Study On The Magnetic Separation Of Steel Slag And Tailings Used In Sintering Process

Steel slag produced during the steel making process is the main kind of solid wastes in metallurgical industry.Because of its huge mount of emissions and low ratio of utilization,most of the steel slags are still piling up and accumulated in the open air which cause serious waste of land and resources.By researching the particle size distribution,composition and mineralogical phase of three different steel slags?BOF slag,desulfurization slag,refining slag?,this paper suggests a magnetic separation-sintering process for the disposal of steel slags.The influence of SA ratio?mass ratio between slag and abrasive?and grinding time on the rate of iron recovery were tested.The economical efficiency and the quality of sinter produced by the process substituting separation tailings for ordinary sinter flux were analyzed.The main conclusions of this paper are as follows.?1?The refining slag and BOF slag exist as powder owing the small particle size while the desulfurization slag exists as lump.The desulfurization slag and BOF slag have higher total Fe content than refining slag?4.60%?.The main phase of steel slag are calcium ferrite,spinel,calcium silicate and RO,and it contains a large mount of alkaline oxides such as free-CaO,Ca?OH?₂.In the slag,Fe mainly exists in the form of solid solution RO oxide of Fe3O4 and FeO.?2?A grade magnetic separation process is developed through the determination of the size of steel slag and metal iron content evaluation: milled for the size range below 10 mm before separation;directly magnetic separation for over 10 mm slag and re-milling the magnetic separation tailings with the ball grinder for the theoretical maximum magnetic recovery rate.The magnetic recovery rate can reach 70% when the material ball ratio is less than 1:1.25?powder slag: BOF,refining slag?and more than 1:1.25?lump slag: desulfurization slag?respectively.?3?The result of sinter pot test shows that: keeping the general basicity about 2.0,with the tailings addition amount gradually increased,the sintering velocity,the grade level of sintering products and TotalFe decreased;while the firing rate and the yield increased at first and then decreased.Tailing added ratio of 5% is the maximum value for tailings addition ratio.?4?The shatter strength and drum strength,reduction degree increased when tailing added ratio increased from 0 to 5%;while decreased when it over 10%.The added ratio had little effect on the start softening temperature and melting temperature of the sintering products,but increased the complete melting temperature and free flowing temperature from 132? to 206?.