| At present,the lead-bismuth-silver alloy materials produced in the lead and bismuth smelting process mainly consist of Pb-X binary alloys,Bi-X binary alloys,Pb-Ag-X ternary alloys,Bi-Ag-X ternary alloys and Pb-Bi-Ag-X multiple alloys.However,the predominant methods for treating these different alloy materials suffer from the disadvantages of the complicated process,excessive energy consumption,long production-cycle,poor performance in the recovery of metals.In addition,the release of harmful gases and emission large amounts of slags and smoke dust will lead to serious environmental pollution.To effectively improve the utilization rate of lead-bismuth-silver alloys,resource recovery,green renewable and comprehensive utilization of complex alloy materials obtained in lead and bismuth metallurgical processes have become an important demand of the non-ferrous metallurgy industry.In this thesis,based on the differences in physical properties of different phases in the lead-bismuth-silver alloys,simultaneously,combining with the theoretical analysis and equilibrium calculation of alloy phase diagrams and clarifying the feasibility criterion of the Stokes particle sedimentation process,an environmental-friendly method for comprehensive extraction of lead and bismuth resources by super-gravity technology is proposed.The following progresses were obtained:(1)For the Pb-X binary alloy materials,with an optimized separation condition T=533K,G=450,dpore=48 ?m and t=210 s,the mass fraction of Pb in the filtrated lead phase reached 85 wt%and migrated to the bottom of the sample along the super-gravity direction.On the contrary,almost all of the antimony-rich phase accumulated along the opposite direction and the mass fraction of Sb in the residue exceeded 91 wt%.And its purity can meet the production requirements of the subsequent lead electrolytic refining process and antimony refining,respectively.The migration behavior and separation characteristics of Pb and other elements in different Pb-X alloys(1#?5#)were analyzed,which provided theoretical guidance for the separation of other Pb-X alloy materials.(2)In addition to the Pb-X system,the Bi-X binary alloys obtained from the bismuth metallurgical process were also explored,and the migration mechanism and microstructural characteristics of the element Bi were investigated.The results showed that the purity of Bi-rich phases separated from the binary alloys of Bi-Zn,Bi-Cu,Bi-Pb,Bi-Ag and Bi-Sn reached 97.1%,99.7%,99.4%,96.3%and 97.1%,respectively;the mass proportions of the filtrated Bi-rich phases(?Bi-rich)were 85%,96%,87%,84%and 61%respectively,and the removal rate of impurity elements of Zn,Cu,Pb,Ag,Sn achieved 80%,98%,90%,75%and 88%,respectively.These results not only paved the way for subsequent separation of Bi-containing alloy materials but also provided a novel direction for green and efficient purification of crude bismuth melt.(3)The distribution behavior of each element in the Pb-Ag-X ternary alloys was analyzed It was found that 95.02wt%of Ag in the Pb-Ag-Sb alloy was enriched in the lower Pb matrix,which was beneficial to the subsequent recovery in the lead electrolytic refining process.And the Sb-rich phase with the content of 90.8wt%was presented in the upper part,which also met the production requirements of the antimony refining process.In addition,an effective and green method to recover silver,copper and lead from anode slime by super-gravity was investigated.Firstly,99.9%of selenium was removed after sulphating roasting,and then the valuable metals of lead,silver and copper with the metallic state were concentrated in the alloy phase by carbothermal reduction at 1173 K for 2 h.Simultaneously,under optimal conditions of G=600,T=1423 K and t=5 min,the filtrated lead-silver-copper alloy and residual phases were obtained.The yield of the Pb-Ag-Cu phase reached about 83%and the recovery efficiencies of lead,silver and copper exceeded 98%,96%and 89%,respectively.Especially,the residues could be recycled and returned to the pretreatment process.Finally,based on the phase diagram analysis and equilibrium calculation,the lead-silver and copper-silver alloys can be attained by super-gravity enrichment.(4)To further remove a small amount of silver in the filtered bismuth obtained from the preliminary separation of Bi-Ag alloy.an innovative physical method of centrifugal separation was proposed in this work.Combined with the theoretical analysis and equilibrium calculation of the Bi-Ag-Zn phase diagram,the removal mechanism of silver from the bismuth melt was investigated.After centrifugal separation with the theoretical amount of zinc addition at T=543 K,G=400 and t=5 min,the purity and yield of the bismuth-rich phase were up to 99.38wt%and 83.92%,respectively.And the removal rate of silver and zinc reached 99.84%and 91.16%.Besides,the silver mainly exists in the separated Ag-Bi and Ag-Zn phases,which could be returned to the silver converter for smelting or blast furnace for processed individually.(5)As to Pb-Bi-Ag-X multiple alloys,the extraction mechanism of valuable metals from Pb-Ag-Sb and Pb-Ag-Bi-Sb alloys was studied.It can be noted that the upper Sb-rich phase and the lower Pb-rich phase can be obtained at the same time after the separation of Sb-25%Pb-5%Ag ternary alloys,and the element Ag mainly presented in the upper sample.Similarly,the Sb-rich and Pb-Bi phases were found in the upper and lower parts respectively during the filtration process of the Sb-22%Pb-5%Ag-3%Bi quaternary alloy.(6)A two-step separation process with the typical Pb-Bi-Ag-X multiple alloy material of noble lead was proposed.Under the conditions of T=573 K,t=5 min and G=600,The filtrated Pb-Bi phase and residual crude Ag phase concentrated from the preliminary separation experiments mainly migrated to the lower and upper part of the sample respectively,and the primary enrichment rate of Ag(?Ag)reached 97.94%.In particular,only 0.89wt%of the Ag was detected in the Pb-Bi phase,which can further recover the Pb and Bi by super-gravity.In addition,By the conditions of T=843 K,t=5 min and G=600,the contents of Ag in the filtrated Ag-rich phase was 55.82wt%,and the secondary enrichment rate of Ag(yAg)achieved 92.04%.After the two-step filtration processes,the total enrichment rate of Ag(?Ag)up to 90.14%. |
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