CALCULATION OF THE TEMPERATURES OF THE CHEMICAL REACTIONS OF THE IRON STEPPED RECOVERY FROM HEMATITE WITH CO GAS AND GASIFICATION OF SOLID CARBON ACCORDING EXISTING FORMULAS AND BY STANDARD VALUES OF ENTHALPY AND ENTROPY OF SUBSTANCES

The article presents the results of a thermodynamic assessment of the possibility of chemical reactions of the stepped recovery of iron from hematite with a recovering gas CO, as well as the Bell-Boudoir chemical reaction. It has been established that for each of the indicated chemical reactions there is a certain temperature (called by the author as "boundary temperature"), up to or above which CO gas cannot be a recovering agent for lower iron oxide from higher or the metallic iron itself from wustite, as well as gasification of solid carbon; while the recovery of Fe3O4 from Fe2O3 is theoretically possible at any temperatures above 0 ° C, the recovery of FeO from Fe3O4 and the gasification of solid carbon are theoretically possible above certain temperatures (i.e. at elevated and high temperatures), and the recovery of iron from FeO is below a certain temperature (i.e. at low temperatures). The numerical values of the boundary temperatures for the reactions of iron recovery and its lower oxides, as well as the reaction of gasification of solid carbon are given; graphical dependences of the Gibbs free energy of the indicated chemical reactions on temperature are made according to the equations available in metallurgical literary sources, and according to the expressions derived in the article by the author.

Thermodynamic modeling of iron recovery processes

One of the promising directions in metallurgy is the use of iron-containing waste, such as converter production sludge, iron-containing concentrates, rolling scale, iron ore processing waste and others. Development of new resource-saving technologies using such waste requires preliminary research and accumulation of information in the field of iron recovery. The paper considers the processes of iron recovery from oxides under various conditions. The authors used the method of thermodynamic modeling based on the search for the entropy maximum. The thermodynamic modeling tool was TERRA software package created at the Bauman Moscow State Technical University. TERRA complex is designed to calculate the thermodynamic properties and composition of the phases of equilibrium state of arbitrary systems with chemical and phase transformations. Using this software package, studies of the processes of iron recovery by various reducing agents (carbon, manganese, and silicon) in model thermodynamic systems were carried out, and optimal conditions for temperature and consumption of reducing agents were determined. The paper presents the results of a study of processes in the metal-slag system in equilibrium. The analysis of the metal-slag system equilibrium state was carried out for the temperature range of 1773 - 1973 K with different amounts of slag. Boundaries of the areas of redox processes were determined and the influence of metal components on conditions for iron oxides recovery from slag to metal was evaluated. The dependences of the system equilibrium composition on temperature at different ratios of metal and slag were obtained, as well as the optimal conditions for iron recovery.

A Combined Soda Sintering and Microwave Reductive Roasting Process of Bauxite Residue for Iron Recovery

In this study an integrated process is presented as a suitable method to transform Fe3+ oxides present in bauxite residue into magnetic oxides and metallic iron through a microwave roasting reduction, avoiding the formation of hercynite (FeAl2O4). In the first step, all the alumina phases were transformed into sodium aluminates by adding sodium carbonate as a flux to BR and then leached out through alkali-leaching to recover alumina. Subsequently, the leaching residue was mixed with carbon and roasted by using a microwave furnace at the optimum conditions. The iron oxide present in the sinter was converted into metallic iron (98%). In addition, hercynite was not detected. The produced cinder was subjected to a wet high intensity magnetic separation process to separate iron from the other elements.

Recovery of iron and phosphorus removal from Gara Djebilet iron ore (Algeria)

Purpose. This research aims to promote the assay of iron and reduce the phosphorus grade of the final DRI. Methodology. A high-phosphorus oolitic iron ore from Gara Djebilet deposit underwent the procedure of coal-based direct reduction (coal-based DR) followed by wet low-intensity magnetic separation (WLIMS). The effects of temperature, periods of time and Na2SO4 dosage on phosphorus removal, metallisation degree and iron recovery rate were tried and optimised. Furthermore, phase changes in iron oxides and the distributing features of phosphorus in both reduced and magnetic materials were investigated as well. Findings. The appropriate addition of sodium sulfate improves the Fe-P separation during the coal-based DR of Gara Djebilet mixed pellets. Originality. Using additives of CaO and sodium sulfate during the coal-based DR-magnetic separation of mixed pellets sourced from Gara Djebilet deposit. Practical value. The results reveal that a final direct reduced powder (DRI) assaying 96 wt% Fe and 0.16 wt% P at a recovery rate of 97.72% was obtained when the ore-coal-CaO mixed pellets were reduced in the presence of 5 wt% Na2SO4 at 1250 C for 30 min. Thus, the coal-based DR could be used as an alternative to the blast furnace (BF) route in the steelmaking industry from refractory iron ores.