Study On Simultaneous Equilibrium About Smelting Process In The Functional Area Of Kivcet Flash Furnace

Abstract:As more attention is paid on to the environment, the traditional lead smelting process has been eliminated gradually due to its severe pollution of flue gas. Large amounts of zinc leaching residues need proper treatment because of environmental damage. Kivcet direct lead smelting process is developing rapidly in recent years, it has no mandatory requirements to the amount of lead in the raw materials, thus it can dispose raw materials with zinc leaching residue.There were few reports on the thermodynamics of multiphase equilibrium about Kivcet direct lead smelting process, this essay studied on the Pb-O-S system with the principle of multiphase equilibrium. The number of independent chemical reaction taking place in the flash functional area was determined by phase rule. Related reactions were chosen to study on simultaneous equilibrium of multiphase and multielement system, and the influences of atmosphere to the system were discussed. The thermodynamic model of "temperature and atmosphere composition" was established."Method of equilibrium molar quantity" and "method of equilibrium reaction progress" were used to solve equilibrium partial pressure and total pressure of gas in the system.The results show that the output of lead sulfate would increase with the increase of preliminary oxygen level at high temperature, while low oxygen input hardly resulted in the generation of lead sulfate. Considering the subsequent treatment of the products, it is suggested that high oxygen input should be chosen to avoid the generation of lead matte which may cause adhering slag and affect the whole process.To avoid producing lead matte in Kivcet flash smelting process, the influences of atmosphere and temperature on the products were studied. The results showed that the content of lead in the product was low as a result of sublimation of lead sulfide, and the product mainly consisted of copper matte and slag in the form of Ca-Fe-SiO2under pure nitrogen atmosphere. The final products were lead matte and slag in the graphite crucible under the condition of pure sulfur dioxide atmosphere and1309 ℃. When the ratio of nitrogen and oxygen was7:3, the raw materials were firstly oxidized into lead oxide and then melted, which can avoid the sublimation of lead sulfide and the generation of lead matte at high temperature.