| Zinc is an important non-ferrous metal raw materials,its consumption is second only to aluminum and copper.Although zinc resources in China is relatively abundant,the available resources is very limited.As the resource consumption is increasing year by year,at the same time,zinc sulfide concentrate resources is decreasing year by year,the efficient utilization of sulfide and oxide mixed zinc ore in a state of accumulation or mining become the main object in the present study.How to handle such minerals reasonably and effectively has become a very important subject for study now.Based on the characteristic of the mineral bearing calcium,the way of oxidation roasting at low temperature and ammonia leaching was proposed for such complex low-grade ore considering economic benefit and technical costs.Firstly,the thermodynamics of phase trasformations of ore samples were analyzed in the oxidation roasting process.The thermodynamic analysis showed that the sphalerite and hemimorphite in the mineral were transformed to easily soluble zinc oxide by controlling the sulfur and oxygen potentials in the gas phase.While the pyrite and galena were transformed into Fe2O3 and PbSO4 respectively,sulfur in the mineral was consisted in calcine in the form of CaSO4.Meanwhile,basing on the characteristics of the ore sample bearing calcium,the reagents according to a certain proportion were used to make up a mixture that the composition was similar to the ore sample,the sulfur fixing effect of calcium in the roasting process was reserched under the same roasting condition.And the impact on the zinc-bearing mineral by iron content was studied simultaneously.The experimental results showed that calcuim in ore did have certain effect on sulfur fixing in the roasting process.The iron content had obvious effect on the mineral phase transformation of zinc-bearing mineral,affecting directly the generation of zinc ferrite.Secondly,the oxidation roasting process at low temperature of zinc sulfide contentrate on one of ingredients of mixed zinc ore was studied in the presence of CaCO3.The roasting conditions were 300? and 3h.Based on the phase detection?morphology characterization of roasting product and contrasting the zinc leaching efficiency in NH3-(NH4)2SO4-H2O solution,it confirmed that the method of oxidation roasting at low temperature could be used to handle material containg zinc sulfide in the presence of calcium carbonate,which provides a practical basis for the treatment of low-grade sulfide and oxide mixed zinc ore bearing high calcuim by the same method.The roasting test results for two kinds of zinc sulfide concentrates showed that the oxidation roasting at low temperature could not only make the phase transformation of sphalerite,but also S could be fixed in the form of CaSO4.And the best mole ratio of calcium to sulfur was 1:1.The obtained calcine was leached in thermostat water bath at 45? for 1h,the zinc leaching efficiencies of two kinds of zinc sulfide concentrate were as high as 100.00%and 92.09%respectively.Compared with that of direct ammonia leaching,the leaching efficiencies of zinc were increased by 98.21 and 90.25 percentage points respectively.Finally,two kinds of low-grade sulfide and oxide mixed zinc ores bearing high calcium with more complex composition were roasted at low temperature.The roasting conditions on the phase transformation of sulfide and oxide mixed zinc ore were researched.According to the law of phase transformation in mixed zinc ore,the best conditions for the roasting were obtained.Then the roasted products were leached in ammonia-ammonium solution.The results showed that the best roasting temperature of phase transformation in sulfide and oxide mixed zinc ore was 300?.The hemimorphite and sphalerite were transformed into ZnO in this temperature.While the temperature was too low,the zinc-bearing mineral were not transformed.The temperature was too high,the complex(Zn0.3sFe0.65)Fe2O4 was generated in calcine,and it made the soluble ZnO content decreased.The best roasting time in sulfide and oxide mixed zinc ore was 3h at 300?.The X-ray diffraction peak intensity of ZnO was the strongest and CaCO3 was completely transformed into CaSO4 at this time.When the roasting time was more than 3h,a part of ZnO reacted with Fe2O3 to generate insoluble zinc ferrite,it was bad for the extraction of zinc.Mineral phase transformation improved the zinc leaching efficiency significantly.Two kinds of sulfide and oxide mixed zinc ores were leached directly in NH3-(NH4)2SO4-H2O system,and their zinc leaching efficiencies were only 49.32%and 43.13%.While roasted at 300? for 3h,the zinc leaching efficiencies were 73.27%and 66.59%respectively,increased by 23.95%and 23.46%. |
PDF Full Text Request