Analyses on Supercritical Water Gasification of Coal and Integration of Novel Power Generation Systems

Author:Chen Zhe Wen

Supervisor:gao lin

Database:Doctor

Degree Year:2018

Download:452

Pages:127

Size:10751K

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The air separation units in the conventional coal gasification technologies can be omitted,and clean hydrogen-rich syngas can be obtained when supercritical water is chosen as the gasification agent for coal.Supercritical water gasification is a promising technology for clean and efficient coal utilization.Supported by the National 973 project,the major aims of this research are to investigate the supercritical water gasification of coal from the aspects of fundamental theories,integration of novel power generation systems.In the aspect of fundamental theories of supercritical water gasification of coal,the characteristic regulations of the energy conversion between the chemical energy of the coal and thermal energy in the gasification process were studied based on the energy and exergy balances of the process.The upgrading ratio relation of the energy in the supercritical water gasification process heated by external combustion was set up,and the upgrading ratio mechanism of the reaction heat was revealed.On the other hand,the graphical exergy analyses(EUD methodology)were adopted to compare the energy release profile on the processes with supercritical water gasification of coal and the pure oxygen gasification technology from the aspects of cold gasification efficiency and exergy efficiency.In the aspects of novel power generation systems integration and integration principles,several power generation systems were proposed,and analyzed based on the differences in the integration methods between utilization about sensible heat of the gasification product and power generation units.The coal-water-slurry concentration and integration methods of the sensible heat decide the allocation proportions of the energy input in the utilization terminal,which influence the thermal efficiencies of the systems.Under the research conditions of this study,the thermal efficiencies of the systems increase with increasing coal-water-slurry concentration.The system with parallel chemical heat recovery has the highest thermal efficiency due to the less exhausted energy in the condenser and relative large amount of heat recovery.From the comparison of the four power generation systems,the basic integration principle for the power generation systems integrated with supercritical water gasification of coal is as follow:optimizing the utilization ways about the sensible heat and composition of the gasification product,and transferring more energy to the combined cycle.The power generation system with parallel chemical heat recovery has advantages over most coal-fired power plants and IGCC(Integrated Gasification Combined Cycle)plants.In the aspect of novel power generation systems integration on the supercritical water gasification with CO2 capture,the power generation system with integrated syngas separation and CO2 capture,and system with syngas direct combustion and CO2 capture are proposed and analyzed based on the basic features of high pressure and clean composition of the produced syngas.In the power generation system with syngas direct combustion and CO2 capture,the net thermal efficiency of the system can reach 38.3%when the CO2 capture efficiency approaches 100%.The system has advantages over most power plants with oxy-fuel technology,post-combustion technology,and pre-combustion technology.In the aspects of experiments on the key processes in the supercritical water gasification of coal,the solubility measuring laboratory furniture was built to measure the solubility of the gas mixture comprised by H2,CO2,CO,and CH4 in the water.The work pressure and temperature of the laboratory furniture can reach 25 MPa and 180℃,respectively.The solubility of the gas mixture in the water can be measured in a wide range of pressure by the laboratory furniture.The data can be the theoretical reference for the design of pipelines,heat exchangers,and supercritical turbines in the energy systems integrated with supercritical water gasification of coal.