The processes of iron oxides’ reduction have a complex physicochemical mechanism, with the participation of solid, liquid, and gaseous substances. The article discusses the existing models for the reduction of iron oxides and provides data on the thermodynamic possibility of carrying out the reactions of their reduction through the solid and gas phases. Experimental data on the reduction of iron from industrial scale, obtained by the DSC (differential scanning calorimetry) method, show the kinetic dependence of the rate and completeness of recovery on external factors: pressing pressure during sample preparation and the reagents’ composition. The pressing pressure, under conditions of iron ions’ solid-phase diffusion, has the significant effect by increasing the reagents’ contact area. Under conditions of iron ions’ comprehensive diffusion, the pressing pressure does not affect the reduction processes rate. The introduction of 10 mass.% flux into the raw mixture composition leads to a partially liquid-phase diffusion of iron ions and weakens the effect of the pressing pressure in this process. An ion diffusion-catalytic mechanism is proposed to describe the observed effects during the reduction of iron oxide of technogenic origin.

In efforts to reduce metal costs, it is important to extend the lining life in metallurgical systems [1]. In particular, the linings of vacuum units account for a considerable portion of total refractory costs.Three groups of factors affect the lining life in cir culatory vacuum units [2]:(1) structural factors (the shape and size of the metal framework, the lining design, the format of the refractory pieces, and so on);(2) the physicochemical properties of the refracto ries, which depend on the quality of the raw materials, the manufacturing technology, and so on; (3) technological factors (the operating conditions of the metallurgical system, the slag composition and properties).Specialists at OAO EVRAZ NTMK have been studying these factors, in order to improve the refrac tory components and optimize their operating condi tions. The results assist in the development and intro duction of new lining configurations with improved performance and longer life.On that basis, measures have been taken to improve the operation of the vacuum units at OAO EVRAZ NTMK. STRUCTURAL FACTORSIn the converter shop at OAO EVRAZ NTMK, the lining configuration illustrated in Fig. 1 is employed in the vacuum unit. A deficiency of this configuration is that the junction of the refractory ring and the refrac tory concrete at the end is rapidly worn, as is the region where the transporting gas is supplied (Fig. 2). During operation, the liquid steel penetrates into the damaged surface and erodes the metallic plate that supports the refractory rings at the end of the tube. That leads to settling of the lower ring of the tube and the formation of a gap between the rows of components. In subse quent operation, metal melt leaks into the gaps, pro ducing local erosion around the circumference (Fig. 3). The vacuum chamber requires premature repair [2,3]. This problem at the junction of the refractory concrete and the refractory rings may be eliminated by adopting the design in Fig. 4. In that case, there is no horizontal junction between the concrete and the refractory ring, and the lower ring is rigidly fixed. In the course of operation, the modified structure does not permit per ceptible settling of the refractory rings. The mean life in experimental vacuum chambers was 106.0 melts (as against 102.0 melts for mass produced components). PROPERTIES OF THE REFRACTORIESSpecialists at OAO EVRAZ NTMK pay great attention to the refractory components obtained from suppliers and, in particular, their susceptibility to wear [4]. Research shows that the unit wear of refractories in the discharge tube does not depend on the overall properties but is largely determined by the characteris tics of the intake refractories. The operating condi tions are most intense at the intakes: additional cool ing of the refractory surface in the period between melts by neutral gas and considerable turbulence of the metal, which tends to erode the brick.It is evident from the table that the components dif fer considerably in properties and working life. For more detaile...