Membrane permeate recycle with pressurized anaerobic digesters
AssigneeL'Air Liquide, Societe Anonyme pour l'Etude et l'Exploitation des Procedes Georges Claude
InventorsMin Ho Maeng, Sudhir Kulkarni, Shu Fang
Life of this patent
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Abstract
A system for upgrading biogas through a membrane separation process comprises an anaerobic digester, operated under an operation pressure higher than atmosphere pressure, preferably greater than 4 baba, generating the biogas, a first membrane stage and a second membrane stage, separating the biogas into a residue stream, enriched in CH4, and a permeate stream, enriched in CO2, a compressor compressing the permeate stream to a pressure slightly greater than the operation pressure, and recycling the permeate stream back to the bottom volume of the anaerobic digester.
Claims15
A system for upgrading biogas through a membrane separation process comprising:
- an anaerobic digester, operated under an operation pressure higher than atmosphere pressure, configured to generate the biogas from a feedstock containing an organic content;
- a first membrane stage, configured to separate the biogas into a first residue stream, enriched in CH4, withdrawn from the residue side of the first membrane stage and forwarded to a second membrane stage as a feed gas therein, and a first permeate stream, enriched in CO2, withdrawn from the permeate side of the first membrane stage, and vented out;
- the second membrane stage, connected to the first membrane stage in series, configured to separate the residue stream from the first membrane into a second residue stream, enriched in CH4, withdrawn from the residue side of the second membrane stage and forwarded to a point of use, and a second permeate stream, enriched in CO2, withdrawn from the permeate side of the second membrane stage and sent to a compressor;
- and
- a third membrane stage, configured to separate the first permeate stream from the first membrane stage into a third residue stream containing CO2 and CH4, withdrawn from the residue side of the third membrane stage and sent to the compressor, and a third permeate stream, enriched in CO2, withdrawn from the permeate side of the third membrane stage, and vented out,
- wherein the residue stream from the third membrane stage in combination with the permeate stream from the second membrane stage is compressed and recycled back to the bottom volume of the digestate sludge phase in the anaerobic digester;
- wherein the compressor is configured to compress the second permeate stream from the second membrane stage and the third residue stream form the third membrane stage to a pressure greater than the operation pressure.
A membrane separation process for upgrading biogas from an anaerobic digester, the process comprising the steps of:
- feeding a feedstock having an organic content to the anaerobic digester;
- generating the biogas comprising CH4 and CO2 from the anaerobic digester under an operation pressure greater than atmosphere pressure;
- feeding the biogas to a first membrane stage, wherein the biogas is separated into a first residue stream enriched in CH4 and a first permeate stream enriched in CO2 compared to the biogas;
- feeding the first residue stream from the first membrane stage to a second membrane stage, wherein the first residue stream is separated into a second residue stream enriched in CH4 and a second permeate stream enriched in CO2 compared to the first residue stream;
- feeding the first permeate stream to a third membrane stage, wherein the first permeate stream is separated into a third residue stream containing CO2 and CH4 and a third permeate gas enriched in CO2;
- compressing a combination stream of the third residue stream from the third membrane stage and the second permeate stream from the second membrane stage;
- and
- recycling the compressed combination stream back to the bottom volume of digestate sludge phase in the anaerobic reactor.
Dependencies are inferred from the claim text.