Desulphurisation mechanism of direct reduction and melting in carbon bearing pellets

Abstract

The iron nugget process which utilises carbon bearing pellets is a flexible, economical and environmentally friendly iron making process. Iron nuggets which have physicochemical properties similar to those of pig iron can be obtained in a short time through high temperature smelting reduction. Sulphur content has an important influence on the quality of the iron nuggets produced. The behaviour of sulphur in the carbon bearing pellets was studied during heating at 1450°C using chemicals of analytical reagent grade as raw materials. The effect of reduction conditions, such as reduction temperature, C/O mole ratio, reducing agent species, basicity and additive agent, on the sulphur content in iron nuggets and slag after separation was investigated. Sulphur disperses in pellets in the initial stage of reduction as a result of reagent mixing. As reduction and melting proceed, sulphur is accumulated at several points in iron and slag. Slag demonstrates a strong desulphurisation ability. Very high temperatures are not conducive for reducing the sulphur content in iron nuggets. Sulphur content in iron nuggets decreases with increasing C/O ratio, basicity and the addition of Na2CO3 as a desulphurisation agent. Iron and slag can be well separated to yield high quality iron nuggets by controlling the process parameters.