Experimental Study On Combustion Characteristics And Kinetics Of Pulverized Coal Under Oxygen - Enriched Atmosphere

Energy is the foundation for human society existence and development. Coal is the main energy source in Chinese energy consumption structure. Pollution caused by emissions of combustion of coals is very serious. So people are trying to develop a new alternative technology which is economical and energy saving. Oxygen-enriched combustion is a kind of technology which consumes more oxygen than air. High concentration of carbon dioxide can be obtained and emissions of pollutants from combustion of coals can be controlled comprehensively when this new technology is utilized. The technology of oxygen-enriched combustion is new and efficient, which is considered to be a technology recycling on resources.Brown coals of Xiaolongtan and bituminous coals of Fuyuan are selected as investigating objects in this paper.The combustion characteristics experiment utilized a instrument called STA449F3Jupiter simultaneous thermal analyzer is carried out at the reaction conditions of O2/N2and different oxygen concentration(21%,30%,50%,80%). The results show that:(1) When O2concentration increases from21%to80%, the temperature of ignition and combustion of two kinds of coals are all decreased. The ignition temperature decreases from321.1℃and483℃to288.4℃and449.3℃, and the combustion temperature from634.5℃and711.8℃to447.9℃and599.3℃respectively. While maximum weight loss rate increases gradually, the burning time is shorten and combustion velocity is improved. The combustion characteristics of coals at oxygen-enriched condition can be improved when oxygen concentration is increased. When oxygen concentration reaches to30%, the parameters of combustion characteristics of coals change slowly. Considering the cost of oxygen, the optimum oxygen concentration is30%.(2) The thermo gravimetric curves of coals deviate to the right side when heating rate increases from5K/min to20K/min. At this concision, ignition and combustion of coals can be advanced and the combustion time of coals is shortened. The smaller of coal granule size, the lower of ignition and combustion temperature. The combustion performance is different based on different kinds of coals. At oxygen-enriched combustion, the ignition of coal is lagged and average weight loss rate decreases. That means combustion characteristics of coals are changed by carbon dioxide.(3) Thermo gravimetric Analysis results show that ignition mode transforms from heterogeneous to combined mode when oxygen concentration increases gradually at oxygen-enriched condition. When heating rate is lager, small particles of coals can combust in heterogeneous mode.(4) The Coats-Redfern integral method、Ozawa method and Kissinger method are used to calculate kinetic parameters of these two kinds of coals. Figures, X-axis is1/T and Y-axis is In [G (α)/T2], can be obtained based on12species of mechanism function. The optimum curve of correlation coefficient parameters can be determined through investigating the figures. According to the investigation on figures, the kinetic model of two kinds of coals at conditions of21O2/79CO2and heating rate of20K/min can be obtained. And there is a compensation effect on activity energy and frequency factor of these two kinds of coals at different concentration of oxygen.