Study On Industrial Metabolism Characteristic And Pollution Reduction Potential Of Heavy Metals In Typical Zinc Hydrometallurgy System

Zinc hydrometallurgy is a typical industry with high heavy metal pollution,and cleaner production is urgent and important for zinc hydrometallurgy industry to implement proactive pollution prevention and control.Due to the limitation of lacking effective data and available methods to identify the cleaner production opportunities,the industrial metabolism characteristics,generation process and pollution reduction methods of heavy metals are still unclear.This should be the main reason for the slow increase in cleaner production level of zinc hydrometallurgy industry.This paper investigated the industrial metabolism process of seven heavy metals(Zn,Mn,Pb,Cd,Cu,Co,and Ag)at process network level(the wet process section within zinc hydrometallurgy system),process unit or production chain level(zinc electrolysis cellhouse),and production unit level(zinc electrolysis cell)of typical zinc hydrometallurgy system.The pollution reduction potential of the heavy metals was analyzed,and the plans of cleaner production implementation as well as the technical requirements for heavy metal pollution reduction of zinc hydrometallurgy system were discussed.In this paper,a two-phase multiple elements material flow model was designed to investigate the industrial metabolism of heavy metals in the wet section process network of zinc hydrometallurgy system.Results showed that zinc calcine is the main source of heavy metals imported into the zinc hydrometallurgy system.Acid leaching residue,jarosite residue,cobalt residue and Cu-Cd residue are the four main outputs of the heavy metals of the system.The distribution pattern of the heavy metals in the network played an important role in affecting the pollution generation of the heavy metals,and the estimated contribution of the distribution patterns is in the order of Cd(55.75%)> Cu(45.88%)> Co(43.64%)> Ag(27.53%)> Zn,Mn and Pb(0%).The allocating behavior in condense process unit after neutral leaching and condense process units after neutralization played a key role in affecting the final recovery rates of related heavy metals.Two novel indicators(S and ?S)were devised to quantify the hazardous potential and the resource potential of the material flows,respectively,for CP opportunities identification and CP strategies selection.The bathing process unit was identified to be the key process,which is the main reason of aggravating the pollution level(indicator S increased by 28.8)and resource dissipation(indicator ?S increased by 2902.3),and should be substituted by more advanced technologies(higher efficiency and less water consumption).The expected recovery process in the upstream of process chain was also indicated based on the evaluation results.A mathematic model based on the reaction mechanisms was built to investigate the current efficiency,the intensity of energy consumption,and the generation intensity of pollutions.It was found that changing or optimizing the anodic reaction might have significant potential to reduce the energy consumption,anode mud generation,and acid mist generation,since that the anodic electric potential contributes 62% of energy consumption,anodic oxygen evolution contributes 87% of acid mist,and manganese oxidation contributes 100% of anode mud generation.The increased energy consumption should be mainly responsible for hindering the pollution generation intensity reducing in the parameter optimization.In summary,the pollution generation mechanisms of heavy metals could be classified into three kinds,including unsatisfactory distribution,resource dissipation,and technology limitation.The unsatisfactory distribution is the main reason for the pollution generation of Cu,Cd,Co,and Ag in zinc hydrometallurgy system(theoretical reduction ratios: 27-56%);Resource dissipation is the main pollution generation mechanism for Zn pollution generation(theoretical reduction ratio: 100%);The technology limitation is the main reason for Mn and Pb pollution generation(theoretical reduction ratios: 13-49%).In addition,to better achieve a green and sustainable development of zinc hydrometallurgy,at present,it is important to promote cleaner production in both the upstream(raw material supply)and downstream(resource recovery)of zinc hydrometallurgy process,and optimize them as an integrated system.