The aim of having 'good quality uxes' is that all the ux charged will go into solution and will do so relatively Ferruginous lime is the term applied to burnt lime quickly. In this regard, the structure of burnt lime (pores, (CaO) coated with dicalcium ferrite (2CaO.Fe 2 O 3 ). channels) resulting from the properties of the limestone Its high degradation strength, its resistance to employed, practices at the lime kiln, time exposed to the hydration, and its capacity for fast and complete atmosphere (moisture content, loss on ignition (LOI)), and solution of fluxes in the basic oxygen and electric sizing of the particles will all have a signi cant impact on arc furnaces make it extremely attractive as a the ease and eYciency of ux solution in the electric arc steelmaking flux. The objectives of the present work furnace (EAF) and the basic oxygen furnace (BOF). were to assess the feasibility of producing Fresh, soft burnt lime has the optimum structure to ferruginous lime in a rotary kiln type reactor, and avoid being 'choked', i.e. an open structure with pores and to determine the operating conditions favourable channels that allow the slag to penetrate right into the lime for both the formation of a hydration resistant particle and so facilitate solution. To summarise, early blow product and the minimisation of problems such as lime solution will be encouraged by: fresh, soft burnt lime; accretions and agglomerations within the reactor.a high slag iron oxide content produced by an initial soft With respect to processing conditions, the trials blow; or another slag uidising agent. suggested that ferruginous lime be generated usingThe following relationship, after Gaye, 8 expresses the a peak reaction temperature of 1260°C and allowing equivalence of other slag components to FeO in a steelmaking 45 min at greater than 1200°C. The optimal oxide slag addition is 10% by weight of the limestone charge to the rotary lime kiln. When subjected to short FeO* = % FeO +% MnO + 2•2(% Al 2 O 3 +% TiO 2 ) duration hydrating conditions, i.e. 30 min in contact with steam at 100°C (according to ASTM +4•1% CaF 2 specification X6), the ferruginous lime productwhere FeO* may be regarded as the eVective FeO level. The exhibited good resistance to hydration (relative to higher is the FeO*, the greater is the solubility of dicalcium pure CaO) and moderate physical degradation.silicate and, hence, the better is the early blow ux solution. Laboratory tests demonstrated the significantly enhanced rate and degree of dissolution of ferruginous lime (compared with uncoated lime) in PRODUCTION OF FERRUGINOUS LIME a steelmaking slag. I&S/1635 Literature reviewDr Lee (mark.lee@corusgrou p.com) is with Corus -Teesside A literature review in the area of ferruginous lime production Technology Centre,

Ferruginous lime-i.e. burnt lime coated with dicalcium ferrite (2CaO.Fe 2 O 3 )-has attractive properties as a steelmaking flux. Work was undertaken to assess the feasibility of producing ferruginous lime in a rotary kiln-type reactor and to determine the operating conditions favourable for both the formation of a hydration-resistant product and the minimization of such problems as accretion and agglomeration within the reactor. The trials indicated that a period of 45 min at temperatures in excess of 1200°C with a peak reaction temperature of 1260°C provides appropriate conditions for the production of ferruginous lime. The optimal oxide addition is 10% by weight of the limestone charge to the rotary lime kiln. When subjected to hydrating conditions of short duration, i.e. 30 min in contact with steam at 100°C (in accordance with ASTM specification X6), the product exhibited good resistance to hydration relative to pure CaO and moderate physical degradation. Laboratory tests demonstrated the significantly enhanced rate and degree of dissolution of ferruginous lime in a steelmaking slag relative to that of uncoated lime.