No abstract

A low grade Limestone from ACC mines, Madukkarai, Coimbatore district, Tamil Nadu, India, was subjected to beneficiation by cationic reverse flotation process with the aim of producing cement grade and metallurgical grade concentrates. The low grade limestone analyzed 43% CaO, 76%TC, 18% SiO 2 , 1.3% MgO, 1.30% Fe 2 O 3 , 2.50% Al 2 O 3 , 0.33% alkalis and 36.00% LOI. It contained mainly calcite and quartz which were mutually intergrown with fair degree of liberation at 65 mesh size. Reverse cationic flotation was preferred to direct soap flotation, as practiced in beneficiation plant at Madukkarai. Inverse flotation studies were carried out to float siliceous impurities using cationic collectors varying collector type, collector dosage, mesh of grind and pulp density. Cement grade composite concentrate (non-float and slimes) assaying 9.51% AI, 90% Total carbonates at wt.% yield of 88 by a process comprising of grinding to MOG D80 400 microns, desliming/ screening over 400 mesh, rougher conditioning with 0.4kg/t SOKEM565C for 2minutes at 50%S, rougher flotation for 4 minutes, at pH 8 and 28% S. The float sand fraction assaying 80.30% AI, 18% total carbonates may be used as eco sand. On the contrary, premium metallurgical grade concentrate assaying 54.64% CaO, 0.6% SiO 2 , 0.7% MgO, 1.4% Fe 2 O 3 , 0.7% Al 2 O 3 , 41.0% LOI with weight% yield of 55.2, could be produced at 20% solids, MOG D 80 400 microns, and pH 8 with 1.0 kg /t of SOKEM 565 C. The evolved nil waste process is stable, selective, and easily adaptable in the existing anionic soap direct flotation plant at ACC Madukkarai cement works, yielding valuable products.

Lack of process characterization data of the ores based on the granulometry, texture, mineralogy, physical, chemical, properties, merits and limitations of process, market and local conditions may mislead the mineral processing entrepreneur. The proper implementation of process characterization and geotechnical map data will result in optimized sustainable utilization of resource by processing. A few case studies of process characterization of some Indian iron ores are dealt with. The tentative ascending order of process refractoriness of iron ores is massive hematite/magnetite \ marine black iron oxide sands \ laminated soft friable siliceous ore fines \ massive banded magnetite quartzite \ laminated soft friable clayey aluminous ore fines \ massive banded hematite quartzite/jasper \ massive clayey hydrated iron oxide ore \ manganese bearing iron ores massive \ Ti-V bearing magnetite magmatic ore \ ferruginous cherty quartzite. Based on diagnostic process characterization, the ores have been classified and generic process have been adopted for some Indian iron ores. Keywords Characterization Á Iron ores Á Beneficiation Abbreviations \ Less than [ Greater than WHIMS Wet high intensity magnetic separation, WLIMS Wet low intensity magnetic separation

The present study aims to investigate the use of mixed hematite and magnetite ores in iron ore pellet production. Pelletizing tests were carried out on the hematite and magnetite premixed pellet feed. Drop number and compressive strength tests for green and dry pellets; porosity, compressive strength and reducibility tests for fired pellets were carried out to determine the influence of mixing ratios of both iron oxides on those pellet properties. Experimental results showed that as the hematite content in the mix pellets is increased, the green drop number decreased from 6.5 to 5.2, the green compressive strength decreased from 1.51 to 1.28 kg/pellet and the dry compressive strength decreased from 2.50 to 1.60 kg/pellet. It was determined that fired compressive strength of mix pellets decreased from 380 to 230 kg/pellet when the hematite content in the mixed pellet is increased. The reducibility of mix pellets had almost the same trend and it was faster up to 40 min reduction time. The results showed that the use of hematite together with magnetite is possible to produce pellets with sufficiently good quality in terms of wet, dry and fired mechanical strengths. The porosity and reducibility values of mix pellets were also found to be adequate to use as feed for the blast furnace.