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.
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.
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 main purpose of this paper was to analyze the behavior of coke in the blast furnace. The analysis of changes in chemical composition of coke due to impact of inert gas and air at different temperatures was made. By applying the FactSage three groups of substances can be distinguished. The chemical composition of blast furnace coke and the results of calculations of changes of chemical composition of coke heat treated under certain conditions were compared. The structural studies of these materials were presented. The results of the analysis of ash produced from one of Polish cokes was taken for consideration. This is not the average composition of Polish coke ashes, nevertheless it is representative of most commonly occurring chemical compositions.Keywords: coke, ash in coke, thermochemical calculations 1 Introduction Coke contains approx. 1% of volatile substances and approx. 10% of mineral substances. So, it is legitimate to claim that the liberation of these volatile substances and a slight evaporation of the mineral compounds will occur under the blast-furnace conditions [1 -10]. As a fuel and an iron oxide reducer, coke performs also the function of a framework supporting the charge. However, in the lower part of the blast furnace shaft, the mechanical properties of the coke worsen. The change of these properties is affected by factors, such as [11][12][13][14][15][16]: 1) gasification reactions; 2) thermal factors; 3) blast-furnace blast. These factors contribute to the formation of coke dust that densifies the primary slag thus making its flowing down difficult and also reducing the charge permeability. The thermal interactions reduce the strength of the coke due to the change in internal stresses in the structure. This is also associated with the presence of mineralogical and organic inclusions in coals subjected to coking. The thermal conductivity of the coke increases as its volatile matter contents decreases. As the volatile substances are released from the coke, a loss and a shrinkage of the solid part result, which leads to a reduction in strength [17].
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