How to Remove The Mica from Sand?
The physical sorting, gravity separation, flotation, or combination methods are generally used for removing mica from sand depending on the difference between the properties of mica and sand gravel. Due to the particularity of sand and gravel processing, physical sorting is a more reasonable choice. The principle of air-selected mica is simple and the cost is moderate, which is more practical for the sand and gravel processing system produced by the dry method. Mica sorting can be carried out by selecting appropriate wind separation equipment and wind separation process.
1. Crushing and screening
Mica minerals are still flaky after grinding, while other minerals are irregular granular. The separation of mica and sand is realized by screening with the help of the difference in the shape of the crushed products. Screening machinery generally adopts a trommel screen and vibrating screen. After the raw ore enters the screen surface, under the action of vibration, the small pieces of sand fall under the screen, while the flake mica remains on the screen surface to realize sorting.
2. Shaker reselection
According to the nature of the ore, mica is in the form of flakes, while other minerals are basically granular. Grind the raw ore to a certain mesh and place it on a shaker. The thin mica flakes can be enriched and stratified in the light mineral belt, while other minerals are enriched in the heavy mineral belt, so as to realize the sorting of mica.
Features: The process is simple and the selection effect is good. However, additional equipment such as a shaker is required, which consumes a lot of energy, consumes a lot of water, and occupies a large space.
3. Magnetic separation
Mica minerals such as biotite and lepidolite all contain iron and are weakly magnetic minerals. Such mica minerals can be sorted by magnetic separation. Experiments have shown that after the magnetic separation of mica, the mica content in the finished sand is greatly reduced, which can be controlled within 2%, which is in line with the standard for sand use. Moreover, the concrete produced by de-mica machine-made sand has better mixing performance.
Features: Iron-containing mica can be removed. The sand and gravel processing system need to conduct a chemical analysis on the properties of the sand and gravel ore and the mica minerals contained before considering the magnetic separation operation.
4. Wind selection
The air separation method is a gravity separation method with air as the separation medium. It has a wide range of adaptability and can separate ores with different densities, particle size, shape, type, and nature in the moving airflow. After the raw ore is crushed, when the minerals of the same particle size fall naturally by gravity, the wind resistance of the flaky mica is greater than that of the granular sand, and the falling speed is slower, so as to realize and separate.
Features: This method needs to be combined with methods such as sieving to obtain the effect of mica separation.
As a widely used beneficiation method, flotation mainly utilizes the difference in the physical and chemical properties of the mineral surface to selectively enrich one or several target materials at the three-phase interface of “solid, liquid, and gas”, so as to achieve waste material phase separation.
Due to the difference in the pH environment of the pulp, the types of collectors used in flotation are also different:
When the pulp pH is less than 6.0, cationic collectors are generally used.
When the pulp pH is>9.0, an anion-cation mixed collector is generally used.
Features: The flotation method is mainly used for the recovery of crushed mica and fine-grained mica in the sand and gravel industry, especially the mica resources in tailings. The flotation method has strict requirements on the PH value of the pulp, and a large number of chemical reagents such as regulators, collectors, and inhibitors need to be added. The flotation method has large water consumption, high cost, and difficult wastewater treatment.
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