Due to the different amount, type and occurrence of impurities contained in quartz sand and different product quality requirements, a single quartz mining process may not be able to achieve the purpose of quartz sand purification, and sometimes the several quartz mining processes are required to form a combined beneficiation process. The common quartz mining processes are as follows:
1. Scrubbing-classifying– desliming process
In the weathering sedimentary and mineralization process of quartz sand, a large number of clayey minerals and iron form the cementation or adhesion minerals on the surface of the quartz. It is a common quartz mining process to adopt the scrubbing-classifying- desliming process to remove clay impurity minerals, argillaceous iron, and some thin-film iron. This quartz mining process is generally used as a pretreatment process before raw ore separation, which can effectively remove the argillaceous impurities.
2. Scrubbing-desliming-magnetic separation process
Generally, the common impurity minerals in the quartz (such as the limonite, tourmaline, hematite and biotite and other weakly magnetic minerals, magnetite and other strongly magnetic minerals) can only be removed by a magnetic separation process. In the actual production, the wet strong magnetic separator with 13000 Oe of magnetic field strength is mostly used for separation.
3. Rod milling washing – desliming – magnetic separation – flotation – acid leaching process
After the washing, magnetic separation and flotation separation of raw ore, the impurity mineral particles with low occurrence (including monomer, aggregate) are basically cleared, the silica purity can generally reach 99.5%-99.9%, basically can meet the majority of industrial requirements of quartz sand. However, in order to obtain the ultra-high purity quartz, the impurities continuously adhere to the surface of quartz particles in the form of spots and inclusions must be treated with acid leaching. The mixed acid leaching with different concentrations and matching must be carried out according to the different requirements of impurity minerals (Fe, AL, Ti, Cr) in the different industries. The high purity quartz with silica content of 99.99% or more can be obtained by the rod milling washing – desliming – magnetic separation – flotation – acid leaching process.
4. Add reagents for high-efficiency and strong scrubbing – classifying and desliming – magnetic separation process
By improving the structure of existing mineral scrubber, optimizing the technical parameters, add reagents for high-efficiency and strong scrubbing – classifying and desliming can remove more than 80% of impurity iron and aluminum ore. The magnetic separation process is mainly to remove the iron-contained impurity minerals. Through this quartz mining process, the high-quality refined quartz sand (silicon dioxide ≥99.8%, iron oxide ≤0.023%, aluminum oxide ≤0.05%, titanium dioxide ≤0.02%) can be obtained, which has reached the requirements of primary optical glass sand, and the yield of fine quartz sand is as high as 73%, while the yield of rod friction washing is only 49%. After further flotation and acid leaching process, the high-purity quartz (silica ≥99.9%, ferric oxide ≤0.005%, aluminum oxide ≤0.05%, titanium dioxide ≤0.02%) can be obtained. This quartz mining process overcomes the shortcomings of secondary contamination of iron caused by rod friction washing and low yield.
In the practice, the selection of the quartz mining processes and flows is often determined based on the nature of quartz stone, conditions of the quartz processing plant, investment budget. It is suggested to choose a single or joint quartz mining process through the mineral processing test report, thus striving for the ideal technical and economic benefits.