Dn. Patel et al., HEAT-TREATMENT OF COKE IN THE TEMPERATURE-RANGE OF 1400-DEGREES-C-1650-DEGREES-C, Transactions of the Indian Institute of Metals, 47(4), 1994, pp. 221-228
Coke which is manufactured in the by-product coke oven by heating coal
to around 1000-degrees-C in absence of air gets heated to much higher
temperatures of 1500-degrees-C or more before taking part in the comb
ustion reaction in the raceway region of a blast furnace. It is estima
ted that 20 to 30% of carbon in the coke takes part in the Boudouard r
eaction in the direct reaction and carburising zones of the furnace in
the temperature range of 1000 to 1300-degrees-C and rest of the mass
remains more or less intact. Samples collected from the tuyere region
of a blast furnace during the off-blast period show 2 to 3% more ash t
han the skip coke due to the loss of carbon from the coke and gasifica
tion of a part of its silica to silicon monoxide. Coke sample when hea
t-treated in the laboratory in absence of any diffusion influx of air
did not undergo much changes in its composition and weight upto 1500-d
egrees-C but suffered a loss of 12 to 16% in its weight alongwith slig
ht lowering of silica in the ash in the temperature range of 1550 and
1650-degrees-C. Results are attributed to the transformation of silica
to silicon carbide at around 1540-degrees-C and simultaneous loss of
10 to 20% of silica as silicon monoxide vapours in the gas phase. In a
blast furnace, such changes which might take place in the vicinity of
the raceway region would lead to recycling of silicon carbide and sub
stantial transfer of silicon to the metal in the bosh region.