Migration law and control measures of Pb element in sintering process
To clarify the migration law of Pb during sintering process,the sinter machine in a steel company was taken as the research object.The balance state of Pb was studied by the ion chromatography.The reaction behavior of Pb in the sintering process and the change characteristics of equilibrium phase composition at different sintering temperatures were obtained with thermodynamic analysis,and then the control method to defend Pb from exceeding the standard was brought.The results show that blending ore provides 96.16%of the Pb source,while sintering ore accounts for 79.82%of Pb expenditure.The removal rate of Pb in the sintering process is 20.18%.In addition,the Pb load in the sintering process is 0.06 kg/t,and the sintering flue gas emission factor is 1.22 g/t crude steel.During the sintering process,most of the Pb-containing compounds will be reacted,leading to the Pb-containing ma-terials to produce phase transformation.Pb in the raw material mainly exists as PbS.When the temperature of sinte-ring process is lower than 740 ℃,Pb mainly exists as PbSO4 in the sintering ore,while PbCl2 is in a gaseous state into the flue gas to be removed.PbSO4 is transformed to PbSiO3 and Pb monomers during the temperature increases to 1 300 ℃.It is further transformed into gaseous PbO to be removed above 1 300 ℃.In addition,under the exist-ing conditions,controling the utilization ratio of solid waste materials containing Pb,and improving the mixing effect of solid waste materials and iron ore powder to stabilize the Pb content in sinter and improving the dust removal equipment to promote the discharge of volatile Pb-containing substances are important ways to control Pb hazards.