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

Explanation

Water gas in produced when superheated steam is passed over red hot cake or coal at 1270 K in pressence of nickel as catalyst.
`underset("Coke")(C(s)) + underset("Steam")(H_(2)O(g)) + 121.3KJ underset("Nickel")overset(1270K) to underset("water gas") underset(ubrace(CO(g) + H_(2)(g))`
It is inconvinient to obtain pure `H_(2)` from water gas as CO is difficult to remove. Hence, 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 `FeCrO_(4)` catalyst at 673 K
`underset("water gas") (ubrace(CO(g) + H_(2)(g))) + underset("Steam")(H_(2)O(g)) underset(FeCrO_(4))overset(673K)to CO_(2)(g) + 2H_(2)(g)`
This is called water-gas shiff reaction. Carbon dioxide is removed by scrubbing with mixture of sodium arsenite solution or by passing the mixture through water under 30 atm pressing the miture throught water under 30 atm pressure when `CO_(2)` dissolves behing `H_(2)` which is collected.