| In the process of copper pyrometallurgical smelting,a huge amount of arsenic evaporated into dust,forming arsenic-containing copper dust,which is potentially harmful to the environment.The composition of high arsenic copper dust is complex.On the one hand,it contains valuable metals such as copper,lead,zinc,tin and indium,and has great recycling value;on the other hand,it contains high arsenic content,resulting complex in harmless and resourceful recycling process.Efficient separation and harmless treatment of arsenic and other components in the dust are the key and difficult points in the treatment of arsenic-containing copper dust.In this paper,the application of comprehensive recovery of valuable metals from arsenic-containing copper dust was studied.The main contents and conclusions of this paper are as follows:1.Mechanism of arsenic evaporation in arsenic-containing copper dust during low temperature roastingBased on the direct evaporation experiment of arsenic-containing copper dust,the mechanism of arsenic evaporation in arsenic-containing copper dust was studied.The results show that Pb3(As O4)2 and Zn3(As O4)2 are the main limiting factors for arsenic evaporation.In order to separate arsenic efficiently,the formation of Pb3(As O4)2 and Zn3(As O4)2 should be inhibited or broken at low temperature.2.Selective removal of arsenic by vulcanizing experiments from arsenic-caontaining copperBased on the phase structure and mineral phase distribution characteristics of arsenic-containing copper dust and the difference of vapor pressure between As2S3,As2 O and other components in the dust,sulfur was added to the arsenic-containing copper dust and roasted at low temperature.In a certain sulfur potential environment,S2 formed a decomposition effect on the phase of complex arsenic coexistence,S2 reacted easier with Zn O and Pb O than As2O3,inhibited the formation of Pb3(As O4)2 and Zn3(As O4)2,and Pb3(As O4)2 and Zn3(As O4)2 could be decomposed by S2 based on the strong reducibility of S2,and arsenic is released in the form of As2S3 and As2O3,which promoted the arsenic evaporation in arsenic-containing copper dust.The evaporation rate of arsenic is 94.54%,the content of arsenic is 0.35%,the evaporation rate of lead and zinc is only 0.89% and 0.77,and other valuable metals are not volatile under the conditions of roasting temperature of 400 0C,sulfur addition of 10% wt and roasting time of 100 min.The selective separation of arsenic from arsenic-containing copper dust is realized.Kinetics studyshows that the arsenic evaporation process is in accordance with the SCM model,controlled by internal diffusion within 60 min,and controlled by chemical reaction within 70-100 min.3.Selective removal of arsenic experiments by carbothermal reduction from arsenic-caontaining copperBased on the strong reduction of CO,Pb3(As O4)2 and Zn3(As O4)2 can be decomposed by CO,which promotes the evaporation of arsenic in arsenic-containing copper dust.The evaporation rate of arsenic is 97.02%,the content of arsenic in roasted slag is 0.31%,the evaporation rate of lead and zinc is only 2.01% and 1.55%,and other valuable metals are not volatile under the conditions of roasting temperature of 3500 C,coke powder addition of 30% wt and roasting time of 150 min.The selective separation of arsenic from arsenic-containing copper dust is realized.Kinetics study shows that the arsenic evaporation process is in accordance with the SCM model,controlled by internal diffusion within 60 min,controlled by hybrid controlling in 70-100 min and controlled by chemical reaction in 110-150 min.Selective removal of arsenic by carbothermal reduction,zinc and copper in the dust were changed into corresponding oxides,is conducive to the subsequent wet leaching.Carbothermal reduction selective removal of arsenic and high arsenic copper dust was selected in the study.4."Atmospheric pressure acid leaching-oxygen pressure acid leaching" to treat low indium content arsenic removed roasting slagBased on the fact that zinc and copper oxides are soluble in sulphuric acid and lead,tin oxides are not soluble in sulphuric acid,zinc and copper in arsenic-removed roasting slag are extracted by acid leaching under atmospheric pressure.The leaching rates of zinc and copper are 96.89%and 85.21%,respectively under the conditions of leaching temperature of 95 C,the concentration of sulfuric acid of 1.84 mol/L,the stirring speed of 350 r/min,the particle size is 80-90 μm,L/S of4:1,and leaching time of 90 min.Lead and tin are not leached and enriched in the leaching residue.The effective leaching of zinc and copper is realized.The leaching rate of indium is low,only 24.31%.Oxygen pressure acid leaching can obviously increase the leaching temperature and improve the thermodynamic and kinetic conditions of indium leaching.The low content of indium in the leaching residue can be extracted by oxygen pressure acid leaching.The leaching rate of indium is99.5%,tin and lead are left in the slag and a small amount of enrichment is achieved under the conditions of under the conditions of leaching temperature of 220 0C,particle size of 75-80 μm,sulfuric acid concentration of 1.53 mol/L,L/S of 10:1,stirring rate of 650 r/min,oxygen partial pressure 0.60 MPa in the kettle.Kinetics study shows that the leaching process of indium conforms to the SCM model,which is controlled by chemical reaction in the early stage,then controlled by hydride controlling,and diffusion controlling in the later stage.Chemical reaction control process is the main process affecting indium leaching.The order of reaction for initial sulfuric acid concentration,oxygen partial pressure and particle size is 0.95,0.82 and-1,respectively.The two-step process of "atmospheric pressure acid leaching-oxygen pressure acid leaching" realizes the high efficient separation and recovery of copper,zinc and indium from arsenic removal roasting slag.Combining with the actual production of the factory,a treating line has been set up to deal with3000 tons per year arsenic-containing copper dust,which provides a demonstration role for dealing with this kind of dust.The arsenic volatilization rate was 93-95% when the reduction temperature was 300-400 0C and the addition of coke powder was 30%.The metal arsenic was prepared by the reduction of arsenic in a closed tank at 700-7500 C for 12 h,and the purity of metal arsenic was 99.0-99.5%.Low indium arsenic removed roasting slag was treated by two-step process of “atmospheric pressure acid leaching-oxygen pressure acid leaching”.Copper in slag was recovered by sponge copper and indium by indium-rich material.The recovery rates of copper and indium were 98.5% and 90.3% respectively.The recovery rate of lead and tin is98.5% and 99%,respectively. |
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