Raw material selection technology of high purity quartz sand

High purity quartz is the general name of silica sand series products with purity of more than 99.9%. It is the material basis of high-end products in silicon industry. It is widely used in photovoltaic, electronic information, optical communication and electric light source industries. It plays an important role in new materials and new energy strategic emerging industries. At presnet, more and more sand washing plants are setup to produce high purity quartz sand.
Kinds of high purity quartz sand
According to the purity of SO2, high purity quartz sand can be divided into three types
Low end w (SO2) ≥ 99.9% (3N)
Middle end w (SO2) ≥ 99.99% (4N)
High end w (SO2) ≥ 99.998% (4N8)
According to the total amount of Al, B, Li, K, Na, CA, Mg, Ti, Fe, Mn, Cu, Cr, Ni and other impurity elements in the product, the high-purity quartz sand can be divided into three parts.
Low end ≤ 1000×10-6
Middle end ≤ 100×10-6
High end ≤ 20×10-6
Each grade of high-purity quartz sand can be divided into 40-80 mesh, 80-140 mesh, 80-200 mesh, 80-300 mesh etc.

Raw material selection technology of high purity quartz sand
1.Why can't crystal be used as industrial raw material of high purity quartz sand?
High purity quartz sand is made from natural crystal at first, and then refined. Natural crystal is usually formed in a cave environment under certain geological conditions.
A.The natural crystal reserves are small and the mining conditions are poor. After years of development and utilization, it will inevitably lead to the shortage of resources and high price, which is difficult to meet the needs of large-scale industrial production;
 
B. Due to the influence of the change of crystal environment, the chemical composition of natural crystal minerals is unstable, which leads to large fluctuations in the chemical composition of raw materials in large-scale industrial application, and it is difficult to standardize raw materials, so it is difficult to meet the needs of high-end production of high-purity quartz sand.
Therefore, we must start with other quartz mineral resources to fundamentally solve the problem of high purity quartz raw materials.
How to choose high purity quartz sand material?
In the 1990s, Japan used fine-grained pegmatite as raw material to process transparent high-purity quartz sand.
Russia and Germany use vein quartz and metamorphic quartzite as raw materials to process high-purity quartz sand.
In the 1980s, PPCC company of the United States processed high-purity quartz sand from foxdale granite on the northwest coast of England as the raw material of quartz glass in Western Europe. The purity of SO2 in the product is 4N and the content of Fe is less than 1 × The content of other impurity elements is less than 5×10-6。
Since the 1990s, Unimin company has been developing pegmatite granite in spruce pine, North Carolina. It has developed a series of high-purity quartz products such as IOTA-STD(standard grade), IOTA-4, IOTA-6 and IOTA-8.
It can be seen that in addition to natural quartz, vein quartz and granite quartz are ideal raw materials to replace natural quartz and process high-purity quartz and high-end products.
What is the selection standard of high purity quartz?
According to the current processing technology level, not all vein quartz and granite quartz can process high-purity quartz sand, only a few can process high-end products. The main reasons are as follows
The vein quartz and granite have many subdivided genetic types, which are influenced by the metallogenic geological conditions;
The mineralogical, petrological and mineralogical characteristics of vein quartz and granite of the same genetic type are quite different.
According to reports, the U.S. Unimin company is very strict in the selection of high-purity quartz raw materials.
Raw material selection standard of Unimin quartz:
One is quartz with the least impurity in crystal structure, such as iota-std aluminum content (14-18) × 10-6, iota-4 aluminum content (8-10) × 10-6；
The other is quartz with less gas-liquid inclusions, such as pegmatite granite and crystal.
Practice shows that the content of impurity elements in raw materials is not simply related to their quality, but to the impurity washability determined by the process mineralogical characteristics of raw materials.
For example, the content of impurity elements in spruce pine pegmatite samples in the United States is quite high, but it is the raw material of iota high-end products.
Therefore, it is necessary to strengthen the mineralogy, petrology and mineralogy of high-purity quartz mineral resources, focus on the process mineralogy characteristics of raw materials, such as chemical composition, useful minerals (quartz), harmful minerals, texture and structure, quartz inclusion, and find out the distribution and occurrence of impurities in raw materials, as well as their influence and mechanism on the application of high-purity quartz, It provides scientific basis for raw material selection technology and mineral resources exploration of high purity quartz ore.