Revista de Engenharia Química e Tecnologia de Processos
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Metastability of CuCl₂ in H₂O-HCl for the Copper-Chlorine Thermochemical Cycle of Hydrogen Production

 Lescisin M, Rosen MA, Jianu OA and Pope K

In this paper, metastability of CuCl2 in H2O-HCL for applications to the Cu-Cl thermochemical cycle is experimentally investigated to decrease crystallizing (precipitating) temperature and reduce thermal energy requirements of the cycle. Metastability delays the phase transition by altering the phase transition temperature, depending on direction (heating or cooling). The dissolving temperature is increased if the solution is heated and decreased if the solution is cooled, whereas a typical simple solubility model assumes dissolving and crystallizing occur at the same temperature. The solution temperature is controlled using an ethylene-glycol heater/chiller and measured with a thermocouple. The results of this paper show the metastable zone width increases with cooling rate and is unaffected by HCL concentration. The solubility product constant is calculated for CuCl2 dissolving in various concentrations of HCL and decreases with increasing temperature and HCL concentration.