Carbonate-fluorite ore dressing technology

Carbonate-type fluorite ore is mainly composed of calcium fluoride, usually coexisting with carbonate minerals such as calcite and dolomite. The characteristics of this type of ore are its complex mineral combination and low fluorite grade. The fluorite particles in the ore vary in size, ranging from fine to coarse, and are often accompanied by other valuable associated minerals such as barite and quartz. The dressing technology for carbonate-type fluorite ore usually includes flotation, gravity separation, magnetic separation and chemical separation.

1. Flotation of carbonate fluorite

Positive flotation: Utilizing the difference in wettability of the mineral surface, by adding a specific collector, the fluorite surface is made hydrophobic and attached to the bubbles, and separated from other minerals. For carbonate-fluorite ores, fatty acid collectors such as oleic acid and sodium oleate are generally used, which can selectively adsorb on the surface of fluorite to make it floatable. Generally, the ore is first crushed and ground to a suitable particle size to fully dissociate the fluorite from the gangue minerals. Then add a regulator, such as sodium carbonate, to the pulp to adjust the pH value of the pulp, then add a collector and a frother, let air in to form bubbles, and the fluorite particles attach to the bubbles and float to the surface of the pulp. Scrape off the foam to get the fluorite concentrate.

Reverse flotation: is to make the surface of the gangue mineral hydrophobic and float, while leaving the fluorite in the pulp. It is often used to treat ores with a high carbonate content. By adding collectors that can selectively make carbonate minerals hydrophobic, such as amine collectors, gangue minerals such as carbonates are floated to separate fluorite from gangue. Similarly, crushing and grinding operations are carried out first, and then inhibitors are added to the pulp to inhibit the floatability of fluorite. Then collectors and frothers for gangue minerals are added to make the gangue minerals float, and the remaining pulp is the fluorite concentrate.

2. Carbonate rock type fluorite ore gravity separation method

The gravity separation of carbonate rock type fluorite ore is based on the density difference between fluorite and gangue minerals such as carbonates. The density of fluorite is generally around 3.18g/cm³, while the density of carbonate minerals is relatively small. The gravity field generated by the gravity separation equipment makes minerals of different densities produce different sedimentation speeds and trajectories during movement, thereby achieving separation.

After crushing and grinding, the ore enters the jig or shaking table. Under the action of water flow, the denser fluorite particles settle to the lower layer, while the smaller carbonate and other gangue minerals remain in the upper layer or are washed away by the water flow, thus achieving the purpose of separation. Gravity separation is generally used to treat coarse-grained fluorite ores, and is often used as a pre-selection operation before flotation to discard some gangue minerals and improve the grade of the selected ore.

3. Magnetic separation of carbonate rock fluorite ore

Magnetic separation of carbonate rock fluorite ore uses the magnetic difference of minerals for separation. Although fluorite itself is a non-magnetic mineral, some associated minerals in the ore may be magnetic, such as iron minerals. The magnetic field generated by the magnetic separation equipment makes the magnetic minerals adsorbed on the magnetic poles of the magnetic separation equipment, while non-magnetic minerals such as fluorite flow away with the slurry, thus achieving the separation of magnetic minerals and fluorite.

After crushing and grinding, the ore enters the magnetic separator for magnetic separation. According to the magnetic strength of the magnetic mineral, magnetic separators with different magnetic field strengths can be used. Weakly magnetic minerals require strong magnetic separators, while strongly magnetic minerals can use weak magnetic separators. Magnetic separation is usually used as an auxiliary mineral separation method to remove magnetic impurities in the ore and improve the quality of fluorite concentrate.

4. Chemical beneficiation of carbonate rock type fluorite

Acid leaching: is to use acid to react chemically with impurities such as carbonates in the ore to dissolve and remove them, thereby improving the grade of fluorite. Commonly used acids include hydrochloric acid and sulfuric acid. Mainly, carbonate minerals such as calcium carbonate can react with hydrochloric acid to produce water-soluble calcium chloride, while fluorite (CaF₂) does not react with hydrochloric acid, thereby achieving impurity removal. The general process is to crush and grind the ore, mix it with an acid solution in a certain proportion, and react under appropriate temperature and stirring conditions. After the reaction is completed, the acid-leached fluorite product is obtained through filtering, washing and other operations. The acid leaching method can effectively remove carbonate impurities in the ore, but it will produce a large amount of acidic wastewater, which needs to be treated to prevent environmental pollution.

Alkali fusion method: At high temperature, alkaline substances are used to react chemically with certain impurities in the ore to generate compounds soluble in water or acid, thereby separating them from fluorite. Generally, under the action of alkaline substances such as sodium hydroxide, impurities such as silicon dioxide in the ore can generate soluble substances such as sodium silicate. The process is to mix the ore and alkaline substances in a certain proportion and then smelt them in a high-temperature furnace. The smelted product is subjected to water quenching, leaching and other operations to dissolve the impurities in the solution, and the fluorite product is obtained through filtering, washing and other steps. The alkali fusion method has high requirements for equipment and high energy consumption, but it has a good beneficiation effect for some difficult-to-select fluorite ores.

The above is an introduction to the beneficiation method of carbonate rock fluorite. In actual production, suitable fluorite beneficiation process plans are usually designed based on the properties, grade, and particle size of the ore. If it is a complex and difficult-to-benefit fluorite, multiple beneficiation technologies are often used to form a combined beneficiation process to achieve suitable beneficiation indicators and improve the recovery rate and concentrate grade of fluorite.