| The emission of a large number of greenhouse gases is a significant reason of Global Warming which has been a serious threat to human survival and development. As CO2 is the most harmful greenhouse gases, so the research of CO2 effective separation and collection is a common goal and also a direction of development all over the world. The energy conversion systems based on the chemical looping technology which could be nearly zero emission is a novel conception in the research field of the energy and the environment. The energy conversion systems based on the chemical looping technology were simulated and studied on the software– Aspen Plus in this paper.In order to verify the correctness of the methods used during the simulation of complex energy conversion systems as well as the usability of the simulation result, the Aspen Plus was firstly conducted on a 300MW coal-fired power plant in Hunan province. The models of various subsystems were established and a thermodynamic simulation of the system has been realized. The simulation results obtained were compared to the actual performance test data and it shows that the maximum corresponding error of the two results is only 1.13% which fully satisfies the requirements of engineering applications. At the same time, the exergy analysis of the thermal system shows that the exergy loss in the boiler is the biggest which is 85.68% of the total exergy loss in the system. In addition, the exergy efficiency of the system is just about 41.33%. Therefore, an enhancement of the exergy efficiency of the boiler will significantly increase the exergy efficiency of the whole system.On this basis, chemical looping combustion systems and conventional combustion systems fueled by CH4 and coal were established by using the Aspen Plus in this paper. The detailed simulation and thermodynamic analysis were realized and the optimal operation conditions and simulation results have been obtained. Comparing to the conventional combustion, the chemical looping combustion has lots of advantages as follows: The combustion temperature is lower than 1500℃, and there is no thermal or fast type NOx; it is convenient to separate and storage the CO2 in the flue gas. The concentration of the CO2 could be 98% after condensing the water stream; the fuel does not contact the air, so the fuel type NOx can not be produced; the thermal efficiency and the carbon capture efficiency are higher. The thermal efficiency of the chemical looping combustion system is 3%～4% higher than that of the conventional combustion system. The carbon capture efficiency of the chemical looping combustion system could reach to be 99%.The reforming and the hydrogen production by using the chemical looping technology is a new conception. Three different hydrogen production systems based on the chemical looping technology were simulated on the Aspen Plus in this paper. The CH4 was selected as the fuel. The analysis of thermal performance and the optimization were performed. The comparison of the three systems shows that: in CH4 autothermal reforming system, the mass and the volume flow rates of Ni-based oxygen carrier are the lowest, which is 0.12624271 kg/mol CH4 and 1.9701×10-5 m3/mol CH4, respectively. In addition, the transmitted energy is the smallest in this system and the reforming gases have the greatest lower heating value which is 11376.04kJ/Nm3; in CH4-steam reforming system, the efficiency of the cold syngas production using Ni-based oxygen carrier is the highest, which is 82.78%. The reforming gases have the greatest gross heating value which is 12771.29kJ/Nm3 in this system; the concentration of H2 in the cracking gas in the Fe-based system is the highest, which is 97.84%. The CH4 conversion efficiency in this system is 100% which is also the highest. Each of the three hydrogen production systems has its unique advantages and which one will be chosen should be according to the actual requirement. |
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