Experimental Research On The Separation And Beneficiation Of Iron And Tin From Lead Smelting Slag

The solid waste slag discharged from industrial pyrosmelting process is usually called lead smelting slag,which is rich in valuable metal elements and is a renewable resource with high recycling value.It will pollute the environment and waste metal resources if stored directly or disposed at will.Therefore,research on the separation,extraction and comprehensive recovery of valuable metals from smelting slag is carried out to make them harmless and resourceful.It not only practices the concept of conserving resources and protecting the environment,but also alleviates the pressure of metal resource shortage in China,which has both environmental protection significance and economic value.The research object of this paper is the waste residue discharged from the pyrosmelting of waste lead-acid batteries in a smelting plant in Ma’anshan city.From the perspective of mineral processing.On the basis of the study of mineralogical characteristics of smelting slag and the exploration of recovery process mechanism,the combined process of"reduction roasting-magnetic separation-pickling impurity removal-acid leaching enrichment-displacement"was adopted to recover the iron and tin elements in the slag.The corresponding products were obtained in the process and the high efficient separation and comprehensive recovery of iron and tin from smelting slag were realized.The analysis results of mineralogical characteristics of smelting slag showed that the main metals with recovery value in slag are iron and tin,with contents of 34.02%and 1.40%respectively.The main minerals are gangue minerals which mostly exist in vitreous melt,while magnetite,hematite and cassiterite are mostly wrapped in them.Iron and tin minerals can be separated and recovered only after they are released from them.Through a series of basic exploration experiments,it was proved that the reduction roasting-magnetic separation process with activated carbon as reducing agent is effective and feasible to separate iron-bearing minerals from smelting slag.Thermodynamic results showed that reduction roasting can transform most of the iron-bearing minerals in smelting slag into magnetic iron and cassiterite into simple tin in a specific temperature range while adding Ca O can make the complex oxides of iron decompose into simple iron at low temperature.This makes it possible to selectively separate iron and tin minerals from smelting slag.Based on the thermodynamic research,experimental research on reduction roasting-magnetic separation of smelting slag was carried out.The results showed that the optimal technological conditions are as follows:the grinding fineness of smelting slag was-0.075 mm 100%,the activated carbon dosage was 4 wt.%,the Na₂CO₃ dosage was 3 wt.%,the Ca O dosage was 10 wt.%,at 10℃/min with the furnace heating up to900 K and roasting for 40 min,then the reduction products were separated by a magnetic field intensity of 160 A/m.Under these conditions,magnetic separation concentrate with iron grade of 70.4%and recovery of 85.47%and magnetic separation tailings with tin grade of 2.18%and recovery of 91.10%were obtained.Then,the tin-containing tailings were acid leached in stages.First,the low concentration pickling experiment for impurity removal is carried out.The results showed that the optimal conditions are as follows:the concentration of hydrochloric acid was 15%,the reaction temperature was 55℃,the reaction time was 30 min,the liquid-solid ratio was 15:1.Under these conditions,the removal rates of Fe,Al and Ca impurities reached 83.00%,96.48%and 98.14%,respectively,and the recovery rate of tin reached 97.22%.Meanwhile,16.28%tin rich slag was obtained.Then the high concentration acid leaching experiment was carried out on tin-rich slag.The results showed that the optimal process conditions were as follows:hydrochloric acid dosage was 150 m L,the reaction temperature was 60℃,the reaction time was 40 min,the liquid-solid ratio was10:1.Under these conditions,the average tin leaching rate reached 83.55%.Finally,sponge tin with an average purity of 95.99%was obtained by replacing tin rich liquid with aluminum sheet,and the average replacement rate of tin reached 99.32%.