Development of Fluxed Iron Oxide Pellets Strengthened by CO2 Treatment for Use in Basic Oxygen Steel Making

Abstract

Lump lime is presently being used as a fluxed material in basic oxygen steel making process. However, problems are often encountered in operation due to its high melting point, poor dissolution property, fines generation and hygroscopic property. Binary CaO-Fe 2 O 3 has a eutectic point (1 200°C) with 22 % CaO. An agglomerate of lime and iron oxide under BOF condition would thus generate low melting oxidizing slag at the beginning of blow and would facilitate refining process. In this study, lime fluxed iron oxide pellet has been prepared using waste iron oxides and its strength was developed by CO 2 /CO 2 containing gas treatment at room temperature, while no separate binders has been used. Industrial waste gases, say, blast furnace gas (BFG) may suitably be used as CO 2 source. The pellet making process parameters such as composition of pellets, grain size of iron ore fines, treatment conditions etc. have been optimized through physical characterization like cold compressive strength, drop strength, abrasive resistance etc. Up to around 30 kg/pellet cold compressive strength, around 150 drop strength and excellent abrasive property have been achieved.

High Temperature Characterization of CO2 Treated Fluxed Pellets Developed for Basic Oxygen Steel Making

“…Then the mixture was pelletized 16) in a pelletizer to 5-16 mm size green pellets and produced pellets were left in natural air for 1-3 d for drying. Different pellets prepared are shown in Table 4.…”

“…The percentage of CaCO 3 obtained through both the methods appears to be in good agreement. Moreover, XRD analyses of the outer surface and inner core of the 5 min treated pellet 16) showed more residual hydroxide at core than outer surface. Therefore, these observations support the presumption that Reaction (2) proceeds from surface towards the centre of the pellets.…”

“…During transformation of Ca(OH) 2 to CaCO 3 , a considerable volume expansion occurs. 16,17) The expanded volume is accommodated by the pores of the pellets and hence increased the compactness of the pellet and accordingly, increase in strength.…”

“…The authors developed a binderless process for the preparation of Fluxed Lime-Iron oxide Pellets (FLIP) at room temperature 16) in which hydrated lime is reacted with CO 2 gas to develop the cold strength. The operating mechanism for this room temperature strengthening is presented in brief as follows:…”

Performance Assessment of CO2 Treated Fluxed Iron Oxide Pellets in Basic Oxygen Steel Making Process

“…16,17) The expanded volume is accommodated by the pores of the pellets, increasing the compactness and subsequently, strength of pellet increases. The details of pellet preparation and its physical as well as physico-chemical characterization has already been reported elsewhere.…”