Influence of raw material particle size on quality of pellets

Abstract

Pellet plant (4?2 MPta capacity) of JSW Steel Ltd imports iron ore fines from different mines to produce pellets for its Corex and Blast Furnace plants. The pelletisation process involves drying the ore fines to reduce the moisture content to less than 1%, grinding in open circuit ball mills to get required fineness. To produce good quality of pellets certain additives are important and limestone is employed for modifying the pellet basicity. Iron ore fines of 210 mm size and limestone are ground together in a ball mill to get sufficient fineness for the balling process. However, as limestone is harder than iron ore fines the z100 mesh size limestone particles is higher than required and not all the limestone is fully consumed in the reaction for melt formation. Microstructural studies were conducted under a Leica DMRX polarized microscope at different level fineness (2325# 2 56, 58 and 60%) to investigate its effect on the pellet quality. The cold crushing strength of the pellet improved from 203 to 220 kg p 21 with increase in fineness. With increase in percentage of 2325# particle size in the ground product RDI of the pellet decreased from 13?8 to 11?9% with increased melt formation from 5 to 9%. With increase in fineness 2325# from 56 to 60% the 150 to 500 mm size pores decreased from 51?8 to 13?6%.

Development on Iron Ore Pelletization Using Calcined Lime and MgO Combined Flux Replacing Limestone and Bentonite

“…This may be due to the higher amount of closed pores formation during induration in high basicity region. Umadevi et al 18) reported that CaCO 3 in limestone particle in pellet decomposed to CaO and CO 2 gas. Then the produced porous and cracked CaO is dissolved by forming Calcium ferrite, SCA or SFCA phases leaving a pore on that place.…”

“…The swelling index is slightly higher in 0.8 basicity than 0.25 basicity. One more problem with high basicity is the crack formation Umadevi et al 18) has found in high basicity pellets that the conversion of glass phase to the crystallized wllastonite phase happens during reduction at around 800-900°C and during conversion, cracks forms over the entire pellet. This may also be the reason of comparatively higher swelling index in 0.8 basicity pellets (i.e high CaO content).…”

“…Earlier investigators [4][5][6][7][8][9][10][11] have studied on the use of hydroxide lime in iron ore pellets and found some encouraging results. De Sauja 4) has shown the advantages of using hydrated lime in pelletzation and reported to achieve average 367 kg cold crushing strength (CCS), 18.5% swelling index and 69% reducibility index of indurated pellets. Very high green compressive strength (4 kg/pellet) drop numbers (10.4) and dry compressive strength has been reported by Eisele and Kawatra 3) when hydroxide lime is used.…”

Effect of Blaine Fineness on the Quality of Hematite Iron Ore Pellets for Blast Furnace

“…Although, investigators (Onoda et al 1980;Dwarapudi et al 2011;Umadevi et al 2011) have studied on quality improvement of hematite pellet by addition of fluxes or carbon, a study on pellet properties with the fineness of hematite ore fines is also imperative. The effect of iron ore fine size on pellet properties has recently been studied by several investigators (Umadevi et al 2008;Pal et al 2009;Dwarapudi et al 2010;Dwarapudi et al 2011). They, however, studied the effect of ore size as per its sieve analysis in terms of mesh size or diameter in ''mm.''…”

Indication of the Measurement of Surface Area on Iron Ore Granulation

“…Therefore, The characterization of the particle size and the surface features of iron ores is of vital importance for the studies of mineral processing. [2][3][4][5][6][7] The specific surface area of iron ore particles can be measured by nitrogen adsorption, laser diffraction, and mathematical models based on the size distribution. 8) However, what is the difference among these methods and what is the indication of the results were less discussed on the iron ore granulation, which is the right topic of the present study.…”