The Analysis And Numerical Simulation Of Mercury Transformation In Coal Combustion Process

With the rapid economic growth and strong demand for the country's power industry, coal-fired power plants as the main power plants and the world of today's China. It also brought the power industry's environmental problems.Power plant emissions of mercury have been caused great attention for its harm to human body.Therefore, the conversion characteristics of standard and organize all types of mercury during combustion of mercury compounds is particularly important to control mercury emissions.Firstly, the use of chemical kinetics software CHEMKIN, by controlling the variable method, O2, NO, H2 O, SO2, CO2 impact over time and temperature changes of the components for flue gas mercury HCl during combustion with morphological changes. The results obtained show that: the presence of Cl atoms will facilitate the conversion of elemental mercury to oxidized mercury, within a certain range to increase the amount of HCl in favor of mercury oxidation. O2 will promote the oxidation of Hg, but significant role than HCl. NO According to its geographical smoke promote oxidative atmosphere both elemental mercury also can inhibit the oxidation of elemental mercury, in an oxidizing atmosphere, NO presence Hg0 oxidation rate of increase. H2 O presence inhibits the generation for Cl, but its presence will increase the rate of oxidation of mercury. HCl in the presence of no help when SO2 conversion of mercury, especially in low-temperature environment, SO2 volume fraction, the higher the rate of oxidation of elemental mercury; and the presence of CO2 will inhibit the oxidation of mercury.In the application CHEMKIN smoke component analog optimum conditions,combined with the actual size of the boiler, coal, operating parameters, the boiler load and other conditions, set the boiler optimum initial concentration of the substance of the argument. Use fluid dynamics software FLUENT, 1000 MW ultra-supercritical coal-fired boilers for the prototype, choose from a variety of basic models to simulate realistic boiler furnace draw a three-dimensional temperature field and concentration field. In order to analyze the internal mercury form distribution in the boiler furnace to prepare.The chemical reaction mechanism contains mercury writing CHEMKIN import FLUENT software selection combustion model coupled EDC calculated the concentration within the coal-fired boilers, etc. Hg0 and HgCl2 temperature, flue gas flow distribution. Conclusions drawn from the analysis:Mainly in the form of mercury Hg0 distributed in the burner zone and the center of the upper part of the boiler furnace zone near the furnace exit temperature, mole fraction of up to 4×l0-3, at a temperature in the region 900-1100 K thermodynamic instability converted to elemental mercury oxidation state. When the temperature is lowered to 900 K or less,due to the occurrence of the reaction of Hg0 HgCl, with decreasing temperature hasbeen oxidized to HgCl2, so cold ash bucket, horizontal flue and the flue tail region oxidized mercury is mainly present form. Increasing the temperature drop rate will eventually suppress the generation of HgCl2, control the temperature optimum conditions 700-1000 K conditions, increasing the oxygen content of the flue gas to provide a suitable oxidizing atmosphere can cause flue gas converted to elemental mercury oxidation state. Gas residence time is longer the full reaction, but the biggest impact the flue gas components HCl conversion of mercury species, whose existence will greatly improve the conversion rate of zero-valent mercury. SO2 and NO affect the results only in an atmosphere containing HCl in only performance significantly.