Discussion on magnetic separation purification of high purity quartz sand
Discussion on magnetic separation purification of high purity quartz sand
Introduction of high purity quartz sand
As an essential basic material in high-tech field, high purity quartz sand has been used more and more widely.
High purity quartz sand, as the name suggests, is the purity of high impurities less quartz sand, SIO ₂ content is greater than 99.9% (3N), mainly used in communications, electronics, photovoltaic and other high-tech areas, is the highest added value products in all quartz sand products.
Low iron quartz sand is the iron content less than 120PPM of quartz sand products, its impurities content is low, SIO ₂ content generally greater than 99% (2N), mainly used in the production of ultra-white glass, its transmittance up to 91.5%, much higher than the ordinary glass of 86% transmittance. As a raw material for the production of ultra-white glass, low iron quartz sand is a product with relatively high added value in quartz sand products. In some occasions, low iron quartz sand is divided into the range of high pure quartz sand.
With the increasing demand for quartz sand in the society, the quality requirements are getting higher and higher, and the demand for high purity quartz sand is also increasing, while natural quartz sand contains a lot of harmful impurities, so the purification process of quartz sand is very important.
Characteristics of purification process of high purity quartz sand
High purity quartz sand SIO ₂ content is very high, the total content of impurities in general not more than 1000PPM, and the type of impurities is often not a single, can not be removed by a single way, so each purification method for the specific impurities content is lower, which puts forward more stringent requirements for purification means.
Purification methods such as magnetic separation, flotation, pickling and roasting are the main purification processes for the production of high-purity quartz at present. Each purification process requires targeted removal of different kinds of impurities during production. Due to the very low content of impurities, in the purification process, it is necessary to accurately control each condition, avoid unnecessary consumption and secondary pollution, and finally obtain high purity quartz sand in line with the standard.
As a purification method of iron removal, magnetic separation has the characteristics of zero emission and no consumption of chemicals. As an environmentally friendly and economic purification method, magnetic separation has been widely used in the field of quartz purification. In the removal of iron impurities for high purity quartz sand, magnetic separation also has an irreplaceable role, at the same time, high purity quartz sand purification also put forward more stringent requirements for the application of magnetic separation.
There are many kinds of magnetic separation equipment for quartz sand purification. The current conventional equipment mainly has the following six categories, and a few occasions will also use centrifugal magnetic separator, superconducting separator and other equipment.
Wet drum magnetic separator
Flat belt wet magnetic separator
Wet high intensity magnetic separator
Slurry material purification machine
Drum vibration powder magnetic separator
Roller powder magnetic separator
Development trend of magnetic separation equipment for high purity quartz sand
Limitations of conventional magnetic separation purification
Through the quartz sand and impurities of magnetic differences for magnetic separation, mainly for ferriferous magnetic minerals. At present, the conventional magnetic separation purification process of quartz sand is as follows: crushing - grinding - desliming - grading - medium magnetic - high intensity magnetic - high intensity magnetic second stage.
According to the conventional process, some quartz ore samples from Inner Mongolia, Guangdong, Anhui and other regions have been purified. The iron content of quartz concentrate is mostly 200‐800PPM, and the total impurity content is generally around 5000PPM, which still has a certain gap from the index of high-purity quartz sand.
Taking the conventional vertical ring wet high intensity magnetic machine as an example, due to the limitation of the structure form, its background magnetic field intensity will not exceed 1.8T, and the suction factor of the medium surface will not exceed 1016.
Impurities in high purity quartz purification stage, the main impurities is the life body, inclusions and so on, wet high intensity magnetic separator can be forced to absorb some impurities, but under the influence of interference force, part of impurities from medium will be sucked to quartz concentrate again, in addition to iron, especially for iron content in addition to 100 ppm of quartz concentrate iron, High intensity magnetic separator at some time will appear to be weak, at the same time in the medium box under the salvage will lose a part of the concentrate, the final magnetic separation effect outweighs the loss.
Conventional magnetic separation equipment has excellent effect in the primary iron removal, but it is not ideal in the purification stage of high purity quartz with very low iron content and complicated continuous production and packaging.
Development trend of magnetic separation for high purity quartz sand
At present, the typical purification process of high purity quartz sand is mainly based on magnetic separation + pickling + flotation. The specific ideas are as follows: magnetic separation treatment of magnetic impurities, pickling treatment of metal oxide impurities, flotation treatment of feldspar mica and other non-metallic impurities.
There are two types of magnetic separation on the market, wet magnetic separation and dry magnetic separation.
Wet magnetic separation is widely used in the purification of quartz sand, which has the characteristics of significant iron removal effect, large handling capacity and no dust pollution. In the primary stage of quartz sand purification, wet magnetic separation is generally considered to be an excellent way of iron removal purification, but in the stage of high-purity quartz cleaning, the conventional wet magnetic separation purification effect is not obvious, the reasons can be summarized as three points.
•The iron content is very low, and the probability of magnetic force effectively of magnetic particles capturing is low.
• Iron impurity has weak magnetism and insufficient magnetic suction
• In the process of wet separation, the fluid reaction force is strong and complex, and the fluid force cannot be controlled accurately
Therefore, whether the effective magnetic contact probability can be increased, the magnetic field suction can be increased, and the reaction force can be effectively controlled are the problems faced by the application of magnetic separation in the field of high purity.
Dry magnetic separation has the characteristics of high material distribution control, magnetic field forms, weak fluid force, in the case of high purity quartz iron removal, dry magnetic separation is more suitable. According to the characteristics of high purity quartz sand, special dry magnetic separation equipment is developed, which has a positive effect on the production of high purity quartz sand with stable purity. Therefore, dry magnetic separation equipment can be used as a powerful purification means of high purity quartz in the cleaning stage in the future.
LONGi can provide the customer wet magnetic separation and dry magnetic separation equipment, and through continuous innovation, promote product iteration and upgrade, promote the development of high-purity quartz sand production technology.
