Thermodynamic and environmental analysis of integrated supercritical water gasification of coal for power and hydrogen production

Coal combustion for thermal power generation causes serious environmental problems. Relatively efficient and clean coal utilization technologies need to be developed to alleviate the growing energy crisis and environmental pollution pressure. A novel integrated supercritical water gasification of coal system with 40 t/h throughput of coal and water was designed. A thermodynamic analysis and a life cycle environmental assessment under different conditions were performed using Aspen Plus 8.4 and SimaPro 9.0 based on the Ecoinvent 3 database, respectively. Results show that the maximum energy loss is induced by the waste heat of the effluent from the heat exchanger. By using organic Rankine cycle, the energy efficiency of the system could reach 53.3% when the temperature and coal concentration are 700 degrees C and 15 wt%, respectively. The global warming potential, acidification potential and nitrogen oxides are 0.058 kg carbon dioxide eq/(kW.h), 3.63 x 10(-4) kg sulfur dioxide eq/ (kW.h) and 7.04 x 10(-5) nitrogen oxides eq/(kW.h), respectively, for the process combined with carbon dioxide capture and storage under the temperature of 700 degrees C and the coal concentration of 15 wt%. The comparison of the thermodynamic and environmental performance among different systems shows that the exergy and energy efficiencies of integrated supercritical water gasification of coal system combined with organic Rankine cycle are higher than those of integrated gasification combined cycle, and the environmental emissions of the integrated supercritical water gasification of coal system are less than those of integrated gasification combined cycle system. This study reveals that the integrated supercritical water gasification of coal is a relatively clean and efficient coal utilization technology with good industrialization prospects.