Abstract
Thermal recovery processes in the STB (Sumitomo Top and Bottom blowing) process have been developed and the refining characteristics have been investigated. Postcombustion process in a STB converter has been developed, applying the results of fundamental tests by a 15t STB converter to a commercial scale 160t STB converter. And then coal injection process through a top lance was combined with postcombustion. The results are as follows:(1) A lance of the two-independent-flow type is essential to postcombustion.(2) The jet angle θ2 for postcombustion should be wide as 30-35 deg.(3) The oxygen flow rate through PC nozzles should be about 20% of the total oxygen flow rate.(4) The thermal recovery efficiency of postcombustion is very high, nearly 100% in a 15t STB converter and 70% in a 160t STB converter.(5) Although postcombustion causes no change in % (T.Fe) in the slag at the end point, it increases (Fe3+) in the slag and improves dephosphorization of the hot metal.(6) The large amounts of heat can be effectively used to improve the heat balance in a converter by using the TAPS (Triple Action Process of STB; coal injection from a top lance with postcombustion).(7) In the case of the TAPS, as the coal injection interferes with postcombustion, it is necessary to inject coal effectively within a short time.
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