Papers by Keyword: Ferrous Metallurgy

Abstract: The paper investigates the effect of high-temperature roasting and cooling modes of roasted iron ore pellets on their strength and porosity. These characteristics depend on the initial iron ore raw materials properties, the parameters of the raw pellets, the firing temperature, the holding time at this temperature, the heating and cooling rate, and take into account the change in these indicators in connection with the chemical and mineralogical compositions of the pellets. It has been established that the strength of iron ore pellets obtained at the optimum firing temperature depends on the characteristics of the initial finely dispersed iron ore raw material. The relationship between the content of draw rock and the strength of calcined pellets has been revealed. A significant influence of the raw pellets porosity on the strength of the calcined pellets was found. It is shown that the crushing strength of pellets cooled in air is higher than the strength of pellets cooled with water, and a decrease in the final cooling temperature leads to an increase in the strength of the pellets. It is substantiated that the heating rate should not exceed the rate of gas diffusion, and with a decrease in the size of finely dispersed iron ore raw materials, the shrinkage of the pellet layer increases during heating. It is shown that shrinkage appears at temperatures lower than the optimal calcining temperature and insignificantly affects the strength of the pellets. The results obtained can be used to substantiate resource-and-energy efficient operating modes of horizontal-grate machines in ferrous metallurgy.

Abstract: The research objective is studying the effect of tailing slurry of chromite ore beneficiation on the phase composition and frost resistance of ceramic bricks obtained based on low-melting clay. For the study, two compositions were taken, % wt.: 1) the optimal composition ─ low-melting clay of the Ilek deposit - 70, tailing slurry of chromite ore beneficiation, 2) the reference composition ─ low-melting clay of the Ilek deposit - 100. Raw materials were crushed to pass through a sieve No. 1.0 mm; then, the components were thoroughly mixed. The bricks were prepared by melting at a batch moisture content of 22 %. The mold bricks were dried to a residual moisture content of 5 % max. The dried bricks were fired at temperatures, ^оС: 950 (the glass phase emergence), and 1,050 (the final brick firing temperature). The increased content of iron oxide (Fe₂O₃=12.3 %) and alkali oxides (R₂O=3.2 %) in the tailing slurry of chromite ore beneficiation contributed to the liquid phase emergence at 950 ^оС. Colorless, yellowish, and brown glasses with refractive indices N within 1.50-1.54, forming as a result of melting of spars and mixed-layer clayey formations, were observed under the microscope in the studied prototypes of composition No. 1 at a firing temperature of 950 °C. In the composition No. 2, a liquid phase also emerges, but in smaller quantities. Adding tailing slurry of chromite ore beneficiation to ceramic masses contributes to the formation of anorthite and glass phase in prototypes based on low-melting clay at a firing temperature of 950 °C. An increase in the firing temperature to 1,050 °C increases the content of the glass phase and anorthite, which significantly improves the frost resistance of ceramic bricks.

Abstract: In this paper the analysis of the processes for spontaneous decay of slags from the production of refined ferroalloy grades is performed. It is shown that the main reason for the decay is the formation of a dicalcium silicate in highly basic melts with CaO / SiO₂ ratio of 1.5-3.1. Based on the performed studies, three main promising directions for the stabilization of slags of ferroalloy production have been formed. First direction is the replacement of the calcium cation (or transformation) in a dicalcium silicate, for example, with the magnesium cation or the production of non-decaying compounds of the gehlenite type (2CaO·Al₂O₃·SiO₂), mainly due to the application of phase composition peculiarities of the waste rock for ferroalloy raw materials. Second direction is the reduction of the dicalcium silicate content with a decrease in the ratio of CaO / SiO₂ in the slag less than 1.4, due to the separation of the silicothermic reduction process into two stages, obtaining in the first stage a low-basic (CaO / SiO₂ = 1.3-1.4) non-decaying tailing slag, and on the second one - highly basic return slag (1.8-1.9), which is used in the first stage of this technological chain. The third direction is the replacement of the SiO anion of dicalcium silicate with other anions, for example, ВО by means of small additions of calcium borate, colemanite, etc. A possibility for stabilization of ferroalloy production slags with obtaining of construction crushed stone corresponding to the requirements of TU 0798-69-00186499-2014 "Crushed stone and sand from ferroalloy slags. Technical conditions», is shown experimentally.

Abstract: In recent years, the steel industry is in decline. To reduce environmental pollution, increase corporate profits and promote the sustainable development of China's steel industry, developing steel metallurgical slags comprehensive utilization has a very important significance. This article describe the present situation and problems in China's steel metallurgy slag comprehensive utilization, and reach the conclusion that the present method should be improved and the new method of comprehensive utilization should be further developed.