Research On Recovering Ferroalloy And Zinc Oxide By Direct Reduction Of Electric Arc Furnace Dust (EAFD)

Electric arc furnace dust(EAFD)has attracted more and more attention as a kind of metallurgical solid waste with huge production.How to reduce its harm to the environment and efficiently recover valuable metals such as zinc,iron,chromium,and manganese from its complex components to realize the comprehensive utilization of EAFD is the aim of various EAFD treatment processes.Chemical analysis,XRF analysis,XRD analysis,and TGA analysis were used to detect the experimental raw materials.The redox reaction mechanism was discussed by using HSC chemistry 6.0 software based on the laws of thermodynamics;Factage 7.2 was used to simulate the theoretical slag composition,viscosity and melting point.According to the mechanical and chemical test results,the compressive strength,metallization rate and element removal rate of metallized pellets were determined.In addition,the migration law of elements in Fe-Cr-Mn alloy was also studied.The results show that the total direct reduction of iron oxide began at 925.5 K,and enthalpy change is positive.Zinc vapor removed at above 1278 K,which is finally oxidized by oxygen.When the alkalinity(R)=1.2,the melting point of the slag is between 1400℃ and 1450℃,and the main phase is Ca3MgSi2O8;When R=1.1,0.8,the slag begins to enter the liquid phase area at 1400,1350℃;When R<1.1,the main phase of the slag is melilite.The limiting link of EAFD-carbon thermal reduction is gas diffusion process,and the reaction activation energy is 60.400 kJ·mol-1,60.932 kJ·mol-1;Based on the assumption of first-order reaction kinetics,the apparent kinetic equation is:In[1-f(t)]=-0.19e一50.068/RTt;Based on the kinetic assumptions of interfacial and local reaction,it is:1-[1-f(t)]1/3=0.013e-30.417/RTt.The optimal parameters are R=0.8,C/O=1.2,T=1250℃,holding for 10 min and heating for 30 min.The metallization rate is 90.03%,the strength of metallized pellets is 17.9 MPa,the removal rate of Zn is 97.42%,that of Pb,Na and K are 97.35%,37.11%and 39.25%respectively.The content of Mn decreased with the increase of temperature;the maximum content of Mn is 1.03 wt.%at 1150℃.The maximum content of Cr is 2.76 wt.%at 1200℃.Cr and Mn decreased with the increase of alkalinity.The maximum content of Cr and Mn are 2.90 wt.%and 1.36 wt.%,respectively.The test shows that the zinc enriched powder is mainly ZnO,and there are impurities of PbCl2,PbO,NaCl,KCl and Zn.Micro morphology analysis shows that the ZnO in the product is mainly needle like,and there is a small amount of comb like and emission like ZnO crystal.