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Study on Recovery of Zinc and Other Valuable Metals from Roasting Dust of Zinc Pyrometallurgy

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Tutor: JiangKaiXi TuGanFeng
School: Northeastern University
Course: Non-ferrous metallurgy
Keywords: Roasted dust,Recover,Zinc,Divalent metal,Hot acid leaching,Reaction Mechanism,Dy
CLC: TF813
Type: PhD thesis
Year:  2009
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Abstract:
Pyrometallurgical zinc smelting of zinc concentrates in the high-temperature oxidation roasting process will output accounted join the 20% of the total roasting soot, the complex smoke constituents, recycling difficult. Currently the the secondary roasting method used in industrial, there is serious pollution, long process, high cost, comprehensive recovery and low can not solve the problem. Roasted dust, hot acid leaching process to the new process of roasting smoke, and comprehensive recovery of other valuable metals while the recovery of the primary zinc metal, in order to achieve the roasted dust wet cleaner production processes. Meanwhile, the paper also the reaction mechanism, kinetics and process conditions on the new technology system. First roasted dust using flotation, bio-leaching and hot acid leaching exploratory experiments, the experimental results show that the product of valuable metals in the flotation process is more dispersed, unable to continue the separation recycling; biological leaching there a long time, leaching low dissolved cadmium affect the growth of bacteria and other shortcomings. Therefore, the first two methods are not suitable for processing roasting soot. The system studies the the neutral leaching roasting smoke conditions, the Mechanism and Kinetics. Ultimately determine the optimum process conditions: reaction temperature 65 ¡ã C, starting acid concentration of 90g / l, liquid-solid ratio 5:1, reaction time 60min, under these conditions, the zinc leaching rate of 71.29%, 54.84% of the slag rate 23.12% zinc slag. Kinetic studies have shown that this process is the apparent activation energy for the E = 11.92kJ/mol, in the diffusion-controlled steps. In-depth study of the thermal the acid leaching neutral leach residue conditions, the Mechanism and Kinetics. Ultimately determine the optimal process conditions were: start acid concentration of 200g / 1, the reaction temperature is 95 ¡ã C, the liquid to solid ratio of 5:1, the reaction time of 180min, manganese dioxide was added in an amount of 0.6 times the theoretical amount, in this condition, zinc The leaching rate of 93.37 percent, slag containing zinc 8.38 percent. Kinetic studies indicate that the process can be used shrinking core model, the apparent activation energy of the reaction 48.09kJ/mo1, the reaction in the chemical control steps, [H] and [Fe3] on the reaction order were 0.4, the Kinetics equation: 1 - (1-¦Á) 1/3 = 4.90 [H] 0.4 [Fe3 0.2d0-exp (-48090/RT) t A study the goethite law of hot acid leaching solution iron removal process and optimize the process conditions: pH = 3.0, temperature 60 ¡æ, reaction time 80min, air flow rate of 20L/min Under these conditions, the leaching solution, in addition to more than 99.5% of the iron rate, in addition to the liquid iron iron 0.1g / 1. Study the process of roasting soot recovery of indium, cadmium, lead, and silver. The indium recovery process, including pre enrichment indium slag acid leaching, extraction and stripping, replacement and processes and get a grade of 97.75% indium sponge, indium total recovery of 92.66%. Cadmium recovery process including leaching solution removal of copper, copper and cadmium sediment acid leaching, acid leaching solution replacement in addition to copper, acid immersion cadmium replacement in addition to cadmium and crude cadmium casting processes available grade of 98.45% crude cadmium, total recovery of 90.73%. Lead and silver recovery using flotation desulfurization and alkali fusion process, obtained 98.29% lead, 0.169% of the crude lead containing silver, lead and silver recoveries were 90.09% and 94.14%, respectively. Huludao Zinc Plant based on the results of the experiment, the expansion of hot acid leaching roasting smoke test, and validate the experimental results, 97.45% of the total zinc leaching rate. Huludao Zinc Plant produced annually 63,000 tons of roasted dust-based analysis of the trend of the whole process of the major ingredients in the roasting dust, recycled annually enter the amount of zinc in the leaching solution of 2.63 million tons, total zinc recoveries 93.93%; 2.56 tons recycled 394.9 tons of crude cadmium; crude lead 2330 tons (of leaded 2290 tons, 3.86 tons of silver); sponge indium. Roasted dust, mainly the loss of valuable metals: zinc into the leach residue 1.50% into the removal of iron slag 4.49%, other 0.08%; lead into the removal of iron slag 3.90%, into the smelting slag 3.61%, other 2.40%; cadmium into the leach residue 0.11 percent, into the iron slag 2.89%, to enter other copper and cadmium sediment and cadmium slag 0.53%; into the leach residue 0.89% indium into the removal of iron slag 4.17%, the other residue 2.28% silver into the smelting slag 1.74%, to enter the melting soot 2.63%, other 1.49%. To sum up, the thesis pyrometallurgical zinc smelting characteristics of roasted dust, hot acid leaching process through the experimental system to study the reaction mechanism of the process, the dynamics and optimum process conditions, and by expanding the test the process of verification. The advantages of the process has process short, low cost, comprehensive recovery, it not only reduces the environmental pollution, but also to achieve the comprehensive utilization of resources and clean production. Roasted dust recycling process compared with other pyrometallurgical zinc smelting processing, promotion prospects and important significance.
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