Research On The Behavior Of Zn、Fe、S During Baking Of Jarosite

In this paper, the thermal decomposition and the reduction process of jarosite are analyzed theoretically. the XRD and XRF examination and the quantitative chemical analysis of key elements of jarosite sample from bayannaoer zijin non-ferrous metals company were also made. From these analysis we know the composition, content and existential state of key elements in the jarosite. Then reductive baking of the jarosite sample by petroleum coke and powder coal-magnetic separation tests have been accomplishment. Following results can be given under the scope of this research work.When reductively baking jarosite with petroleum coke, no reductive reactions happen below820℃. A part of jarosite has been reduced during baking when temperature exceeds970℃. When temperature reaches1020℃, ratio of Fe2+coming from reduction exceeds theoretical proportion of Fe3O4compound(1/3). This means that a part of Fe3O4has been reduced to FeO or iron. Addition of magnesium hydrogen carbonate and sodium carbonate has only a little effect on the reduction of jarosite. On the other hand, the additives will fix a part of S and make it difficult to escape from calcine. When temperature were controlled between700℃and1000℃, Calcified baking help to produce magnetic separation concentrate. And the amount of concentrate gets more than the tailing at10O0℃. The concentrate amount is lower than that without calcified at1000℃. But calcified baking help to Restrain the sulfur dioxide to escape.When reductively baking jarosite with powder coal, jarosite gets a good reduction result at900℃. Basic sulfate other sulfate will get reduced above900℃, there is basic sulfide formed and causes sintering. The optimum conditions of baking jarosite by powder coal are as following:baking temperature at900℃, powder coal addition is45g/kg, residence time is75minutes. The content of S and Fe in the calcine under this condition are3.07%and55.94%respectively. And pH value of leaching solution of the calcine under this condition is5.19. Test results of baking-magnetic separation show that under this condition Fe content in the concentrates are between58.72～58.99%when magnetic field intensity were controlled in the range of30mT-150mT. Thereis a part of Fe dissolved during magnetic separation. The content of Zn in concentrate is higher than that in tailing by about1%. S content in concentrate is between2.5and3%, and majority of S exists together with magnetic product.Baking jarosite with powder coal followed by magnetic separation can achieve proper enrichment of Fe, and Fe content are close to meet the demand of iron-making. But a large part of Zn and majority of S go with magnetic part of the calcine. This make it difficult to separate them from Fe.