Research On The Selective Leaching Of Lead, Silver And Zinc From Iron And Steel Smelting Dust

Both sintering dust and blast furnace dust are the dust and sludge produced in the iron and steel smelting process,which are the by-products inevitably produced in the iron and steel smelting process.Because they contain much more iron and carbon,the traditional treatment method is returning the dust and sludge directly to the sintering ingredients in order to recycle of iron and carbon resources and reduce pollutant emissions.However,the dust and sludge containing heavy metals such as lead and zinc are directly returned to the sintering batch for recycling,resulting in the cyclic enrichment of these nonferrous metals in the steel smelting process,affecting the blast furnaces'forward and life.Therefore,it is necessary to find a feasible way to selectively separate harmful metal elements from the iron and steel smelting dust,so that the valuable metal elements can be recovered to the greatest extent while reducing the harm of the impurity metal elements in the iron and steel smelting dust.This article starts from the selective separation and extraction of zinc,lead and other elements that are harmful to blast furnace ironmaking in dust and sludge,and simultaneously enriches iron and carbon and other useful elements for iron and steel smelting.The acid chloride salt system is used to treat the sintering dust and blast furnace dust separately to achieve the selective separation of nonferrous metal elements such as lead,silver and zinc in the iron and steel smelting dust and the efficient enrichment of iron,carbon and other beneficial elements for iron and steel smelting.The main research contents and related results of this topic are as follows:?1?According to the characteristics of high lead and silver content in the sintering head ash,the HCl-NH₄Cl leaching system was used to selectively separate the lead and silver in the sintering dust.The study found that the increase of acidity,leaching temperature,chloride ion concentration,liquid-solid ratio and leaching time will promote the leaching of lead and silver in the dust,which is consistent with the theoretical analysis results of the species distribution diagram of the lead and silver complexes and the potential p H diagram.The optimized leaching conditions were as follows:the p H of the leaching solution was 3.0,the leaching temperature was 80?,the chloride ion concentration was 6 mol/L,the liquid-solid ratio was 10:1 m L/g,the stirring speed was 400r/min,and the reaction time was 2h.Under this optimized condition,the leaching rates of lead and silver in the sintering dust are both greater than95%,while the leaching rates of iron is 1.3%;the content of lead in the slag is reduced from 22.4%in the raw material to leaching 1.82%in the slag,the silver content is reduced from 310.4g/t in the raw material to 78.2g/t in the leaching slag.The iron content is enriched from 28.5%in the raw material to 52.6%in the leaching slag and the content of carbon is enriched from 2.7%in the raw material to 5.0%in the leaching slag.The leaching slag after iron-carbon enrichment can be used as the raw material for sintering process.According to the phase analysis,the flocculated KPb₂Cl₅ on the surface of the particles in the raw material disappeared,exposing the particles with smooth and dense surface after leaching,the main components are iron oxide,carbon and aluminosilicate.?2?In view of the characteristics of high zinc content in blast furnace dust,the HCl-Na Cl leaching system was used to selectively separate zinc from blast furnace dust.The study found that the increase of acidity as well as the leaching temperature,sodium chloride concentration and liquid-solid ratio will promote the leaching of zinc in the blast furnace dust,which is consistent with the theoretical analysis results of the zinc chloride complex species distribution diagram and potential p H diagram.The optimized leaching conditions were p H value of leaching solution 4.0,leaching temperature 70?,sodium chloride concentration 3 mol/L,liquid-solid ratio 4:1m L/g,stirring speed 400r/min and reaction time 2h.Under this optimized process condition,the leaching ratio of zinc reaches 93.1%and the leaching ratio of iron is7.4%;the zinc content is reduced from 9.54%in the raw material to 0.8%in the leaching slag.The iron content is rich from 35.9%in the raw material collected into43.0%of the leaching slag and the carbon content is enriched from 13.5%in the raw material to 17.3%in the leaching slag.The leaching slag after the enrichment of iron and carbon can be used as a raw material for sintering process.The phase analysis results of the leaching slag show that after leaching,the zinc phases such as zinc sulfate and zinc oxide embedded in the particles are leached.The leaching slag is mainly smooth and dense and uneven grains,and its main The components are oxides of carbon and iron.The unleached zinc in the leaching slag mainly exists in the form of zinc ferrite.?3?After the sintering dust and blast furnace dust are separately leached by chloride,non-ferrous metal elements such as lead,silver and zinc are selectively separated and leached into the leaching solution,which provides favorable conditions for the subsequent recovery of these valuable metals.Elements such as iron and carbon in the dust that are beneficial to ironmaking are not leached,and remain in the leaching slag and are enriched,which creates favorable conditions for the return of sintering process and the comprehensive recovery of valuable elements such as iron and carbon.Coordination extraction and separation technology can better realize the comprehensive recovery of various valuable elements and components in steel dust..