Quality of Lime for Steelmaking in Converter Sep08

Quality of Lime for Steelmaking in Converter...

Quality of Lime for Steelmaking in Converter Lime is a white crystalline solid with a melting point of 2572 deg C. It is a basic oxide and is used to react with the acidic oxides (e.g. silica). It is calcium oxide (CaO) produced on heating (calcination) of limestone (CaCO3) to a temperature of 900 deg C and above (usually 1100 deg C). CaCO3(s) + heat = CaO(s) + CO2 (g) This reaction is reversible. Calcium oxide reacts with carbon dioxide to form calcium carbonate. The reaction is driven to the right by flushing of carbon dioxide from the mixture as it is released. Hydrated lime Ca(OH)2 is formed by reaction of lime with water (slaking). Hydrated lime is also known as slaked lime. CaO + H2O = Ca(OH)2 + heat Lime as a basic flux in steel production and it plays an important role in the sequence of metallurgical reactions taking place in a converter. Steel is produced from hot metal by oxidizing sulphur (S), phosphorus (P), carbon (C), silicon (Si), manganese (Mn), and other impurities so that they can enter the slag or gas phases, thus separating from the metal phase. Lime in steelmaking is mainly used to produce slag for the removal of these harmful elements in liquid bath and optimize the quality of liquid steel. The basic oxygen process oxidizes impurities in an oxygen converter also known as basic oxygen furnace (BOF) where the hot metal comes in contact with oxygen. Oxidized impurities of the hot metal are absorbed in a slag, which is formed with the help of calcined lime. Metallurgical lime in the fifties consisted of a mixture of particles of all sizes from very coarse to very fine, with additional components such as silicon dioxide and sulphur concentrated...