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Study Of Zinc Leaching Residue Chlorinated Roasting Experiment

Posted on:2011-07-08Degree:MasterType:Thesis
Country:ChinaCandidate:X CheFull Text:PDF
GTID:2121360305490319Subject:Safety Technology and Engineering
Abstract/Summary:PDF Full Text Request
Zinc leaching residue is produced in the zinc hydrometallurgy process with neutral or acid leaching, which seriously threatens our environment due to the hazardous materials such as lead, copper and other constituents contained. It is also perceived as a secondary resource because zinc, indium, germanium, gold, silver and other valuable elements are contained. So study on utilization of the Zinc leaching residual has both economic and environmental benefits. Chloridizing roasting is a potential technology for Zinc leaching residue treatment, which can effectively separate iron and nonferrous metals from the residue, and finally realize reuse of the resources contained in the residue.Thermodynamic calculation for the chloride reaction temperatures and feasibility analysis of the reaction between chlorinating agent and metal oxide in Zinc leaching residue was carried out by using the HSC software. The results show that metal oxides began to react with NH4Cl, MgCl2, FeCl2, FeCl3 with a starting reaction temperature all below 1000℃in N2 atmosphere, but the standard free energy change of KCl, NaCl and CaCl2 reacting with the metal oxides show positive values within the range of 100-1000℃. The initial reaction temperature of chlorination decreased and some chlorination process which can't take place in N2 atmosphere can take place smoothly in O2 atmosphere. When there was SiO2 in the reaction system, the initial reaction temperature between CaCl2, MgCl2 with metal oxides also decreased. Moreover, it was found the reaction with existence of carbon (reducing agent) was easier to take place than that without. The results of thermodynamic calculation were tested by means of thermogravimetric analyzer, characterized by weight-loss ratio. The results showed at 1000℃the weight-loss ratio of NH4Cl, NaCl, CaCl2 FeCl2 were positive in value, that is, the addition of chlorinating agents strengthened the chlorination process. The optimal technical conditions of comprehensive utilization of Zinc leaching residue via chloride roasting were determined through orthogonal testing, that is, roasting at 1000℃for 60 min with carbon content of 10% and finally the mass fraction of Zn reduced to 16.87%. After a series of experiments, NaCl was chosen as the chlorinating agent. The results showed that weight-loss ratio of Zinc leaching residue along with the volatilization rate of Zn increased with the roasting temperature and time increasing. After baking at 1000℃for 120min, the weight loss of Zinc leaching residue achieved 54.56%, and the volatilization rate of Zn reached 90.9%. Using the method of Zinc leaching residues is treatmented by chlorinated roasting to solve the environmental pollution of residues and recovery of valuable elements, and achieved good environmental benefits.
Keywords/Search Tags:Zinc leaching residues, chlorinated roasting, thermodynamics calculating, reaction weightlessness rate, volatile rate
PDF Full Text Request
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