| With the increasing scarce supply of non-ferrous metals resources,the research on green extraction of non-traditional zinc-containing resources is urgent,which can effectively alleviate the dependence on foreign resources,and provide protection for our economic sustainable development and national security.The discovered oxide-sulphide zinc ore accounts for million tons,which characterizes as complex compositions,high content of alkaline gangue,multi-metal associated and one metal existing in multiphase,thus can't be effectively processed by the existing technologies.Based on the comprehensive analysis of mineralogical characteristics of oxide-sulphide zinc ore,one synchronous leaching techniques of zinc ore is proposed in this thesis:oxidation roasting enhancement with field synergy,which is an improvement to the traditional oxidation roasting process.In this technique,the refractory ammonium leaching zinc-containing phases convert to easy-leaching phases by adding sodium-containing compounds and microwave-assisted heating,which is followed by introduction of ultrasonic-assisted technique and addition of complexing agent to strengthen the coordination leaching of zinc calcine.There also explores a new thechnique of low-temperature roasting with ammonium salts.The low-temperature roasting with ammonium salts technology is realized through addition of ammonium salt in the calcination process,in which zinc phases can directly transform to water leaching phases.The phase transformation process of oxide-sulphide zinc ore and the function mechanisms of different types of additives are studied by adopting the thermodynamics calculation of Factsage.The effects of complexing agents on species distribution in the leaching solution are analyzed by the coordination equilibrium software HYDRA/MEDUSA.Besides,the structures of complex are optimized by MS(material studio).Main results are as follows:(1)The composition minerals of oxide-sulphide zinc ore include sphalerite,smithsonite,galena,pyrite,quartz and calcite etc.,which can be deduced as comprising of complex phase compositions.(2)By comparing effects of Na2SO4,NaCO3 and Na2O2 on phase transformations of oxide-sulphide zinc ore,XRD,SEM-EDAX and XPS characteristics of zinc calcines,and the leaching rates of zinc,it can be concluded that,addition of sodium peroxide can promote the transformation of ZnS to ZnO,and inhibit the formation of Zn2SiO4 and ZnFe2O4,and is helpful for the effective recovery of zinc ore.(3)In the technique of oxidation roasting enhancement with field synergy,effect of sodium peroxide adding,microwave heating,ultrasonic strengthening and type of complexing agents on the recovery of zinc ore are studied.The results showed that,contents of ZnFe2O4 and ZnS gradually decreases with the addition of sodium peroxide,and microwave heating significantly increases the degree of oxidation of minerals and reduces energy consumption.In the ammonium leaching solutions,the complexing agent-triacetic acid(NTA)can form a more stable complex with Zn2+,what's more,ultrasonic technique can shorten leaching time.Under conditions of heating by microwave,mass doping level of Na2O2 being 20%,and leaching strengthened by ultrasonic wave,zinc leaching can reach 91.4%,with adding 0.5mol/L NTA.(4)The species distribution in the leaching solution are analyzed by HYDRA/MEDUSA.Results showed that Zn2+ mainly exists in the form of Zn(NH3)42+ tetrahedral coordination in Zn-NH3-NH4+-H2O system.Addition of complexing agent-citric acid can inhibits the generation of low coordination-Zn(NH3)32+,the promoting effect of NTA on zinc leaching is mainly due to the formation of Zn(NTA)24-.CH3COO-can form effective complex-Zn(CH3COO)3-with Zn2+ in the leaching solution.Zn(gly)3-has a greater stability to enhance the zinc leaching.The effective sequence of complexing agents are:nitrilotriacetic acid(NTA)>acetic acid(CH3COO-)>glycine(gly-)>citric acid(cit3).(5)In the low-temperature roasting with ammonium salts technique,effects of NH4H2PO4,NH4F,(NH4)2SO4,(NH4)2CO3 and NH4C1 on phase transformation of oxide-sulphide zinc ore are determined.It was found that NH4CI is a potential agent.In the heating process,refractory ore phase-ZnS and Zn2SiO4 can gradually react with NH4Cl to form a leachable phase-ZnCl2 On this basis,effect of doping amount of ammonium chloride is analyzed,and the optimized process is also studied.It can be found that high addition content of ammonium chloride is favourable.The optimum conditions for low-temperature roasting with ammonium salts is:NH4Cl adding mass ratio being 1.59,calcination temperature 320?,and the holding time 2.33h,and the transitions degree of zinc ore is 77.08%.(6)The transformation processes of oxide-sulphide zinc ore are calculated and simulated by adopting Equilib module of FactSage,whose correctness is verified by detection the XRD patterns,SEM-EDAX,FT-IR spectra and XPS spectra of zinc calcines.Both the two new thechniques of oxidation roasting enhancement with field synergy and low-temperature roasting with ammonium salts can strengthen the synchronous recovery of zinc-containing componets from oxide-sulphide zinc ore.The technique of oxidation roasting enhancement with field synergy takes a relatively short period of time to complete the phase transformation,while its cost is relatively high.Low-temperature roasting with ammonium salt demands a longer transformation time,but it can realize the closed circuit circulating by condensing and recovering the gas during roasting,which has a greater industrial prospects.The results of this thesis have some guiding significance for the establishment of new green and efficient extraction metallurgical process,improvement of theoretical system,and establishment of technical prototype for oxide-suiphide zinc ore. |
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