BENEFICIATION PROCESS DESCRIPTION
Low grade iron ore fines (<57% Fe) are subjected to Beneficiation process to produce iron ore concentrates with higher iron content (>63% Fe). The iron ore fines of -10mm size from the stockpile is conveyed to Beneficiation plant for screening through series of conveyors.
The oversize material (+1mm) from the screening process is fed to Rod Mill (wet type primary grinding unit) to generate a product of (–)800 microns size. The under size product collected from the screening process and primary grinding product is mixed and further processed in the gravity separation process to enrich iron ore grade. Gravity separation process separates the feed into three products viz. coarse (+800 microns), Fines (-800 to +150 microns) and Slimes (-150 microns). Course fraction is subjected to Ball Mill (wet type secondary grinding unit) for size reduction to -150 microns.
Fines fraction is subjected to magnetic separation process to produce magnetic concentrate and non-magnetic tailings. Slimes from the gravity separation process is thickened in intermediate thickener and fed to magnetic separation unit. Magnetic concentrate from magnetic separation process is fed for secondary grinding to achieve the required size for making pellet. The secondary grinding product is subjected to classification and thickening process to produce iron ore concentrate.
The tailings from the magnetic separation process are pumped to a designated place for disposal. The reclaimed water from tailings & thickening process are recycled back to process. The makeup water is added, for the loss of water in concentrate and tailings.
The beneficiated concentrate is sent to concentrate Thickener, where the slurry composition is adjusted by coalescence and transferred to Slurry tanks for further pumping to Pellet Plant.
PELLETISATION PROCESS DESCRIPTION
The beneficiated concentrate slurry is received at Pellet plant and stored in slurry tanks. The concentrate slurry is fed to the filtration process where it is dewatered by Pressure filters. The product comes out is called filter cake (moisture around 10-11%) which is stored in bin for further process of mixing. The filtrate water, so generated, is sent to process water reservoirs through thickener for storage and internal plant consumption.
Pellet plant is facilitated with Additives grinding unit as the process of pelletization requires binder and additives. Bentonite is used as a binder for proper balling of the filter cake particles into spherical shaped balls with certain compression strength. The bentonite is stored and ground in a Vertical grinding mill by dry grinding process to desired fineness. The powdered Bentonite is stored for further mixing process. Lime stone is used as a fluxing agent and to get strength to the pellet by heat hardening. Coke dust is used as a compensatory fuel and to improve physical strength of the pellets by uniform firing of each pellet up to the core. Both Lime stone and coke are ground in a definite lime to coke ratio in a ball mill by Dry grinding process. The product is lime + coke powder mix of desired fineness is stored for subsequent mixing process.
In Mixing & Baling unit; Bentonite, lime & coke mix are added to the concentrate filter cake at a definite rate of addition and is thoroughly mixed in a Vertical mixer. The so mixed concentrate is fed to rotating inclined disc pelletizers. Fine ore particles are agglomerated into spherical shaped balls due to the rotating action of the disc. The so formed balls are called green balls which are further screened and fed to an indurating furnace.
In Induration unit, the green balls are fed to the induration machine which forms endless chain of pallets, are slowly brought through different zones of the induration furnace by the horizontal movement of the pallets. These green balls are subjected to drying, preheating, firing, after-firing & cooling in the indurating furnace where pellets are in directly heated in a controlled manner by circulation of hot gases with the help of Process fans. Heat energy is supplied by oil fired burners. LSHS/FO is used as fuel and source of heat energy which is stored and pumped to burners. Critical parts of the induration furnace are cooled by water circulation.
The fired and cooled pellets with good physical strength is conveyed and stored in pellet stock pile. The pellets are dispatched to the customers as a feed to blast furnace and /or DRI production.