Experimental And Simulation Study On SOx Emission Under Oxy-fuel Combustion

Coal combustion supplies a large amount of thermal energy, at the same time it produces SO2, NOx, CO2 ,etc, causes serious air pollution. Oxy-fuel combustion is now a new technology which can achieve integrative control of SO2,CO2, NOx and other pollutants. Currently, there is little studies about the mechanism of sulfur phase precipitation and transformation. Based on the experiment and simulation, this paper focus on the liberation of sulfur components in coal under different conditions and the influence mechanism of flue gas composition on sulfur phase transformation.Firstly in this paper horizontal tube furnace and Drop-tube furnace were used to study SO2 liberation changes of pulverized coal under conventional combustion and oxy-fuel combustion. Explored the influence of temperature, oxygen concentration and CO2 concentration on sulfide liberation. The results indicate that under oxygen combustion atmosphere, CO2 reacts with char particles to form CO, and part of SO2 will react with CO to form COS, this is an important reason of SO2 reduction under this atmosphere. Increasing of CO2 concentration inhibits the formation of SO2. Meanwhile, the increase of O2 concentration promotes the coal sulfur liberation. The results of thermal-equilibrium method and homogeneous kinetic indicate that under oxygen-rich conditions, the change of CO2 concentration has no impact on sulfur concentration and composition in smoke. Under fuel-rich conditions, the existence of CO2 promotes the liberation of SO2 in a certain extent.Secondly thermal analyzer and horizontal tube furnace were used to study the thermal decomposition and sulfur liberation characteristics of pyrite under O2/CO2 atmosphere, the major inorganic sulfur component of coal. The results indicate that pyrite decompose to pyrrhotite firstly, then pyrrhotite will be oxided. The increase of temperature or O2 concentration shortens sulfur liberation and promotes the oxidation. Increasing CO2 concentration promotes the oxidation of sulfur steam under low temperature and inhibits the formation of SO2 under high temperature.The above research of sulfur phase precipitation under O2/CO2 atmosphere provided theoretical basis for revealing of sulfur phase transformation in the gas phase and further desulfurization.