Hydrogen production by the Cu–Cl thermochemical cycle: Investigation of the key step of hydrolysing CuCl 2 to Cu 2OCl 2 and HCl using a spray reactor

Abstract

One of the most challenging steps in the thermochemical Cu–Cl cycle for the production of hydrogen is the hydrolysis of CuCl 2 into Cu 2OCl 2 and HCl while avoiding the need for excess water and the undesired thermolysis reaction, which gives CuCl and Cl 2. Argonne National Laboratory has designed a spray reactor where an aqueous solution of CuCl 2 is atomized into a heated zone, into which steam/Ar are injected in co- or counter-current flow. The solid products of the reaction were analyzed by XRD and SEM. With a pneumatic nebulizer, the counter-current flow design gave high yields of Cu 2OCl 2 compared to the co-current flow design, but some CuCl 2 remained unreacted in both designs. With an ultrasonic nozzle, essentially 100% yields of Cu 2OCl 2 were obtained. Some CuCl was present in the products with both types of atomizers but this is believed to be due to decomposition of Cu 2OCl 2 rather than CuCl 2. Analyses of gaseous products from the hydrolysis reactions in a fixed bed were conducted at the Commissariat à L'Energie Atomique using ultraviolet-visible spectrometry and conductivity. At a reaction temperature of 390 °C, the desired HCl was formed while no Cl 2 was detected until the bed temperature was above 400 °C.