Gas separation system and method for producing methane-enriched gas
A gas separation system for producing a CH 4 -enriched gas from a feedstock gas containing CO 2 and CH 4 , including a first gas separation membrane unit and a second gas separation membrane unit, in which the gas separation system includes a feedstock gas supply line connected to a gas inlet of the first gas separation membrane unit; a compression part disposed in the feedstock gas supply line; a first line connecting the retentate gas outlet of the first gas separation membrane unit and the gas inlet of the second gas separation membrane unit; a second line connecting the permeate gas outlet of the second gas separation membrane unit and the feedstock gas supply line; and a cooling part for lowering the operating temperature of the second gas separation membrane unit below the operating temperature of the first gas separation membrane unit.
1 . A gas separation system for producing a CH 4 -enriched gas from a feedstock gas comprising CO 2 and CH 4 ,
the gas separation system comprising a first gas separation membrane unit and a second gas separation membrane unit, wherein
each of the first gas separation membrane unit and the second gas separation membrane unit includes at least a gas inlet, a permeate gas outlet and a retentate gas outlet,
the gas separation system comprises:
a feedstock gas supply line connected to the gas inlet of the first gas separation membrane unit;
a compression part disposed in the feedstock gas supply line;
a first line connecting the retentate gas outlet of the first gas separation membrane unit and the gas inlet of the second gas separation membrane unit;
a second line connecting the permeate gas outlet of the second gas separation membrane unit and the feedstock gas supply line, and
a cooling part for lowering an operating temperature of the second gas separation membrane unit, T 2 , below an operating temperature of the first gas separation membrane unit, T 1 ,
and wherein a gas permeation rate of the second gas separation membrane unit at 40° C., P2′CO2(40), is higher than a gas permeation rate of the first gas separation membrane unit at 40° C., P1′CO2(40).
2 . The gas separation system according to claim 1 , wherein a temperature of a gas supplied to the second gas separation membrane unit is 30° C. or less.
3 . The gas separation system according to claim 1 , wherein a temperature of the gas supplied to the second gas separation membrane unit is lower than a temperature of a gas supplied to the first gas separation membrane unit.
4 . The gas separation system according to claim 1 , wherein a difference between the operating temperatures T 1 and T 2 , T 1 -T 2 , is 10° C. or more.
5 . The gas separation system according to claim 1 , wherein during operation of the gas separation system, a gas separation membrane included in the second gas separation membrane unit has a separation selectivity P 2 ′CO 2 /P 2 ′CH 4 of 15 or more and 3000 or less, and a CO 2 permeation rate P 2 ′CO 2 of 3×10 −5 cm 3 (STP)/cm 2 ·sec·cmHg or more and 80×10 −5 cm 3 (STP)/cm 2 ·sec·cmHg or less.
6 . The gas separation system according to claim 1 , wherein the cooling part is disposed in the first line.
7 . The gas separation system according to claim 1 , wherein a proportion of an amount of a gas flow refluxed to the first gas separation membrane unit in an amount of a gas flow supplied to the first gas separation membrane unit is 10 to 60%.
8 . The gas separation system according to claim 1 , further comprising a third gas separation membrane unit, wherein
the third gas separation membrane unit comprises at least a gas inlet, a permeate gas outlet and a retentate gas outlet, and
the gas separation system comprises:
a third line connecting the permeate gas outlet of the first gas separation membrane unit and the gas inlet of the third gas separation membrane unit, and
a fourth line connecting the retentate gas outlet of the third gas separation membrane unit and the feedstock gas supply line.
9 . The gas separation system according to claim 1 , comprising a liquefaction device for further cooling and liquefying a retentate gas of the second gas separation membrane unit.
10 . A gas separation system for producing a CH 4 -enriched gas from a feedstock gas comprising CO 2 and CH 4 ,
the gas separation system comprising a first gas separation membrane unit and a second gas separation membrane unit, wherein
each of the first gas separation membrane unit and the second gas separation membrane unit includes at least a gas inlet, a permeate gas outlet and a retentate gas outlet,
the gas separation system comprises:
a feedstock gas supply line connected to the gas inlet of the first gas separation membrane unit;
a compression part disposed in the feedstock gas supply line;
a first line connecting the retentate gas outlet of the first gas separation membrane unit and the gas inlet of the second gas separation membrane unit;
a second line connecting the permeate gas outlet of the second gas separation membrane unit and the feedstock gas supply line, and
a cooling part for lowering an operating temperature of the second gas separation membrane unit, T 2 , below an operating temperature of the first gas separation membrane unit, T 1 , and
wherein a carbon dioxide gas permeation rate of the second gas separation membrane unit at the operating temperature T 2 , P1′CO2(T2), is higher than a carbon dioxide gas permeation rate of the first gas separation membrane unit at the operating temperature T 1 , P1′CO2(T 1 ).
11 . A gas separation system for producing a CH 4 -enriched gas from a feedstock gas comprising CO 2 and CH 4 ,
the gas separation system comprising a first gas separation membrane unit and a second gas separation membrane unit, wherein
each of the first gas separation membrane unit and the second gas separation membrane unit includes at least a gas inlet, a permeate gas outlet and a retentate gas outlet,
the gas separation system comprises:
a feedstock gas supply line connected to the gas inlet of the first gas separation membrane unit;
a compression part disposed in the feedstock gas supply line;
a first line connecting the retentate gas outlet of the first gas separation membrane unit and the gas inlet of the second gas separation membrane unit;
a second line connecting the permeate gas outlet of the second gas separation membrane unit and the feedstock gas supply line, and
a cooling part for lowering an operating temperature of the second gas separation membrane unit, T 2 , below an operating temperature of the first gas separation membrane unit, T 1 , and
the gas separation system comprises a heating part for heating the feedstock gas supplied to the first gas separation membrane unit, the heating part being provided in the feedstock gas supply line.
12 . A gas separation system for producing a CH 4 -enriched gas from a feedstock gas comprising CO 2 and CH 4 ,
the gas separation system comprises a first gas separation membrane unit, a second gas separation membrane unit, and a third gas separation membrane unit, wherein
each of the first gas separation membrane unit and the second gas separation membrane unit includes at least a gas inlet, a permeate gas outlet and a retentate gas outlet,
the gas separation system comprises:
a feedstock gas supply line connected to the gas inlet of the first gas separation membrane unit;
a compression part disposed in the feedstock gas supply line;
a first line connecting the retentate gas outlet of the first gas separation membrane unit and the gas inlet of the second gas separation membrane unit;
a second line connecting the permeate gas outlet of the second gas separation membrane unit and the feedstock gas supply line, and
a cooling part for lowering an operating temperature of the second gas separation membrane unit, T 2 , below an operating temperature of the first gas separation membrane unit, T 1 ,
the third gas separation membrane unit comprises at least a gas inlet, a permeate gas outlet and a retentate gas outlet,
the gas separation system comprises:
a third line connecting the permeate gas outlet of the first gas separation membrane unit and the gas inlet of the third gas separation membrane unit, and
a fourth line connecting the retentate gas outlet of the third gas separation membrane unit and the feedstock gas supply line,
wherein the operating temperature of the second gas separation membrane unit is lower than an operating temperature of the third gas separation membrane unit.
13 . A gas separation system for producing a CH 4 -enriched gas from a feedstock gas comprising CO 2 and CH 4 ,
the gas separation system comprising a first gas separation membrane unit and a second gas separation membrane unit, wherein
each of the first gas separation membrane unit and the second gas separation membrane unit includes at least a gas inlet, a permeate gas outlet and a retentate gas outlet,
the gas separation system comprises:
a feedstock gas supply line connected to the gas inlet of the first gas separation membrane unit;
a compression part disposed in the feedstock gas supply line;
a first line connecting the retentate gas outlet of the first gas separation membrane unit and the gas inlet of the second gas separation membrane unit;
a second line connecting the permeate gas outlet of the second gas separation membrane unit and the feedstock gas supply line, and
a cooling part for lowering an operating temperature of the second gas separation membrane unit, T 2 , below an operating temperature of the first gas separation membrane unit, T 1 ,
wherein a cooled retentate gas of the second gas separation membrane unit is used to lower the operating temperature of the second gas separation membrane unit.
14 . A method for producing a CH 4 -enriched gas, comprising supplying a feedstock gas comprising at least CO 2 and CH 4 to a gas separation system, wherein
the gas separation system comprises at least a first gas separation membrane unit and a second gas separation membrane unit, each of the first gas separation membrane unit and the second gas separation membrane unit includes at least a gas inlet, a permeate gas outlet, and a retentate gas outlet,
the gas separation system comprises:
a feedstock gas supply line connected to the gas inlet of the first gas separation membrane unit;
a compression part disposed in the feedstock gas supply line;
a first line connecting the retentate gas outlet of the first gas separation membrane unit and the gas inlet of the second gas separation membrane unit;
a second line connecting the permeate gas outlet of the second gas separation membrane unit and the feedstock gas supply line, and
a cooling part for lowering an operating temperature of the second gas separation membrane unit below an operating temperature of the first gas separation membrane unit,
wherein a gas permeation rate of the second gas separation membrane unit at 40° C., P 2 ′CO 2 (40) , is higher than a gas permeation rate of the first gas separation membrane unit at 40° C., P 1 ′CO 2 (40) .