Application of Reagents Throughout the Fluorite Flotation Process

As a core strategic mineral in the fluorine chemical industry, fluorite is associated with a wide variety of gangue minerals. Quartz, calcite, barite, sulphide minerals and clay minerals can all interfere with the purification of fluorite; it is difficult to consistently produce high-grade fluorite concentrate relying solely on a single process or a single reagent. In actual production, a comprehensive mineral processing flow works in tandem with a tailored reagent system. Through segmented process control and precise reagent adjustment, efficient separation of fluorite from various gangue minerals is achieved. The following section explains the functions of the reagents and the principles of their synergy in each stage of the full process.

The complete fluorite beneficiation process is divided into five core stages: pre-treatment, roughing, multi-stage scavenging, re-treatment of intermediate products, and tailings disposal. Each stage is matched with a dedicated combination of reagents, each performing its specific role in controlling the separation process. Upon arrival at the plant, the ore first undergoes pre-treatment involving crushing and staged grinding. As fluorite is brittle, over-grinding can produce fine slime that impairs flotation; therefore, a staged grinding process is adopted, involving coarse grinding for liberation followed by re-grinding of the coarse concentrate. Once grinding is complete, the slurry enters the slurry adjustment tank, where a slurry conditioner is first added to establish a suitable flotation environment. Sodium carbonate is the primary base modifier, stabilising the slurry within a weakly alkaline range and precipitating harmful free calcium and magnesium ions from the slurry to ensure sufficient ionisation of the subsequent collectors; for high-silt ore, dispersants are added simultaneously to break up agglomerated clay particles, thereby preventing the flocculation of fluorite particles by clay slime and the resulting decline in recovery rates.

Once slurry conditioning is complete, the process proceeds to the roughing stage, which relies primarily on collectors to selectively capture fluorite minerals. Traditional oleic acid-based collectors offer good value for money but have poor low-temperature performance; modified fatty acids and new Gemini synthetic collectors are more widely used. The collector molecules adsorb directionally onto the fluorite surface to form a hydrophobic film, enabling the fluorite to adhere to air bubbles and float to the surface, whilst having virtually no collecting effect on quartz or carbonate gangue, thereby significantly reducing the simultaneous flotation of impurities. During the roughing stage, a basic inhibitor is added simultaneously; modified water glass forms a hydrophilic colloidal layer on the surface of quartz, inhibiting the flotation of silicate gangue and achieving preliminary separation of fluorite from siliceous impurities. The roughing foam constitutes the rough concentrate, whilst the bottom tailings are fed into the scavenging stage, where a small amount of collector is added to recover residual fluorite and minimise metal loss.

As the impurity content in the rough concentrate is relatively high, it must be sent to a multi-stage fine selection process for gradual purification; fine selection is the key process in which the reagents play a central role. For calcium-bearing associated gangue minerals such as calcite and dolomite, water glass alone has limited inhibitory effect; it must be combined with a compound organic inhibitor comprising tannin, sodium humate and aluminium salts. The functional groups of these reagents firmly adsorb onto the surface of carbonate minerals, forming a stable hydrated film that blocks their flotation pathways, whilst having minimal impact on fluorite; if the ore contains barite, tannin is replaced with tannic acid - metal salt composite inhibitors to selectively suppress barite and achieve priority separation of fluorite; for sulphide-type fluorite containing pyrite and galena, a pre-desulphurisation stage is added, utilising specialised collectors for sulphide ores to remove sulphide impurities in advance, thereby preventing sulphur from entering the fluorite concentrate and reducing product grade.

The concentrate and sweep middlings generated during the process must not be discarded directly. Depending on the ore’s distribution characteristics, three recycling schemes are selected: for fine-grained, difficult-to-process ores, a middlings regrinding process is employed; after re-liberating mineral intergrowths, re-selection is carried out using reduced chemical dosages; for conventional ores, sequential return is adopted, with the middlings returned to the previous enrichment stage to stabilise the froth separation environment; for low-impurity ores, the middlings are centrally returned to the roughing stage to simplify the equipment flow. Following regrinding of the middlings, the reagent ratios are fine-tuned to reduce the dosage of inhibitors, thereby preventing excessive inhibition of fluorite caused by multiple recycling cycles.

The entire process can be flexibly extended to incorporate combined gravity and flotation or gravity and magnetic flotation processes. Fluorite containing iron is first subjected to magnetic separation to remove magnetic impurities, whilst coarse-grained fluorite undergoes gravity separation to pre-discharge tailings and reduce the flotation load; for high-grade acid-grade fluorite, a chemical purification stage may be added after flotation to deeply remove carbonate impurities using weak acid reagents. The entire process relies on segmented control of pulp particle size and concentration, combined with the synergistic action of adjusters, collectors and inhibitors. The dosage and ratios of reagents are dynamically adjusted according to different process stages and types of ore impurities. The process ensures thorough mineral liberation and enables precise selective separation through the reagents; these two factors complement each other, simultaneously enhancing the grade of the fluorspar concentrate and the overall recovery rate, whilst balancing production economics with the requirements for environmentally sound tailings management.