ADIABATIC FLAME TEMPERATURE AND SILICON TRANSFER IN A BLAST-FURNACE

Thermal state of the hearth of a blast furnace may be measured in term s of adiabatic flame temperature. This is defined as the temperature a ttained by the tuyere gases at the completion of the combustion reacti ons in the raceway reg ion. Factors that determine the flame temperatu re include the blast temperature, blast humidity, oxygen enrichment of the blast, injectants through the tuyeres and presence of silica rich ash in coke. Actual temperature is affected by the rate of heat losse s through the walls and water cooled tuyeres. Silica present in the co ke affects the flame temperature by its pre-transformation to silicon carbide in the bosh region, its reoxidation to silica and subsequent d issociation to silicon monoxide in the raceway region. Iii the present work, model equations are developed and solved using a computer to de termine the temperature and composition of the tuyere gases as a funct ion of the degree of combustion. Dissociation of carbon dioxide to for m carbon monoxide and that of silica to form silicon monoxide vapours are taken into account in the model equations. Peak temperatures occur at around 50 to 65% degree of combustion due to the endothermic natur e of the dissociation reactions. Silicon monoxide formed in the combus tion zone takes part in the gas metal and gas slag reactions in the bo sh region and it results in the transfer of silicon to the blast furna ce iron. Reoxidation of metal might occur in the hearth region and low er its silicon content slightly due to high oxygen potential of the sl ag and that of the blast.