How can production of hydrogen from water gas be increased by using water gas shift reaction ?

Explanation

Water gas is produced when superheated steam is passed over red hot coke or coal at 1270 K in the presence of nickel as catalyst.
`C(s) + underset("stream")(H_2 O(g)) to underset("Water gas")ubrace (CO(g) + H_2 (g)) - 121.3 KJ`
Pure `H_2` from water gas cannot be obtained easily because it is difficult to remove CO. Therefore, to increase the production of `H_2` from water gas, Co is oxidised to `CO_2` by mixing it with more steam and passing the mixture over heated `Fe CrO_4` catalyst at 673 K.
`underset("Water gas")ubrace(H_2 + CO) + H_2 O underset(FeCrO_4)overset(673K)to CO_2 + 2H_2`
The `CO_2` produced is removed by scrubbing with sodium arsenite solution.