The Role of Gangue Mineralogy on Flowsheet Development in Fluorite Processing

Fluorite, CaF2, is considered a strategically important mineral as it is a raw material for many strategic industries. Froth flotation is reported to be the most efficient and economically viable process for the production of an acid-grade product with a CaF2 content of at least 97%. Selective flotation of fluorite from gangue minerals, e.g., calcite and barite, is challenging because these minerals have similar physicochemical properties. This study employed batch flotation tests coupled with mineralogical analysis to design suitable customised flowsheets and efficiently optimised reagent regimes for optimum production of acid-grade fluorite concentrate from two different fluorite ores by the froth flotation process. The effect of pulp temperature on fluorite flotation was investigated in this study with the objective of lowering pulp temperatures in fluorite flotation. The results showed that an acid-grade CaF2 concentrate could be obtained from the flotation of both ores at ambient pulp temperatures. This eliminates the requirement for high-temperature pulp treatment, which would result in a significant reduction in thermal energy costs. This study showed that an understanding of gangue mineralogy is key to process optimisation for acid-grade CaF2 production. Although an acid-grade CaF2 concentrate could be produced from both ores, the flowsheets and reagent regimes were markedly different. For instance, the production of an acid-grade CaF2 product from a high quartz and calcite ore was achieved by employing a simple rougher–multiple cleaner flotation circuit using tannin and sodium silicate as calcite and quartz depressants, respectively. On the other hand, the production of an acid-grade CaF2 product from the flotation of the pyritic ore required a pre-sulphide flotation stage for upfront sulphur removal and the use of a sulphide depressant. Multiple stages of cleaning were required for improved selectivity in the flotation of both ores.

Evaluation of the influence of the dispersion-sludge characteristics of the pulp on the beneficiation indicators of technogenic fluorite-containing tailings

The article provides an assessment of the technological features of mature tailings from the processing of finely disseminated fluoritecontaining raw materials of the Yaroslavkaya Mining Company. The prospects for their secondary processing are considered. It has been established that the waste stored in various sectors of the enterprise’s tailings contain from 13 to 23% fluorite, 12-14% calcite. The characteristic is given to the technological features of raw materials. The fluorite grains present in the technogenic tailings are characterized by the presence of thin inclusions and veins of silicate minerals. An obstacle to the selective separation of minerals by the flotation method is the shielding coatings of the surface zone of mineral particles, formed from contact with reagents at the stage of primary ore processing and in the process of interaction with the water-air environment in the tailing dump. The ways of increasing the contrast of the adsorption properties of minerals are proposed. Important factors influencing the process of mineral selection, allowing to influence the quality characteristics of flotation of refractory secondary raw materials is fine grinding of the material in combination with a high degree of dilution of the pulp. The possibility of extracting concentrates with a CaF2 content of 95.2-95.6% with the recovery of fluorite in them of 57-60.7% is shown. The introduction of inter-cycle regrind of foam products into the operation scheme allows to reduce the content of silicone dioxide in concentrates to 0.98%, which meets the requirements of consumers.

Effect of CaF2 on the Viscosity and Microstructure of CaO–SiO2–Al2O3 Based Continuous Casting Mold Flux

In this study, a CaO–SiO2–Al2O3-based continuous casting mold flux was designed using the FactSage thermodynamics software to determine the composition range of CaF2. The viscosity characteristics of the mold flux were determined using a rotating viscometer. The results show that the constant temperature viscosity at 1300 °C decreases gradually as CaF2 content is increased from 3% to 11% in the CaO–SiO2–Al2O3-based slag. Viscosity is reduced from 0.854 to 0.241 Pa·s, viscous the flow activation energy is reduced from 157.74 to 114.34 kJ·mol−1, and the break temperature is reduced from 1280 to 1180 °C. Furthermore, when the CaF2 content is increased from 3% to 11%, the number of nonbridging fluorine bonds (Al–F structure and Si–F structure) in the melt increases to 287, the number of bridging fluorine bonds (Al–F–Al structure, Si–F–Si structure, and Si–F–Si structure) is only 17, and the network rupture of fluorine ions in the system is larger than the network formation. Consequently, both the degree of polymerization and viscosity are reduced.

THEORETICAL JUSTIFICATION AND DEVELOPMENT OF THE SLAG MODE FOR TREATMENT OF WHEEL STEEL ON THE INSTALLATION OF A BUCKET-OVEN WITH A PURPOSE TO REDUCE THE SPECIFIC ELECTRIC ENERGY

Purpose. Management of the formation of oxide fluoride slag at the stage of out-furnace treatment of the wheel metal. Methodology. Investigations of the energy technological regimes of out-of-furnace treatment of wheel steel were performed by analyzing the parameters of the basic metal processing technology at the ladle furnace. Results. The optimal input mode of the fluorspar is established when the ladle slag is formed at the ladle furnace installation. Scientific novelty. Analytical studies confirmed the absence in the structure of oxide fluoride slag structures containing fluorspar. Its role in the formation of ladle slag is defined as a depolymerization unit of spatial silica-oxygen groups and, as a consequence, an increase in the flowability of the melt while simultaneously increasing the oxidative potential of the slag. Practical significance. The results of the study determine the limits of the CaF2 content in the ladle slag and allow a 30–35% reduction in the power consumption during slag formation at the ladle furnace. Key words: Wheeled steel, electric arc furnace, metal intermediate, deoxidizing agents, alloying, slag-forming materials, fluorspar, ladle-furnace installation, energy saving.

Research on Properties of AlN-Mo Composite Ceramic

With CaF2 and CaCO3 as sintering additives, AlN-Mo composite was prepared using hot pressed sintering technique. The phase composition and morphology of AlN-Mo composite ceramics were analyzed using XRD and SEM, respectively. The experimental results show that when CaF2 and CaCO3 additives is in a range of 1~3wt%, the thermal conductivity AlN-Mo composites increases with increasing of the CaF2 content; With the increasing of CaCO3 content, first increases and then decreases. Sintering additives in a certain type and content, the thermal conductivity of AlN-Mo composite ceramics with 20 vol% Mo is higher than containing 18 vol% Mo. The dielectrical property of AlN-Mo composite ceramics was also discussed. The addition of CaF2 can decrease the dielectric constant of AlN-Mo composite ceramics.

Effect of calcium fluoride on sintering behavior of SiO2-CaO-Na2O-MgO glass-ceramic system

The crystallization characteristics of glasses based on the SiO2-CaO-Na2O-MgO (SCNM) system containing calcium fluoride (CaF2) have been investigated by differential thermal analysis (DTA), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The partial replacement of CaO by CaF2 in the studied glass-ceramics led to the development of different crystalline phase assemblages, including wollastonite and diopside using various heat-treatment processes. With the increase of CaF2 content, the crystallization temperature of the glass and the strength of the crystallization peak temperature decreases. Addition of CaF2 up to 6.0 mol%, as expected, improved the sinterability. This sample reached to maximum density by sintering at 950 ?C.

Study on Properties of Al2O3 -CaO-SiO2-CaF2 Slag System

Liquidus temperature, electrical conductivity and phase composition of Al2O3－CaO－SiO2－CaF2 System were studied. The results showed that the liquidus temperature of the slag decreased with increasing CaF2 content, and its electrical conductivity increased with increasing CaF2 content and temperature. When the content of CaF2 is 20%, the liquidus temperature is 1469°C. When the contents of CaF2 is 10%，its main phase compositions are composed of Ca5Al6O14、Al2Ca3(SiO4)3、Al2(SiF6)3 and Ca3Al10O18. Ca2AlF7、Ca2Al3O6F becomes more and more with increasing the content CaF2 because of F1- replacing O2- in molten slag.

An Analysis on Formation of ANF-6 Electroslag Fluxes Skin of Electroslag Remelting Ingot

The analysis on ingredient and petrographic examination of 5mm thickness ANF-6 electroslag fluxes (70% CaF2 + 30% Al2O3) skin formed during 0.45C steel 260 kg ingot remelting by electroslag remelting furnace with 160 kW, Φ100 mm × 350 mm mould indicates that the lamination phenomenon of fluxes is observed, and the Al2O3 content in fluxes skin near mould side and near electroslag ingot side is higher 69.24%-75.62%, and the CaF2 content is 21.46%-28.36%, where at skin center 3 mm location, the Al2O3 content in fluxes skin is only 15.84% and the CaF2 content is 81.06%. The solidification mechanism of “ring shaped miniature fluxes pool” formed at upper edge of remelted ingot is advanced in this paper, and the surface quality of ingot by using large over-cooling and low melting-point fluxes is higher than that by using low over-cooling and high melting-point fluxes.