Heat recovery with low temperature spray drying for thermochemical hydrogen production

Abstract

This paper examines the heat transfer and evaporative drying of molten salt droplets in a thermochemical copper-chlorine (Cu-Cl) cycle of hydrogen production. An aqeous CuCl2 stream exiting from an electrochemical cell is preheated to 150°C, before entering the flash dryer to produce solid CuCl2(s). The device must add sufficient heat to remove water and recover solid CuCl2. New innovations of heat recovery aim to develop alternatives to reduce costs and improve efficiency of the evaporation process for CuCl2 particle production. This includes a new method to pressurize the liquid stream sufficiently to atomize droplets through a pressure-reducing nozzle in the spray system, thereby enhancing the devices performance. The liquid phase flashes due to a sudden pressure drop. Unlike other thermochemical cycles, the Cu-Cl cycle can take unique advantage of low-grade waste heat for spray drying and vaporizing processes at low temperatures. The powder produced by spray drying is then injected in a fluidized reactor to eventually produce hydrogen. A common byproduct of manufacturing processes, incinerators, industrial furnaces, etc. - heat - can become a valuable resource through its utility for hydrogen production with the Cu-Cl cycle.