The Study On Energy & Power System Of Partial Coal Gasification And CO₂ Capture

Harmonious development of energy resource, environment and economy is the important forward direction of energy research in 21^st century. Global warming climate brought by main greenhouse gas CO₂ has been the focus and difficulty of energy science. CO₂ control of coal-based energy power system has been the topic of energy field, and the production of hydrogen that is clean energy carrier has been also paid attention. Supported by the National Natural Science Foundation of China and the Hi-tech Research and Development Program of China, from the aspects of key process mechanism, system integration and technology pathway, integration theories of coal gasification system and dual fuel reforming system are studied, and partial coal gasification system with CO2 capture and dual-fuel system with hydrogen and electricity production are proposed, and also, economic and envirmental benefits brought by the new systems are predicted, technology pathway suitable for China is suggested.To exploit high-efficiency and friendly-environment clean coal power system, integration mechanism of fuel conversion processes and integrative mechanism of CO₂ control in coal gasification system are developed. The equation of cascaded utilization of chemical energy and physical energy for integration of processes that include coal gasification, syngas combustion and char combustion is built. The equation reveals that the relation of composition and energy level to energy matching during the integration of the fuel conversion processes. This investigation shows there is an optimized GCCR (gasification carbon conversion ratio) to make irreversibility of fuel conversion processes minimal. Furthermore, integration relation between fuel conversion process and CO₂ separation process is analysized. It was revealed that partial coal gasification system adopting oxy-fuel combustion realizes integration of fuel conversion and CO₂ control.Aiming at high invest cost of IGCC system, based on cacaded conversion of fuel, the principle of cascaded utilization of chemical energy and physical energy, and integration mechanism of CO₂ control, partial coal gasification combined cycle with CO₂ capture is proposed. The performance characteristics of the system are revealed. Within the feasible range of variables, thermal efficiency of the system has maximal value. From the aspects of thermodynamic, economic and environmental performances, the new system is compared with IGCC system. The comparison shows the new system realizes higher thermal efficiency, lower investment cost and lower CO₂ separation energy consumption.In the face of China's energy resource structure with more coal and less natural gas, and aiming at a large of high quality fuel is consumed in the conventional reforming process of natural gas, dual fuel (natural gas and coal) energy system with hydrogen and electricity production is proposed. Based on the conception of energy level, the level equation of fuel conversion process, which describes the complementary utilization of coal and natural, is deduced. By the use of the equation, the characteristic of cascaded utilization of energy during chemical energy release of dual fuel is revealed. By the use of EUD, and compared with conventional systems with hydrogen production, the reasons of higher thermodynamic performance of the new system is explained.Based on sustainable energy development strategy of China, by the use of the MESSAGE model, scenarios of energy supply system of electricity and transportation are investigated, which include partial coal gasification system and dual fuel system with methanol production proposed by this thesis. Through comparison of different CO₂ control tenology pathways in electricity industry, it was pointed out that the clean coal technology such as the partial coal gasication system can meet harmonious development of energy, ecnomy and envirment. It is expected to be promised pathway suitable for China for CO₂ mitigation. Furthermore, speedy increasing fuel for transportation is an important reason that oil import increase speedily. This study use dual fuel system with methanol production as typical case, and predict scenario development of the new-type fuel for transportation substituting for oil, and point out that techonology patyway of economic feasible coal substituting for oil is necessary.