Indirect contact heat recovery with solidification in thermochemical hydrogen production

An analysis is presented for the heat transfer from molten salt in the copper–chlorine thermochemical cycle for hydrogen production. For this cycle to become economical relative to other existing or developing technologies, effective heat recovery is very important. Heat recovery processes are investigated from molten CuCl (a product of the copper oxychloride decomposition process in the Cu–Cl cycle). Recovering heat from molten CuCl at 500 °C is challenging due to its phase change from liquid to solid. Based on a previous examination of different options for this heat recovery (including atomization with steam generation, casting/extrusion, drum flaker and a rotary spinning atomizer), the casting/extrusion method was deemed advantageous. Hence that process is considered here, with a counter-current air flow as a coolant. Predicted results for axial growth of the solid layer and variations of the coolant and wall temperatures are presented and discussed. The effects of the inner tube diameter and air mass flow rate are also investigated.