The rotating disk methodology has been used for examination of the reduction of FeO from CaOFeO-SiO 2 liquid slags (20 and 60 pct FeO) with a CaO/SiO 2 ratio equal to 0.66 and 1.27, in the temperature range 1350 ЊC to 1420 ЊC. It has been found that the reduction proceeds under diffusion control. The calculated diffusion coefficients fall in the range 0.76 и 10 Ϫ7 to 1.6 и 10 Ϫ6 cm 2 /s. Comparison of these values with those given in the literature suggests that the calculated coefficients are related to the diffusion of oxygen ions in the slag. The calculated thickness of the limiting diffusion layer, ␦, ranges from 0.65 и 10 Ϫ3 to 5.25 и 10 Ϫ3 cm, depending on the reduction conditions. The largest decrease in the limiting diffusion layer thickness takes place at low rotational speeds, i.e., 100 and 400 rev/min. The maximum value of the mass transfer coefficient is 1.71 и 10 Ϫ3 cm/s for reduction from slag with a CaO/SiO 2 ratio of 1.27, 60 pct FeO, at 1420 ЊC and 2000 rev/min, and the minimum value is 0.27 и 10 Ϫ4 cm/s for reduction from slag with a CaO/SiO 2 ratio of 0.66, 20 pct FeO, at 1350 ЊC and 100 rev/min. Good agreement has been found between experimental and calculated reduction rates at low disk rotations (100 and 400 rev/min).

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.

As a result of manufacturing processes, steelworks plants produce large amounts of waste materials. Currently in modern steelworks the most of waste is utilized in the same steelworks and passed to external customers or it is reused as a feed for other technological processes. Finegrained metallurgical waste materials are used to production of granules because of the high contents of iron and other valuable elements. Granulation of iron-bearing waste materials increases permeability of blend and performance of the sinter strand. Dosing of material in the form of granules to an average sinter mix may be accomplished in a more controlled manner than is the case for bulk material. Due to recycling carried out by adding granulated wastes to blast furnace charge or to sintering process the cost of production of steel is reduced. This procedure allows metallurgical sector on the delivery of measurable economic, technological and environmental benefits. In this work the chemical composition, grain size and the possibility of using fine-grained iron-bearing wastes are presented.

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