Core Stages and Processes of Scheelite Flotation

The scheelite flotation process is generally divided into two core stages: roughing and cleaning. For some complex ores, a pretreatment stage is added. Each stage has a clear division of labor and works in concert to ultimately achieve efficient enrichment of scheelite.

(I) Pretreatment Stage

 Pretreatment is mainly for scheelite with complex mineral distribution and many impurities, aiming to create favorable conditions for subsequent flotation. Common pretreatment methods include desliming, desulfurization, and iron removal. For ores with severe mud formation, desliming removes fine mud to prevent it from covering the mineral surface and affecting the flotation effect. For ores containing sulfide minerals such as pyrite and pyrrhotite, desulfurization flotation is used to remove sulfide minerals in advance to prevent them from interfering with scheelite flotation. If the ore contains magnetic impurities, they can be removed in advance by magnetic separation to improve the purity of the ore entering the flotation process and reduce the reagent consumption and process load of subsequent flotation.

(II) Roughing Stage

 The core objective of the roughing stage is to maximize the recovery of scheelite from the ore while ensuring a high enrichment ratio. The key to this stage lies in the proper combination of modifiers, collectors, and frothers to create a suitable pulp environment.

Modifiers typically use a combination of sodium carbonate and water glass or lime and water glass. This not only regulates the pulp pH but also improves mineral surface activity, eliminates interference from harmful ions in flotation, and inhibits the floatability of some gangue minerals. Collectors are typically fatty acid-based or chelating agents. These agents react with calcium ions on the surface of scheelite to form a stable hydrophobic adsorption layer, enhancing the hydrophobicity of scheelite. Frothers are used to generate stable and suitable foam to carry the collected scheelite particles to the float, achieving initial separation of scheelite from tailings.

The roughing process can be optimized according to the ore type. For mixed scheelite and gangue ores, a specialized chelating collector combined with an activator can be used to achieve simultaneous flotation of both scheelite and gangue. For ores with a high calcium gangue content, the inhibitory effect of the modifier is enhanced to reduce the floatation of gangue minerals and improve the grade of the rough and concentrate.

(III) Cleaning Stage

The core task of the cleaning stage is to further improve the grade of the rough concentrate while ensuring the recovery rate, thereby obtaining qualified scheelite concentrate. Based on ore properties and economic costs, the cleaning process is mainly divided into two categories: heated flotation and ambient temperature flotation.

Heated flotation utilizes the difference in inhibition between scheelite and carbonate gangue minerals by water glass at specific temperatures to achieve separation. By heating the pulp to a suitable temperature and using sodium carbonate, water glass modifiers, and fatty acid collectors, it can effectively inhibit gangue minerals such as calcite and fluorite, significantly improving the grade of scheelite concentrate. This method is suitable for refractory scheelite that coexists with carbonate minerals and fluorite.

Ambient temperature flotation does not require heating the pulp and has advantages such as low energy consumption, simple operation, and environmental friendliness and economy. Among them, the 731 ambient temperature flotation method uses highly selective oxidized paraffin soap as a collector, combined with sodium carbonate and water glass, and is suitable for scheelite with quartz as the main gangue. The lime ambient temperature flotation method uses ions generated by the dissolution of lime to form a coating layer on the surface of calcium-containing gangue minerals, enhancing the hydrophilicity of the gangue minerals and improving the selective separation effect between scheelite and gangue. The beneficiation process usually adopts a multi-stage beneficiation mode, continuously removing gangue impurities by gradually optimizing the reagent dosage and stirring conditions, and finally obtaining high-grade scheelite concentrate.