Refining of hot metal utilizing fluxed iron oxide pellets

Abstract

Fluxed iron-oxide pellets were prepared using waste iron oxide fines and lime fines and subsequently treated with industrial waste through room temperature binder less process that developed its handling strength (CCS 30 kg/pellet). It has the potential to partially replace scrap and lump lime as BOF charge material. In order to assess the suitability of pellets in refining, performance of the treated pellets in the refining of hot metal was investigated in a laboratory-scale, bottom blowing ladle, lined with magnesite. The hot metal was prepared by melting pig iron chips in an induction furnace, which was subsequently transferred to the bottom blowing ladle. Refining was carried out with the following three flux combinations, viz. i) Heats with lime alone as flux ii) Heats with treated pellets plus additional lime as flux, iii) Heat with iron ore plus lime as flux. Pellets containing 30% lime in their base mixtures were used in this performance study. Parameters like oxygen flow rate, initial temperature and composition of hot metal, slag basicity, etc. were kept constant in all heats as far as practicable. The progress of the removal of C, P, Si, and Mn was studied by collecting metal samples from the refining bath at different blowing stages for chemical analysis. C, P and Mn removals were observed to be faster with the use of pellets than with the other two combinations (combinations-i. and iii.). It was also found that the pellet addition in the proportion of 8% of hot metal brought about a greater removal rate of carbon than that in higher (10%) or lowers (5%) proportions. the metallic yield was found to improve by 1.4%, in comparison with the use of lime alone as flux. Also, there was a remarkable saving in oxygen consumption. This study mainly emphasizes on the comparative heat and mass balance in different flux conditions and analysis of thermodynamic and kinetic aspect of comparative C, P, Si and Mn removal in aforementioned conditions.