Thermal analysis of coal gasification in supercritical water for power generation

The ways of utilizing coal for power generation are directly combusting in air integrating with a steam cycle and gasification with O₂/air integrating with a combined cycle. Special equipment is needed for the removal of NO_x, SO_x, CO₂, PM2.5 and the cost is high. The technology of supercritical water gasification (SCWG) can efficiently convert coal to clean gaseous product. A novel method integrating SCWG with combined cycle for power generation is proposed. Two models, which mainly differ in heat recovery unit, are proposed, theoretically analyzed, and compared. The influence of coal-water-slurry concentration (CWSC) on the efficiencies of the models and their difference is investigated. The efficiencies of the models are increased with increasing CWSC. Implementing chemical heat recovery can raise the model efficiency by about 5.1% when the CWSC is 11.3%. The model with chemical heat recovery has an advantage over the model without chemical heat recovery in high CWSC but such an advantage is absent at low CWSC (the critical data is about 3.8%).