The Development Of High Reactive Ferro-coke And The Study Of Reaction Mechanism

Ferro-coke,also known as high reactive ferro-coke,is made of iron-containing material and coking coal.In the blast furnace smelting process,it can react with CO₂ at a lower temperature,and the temperature of the blast furnace thermal reserve zone can be reduced,thus,the FeO-Fe reduction equilibrium point is changed,resulting in less coke consumption and CO₂ emissions.However,the low coke strength after reaction（CSR）seriously restricts the use range of ferro-coke in blast furnace,therefore,it has become one of the research directions of coking workers to develop ferro-coke with high CSR.In this paper,the effects of iron ore powder types and proportion,coking coal properties(coalification degree index(V_daf),caking index（G）),coking process conditions（bulk density,soaking time,heating rate）and coal tar pitch on ferro-coke performance were systematically studied,and the mechanism of iron oxide conversion in ferro-coke was analyzed,and making the explanation on the mechanism of ferro-coke solution loss reaction from its microstructure,which laid a theoretical foundation for the production of"double high"ferro-coke.The results show that the Canadian iron ore powder is the best additives than Western Hubei iron ore powder and Australian iron ore powder,and the mechanical strength and thermal properties of the ferro-coke are deteriorated with the increasing of its proportion,fortunately,the ferro-coke can maintain better performance when the proportion of the Canadian iron ore powder is less than 10%.The ferro-coke has the best performance when the Vdaf is about 27%and the G is in the range of 80～82.Apart from the above conditions,the optimal coking process conditions were as follows:the bulk density is 1.0t/m³,the soaking time is 120min and the heating rate is 2.5℃/min.Under the optimal coking conditions,with the increase of pitch ratio,the ash and the sulfur in ferro-coke gradually decrease,the porosity decreases firstly and then increases,and the mechanical strength and thermal properties are optimized when the proportion of pitch is 10%.The analysis of the iron and the microstructure observation in ferro-coke show that most of the iron oxide in the coking process is reduced to metallic iron and distributed irregularly in the coke matrix with irregular size and shape.With the increase of the ratio of iron ore powder,the reduction rate of the iron oxide increases,at the same time,the beginning temperature of coke solution loss reaction gradually decreases,there is a good linear correlation between both,which is directly related to the catalytic effect of the metallic iron.The microstructure of the ferro-coke before and after solution loss reaction shows that the CO₂ gas is preferentially reacted with the outside of the ferro-coke due to its high reactivity,which has played a protective role in the ferro-coke so that the coke strength wouldn’t decline too much.