This paper examines the chemical equilibrium and gaseous product fraction of a multiphase gas-solid flow involving hydrolysis of copper (II) chloride and steam in a packed bed reactor. The effectiveness of the water splitting process has a significant impact on the efficiency of the thermochemical copper-chlorine (Cu-Cl) cycle for hydrogen production. A thermodynamic analysis of the HCl fraction in the gaseous effluent is presented, along with a predictive model of solid particle conversion based on the reaction temperature and pressure. Experimental results are presented for a horizontal packed bed reactor which exposes a low steam flow rate to a large volume of solid CuCl2 in the packed bed reactor. The predicted and experimental results demonstrate that an HCl fraction above 0.3 can be achieved within the hydrolysis reactor, thus allowing effective integration between hydrolysis and downstream electrolytic hydrogen production steps in the Cu-Cl cycle, without costly HCl/steam separation processes. Copyright (c) 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.