Novel Thermodynamic Cycle With Cascade Utilization Of Chemical Exergy And Physical Exergy Of Fossil Fuel

To resolve energy and environmental problem is the general objective of the research of energy utilization system in the 21st century. Exploring the new principle of energy transformation and utilization and innovating the new thermodynamic cycle are the main research directions of the generalized total energy system with gas turbine in the future. Focusing on this objective, the main study of this dissertation proposes the feedwater heating combined cycle for repowering the conventional coal-fired steam power plants, the chemically intercooling thermodynamic cycle and the solar thermal power system with the integration of methanol fuel. Based on repowering the existing coal -fired steam power plants of below 200MW in China, Feedwater heating combined cycle system is investigated. Through the graphical exergy analysis of EUD, the study on the internal exergy consumption is carried out. Their thermodynamic performances of coal-fired steam power plants of 50MW, 125MW and 200MW are, respectively, investigated by analyzing the interactions between system reforming and modification of the vane of the steam turbine with all-three dimension technology. For reformed system, the effect of cost ratio of natural gas to coal on its electricity production cost is evaluated by static economic analysis. For the energy transformation in a conventional power system, the largest exergy consumption occurs in the process of the conversion of chemical energy of fuel into the thermal energy. Hence, how to reduce the destruction of energy level of chemical energy in the combustion of carbon fuel is an important problem for us. The new principle of cascade utilization of chemical energy of carbon fuel is proposed and investigated fundamentally. The interactions among chemical exergy of fuel, the availability of work in chemical reaction, physical exergy are identified, and also disclosed by energy level. Based on these fundamentals, the indirect combustion of methanol is proposed in which the methanol decomposition is coupled with the low energy level of physical energy. The characteristics about the indirect combustion of methanol are investigated. According to the above new principle, the gas turbine combined cycle with the integration of low–temperature waste heat and methanol decomposition is proposed. To predict the effect of solar thermal decomposition of methanol and to disclose about special characteristics, the reactivity of methanol decomposition is experimentally investigated. To increase the conversion rate of methanol at temperature of 150℃~200℃, the improvement scheme for methanol decomposition is proposed. To resolve the intermission of solar energy in the power system and to increase the competition of renewable energy, a new solar thermal power cycle is proposed where the methanol decomposition is integrated with middle-temperature solar thermal energy. The features of the proposed cycle are investigated on the basis of the role of indirect combustion of methanol. The performance of thermodynamic cycle is evaluated and the effects of key thermodynamic parameters on its performance are analyzed. The promising results obtained here is important for the extensive investigation of the new principle of the conversion chemical energy of carbon fuel and innovative power system with both saving energy and suppressing environmental impact.