Reaction Mechanism Study On Trace Elements Of Pb In The Coal Flue Gas

Toxic trace elements in coal-fired power boiler would do great harm to human health and living environment, which has attracted attention around the world. At present, the main research for trace element is focus on enrichment, distribution aspects of atmospheric transport and control technology. People know few about emissions of Pb and morphological transformation mechanism exploration become the amount is very scarce. In this paper, we counted the the microscopic reaction mechanism in coal-fired flue gas homogeneous reaction toxic trace elements such as lead chloride, bromide oxidation and theoretical calculations, and also have a deep study for multiphase adsorption about the elements of Pb on the fly carbon.The geometry optimizations of reactant and product were calculated by density functional theory of quantum chemistry, its ground-state geometry is determined by comparison with literature values and energy analysis, and `the calculating results were compared with the literature data.On this basis, theoretical exploration on the flue gas of coal-fired lead chloride, bromide oxidation and microscopic reaction mechanism of 10 reactions were studied. The geometry optimization of reactant, transition stste, intermediate and product was made at B3 LYP quantum chemistry methods. The basis set of SDD was used for Pb, and the basis set of 6-311++G(3df, 3pd) was used for nonmetal atoms(Cl, Br, O, H, and N), because its much charge is in the system, so its need to increase the dispersion function to improve its accuracy. The property of stable minimums were validated by vibration frequencies analysis and IRC. By the QCISD(T) level the activation energies were calibration(including zero-point energy correction). The reaction rate and pre-exponential factor constants within 298-1800 K temperature range were calculated from transition state theory.The adsorption of different species of unburned carbon(UBC) surface(the cluster models were construct of 4 to 5 benzene rings cluster structure such as zigzag, armchair and tip, and the unsaturated carbon atom in the edge of the cluster model were used to representing the UBC surface, and other carbon atoms were closed by H atom) were studied by the density functional theory(DET). We computed the bond lengths, bond Mulliken number and bond energy, while comparing the difference between the different adsorption and different models. The present research show that the UBC could substantially reducing gaseous lead chloride(PbCl,PbCl2), and also have apparent effort on Pb0. Cl atom will significantly increase the adsorption capacity of UBC of lead, showing strong chemical adsorption characteristics.