Utilisation of Hot Metal Desulphurised Slag in Sinter Making at JSW Steel Limited.

Abstract

In BOF, hot metal is converted into steel. Sulphur can be reduced in blast furnace / Corex, but it will be having detrimental effect on plant economy. The generation of steel melting slag are 200-220 kg/t of steel produced. Disposal of large quantities of slag becomes a big environmental concern. Slag from steel making has free CaO, which can replace some amount of flux in Iron Making burden. But due to high Phosphorous content in LD slag, it is proposed to use the pre treatment slag which has same CaO content and less Phosphorous. HMDS slag consists of 2-2.5 % sulphur and same slag used in lab scale to see the impact on sinter quality. Analysis of sinter shown decrease in sulphur up to 0.010%. Hence its is desired to use HMDS slag as substituent to LD Slag in iron ore sinter making which is being used since inception and usage is restricted due to phosphorous content . Thus, recycling of HMDS slag through the sintering process recovers lime, iron and magnesia and thereby saving of flux material and iron ore in future. Detailed investigation was carried out through lab scale studies for estimating the maximum permissible limits of usage of HMDS slag in sinter making and to know the influence of addition on sinter productivity and properties. Statistical Design of Experiments was conducted using the HMDS slag in sinter making from 0 to 60 kg/t of sinter. From the test results it was found that 30 to 35 kg HMDS slag can be used per ton of sinter to get desired properties of the sinter. Results are 30 % of HMDS with -5mm (5.9 %), 48.14 % (+10mm) Tumbler Index (67.12) with < 0.004 % of phosphorous.