| For a long time, the kiln slag produced in zinc hydrometallurgy was stockpiled, resulting in land occupancy, resource waste and environmental pollution. In recent ten years, a technique composed of gravity and maganetic separations was developed at home for treating kiln slags, which separated a component mainly containing carbon used as fuel, an iron concentrate used as flux in lead pyrometallurgy or as raw material in iron making, as well as a tailing used in cement production. This techinique has been applied broadly in China and most of kiln slags stockpiled historically or produced recently have been treated by it. Iron concentrate separated from kiln slags contains much valuable metals such as Ag, Cu, In, Ge and Ga, and although part of them could be recovered by using the iron concentrate as flux in lead pyrometallurgy, with the gradually elimilation of lead making process of sintering-blast furnace reduction, the utilization of the iron concentrate in this field would dispear step by step. The iron concentrate could be used as iron making raw material only in a small quantity due to its high contents of S, Zn and As. In addition, the valuable metals such as Cu, Ag, In, et al could not be recovered in iron making process. In conclusion, developing a new process of treating iron concentrate separated from kiln slag was meanful in order to reclaim the valuable elements comprehensively.Based on the chemical and phase compositions of the iron concentrate, a new process mainly composed of HCl leach and spray pyrolysis of FeCl2solution was proposed and studied systematically for the treatment of the iron concentrate. The study included:①the dissolution performances of different elements and the effects of HCl concentration variations were evaluated through the thermodynamic analysis of the leach;②the effects of leach time,HCl concentration, temperature and liquid to solid ratio were investigated experimentally on the leach efficiencies of Fe, Ag, Cu, Pb, As and Zn;③the dissolution of SiO2in the iron concentrate and its effects on the leach performences of other elements were studied;④the replacements of Cu and Ag in the leach solution by iron powders were tested;⑤the spray pyrolyses of FeCl2solution were experimented to obtain Fe2O3powders and to regenerate HC1.The results showed that main elements in the iron concentrate could be leached in HC1solutions, and with the increace of HC1concentrate, their solubilities ascend gradually. Under the optimum leach condition of leach time of120minutes, HC1concentration of6mol/L, temperature of60℃, liquid to solid ratio of10:1mL/g and stirring speed of300rpm, the leach efficiencies of Fe, Ag, Cu, Pb, As and Zn were92,21%,99.95%,95.07%,99.34%,88.59%and55.72%respectively. Under the optimum leach condition, the effects of mechanical activation on the leach were investigated in conclusions that mechanical activation accelerates the initial leach, but has no effect on altimate leach equilibra. Under the optimum leach condition other than liquid to solid ratio equal to5:1mL/g, a two stage counter-current leach was carried out, and leach efficiencies of94.15%,96.78%,97.72%,95.14%,95.80%, and87.74%were obtained for Fe, Ag, Cu, Pb, As and Zn respectively, while the residual HC1concentration was only0.19mol/L. SiO2in the iron concentrate dissolved partly, resulting in leach obstacle with the effect order of Cu>As>Ag>Pb>Zn>Fe. The replacements of Cu and Ag from leach solutions by iron powders were studied and the results demonstrated that Cu and Ag can be replced quickly and increasing temperature benefits the replacement. The replacement under the condition of excess coefficient of iron powders of1.5and pH value of0.5obtained the best replacement efficiencies of metals. The experiments of FeCl2solution spray prolysis showed that the Fe2O3powders prepared at temperature of900℃were fine and of spherical morphology, smooth surface and narrow particle size distribution. |
PDF Full Text Request