Chemistry of Steelmaking by Basic Oxygen Furnace Dec08

Chemistry of Steelmaking by Basic Oxygen Furnace...

Chemistry of Steelmaking by Basic Oxygen Furnace During the steelmaking process by basic oxygen furnace (BOF), impurities in hot metal such as carbon (C), Silicon (Si), manganese (Mn), phosphorus (P) etc. are removed by oxidation for the production of liquid steel. Oxidation is carried out with high purity oxygen gas which is blown in the BOF. The oxidation reactions result into the formation of CO, CO2, SiO2, MnO, and iron oxides. While CO and CO2 are in gaseous form and removed from BOF top as converter gas, other oxides are dissolved with the fluxes added to the BOF, to form liquid slag that is able to remove sulphur (S) and phosphorus (P) from the metal. BOF process has two characteristics. First, the process is autogenous that meaning that no external heat source is needed. The oxidation reactions during the oxygen blow provide the energy needed to melt fluxes and scrap and to achieve the desired temperature of liquid steel. Second, the process refines hot metal at high production rates for the production of liquid steel. The fast reaction rates are due to the large surface area available for reactions. Large amount of gas is evolved when oxygen is injected into the bath of metal. This gas forms an emulsion with the liquid slag and metal droplets sheared from the bath surface by the impingement of the oxygen jet. The large surface area generated by gas- metal- slag emulsion increase the rates of the refining reactions. Since the impurities are dissolved in the molten metal, reactions between impurities and oxygen occurs with dissolved oxygen. Further since oxidation of carbon takes place at higher temperature, carbon oxidation to CO is highly probable and hence majority of C is removed as CO. The oxidation reactions which take...