Nk. Batra, ADIABATIC FLAME TEMPERATURE AND SILICON TRANSFER IN A BLAST-FURNACE, Transactions of the Indian Institute of Metals, 50(2-3), 1997, pp. 169-180
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.