Investigation Of Coal-Based Polygeneration Systems For Production Of Power And Liquid Fuel

Synthetically combining the chemical (clean fuel) production, the power generation and the environmental protection, polygeneration system can present more opportunities to achieve higher efficiency, lower investment and less environmental impact compared to single-product systems, which is looked as one of the key sustainable development of energy technologies with promising prospect. Supported by the National Key Project (G1999022302, 2005CB221207) and the NSF of China (90210032), the major aim of this research is to investigate the coal-based polygeneration systems from aspect of fundamental theory of system integration, to reveal the specific features of the polygeneration systems, and to propose the new polygeneration system with advanced features.In the first part, the basic principle for integration of polygeneration system is systematically illuminated as "cascade conversion of material according to composition", "cascade utilization of energy according to energy level" and "integration of clean fuel production and pollutants control". From the viewpoint of chemical energy utilization, the interactions between key processes are clarified, and the mechanism of cascade utilization of chemical energy is revealed. Focusing on the cascade utilization of chemical energy level, the equations describing the characteristics of chemical energy utilization in polygeneration system are derived, and the principle for chemical energy cascade utilization is studied.On the basis of simulations of several polygeneration systems for power and methanol production, the potential for further improvement in parallel polygeneration systems are identified and the approaches are provided, and the integration features of sequentialpolygeneration system are indicated. On the basis of the internal relationships between the material conversion and energy utilization, the key integration factors and corresponding diagnostic variables are refined, and their effects on system performance are revealed.A novel coal based polygeneration system combining the power generation and liquid fuel (methanol) production in sequential configuration, especially adopting the partial-recycle methanol synthesis scheme without CO/H2 adjustment process, is proposed. Through synergetically integrating no CO/H2 adjustment process and partial-recycle methanol synthesis, this new system reaches the coupling between material conversion and energy utilization, and upgrades the system performance distinctively, whose energy saving ratio is as high as 15%. The interactions between material conversion and energy utilization play an important role in polygeneration system integration.Based on the fundamental analysis of CO2 separation processes, the chemical energy utilizations in different CO2 separation methods (fuel gas separation and flue gas separation) are compared, and the key factors for energy consumption are identified. A polygeneration system with CO2 recovery is investigated. The results show that the polygeneration system has an attractive potential for greenhouse gas control.