Smelting reduction of iron ore was studied with 5 t and 170 t top-and-bottom blowing converter in the condition that stirred metal bath was separated from oxygen jet by the thick layer of slag.
The results obtained in the experiments using coke as carbonaceous materials were as follows :
(1) Heavy slag increased the rate constant of reduction per area of the geometrical slag-metal interface.
(2) The effect of bath temperature on the rate constant is small in 170 t furnace compared with 5 t furnace. Smelting reduction about 1 400°C was stably carried out in 170 t furnace.
(3) The ratio of reduction of iron oxide in three kinds of reaction sites ; bulk metal-slag, metal dropletsslag and coke-slag interfaces was calculated as, for example, 0.55 : 0.27 : 0.18 in the 5 t furnace and 0.34 : 0.33 : 0.33 in the 170 t furnace.
(4) High post combustion (about 60%), high heat efficiency (about 90%) and suppression of dust formation were achieved in both of 5 and 170 t furnace.
Hot metal was produced at the rate of 42.7 t-HM/h from ore in 170 t furnace (oxygen blow rate ; 30 000 Nm3/h).
