Release characteristics of mercury during the combustion of mixed coal

In order to improve the combustion characteristics of the mixed coal with high and low sulfur,the experiment of mercury removal is carried out in a tubular furnace after adding additives (biomass,calcium based additives,catalyst) to the mixed coal.Pure titanium dioxide (TiO2) and neodymium doped titanium dioxide (NdTiO2) are prepared by microwaveassisted solgel method.To explore the mechanism of mercury removal,the catalysts are characterized by BrunauerEmmettTellerbet (BET),Xray Diffraction (XRD),Scanning Electron Microscope (SEM),Xray Photoelectron Spectroscopy (XPS) and Energy Dispersive Spectrometer (EDS).The biomasses are analyzed by Fourier infrared spectrum (FTIR).Thermogravimetric analysis (TG-DTG) is carried out on the samples of the determined scheme.The experimental results of mercury removal performance show that the mixture of low sulfur coal A and high sulfur coal C are mixed according to the mass ratio of 4.5∶5.5.The efficiency of mercury removal is 72.7% when the biomass rape straw (the mass ratio of coal to rape straw is 7∶3),calcium based additive CaO (the molar ratio of Ca to S is 2.3),catalyst Nd-TiO2 (the mass ratio of Nd-TiO2to coal is 8%,mass doping content of Nd in TiO2 is 1%,calcination temperature is 500 ℃) are added to the mixed coal,which is 14.1% higher than the efficiency of mercury removal of adding rape straw and calcium oxide in the mixed coal,and 29.5% higher than the efficiency of mercury removal of adding rape straw in the mixed coal.The results of characterization analysis show that the rare earth ion Nd3+ doped titanium dioxide causes slight distortion of the crystal surface to some extent,but does not change its crystal structure.The specific surface area of the catalyst increases from 12.20 m2/g to 66.79 m2/g,which increases nearly 4.5 times,and improves the catalytic activity of TiO2.The results of characterization analysis also show that the removal of Hg0 by rape straw mainly focus on the adsorption of hydroxyl groups on its surface and the oxidation of oxygencontaining functional groups on its surface.At the same time,rape straw contains a large number of basic compounds,such as Fe2O3,which can catalyze the oxidation of Hg0CaO reduces the concentration of SO2in flue gas and eliminates the inhibitory effect of high concentration SO2on Hg0.The doping of rare earth neodymium increases the specific surface area of titanium dioxide,improves the redox ability of titanium dioxide.Nd-TiO2 promotes mercury removal in combination with rape straw and CaO