Effect of Mineral Compositions on Volatilization of Pb during Coal Combustion

Coal-fired power plants are the main sources of atmospheric Pb. The mineral composition of coal is an important factor of the trace element distribution. The Pb volatilization characteristics of the anthracite, lignite and bitumite were examined in the horizontal tube furnace. SiO2, Al2O3, CaO and Fe2O3 were chosen as the mineral compositions and PbO was chosen as Pb source to investigate the effect of minerals on Pb volatilization during coal combustion. The results indicated that the occurrence modes of Pb and mineral composition were major factors in Pb volatilization and the coal containing more silicon and aluminum had the lower Pb volatilization rate. The intrinsic minerals in coal immobilized the released Pb through both physisorption and chemisorption. The combustion and thermogravimetric investigation showed that the Pb capture efficiency of the four minerals ranked as SiO2>Al2O3> CaO> Fe2O3. The formation of the non-volatile materials such as PbSiO3, Ca2PbO4 and PbFe12O19 accounted for the capture mechanisms of SiO2, CaO and Fe2O3, while Al2O3 stabilized Pb via the physisorption. The synergy of SiO2 and Al2O3 exhibited the most superior capture efficiency on Pb, which provided references to the preparation of oriented Pb removal adsorbent.