A Novel Power Generation System Based On Coal Gasification In Supercritical Water And Principle Of Its Energy Conversion

Coal is the most important fuel for power generation at the present time. But thecoal combustion in the air produces NOx, SOx, CO2and other pollutants inevitably. Coaland supercritical water gasification process is an efficient technology to convert coalcleanly. To take advantage of the unique properties of supercritical water, coal can beconverted into H2with clean high calorific value and CO2, and the pollutants such as N,S are discharged from the reactor as solid residual. This paper proposes a novelthermodynamics cycle power generation system based on coal gasification insupercritical water, and adopts the methods of energy analysis and exergy analysis tostudy the energy consumption process. In addition, in order to achieve the aims of cleanusing of coal and energy-saving and emission-reduction, this paper also make a furtherexplore of the mechanism of energy transformation based on the concept of energygrade and the Energy Utilization Diagram Methodology.Firstly, a novel thermodynamics cycle power generation system based on coalgasification in supercritical water was proposed. Coal gasificated in supercritical water,then the mixed medium of supercritical water and the gasification products enter thehigh pressure turbine to generate electricity, which makes full use of the energy carriedby the supercritical water from the reactor outlet. And make the gasification productscan generate oxidizing reaction for steam heating again. Then pass the steam into thelow pressure turbine to generate more electricity, which saves the energy consumptionof hydrogen separation and purification. And it also turn the hydrogen into theelectricity which is wider application.Secondly, by analyzing the energy and exergy analysis in the new system, find out the weak links of the system. And take the conventional system which coal is directburning to drive the supercritical steam turbine reheat cycle system as a reference, findthat the energy efficiency and the exergy efficiency of the new system is higher, andpoint out the key processes affecting the energy efficiency and the exergy efficiency isthe chemical reaction processes, including gasification and combustion processes.Finally, based on the concept of energy grade and the Energy Utilization DiagramMethodology, and through the study of the energy grade relationship between thechemical energy and physical energy in the process of coal gasification in supercriticalwater, reveal the deep reasons of exergy loss generated in the key process, and clarifythe mechanisms of the reduction of exergy losses and the promotion of heat source levelin the new system. Which provides a theoretical basis for the design and optimization ofpower generation system based on coal gasification in supercritical water.