Life Cycle Assessment And Key Problem Research Of Coal-based Polygeneration System

In recent years, the rapid growth of China’s economy greatly increase the energy consumption of the country. The production and utilization of coal plays an critical role in meeting the energy demand of the economy growth. However, the huge amount of coal consumption brings serious enviromental problems, which result in negative impact on the people’s daily life. There is an urgent demand for the development of the next generation coal utilization technology, which makes the coal use more efficient and enviromental-friendly at the same time.As a representative of the next generation coal utilization technology, coal staged-utilization system incorporates multiple coal conversion technologies. The optimized system can achieve high efficiecy while minimizes emissions to the environment. However, the lack of theoretical system study greatly slows down the development of the coal staged-utilization system. Besides electricity output, the main products of the system include the pyrolysis semi-char and syngas. Therefore, the utilization of semi-char and the steady combustion of syngas become two key challenges to improve the overall efficiency of the system.For the first time, a systematic life cycle assessment (LCA) of the coal staged-utilization system and three other advanced coal utilization systems is conducted, which are Ultra-super-critical pulverized coal power system (PC), Integrated gasification combine cycle system (IGCC), and Circulating fluidized bed system (CFB). The resources consumption, emissions to environment, and investment of the systems are evaluated and compared. Results show that, IGCC are highly efficient and clean, but the cost is high; PC has a low investment, but also has emission problems; the coal staged-utilization system reaches a high efficiency, and it has a good control on the emissions. Besides, the extra cost of the coal staged-utilization system is very reasonable, which make it very promising to future development. Regard the utilization of semi-char, this study adopts a typical Chinese lignite, and uses the semi-char of the lignite pyrolysis to produce high-quality coal-water-slurry (CWS). The coal concentration of CWS product are all above65%, and it has a good fluidity and steadiness. The Fourier Transform Infrared Spectroscopy measurement results show that, the amount of hydrophilic oxygen group of the sample decreases when the pyrolysis temperature increases, which is the reason that the quality of the CWS is improved.In this thesis, the enhancement effect of ozone addition for syngas/air premixed flames at ambient condition is investigated both experimentally and computationally. Adiabatic laminar velocities under different amount of O3addition were directly measured using the Heat Flux Method. The minimum uncertainty of the measurement is0.478cm/s, and the average uncertainty is less than1cm/s. Kinetic modeling works were conducted by integrating ozone sub-mechanism with three kinetic mechanisms:GRI-Mech3.0, Davis mechanism and USC Mech II. The research data shows significant enhancement of the burning velocities due to O3addition. The enhancement shows nearly linear increase when the O3concentration increases linearly. And the enhancement is more notable at off-peak equivalence ratios. The flame is enhanced due to the extra intermediate radicals promoted by O3...