Thermal analysis of supercritical water gasification of coal for power generation with partial heat recovery

Abstract

The methods of utilizing coal for power generation include direct combustion in air integrated with a steam cycle and gasification with O2/air integrated with a combined cycle. Special equipment is needed for the removal of NOx, SOx, CO2, and PM2.5, and the cost is high. The technology needed to perform supercritical water gasification (SCWG) can efficiently convert coal to a clean gaseous product. A novel model integrating SCWG with power cycles and heat recovery for power generation is proposed. The gasification product has a large amount of sensible and latent heat. The heat in the high temperature range is used to produce high-temperature and -pressure steam for power generation, whereas the heat in the low temperature range is recovered to preheat water before being heated to the supercritical state. The temperature that separates the high temperature range and low temperature range is the characteristicparameter T. The influences of T, which represents the extent of heat recovery, and the coal–water slurry concentration (CWSC) on the model performance are studied. The efficiency curves have a maximum value when T equals approximately 250°C in all CWSCs. The model efficiency increases with increasing CWSC at a certain T. The model efficiency can reach 42.18% when CWSC=11.3% and T=250°C.