Reduction of Silica content in a Limestone Sample (No.4) from Purnapani Quarries, Orissa (for Hindustan Steel Ltd., Rourkela)

Abstract

A sample of low grade limestone (Sample No.4) from Purnapani Quarries of Hindustan Steel Ltd., Rourkela, assaying 40.95% CaO,35.0% CO2,5.4% MgO, 14.4% SiO2, 3.08% Al2O3,1.1 % Fe2O3 and 0.2% S was studied for be profitably utilized as a flux in the iron and steel industry. Calcite and dolomite constituted the carbonate minerals and the gangue consisted primarily of quartz followed by chlorite, phlogopite, biotite, muscovite, feldspars and small amounts of pyrrhotite, chalcopyrite and pyrite. The gangue was reported to be fairly well liberated at about 150 mesh. Flotation with an optimum feed containing 73.13-200 mesh and using 0.75 1b/ton of oleic acid emulsion as collector and 1.01b/ton of sodium silicate as depressant for siliceous gangue yielded a concentrate assaying 48.9% CaO, 4.76% MgO,40.9% CO2,2.53%.This concentrated product which is in the form of fines is considered chemically suitable for use as a flux in the iron and steel industry. However, its successful utilisation depends on the development of proper agglomeration processes such as briquetting, pelletising and sintering techniques, studies on these aspects are being under in the National Metallurgical Laboratory.