Coal gasification with CO2 in molten salt for solar thermal/chemical energy conversion

Coal gasification with CO2 in Na2CO3–K2CO3 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 CO2 flow rates, weights of the molten salt and Na2CO3/K2CO3 ratios. The CO2 gas consumption rate increased with increasing CO2 flow rate, however, the conversion efficiency of CO2 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 CO2 to CO under the experimental conditions reached 71% at the CO2 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+CO2=2CO−169.16 kJ (at 1150 K); coal=10 g), when this gasification reaction would be performed by using concentrated solar heat.