| Resources complementary of lead-zinc and multi metal comprehensive recovery are the main development trend for lead-zinc joint enterprises.The bottom-blowing oxidation smelting+side-blowing reduction smelting is a typical pyrometallurgical smelting process,which has the ability of comprehensive treatment and recovery from mixed lead concentrate containing complex raw materials in theory.However,when this system were used to handle with leaching lead-silver residues and smelting ash in a certain enterprise,some thorny problems,such as insufficient heat of oxidation smelting,instability and poor slag performance of reduction process were faced.Therefore,it is urgent to provide theoretical support for resource utilization of complex lead-containing materials and slag control through relevant theoretical and technological research.Considering the above requirements,this paper selected the Pb O-Fe O-Ca O-Si O2-Zn O systems to detect the root cause of instability and poor slag performance of reduction process based on analysis of the composition raw materials,process parameters,melting temperature and viscosity of slag.The phase and properties of slag in different reduction stages were measured and the dynamic law of reduction process for high lead slag was revealed.And according to the control and forming mechanism of smelting slag,process optimization suggestions in direct lead smelting handling lead-silver residues mixed lead sulfide concentrates were put forward,and verified in actual production.The main conclusions are as follows:（1）When adding mixed lead-silver slag 20 wt.%to 22 wt.%,the heat of oxidation smelting is seriously insufficient and incomplete oxidized.If H2O content in the smelting feeds lowered to 10 wt.%,the amount of lead-silver residues would reached 24 wt.%.If the H2O content in raw material reduced by 4 wt.%,the consumption of lead-silver residues can be increased by 1 wt.%to 1.5 wt.%,without adding extra heat.In reduction smelting stage,since the final slag containing Fe3O4phase,and Zn O content are more than20 wt.%,which lead to higher melting temperature and viscosity of slag than that of conventional smelting.（2）In the early stage of reduction,Pb are mainly exists in the form of Pb3Si O5,Pb O and Pb Zn Si O4.After reduced for about 30min,the Pb-containing phase disappear basically,and the Zn content in slag are improved,mainly present as Pb Zn Si O4,Ca2Zn Si2O7 and Zn Fe2O4.With the continurous reduction,the high melting temperature phases in slag increase,which worse the melting characteristics and fluidity of reducing slag.It can be seen from the the kinetics of reduction process that the early reduction process is controlled by the interface reaction,which conforms to the Erofeev equation;and after reduction 20 min,external diffusion condition become the dominanted factors;and then the reduction process conforms to the Mckwan equation after 30 min,which is controlled by the interface reaction.（3）Process optimized measures such as decreasing H2O content in the feeds,supplying extra heat to improve oxidation smelting temperature to 1050℃,the oxygen to material ratio can be dropped from 120 Nm3/t to about 110 Nm3/t,the feeding amount can be maintained to 24 t/h,the addition of lead silver residues reach up to 24 wt.%,with an ash rate decreased by 13.47%.In the reduction smelting,the optimum melting effect with Pb content of 1.8 wt.%in final residues,decresed ash rate by15.82%and reduced production cost by 10.63 wt.%can achieved.The controlling measures are adopted as follows:Fe O/Si O2 in the range of 1.2 to 1.6,Ca O/Si O2 from 0.4 to 0.6,Zn O content in slag less than 20 wt.%.To sum up,this study evaluated and optimized the direct lead smelting process handling mixed leaching lead-silver residues and smelting ash.The reduction mechanism of the reduction process is revealed,which provides the theoretical basis and practical data for the direct lead smelting process of resource utilization of lead-silver residues and other lead-containing wastes. |
