Mill scale is an iron oxide waste generated during steelmaking, casting and rolling. Total generation of mill scale at JSWSL is around 150 t/day and contains 60-70%FeO and 30-35%Fe 2 O 3 . To recover the iron, the mill scale must be smelted in a blast furnace or other reduction furnace; however, it is usually too fine to use without previous agglomeration such as via pellet or sinter mix. JSWSL operates a 4?2 Mtpa pellet plant to produce pellets for Corex and BF ironmaking units. The aim of this study is to determine the effect of mill scale on pellet properties. Detailed laboratory basket trials were conducted using up to 40% of mill scale in the pellet mix. The addition of mill scale up to 10% is considered to provide the optimum balance of chemical, physical and metallurgical properties of the pellet.
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%.
Pellet quality plays a significant role in the performance of the Corex process, which is, in turn, affected by the C content of the green pellets. Experiments have been conducted to study the effect of varying the C content (%) in the pellet mix on pellet quality, properties and microstructure by varying the quantity of Corex sludge. For further understanding of the phenomenon, microstructural studies have been carried out. It was observed that FeO increased with increasing C content to 1?45% in the pellet mix, thereby decreasing the cold crushing strength (CCS) of pellets to 186 kg/ pellet and increasing the reduction degradation index (RDI) (26?3 mm) of pellets to 16?3%. Superior pellet properties were obtained with the carbon in the range of 1?15-1?2% in the pellet mix.
Steel Melting Shop-I, Rourkela Steel Plant, Rourkela, produces 0.5 MT of various special steels through BOF-VAR/VOR-LF-CC route. One of the most serious problems in BOF operations was lance skulling, hood jamming, and build-up of metal in the mouth and cone of the furnace due to spitting and slopping. As spitting occurring during blowing increases, these particles of metal are deposited inside the mouth and cone and affect badly BOF productivity. In the present work, control of spitting has been established by addition of sinter during the period of spitting. It also helped to improve the slag formation and fluidity of slag through increase of FeO content during peak decarburisation period.
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