The Basic Experimental Research Of High Temperature Pyrolysis For Coal&Oxy-fuel Combustion For Semi-coke

In the future,China's energy structure will still be dominated by coal.About half of the reserves of coal in China are low rank coal and it is common of low efficiency and high pollution in the process of coal utilization.Therefore,it is necessary to solve the energy problem by developing the.coal-based polygeneration&oxy-fuel combustion technology.The coal-based polygeneration can optimize the utilization of coal,in which the coal gas can be used as chemical raw materials and the semi-coke can be used as the fuel in power plant.Oxy-fuel combustion has many advantages,such as high flame temperature,capturing CO₂ by low cost,low emissions of NOx.In this paper,research on high temperature pyrolysis of pulverized coal and oxy-fuel combustion of semi-coke will provide the basic experimental data for the industrial application of coal-based polygeneration&oxy-fuel combustion technology.The high temperature pyrolysis test was carried out on the drop-tube furnace using Shenhua bituminous coal.Temperature is the main influencing factor to pyrolysis.With the temperature increasing,reaction rate increases,more semi-coke&coal gas are produced,the pore structure of semi-coke is developed and the coke tar is converted to coal gas.Oxy-fuel combustion experiments are carried out on the thermal gravity platform&tube furnace using semi-coke from pyrolysis to analyze the influence of atmosphere and oxygen concentration on combustion charateristics.In the atmosphere of O₂/CO₂,the diffusion rate of oxygen is lower than O₂/N2 and the specific heat capacity is lower than O₂/N2,so the reaction rate of semi-coke decreases,reaction time is expanded and more CO is produced in the fluegas.Generally,the combustion charateristics of semi-coke become worse in the atmosphere of O₂/CO₂.When the oxygen concentration increases,the TG/DTG curves of semi-coke are shifted to the low temperature region greatly and combustion characteristics parameters become better,which indicates the combustion characteristics of semi-coke is better than low oxygen concentration.In the low oxygen concentration,the gasifcation reaction between CO₂&C is strengthened and the combustion reaction is controlled,in which the reaction releases more CO and the reaction time is expanded.The tube furnace temperature and oxygen concentration have a great influence on the combustion characteristics of semi-coke.When the tube furnace temperature is 900? or the oxygen concentration is 3%,the combustion reaction rate decreases and the gasification reaction dominates the reaction,leading to less heat release,lower maximum combustion temperature,expaned reaction time and more CO emission.Heating up and oxygen concentration will improve the combustion characteristics of semi-coke and reduce the emission of CO.