Experimental Study On Treatment Of Zinc-bearing Electric Arc Furnace Dust Based On Rotary Hearth Furnace Technology

The EAF dust produced by EAF steelmaking contains a lot of valuable elements such as Zn and Fe.Rotary hearth furnace treatment technology is a common treatment method for zinc containing dust at present.Its process is as follows:zinc containing dust and carbonaceous reducing agent are made into pellets and then sent to rotary hearth furnace for treatment.The low boiling point of Zinc is used to remove it,so as to achieve the purpose of separating Zn and Fe.The obtained metallized pellets can be used as raw materials for iron making or steel making.Firstly,the composition,phase,particle size and melting characteristics of EAF dust were studied by XRF,XRD and DTA.The results show that EAF dust has high zinc content,low iron content,fine particle size and high melting temperature.Zinc mainly exists in ZnFe₂O₄and Zn O,while iron mainly exists in ZnFe₂O₄and Fe₃O₄.Based on the thermodynamic analysis of the reduction process of ZnFe₂O₄,Zn O and iron oxide,the direct reduction and indirect reduction of three substances are studied.Theoretically,direct reduction at 1000?can reduce all three substances to single Zn and Fe.Secondly,the direct reduction experiment was carried out with ZnFe₂O₄as raw material,and its kinetic process was studied.The experimental results show that the reduction process of ZnFe₂O₄is divided into two stages:the first stage is mainly composed of iron oxide reduction,the interfacial chemical reaction is the limiting link of reduction.In the second stage,the reduction of Zn O is the main step,and internal diffusion is the limiting step.Finally,based on the technology of the rotary hearth furnace,the ball forming and roasting characteristics of the carbon containing electric furnace dust are tested.The effects of different binders,moisture content of mixture,C/O,coal type and pressing times on pellet strength were studied.The results show that C/O has a great influence on the strength of bituminous coal pellet,and coal type also has a certain influence on the strength of pellet.Increasing the moisture content of mixture will lead to the decrease of pellet strength,and adding bentonite can improve the strength of pellet.The effects of roasting time,roasting temperature and C/O ratio on the metallization rate,compressive strength and dezincification rate of pellets were studied.The optimum roasting conditions were obtained as follows:C/O=1.2,roasting temperature 1270?,roasting time 22min.The dezincification rate of pellets reached 99.9%,metallization rate reached 81.20%,and compressive strength reached 1113.5N.