Two measures for coke saving and increase in blast furnace efficiency related to coke characteristics -reactivity and size -are discussed in this paper. Modern blast furnace operation with low coke rate and high injection rate causes a change in coke quality requirements. A discussion has arisen recently about highly reactive coke. Here, a theoretical analysis of influence of coke reactivity on the thermal reserve zone, direct reduction and carbon consumption in the blast furnace has been undertaken. Experiments have been performed using non-standard test scenarios that simulate coke behaviour under real blast furnace operating conditions. Coke reactivity and microstructure have also been investigated under the impact of alkali and pulverised coal ash and char. Operation of many blast furnaces has proved the possibility of coke saving and increase in productivity when using small-sized coke (so-called nut coke) mixed with the burden, but the reasons for this phenomenon, and consequently the limit for nut coke consumption, are still not very clear. An analytical method and cold model simulations have been used to quantify the change in shaft permeability and furnace productivity when using nut coke.

In this review paper described are possible chemical reactions and their thermodynamic analysis during direct reduction. The sticking mechanism during direct reduction in the fluidized bed was analysed, and the reasons for the sticking appearance explained. The most important parameters on the sticking were analysed. The ways for prevention and observation were considered. The plan for experimental investigations was proposed. The investigations could be performed in fluidized bed reactor. Coal will be used as inert material. Separately, the influence volatile content in the coal on the reduction process and sticking appearance, will be analysed. As results of these investigations would be some improvements of the method direct reduction of iron ore in the fluidized bed.

In the present paper, a study has been made of carbon dissolution from industrial cokes and specially treated cokes in hot metal. With these results obtained together with earlier investigations, a model is now presented, which attempts to explain carbon pick‐up from coke by hot metal. Factors relating to hot metal, coke and experimental conditions are included in the model. An attempt is also made to quantify carbon dissolution behaviour from coke in hot metal in comparison with that of pure graphite. It was determined, that the carburizing ability of cokes can be modified by controlling the ash compositon. The results of the special cokes indicate clearly that the presence of iron oxide is favourable for carburization. Some additives, i.e. CaO, MgO, SiO2 and Al2O3 reduce significantly the dissolution of carbon.

Comparing the four fundamental ironmaking processes the reasons for the development of smelting reduction were derived. Based on bibliographical references a fundamental classification of the main important smelting reduction processes is presented regarding the process engineering principle of both steps, prereduction and final reduction. According to fundamental considerations, the fluidized bed process seems to be optimal for prereduction. Experiments to investigate the influence of process parameters on sticking – the main problem of fluidized‐bed reduction – and their interactions were carried out. Optimal operating conditions to run a fluidized bed as the prereduction unit of smelting reduction process were derived. A special “Reduction‐SEM” to directly observe metallurgical reactions, like the precipitation behaviour of iron during iron ore reduction, is presented. With the results of such investigations it is possible to show the influence of precipitation behaviour on sticking and to assign the different types of precipitates to the Baur‐Glaessner‐Diagram. The influence of hydrogen addition on surface morphology is sketched out.