Mixed gas separation method and mixed gas separation device
A mixed gas separation method includes supplying a mixed gas containing at least N 2 , H 2 , and CO 2 and having a CO 2 concentration of 30% or less by volume to a first separation membrane that selectively allows passage of H 2 , supplying the first non-permeated gas to a second separation membrane that selectively allows passage of CO 2 , and supplying the second non-permeated gas to a CO 2 collector that separates and collects CO 2 by a separation method other than membrane separation to collect CO 2 contained in the second non-permeated gas. The first non-permeated gas has a CO 2 concentration that is 5% or more by volume higher than or equal to the CO 2 concentration in the mixed gas. The second non-permeated gas has an N 2 concentration of 50% or more by volume and an H 2 concentration of 30% or less by volume.
1 . A mixed gas separation method comprising:
a) supplying a mixed gas containing at least N 2 , H 2 , and CO 2 and having a CO 2 concentration of 30% or less by volume to a first separation membrane that selectively allows passage of H 2 to separate said mixed gas into a first permeated gas that has permeated through said first separation membrane and a first non-permeated gas that has not permeated through said first separation membrane;
b) supplying said first non-permeated gas to a second separation membrane that selectively allows passage of CO 2 to separate said first non-permeated gas into a second permeated gas that has permeated through said second separation membrane and a second non-permeated gas that has not permeated through said second separation membrane; and
c) supplying said second non-permeated gas to a CO 2 collector that separates and collects CO 2 by a separation method other than membrane separation to collect CO 2 contained in said second non-permeated gas,
wherein said first non-permeated gas has a CO 2 concentration that is 5% or more by volume higher than or equal to the CO 2 concentration in said mixed gas,
said second non-permeated gas has an N 2 concentration of 50% or more by volume, and
said second non-permeated gas has an H 2 concentration of 30% or less by volume.
2 . The mixed gas separation method according to claim 1 , wherein
after said operation a), said first permeated gas is mixed with a gas exhausted from said CO 2 collector.
3 . The mixed gas separation method according to claim 1 , wherein
after said operation a), said first permeated gas is supplied to said CO 2 collector.
4 . The mixed gas separation method according to claim 1 , wherein
said second separation membrane has a CO 2 recovery rate of 70% or higher.
5 . The mixed gas separation method according to claim 1 , wherein
the separation method used in said CO 2 collector to separate CO 2 is chemical absorption.
6 . The mixed gas separation method according to claim 1 , wherein
said second non-permeated gas has an N 2 concentration of 60% or more by volume, and
said second non-permeated gas has a CO 2 concentration of 30% or less by volume.
7 . The mixed gas separation method according to claim 1 , wherein
said second permeated gas has a CO 2 concentration of 97% or more by volume.
8 . The mixed gas separation method according to claim 1 , wherein
said mixed gas supplied to said first separation membrane in said operation a) has a pressure of 1.5 MPaG or higher.
9 . The mixed gas separation method according to claim 1 , wherein
said first separation membrane has H 2 /CO 2 selectivity of 100 or higher, and
said second separation membrane has CO 2 /H 2 selectivity of 100 or higher.
10 . The mixed gas separation method according to claim 1 , wherein
at least one of said first separation membrane or said second separation membrane is a zeolite membrane.