Adaptation of the Rist Operating Diagram as a Graphical Tool for the Direct Reduction Shaft

The blast-furnace operating diagram proposed by Rist was revised to direct reduction and was specifically applied to the Midrex NGTM process. The use of this graphical tool in the study of an industrial process highlighted the staggered nature of the reduction in the shaft furnace with, in particular, the existence of a prereduction zone in the upper part where metallization is thermodynamically impossible. A sensitivity study also showed the impact of the in situ reforming rate on the ability of the gas to completely reduce iron oxides. Finally, we graphically defined the minimum quality required for the top gas to produce direct-reduced iron.

A Numerical Study on the Performance of the H2 Shaft Furnace with Dual-Row Top Gas Recycling

Given the urgent pursuit of carbon neutrality and stringent climate policies, the H2 shaft furnace (H2-SF) is starting to gain widespread attention in the steel industry. In this study, the performance of the H2-SF under operation with a dual-row injection top gas recycling system was investigated by a one-dimensional mathematical model. The potential of microwave heating as a means to supply thermal energy in regions of energy deficit was also assessed briefly. The results showed that for scenarios without microwave heating, increasing the upper-row injection rate can improve the furnace performance, and increasing the distance of the upper-row injection level from the furnace top also has a positive effect. A high microwave heating efficiency is expected in regions above the upper-row injection level. For scenarios with microwave heating, a higher microwave power leads to a better furnace performance. Thus, a higher furnace productivity can be achieved by increasing either the upper-row injection rate or the microwave power. However, the latter seems more promising as it decreases the total energy demand due to a better utilization of thermal energy. Based on the comparison of two representative examples, the decrease in the total energy demand is about 0.2 GJ/t-Fe.

A mathematical model of metallization of titanium-magnetite ores of Kachkanar deposit in Midrex shaft furnace

Development of a technology for obtaining direct reduction iron from titanium-magnetite ores, which will be the main ore base of the Ural ferrous metallurgy in the future, is one of the urgent tasks of metallurgical science. The world and domestic experience of the development of direct iron reduction processes, which are the most environmentally friendly of all existing methods of obtaining iron from ore considered. It was shown that the technology of metallization of iron ore materials in the Midrex shaft furnace has received the most widespread application. It is noted that the accumulated experience of using Midrex technology in Russian Federation will allow increasing the production of metallurgical raw materials with a reduced carbon footprint. An algorithm and a block diagram for calculating technical and economic indicators of the metallization process for the Midrex process shaft furnace are described. A methodology for calculating material and thermal balance of the Midrex process has been developed, taking into account the use of iron ore raw materials containing vanadium and titanium in the charge. On its basis, an algorithm was developed and a mathematical model of the metallization process was implemented, calculations of the metallization process of titanium-magnetite pellets obtained from the ores of the Kachkanar deposit in the Midrex mine furnace were performed. A comparison of the indicators of the metallization process of titanomagnetite pellets carried out in the shaft furnace of JSC “OEMK named after A.A. Ugarov” and obtained using the created software product showed satisfactory convergence of the results.

Thermodynamic Analysis of Siderite Ore Carbonate Decomposition Process at Roasting

Carbonate decomposition with significant heat energy absorption takes place at siderite ore oxidizing roasting in a shaft furnace. Thermal dissociation of complex carbonates comprising the siderite ore was studied. Thermodynamic analysis was carried out for a sideroplesite decomposition process. Formulas allowing determination of the carbonate dissociation and exchange energy rates were obtained using the regular ion solution theory. The ion composition and thermodynamic activity simulation results were described for sideroplesites as well as iron and magnesium cation shares. The work output is of certain interest as knowing the initial sideroplesite decomposition temperature and the carbonate dissociation rate the optimal dimensions of various zones throughout the shaft furnace height may be defined, the roasting process time may be calculated and the optimal heat treatment conditions as well as the firing rate may be established.