Production of High Reactivity Coke by Utilization of Low-Grade Coal and Steel Plant Wastes

Abstract

Steel industries around the world have been trying to improve the blast furnace efficiency in order to reduce energy consumptions and decrease the reducing agent rate. One of the most popular techniques of achieving this is by decreasing the thermal reserve zone temperature inside the blast furnace by the use of High reactivity coke. Due to its high reactivity, the reaction starting temperature of coke in the reversible Boudouard reaction is lowered, which results in the decrease of thermal reserve zone temperature. As a result, the reducing agent rate is decreased, resulting in lower energy requirements and also lesser greenhouse effects due to lower emissions of CO2 into the atmosphere. This higher reactivity is achieved by adding certain substances into the coal blend which exhibits positive catalysis on the gasification reaction of coke. Also, due to the gradual shrinkage of coking coal reserves, there is a constant urge to improve existing techniques and develop innovative technologies to utilize non-coking and slightly coking coal as much as possible by blending with coking coal during carbonization in coke ovens. In order to achieve these, certain binders are to be added into the coal blend which will help to maintain the coke strength in spite of addition of non-coking coal.
In this research work, the briquetting technique was utilized for producing coke using non-coking coal up to 40%. The potential of different steel plant wastes and by-products like powdered iron ore, iron (III) oxide, LD Slag and sinter return fines were studied and the optimum proportion was obtained as 10%. The use of coal tar pitch and petroleum pitch binders were also studied extensively and their optimum proportions were obtained as 3% in case of coal tar pitch and 2% in case of petroleum pitch. Also, experiments were carried out to check the corrosion of coke oven bricks due to the reaction of silica in brick with the externally added iron ore. Later, lump coke was produced in a 7 kg oven by blending different iron-bearing additives into the coal and then carbonizing the mixture, in order to enhance the reactivity and strength of coke produced. The coke produced was tested and compared with conventional coke in terms of its reactivity, strength and porosity.