US 12,072,144 B2
Cryogenic purification of biogas with withdrawal at an intermediate stage and external solidification of carbon dioxide
Jorge Ernesto Tovar Ramos, Cachan (FR)
Assigned to L'Air Liquide, Societe Anonyme Pour l'Etude et l'Exploitation des Procedes Georges Claude, Paris (FR)
Filed by L'Air Liquide Société Anonyme pour l'Etude et l'Exploitation des Procédés Georges Claude, Paris (FR)
Filed on Jun. 9, 2022, as Appl. No. 17/836,139.
Claims priority of application No. 2106091 (FR), filed on Jun. 9, 2021.
Prior Publication US 2022/0397345 A1, Dec. 15, 2022
This patent is subject to a terminal disclaimer.
Int. Cl. F25J 3/02 (2006.01); B01D 3/14 (2006.01); F25J 3/06 (2006.01)
CPC F25J 3/0233 (2013.01) [B01D 3/143 (2013.01); F25J 3/0266 (2013.01); F25J 3/067 (2013.01); F25J 2200/70 (2013.01)] 2 Claims
OG exemplary drawing
 
1. A combined plant for cryogenic separation and liquefaction of methane and carbon dioxide in a biogas stream, comprising:
a mixing means for mixing a biogas stream with a recycle gas stream, thereby producing a mixed biogas stream,
a compressor for compressing the mixed biogas stream to a pressure suitable for distillation, thereby producing a compressed stream,
a first exchanger for cooling the compressed mixture, thereby producing a cooled stream,
a distillation column, comprising a top and a bottom, configured to be supplied with the cooled stream and configured to produce a methane stream at the top and a CO2-enriched liquid stream at the bottom,
a second exchanger for liquefying the methane stream, thereby producing a liquefied methane stream,
a separating means for separating the liquefied methane stream into two portions: a “reflux” portion and a “product” portion,
an expanding means for expanding the CO2-enriched liquid stream thereby producing an expanded CO2-enriched liquid stream, and a heating means for heating the expanded CO2-enriched liquid stream, thereby producing a heated CO2-enriched stream, and for recovering the cold from the expanded CO2-enriched liquid stream, and
a separator vessel for receiving the heated CO2-enriched stream and for producing an overhead vapour stream and a liquid CO2 stream,
a means for withdrawing a vapour stream from an intermediate stage of the distillation column,
a condensing means for partially condensing the vapour stream and producing a two-phase stream,
wherein
the mixing means is configured such that the recycle gas stream corresponds to the overhead vapour stream recovered at the outlet of the separator vessel, and
a cryogenic separation unit comprises:
the distillation column comprising a cold section at the top of the distillation column and a hot section at the bottom of the distillation column,
at least two containers external to the distillation column, configured to place in contact a liquid stream from the cold section and a vapour stream rising from the hot section and for trapping solid CO2, and
a device for regenerating the at least two external containers, comprising an extracting means for extracting a fluid from the distillation column which is configured to liquefy the solid CO2, a means for introducing this fluid into the at least two external containers in regeneration thereby melting the solid CO2 and a means for reintroducing the resulting liquid CO2-vapour mixture into the distillation column.