Process integration of material flows of copper chlorides in the thermochemical Cu–Cl cycle

The copper–chlorine (Cu–Cl) thermochemical hydrogen production cycle consists of three chemical reactions, i.e., electrolyisis of copper(I) chloride (CuCl) and hydrogen chloride (HCl), hydrolysis of copper(II) chloride (CuCl2), and thermolysis of copper oxychloride (Cu2OCl2). The outlet stream of the electrolysis includes aqueous CuCl2, CuCl, and HCl. The CuCl2 product of the electrolysis is the reactant of downstream hydrolysis. In this paper, three integration pathways for the copper chloride flows between electrolysis and hydrolysis reactors are investigated in terms of energy saving and reduction of auxiliary operations for the processing of the flows. The integration pathways include solid precipitation of CuCl2 using a crystallization process, water vaporization in the hydrolysis reactor by introducing the electrolyzer outlet stream directly to the reactor, and vaporization in an intermediate spray dryer.