Study on the reducibility of iron ore pellets at high temperature

The behaviour of iron ore pellets in a blast furnace must be considered to improve ironmaking operations, especially when a large amount of the pellets is used. This study presents the reduction degree, mineralogical composition, and morphology of the pellet reduced in a gas mixture of 60% CO and 40% Ar at temperatures between 900 and 1,100oC. The pellet was prepared from iron ore from the Cao Bang province, Vietnam, by rotary drum. The obtained results showed that the reduction degree of the pellet increased with increasing reduction time and temperature. The activation energy of the reducing reaction was calculated to be 63.2 kJ/mol, which indicated that reduction occurred more easily in the present condition. X-ray diffraction (XRD) results revealed mineralogical phases such as hematite (Fe2O3), magnetite (Fe3O4), wüstite (FeO), metallic iron (Fe), and fayalite (Fe2SiO4) existing in the pellets when reduced for different times and temperatures. Fe and Fe2SiO4 were found to be the majority in the pellet that was reduced for 90 min at 1,100oC. Scanning electron microscopy (SEM) observations suggested the formation of a liquid phase, e.g., Fe2SiO4, which retarded the reducing reaction because it hindered the diffusion of gas flow inside the pellet. This phenomenon is essential to blast furnace ironmaking because pellets must be completely reduced before they move down to the liquid zone.

PRODUCTION OF IRON ORE PELLETS BY UTILIZATION OF SUNFLOWER HUSKS

Steel production is the most dynamic industry and one of the key sectors for the development of the global economy. The growing production of iron ore increases the need for its beneficiation and granulating for subsequent use in the production of iron and steel. As a result, the number of CO2 emissions and harmful substances increases, which negatively affects both society and the environment. It is important to study the use of biomass for the production of iron ore pellets. Lignocellulosic biomass is a renewable and sustainable source of heat and energy that can mitigate climate change. The efficiency of using sunflower husks on the combined machine “straight grate - rotary kiln - annular cooler” to partially replace natural gas in the production of iron ore pellets has been studied. The influences of alternative fuel use on technological indicators of the process and quality of iron ore pellets have been analyzed. It was found that the combustion of sunflower husks generates enough heat to obtain iron ore pellets with good strength. The main indicators of the quality of iron ore pellets remain at the same level as the iron ore pellet quality when using natural gas.

Comparative analysis of straight grate machines and combined facilities grate-tubetype kiln-cooler for selection technologies of pellets production

At present, mainly straight grate machines (SGM) and combined facilities grate-tube-type kiln-cooler (GKC) are used for heat-strengthening induration of iron ore pellets. Their total share in the produced iron ore pellets in the world accounts for 93%, of which SGM takes 60% and GKC – 33%, which speaks about high efficiency of both methods of induration. At the same time, when making decision on construction a pelletizing plant, a question of selection of most effective technology of iron ore pellets production by SGM and GKC often arises. Results of comparative analysis of efficiency of technologies of iron ore pellets production by SGM and GKC presented. Features of various ore types pellets induration considered as well as possibilities of ensuring the required quality of finished pellets at application for induration SGM and GKC. Data on maximum productivity of the considered induration facilities, amount of dust, fines formation, emissions of harmful substances into environment and electric energy consumption presented. Importance of a possibility of accounting of fuel type selection, of heat expenses for heat treatment, of expenses for maintenance, capital and operation costs were noted. It was shown that choice of a particular variant of technology should be done at the stage of elaboration feasibility study accounting existing experience of facilities running, availability of fuel types, cost of energy resources, climate zone and assembling solutions.

Workers’ Health Risk Factors in the Production of Iron Ore Pellets

Introduction. The labor of workers of the main occupations in the mining industry is characterized by a combined effect of occupational risk factors, which can be further aggravated by adverse environmental conditions. Objective: to study working conditions of employees in the mining industry. Materials and methods. We conducted a hygienic assessment of the technological process of manufacturing oxidized fluxed and non-fluxed pellets during the extraction of iron ore by surface mining and its further processing into high-quality raw materials for ferrous metallurgy, and a study of harmful physical and chemical factors of the working environment. Results. We established that a sinter machine operator (Class 3.3 hazard working conditions in the summer time), an operator of the agglomeration and firing furnace (Сlass 3.4), and a bunker operator in the shop for fired pellets (Сlass 3.3) work in hot occupational environment. The average value of the intensity of thermal radiation over the irradiation period (1.35 hours) for agglomeration and firing furnace operators was 356.2 W/m2 or 2–2.5 times higher than the maximum permissible level. Increased noise levels (Class 3.2) were measured at the workplaces of conveyor, sinter and furnace operators (14.8 % and 9.25 %). At individual workplaces of sintering machine operators, we registered elevated dust concentrations (Class 3.1), noise levels (Classes 3.1 and 3.2), sulfur dioxide concentrations (Class 3.1), and the sum of irritant chemicals (Classes 3.1 and 3.2 by excess of the maximum permissible concentration (MPC)) were recorded. At workplaces and in the service area of the furnaces at agglomeration and roasting, the maximum permissible level was exceeded for dust (Class 3.1), noise (Classes 3.1 and 3.2), sulfur dioxide (Class 3.1), and the sum of irritant chemicals (Classes 3.1 and 3.2). Conclusions: The hygienic analysis of the technological process of manufacturing iron ore pellets at the pelletizing plant indicates the presence of sources and conditions forming adverse occupational factors posing health risks for workers. In order to address occupational health and safety issues, it is necessary to introduce comprehensive measures to prevent health disorders in the working population.

Use of local fuel-produced syngas for iron ore pelletizing

Iron ore pellets are important sources of iron for steel manufacturing. A high temperature process of induration finalizes pelletizing and typically consumes vast amounts of heat. While local resources can include iron ore, there can be a lack of local natural gas normally used for ore processing. A solution is use of abundant local fuel-produced syngas. We have performed this research based on mathematical modeling. A possibility of use of local coal-produced syngas for iron ore pelletizing has been proven what means creating a novel way for active and cost-efficient local ore pellet manufacturing. Gasification of induration machines does not require major equipment renovation. We have also analyzed major benefits and risks of this new technology.