DESC:
FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003

COMPLETE SPECIFICATION
(See section 10 and rule 13)
1. TITLE OF THE INVENTION
A SYSTEM AND PROCESS FOR OBTAINING DRY BIOGAS
2. APPLICANT(S)
NAME NATIONALITY ADDRESS
GPS RENEWABLES PVT. LTD. INDIAN PRESTIGE PINNACLE, NO. 113, 20TH MAIN ROAD, 3RD FLOOR, 7TH BLOCK, ADUGODI, KORAMANGALA, BANGALORE, KARNATAKA - 560034

3.PREAMBLE TO THE DESCRIPTION

THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE NATURE OF THIS INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED.

FIELD OF THE INVENTION
[0001] The present invention relates to a system and process for treating biogas. More particularly, it relates to a system and process for upgrading raw biogas to obtain dry biogas.

BACKGROUND OF THE INVENTION
[0002] Raw biogas is a combination of 40-60% methane, 30-50% carbon dioxide and a high concentration of water vapor (being ~30 & 150 g water per m³ gas) which amounts to 4-14 v/v% of the total biogas composition.
[0003] The presence of such a high concentration of water vapour in the raw biogas reduces the net calorific value of the biogas, thereby affecting the energy efficiency of the equipment such as but not limited to biogas engines and boilers where biogas is used as a fuel, as well as in the biogas upgradation systems wherein the moisture in the biogas can damage the equipment and affect their performance.
[0004] In some known methods of raw biogas upgradation where there is no removal of water, when ambient temperatures drop below the level of the biogas water dew point, the biogas cools, thereby causing the water vapour to condense in the pipeline carrying the raw biogas. The condensate so formed, combines with the carbon dioxide and hydrogen sulphide to form acidic compounds such as carbonic acid, sulphuric acid and ionic hydrogen, respectively that are highly corrosive in nature and accelerate the corrosion of the associated downstream equipment if not removed in a proper way.
[0005] In other methods of biogas upgradation, Alumina based dryers remove moisture by adsorption by the Alumina. However, such dryers need additional equipment thereby increasing the initial capital expenditure for the unit and the operating expenses.
[0006] The presence of free water in the raw biogas going to the membrane unit damages the equipment and reduces the life and efficiency of the purification system.
[0007] Thus, there is a need for a system and process which addresses and eliminates the aforesaid disadvantages of the prior art.

SUMMARY OF THE INVENTION

[0008] Accordingly, one or more embodiments of the present invention is to provide a system and process for obtaining dry biogas.
[0009] An embodiment of the present invention provides a system for obtaining dry biogas. The system comprises of a first vessel, configured to receive raw biogas from a biogas digester via an inlet and separate moisture from the raw biogas. The first vessel is provided with a valve at a base to drain moisture separated from the raw biogas. The system further comprises of a blower system, configured to pressurize the partially dried biogas received from the first vessel to a predetermined pressure. The system further comprises of a first temperature exchanger system, configured to lower the temperature of the compressed biogas received from the blower system to a predetermined temperature. The system further comprises of a second vessel, configured to separate moisture from the treated biogas received from the first temperature exchanger system. The second vessel is provided with a valve at a base to drain the moisture separated from the treated biogas. The system further comprises of a Hydrogen Sulphide (H2S) and Volatile Organic Compounds (VOC) removal system i.e. H2S and VOC removal system, configured to filter out impurities from the biogas received from the second vessel. The system further comprises of a third vessel, configured to separate moisture from the filtered biogas (also known as sweet biogas i.e. biogas without H2S) received from the H2S and VOC removal system. The third vessel is provided with a valve at a base to drain the moisture separated from the filtered biogas. The system further comprises of a compressor configured to compress the biogas received from the third vessel to a predetermined pressure. The system further comprises of a second temperature exchanger system, configured to lower the temperature of the compressed biogas received from the compressor and to reheat the biogas received from a fourth vessel. The system further comprises of a fourth vessel, configured to separate moisture from the biogas treated in the second temperature exchanger system and resend it to the second temperature exchanger system. The fourth vessel is provided with a valve at a base to drain the moisture separated from the cooled biogas received from the second temperature exchanger system. The system further comprises of an outlet, configured to receive dry biogas from the second temperature exchanger system and transfer it to an outlet tank.
[0010] An embodiment of the present invention provides a process for obtaining dry biogas, comprising the steps of receiving, at a first vessel, raw biogas via an inlet. The biogas is received by the first vessel from a biogas digester. The process further includes the step of condensing, at the first vessel, the raw biogas to separate moisture from the raw biogas to obtain the partially dried biogas. The separated moisture is drained from the first vessel via a valve. The process further includes the step of pressurizing, inside a blower system, the partially dried biogas received from the first vessel to obtain a biogas having a predetermined pressure. The process further includes the step of treating, at a first temperature exchanger system, the biogas received from the blower system. On treatment in the first temperature exchanger system, the biogas is cooled to a predetermined temperature. The process further includes the step of condensing, at a second vessel, the cooled biogas to separate moisture from the cooled gas. The separated moisture is drained from the second vessel via a valve. The process further includes the step of filtering, at a H2S and VOC removal system, the condensed biogas received from the second vessel to remove H2S and other impurities to obtain a filtered biogas (also known as sweet biogas). The process further includes the step of condensing, at a third vessel, the filtered biogas received from the H2S and VOC removal system to separate moisture from the filtered biogas. The separated moisture is drained from the third vessel via a valve. The process further includes the step of compressing, at a compressor, the biogas received from the third vessel to a predetermined pressure. The process further includes the step of treating, at a second temperature exchanger system, the compressed biogas received from the compressor, by lowering the temperature of the compressed biogas to a predefined temperature. The process further includes the step of condensing, at a fourth vessel, the cooled biogas, received from the second temperature exchanger system, to separate moisture from the biogas. The separated moisture is drained from the fourth vessel via a valve. The process further includes the process of re-heating, at the second temperature exchanger system, the biogas received from the fourth vessel to a pre-determined temperature to obtain dry biogas.
[0011] Other features and aspects of this invention will be apparent from the following description and the accompanying drawings. The features and advantages described in this summary and in the following detailed description are not all-inclusive, and particularly, many additional features and advantages will be apparent to one of ordinary skill in the relevant art, in view of the drawings, specification, and claims hereof. Moreover, it should be noted that the language used in the specification has been principally selected for readability and instructional purposes and may not have been selected to delineate or circumscribe the inventive subject matter, resort to the claims being necessary to determine such inventive subject matter.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The accompanying drawings, which are incorporated herein, and constitute a part of this disclosure, illustrate exemplary embodiments of the disclosed systems and processes in which like reference numerals refer to the same parts throughout the different drawings. Components in the drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the present disclosure. Some drawings may indicate the components using block diagrams and may not represent the internal circuitry of each component. It will be appreciated by those skilled in the art that disclosure of such drawings includes disclosure of connectors, components or parts, electrical components, electronic components or circuitry commonly used for working of the various components together as a system.
[0013] FIG. 1 is an exemplary block diagram of an environment for obtaining dry biogas according to one or more embodiments of the present invention.
[0014] FIG. 2 is an exemplary block diagram of a system for obtaining dry biogas, according to one or more embodiments of the present invention.
[0015] FIG. 3 is a schematic representation of the system, according to one or more embodiments of the present invention.
[0016] FIG. 4 is a schematic representation of the process for obtaining dry biogas according to one or more embodiments of the present invention.
[0017] The foregoing shall be more apparent from the following detailed description of the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0018] Some embodiments of the present disclosure, illustrating all its features, will now be discussed in detail. It must also be noted that as used herein and in the appended claims, the singular forms "a", "an" and "the" include plural references unless the context clearly dictates otherwise.
[0019] Various modifications to the embodiment will be readily apparent to those skilled in the art and the generic principles herein may be applied to other embodiments. However, one of ordinary skill in the art will readily recognize that the present disclosure including the definitions listed herein below are not intended to be limited to the embodiments illustrated but is to be accorded the widest scope consistent with the principles and features described herein.
[0020] A person of ordinary skill in the art will readily ascertain that the illustrated steps detailed in the figures and herein below are set out to explain the exemplary embodiments shown, and it should be anticipated that ongoing technological development will change the manner in which particular functions are performed. These examples are presented herein for purposes of illustration, and not limitation. Alternatives (including equivalents, extensions, variations, deviations, etc., of those described herein) will be apparent to persons skilled in the relevant art(s) based on the teachings contained herein. Such alternatives fall within the scope and spirit of the disclosed embodiments.
[0021] As per various embodiments depicted, the present invention discloses a system and process for obtaining dry biogas free from impurities.
[0022] Referring now to the drawings, where similar reference characters denote corresponding features consistently throughout the figures, there are shown preferred embodiments.
[0023] FIG. 1 is an exemplary block diagram of an environment 100 comprising of a system 104 for obtaining dry biogas, according to one or more embodiments of the present disclosure. In this regard, the environment 100 includes a biogas digester 102, a system 104 for obtaining dry biogas, and an outlet tank 106 to receive the dry biogas from the system 104 for obtaining dry biogas for further use in a membrane unit (not shown), all communicably coupled to each other.
[0024] The biogas digester 102 includes, by way of example but not limitation, a wet digester, dry digester, small scale digester, industrial digester, dry fermentation plant or landfill gas system. In an embodiment of the present invention, the small scale digester includes, by way of example but not limitation, fixed dome plant digester, floating drum plant digester, low-cost polyethylene tube digester, balloon plant digester, horizontal plant digester, earth-pit plant digester and ferro-cement plant digester. In another embodiment of the present invention, the industrial digester includes, by way of example but not limitation, batch plant digester, continuous plant digester, Continued Stirred Tank Reactor (CSTR), Upflow Anaerobic Sludge Blanket digester (UASB), Lagoon digester, Plug flow digester and Semi-batch plant digester. In an embodiment of the present invention, the raw biogas used for treatment in the system 104 for obtaining dry biogas is received from but not limited to, mesophilic or thermophilic or landfill gas systems.
[0025] The environment 100 further includes the system 104 for obtaining dry biogas, which is communicably coupled to the biogas digester 102 on its one side and to an outlet tank 106 on its other side. In particular, the system 104 for obtaining dry biogas is configured to treat raw biogas received from the biogas digester 102 and remove moisture and other impurities from the raw biogas to obtain dry biogas and transfer it to the outlet tank 106 for further use in critical equipment. In an embodiment of the present invention, the outlet tank 106 includes, by way of example but not limitation, CO2 removal units for e.g. membrane units; biogas engines; and biogas boilers.
[0026] Operational and construction features of the system 104 for obtaining dry biogas and the process adapted to obtain dry biogas will be explained in detail with respect to the following figures.
[0027] FIG. 2 is an exemplary block diagram of the system 104 for obtaining dry biogas, according to one or more embodiments of the present invention.

[0028] As per the illustrated embodiment, the system 104 for obtaining dry biogas is provided with an inlet 202 which receives raw biogas from the biogas digester 102 (shown in FIG.1). A first vessel 204 is configured to receive raw biogas from the biogas digester 102 via the inlet 202. On receiving the raw biogas, the first vessel 204 is adapted to separate moisture from the raw biogas.
[0029] In an embodiment of the present invention, the first vessel 204 is a condensation tank adapted to subject raw biogas to condensation and separate part of the moisture from the raw biogas to obtain partially dried biogas. The first vessel 204 is adapted to drain out the moisture separated from the raw biogas on condensation, from a valve 204a provided at a base of the first vessel 204. The valve 204a provided at a base of the first vessel 204 is selected from a manual valve or an automated valve. In a preferable embodiment of the present invention, the valve 204a is a manual drain valve with liquid seal arrangement.
[0030] The system 104 for obtaining dry biogas further includes a blower system 206 coupled to the first vessel 204. In an embodiment of the present invention, the blower system 206 is coupled to the first vessel 204 on one side and is configured to pressurize the partially dried biogas received from the first vessel 204 to a predetermined pressure. In a preferable embodiment of the present invention, the partially dried biogas in the blower system 206 is pressurized to 500 – 1000 mbarg. The resultant temperature of the partially dried biogas on being pressurized in the blower system 206 is 100-150?.
[0031] In an embodiment of the present invention, the blower system 206 includes only one blower. In an alternate embodiment, the blower system 206 includes one or more blowers, and only one blower of the one or more blowers of the blower system 206 is in use when the system 104 for obtaining dry biogas is in operation. The additional blowers of the one or more blowers of the blower system 206 aid in ensuring that there is no operational delay due to technical difficulties with an operational blower of the one or more blowers of the blower system 206. In another embodiment of the present invention, when the blower system 206 has more than one blower, the blowers are arranged either in series or parallel to each other. In an embodiment of the present invention, the one or more blowers in the blower system 206 include, by way of example but not limitation, centrifugal blower, positive displacement blower, axial flow blower, high-speed blower, regenerative blower, blower with variable frequency drive (VFD) and blower without VFD.
[0032] Further, as per the illustrated embodiment, the system 104 for obtaining dry biogas includes a first temperature exchanger system 208 coupled to the blower system 206. Thus, the blower system 206 is coupled to the first vessel 204 on one side and to the first temperature exchanger system 208 on another side. In an embodiment of the present invention, the first temperature exchanger system 208 is coupled to the blower system 206 on one side and is configured to lower the temperature of the pressurized biogas received from the blower system 206 to a predetermined temperature. In a preferable embodiment of the present invention, the temperature of the pressurized gas is lowered to 12-22? in the first temperature exchanger system 208.
[0033] In an embodiment of the present invention, the first temperature exchanger system 208 includes a single heat exchanger. In an alternate embodiment of the present invention, the first temperature exchanger system 208 includes one or more heat exchangers. In an embodiment of the invention, the more than one heat exchangers of the first temperature exchanger system 208 are arranged either in series or parallel to each other. In an embodiment of the present invention, the one or more heat exchangers in the first temperature exchanger system 208 are selected from but not limited to, gas to liquid heat exchanger and gas to gas heat exchanger. The cooling means used inside the gas to liquid heat exchanger of the first temperature exchanger system 208 includes, by way of example but not limitation, one or more of, water, glycol, ammonia, and other known organic and inorganic chemicals and synthetic refrigerants, used either independently or in combination. In another embodiment, the one or more heat exchangers inside the first temperature exchanger system 208 uses a cooling system known in the art, without deviating from the scope of the present disclosure.
[0034] In an embodiment of the present invention, the system 104 for obtaining dry biogas further includes a second vessel 210, coupled to the first temperature exchanger system 208. Thus, the first temperature exchanger system 208 is coupled to the blower system 206 on one side and to the second vessel 210 on another side. In an embodiment of the present invention, the second vessel 210 is coupled to the first temperature exchanger system 208 on one side and is configured to separate moisture from the partially cooled biogas received from the first temperature exchanger system 208. In a preferable embodiment of the present invention, the second vessel 210 is a condensation tank adapted to separate moisture from the partially cooled biogas by subjecting it to condensation. The second vessel 210 is further adapted to drain out the moisture separated from the biogas on condensation, by means of a valve 210a provided at a base of the second vessel 210. The valve 210a provided at a base of the second vessel 210 is selected from a manual valve or an automated valve. In a preferable embodiment of the present invention, the valve 210a is an automated drain valve.
[0035] In an embodiment of the present invention, the system 104 for obtaining dry biogas further includes a Hydrogen Sulphide (H2S) and Volatile Organic Compounds (VOC) removal system 212 coupled to the second vessel 210. Thus, the second vessel 210 is coupled to the first temperature exchanger system 208 on one side and to the H2S and VOC removal system 212 on another side. In an embodiment of the present invention, the H2S and VOC removal system 212 is coupled to the second vessel 210 on one side and is configured to receive the biogas from the second vessel 210 and filter out impurities such as H2S, CO2 and other volatile organic compounds from the biogas received from the second vessel 210. In an embodiment of the present invention, the H2S and VOC removal system 212 includes one filter unit. In an alternate embodiment of the present invention, the H2S and VOC removal system 212 includes one or more filter units and only one filter unit of the one or more filter units of the H2S and VOC removal system 212 is in use when the system 104 for obtaining dry biogas is in operation. The additional filter units of the one or more filter units of the H2S and VOC removal system 212 aid in ensuring that there is no operational delay due to technical difficulties with an operational filter unit of the one or more filter units of the H2S and VOC removal system 212. In an embodiment of the present invention, when H2S and VOC removal system 212 has more than one filter units, the filter units are arranged either in series or parallel to each other.
[0036] In an embodiment of the present invention, the one or more filter units in the H2S and VOC removal system 212 include, by way of example but not limitation, activated carbon media filters or iron hydroxide media filters. In an embodiment of the present invention wherein the filter units in the H2S and VOC removal system 212 are activated carbon media filters or iron hydroxide media filters, the system 104 is provided with an independent heat exchanger 212a (shown in FIG.3) configured to reheat the biogas received from the second vessel 210, before filtration in the H2S and VOC removal system 212. The embodiment of the system 104 using the independent heat exchanger 212a (shown in FIG.3) and its configuration will be explained in detail with reference to FIG. 3.
[0037] In an embodiment of the present invention, the system 104 for obtaining dry biogas further includes a third vessel 214 coupled to the H2S and VOC removal system 212. Thus, the H2S and VOC removal system 212 is coupled to the second vessel 210 on one side and to the third vessel 214 on another side. In an embodiment of the present invention, the third vessel 214 is coupled to the H2S and VOC removal system 212 on one side and is configured to receive the filtered biogas from the H2S and VOC removal system 212, and separate moisture from the filtered biogas. In a preferable embodiment of the present invention, the third vessel 214 is a condensation tank adapted to separate moisture from the filtered biogas by subjecting it to condensation. The third vessel 214 is further adapted to drain out the moisture separated from the filtered biogas on condensation, by means of a valve 214a provided at a base of the third vessel 214. The valve 214a provided at a base of the third vessel 214 is selected from a manual valve or an automated valve. In a preferable embodiment of the present invention, the valve 214a is a manual drain valve.
[0038] In an embodiment of the present invention, the system 104 for obtaining dry biogas further includes a compressor 216 coupled to the third vessel 214. Thus, the third vessel 214 is coupled to the H2S and VOC removal system 212 on one side and to the compressor 216 on another side. In an embodiment of the present invention, the compressor 216 is coupled to the third vessel 214 on one side and is configured to compress the biogas received from the third vessel 214 to a predetermined pressure. In a preferable embodiment of the present invention, the compressor 216 used in the system 104 for obtaining dry biogas includes, by way of example but not limitation, centrifugal compressor, axial compressor, reciprocating compressor, screw compressor, water cooled compressor, oil free compressor, oil cooled compressor, single stage compressor, multi-stage compressor, compressor with VFD, compressor without VFD and liquid ring compressor. In an embodiment of the present invention, the biogas in the compressor 216 is compressed from 200-400 mbarg to 10-15barg. Compression of the biogas causes resultant increase in the temperature of the biogas to 130-160?, thereby releasing a warm biogas.
[0039] In an embodiment of the present invention, the system 104 for obtaining dry biogas further includes a second temperature exchanger system 218 coupled to the compressor 216. Thus, the compressor 216 is coupled to the third vessel 214 on one side and to the second temperature exchanger system 218 on another side. In an embodiment of the present invention, the second temperature exchanger system 218 is coupled to the compressor 216 on one side and is configured to lower the temperature of the biogas received from the compressor 216 to a predetermined temperature. In a preferable embodiment of the present invention, the temperature of the biogas received from the compressor 216 is lowered to 5-12? in the second temperature exchanger system 218.
[0040] In an embodiment of the present invention, the second temperature exchanger system 218 includes one heat exchanger. In alternate embodiment of the present invention, the second temperature exchanger system 218 includes one or more heat exchangers. In an embodiment of the present invention, the one or more heat exchangers in the second temperature exchanger system 218 are selected from but not limited to, gas to liquid heat exchanger and gas to gas heat exchanger. The cooling means used inside the gas to liquid heat exchanger of the second temperature exchanger system 218 includes, by way of example but not limitation, one or more of, water, glycol, ammonia, and other known organic and inorganic chemicals and synthetic refrigerants, used either independently or in combination. In another embodiment, the heat exchangers inside the second temperature exchanger system 218 use a cooling system known in the art, without deviating from the scope of the present disclosure. The use of more than one type of heat exchanger in combination with each other in the second temperature exchanger system 218 aids in reducing the overall utilization of power. Further, the use of more than one heat exchanger in the second temperature exchanger system 218 also allows the use of lower capacity heat exchangers, thereby further reducing power consumption by the system 104 for obtaining dry biogas. In an embodiment of the invention, the more than one heat exchangers of the second temperature exchanger system 218 are arranged either in series or parallel to each other.
[0041] In an embodiment of the present invention, the second temperature exchanger system 218 is also coupled to a fourth vessel 220. The fourth vessel 220 is configured to receive the cooled biogas from the second temperature exchanger system 218 and separate moisture from the cooled biogas. In a preferable embodiment of the present invention, the fourth vessel 220 is a condensation tank adapted to separate moisture from the cooled biogas by subjecting it to condensation. The fourth vessel 220 is further adapted to drain out the moisture separated from the biogas on condensation, by means of a valve 220a provided at a base of the fourth vessel 220. The valve 220a provided at a base of the fourth vessel 220 is selected from a manual valve or an automated valve. In a preferable embodiment of the present invention, the valve 220a is an automated drain valve. In an embodiment of the present invention, the fourth vessel 220 is also configured to resend the biogas treated inside the fourth vessel 220 back to the second temperature exchanger system 218 for the purpose of re-heating the treated biogas to obtain dry biogas.
[0042] In an embodiment of the present invention, the second temperature exchanger system 218 is also configured to receive treated biogas from the fourth vessel 220, and re-heat the biogas to a predetermined temperature above the biogas water dewpoint to prevent condensation. In an embodiment of the present invention, the biogas from the fourth vessel 220 is re-heated in the second temperature exchanger system 218 to 22-32?. The biogas so obtained at this stage is dry biogas.
[0043] In an embodiment of the present invention, the second temperature exchanger system 218 is also configured to release the dry biogas in an outlet tank 106 (shown in FIG.1) via an outlet 222. The biogas transferred through the outlet 222 is virtually free of Hydrogen Sulphide and has less than or equal to 1000ppm of moisture which can then be passed through the membrane units.
[0044] In an embodiment of the present invention, the system 104 for obtaining dry biogas includes an oil filter (not shown) configured to remove oil or at least reduce oil concentration levels from the biogas received from the fourth vessel 220 before re-heating the biogas in the second temperature exchanger system 218. The concentration of the oil in the dry biogas after filtering the biogas through the oil filter is substantially reduced from the initial concentration of the oil in the biogas down to 0.0085 mg/NM3. In a preferable embodiment of the present invention, the temperature inside the oil filter is maintained at 5-12?.
[0045] FIG. 3 illustrates a schematic diagram according to a preferred embodiment of the present invention. As mentioned earlier in FIG. 2, the system 104 for obtaining dry biogas of the present invention is provided with inlet 202 which receives raw biogas from a biogas digester 102 (shown in FIG. 1). As per the illustrated embodiment, the system 104 further includes a first vessel 204, a blower system 206 and a first temperature exchanger system 208. The operations and functions of the first vessel 204, the blower system 206, and the first temperature exchanger system 208 are already explained in FIG. 2. For the sake of brevity, a similar description related to the working and operation of the system 104 for obtaining dry biogas as illustrated in FIG. 2 has been omitted to avoid repetition. The limited description provided for the system 104 for obtaining dry biogas in FIG. 3 should be read with the description as provided for the system 104 for obtaining dry biogas in FIG. 2 above and should not be construed as limiting the scope of the present disclosure.
[0046] In a preferable embodiment of the present invention, as illustrated in FIG. 3, the first temperature exchanger system 208 of the system 104 for obtaining dry biogas includes two heat exchangers 208a and 208b, configured to lower the temperature of the biogas received from the blower system 206. Two heat exchangers are used in the first temperature exchanger system 208 instead of one heat exchanger as an alternate embodiment, to reduce the overall utilization of power, as two lower capacity heat exchangers may be used. The heat exchangers 208a and 208b collectively form the first temperature exchanger system 208 shown in FIG. 2. In particular, the heat exchanger 208a is coupled to the blower system 206 on one side and to heat exchanger 208b on the other side. The heat exchanger 208a is configured to receive the pressurized gas from the blower system 206 and lower the temperature of such biogas to a first predetermined temperature. The heat exchanger 208b is configured to receive the biogas from heat exchanger 208a and further lower the temperature of the biogas to a second predetermined temperature.
[0047] In an embodiment of the present invention, the two heat exchangers 208a and 208b are gas to liquid heat exchangers. The features of the gas to liquid heat exchangers forming the first temperature exchanger system 208 are already explained in FIG. 2. Hence, for the sake of brevity, a similar description related to the working and operation of the system 104 for obtaining dry biogas as illustrated in FIG. 2 has been omitted to avoid repetition. The limited description provided for the system 104 for obtaining dry biogas in FIG. 3 should be read with the description as provided for the system 104 for obtaining dry biogas in FIG. 2 above and should not be construed as limiting the scope of the present disclosure. In an embodiment of the present invention, the heat exchangers 208a and 208b of the first temperature exchanger system 208 are communicably coupled to each other in series.
[0048] The system 104 for obtaining dry biogas as illustrated in FIG. 3 further includes a second vessel 210, coupled to the heat exchanger 208b of the first temperature exchanger system 208 and is configured to receive the partially cooled biogas from the heat exchanger 208b of the first temperature exchanger system 208 and separate moisture from the partially cooled biogas. Thus, the heat exchanger 208b of the first temperature exchanger system 208 is coupled to heat exchanger 208a of the first temperature exchanger system 208 on one side and to the second vessel 210 on the other side. In a preferable embodiment of the present invention, the second vessel 210 is a condensation tank wherein the moisture from the biogas is separated by subjecting it to condensation. The separated moisture is drained out of the second vessel 210 from the valve 210a provided at the base of the second vessel 210. The valve 210a provided at the base of the second vessel 210 is selected from a manual valve or an automated valve. In a preferable embodiment of the present invention, the valve 210a is an automated valve.
[0049] In an embodiment of the present invention, as illustrated in FIG. 3, the system 104 for obtaining dry biogas includes an H2S and VOC removal system 212 comprising of two filter units i.e. 212b and 212c. In an embodiment of the present invention, the two filter units 212b and 212c of the H2S and VOC removal system 212 are either activated carbon media filters or iron hydroxide media filters and are configured to filter out impurities from the biogas released from the second vessel 210. When activated carbon media filters or iron hydroxide filters are used for filtering out H2S, CO2 and other volatile organic compounds (VOC), the temperature of the biogas must preferably be in the range of 19-29? to maintain a predetermined relative humidity. Thus, in a preferable embodiment of the present invention, the system 104 for obtaining dry biogas is provided with an independent heat exchanger 212a coupled to the second vessel 210 on one side and to the H2S and VOC removal system 212 on the other side, such that it is configured to receive partially treated biogas from second vessel 210 and re-heat the partially treated biogas to a predetermined temperature, preferably in the range of 19-29?. This re-heated biogas is suitable for filtration through activated carbon media filters or iron hydroxide media filters in the H2S and VOC removal system 212. In an embodiment of the present invention, the independent heat exchanger 212a is selected from but not limited to, gas to liquid heat exchanger and gas to gas heat exchanger. In a preferable embodiment of the present invention, the heat exchanger 212a is a gas to liquid heat exchanger. The re-heating of the biogas in the independent heat exchanger 212a is achieved by means of circulating hot water through the independent heat exchanger 212a. In another embodiment, the independent heat exchanger 212a uses a mechanism for re-heating the biogas known in the art, without deviating from the scope of the present disclosure. As discussed above, the independent heat exchanger 212a is introduced in the system 104 only when the type of filters used in the H2S and VOC removal system 212 necessitates that the biogas is of a temperature higher than that of the biogas after treatment in the second vessel 210.
[0050] The system 104 for obtaining dry biogas further includes a third vessel 214 provided with a valve 214a at its base, a compressor 216 and a second temperature exchanger system 218, communicably coupled to each other. The operations and functions of the third vessel 214, the compressor 216 and the second temperature exchanger system 218 are already explained in FIG. 2. For the sake of brevity, a similar description related to the working and operation of the system 104 for obtaining dry biogas as illustrated in FIG. 2 has been omitted to avoid repetition. The limited description provided for the system 104 for obtaining dry biogas in FIG. 3 should be read with the description as provided for the system 104 for obtaining dry biogas in FIG. 2 above and should not be construed as limiting the scope of the present disclosure.
[0051] In an embodiment of the present invention, as illustrated in FIG. 3, the second temperature exchanger system 218 of the system 104 for obtaining dry biogas includes three heat exchangers 218a, 218b and 218c each of which is configured to lower the temperature of the biogas received from the compressor 216, and which collectively form the second temperature exchanger system 218 (shown in FIG. 2). In particular, a first heat exchanger 218a of the second temperature exchanger system 218 is coupled to the compressor 216 on one side and to the second heat exchanger 218b of the second temperature exchanger system 218 on the other side. The first heat exchanger 218a of the second temperature exchanger system 218 is configured to receive the compressed biogas from the compressor 216 and lower the temperature of such biogas to a first predetermined temperature. This partially cooled biogas passes from the first heat exchanger 218a of the second temperature exchanger system 218 to the second heat exchanger 218b of the second temperature exchanger system 218. The second heat exchanger 218b of the second temperature exchanger system 218 is further coupled to the third heat exchanger 218c of the second temperature exchanger system 218. The second heat exchanger 218b of the second temperature exchanger system 218 is configured to receive the partially cooled biogas from the first heat exchanger 218a of the second temperature exchanger system 218 and lower the temperature of the biogas further to a second predetermined temperature. This further cooled biogas passes from the second heat exchanger 218b of the second temperature exchanger system 218 to the third heat exchanger 218c of the second temperature exchanger system 218. The third heat exchanger 218c of the second temperature exchanger system 218 is configured to receive the further cooled biogas from the second heat exchanger 218b of the second temperature exchanger system 218 and lower the temperature of the biogas further to a third predetermined temperature. In an embodiment of the present invention, the first heat exchanger 218a, second heat exchanger 218b and third heat exchanger 218c of the second temperature exchange system 218 are selected from but not limited to, gas to liquid heat exchanger and gas to gas heat exchanger. In a preferable embodiment of the present invention, the first heat exchanger 218a and third heat exchanger 218c of the second temperature exchanger system 218 are gas to liquid heat exchangers and the second heat exchanger 218b of the second temperature exchanger system 218 is a gas to gas heat exchanger. The aforesaid selection of the heat exchangers in the second temperature exchanger system 218 aid in lowering the energy and cool water consumption by the system 104 for obtaining dry biogas. The operations and functions of the first heat exchanger 218a, second heat exchanger 218b and third heat exchanger 218c forming the second temperature exchanger system 218 are already explained in FIG. 2. Hence, for the sake of brevity, a similar description related to the working and operation of the system 104 for obtaining dry biogas as illustrated in FIG. 2 has been omitted to avoid repetition. The limited description provided for the system 104 for obtaining dry biogas in FIG. 3 should be read with the description as provided for the system 104 for obtaining dry biogas in FIG. 2 above and should not be construed as limiting the scope of the present disclosure. In a preferable embodiment of the invention, the first heat exchanger 218a, second heat exchanger 218b and third heat exchanger 218c of the second temperature exchanger system 218 are arranged in series.
[0052] The system 104 for obtaining dry biogas, as illustrated in FIG. 3, further includes a fourth vessel 220, coupled to the third heat exchanger 218c of the second temperature exchanger system 218 and is configured to receive the cooled biogas from the third heat exchanger 218c of the second temperature exchanger system 218 and separate the moisture from such cooled biogas. In an embodiment of the present invention, the fourth vessel 220 is a condensation tank wherein the cooled biogas is subjected to condensation to separate the moisture from the biogas. The separated moisture is drained out of the fourth vessel 220 by means of valve 220a provided at the base of the fourth vessel 220. In an embodiment of the present invention, the valve 220a is a level operated automated valve. The use of manual valves 204a and 214a in the first vessel 204 and third vessel 214 respectively and the use of automated valves 210a and 220a in the second vessel 210 and fourth vessel 220 respectively, is only to reduce the consumption of energy by the system. Alternatively, all four vessels of the system 104 i.e. first vessel 204, second vessel 210, third vessel 214 and fourth vessel 220 may use either automated valves or manual valves or any combination of the said valves.
[0053] In an embodiment of the present invention, as illustrated in FIG. 3, the second heat exchanger 218b of the second temperature exchanger system 218 is also configured to receive the treated biogas from the fourth vessel 220 and re-heat the biogas to obtain a dry biogas having a predetermined temperature above the biogas water dewpoint to prevent condensation. In an embodiment of the present invention, the treated biogas from the fourth vessel 220 is re-heated in the gas to gas heat exchanger 218b of the second temperature exchanger system 218 preferably to 22-32?. In an embodiment of the present invention, the second heat exchanger 218b of the second temperature exchanger system 218 comprises of a piping system comprising of two pipes (not shown) i.e. one pipe for receiving the partially cooled biogas from the first heat exchanger 218a of the second temperature exchanger system 218 and the other pipe for receiving treated biogas from the fourth vessel 220. The heating media for re-heating the treated biogas received from the fourth vessel 220 is the biogas received in the pipe from the first heat exchanger 218a of the second temperature exchanger system 218 which is at a temperature of about 40-45?. The two pipes in the second heat exchanger 218b are in close proximity to each other to enable an exchange of temperature between the biogas passing through the two pipes i.e. the biogas released from the first heat exchanger 218a of the second temperature exchanger system 218 and received by the second heat exchanger 218b of the second temperature exchanger system 218 passing through in one pipe and the biogas received in the second pipe of the second heat exchanger 218b of the second temperature exchanger system 218 from the fourth vessel 220. This exchange of heat results in re-heating of the treated biogas received from the fourth vessel 220. The re-heated biogas has a temperature in the range of 22-32?, making it suitable for use in membrane units.
[0054] The second heat exchanger 218b of the second temperature exchanger system 218 is further configured to release the dry biogas to an outlet tank 106 (shown in FIG. 1) via outlet 222.
[0055] The present invention further discloses a process for obtaining dry biogas free from impurities. FIG. 4 is a schematic representation of the process 400 for obtaining dry biogas according to one or more embodiments of the present invention. For the purpose of description, the process 400 for obtaining dry biogas is described with the embodiments as illustrated in FIG. 2 and FIG. 3 and should nowhere be construed as limiting the scope of the present disclosure.
[0056] At step 402, the process 400 includes the step of receiving, at a first vessel 204, raw biogas via an inlet 202, wherein the biogas is received from a biogas digester 102.
[0057] At step 404, the process 400 includes the step of condensing, at the first vessel 204, the raw biogas to separate moisture from the raw biogas to obtain the partially dried biogas, wherein the separated moisture is drained from the first vessel 204 via a valve 204a. In an embodiment of the present invention, the valve 204a is a manual valve with a liquid seal.
[0058] At step 406, the process 400 includes the step of pressurizing, inside a blower system 206, the partially dried biogas received from the first vessel 204 to obtain a biogas having a predetermined pressure. In a preferable embodiment of the present invention, the biogas in the blower system 206 is pressurized to have pressure in the range of 500 – 1000 mbarg. The resultant temperature of the biogas on being pressurized in the blower system 206 is 100-150?. The pressure of the biogas in the range of 500 – 1000 mbarg is essential if it has to be filtered through the H2S and VOC removal system (described in FIG. 2 and FIG. 3). However, for filtration of the biogas in the H2S and VOC removal system 212, the moisture level in the biogas is also required to be low. Hence, for the separation of moisture from the biogas released from the blower system 206, the biogas is required to be cooled.
[0059] At step 408, the process 400 includes the step of treating, at a first temperature exchanger system 208, the biogas received from the blower system 206, wherein on treatment, the biogas is cooled to a predetermined temperature. In an embodiment of the present invention, the temperature of the biogas received from the blower system 206 is cooled to 12-22? and preferably to 17? in the first temperature exchanger system 208. In a preferable embodiment of the present invention, the temperature of the biogas received from the blower system 206 is lowered to a first predetermined temperature in the range of 40-50?, and preferably 45? by passing it through the heat exchanger 208a (shown in FIG. 3) of the first temperature exchanger system 208. The temperature of the cooled biogas received from heat exchanger 208a of the first temperature exchanger system 208 is thereafter further lowered to a second predetermined temperature in the range of 12-22?, and preferably to 17? by passing it through the heat exchanger 208b of the first temperature exchanger system 208. Both heat exchangers 208a and 208b collectively form the first temperature exchanger system 208.
[0060] At step 410, the process 400 includes the step of condensing, at a second vessel 210, the cooled biogas received from the first temperature exchanger system 208 to separate moisture from the cooled biogas, wherein the separated moisture is drained from the second vessel via the valve 210a. In an embodiment of the present invention, the valve 210a is an automated valve.
[0061] At step 412, the process 400 includes the step of filtering, at an H2S and VOC removal system 212, the condensed biogas received from the second vessel 210 to remove Hydrogen Sulphide (H2S), VOC and other impurities to obtain a filtered biogas (also known as sweet biogas). In an embodiment of the present invention, prior to the step of filtration of the biogas, the process 400 includes the step of re-heating the biogas (not shown) received from the second vessel 210 in the independent heat exchanger 212a to a predetermined temperature, suitable for maintaining the humidity while passing through the activated carbon media filters or iron hydroxide media filters of the H2S and VOC removal system 212. For the effective filtration of the biogas through the activated carbon media filters or the iron hydroxide media filters, the H2S and VOC removal system 212 requires the temperature of the biogas to be in the range of 19-29?, and preferably 24?. The temperature of the biogas released from the second vessel 210 is lower than the above temperature range and hence re-heating the biogas to make it suitable for use in the activated carbon media filters or the iron hydroxide media filters is necessitated. When the H2S and VOC removal system 212 uses filters other than activated carbon media filters or iron hydroxide media filters, the step of re-heating of the biogas received from the second vessel 210 is eliminated.
[0062] At step 414, the process 400 includes the step of condensing, at a third vessel 214, the filtered biogas received from the H2S and VOC removal system 212 to separate moisture from the filtered gas, wherein the separated moisture is drained from the third vessel via valve 214a. In an embodiment of the present invention, the valve 214a is a manual valve.
[0063] At step 416, the process 400 includes the step of compressing, at a compressor 216, the condensed biogas received from the third vessel 214 to a predetermined pressure. In an embodiment of the present invention, the biogas in the compressor 216 is compressed from 200-400 mbarg to 10-15barg. The pressure 10-15barg of the biogas is suitable for use in membrane units and any other critical equipment using biogas. The compression of the biogas in the compressor 216 causes resultant increase in the temperature of the biogas to 130-160?. This necessitates cooling of the biogas to eliminate further moisture from the biogas.
[0064] At step 418, the process 400 includes the step of treating, at a second temperature exchanger system 218, the biogas received from the compressor 216, wherein on treatment, the biogas is cooled to a predetermined temperature. In an embodiment of the present invention, the temperature of the biogas received from the compressor 216 is cooled to 5-12? in the second temperature exchanger system 218. In a preferable embodiment of the present invention, the step of cooling of the biogas in the second temperature exchanger system 218 is divided into three steps of cooling. In particular, the process 400 at step 418 includes a first step of lowering the temperature of the biogas received from the compressor 216 to a first predetermined temperature preferably in the range of 40-50?, and more preferably to 45? by passing it through a first heat exchanger 218a (shown in FIG. 3) of the second temperature exchanger system 218. The process 400 at step 418 further includes a second step of lowering the temperature of the biogas received from the first heat exchanger 218a of the second temperature exchanger system 218 to a second predetermined temperature, preferably in the range of 25-35?, and more preferably to 30? by passing it through the second heat exchanger 218b (shown in FIG. 3) of the second temperature exchanger system 218. The process 400 at step 418 further includes a third step of lowering temperature of the biogas received from the second heat exchanger 218b of the second temperature exchanger system 218 to a third predetermined temperature, preferably in the range of 5-12?, and more preferably to 10? by passing it through the third heat exchanger 218c (shown in FIG. 3) of the second temperature exchanger system 218. The first heat exchanger 218a, second heat exchanger 218b and third heat exchanger 218c collectively form the second temperature exchanger system 218. The division of the step of cooling of the biogas into three sub-steps to achieve the preferred temperature range of 5-12? is adapted to reduce the consumption of water and power used for cooling the biogas.
[0065] At step 420, the process 400 includes the step of condensing, at a fourth vessel 220, the cooled biogas, received from the second temperature exchanger system 218, to separate moisture from the biogas, wherein the separated moisture is drained from the fourth vessel 220 via valve 220a. In an embodiment of the present invention, the valve 220a is an automated valve.
[0066] In an alternate embodiment of the present invention, the process 400 includes the step of filtering (not shown), at an oil filter (not shown), the cooled biogas received from the fourth vessel 220 to filter out oil from the biogas. The step of filtration of the biogas through an oil filter is implemented in the event that the compressor 216 of the system 104 for obtaining dry biogas is an oil injected compressor. The step of filtration brings the initial concentration of oil in the biogas down to 0.0085 mg/NM3. The temperature inside the oil filter is maintained in the range of 5-12?.
[0067] At step 422, the process 400 includes the step of re-heating, at the second temperature exchanger system 218, the biogas received from the fourth vessel 220, to a predetermined temperature to obtain dry biogas. In a preferable embodiment of the present invention, the biogas is re-heated to a temperature in the range of 22-32?, and preferably to 28?.
[0068] At step 424, the process 400 includes the step of releasing, from the second temperature exchanger system 218, the dry biogas to an outlet tank 106 by means of outlet 222.
[0069] The dry biogas obtained by way of the present invention has a temperature well above its water dew point, which will not condense and generate free water to damage the membranes even if there is a large fluctuation in the ambient temperature.
[0070] The advantage of dehumidification and removal of water vapour by the process of the present invention is that the dry biogas obtained in the present invention has moisture content of 1000ppm or lower thereby increasing the methane content and consequently increasing the calorific value of the biogas. Efficient dehumidification reduces the concentration of contaminants in the biogas such as sulphur dioxide, siloxanes, and volatile liquid compounds that do not biodegrade easily on the one hand, and ammonia and halogen compounds such as chlorides and fluorides, each of which dissolve in condensed water. The removal of such contaminants reduces corrosion and improves the efficiency of the downstream equipment such as but not limited to CHP plant, gas pipeline that uses biogas.
[0071] Further, the system and the process of the present invention provide an automated procedure for obtaining dry biogas thereby reducing manual interference resulting in ease of operation. Particularly, the continuous draining out of moisture from the four vessels of the system advantageously enable effective maintenance of the system. The present invention also permits modularisation.
[0072] The system and process of the present invention are efficient for removal of water from the biogas and heat recovery, and the equipment used is agnostic. It uses pressurized gas for chilling the biogas to dew point of -65? instead of using a refrigerant to actually cool down the biogas to -65?, while achieving the same impact due to use of pressurised gas and series of heat exchangers.
[0073] The present invention offers multiple advantages over the prior art and the above listed are a few examples to emphasize on some of the advantageous features. The listed advantages are to be read in a non-limiting manner.
[0074] The foregoing description of the invention has been set merely to illustrate the invention and is not intended to be limiting. Since, modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to a person skilled in the art, the invention should be construed to include everything within the scope of the appended claims.

REFERENCE NUMERALS
[0075] Environment- 100
[0076] Biogas Digester- 102
[0077] System for obtaining dry biogas- 104
[0078] Outlet tank- 106
[0079] Inlet- 202
[0080] First vessel- 204
[0081] Valve of the first vessel- 204a
[0082] Blower system- 206
[0083] First temperature exchanger system- 208
[0084] Heat exchangers of the first temperature exchanger system- 208a and 208b
[0085] Second vessel- 210
[0086] Valve of the second vessel- 210a
[0087] H2S and VOC removal system- 212
[0088] Independent heat exchanger- 212a
[0089] Filter units of the H2S and VOC removal system- 212b and 212c
[0090] Third vessel- 214
[0091] Valve of the third vessel- 214a
[0092] Compressor- 216
[0093] Second temperature exchanger system- 218
[0094] First heat exchanger of the second temperature exchanger system- 218a
[0095] Second heat exchanger of the second temperature exchanger system- 218b
[0096] Third heat exchanger of the second temperature exchanger system- 218c
[0097] Fourth vessel- 220
[0098] Valve of the fourth vessel- 220a
[0099] Outlet- 222
,CLAIMS:CLAIMS
We Claim:
1. A system 104 for obtaining dry biogas, the system comprising of
an inlet 202 to receive raw biogas from a biogas digester;
a first vessel 204, configured to receive raw biogas from the inlet 202, wherein the first vessel 204 is provided with a valve 204a at a base to drain water separated from the raw biogas;
a blower system 206, configured to compress the partially dried biogas received from the first vessel 204;
a first temperature exchanger system 208, configured to lower the temperature of the compressed biogas received from the blower system 206;
a second vessel 210, configured to separate moisture from the biogas treated in the first temperature exchanger system 208, wherein the second vessel 210 is provided with a valve 210a at a base to drain water separated from the treated biogas;
an H2S and VOC removal system 212, configured to filter out impurities from the biogas received from the second vessel 210;
a third vessel 214, configured to separate moisture from the biogas received from the H2S and VOC removal system 212, wherein the third vessel 214 is provided with a valve 214a at a base to drain moisture separated from the filtered biogas;
a compressor 216, configured to compress the biogas received from the third vessel 214 to a predetermined pressure;
a second temperature exchanger system 218, configured to lower the temperature of the compressed biogas received from the compressor 216 and wherein the second temperature exchanger system 218 is also adapted to re-heat the dry biogas;
a fourth vessel 220, configured to separate moisture from the biogas treated in the second temperature exchanger system 218 and adapted to resend the cooled biogas to the second temperature exchanger system 218 for re-heating, wherein the fourth vessel is provided with a valve 220a at a base to drain water separated from the cooled biogas received from the second temperature exchanger system 218;
an outlet 222, configured to receive the dry biogas from the second temperature exchanger system and release it to an outlet tank 106
2. The system 104 as claimed in Claim 1, wherein the blower system comprises of one or more blowers arranged in series or parallel to each other.

3. The system 104 as claimed in Claim 1, wherein an independent heat exchanger 212a is coupled to the second vessel 210 on its one side and to the H2S and VOC removal system 212 on its other side and is configured to re-heat the biogas received from the second vessel 210.

4. The system 104 as claimed in Claim 1, wherein the first temperature exchanger system 208 and second temperature exchanger system 218 comprise of one or more heat exchangers, arranged in series or parallel to each other.

5. The system 104 as claimed in Claim 1, wherein the H2S and VOC removal system 212 comprises of one or more filter units, arranged in series or parallel to each other.

6. The system 104 as claimed in Claim 1, wherein an oil filter is coupled to the fourth vessel and configured to filter out oil from the biogas.

7. A process 400 for obtaining dry biogas, comprising the steps of
receiving, at a first vessel 204, raw biogas via an inlet 202, wherein the biogas is received from a biogas digester 102;
condensing, at the first vessel 204, the raw biogas to separate moisture from the raw biogas to obtain the partially dried biogas, wherein the separated water is drained from the first vessel 204 via valve 204a;
pressurizing, inside a blower system 206, the partially dried biogas received from the first vessel 204 to obtain a biogas having a predetermined pressure;
treating, at a first temperature exchanger system 208, the biogas received from the blower system 206, wherein on treatment the biogas is cooled to a predetermined temperature;
condensing, at a second vessel 210, the cooled biogas to separate moisture from the biogas, wherein the separated water is drained from the second vessel 210 via a valve 210a;
filtering, at an H2S and VOC removal system 212, the condensed biogas received from the second vessel 210 to obtain a filtered biogas;
condensing, at a third vessel 214, the filtered biogas received from the H2S and VOC removal system 212 to separate moisture from the filtered biogas, wherein the separated water is drained from the third vessel 214 via a valve 214a;
compressing, at a compressor 216, the filtered and condensed biogas to a predetermined pressure;
treating, at a second temperature exchanger system 218, the compressed
biogas received from the compressor 216, by lowering the temperature of the compressed biogas to a predetermined temperature;
condensing, at a fourth vessel 220, the cooled biogas, received from the second temperature exchanger system 218, to separate moisture from the biogas, wherein the separated water is drained from the fourth vessel 220 via a valve 220a; and
re-heating, at the second temperature exchanger system 218, the biogas received from the fourth vessel 220, to a predetermined temperature to obtain dry biogas.

8. The process as claimed in Claim 7, wherein the biogas in the blower system is pressurized to 500 – 1000 mbarg.

9. The process as claimed in Claim 7, wherein the partially dried biogas is cooled to a temperature range of 12-22? in the first temperature exchanger system 208.

10. The process as claimed in Claim 9, wherein the temperature of the biogas is lowered to a first predetermined temperature in a heat exchanger 208a and thereafter to a second predetermined temperature in heat exchanger 208b of the first temperature exchanger system 208.

11. The process as claimed in Claim 10, wherein the first predetermined temperature is in the range of 35-50? and the second predetermined temperature is in the range of 12-22?.

12. The process as claimed in Claim 7, wherein the biogas received from the second vessel 210 is reheated to a temperature range of 19-29? and then introduced into the H2S and VOC removal system 212.

13. The process as claimed in Claim 7, wherein the biogas in the compressor 216 is compressed to 10-15barg.

14. The process as claimed in Claim 7, wherein the biogas is cooled to a temperature range of 5-12? in the second temperature exchanger system 218.

15. The process as claimed in Claim 14, wherein the temperature of the biogas is first lowered to a first predetermined temperature in a heat exchanger 218a, to a second predetermined temperature in heat exchanger 218b and thereafter to a third predetermined temperature in heat exchanger 218c of the second temperature exchanger system 218.

16. The process as claimed in Claim 15, wherein the first predetermined temperature is in the range of 40-50?, the second predetermined temperature is in the range of 25-35?, and the third predetermined temperature is in the range of 5-12?.

17. The process as claimed in Claim 7, wherein the biogas released from the fourth vessel 220 is re-heated to a temperature in the range of 22-32? in the second temperature exchanger system 218.

18. The process as claimed in Claim 7, wherein the dry biogas received from the fourth vessel 220 is filtered through an oil filter at a temperature range of 5-12?.