Description : | Bauxite is used as raw materials for production of alumina by Bayer process. It has some limitation with respect to mineralogical composition of the bauxite ores. As India bauxite contains more gibbsite, it is more suitable to this process. The bauxite should not contain more than 5% of reactive silica, total alumina content more than 42% and Fe should be less than 15% to make economical viability of the process. As the high grade ore availability becomes the problem, low grade ore is needed to beneficiate to meet the requisite specification of the alumina industry. The reactive silica presents mostly in ultrafine forms. If it is more, it increases the consumption of sodium hydroxide in leaching process and also give negative impact inthe down stream processes like settling, purification, crystallization, filtration and calcination. The attrition technique was used to scrub the ores in water by adding the suitable dispersing reagents using screw scrubber developed in CSIR-IMMT. The most of the reactive silica reports in the overflow of the screw scrubber. To enhance the yield of the product, the overflow is deslimed by hydrocyclone. It is possible to reduce the reactive silica to below 2% from 6-7% content in the ore. Vedanta and NALCO have the sponsored the project to carryout the studies. The process will be implemented by the stakeholders due to unavailability of high grade ore. Bayer process is used in India for production of the alumina. It has some limitation with respect to mineralogical composition of the bauxite ores. As India bauxite contains more gibbsite, it is more suitable to this process. The bauxite should not contain more than 5% of reactive silica, total alumina content more than 42% and Fe should be less than 15% to make economical viability of the process. As the high grade ore availability becomes the problem, low grade ore is needed to beneficiate to meet the requisite specification of the alumina industry. The reactive silica presents mostly in ultrafine forms. If it is more, it increases the consumption of sodium hydroxide in leaching process and also give negative impact I the down stream processes like settling, purification, crystallization, filtration and calcination. |
