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During the processing of steel in steel mills, iron oxides will form on the surface of the metal. These oxides, known as mill scale, occur during continuous casting, reheating and hot rolling operations. Mill scale is a valuable metallurgical raw material since it contains 65-70% iron. JSW Steel Ltd is a 7 Mtpa integrated steel plant and generates 270 t of mill scale per day. Most of the materials of steel plant wastes are recycled through sinter making in most of the countries. Because of its physical, chemical and mineralogical properties, it can be used as a raw material in a process like sintering. The mill scale contains high amounts of Fe and low amounts of silica and alumina. Thus, recycling it through the sintering process helps in the saving of raw materials like iron ore and limestone. This paper presents preliminary findings of a study that investigates the potential for recycling steel mill scale in the sintering process. Experiments were conducted using the mill scale in sinter making from 0 to 70 kg/t of sinter. The total Fe and FeO contents of the sinter increased with the increase in mill scale addition. The sinter productivity decreased with the increase in mill scale addition due to a decrease in sinter bed permeability. The sinter strength and sinter mean size initially increased and reaches a maximum at mill scale addition of 40-50 kg/t of sinter and afterwards declines with the increase in mill scale addition. Sinter reduction degradation index and reducibility decreased with the increase in mill scale addition due to the increase in FeO content. Except sinter productivity, other desired sinter properties can be obtained with the use of 40-50 kg mill scale per tonne of sinter.

Coke breeze is the most common fuel used in sintering, and its usage depends on the alumina content and fineness of the sinter mix. The coke breeze consumption in the JSW Steel Limited sinter plant was high compared to many other sinter plants in the world, and as there was a local shortage, optimisation in the sinter plants was necessary. FeO is an indicator of the thermal state of the sintering process and is employed as a quality control tool at many plants. Laboratory pot sinters were made, and the variation in FeO was affected by varying the amount of coke breeze in the green mix from 55 to 85 kg t 21 of sinter. The produced sinters were evaluated with respect to productivity, strength (tumbler index), reduction degradation index (RDI), reducibility and microstructural phases in the FeO range between 6?2 and 14?8%. It was found that the sinter with FeO range of 8?60-9?88% showed higher productivity and higher strength with desired RDI of (27% and reducibility of .60%. Analysis of plant data has revealed that the sinter with FeO of 8?5-10?0% showed higher productivity, higher strength and lower RDI.

At JSW Steel Limited (JSWSL), pellets form the major part of the iron-bearing feed to corex and blast furnace. JSWSL produces low-basicity pellets ((CaO/SiO 2 ) -0.40 to 0.50). The quality of the pellet is affected by the raw material chemistry (gangue content), flux proportion and their subsequent heat treatment to produce the fired pellets. The raw material silica, limestone addition, i.e. basicity -CaO/SiO 2 of pellet decides the mode, temperature and the amount of melt formed. The properties of the pellets are, therefore, largely governed by the form and degree of bonding achieved between ore particles and also by the stability of these bonding phases during the reduction of iron oxides. In the present study, laboratory pelletisation experiments have been carried out to know the effects of silica and basicity on the microstructure and swelling behaviour of pellets during reduction. Phase analysis was carried out using image analyser, and chemical analysis of oxide and slag phases was carried out using SEM-EDS. From the laboratory studies, it was observed that the swelling index of the pellets decreased with an increase in silica content due to the decrease in porosity. The presence of higher silica in pellet hinders the reduction step of haematite to magnetite at lower temperatures. Pellets with basicity range 0 to 0.1 exhibited lower swelling index due to the formation of high melting point fayalite phase and also at this basicity range the structure is held together by the seam-like compounds between Fe 2 O 3 and SiO 2 primarily at high silica content. Higher swelling index was observed at the basicity range 0.3 to 0.7 due to the presence of low melting point calcium olivines (1115°C) between fayalite (FeSiO 4 ) and dicalcium silicate (Ca 2 SiO 4 ). Low melting point slag phase enhances the swelling index of the pellets. Swelling index of the pellets considerably dropped between the basicity range 0.9 to 1.1 due to the formation of calcium ferrite phases with a close pore structure.

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