Coal gasification with CO 2 in molten salt for solar thermal/chemical energy conversion

Abstract

Coal gasification with CO 2 in Na 2CO 3–K 2CO 3 molten salt that was used as thermal storage for gas/solid heterogeneous reaction was studied to apply this system for solar thermal/chemical energy conversion. The reactions were performed at 1173 K under various CO 2 flow rates, weights of the molten salt and Na 2CO 3/K 2CO 3 ratios. The CO 2 gas consumption rate increased with increasing CO 2 flow rate, however, the conversion efficiency of CO 2 to CO was decreased. As the weight of the molten salt increased, the rate of the gasification reaction was decreased. The maximum conversion efficiency of CO 2 to CO under the experimental conditions reached 71% at the CO 2 flow rate of 310 μmol/s. Thus 37 J of the solar thermal energy can be converted into chemical energy per second by the endothermic process of the Boudouard reaction (C+CO 2=2CO−169.16 kJ (at 1150 K); coal=10 g), when this gasification reaction would be performed by using concentrated solar heat.