In order to improve the refining characteristics in the bottom blowing converter (Q-BOP) at Chiba works, the oxygen flow rate at the final stage of the blowing was decreased by reducing the diameter of the bottom tuyere.
The results obtained are summarized as follows:
(1) By lowering the oxygen flow rate at the final stage of the blowing, the improvement in the decarburization efficiency is achieved. Consequently, (T.Fe) in slag is lowered.
(2) The effect of the dilution of the partial pressure of CO, Pco, on the metallurgical characteristics is small in Q-BOP. Therefore, for the improvement in the metallurgical characteristics the reduction of the oxygen flow rate is better than the mixed gas blowing.
(3) The increase in the pressure of the oxygen gas improves the decarburization efficiency at the same gas flow rate.
(4) On the basis of the mass transfer model considering the turbulent theory, the mass transfer rate in the reaction zone is assumed to be increased with the increase in the gas pressure. The improvement in the decarburization efficiency by the increase in the gas pressure in Q-BOP is well described by this increase in the mass transfer rate in the reaction zone.
