Studies On Mercury Transformation And Enrichment Mechanism On Particulate Matter In Combustion Flame

In China, coal accounts for 70% in the structure of primary energy consumption, nearly 30% of mercury in the atmosphere comes from coal-fired power plants. Mercury is one of the main pollutants produced in the combustion process of coal, its mechanism of formation, release and its efficient removal technology become the main subject of research.This study designed and established a experimental system, showing as follows: using a self-designed inverse diffusion flame burner, fluxed the Hg vapor into the combustion system using ethylene as the fuel, samples were restored and digested with the Ontario-Hydro Method, then analyzed by the CVAAS; studies on the enrichment law influences of particle state mercury for fine particulate matter were researched by changing species and concentrations or the air-fuel ratio of gases into the burner. Meanwhile, the influence of different flue gas atmosphere on the oxidation of mercury was simulated with Chemkin, and the changing rates of reaction of the four primitive reactions in different temperatures were explored with Gaussian. By experiment and these simulations, the mercury speciation transformation and enrichment rules of fine particulate matter in the flame were obtained.The study shows that the increase of air-fuel ration and HCl concentration can improve the formation rate of mercury; the effect of SO2 on the generation of particle state mercury is bidirectional. The formation rate of particle mercury in the combustion process is the comprehensive result of soot concentration, flame temperature, air-fuel ratio and combustion atmosphere, etc. The adsorption of mercury on soot mainly include physical adsorption（mercury is accumulated on the surface of particles with large specific surface area） and chemical adsorption（functional groups of-OH,-C=O,-COOCH3 can improve the mercury adsorption of soot）. Simulation results show that:（1） the Cl element can promote Hg0（g） translating into HgCl2（g）.（2） S element can not only promote but also restrain the generation of Hg2+, high value of S-Cl will suppress the generation of Hg2+;（3） the O element has a promoting effect of oxidation on mercury, but its role is much less than the Cl element, also not as good as SO2;（4） the influences of NOx on the oxidation of mercury were reflected through the generation of NO while its decomposition;（5） The relatively lower NO concentration can promote the process of oxidation of mercury while the higher concentration can inhibit the oxidation of mercury.（6） The C element can inhibit the oxidation of mercury. Fly ash absorb mercury though physical adsorption（Active adsorption sites are generated at the surface to adsorb mercury.）, and chemical adsorption（ promoting Hg0 into Hg2+ by the element of Fe, Al, etc.）.（7） Combustion temperature and flue gas atmosphere can also affect the oxidation of mercury. The influence of Cl, S, O to the mercury oxide obtained from the experiment results are matched up with result（1）³ of simulation research, showing that the experiment was in accord with simulation.