The Characteristics and the Function of a Thick Slag Layer in the Smelting Reduction Process.

Abstract

The characteristics of the slag layer in smelting reduction with a large amount of slag were examined with various devices, and its influence on the operation performance was investigated.(1) The characteristics of slag layer. The average density of the slag layer calculated by the detected slag height was 0.6-1.1 t/m3. In the practical smelting reduction condition, the average density of slag layer seems to be 0.8-1.0 t/m3. The temperature difference between the slag layer and the metal bath was 30°C or less. The amount of metal droplets in the lower 30 vol% of the slag layer reaches 30 wt% or more. In the upper 70 vol% of the slag layer, it depends on the stirring intensity of metal bath and slag compositions. 85-95 wt% of these originated in the stirred metal bath according to the tracer test.By combining the sampling test and the calculation using measured data, the distribution of carbonaceous materials in the slag layer could be obtained.(2) The influence of the characteristics of slag layer on the operation performance: The increase of metal droplets in the slag layer decreases post combustion and increases iron dust generation. The increase of the amount of slag decreases the generation of iron dust and carbon dust. When coal is used instead of coke, the carbon content of the metal bath decreases. This phenomenon was explained by the distribution of carbonaceous materials and metal droplets in the slag layer.The principle for the simultaneous achievement of high post combustion, acceleration of reduction and heat transfer, suppression of dust generation, and the adjustment of carbon content of metal bath by controlling the distribution of metal droplets and carbonaceous materials in slag layer is shown.