Patent ID: 8173005

Claim:
A process for obtaining hydrogen gas and oxygen gas from water decomposition comprising using a copper-chlorine (Cu—Cl) thermochemical cycle comprising the steps of: 1) reacting electrolytic Cu and dry HCl to obtain hydrogen gas and molten CuCl salt; 2) subjecting solid CuCl and HCl in an aqueous solution to electrolysis to obtain Cu and an aqueous slurry containing HCl and CuCl 2 ; 3) drying the aqueous slurry obtained from step (2) to obtain solid CuCl 2 and H 2 O/HCl vapour; 4) reacting the solid CuCl 2 with steam to obtain solid CuOCuCl 2 and gaseous HCl; 5) decomposing the solid CuOCuCl 2 obtained in step 4 at a temperature of about 500° C. to obtain molten CuCl and oxygen gas; and wherein at least one first chemical heat pump that upgrades low grade heat from an industrial source to a higher intermediate temperature, supplies heat to the endothermic step 4) of the hydrogen gas production cycle and at least one second chemical heat pump that is a solid-gas heat pump and utilises a high temperature salt to upgrade heat from the exothermic step 1) of the hydrogen gas production cycle, to a higher temperature needed by the endothermic oxygen step 5) of the hydrogen gas production cycle.