Research On Recovery Of Zinc And Lead From Flotation Tailings Of Copper Smelting Slag By Chlorination Roasting

Copper is a critical primary material in modern industry and is widely used in national defense,military industry,aerospace,and other fields.At present,more than 80%of refined copper in the world is produced by the pyrometallurgical process,which will produce a large amount of Cu-containing waste slag dominated by copper smelting slag.Copper smelting slag is a typical secondary resource of nonferrous metals,containing large amounts of valuable components with great recycling value.However,it is difficult to recover the valuable components from copper smelting slag by the traditional metallurgical processes because the slag has a stable structure and complicated multi-component system.Most copper smelting enterprises only use the slow cooling flotation method to separate and recover Cu from copper smelting slag,without considering the recovery of Zn and Pb components in flotation by-products（i.e.,flotation tailings）.This paper proposed a chlorination-volatilization method using CaCl₂ as a chlorination agent to selectively separate and recover Zn and Pb in flotation tailings of copper smelting slag.The possibility of chlorination of Zn and Pb components was evaluated,the chlorination mechanism of Zn and Pb was to be clarified,the kinetic model of each stage of the chlorination roasting process of flotation tailings of copper smelting slag was established,the effects of various factors on the recovery efficiencies of Zn and Pb in the chlorination roasting were investigated.The main content of the study is as follows:（1）The thermodynamic and phase transition behaviors of the chlorination process were investigated.The results demonstrated that gaseous CaCl₂ is easily decomposed by O₂ and H₂O to produce Cl₂ and HCl,respectively.Zn-containing phases and Pb-containing phases are easily chlorinated by Cl₂ and HCl.After the Cu component in the slag is transformed into Cu Cl₂,it is further transformed into Cu Cl at a high temperature.Fe₂SiO₄ and Fe₃O₄ in slag are easily oxidized to Fe₂O₃.（2）The dynamic behaviors of Zn/Pb chlorination and Fe₂SiO₄/Fe₃O₄oxidation during the chlorination roasting process were studied.The kinetic models were established by reaction kinetic experiment and thermal analysis kinetics.The results demonstrated that Zn and Pb chlorination followed the shrinking unreacted core model,and the rate-controlling step was the chemical reaction.The apparent activation energy of the Zn and Pb chlorination was 83.5 k J/mol and 111.8 k J/mol,respectively.Increasing the roasting temperature had a significant effect on improving the chlorination rate.The apparent activation energy of the iron oxidation reaction during the chlorination roasting process was 101.7k J/mol.The probable mechanism function for describing the process was G（α）=[-ln（1-α）]^1/2.The oxidation reaction rate of Fe₂SiO₄ and Fe₃O₄can be controlled by adjusting the roasting temperature and roasting time.（3）The effects of the roasting temperature,holding time,the dosage of CaCl₂,and airflow on the recovery efficiencies of Zn and Pb during the chlorination roasting process were studied.When the flotation tailings are10 g and the airflow is 100 m L/min,the optimum condition obtained by Box-Behnken design of response surface method was that roasting temperature was 1043°C,holding time was 27 min,the dosage of CaCl₂was 30.7 wt.%,and the recovery efficiencies of Zn and Pb were 98.31%and 99.98%,respectively.There are 57 figures,25 tables and 127 references.