Integrated study on obtaining oxide pellets from brown iron ore

Introduction. Currently, the main raw materials for the production of cast iron and steel at metallurgical plants are iron concentrates obtained from magnetite (ferrous) quartzites, titanium-magnetite, and skarn ores. The existing technologies for processing these types of ores, which mainly include separation processes based on magnetic properties, size, separating of equally falling grains, and surface wettability allow us to produce both ordinary iron concentrates and high quality ones. The use of such schemes in the processing of brown iron ore does not allow obtaining high rates of mineral concentration. One of the methods for processing this type of ore is a roasting-magnetic scheme, which allows converting weakly magnetic (non-magnetic) forms of iron into strongly magnetic ones. Research objective is to develop the mode of magnetizing roasting of brown iron ore, technology of concentrating of the burn-out product in order to obtain iron concentrate and oxide pellets. Methods of research. The duration of heat treatment of the charge consisting of iron ore from the Abail deposit and coal from the Ekibastuz deposit and the required mass fraction of solid carbon contained in the coal are determined. Technological studies of the roasted product were carried out in order to obtain a concentrate with a mass fraction of iron at least 67%. According to the developed technology, a batch of iron concentrate was developed in order to obtain and study raw and oxide pellets. Results. The modes of magnetizing roasting of brown iron ore from the Abail deposit and cooling of the roasted material have been developed. A scheme for mineral processing of the roasted material has been developed in order to obtain a concentrate with at least 67% of iron mass fraction. The process of obtaining strong raw and roasted pellets from iron concentrate is studied. Conclusions. The developed mode of magnetizing roasting of the charge consisting of coal and ore from the Abail deposit makes it possible to obtain a roasted product with a degree of magnetization of 93%. The using of desliming of the roasted product makes it possible to remove magnetic floccules from the processing that reduce the concentrate quality, and to obtain a concentrate with a mass fraction of iron of at least 67% in the last stage of magnetic separation. From the iron concentrate, it is possible to obtain oxidized pellets with a strength of at least 200 kg/pellet at temperature of pellets firing of 1325 °C.

Preparation, Sintering Behavior and Consolidation Mechanism of Vanadium-Titanium Magnetite Pellets

High-quality oxidized pellets are the basis to achieve high-efficiency utilization of vanadium–titanium magnetite (VTM) ores. Bentonite was used as a binder of VTM. The main phase composition of VTM is titanomagnetite and ilmenite. When the amount of bentonite is 1%, the compressive strength and dropping strength of VTM pellets can meet the requirements. To improve metallurgical properties, the pellets need to be roasted. The best conditions for roasting are as follows: calcination temperature of 1523 K and a calcination time of 20 min. The consolidation mechanism, phase transformation, and crystal structure transformation of VTM in the process of oxidation roasting are also explained.

Phase Transitions and Microstructural Changes During Oxidation and Reduction of a Weathered Ilmenite Concentrate

The present work aims to investigate the link between the oxidation and reduction of a weathered ilmenite concentrate in terms of phase transitions, microstructural changes, and element distribution. An ilmenite concentrate sample was pelletized and fired at 1000 °C in air, and as a result, the pellets were oxidized. The oxidized pellets were reduced by hydrogen gas at 1000 °C, which yielded almost complete metallization of the iron content of the pellets. The ore and the pellets were characterized in each step by XRD and SEM techniques, and distribution of elements and phases were investigated. Ilmenite, pseudorutile, and rutile were the main phases detected in the ilmenite concentrate sample, and depending on the weathering degree of the particles, different fractions of the phases were identified in their microstructure. It was found that irregular rutile grains dispersed in a pseudobrookite matrix is the morphology of the oxidized ilmenite phase. However, increasing microcracks and porosities were the only microstructural changes in the pseudorutile phase after oxidation in air. Studying the specific types of the ore particles and their oxidized and reduced forms indicated that the phase distribution in the ilmenite ore particles dictates the phase distribution in the oxidized and reduced ones. Results show that the morphology of the reduced particles includes a titanium (III) oxide matrix in which reduced iron globules are dispersed.

Effect of Incremental Utilization of Unground Sea Sand Ore on the Consolidation and Reduction Behavior of Vanadia–Titania Magnetite Pellets

In the iron and steel industry, improving the usage amount of New Zealand sea sand ore as a raw material for ironmaking can reduce the production costs of iron and steel enterprises to a certain extent. In this paper, New Zealand sea sand ore without any grinding pretreatment was used as a raw material, oxidized pellets were prepared by using a disc pelletizer, and the effect of sea sand ore on the performance of green pellets and the metallurgical properties of oxidized pellets was investigated. The effects of sea sand ore on the compressive strength, falling strength, compressive strength of oxidized pellets, and reduction performance were mainly investigated. X-Ray Diffraction (XRD) patterns and Scanning Electron Microscope (SEM) analysis methods were used to discuss the influence of sea sand ore on the microstructure of the pellets’ oxidation and reduction process. As the amount of sea sand ore used increased, the compressive strength of green pellets was gradually decreased, and the falling strength of green pellets and the compressive strength of oxidized pellets were gradually increased. When the amount of sea sand ore used was 40%, the reduction swelling index of pellets was 16.31%. The increase of sea sand ore used made the reduction of pellets suppressed and the reduction rate decreased. When the amount of sea sand ore used increased to 40%, the reduction degree of sea sand ore pellets was only 60.06%. The experimental results in this paper provide specific experimental data for the large-scale application of New Zealand sea sand ore in the blast furnace ironmaking process.

Effects of High Proportion Unground Sea Sand Ore on the Preparation Process and Reduction Performance of Oxidized Pellets

The New Zealand sea sand ore is a kind of vanadia–titania magnetite formed by erosion in the coastal zone. Because of its coarse particle size, smooth spherical particles, complex chemical composition, it has been added to sinter as an auxiliary material. Based on the principle of optimizing ore blending to strengthen advantages and weaken disadvantages, this paper used New Zealand sea sand raw ore that has not undergone any pretreatment as the main material and prepared it into oxidized pellets using a disc pelletizer and explored the influence of high-proportion unground sea sand ore on the preparation process and reduction performance of oxidized pellets. The influence of unground sea sand ore on the falling strength, compressive strength, reduction swelling index, and reduction degree of pellets was analyzed by the ICPAES, XRF, XRD, SEM-EDS, and other detection methods, and the change laws and influencing factors of oxidized pellets were analyzed. With the increase of the amount of unground sea sand ore used, the falling strength and compressive strength of the green pellets first decreased and then gradually increased, while the compressive strength of the oxidized pellets first increased and then decreased. At the same time, as the amount of sea sand ore used increased, the reduction process of pellets was restricted. The reduction swelling index and the reduction degree index generally show a downward trend. However, the compressive strength of the pellets gradually increased after reduction. Through the research on the pellet-forming performance and reduction properties of unground sea sand ore, it is shown that when the amount of unground sea sand ore used was 40%, it can still be used as raw material for blast furnace ironmaking. Thus, this research provided specific data support for iron and steel enterprises to improve the ratio of unground sea sand ore and reduce production cost.

Optimization of experimental conditions on preparation of oxidized pellets with New Zealand sea sand ore

In the iron and steel industry, improving the usage amount of New Zealand sea sand ore as a raw material for ironmaking can reduce the production costs of iron and steel enterprises to a certain extent. In this paper, the New Zealand sea sand ore without any grinding pretreatment was used as raw material, oxidized pellets were prepared by using a disc pelletizer, and the experimental conditions for preparing oxidized pellets were investigated and optimized. The effects of binder dosages, roasting temperature and roasting time on the properties of pellets were mainly investigated, and the effects of roasting temperature and roasting time on the microstructure of oxidized pellets was discussed by researching XRD patterns and SEM-EDS. With the increase of binder dosages, the drop strength of green pellets and the compressive strength of oxidized pellets were gradually increased. With the increase of roasting temperature and roasting time, the compressive strength of oxidized pellets increased gradually. When the amount of New Zealand sea sand ore was increased to 40–50%, the optimal process conditions for the preparation of oxidized pellets were as follows: the dosage of binder was 1.5%, the roasting temperature was 1200 °C, and the roasting time was 20 min.