Experimental Study On Roasting And Reducing Of Copper Slag To Produce Bead Iron

In China,the production of copper slag has increased in recent years,most of them are left untreated.Copper slag contains iron,copper,lead,zinc and other valuable elements,especially iron grade up to 40%,so it has high recovery value.Iron is mainly in the form of the silicate,which is tightly packed with the silicate and has a fine grain size,so it is difficult to separate and use traditional methods to realize the efficient recovery of iron.In order to recycle the iron resources of the copper slag,based on the conditions of the direct reduction process of rotary hearth furnace,pellets containing carbon are prepared by raw materials such as copper,reducing agent and limestone.Then bead iron and slag are prepared by pellets roasting and reducing.Through experiment,master the forming pellets and drying process,study the influence of technological parameters and material ratios on roasting effect,analyze the mechanism of melting and bead iron growing up,and master the mechanism of sulfur distribution.The pellets require a certain amount of intensity in a high temperature environment,so the influence of the variety and dosage of binder on the strength of pellets is studied in this paper,the results showed that the pellet strength is highest when the material contain 5%bentonite and 10%starch solution.In a certain range,drying temperature is higher and water evaporates faster,the drying time is shorter.In order to obtain better process parameters and material ratios,test examines process parameters and material ratios including the temperature and time,roasting atmosphere,cooling method,particle size of bedding material and C/O of pellets,alkalinity,fluxing agent type,adding method and dosage on the roasting effect,main conclusions as follow:(1)in terms of process parameters,roasting effect is better when more than 1400?,rate of iron recovery and total iron grade can reach more than 86%and 94%,so the choice of temperature is 1400?in view of the cost and energy consumption.The roasting effect is better than-35 when the size of the reducing agent is-100 and-200 mesh.Considering the difficulty of the broking process,the size of reducing agent chooses-100 mesh.When anthracite and semi-coke are used as reducing agents of pellet,the former roasting effect is better under the same conditions.The rate of iron recovery is gradually increased with the increasing of roasting time,but the rate of iron recovery remained unchanged after 40min.The bedding material can be used to prevent corrosion of slag and iron,then change the particle size,and find that the protection is the best when the particle size is 0.5?1mm.During roasting process,nitrogen protection can obtain better roasting effect.In contrast to the irregular shape of the water-cooled iron,the air-cooled bead iron stays elliptical and is easier to recycle.(2)In terms of material ratios,The iron recovery and total iron grade can reach 85%and 94%when the pellets are added with the 3%fluxing agent CaF2.Changing the dosage on the base of the internal adding CaF2,the roasting effect is the best when the dosage is 2%,with the highest rate of iron recovery 91.80%and total iron grade 95.22%.with the increasing of the C/O of pellet,the rate of iron recovery is the first to increase and decrease,and the rate of iron recovery is highest when C/O 1.54.With the increase of the alkalinity of the pellets,the rate of iron recovery was firstly increased and then decreased,reaching a maximum of 95.05%at 0.36.In order to obtain the high-quality bead iron with low sulfur content,this paper studies the distribution rules of sulfur in the process of reduction and melting of pellets.The results show that with the improvement of alkalinity,the sulfur of pellet is fixed mainly in slag,sulfur content of in bead iron and furnace gas is gradually reduced,while the sulfur content in slag showed a trend of increasing.this can not only get high-quality bead iron,can also reduce air pollution.In the condition of process parameters andmaterial ratios,we get the high-quality bead iron that has a 91.71%rate of iron recovery,total iron grade of 95.22%and sulfur content of less than 0.37%in the laboratory.