COMPARATIVE EVALUATION OF THE EFFICIENCY OF VARIOUS MATERIALS IN THE PROCESS OF REDUCING MAGNETITE FROM SLAG MELT

ABSTRACT

The article presents a comparative analysis of studies on the reduction of the magnetite mineral contained in the slags of the copper smelter. Carbon, iron, and sulfur were chosen as reducing substances, and information about their relatively cheap local sources is given. According to a comparative analysis of the studies carried out, the reduction of magnetite to slag with elemental sulfur gave better results compared to other reducing agents.  

АННОТАЦИЯ

В статье представлен сравнительный анализ исследований по восстановлению минерала магнетита, содержащегося в шлаках медеплавильного производства. В качестве восстановительных веществ выбраны углерод, железо и сера, приведены сведения об их относительно дешевых местных источниках. Согласно сравнительному анализу проведенных исследований, восстановление магнетита в шлак с элементарной серой дало лучшие результаты по сравнению с другими восстановителями.

Keywords: magnetite, slag, reduction, carbon, iron, sulfur, temperature.

Ключевые слова: магнетит, шлак, восстановление, углерод, железо, сера, температура.

From the theory of pyrometallurgical processes and the practice of metallurgical enterprises, it is known that magnetite in a molten slag can be reduced by the following reactions [1-2].

Fe₃O₄ + C = 3FeO + CO                                             (1)

Fe₃O₄ + Fe = 4FeO                                                 (2)

2Fe₃O₄ + S = 6FeO + SO₂                                           (3)

To evaluate the effectiveness of various reducing agents, special studies have been carried out. The experiments were carried out according to the procedure described in [3]. For research, a synthetic slag was prepared similar in composition to the real converter slag in the composition, %: 26 SiO₂; 53 FeO and 21 Fe₃O₄. The carbon source was the magnetized fraction after the magnetic separation of the clinker of the zinc plant (Almalyk MMC), and the magnetized fraction after the magnetic separation of the clinker of this plant was used as the source of iron [4]. In addition, technical sulfur from the Mubarak Gas Processing Plant was chosen as a source of sulfur. The results of the conducted studies are presented in Figure 1 and Table 1.

Figure1. Change in the residual content of magnetite over time when using various materials, temperature - 1300 ° C: 1 - sulfur; 2 - iron; 3 - carbon

Table 1.

Influence of the reducing agent material on the kinetics of magnetite reduction in slag of the initial composition, %

As can be seen from the above results, sulfur turned out to be the most effective reducing agent in this case. The reducing power of solid carbon and iron is approximately the same [5-6].

A certain scientific and practical interest is the study of a deeper degree of reduction of magnetite to wustite and up to the appearance of metallic iron in time [7]. For this purpose, according to the previously described method, studies were carried out on the reduction of magnetite with a solid reducing agent located in the slag melt. The studied slag had the composition, %: 20 Fe₃O₄, 25 SiO₂, 55 FeO. Experiments were carried out at temperatures of 1250 ^oC, 1350 ^oC. The results of the experiments were controlled by X-ray microanalysis [8].

The mineralogical analysis of a vertical section of a carbon-slag sample taken 2.7 · 10³ s and 3.6 · 10³ s after the start of the experiment at a temperature of 1250 °C showed that carbon did not undergo any noticeable changes. In the main volume of slag there are relatively large (0.05¸0.1 x 0.5¸2.0 · 10^-3m) fayalite crystals, between which there are glass, magnetite and fine-grained fayalite [9]. The content of magnetite in general over the entire plane of the slag section is about 2% at 2.7· 10³ s, 1% at 3.6 · 10³ s. In the horizontal section from carbon to the crucible wall, there is no appreciable difference in the concentration of Fe₃O₄. On the border with carbon, in some places there are areas of one fayalite and acid glass. There is no metallic iron in the sample [10].

After 1.8 · 10³ s of being in the slag at 1350 °C, carbon samples were subjected to severe corrosion, and drops of cast iron accumulated on their surface in abundance. In the horizontal and vertical sections of the cut section, carbon is slag, magnetite is absent. The data obtained are in good agreement with the data in Table 1 in terms of the reduction of magnetite molten slag with carbon-containing material.

Based on the studies conducted on the comparative evaluation of the effectiveness of various materials, it is necessary to select a relatively cheap reducing agent, preferably produced in our Republic, since import is very problematic due to the high cost of the material, transportation costs, taxes, etc. In the absence of a reducing agent in Uzbekistan, it is possible to use its substitute in the form of a sulfur-containing middling product of metallurgical and chemical industries.

In this regard, a search was made for an alternative source of reducing agents. This material turned out to be a composite material in the form of technical sulfur and zinc production clinker, which is a technogenic raw material in the form of an intermediate product from the Waelzing of zinc cakes. Hundreds of thousands of tons of this material have accumulated in special storages and can be used without special preliminary preparation.

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