Analysis On Characteristics Of Coal Based Polygeneration System

The energy structure based on coal in China will not be changed in the next decades, but huge damage had been created as a result of conventional utilization of coal, which is a non-sustainable development way. Coal based polygeneration system is a sustainable energy system with integration of energy, resource and environment. It is Proposed due to the non-sustainable development of the energy system in China and hoped to fulfill the requirements of power, liquid fuels and chemical needed by the development of society and economy. In order to optimize the overall efficiency, minimize the pollution and simplify the different process and equipment, it is necessary to combine the production of energy and chemical which are independent systems based on coal gasification.Some relevant researches about the characteristics of coal based power and methanol polygeneration system have been done in this thesis, based on a lot of references and sponsored by Programs for Science and Technology Development from the Science and Technology Commission of Shanghai. Work as follows:First, on the basis of structure and flow scheme characteristics of coal based power and methanol polygeneration system, the basic models, including the Texaco gasifier, air blown gasifier, cold gas cleanup unite, gas turbine combine cycle unite and methanol production unite, have been built and the models'results are good agreement with the data published. That is to say the models were qualified to simulate the coal based power and methanol polygeneration system.Secondly, according to the integration theory and principle of the power and chemical polygeneration based on coal gasifier, models of IGCC system, coal based power and methanol parallel system and coal based power and methanol serial system were built and the different systems'performance were calculated. The result was presented that the coal based power and methanol parallel system is superior to coal based power and methanol serial system in the overall.Finally, a new coal based power and methanol parallel system without water gas shift was first suggested. The new system regulates the C/H ratio of raw gas for methanol production by membrane separation technology which separates the hydrogen from raw gas for CC. The model of coal based power and methanol parallel system combined with membrane separation for hydrogen production was built. The performance of the new system was calculated and comparison between those two systems was made. The different parameters of the new system, such as oxygen-coal ratio, water-coal ratio, the percentage of raw gas for methanol production, have a great influence on the syngas composition of the air blown gasifier and the performance of system. These results show that:when the coal-water ratio is increasing, the volume fraction of CO in the syngas is increasing significantly, while H2 is decreasing slightly, methanol production is increasing and power is decreasing; when the oxygen-coal ratio increases, the volume fraction of CO and H2 are decreasing, methanol and power are decreasing too; when the gas ratio for methanol production is changed from from 0.2 to 0.3, methanol production is increasing while power is decreasing.