During the steel production process, nearly twice as many input materials are used as compared to finished products. This creates a large amount of post-production waste, including slag, dust, and sludge. New iron production technologies enable the reuse and recycling of metallurgical waste. This paper presents an investigation on the reduction of selected iron-bearing waste materials in a laboratory rotary furnace. Iron-bearing waste materials in the form of dust, scale, and sludge were obtained from several Polish metallurgical plants as research material. A chemical analysis made it possible to select samples with sufficiently high iron content for testing. The assumed iron content limit in waste materials was 40 wt.% Fe. A sieve analysis of the samples used in the subsequent stages of the research was also performed. The tests carried out with the use of a CO as a reducer, at a temperature of 1000 °C, allowed to obtain high levels of metallization of the samples for scale 91.6%, dust 66.9%, and sludge 97.3%. These results indicate that in the case of sludge and scale, the degree of metallization meets the requirements for charge materials used in both blast furnace (BF) and electric arc furnace (EAF) steelmaking processes, while in the case of reduced dust, this material can be used as enriched charge in the blast furnace process. Reduction studies were also carried out using a gas mixture of CO and H₂ (50 vol.% CO + 50 vol.% H₂). The introduction of hydrogen as a reducing agent in reduction processes meets the urgent need of reducing CO₂ emissions. The obtained results confirm the great importance and influence of the selection of the right amount of reducer on the achievement of a high degree of metallization and that these materials can be a valuable source of metallic charge for blast furnace and steelmaking processes. At an earlier stage of the established research program, experiments of the iron oxides reduction from iron-bearing waste materials in a stationary layer in a Tammann furnace were also conducted.

This article was conducted within the framework of project reg. no. CZ.11.4.120/0.0/0.0/16_013/0002594, programme, Interreg V-A Czech Republic-Poland, Microprojects Fund 2014–2020 in the Euroregion Silesia. It is focused in the area of modelling technological processes and the presentation of the main principles of these models. The modelling of technological processes is important in terms of its applicability to process prediction in industry. A complex of analytical and predictive metallurgical models was developed within VSB-TUO. The original mathematical model of coke degradation in a blast furnace makes it possible to calculate the minimum consumption of coke from the dynamic balance for different values of the ratio of direct and indirect reduction. As part of the graphic output, it determines the practically and theoretically achievable minimum coke consumption points. The use of the model enables the determination of a real reserve in reducing the amount of coke.

The article describes the behaviour of coke in the blast furnace. Factors, which cause weakening and degradation of coke lumps at temperatures above 1300°C have been analyzed. On the basis of preliminary testing of samples taken from a blast furnace at different distances from the tuyère outlet and tests for thermo-abrasion ξ, the advisability of using the pre-tuyère chamber for the assessment of coke quality at high temperatures has been indicated. Thermodynamic calculations for the determination of the chemical composition of the products of reaction of coke ash mineral substances with elementary carbon and air, as well as the behaviour of coke at high temperatures under inert gas conditions are presented. The number of compounds forming from coke ash components during heating in a stream of gases of highly differential reductiveness reflects the complexity of the physicochemical phenomena.

The analysis of coke quality and the effect of coke quality on blast furnace process was presented in this paper. The mechanical properties of cokes was determined by the MICUM method, the same coke samples were hot tested in the blast-furnace pre-tuyère chamber model at the Department of the Extraction and Recycling of Metals of the Czestochowa University of Technology to determine their thermo-abrasiveness ξ. Moreover, the permeability of the column of materials in the blast furnace during the use of those cokes was determined. The permeability of the materials column characterizes the “quality” of the materials, including the coke. Separating the coke features in this characteristics is possible with the remaining charge and technological conditions being stabilized. However, the high variability of charge conditions in the blast-furnace under examination distorts the existing permeabilities. Nevertheless, the dependence of the permeability on thermo-abrasiveness was “physically” correct, i.e. it decreased with increasing thermo-abrasiveness ξ, despite the small value of the coefficient of significance of this relationship.