CZ306061B6 - Apparatus for modification of biogas to fuel of natural gas type - Google Patents

Abstract

In the present invention, there is disclosed an apparatus for modification of biogas to fuel of a natural gas type, the apparatus comprising an inlet unit having the nature of a desulfurizing section adapted for desulfurizing to residual concentration of Hi2S in the range of 2 to 7mg/me3of biogas and further a separation unit with a dewatering section, adapted for the removal of moisture to the residual concentration of up to the most 32 mg Hi2O/me3, and with a separation section adapted for high-pressure separation of COi2 in several pressure stages with output pressures ranging from 0.5 to 14.8 MPa, adapted for achieving the CHi4 fraction in an amount of at least 95 percent by volume and for achieving at the most 2 percent by volume of COi2 and 0 mg Ni2(NHi3)/kg, wherein the invention is characterized in that the inlet unit (10), with the nature of a desulfurizing section is performed as a chemical separation and/or scrubbing column provided with at least one adsorber (1) with a charge having hydrated iron oxide as a reaction component, adapted for passage of biogas. It is provided with an air inlet (11) for regeneration of the charge and a mud outlet (12) for condensate, Father, the separation unit comprises a dewatering section (20), performed as a dehumidifying column, followed up with a separation section (30) performed as a high-pressure separator of COi2 with high-pressure separation of COi2 and increase in volume of CHi4 fraction. Preferably, the apparatus also comprises storage and filling device (50), arranged after the separation unit, for filling transportation pressure cylinders or pressure tanks of vehicles or a regulation station for distribution of biogas for use as a fuel with the natural mgs grade. At the same time, it is advantageous, when an additional purification section (40) is arranged after the high-pressure separator.

Description

Equipment for the treatment of biogas into natural gas type fuel

Field of technology

The invention relates to a plant for the treatment of biogas, consisting in particular in the removal of CO2 while increasing the volume of CH4 by pressurization and further in the removal of H ₂ S, moisture (H ₂ O) and N ₂ (NH ₃ ) for use as fuels, including motor fuel.

Prior art

At present, devices are known for converting biogas into gas with properties comparable to natural gas, where such devices contain mainly gas separation sections, for the separation of CO ₂ in particular, on the principle of washing gases in water or other liquids, at low , or even at high, resp. alternating pressure, using the different adsorption and absorption capabilities and properties of these liquids. Another possibility is the adsorption of CO ₂ on a solid adsorbent using alternating pressure. It is by modifying the pressures and temperatures that it is possible to significantly increase the indicated efficiency of the catching liquids as well as the activated carbon used. There are also devices based on the separation of biogas components using a molecular sieve. Although such a separation makes it possible to obtain a gas with a predominant proportion of methane and other properties which are also substantially satisfactory, the devices operating on the described principle are very expensive to manufacture and operate. Furthermore, in order to use the fuel thus obtained as motor fuel, in connection with the described separation station it is necessary to install a filling station, of the CNG filling station type, which makes the device even more expensive and energy intensive, as a significant share of the required energy input The production of biomethane on the adsorption and / or absorption principle, as well as the compression of biomethane for filling tanks, especially in vehicles, has the whole process. In addition to the already mentioned disadvantages, the main disadvantage of the known and described devices is their high investment intensity, which currently results in economically acceptable feasibility only for plants with a production capacity of at least 500 m ^{3 of} raw biogas per hour, ie about 4000 thousand. m ³ / year.

The essence of the invention

These disadvantages are substantially solved by a device for the treatment of biogas into natural gas type fuel, comprising an input unit with the nature of a desulphurisation section, adapted for desulphurisation to a residual concentration of H ₂ S 2 to 7 mg / m ^{3 of} biogas , adapted to remove moisture up to a residual concentration not exceeding 32 mg H2O / m ³ and with a separation section adapted for high-pressure CO2 separation in multiple pressure stages with outlet pressures from 0,5 to 14,8 MPa, adjusted to achieve a CH4 content of at least 95 % by volume and to achieve a maximum of 2% by volume CO ₂ and 0 mg N ₂ (NH ₃ ) / kg, the essence being that the input unit, with the nature of a desulphurisation section, is formed as a chemical separation column and / or as a washing column , with at least one adsorber with a charge, the reactant of which is hydrated iron oxide, adapted for the passage of biogas and provided with an additional air supply for regeneration of the charge and a desilting outlet for condensate, and further in The dewatering section contained in the separation unit is formed as a dehumidification column, and the separation section downstream of it is formed as a high-pressure CO ₂ separator with high-pressure CO ₂ separation and an increase in the CH4 volume fraction. Preferably, a storage and filling device for filling transport pressure vessels or pressure tanks of vehicles or a control station for distribution for the use of biogas as a natural gas quality fuel is arranged behind the separation unit. It is also advantageous if the high-pressure CO ₂ separator is designed as a high-pressure multistage compressor system, where a CO ₂ -based liquefied component separator is always included between the individual stages and the outlet from the last high-pressure compressor stage is connected to a filling device for filling transport pressure vessels or pressure vessels. tanks of vehicles where, before this connection,

- 1 CZ 306061 B6 within the separation unit, the finishing section of the produced biomethane is added. It is also advantageous if the CO ₂ -based liquefied component separator comprises a fine mechanical filter, a carbon filter and at least one membrane separator. Preferably, the gas outlet of the at least one membrane separator is connected back to the dehumidification section and / or one of the lower stages of the compressor. The finishing section is preferably formed as a system of separation columns, namely as a system of at least one final dehumidification column packed with CaCl ₂ and at least one column of final final purification of CO ₂ and N ₂ (NH ₃ ), packed with zeolite. Preferably, the dewatering section then consists of at least two separation columns packed with CaCl ₂ and a fine mechanical filter, located in front of and behind the outlet of the screw compressor with an outlet pressure of 0.5 to 1 MPa. Alternatively, the dewatering section is formed as a dehumidification column, comprising at least one heating chamber connected in series, adapted to heat the processed biogas, and at least one cooling chamber provided with a cooling circuit and a sludge outlet for draining condensed water. The main multistage compressor then has operating pressures of 0.5 to 14.8 MPa, as can be seen from the basic embodiment described above.

In this way, a device for the conversion of biogas into gas is achieved, usable primarily as a motor fuel, and this device is investment-intensive and operationally inexpensive, especially in the area of relatively low volumes of processed biogas.

Explanation of drawings

The invention is further described and explained in more detail on an exemplary embodiment, also with the aid of the accompanying drawings, in which FIG. 1 shows a diagram of the whole device in an exemplary embodiment, FIG. 2 shows a circuit of a desulfurization section with a flow switching arrangement; there is an example in axonometry of a practical embodiment of the construction of the separating unit, after which the same separating unit can be seen in Fig. 4, this time in plan view.

Examples of embodiments of the invention

The device in the exemplary embodiment is designed as a station for converting biogas to natural gas quality gas, also referred to as biomethane, where the output is a filling station for pressure vessels in CNG vehicle propulsion systems and control stations for gas use as natural gas fuel. gas. The following is a detailed description of an exemplary embodiment of this device.

- Model solution of a biogas treatment plant with an output of 45 m ³ / h

Device functions

The device solves the treatment of biogas to the quality of motor fuel for petrol engines and provides other additional functions such as:

- storage of purified biogas,

- filling of biogas into motor vehicles,

- regulation of biogas pressure for its use as a fuel in the quality of natural gas.

Useful properties of the device

The biogas produced at this plant, ie the biogas plant, hereinafter also referred to as BPS, contains less O ₂ than requires its use as a motor fuel for petrol engines. Therefore, only the parameters CH4, CO ₂ , H ₂ S, water vapor (H ₂ O) and N ₂ (NH ₃ ) are adjusted.

-2GB 306061 B6

Orientation parameters for which the device is designed

Capacity 45 m ³ biogas / h *

Operating hours 24 hours / day

360 days / year

8640 hours / year

Capacity

- biogas before processing 388 800 m ³ / year, 45 m ³ / h *

- biogas after processing 233 280 m ³ / year, 27 m ³ / h *.

Note: * The capacity of the plant is given in the volume of biogas at a pressure of 0.01 MPa as fed from the BPS reactor.

Useful properties of the device

Values of treated biogas:

CH ₄ min. 95% by volume

CO ₂ 2% by volume

H ₂ S 2 to 3 mg / m ³

H ₂ O 32 mg / m ³

N ₂ (NH ₃ ) about 0%.

- List of operating files, resp. units and sections, and their machinery and equipment, including the main parameters:

The outputs of the sub-plants are given in volumes of biogas at a pressure of 0.01 MPa.

- An inlet unit 10, designed as a desulphurisation section with two adsorbers 1, provided with an additional air inlet 11 for regenerating the charge and a desilting outlet 12 for draining any condensate.

Principle: the adsorber works on the basis of chemisorption of sulfane on hydrated iron oxide and shows for example the following parameters:

capacity 40 to 50 m ³ / h (max. 65 m ³ / h) operating pressure 0.01 MPa biogas parameters:

H ₂ S at inlet 1390 (3500) mg / m ³ biogas

H ₂ S at the outlet max. 2 to 3 mg / m ^{3 of} biogas inlet temperature 40 ° C outlet temperature in summer 25 to 35 ° C in winter 15 ° C.

The separation unit comprises a dewatering section 20 operating on the basis of the adsorption of H ₂ O in a charge of crystalline CaCl 2, as well as a separation section 30 and a purification section 40.

biogas input parameters:

pressure H ₂ S at inlet humidity amount CH4 amount CO ₂ 0.01 MPa max. 2 to 3 mg / m ³ biogas 7 (max. 10)% volume 55 (min. 40)% volume 33 (max. 55)% volume inlet temperature in summer in winter 25-35 ° C 15 ° C.

Drainage section equipment components 20:

Dehumidification separation column 21 filled with CaCl ₂ and a replaceable mechanical filter 23 with a permeability of 0.01 μ.

power operating pressure filling 40 to 50 m ³ / h 0.01 MPa 100 kg of crystalline CaCl ₂ , filling change recommended after 4 months of operation.

Screw compressor 22 with heat exchanger 221 and other common accessories:

power inlet pressure outlet pressure 40 to 50 m ³ / h 0.01 MPa 0.8 MPa (max. Protection).

Dehumidification separation column 21 with CaCl ₂ packing and a replaceable mechanical filter with a permeability of 0,01 μ, placed next, still behind the screw compressor 22:

power operating pressure filling 40 to 50 m ³ / h 0.8 MPa 100 kg CaCl ₂ , change of charge after 4 months of operation.

Biogas output parameters:

pressure H ₂ S humidity (H ₂ O) amount CH4 amount CO ₂ 0.8 MPa max. 2 to 3 mg / m ³ biogas max. 34 mg / m ³ biogas 55 (min. 40)% by volume 33 (max. 55)% by volume temperature in summer in winter 35-45 ° C 25 ° C.

-4GB 306061 B6

Separation section 30, as a device increasing the volume of CH ₄ and removing CO ₂ and N ₂ (NH ₃ ).

Principle: the majority of CO ₂ is removed by pressurization, N ₂ (NH ₃ ) and residual CO _{2 by} separation.

Biogas input parameters:

pressure

H ₂ S

Moisture (H ₂ O) amount of CH ₄ amount of CO ₂ amount of N ₂ (NH ₃ )

0.8 MPa max. 2 to 3 mg / m ³ biogas max. 34 mg / m '' biogas 55 (min. 40)% volume 33 (max. 55)% volume 0.85 (max. 1.8)% volume temperature in summer in winter up to 45 ° C ° C.

Equipment components - separation section 30.

High-pressure reciprocating compressor 31, four-stage CO ₂ pressure separation, with a heat exchanger 311 after each of the four stages and other common accessories:

power inlet pressure pressure - 1st stage pressure - 2nd stage pressure - 3rd stage outlet pressure up to 50 m ³ / h

0.8 MPa

MPa, 40 to 50 m ³ / h

MPa, 29 m ³ / h

10.4 MPa, 29 m ³ / h

25.0 MPa, 27 to 29 m ³ / h

Mechanical filter 32 with a permeability of 0.01 μ, fitted after the 1st pressure stage.

output operating pressure number up to 50 m7h

MPa pcs.

Carbon filter 33, fitted after the 1st pressure stage:

performance the operating pressure 40 to 50 m ³ / h 20 MPa.

Membrane separator 34 for separating CO ₂ , N ₂ (NH ₃ ), equipped after the 1st pressure stage:

performance the operating pressure 40 to 50 m ³ / h 20 MPa

number of 2 pieces, from the first separator 34 branching of substantially raw biogas also towards the cogeneration unit with the internal combustion engine.

-5CZ 306061 B6

Separator 35 CO ₂ with replaceable mechanical filter, fitted after 2nd and 3rd pressure stage:

output 29 m ³ / h operating pressure behind the 1st stage 3 MPa behind the 2nd stage 10.4 MPa

number 2 pcs.

Biogas output parameters:

pressure H ₂ S humidity (H ₂ O) amount CH ₄ amount CO ₂ amount N ₂ (NH ₃ ) 25.0 MPa max. 2 + 3 mg / m ³ biogas max. 34 mg / m ³ biogas min. 95% by volume 2.15% by volume 0.05 (max. 0.1)% by volume summer temperature in winter 35-45 ° C 25 ° C.

- Finishing section 40 for final finishing and other additional equipment.

Principle: The device works on the basis of adsorption of H ₂ O residues in the crystalline CaCl ₂ charge of CO ₂ and N ₂ (NH ₃ ) residues in the zeolite charge.

Biogas input parameters:

pressure 25.0 MPa H ₂ S humidity (H ₂ O) amount CH ₄ amount CO ₂ amount N ₂ (NH ₃ ) max. 2 to 3 mg / m ³ biogas max. 34 mg / m ³ biogas min. 95% by volume 2.15% by volume 0.05 (max. 0.1)% by volume temperature in summer in winter 35-45 ° C 25 ° C.

Final dehumidifier separator 41 filled with CaCl 2

power inlet pressure outlet pressure operating temperature number 27 to 29 m ³ / hour 25.0 MPa 24.3 MPa 5 to 10 ° C 1 p.

-6GB 306061 B6

Separator 42 for final final purification of CO ₂ , N ₂ (NH ₃ ) with zeolite filling:

output inlet pressure outlet pressure operating temperature number up to 29 m ³ / hour

24.3 MPa

23.5 MPa to 10 ° C pcs.

ίο Biogas cooler 43 - freon cooling unit with accessories:

output biogas pressure biogas temperature inlet outlet up to 29 m ^J biogas / h

25.0 MPa max 45 ° C 5 to 10 ° C.

To ensure practical operation, pneumatic valve control is also used, not shown here, with the following parameters and accessories:

compressed air compressor 0.6 to 0.8 MPa, compressed air piping with accessories.

A gas analyzer is used to measure the quality of biogas, while during the test operation, an indicative measurement was performed using a device for taking biogas from individual phases of its treatment for laboratory quality verification.

Detected biogas output parameters: 30 pressure H ₂ S Humidity (H ₂ O) amount CH ₄ 23.5 MPa max. 2 to 3 mg / m ³ biogas max. 32 mg / m ³ biogas min. 95% by volume 35 amount of CO ₂ amount of N ₂ (NH ₃ ) temperature 2% by volume 0% by volume 5 to 10 ° C.

- Storage and distribution equipment 50 for treated biogas.

- VTL gas tank:

blocks of 10 bottles, of which:

1 block capacity 9201 operating pressure 23.5 MPa number 1 pcs.

blocks: capacity operating pressure number

64401

20.0 MPa pcs

- Control station:

capacity inlet pressure outlet pressure number max. 50 m ³ / h

20.0 MPa 0.4 MPa 1 pc.

- Filling of treated biogas into motor vehicles:

Dispenser:

mechanical filling set with NGV-1 end piece type SEKO operating pressure 20.0 MPa number of 1 pcs.

Description of details and function of the device according to the invention:

Modification of biogas to the quality of motor fuel for petrol engines takes place in three successive stages by removal:

sulfur compounds,. moisture,. CO ₂ and N ₂ .

The removal of sulfur compounds, i.e. desulphurisation in the desulphurisation section in the inlet unit 10, is solved by means of an adsorber 1, which operates on the basis of sulfane chemisorption on hydrated iron oxide. The residual concentration of H ₂ S at the outlet of the plant shall not exceed 2 to 3 mg / m ³ . The desulphurisation mass is replaced when the residual H ₂ S concentration increases to 7 mg / m ³ . This can be assumed for this device, with respect to the input H2S concentration changing over time, after 3 to 5 years of operation.

The vessel of the adsorber 1 has a volume of 6 m ³ , it is rectangular with a horizontal cross section of approx. 4 m ² and a height of 1.5 m. The height of the desulfurization material layer in the adsorber 1 is approx. 1 m. The required volume of desulfurization material is 4 m ³ . The desulphurisation mass is stored in a container in a removable basket fitted with a plastic net. The settling height above the bottom of the container is chosen so that the biogas enters the container under the basket. Above the layer of desulfurization material, a neck for biogas outlet opens into the vessel. The total height of the adsorber vessel 1 is therefore approx. 1.5 m. From above, the vessel is gas-tightly closed with a lid. In the bottom of the vessel, a sludge device is installed with a sludge outlet 12 of any condensate formed. The adsorber vessel 1 is mounted on a 0.5 m high base.

For higher output plants, up to 500 m ^{3 of} purified biogas / h, the use of a desulphurisation plant consisting of a pair of adsorbers L series applied shall apply. When the sulphane concentration in the purified biogas increases above 7 mg H ₂ S / m ³ , shut down the first adsorber 1 in the series. In it, the used desulphurisation mass is replaced by fresh. After replacing the desulphurisation, the device is connected

-8EN 306061 B6 so that the originally second adsorber 1 is then the first in the series and the originally first, now with fresh desulphurisation, is the second in the series. The connection of the device also enables the operation of one and parallel regeneration of the second shut down adsorber 1, by regeneration through the air passage supplied by the additional inlet H. The circuit diagram of the pair of adsorber 1, with the possibility of switching to serial or parallel operation, is shown in Fig. 2.

Performance of the basic unit of absorber 1 at the concentration of H ₂ S 1500 mg / m ^{3 of} biogas:

- at a filling height of 1 m ............... 116 m ³ / h

- at a filling height of 1.5 m ............ 175 m ³ / h.

Desulphurisation substance change cycle 9 to 10 months.

Other possible reports:

- 2 basic units connected in parallel

- output 232 (350) m ³ / h

- 3 basic units connected in parallel

- output 348 (525) m ³ / h.

Increasing the volume of CH ₄ and removing moisture (H ₂ O), CO ₂ and N ₂ (NH ₃ ) is solved within the combined equipment of container design with placement of machines and partial equipment on a steel supporting and fixing frame with a floor plan size of 4130 x 2300 mm.

Moisture removal is solved within the passage of desulfurized biogas through the adsorption mass in two separation columns supplemented by mechanical filters 32 with a permeability of 0.01 μ. In the first under a pressure of 0.01 MPa, in the second 0.8 MPa. The packing of each column 21 is 100 kg of crystalline CaCl ₂ , the exchange is planned every four months. A screw compressor 22 is inserted between the two columns 21, pressurizing the biogas to 0.8 MPa.

The predominant amount of CO ₂ is removed during the pressurization of desulphurised and dehumidified biogas by a four-stage mechanical compressor 31, where it leaves gradually after individual pressurization stages:

- 1st degree - 2 MPa

- 2nd degree - 3 MPa

- 3rd degree - 10.4 MPa

- 4th degree - 25.0 MPa.

As part of this pressurization, the volume of CH ₄ increases at the same time.

The compressor 31 is supplemented at the 1st pressure stage with two mechanical filters 32 with a permeability of 0.01 μ, a carbon filter 33 and two membrane separators 34 for separating N ₂ and CO ₂ . After passing through both filters, 17 to 25% of its volume, mainly CO _{2, is} separated from the biogas in the first separator. This volume is pressurized back into the biogas pipeline before it enters the cogeneration units. In the second separator, about 10% of its volume is separated, mainly CO ₂ . This volume is returned to the biogas treatment process in the dehumidification phase. The remaining 65 to 73% of the biogas volume goes to the second pressurization stage.

After the 2nd and 3rd pressure stage, the piston compressor 31 is equipped with a CO ₂ separator 35 with a replaceable mechanical filter, here a total of 2 pcs. The phase of CO ₂ and N ₂ (NH ₃ ) removal is completed by two final purification separators. The final removal of moisture is ensured by a separator 41 filled with crystalline CaCl ₂ , here 1 piece, and the final purification of CO ₂ and N ₂ (NH ₃ ) is ensured by a separator 42 filled with zeolite,

-9CZ 306061 B6 here also for example 1 pc. Within the 2nd and 3rd pressurization stage, 4 to 12% of its volume is removed from biogas, mainly CO2, within the subsequent final final purification, the residual amount of CO2, N ₂ (NH ₃ ) and H ₂ O is removed from the biogas in the range 1% of the original volume of biogas, ie here 45 m ^{1 * 3} . The volume of treated biogas represents 60% of the original volume of 27 m ³ .

Temperature mode of the device

As part of its treatment, the temperature of biogas is maintained at the level of the inlet temperature increased by 10 ° C, ie in winter 25 ° C, in summer 35 to 45 ° C. In the event that it is necessary to include a final dehumidifier as part of the final purification, cooling must be included in front of it in the plant, which will reduce the biogas temperature to 5 to 10 ° C.

The combined equipment also includes additional equipment for biogas cooling, pneumatic valve control and biogas quality measurement.

Behind the energy recovery of biogas within the pressure removal of CO ₂ , cooling is included, here the cooling device 43, because the temperature of the biogas increases up to about 45 ° C during its pressurization. The refrigeration unit works with freon refrigerant and its output is designed to cool biogas from 45 to 5 to 10 ° C. All valves installed in the biogas plant and other controls on this plant are pneumatically operated. In addition to the necessary compressed air distribution, an electric compressor with an outlet pressure of 0.6 to 0.8 MPa is designed as a source.

The pneumatic control necessary for extractive measurement can be dispensed with when using "in site" measurement, where the measuring probes are inserted directly into the gas pipeline of the device and are connected by cable to a separate evaluation unit, ie usually an analyzer completely separated from the measured medium.

Industrial applicability

The device according to the invention can be used for the conversion of biogas into a gas, generally referred to as biomethane, with a level of composition, calorific value and purity meeting the quality requirements for the quality of natural gas for the propulsion of internal combustion engines. It can also be used for analogous treatment of biogas for other purposes, where it is important to reduce the proportion of CO ₂ and N ₂ (NH ₃ ) and a certain degree of purification, but the most important area of application is the treatment of biogas for gas intended for internal combustion engines. The capacity of the plant in the exemplary embodiment can be modified to process up to 500 m ^{3 of} biogas / h, but in general it is also possible to create units of higher capacities, for example by the modular method.

Claims (8)

PATENT CLAIMS A plant for the treatment of biogas into a natural gas type fuel, comprising an inlet unit having the nature of a desulphurisation section, adapted for desulphurisation to a residual H ₂ S concentration of 2 to 7 mg / m ^{3 of} biogas, and a separation unit with a dewatering section adapted for dehumidification. up to a residual concentration of not more than 32 mg H2O / m ³ and with a separation section adapted for high-pressure CO2 separation in multiple pressure stages with outlet pressures from 0,5 to 14,8 MPa, adjusted to achieve a CH4 content of at least 95% by volume and to achieve not more than 2% by volume CO ₂ and 0 mg N ₂ (NH ₃ ) / kg, characterized in that the inlet unit (10), with the nature of a desulfurization section, is formed as a chemical separation column and / or as a washing column, with at least one adsorber (1) with a charge, the reactant of which is hydrated iron oxide, adapted for the passage of biogas and provided with an additional air supply (11) for regeneration of the charge and a sludge outlet (12) for condensate, and a dewatering section (20) contained in the separation unit. is formed as a dehumidification column, and the separation section (30) behind it is formed as a high-pressure CO ₂ separator with high-pressure CO ₂ separation and an increase in the CH ₄ volume fraction. Device according to Claim 1, characterized in that a storage and filling device (50) for filling transport pressure vessels or pressure tanks of vehicles or a distribution control station for the use of biogas as natural gas quality fuel is arranged downstream of the separation unit. Device according to one of Claims 1 or 2, characterized in that the high-pressure CO ₂ separator is designed as a high-pressure multistage compressor system (31), where a CO ₂ -based liquefied component separator (35) and an outlet from of the last stage of the high-pressure compressor (31) is connected to a filling device (50) for filling transport pressure vessels or pressure tanks of vehicles, where before this connection, a purification section (40) of produced biomethane is inserted within the separation unit. Device according to one of Claims 1 to 3, characterized in that the CO ₂ -based liquefied component separator comprises a fine mechanical filter (32), a carbon filter (33) and at least one membrane separator (34). Device according to one of Claims 1 to 4, characterized in that the gas outlet of the at least one membrane separator (34) is connected back to the drainage section (20) and / or to one of the lower stages of the compressor (31). Device according to one of Claims 1 to 5, characterized in that the purification section (40) is designed as a set of separation columns, namely as a set of at least one CaCl ₂ -filled final dehumidification column (41) and at least one column (42). final purification of CO ₂ and N ₂ (NH ₃ ) with zeolite filling. Device according to one of Claims 1 to 6, characterized in that the dewatering section (20) is formed by at least two separation columns (21) filled with CaCl ₂ and a fine mechanical filter (23) located in front of and behind the screw compressor (22). with an outlet pressure of 0.5 to 1 MPa. Device according to one of Claims 1 to 6, characterized in that the dewatering section (20) is designed as a dehumidification column comprising at least one chamber for heating the processed biogas and at least one cooling chamber provided with a cooling circuit and a sludge outlet for condensed dewatering. water.