底吹き転炉を用いる生石灰系フラックスによる溶銑脱燐の反応機構

概要

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Hot metal dephosphorization in Q-BOP was shown in the previous work to be very quick and efficient. Experiments have been made to determine the contribution to the dephosphorization of top slag (permanent reactor reaction) and of lime powders injected from bottom tuyeres with O_2 gas and ascending in the bath (transitory reaction). The ratio of dephosphorization, 100{[P]_<initial>-[P]_<final>}/[P]_<initial>reached 90-95% when fluorspar is added either to injected lime or to resulting top slag, whereas it decreased to 50-70% without the fluorspar addition. Detailed analysis has shown that 50-70% of the above ratio of dephosphorization is shared by the transitory reaction, the rest of 0% (without fluorspar) to 25-40% (with fluorspar) by the permanent reactor reaction. Slag particles ascending in the bath have been sampled and found to contain 10-30%P_2O_5, confirming the considerable contribution of the transitory reaction. With the aid of additional laboratory experiments, the following sequence is found operative for the dephosphorization : Lime particle injected with O_2 gas is transformed to calcium ferrite. During ascending in the bath, calcium ferrite oxidizes [P] to P_2O_5, itself being reduced to CaO which combines with P_2O_5 to form 3CaO・P_2O_5 particles.
1982-09-01