Research On Desulphurization And Digestion Performance Of High-sulfur Bauxite

Ninety percent of the bauxite in China is diaspore with high content of aluminum and low content of iron. Almost half of the high aluminum, low iron diaspore ore can not be applied in industry for containing high-sulfur. Among the high-sulfur diaspore, high-grade ore accounted for57.2%, medium and low grade ore accounted for42.8%. If processing of desulfurization from the high-sulfur diaspore, such a large proportion of high-grade ore can be applied in industry, so researching the economic desulfurization method has great potential industrial significance.Based on lots of datum about desulfurization home and abroad, the paper considered that the flotation method is the effective method of desulfurization. It is necessary that the sulfur collectors, flotation process parameters, flotation kinetics and flotation process for high-sulfur diaspore should be further studied.Firstly, the phase composition of high-sulfur bauxite of Chongqing China was studied. The results show that:the diaspore is the main phase of high-sulfur bauxite. Furthermore, this also contains a certain amount of goethite, kaolinite and pyrite. The element of sulfur is mainly in the form of FeS2. Sulfur content is2.08%. Pyrite embedded fabric diaspore uneven.Secondly, the sulfur capture abilities of sodium dodecyl sulfonate, ethyl xanthate, ethyl-thio carbamate, butyl xanthate and isobutyl xanthate were studied by one-stage cleaning process. Furthermore, the influences of these collectors by process parameters were studied too. The results show that:the collective and selective abilities of sodium dodecyl sulfonate are very poor. So it can not be used as sulfur collector in high-sulfur bauxite desulfurization. Although the ethyl xanthate and ethyl thio carbamate can be used as capture agents in the desulphurization experiments of high-sulfur bauxite, the selectivity and capture ability are not as good as butyl xanthate and iso-butyl xanthate. Butyl xanthate has stronger capture ability than isobutyl xanthate, but the selectivity is lower than isobutyl xanthate.Thirdly, The optimum flotation process parameters of ethyl thio carbamate were:the dose0.5kg·t-1, pH=4, ore size≦0.09mm, liquid/solid ratio10; The optimum flotation process parameters of ethyl xanthate:dose0.4kg·t-1, pH=8, ore size no more than0.09mm, L/S=9:1; The flotation experiments by the circle test of one-stage roughing, two-stage scavenging and two-stage cleaning flotation under these flotation process parameters were studied. The results as flows:the sulfur containt was lower than0.55%, the aluminium recovery was98%.Fourthly, Butyl xanthate and iso-butyl xanthate have the same optimum flotation process parameters:dose0.16kg·t-1, pH=10, ore size no more than0.09mm, L/S=10. The flotation time of these collectors are15min. The flotation experiments by the circle test of one-stage roughing and one-stage cleaning flotation under these flotation process parameters were studied. The results as follows:the sulfur containt of bauxite was lower than0.6%and the aluminium recovery was98%. The sulfur containt was more than20%of the sulfur concentrate.Fifthly, the results of flotation kinetics showed that:the flotation dynamic equation of butyl xanthate was R=R∞o(1-e-kt), k=2.934×10-3. The flotation dynamic equation of ethyl xanthate was R=16.15t1.63/(1+0.21t1.63), while the flotation dynamic equation of isobutyl xanthate was R=52.87t0.83/(1+0.59t0.83), R means desulfurization,t means flotation time.Sixthly, the flotation mechanism was studied, too. The double-poly reaction was occurred in the flotation process whether xanthate or thio carbamate agents was the flotation collectors. The double-poly could increase the hydrophobic properties of mineral surface which adsorbed the collectors. CuSO4used as the sulfide activator in the flotation test. The reason of Cu2+,s activation is that it could promote dimmer formation of flotation collectors.Seventhly, the digestion performance and settling performance of raw ore and flotation ore were studied. The result showed that the optimum digestion performance conditions were similar. The digestion conditions were temperature220℃, lime addition15%, time60minutes, ANk240g·L-1and molecular ratio1.5. The digestion rates of the flotation ores were95.03%which was lower than that of raw ores’95.35%. But both have reached the requirements of industrial production of alumina. In the digestion process, the flotation ore greatly improved the phenomenon of dark red mud. The settling performance studied showed that the flotation ore and raw ore had the same performance.