Biogas reduction process and biogas reduction system
The biogas relaxation process addresses liquefaction and hydrate formation risks through staged pressure reduction and preheating, ensuring efficient biogas transfer and biomethane production without complex site-specific equipment.
Patent Information
- Application Number
- FR2023003888
- Authority / Receiving Office
- FR · FR
- Patent Type
- Utility models
- Current Assignee / Owner
- Filing Date
- 2023-04-19
- Publication Date
- 2025-05-02
- Estimated Expiration
- 2033-04-19
AI Technical Summary
Existing biogas relaxation processes face challenges such as the risk of gas liquefaction and hydrate formation during transportation and injection into natural gas networks, especially when methanization units are not connected to the network, requiring complex and expensive equipment installations and posing risks during compression and relaxation.
A biogas relaxation process involving preheating and staged pressure reduction from high upstream pressures to low downstream pressures, using a system with heaters and regulators to manage temperature and pressure transitions, ensuring biogas is transferred efficiently from mobile tanks to processing units.
The process prevents liquefaction and hydrate formation, enabling efficient biogas transfer and purification to biomethane, simplifying infrastructure needs and reducing costs by allowing a single common processing unit for multiple sites.
Smart Images
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Abstract
Description
Title of the invention: Method for expanding biogas and system for expanding biogas
[0001] The present invention relates to a method for expanding a biogas implemented during the transfer of the biogas from a mobile tank to a biogas treatment unit.
[0002] In order to recover biomass, such as agricultural effluents, it is known to methanize them to produce biogas using a methanizer.
[0003] The biogas thus produced is a renewable gas which can be purified in particular to produce biomethane in order to inject it into the natural gas distribution network. It is thus possible to have a more environmentally friendly energy source.
[0004] For this purpose, it is known to install methanizers and treatment units to purify biogas into biomethane directly on the biomass production site, such as an agricultural exploitation site for example.
[0005] However, this solution is not entirely satisfactory.
[0006] Indeed, it requires the installation of complex and expensive equipment on each biomass production site.
[0007] In addition, methanization units do not always have the possibility of being connected to the natural gas distribution network. In this case, the biogas must therefore be compressed to allow its road transport. Once delivered to a site with a purification unit and connected to the network, the biogas must therefore be expanded in order to be purified, then injected into a natural gas network.
[0008] However, the expansion of biogas presents the risk of liquefaction of the gas and creation of cold, which leads to the formation of hydrate crystals and prevents the proper conduct of this expansion.
[0009] An aim of the invention is to overcome these drawbacks and to provide a biogas expansion process capable of being implemented during a biogas collection process between, on the one hand, one or more methanization sites not connected to the network and, on the other hand, a site capable of purifying it and injecting it into a transport or distribution network.
[0010] To this end, the invention relates to a method for expanding a biogas implemented during the transfer of the biogas from a mobile tank to a biogas treatment unit, the method comprising the following steps:
[0011] a) a step of passing the biogas through an expansion pipe connecting the mobile tank to the treatment unit,
[0012] b) a step of preheating the biogas in the pipe,
[0013] c) a step of expanding the biogas in the pipe from an upstream pressure to a downstream pressure, the expansion taking place downstream of the biogas preheating stage.
[0014] The method according to the invention may comprise one or more of the following characteristics, taken in isolation or in any technically possible combination:
[0015] - the biogas comprises a carbon dioxide content greater than 20%;
[0016] - the upstream pressure is greater than 200 bar, and preferably between 200 bar and 350 bar, the downstream pressure being less than 5 bar;
[0017] - the expansion step comprises a first expansion of the biogas from the upstream pressure to an intermediate pressure, followed by a second expansion of the biogas from the intermediate pressure to the downstream pressure;
[0018] - the intermediate pressure is between 10 bar and 50 bar;
[0019] - the temperature of the biogas is regulated during the expansion stage.
[0020] The invention also relates to a method for collecting biogas for injection into a gas distribution or transport network, the method comprising the following successive steps:
[0021] a) compression of the biogas at the outlet of a methanizer and transfer of the compressed biogas into a mobile tank, the methanizer being located in a first location,
[0022] b) transporting the biogas in the mobile tank from the first location to a second location,
[0023] c) transferring the biogas from the mobile tank to a biogas treatment unit located in the second location, the expansion method as described above being implemented,
[0024] d) purification of the biogas into biomethane by the treatment unit, and
[0025] e) injection of biomethane into the gas distribution or transport network.
[0026] The invention also relates to a system for expanding a biogas comprising:
[0027] - an expansion pipe intended to connect a mobile biogas tank to a biogas treatment unit,
[0028] - a heater arranged around and / or in the expansion pipe to preheat the biogas, and
[0029] - an expansion device arranged in the expansion pipe for expanding the biogas from one pressure to a downstream pressure,
[0030] the heater comprising a first heating element upstream of the expansion device.
[0031] The system according to the invention may comprise one or more of the following characteristics, taken in isolation or in any technically possible combination:
[0032] - the expansion device comprises a first expander capable of expanding the biogas from the upstream pressure to an intermediate pressure, and a second regulator downstream of the first pressure reducer and capable of reducing the biogas from intermediate pressure to downstream pressure;
[0033] - the heater comprises a second heating element surrounding the device of expansion device and a second regulating device regulating the temperature of the second heating element so as to regulate the temperature of the biogas in the expansion device.
[0034] The invention will be better understood on reading the following description, given solely by way of example, and made with reference to the appended drawings, in which:
[0035] - [Fig.l] [Fig.l] is a schematic representation of an expansion system of a biogas according to the invention; and
[0036] - [Fig.2] [Fig.2] is a schematic representation of a method for collecting biogas according to the invention.
[0037] [Fig.l] illustrates a biogas expansion system 10 comprising an expansion pipe 12 intended to connect a mobile biogas tank 14 to a biogas treatment unit 16.
[0038] The expansion system 10 also comprises a heater 18 and an expansion device 20, in particular arranged on the expansion pipe 12 between the mobile biogas tank 14 and the biogas treatment unit 16.
[0039] Biogas means gas produced by the fermentation of organic matter.
[0040] In particular, biogas is produced by the anaerobic digestion of organic waste such as agricultural effluents, in particular manure or slurry.
[0041] The biogas preferably consists of a mixture of methane, carbon dioxide, and preferably other elements such as water vapor, hydrogen sulfide and possibly other contaminants.
[0042] In particular, the biogas comprises a methane content greater than 50%, preferably between 50% and 70% and advantageously between 55% and 65%.
[0043] The biogas comprises, for example, a carbon dioxide content greater than 20%, preferably between 20% and 50% and advantageously between 35% and 45%.
[0044] The expansion pipe 12 is for example a pipeline configured to transport biogas between the mobile biogas tank 14 and the biogas treatment unit 16.
[0045] In the remainder of the description, the terms “upstream” and “downstream” are defined according to the direction of normal circulation of the gas in the expansion pipe 12.
[0046] The mobile biogas tank 14 is for example a bottle configured to contain compressed biogas.
[0047] In particular, the biogas contained in the mobile tank 14 is at an upstream pressure
[0048] The upstream pressure Pam is greater than 200 bar, and preferably between 200 bar and 350 bar, in particular between 260 bar and 320 bar.
[0049] The pressure unit "bar" means the relative bar, that is to say the pressure difference compared to atmospheric pressure.
[0050] Preferably, the expansion line 12 also comprises an inlet valve 22.
[0051] The inlet valve 22 is for example a manual valve.
[0052] More particularly, the inlet valve 22 is movable between an open position, in which the connection between the mobile biogas tank 14 and the expansion pipe 12 is permitted, and a closed position, in which the connection between the mobile biogas tank 14 and the expansion pipe 12 is cut.
[0053] The treatment unit 16 is for example a biogas purification unit intended to eliminate carbon dioxide and hydrogen sulfide, to produce biomethane.
[0054] The biogas is for example injected into the treatment unit 16 at a downstream pressure P av lower than the upstream pressure Pam.
[0055] The downstream pressure Pav is for example less than 5 bar, and preferably between - 0.5 bar and 5 bar.
[0056] Preferably, the expansion pipe 12 also comprises an outlet valve 24.
[0057] The outlet valve 24 is for example a manual valve.
[0058] More particularly, the outlet valve 24 is movable between an open position, in which the connection between the expansion line 12 and the treatment unit 16 is permitted, and a closed position, in which the connection between the expansion line 12 and the treatment unit 16 is cut.
[0059] Optionally, the expansion pipe 12 also comprises a first pressure and temperature sensor 26 arranged upstream of the expansion device 20 and a second pressure and temperature sensor 28 arranged downstream of the expansion device 20.
[0060] Advantageously, the expansion pipe 12 also comprises a safety valve 30 at the outlet of the expansion device 20.
[0061] The heater 18 is arranged around and / or in the expansion pipe 12 to preheat the biogas.
[0062] In particular, the heater 18 comprises a first heating element 32 upstream of the expansion device 20, in particular capable of preheating the biogas upstream of the expansion device 20.
[0063] The first heating element 32 is for example a heating resistor arranged in the expansion pipe 12.
[0064] Advantageously, the heater 18 comprises a first regulation device 34 defining a set temperature of the first heating element 32.
[0065] The first regulating device 34 is advantageously activated when the inlet valve 22 moves to the open position.
[0066] Furthermore, the first regulation device 34 is preferably controlled by the temperature measured by the first pressure and temperature sensor 26.
[0067] The set temperature of the first heating element 32 is for example greater than 80°C, and preferably between 100°C and 120°C.
[0068] Preferably, the heater 18 comprises a second heating element 36 surrounding the expansion device 20, so as to regulate the temperature of the biogas in the expansion device 20.
[0069] The second heating element 36 is for example an aluminum heating body.
[0070] Advantageously, the heater 18 comprises a second regulation device 38 defining a set temperature of the second heating element 36, in particular so as to regulate the temperature of the biogas in the expansion device 20.
[0071] The second regulation device 38 is preferably controlled by the temperature measured by the second pressure and temperature sensor 28.
[0072] The set temperature of the second heating element 36 is for example greater than 80°C, and preferably between 100°C and 120°C.
[0073] The expansion device 20 is arranged in the expansion pipe 12 to expand the biogas from the upstream pressure Pam to the downstream pressure Pav.
[0074] As illustrated in [Fig.l], the expansion device 20 comprises a first expander 40 capable of expanding the biogas from the upstream pressure Pam to an intermediate pressure Pint, and a second expander 42 arranged downstream of the first expander 40 and capable of expanding the biogas from the intermediate pressure Pint to the downstream pressure Pav
[0075] The intermediate pressure Pint is preferably between 10 bar and 50 bar, and advantageously substantially equal to 12 bar.
[0076] The expansion device 20 preferably comprises a pressure gauge 44 measuring the intermediate pressure Pint between the outlet of the first expansion valve 40 and the inlet of the second expansion valve 42.
[0077] Furthermore, the expansion device 20 also advantageously comprises a safety valve 46 at the outlet of the first expansion valve 40 and upstream of the second expansion valve 42.
[0078] Advantageously, the expansion device 20 also comprises an inlet filter 48 capable of filtering the biogas, and in particular of filtering any solid particles possibly present therein.
[0079] The intake filter 48 is preferably arranged upstream of the first regulator 40.
[0080] Preferably, the expansion device 20 also comprises a purge valve. 50 capable of purging the expansion line 12 in the expansion device 20 upstream of the first expansion valve 40.
[0081] A biogas expansion method implemented during the transfer of biogas from the mobile tank 14 to the biogas treatment unit 16 will now be described.
[0082] Preferably, the biogas expansion process is implemented by the expansion system 10 as described above.
[0083] The expansion method comprises a step of continuous passage of the biogas in the expansion pipe 12 connecting the mobile tank 14 to the treatment unit 16.
[0084] In particular, to implement this step, the inlet valve 22 of the expansion pipe 12 is in the open position.
[0085] The expansion process comprises, simultaneously with the passage of the biogas, a step of preheating the biogas in the pipe 12.
[0086] In particular, during this preheating step, the biogas is heated by the first heating element 32.
[0087] For this purpose, the first regulating device 34 of the heater 18 defines for example a set temperature of the first heating element 32. The set temperature of the first heating element 32 is for example greater than 80°C, and preferably between 100°C and 120°C.
[0088] Advantageously, the upstream pressure and the temperature of the biogas are measured by the first pressure and temperature sensor 26 downstream of the preheating step.
[0089] The expansion method also comprises a step of expanding the biogas in the pipe 12 from the upstream pressure Pam to the downstream pressure Pav.
[0090] More precisely, the expansion step is carried out downstream of the biogas preheating step.
[0091] Preferably, the expansion step comprises a first expansion of the biogas from the upstream pressure Pam to the intermediate pressure Pint, followed by a second expansion of the biogas from the intermediate pressure Pint to the downstream pressure Pav.
[0092] Preferably, the first expansion is implemented by the first expansion valve 40 and the second expansion is implemented by the second expansion valve 42.
[0093] Preferably, the biogas is filtered by the inlet filter 48 upstream of the first regulator 40.
[0094] Furthermore, the intermediate pressure Pint between the two expansions is measured by the pressure gauge 44.
[0095] Advantageously, the temperature of the biogas is regulated during the expansion step, in particular by the second heating element 36 of the heater 18 regulated by the second regulation device 38.
[0096] The expansion flow rate advantageously remains constant during the expansion step.
[0097] Following the expansion step, the biogas at downstream pressure Pavest injected into the treatment unit 16.
[0098] In particular, during this step, the outlet valve 24 of the expansion pipe 12 is in the open position.
[0099] With reference to [Fig.2], a method of collecting biogas for injection into a gas distribution or transport network 100 will now be described.
[0100] The biogas is preferably initially produced in at least one methanizer 102, in particular by the anaerobic digestion of organic waste such as, for example, agricultural effluents, in particular manure or slurry.
[0101] The methanizer 102 is located in a first specific location. The first location is for example the agricultural exploitation site producing the organic waste.
[0102] The method initially comprises a step of compressing the biogas at the outlet of the methanizer 102 and transferring the compressed biogas into the mobile tank 14.
[0103] In particular, a compressor 104 is preferably installed in the first location near the methanizer 102.
[0104] Preferably, as illustrated in [Fig.2], compressed biogas from a plurality of methanizers 102 is transferred into a plurality of mobile tanks 14 which are for example collected by the same road transport vehicle.
[0105] In other words, the method comprises collecting compressed biogas from a plurality of agricultural sites.
[0106] The method then comprises a step of transporting the biogas in the mobile tank 14 from the first location or first specific locations, in particular from each methanizer 102, to a second location, in particular an expansion and purification point.
[0107] For example, as illustrated in [Fig.2], the mobile tank 14 is transported by road to the pressure reduction and purification point.
[0108] The method subsequently comprises a step of transferring the biogas from the mobile tank 14 to the biogas treatment unit 16 located in the second location.
[0109] During this transfer step, the biogas expansion process as described above is implemented.
[0110] The method then comprises a step of purifying the biogas into biomethane by the treatment unit 16.
[0111] During this biomethane purification step, the biogas is preferably treated with to eliminate carbon dioxide to produce biomethane.
[0112] The method subsequently comprises a step of injecting the biomethane into the gas transport or distribution network 100.
[0113] The biogas collection method according to the invention allows injection of biomethane at a single point. This method requires a single treatment unit 16 common to several biogas production sites.
[0114] Such a process thus simplifies the production of biomethane and avoids costly investments.
[0115] Such a method is made possible by the expansion system 10 and the expansion method according to the invention.
[0116] In particular, the step of preheating the biogas upstream of the expansion step, using the heater 18, makes it possible to avoid the liquefaction or even the solidification of the biogas and therefore the creation of methane hydrate crystals.
[0117] Furthermore, the regulation of the temperature during the expansion stage and the division of the expansion stage into two successive expansions greatly facilitate the control of the expansion of the biogas.
Claims
Claims
1. A method of expanding a biogas implemented during the transfer of the biogas from a mobile tank (14) to a biogas treatment unit (16), the method comprising the following steps: a. a step of passing the biogas through an expansion pipe (12) connecting the mobile tank (14) to the treatment unit (16), b. a step of preheating the biogas in the pipe (12), c. a step of expanding the biogas in the pipe (12) from an upstream pressure (Pam) to a downstream pressure (Pav), the expansion taking place downstream of the step of preheating the biogas.
2. The method of claim 1, wherein the biogas comprises a carbon dioxide content greater than 20%.
3. Method according to claim 1 or 2, in which the upstream pressure (Pa m) is greater than 200 bar, and preferably between 200 bar and 350 bar, the downstream pressure (Pav) being less than 5 bar.
4. A method according to any preceding claim, wherein the expansion step comprises a first expansion of the biogas from the upstream pressure (Pam) to an intermediate pressure (Pint), followed by a second expansion of the biogas from the intermediate pressure (Pint) to the downstream pressure (Pav).
5. Method according to claim 4, in which the intermediate pressure (Pint) is between 10 bar and 50 bar.
6. A method according to any preceding claim, wherein the temperature of the biogas is regulated during the expansion step.
7. A method of collecting biogas for injection into a gas distribution or transport network (100), the method comprising the following successive steps: a. compressing the biogas at the outlet of a methanizer (102) and transferring the compressed biogas into a mobile tank (14), the methanizer (102) being located in a first location, b. transporting the biogas in the mobile tank (14) from the first location to a second location, c. transferring the biogas from the mobile tank (14) to a biogas treatment unit (16) located in the second location, placement, the expansion method according to any one of the preceding claims being implemented, d. purification of the biogas into biomethane by the treatment unit (16), and e. injection of the biomethane into the gas distribution or transport network (100).
8. A system (10) for expanding a biogas comprising: - an expansion pipe (12) intended to connect a mobile biogas tank (14) to a biogas treatment unit (16), - a heater (18) arranged around and / or in the expansion pipe (12) for preheating the biogas, and - an expansion device (20) arranged in the expansion pipe (12) for expanding the biogas from a pressure (Pam) to a downstream pressure (Pav), the heater (18) comprising a first heating element (32) upstream of the expansion device (20).
9. Expansion system (10) according to claim 8, wherein the expansion device (20) comprises a first expander (40) capable of expanding the biogas from the upstream pressure (Pam) to an intermediate pressure (Pint), and a second expander (42) downstream of the first expander (40) and capable of expanding the biogas from the intermediate pressure (Pint) to the downstream pressure (Pav).
10. An expansion system (10) according to claim 8 or 9, wherein the reheater (18) comprises a second heating element (36) surrounding the expansion device (20) and a second control device (38) controlling the temperature of the second heating element (36) so as to control the temperature of the biogas in the expansion device (20).