Further Pilot Plant beneficiation studies on Limestone sample from T.I.S.C.O.

Abstract

A 700 tons sample of low grade limestone, assaying 45.9% CaO and 7.1% SiO2 was received from Messrs Tat Iron & Steel Works, Jamshedpur, for upgrading and agglomeration studies in continuation of National Metallurgical Laboratory ‘s earlier investigation Report (vide NML I.R.No.235/62) with particular stress on techno-economic studies of beneficiation of limestone for use as steel-making flux. The flow sheet broadly comprises of grinding the ore to 80%-200 mesh and floating off limestone using sodium create as collector and sodium silicate as depressant for siliceous gangue. The concentrate thus obtained was agglomeration using molasses as binder to yield pellets of optimum strength and size. The test results indicated that by this operation, about 75% of the entire siliceous gangue could be rejected as tailing, producing a concentrate constituting 88% by weight and assaying 50.3% CaO, and 2.0% SiO2 with a recovery of 94-95% CaO. In continuous plant operations, one should be prepared to expect a concentrate containing 2% SiO2 with a maximum variation of about +- 0.5 % in the day-to-day results. The test results also indicated that the best separation of insolubles should be achieved from a pulp containing not over 22% solids, 80% of which pass through 200 mesh. Small additions as low as 0.0227 Kg/tonne (0.05 lb/tonne) of pine oil were found to drastically cut down the collector consumption from 0.73 Kg/tonne (1.6lb) to 0.41 Kg/tonne (0.9 lb/tonne) for upgrading the limestone. The agglomeration studies revealed that the moisture content of the concentrates mix had a marked influence on the size, shape and quality of pellets produced. Drop tests with green pellets and crushing load tests on hardened pellets indicated that strong pellets assaying 47.84 % Cao and 1.91% SiO2 could be obtained when the final concentrate containing not over 8.5% moisture was mixed with 6% molasses.