The Effects Of Steam On Coal Char Combustion Under Oxy-fuel Atmosphere

Oxy-fuel combustion is suggested as one of the possible, promising technologies for Carbon Capture, Utilization and Sequestration from power plants. Since a large number of exhaustgas circulation, H2 O concentration(15%-30%) in O2/CO2 combustion is obviously higher that in conventional air combustion, even up to 40% in the system adopting wet exhaust gas circulation. Therefore, under oxy-fuel atmosphere considering the effect of water vapor on pulverized coal combustion is very meaningful. The paper used the isothermal thermo-gravimetric platform?high temperature horizontal furnace platform and CFD software numerical simulation study of water vapor on the char combustion characteristic respectively, flue gas composition?temperature field distribution in the furnace and The proportion of different reaction of the carbon consumption.Frist, Three different degree of the coal(XLT?SC and MAS) were chosen and prepared coal char.Effects of steam gasification on coal char combustion in oxy-fuel combustion atmosphere were studied through the isothermal thermo-gravimetric platform. The variations of char during the process of combustion were measured by N2 adsorption analyzer at a low temperature and scanning electronic microscope(SEM). The results show that under low oxygen concentration, water vapor affects the coal char combustion significantly, which noticeably increases the weight loss rate and reduces the burning time. The influence of steam gasification on char combustion decreases with the increase of oxygen concentration. Moreover, With the rise of reaction temperature, R0.5-index increased gradually. When the environment temperature is 1000 ? and 20% water-vapor exist in the environment, the R0.5 grow fastest. Additionally, the char of specific surface area increase and pore structure is abundant after adding water-vapor.Second,in high temperature horizontal furnace platform, research on XLT's char under different oxygen concentration(0%?5% and 10%), temperature(1100?C?1200?C and 1300?C) and water vapor concentration(10%, 20%, 30% and 40%) impact on the gas release. Studies have shown When oxygen concentration is 5%, the amount of hydrogen and Carbon monoxide is the largest; With the deeper the degree of coal char, It is difficult for gasification to happen, However, XLT's coal-char gasification is the easiest response.At last, Using CFD software simulate the influence of gasification on coal char combustion in the 0.3MWth vertical coal combustion furnace, which located in the State Key Laboratory of Coal Combustion of Huazhong University of Science and Technology. The fluent software was used to simulate the effects of steam gasification on coal char combustion in oxy-fuel combustion atmosphere,analyze the temperature distribution within the furnace after addition water and calculate all kinds of char-reaction ratio. Studies have shown that with the increase of water steam concentration, the corresponding maximum temperature increasing and the highest temperature of the center line of the corresponding distance over backwards. When water vapor concentration is certain, the peak of H2 increase as as the oxygen concentration increased. The main reason is that the gasification reaction is endothermic reaction. when add the appropriate oxygen, the surface temperature of the char will increase.