Combustion And Gasification Of Pulverized-Coal In High Concentration Carbon Dioxide

CO2 emitted from coal combustion is the bases of greenhouse gases. In recent years, many institutions and researchers are investigated the technologies of collecting and depositing CO2 in the world. One of the important technologies is the coal combustion in pure oxygen and recycled flue gases (021C02). The available results show that the flame temperature of coal combustion in 02/C02 atmosphere is lower and the stability is poor compared with that in air. But the flame temperature can be enhanced effectively by adjusting air distribution. However, few studies have focused on the mechanism of coal combustion and gasification referred in this technology. First the theory, study method and some experimental results of coal char particle combustion has been summarized in this thesis. And some key issues in coal char combustion are also analyzed. Based on the suitable carbon combustion model, the combustion of solid carbon ball in 02/C02 atmosphere has been predicted. The carbon combustion rates in static state and in different gas temperatures, mole ratios of 02/C02, particle diameter and chem.-dynamic parameters are acquired. The experiments of combustion and gasification of two kinds of coal char particle in 02/C02 ~. 02/Ar and pure CO2 atmosphere have been carried out in thermal gravimetric analysis. The dynamic parameters of the reaction between coal char and Q2~ CO2 have been estimated from the results. The influences of high CO2 concentration on the reaction between coal char and oxygen in lower temperature have been observed. A corrected model was used to simulate the experiment process. A high temperature entrained flow reactor (EFR) was designed in this work. And the experiments of combustion and gasification of the same coal char particle in 02/C02 02/N2 and pure CO2 atmosphere have been carried out in this test system. The burnout ratios of coal char in entrained flow status and different mole ratio of 02/C02 and gas temperatures are obtained. For using the pure carbon particle combustion model on coal char combustion, a suitable method has been proposed in this thesis. The measurement data are in general agreement with predicted results using this model. The Fluent5.O software is used for modeling the coal combustion process of two-dimension axis symmetry and swirling flow vertical furnace. The flow, combustion and heat transfer model are analyzed and selected. The change of flow status, the temperature level and gas radiate characteristic in different 02/C02 mole ratio are studied. Some predicted results are compared to measured data. The principle of adjusting rule of 02/C02 mole ratio for 02/C02 combustion technology is proposed in this thesis.