Effect of Particle Size Classification on Purification of Vein Quartz

Crystal used to be an important raw material for the preparation of high-purity quartz sand, but with the depletion of crystal resources, the demand for the production of high-purity quartz sand with quartz ore instead of crystal is becoming more and more urgent. High quality vein quartz ore is expected to replace the crystal, become the raw material for the production of high purity quartz sand. At present, the proven reserves of vein quartz in China are 0.05 billion t, which has the potential to be developed into high-quality quartz raw materials.
The main impurities in quartz such as Fe, Ca, Al, K, Na and other elements often reach thousands of g/g. When the content of K and Na elements in the high-purity quartz crucible used for the growth of monocrystalline silicon is too high, the softening temperature of the crucible will be too low to pull the crystal, and when the Al element is too high, it will affect the purity of the pull monocrystalline silicon. Quartz raw materials for producing TFT-LCD substrates have high requirements on alkali metal oxides, and at the same time, they are required to have few defects such as bumps and bubbles in the glass during processing. Therefore, the production of such glass also has higher requirements on the inclusion content in the quartz raw materials. How to effectively remove these impurities has become the difficulty of producing high quality quartz sand.
At present, domestic and foreign scholars generally follow the principle of matching mineral processing and deep purification of vein quartz ore. After crushing and grinding of vein quartz ore, traditional mineral processing methods such as gravity separation, magnetic separation and flotation, in-depth treatment of impurities in quartz particles, namely roasting and water quenching, and acid leaching-based wet leaching process can also be used to purify quartz raw materials.
Considering the differences in the distribution of impurities between quartz particles and the occurrence of gangue minerals, and the differences in the quality of quartz obtained by different treatment conditions, it is necessary to classify the vein quartz and then purify it. The classification-separation process test was carried out with low-quality vein quartz from a certain area of Gansu Province as raw material, and the crushed raw ore was screened-ground-screened to obtain four samples, and then the four samples were subjected to high-gradient magnetic separation and reverse flotation respectively, and the effect of classification and separation on each classification product and the quality difference of each quartz were evaluated by the content of Fe, Al and other elements, to investigate the separation effect of vein quartz classification beneficiation purification and the quality and washability of each grain grade concentrate, the results show that:

1) The four samples of (-0.60+0.10)mm, (-0.10+0.045)mm in the raw ore and (-0.60+0.10)mm and (-0.10+0.045)mm obtained by grinding are respectively subjected to magnetic separation and flotation to obtain better purification effect. The quality of the four concentrates is quite different. The best is the (-0.60+0.10)mm grade produced by grinding, with SiO2 content of 99.67, Al2O3 content of 2271.92 μg/g and Fe2O3 content of 38.64 μg/g. The difference is the (-0.10+0.045)mm grade in the raw ore, with SiO2 content of 99.62 and Al2O3 content of 2546.83 μg/g, the Fe2O3 content was 70.26 μg/g.

2) The products of different grain fractions of vein quartz ore have differences in quality. The (-0.60 0.10)mm grade samples produced from raw ore and grinding are dominated by large quartz particles, while the (-0.10 0.045)mm grade samples are dominated by crushed large quartz particles and primary fine quartz particles. The fine-grained mica aggregate dissociates into the fine-grained fraction to increase the aluminum content. Therefore, based on the conclusion of process mineralogy, it is necessary to take grading and sorting for different grain grades of vein quartz, and the results of purification test show that the effect of grading and sorting is remarkable.