Micro-scale Thermodynamic and Kinetic Analysis of a Calcium Chloride Methanol System for Process Cooling

Calcium chloride methanol addition compounds are promising sorbent candidates, which can not only be used for thermal energy storage but also for providing evaporative cooling in industrial applications using low-grade heat. The methanolate dissociation occurs within the working temperature range of low temperature cooling systems. Methanol has a low freezing point and high operating pressure and is less toxic and corrosive than ammonia as refrigerant. In solid-gas reactions the overall specific cooling capacity mainly depends on the sorption rate of the reaction. In general the reaction pattern follows a complex mechanism, in which the formation of intermediate phases and structural changes might occur. In this study a comprehensive micro-scale analysis on the effect of the methanol partial pressure, the thermal history of the calcium chloride, the dissociation temperature and subsequent sorption-desorption cycling on the sorption rate has been carried out. Results show that thermodynamic conditions as well as the thermal history and physicochemical properties of the material have a great influence on the sorption rate, whereas only a marginal dependence between the regeneration temperature and the sorption process was observed.