Method for reducing methane emissions from biogas upgrading
AssigneeAirco Process Technology A/S
InventorRasmus Find
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Abstract
The present invention relates to a method for upgrading biogas generated by a biological process wherein at least carbon dioxide is removed from the bio-gas. More specifically the present invention relates to method for upgrading a biogas comprising a first absorption step wherein the liquid effluent is subjected to a second absorption step and a flash step and the gas streams resulting therefrom are recycled. The present invention also relates a biogas upgrading plant.
Claims31
A method for upgrading a biogas stream comprising methane and carbon dioxide, the method comprising the steps of:
- a) feeding the biogas stream and a first liquid physical absorbing agent to a first absorber,
- b) absorbing carbon dioxide and methane from the biogas stream into the first physical absorbing agent thereby obtaining a first gas effluent having a lower content of carbon dioxide than the biogas stream and a first liquid effluent having higher content of carbon dioxide than the first absorbing agent,
- c) feeding the first liquid effluent to a second absorber and feeding a second liquid physical absorbing agent to the second absorber, whereby carbon dioxide released from the first liquid effluent is subsequently absorbed into the second physical absorbing agent, thereby obtaining a second gas effluent comprising methane and a second liquid effluent having a lower content of methane than the first liquid effluent,
- d) depressurizing and feeding the second liquid effluent into a flash unit,
- e) flashing the depressurized second liquid effluent thereby obtaining a flash gas effluent comprising methane and a flash liquid effluent having a lower content of methane than the second liquid effluent,
- f) feeding the flash gas effluent into the second absorber or into the biogas stream of step a),
- g) feeding the second gas effluent into the first absorber optionally through the biogas stream of step a), and
- h) recovering or further processing the first gas effluent as an upgraded biogas stream.
A method for upgrading a biogas stream comprising me-thane and carbon dioxide, the method comprising the steps of:
- a) feeding the biogas stream into a first absorber, the first absorber having a first section and a second section, wherein the first section is positioned above the second section, and the biogas stream is fed to the first absorber at a position between the first and second sections of the first absorber,
- b) feeding a first liquid physical absorbing agent to the first absorber at a position above the first section,
- c) absorbing carbon dioxide and methane from the biogas stream into the first physical absorbing agent thereby obtaining a first gas effluent having a lower content of carbon dioxide than the biogas stream and a first liquid effluent having higher content of carbon dioxide than the absorbing stream,
- d) depressurizing and feeding the first liquid effluent into a flash unit,
- e) flashing the depressurized first liquid effluent thereby obtaining a flash gas effluent comprising methane and a flash liquid effluent having a lower content of methane than the second liquid effluent,
- f) compressing and feeding the flash gas effluent into the first absorber at a position below the second section of the first absorber,
- g) recovering or further processing the first gas effluent as an upgraded biogas stream.
Dependencies are inferred from the claim text.