| CPC F25J 1/0015 (2013.01) [F25J 1/0022 (2013.01); F25J 1/0072 (2013.01); F25J 1/0214 (2013.01); F25J 2210/42 (2013.01); F25J 2210/60 (2013.01); F25J 2290/12 (2013.01)] | 17 Claims |
|
1. A method for processing a gas mixture containing nitrogen and methane,
wherein the gas mixture is at least partly liquefied using a mixed refrigerant circuit, expanded, and introduced into a storage tank,
wherein a liquid phase, which is depleted in nitrogen and enriched with methane relative to the gas mixture, and a vapor phase, which is enriched with nitrogen and depleted in methane relative to the gas mixture, are formed in the storage tank,
wherein at least some of the vapor phase is withdrawn from the storage tank, compressed, at least partly liquefied using a mixed refrigerant circuit, and subjected to low-temperature rectification,
wherein a top fraction rich in nitrogen and lean in methane and a bottom liquid lean in nitrogen and rich in methane are formed in the low-temperature rectification, and the top fraction is withdrawn from the low-temperature rectification, and
wherein the liquefaction of the gas mixture containing nitrogen and methane and the at least partial liquefaction of the vapor phase are both performed using a single, mixed refrigerant circuit,
wherein
the liquefaction of the gas mixture containing nitrogen and methane is performed in a first heat exchanger and the at least partial liquefaction of the vapor phase is performed in a first second exchanger wherein said first heat exchanger and said second heat exchanger are separate heat exchangers,
a partial stream of the bottom liquid is withdrawn from the low-temperature rectification, at least partly vaporized by heat exchange with a top gas drawn off from the low-temperature rectification, and the top gas is at least partially condensed and supplied to the low-temperature rectification as a return stream,
wherein, in the mixed refrigerant circuit, the mixed refrigerant is split into a first refrigerant gas phase, a first refrigerant liquid phase, a second refrigerant gas phase, and a second refrigerant liquid phase,
wherein a first partial stream of the first refrigerant liquid phase is combined with a first partial stream of the second refrigerant gas phase and used as refrigerant in the first heat exchanger, and a second partial stream of the first refrigerant liquid phase is combined with a second partial stream of the second refrigerant gas phase and used as refrigerant in the second heat exchanger, and
the top fraction withdrawn from the low-temperature rectification has contains inert component(s) comprising nitrogen, and the concentration of all inert components, including nitrogen, in the withdrawn top fraction is at least 99 mol %.
|