6) describes how membrane technology and amine scrubbers can be combined where carbon dioxide is pre-separated with a membrane module before the last carbon dioxide is separated with an amine scrubber. An advantage is that the amine scrubber can be built at a camp cost, while the disadvantage is that the complexity of the plant increases. According to Bhide (Hybrid processes for the removal of acid gases from natural gas, journal of MEMBRANE SCIENCE 1997), however, it is a higher cost to combine membrane technology with an amine scrubber compared to purifying gas with different membrane combinations. The patent US005407466A relates to an invention on how two different types of membranes can be combined and integrated with an amine scrubber or other technology with physical absorption in a genosorb process in order to thereby obtain an improved process gasification treatment.

Membranes can also be combined with PSA technology. The patent ES2411332 (T3) describes how the landfill gas is upgraded by combining membrane technology and PSA. Carbon dioxide is then first separated with membranes and then nitrogen is separated with PSA technology. Another example is the patent USOO2332424A which relates to an invention on how membranes can be integrated with a PSA in order for the ecomethane yield and the degree of purity of the gases The report “Biogas to biomethane technology review” (Technische Universität Wien, IEE / 10/130, May 2012) describes investment cost than water scrubber technology and also that the total upgrade cost is normally lower for membrane technology than water scrubber technology. It also appears that the electricity consumption is 0.46 kWhe | / m3 biomethane pre-water scrubber technology and 0.25 - 0.43 kWhel / m3 biomethane for membrane technology.

Advantages of the invention The invention shows how, based on a water scrubber system, membrane technology can be integrated in such a way that methane losses are reduced, capacity is increased and energy use is reduced. Related inventions have instead focused on integrating membrane technology with other upgrade facilities to complement membrane properties. The patent USOO2332424A is an invention on how membranes can be integrated with a PSA to increase methane yield and gas purity.

The patent US005407466A is an invention on how two different types of membranes can be combined with amine scrubbers or other technology with physical absorption in a genosorb process to thereby maintain an improved gas treatment process. However, this patent does not integrate residual gas fumes from the amine scrubber or genosorb scrubber with the membrane technology in such a way that process methane losses and energy use are reduced and capacity is increased.

By separating carbon dioxide from the incoming biogas flow and / or from the ash gas with the help of membrane technology, the water scrubber's specific energy consumption per upgraded volume unit can reduce gas.

With the invention, the capacity for the production of upgraded gas from a single-water scrubber plant is increased as its capacity is mainly dependent on the total incoming gas flow to the absorption column. An integrated process that raises the methane content of the biogas before the gas is upgraded in the water scrubber, or reduces the internal circulation of gas, thus means that the water scrubber has a higher capacity. In cases where the water scrubber's compressor limits the capacity of the plant, this can be supplemented with additional compressor capacity.

The heat allows the pressure in the ash column to be reduced without increasing the use of water scrubber energy or significantly reducing capacity. This creates the possibility of achieving camp methane losses than has previously been applicable. The methane loss from a water scrubber with the integrated recovery may be less than 0.5 vol%. In markets where 0.5% by volume of methane loss is sufficient, the increase provides a saving for investing in residual gas treatment plants such as RTO. A reduced methane loss also results in greater production of upgraded gas and thus higher revenues.

The process design of the water scrubber does not allow, unlike amine scrubbers and PSA, that a separate gas fl fate with a high carbon dioxide content can be obtained. With the invention, a separate carbon dioxide-rich gas fate can be obtained which can be used for, for example, catalytic or biological methanation.

Membrane technology can be integrated with durable water scrubber systems and thereby increase the scrubber's production capacity of upgraded gas. The advantages of membrane technology with relatively low investment costs and specific energy use can then be applied to some exhaust fumes, at the same time as the total capacity is higher and a significant part of the equipment on the non-toxic plant can be used. The investment to supplement a permanent water scrubber plant with membrane technology and associated equipment, as well as supplementary compressor capacity if the permanent compressor capacity does not cope with increasing gas fate, is judged to be lower than investing in a completely new upgrading plant for upgrading biogas plant. The invention also offers the advantage that a buyer of a single-water scrubber plant has a good alternative to increasing capacity in the future.

The extension can also be used for new construction of an upgrade facility. The integration between membrane technology and a water scrubber plant enables lower methane losses, high capacity, lower energy use and recovery of carbon dioxide in comparison with a conventional water scrubber plant.

Brief description of the drawings Examples of embodiments of the invention will be described in more detail with reference to the accompanying drawings. Figure 1 schematically shows a water scrubber that is integrated with a plant that separates mainly carbon dioxide, hydrogen sulphide, particles and water, where membrane technology is used to separate the main part of the carbon dioxide. Incoming till fates to the membrane unit can be biogas and fl ash gas from the water scrubber fl ash column. Figure 2 shows an application where the invention is used to separate gases such as carbon dioxide from the ash gas without first increasing the ash gas. Figure 3 shows an application where a water scrubber is integrated with processes that separate gases such as carbon dioxide from the fl ash gas, from the incoming gas fl desert to the plant and from the outgoing gas from the plant that separates gases such as carbon dioxide from the fl ash gas.

Detailed description of exemplary embodiment shown Figure 1 schematically shows a plant for upgrading biogas where a water scrubber plant 20, mainly consisting of an absorption column 21, ash column 22 and desorption column 23, is integrated with membrane unit 10 for separation of gases such as carbon dioxide with membrane separation 11 and for water 12, separation unit for hydrogen sulphide 13 and separation unit for particles and other pollutants 14. An alternative configuration for separating water in separation unit 12 is to instead heat the gas with a heat exchanger.

Gas de fate 1 in Figure 1 is combined with gas de fate 24 and led into a compressor 30 to raise the pressure. Gas fl fate 2 after compressor 30 maintains a pressure between 2-18 bar, mainly 4-16 bar, preferably 8-12 bar and contains mainly methane, carbon dioxide, water, hydrogen sulphide and particles. The carbon dioxide content in the incoming gas fl fate 1 is normally between 20- 60 vol- ° / o, mainly 30-50 vol-%, most preferably 40-50 vol-%. The methane content in gas fl fate 1 is normally between 40-80 vo | -%, mainly 50-70 vol-%, most preferably 50-60 vo | - ° / o.

In the plant configuration according to Figure 1, gas 2 2 is led into the membrane unit 10 consisting of separation unit for water 12, separation unit for hydrogen sulphide 13, separation unit for particulate matter and other pollutants 14 and membrane for separation of carbon dioxide 11. The mutual order between the constituent steps in the membrane unit varies. Units 12, 13 and 14 are established and used to the extent required by the membrane design and biogas composition. The units 12, 13 and 14 are placed after the compressor, but one or more of them can also be placed before the compressor.

After passing the various purification steps / separation steps in the membrane unit 10 in Figure 1, the gas enters the membrane 11 to separate gases such as carbon dioxide, hydrogen sulphide and water. The membranes can be of the polymeric hole type fimembranes, carbon membranes or other types of membranes and different types of membranes can be combined with each other as well as that only one type is used. The membranes can be arranged in series or in parallel or be a combination of the two.

From membrane 11 in Figure 1 goes a residual gas fl fate 3 which for the most part contains carbon dioxide and smaller amounts of methane. Residual gas fl can be burned in a boiler, destroyed with thermal oxidation or handled in another way.

According to the plant configuration in Figure 1, gas de desert 4 continues from the membrane 11 to the water scrubber unit 20 with a higher methane content compared to gas med desert 2 which enters the membrane unit 10. The higher methane content in gas fl desert 4 means that the capacity increases in the absorption column 21 due to less carbon dioxide being separated21 , compared with if the methane content was the same in gas flow 4 as in gas de fate 2. Since it is the total gas fl fate to the absorption column that affects the capacity in absorption column 21, upgraded gas can be produced because gas fl fate 4 has a higher methane content than biogas fl fate 1. Energy consumption can also be reduced due to the fact that the water scrubber unit 20 has a reduced cooling requirement and because the amount of water required to separate the carbon dioxide in gas fl desolation 4 is less than the amount of water needed to separate the carbon dioxide in gas fl desolation 2.

Under typical conditions with 50 vol% carbon dioxide in gas fl fate 1, the capacity for production of upgraded methane-rich gas in absorption column 21 can be increased by 40-70% and the energy use pre-cooling and pumping of the recirculating water fl fate through columns 21, 22 and 23 decreased by 10-20% with a process configuration according to Figure 1.

Under typical conditions with 40 vol% carbon dioxide in gas fl destiny 1, the capacity for production of upgraded methane-rich gas in absorption column 21 can be increased by 30-40% and the energy use for cooling and pumping the recirculating water fl destiny through columns 21, 22 and 23 can be reduced by 5- 15% with a plant configuration according to Figure 1.

Under typical conditions with 35 vol% carbon dioxide in gas de fate 1, the capacity for production of upgraded methane-rich gas in absorption column 21 can be increased by 20-30% and the energy use pre-cooling and pumping of the recirculating water fl fate through columns 21, 22 and 23 decreased by 5-10 % with a plant configuration according to Figure 1.

In the plant configuration according to Figure 1, the gas flow from the ash column 22 is returned with gas flow according to gas flow 24. The pressure allows the pressure in the ash column 22 to be reduced without reducing the capacity for production of upgraded gas 5 in absorption column 21 or using energy for cooling and pumping water. onns 21, 22 and 23 increase significantly. This creates the possibility of reducing the total methane loss from the upgrading plant to less than 0.5% vol., Which can lead to increased revenues from gas sales and reduced costs for disposing of residual gas fl destiny 6.

From the absorption column 21 in Figure 1, a gas fl desolate 5 having a methane content above 95% by volume leaves, from the desorption column 23, a residual gas fl deserts 6 containing for the most part carbon dioxide and air.

Figure 2 schematically shows a plant for upgrading biogas where a water scrubber plant 20, mainly consisting of an absorption column 21, ash column 22 and desorption column 23, is integrated with membrane unit 10 for separating carbon dioxide with membrane module 11 and, if necessary, separation unit for water unit 12, separation unit and water unit 12. for particles and other pollutants 14. An alternative configuration for separating water in separation unit 12 is to heat the gas with a single heat exchanger instead. The relative order between the constituent steps in membrane unit 10 can vary. Units 12, 13 and 14 are established and used to the extent required by the design of the membranes and the composition of the biogas.

In Figure 2, gas fl deserts 1 and 7 are combined and led into a compressor 30 to increase the pressure. Gas fl fate 2 maintains after compressor 30 a pressure between 2-18 bar, mainly 4-16 bar, preferably 8-12 bar and contains methane , carbon dioxide, water, hydrogen sulfide and particles. The carbon dioxide content in the incoming gas fl fate 1 is normally between 20-60 vol-%, mainly 30-50 vol- ° / o, most preferably 40-50 vol-%. The methane content in gas fl fate 1 is normally between 40-80 vol-%, mainly 50-70 vol-%, most preferably 50-60 vol- ° / o.

In the plant configuration according to Figure 2, gas fl desolate 2 is led into water scrubber plant 20. The water scrubber plant is integrated with membrane unit 10 by directing gas fl desert 24 "from fl ash column 22 to membrane unit 10. From membrane module 11 a gas de desert with high methane content is obtained The membranes can be of the polymeric hole type, membrane membranes, carbon membranes or other types of membranes and different types of membranes can be combined with each other as well as only one type is used. The membranes can be arranged in series or in parallel or be a combination of the two.From membrane 11 runs a residual gas fl fate 3 which for the most part contains carbon dioxide and methane.Rest gas fl fate can be burned in a boiler, destroyed by thermal oxidation or handled in other ways.

In a conventional water scrubber system, the ash gas is returned directly to the compressor suction side. The solution with process configuration according to Figure 2 means that gas fate 2 has a lower carbon dioxide content in comparison with a water scrubber plant where the solution is not used. The high methane content in gas fl destiny 2 means that the capacity for production of upgraded gas 5 increases in the water scrubber plant 20 due to the fact that less carbon dioxide needs to be separated in the absorption column 21, compared with if the ash gas is returned directly to the suction side of the compressor. The energy consumption can also be reduced as a result of the water scrubber unit 20 having a reduced cooling demand and because the amount of water required to separate the carbon dioxide in gas 2 is less than the amount of water needed if the ash gas had been recirculated directly to the suction side of the compressor.

Under typical conditions with 80-90 vol% carbon dioxide in the ash gas, the capacity of the water scrubber can be increased by about 10-20% and the energy consumption can be reduced by 10-20% with the co-process configuration according to Figure 2.

In the plant configuration according to Figure 2, the gas fate is transferred from the ash column 22 to the membrane unit 10 according to the ash gas fate 24 ”. The invention means that the pressure in the ash column 22 can be reduced without the capacity in the absorption column 21 being reduced or that the energy use for cooling and pumping the recirculating water through the columns 21, 22 and 23 increases significantly. It creates the possibility of coming down to a total methane loss from the upgrading plant that is less than 0.5 vol%, which can increase revenues for gas sales and reduced costs for disposal of residual gas rest fate 6.

Figure 3 schematically shows a plant for upgrading biogas where a water scrubber plant 20 is integrated with the membrane units 10a and 10b. The water scrubber plant 20 consists mainly of an absorption column 21, ash column 22 and desorption column 23. Membrane unit 10a consists of membrane module 11a for separation of carbon dioxide and water separation unit 12a, hydrogen sulfide separation unit 13a and particulate and other impurity separation unit 14a. An alternative configuration for separating water in separation unit 12a is to instead heat the gas with a single heat exchanger. Membrane unit 10b consists of membrane module 11b for separation of gases such as carbon dioxide and if necessary also separation unit for water 12b, separation unit for hydrogen sulphide 13b and separation unit for particles and other pollutants 14b. An alternative configuration allowed to separate water in separation unit 12b is to instead heat the gas with a heat exchanger.

Gas fl fate 1 is combined in Figure 3 with gas de fate 7 and led into a compressor 30 to raise the pressure. Gas de destiny 2 maintains after compressor 30 a pressure between 2-18 bar, mainly 4-16 bar, preferably 8-12 bar and contains methane, carbon dioxide, water, hydrogen sulphide and particles. The carbon dioxide content in gas fl desolation 1 is normally between 20-60 vol%, mainly 30-50 vol%, most preferably 40-50 vol%. The methane content in gas gas destiny is normally between 40-80 vol%, mainly 50-70 vol%. - ° / u, preferably 50-60 vol-%.

In the plant configuration according to Figure 3, gas fl 2 is led into the membrane unit 10 consisting of a separation unit for water 12a, a separation unit for hydrogen sulphide 13a, a separation unit for particles and other pollutants 14a and a membrane for the separation of gases such as carbon dioxide 11a. The relative order between the included steps in membrane unit 10a can vary. The units 12a, 13a and 14a are established and used to the extent required by membrane design and biogas composition. The units 12a, 13a and 14a are placed in Figure 3 after the compressor 30, but one or more of them can also be placed before the compressor 30.

After passing the various purification / separation steps in the membrane unit 10a in Figure 3, the gas enters the membrane 11a to separate gases such as carbon dioxide, hydrogen sulfide and water. The membranes may be of the polymeric hole type ermmembranes, carbon membranes or other types of membranes and different types of membranes can be combined with each other as well as that only one type is used. The membranes can be arranged in series or in parallel or be a combination of the two.

From membrane 11a in Figure 3 is a residual gas fl destiny 3a which for the most part contains carbon dioxide and smaller amounts of methane. Residual gas fl can be burned in a boiler, destroyed with thermal oxidation or handled in another way.

In the plant configuration according to Figure 3, gas fl fate 4 is led in to water scrubber plant 20. The water scrubber plant is integrated with membrane unit 10b by directing gas 24 fate 24 ”from fl ash column 22 to membrane unit 10b. From membrane module 11b a gas fl fate with high methane content is obtained which is either combined with gas fl fate 1 on the suction side of the compressor according to gas fl fate7 or combined with the outgoing gas fl fate 5 from the absorption column 21 according to gas fl fate 8. The membranes can be of the polymeric holes fi membrane or other membranes membranes can be combined with each other as well as only one type is used. The membranes can be arranged in series or in parallel or be a combination of the two. From membrane 11b flows a residual gas stream 3b which for the most part contains carbon dioxide and methane. The residual gas can be burned in a boiler, destroyed by thermal oxidation or otherwise handled.

The arrangement with plant configuration according to Figure 3 means that gas fate 4 has a lower carbon dioxide content in comparison with a water scrubber plant where membrane units 10a and 10b are not integrated. The high methane content in gas de fate 4 increases the capacity of the water scrubber plant 20 due to less carbon dioxide having to be separated in the absorption column 21. Since it is the total gas fl fate of the absorption column that affects the capacity of water scrubber 20, more upgraded gas can be produced. The energy consumption can also be reduced as a result of the water scrubber unit 20 having a reduced cooling requirement and because the amount of water required to separate the carbon dioxide in gas fl 4 is less than the amount of water that would have been needed if membrane units 10a and 10b had not been integrated with the water scrubber plant.

Under typical conditions with 50 vol-% carbon dioxide in gas fl fate 1, the capacity for production of upgraded methane-rich gas in absorption column 21 can be increased by 40-80% and the energy consumption pre-cooling and pumping of the recirculating water flow through columns 21, 22 and 23 with 10-30% with a process configuration according to Figure 3.

Under typical conditions with 40 vol% carbon dioxide in gas fl fate 1, the capacity for production of upgraded methane-rich gas in absorption column 21 can be increased by 30-50% and the energy consumption pre-cooling and pumping of the recirculating water fl fate through columns 21, 22 and 23 decreased by 5-25% in the process configuration according to Figure 3.

Under typical conditions with 35 vol% carbon dioxide in gas fl fate 1, the capacity for production of upgraded methane-rich gas in absorption column 21 can be increased by 20-40% and the energy consumption pre-cooling and pumping of the recirculating water fl fate through columns 21, 22 and 23 decreased by 5-15% in the process configuration according to Figure 3.

In the plant configuration according to Figure 3, the gas flow from ash column 22 to membrane unit 10b is carried according to ash gas flow 24 ". The invention allows the pressure in ash column 22 to be lowered without reducing the capacity of absorption column 21 or increasing energy use for cooling and pumping the recirculating water. It creates the possibility of reducing the total methane loss from the upgrading plant to less than 0.5% by volume, which could lead to increased revenues for gas sales and reduced costs for the pre-disposal of gas fl destiny 6.

From the absorption column 21 in Figure 3, a gas fl desolate 5 having a methane content above 95% by volume leaves, from the desorption column 23, a residual gas fl desolate 6 containing for the most part carbon dioxide and air.

Claims (7)

Plant, in which a water scrubber plant 20, consisting essentially of one absorption column 21, ash column 22 and desorption column 23 is integrated with a membrane unit 10, for purification / separation / enrichment of a gas or biogas containing significant amounts of methane and carbon dioxide, thereby reducing the gas dioxide content, which is characterized in that incoming gas fl desolate 1 is combined with fl ash gas flow 24 from flash column 22 and raised in pressure in compressor 30 and then led to a membrane unit 10 for separation of carbon dioxide in a membrane 11, if necessary also water separation or heating in unit 12, hydrogen sulphide and particle hydrogen and other contaminants in the particulate and other contaminant separation unit 14, with residual gas fl desolate 3 escaping and the purified gas 4 being passed on to a water scrubber plant20, the energy use for cooling and pumping the recirculating water fl through the columns 21, 22 and 23 decreasing, alternatively to capacity a gas upgraded for production 5 increases. Plant according to 1, characterized in that the pressure in ash column 22 can be lowered without the capacity for production of upgraded gas 5 in absorption column 21 decreasing significantly or that the energy use for cooling and pumping the recirculating water stream through columns 21, 22 and 23 increases significantly, thereby reducing methane losses. . Plant according to 1 or 2, characterized in that the plant is supplemented with additional compressor capacity. Plant, in which a water scrubber plant 20, consisting essentially of an absorption column 21, ash column 22 and desorption column 23 is integrated with a membrane unit 10, for purifying / separating / enriching a gas or biogas containing gases such as methane and carbon dioxide, thereby reducing the carbon dioxide content of the gas, characterized in that fl ash gas fl waste 24 "from fl ash column 22 belonging to water scrubber plant 20 is led to a membrane unit 10 for separating carbon dioxide in a membrane 11, if necessary also water separation or heating in unit 12, hydrogen sulphide in separation unit and particle units for sulfur hydrogen 14, whereby a residual gas fl destiny 3 escapes and the methane rich gas 7 is combined with incoming gas fl destiny 1 and pressurized in compressor 30 and then led to water scrubber unit 20, whereby the energy use for cooling and pumping the recirculating water fl destiny through columns 21, 22 and 23 decreases, al alternatively the capacity for upgraded gas production 5 increases. Plant according to claim 4, characterized in that the pressure in the ash column 22 can be lowered without the capacity for production of upgraded gas 5 in the absorption column 21 decreasing significantly or that the energy use for cooling and pumping the recirculating water stream through the columns 21, 22 and 23 increases significantly, thereby reducing methane loss. . Plant according to 4 or 5, characterized in that the plant is supplemented with additional compressor capacity. Plant, in which a water scrubber plant 20, consisting essentially of one absorption column 21, ash column 22 and desorption column 23 is integrated with a membrane unit 10, for purifying / separating / enriching a gas or biogas as containing gases such as methane and carbon dioxide, thereby reducing the carbon dioxide content of the gas. characterized in that fl ash gas fl waste 24 "from fl ash column 22 associated with water scrubber plant 20 is led to a membrane unit 10b for separating carbon dioxide in a membrane 11b, if necessary also water separation or heating in unit 12b, hydrogen sulphide in separation unit and particle dehumidification unit pollutants 14b, whereby a residual gas fl fate 3b is removed and the methane-rich gas 7 is combined with gas fl fate 1 and pressurized in compressor 30 and then led to a membrane unit 10a for separating carbon dioxide in a membrane 11a, if necessary also water separation or heating in unit 12a, sulfur water unit of hydrogen sulphide 13a and particles and other pollutants in the separation unit for particles and other pollutants 14a, whereby a residual gas fl desolate 3a is discharged and the purified gas 4 is passed on to a water scrubber plant 20, whereby the energy use for cooling and pumping alternatively that the capacity for production of upgraded gas 5 increases. Plant according to 7, characterized in that the pressure in ash column 22 can be lowered without the capacity for production of upgraded gas 5 in absorption column 21 decreasing significantly or that the energy use for cooling and pumping the recirculating water through the columns 21, 22 and 23 increases significantly, thereby reducing methane loss. Plant according to 7 or 8, which is characterized in that the plant is supplemented by an additional compressor capacity.