This paper introduces in detail the process of processing high-purity quartz sand by using quartz gravel, which mainly includes crushing, self grinding with water, optical separation, calcination, grinding, cleaning, etc. Finally, the total amount of trace metal elements in quartz sand can be less than 50ppm, and the content of SiO2 is more than 99.99%.
At present, most of the ancient quartz veins have been destroyed by geological process and accumulated together after being transported and rounded, forming an egg shaped quartz gravel layer (stone shed), with a resource of 100 million tons. The surface of quartz gravel is generally attached with brown red or brown yellow iron thin film, and the internal cracks are developed, and the cracks are filled with impurities. These gravels have low SO2 content and high impurity content. If they can be used as raw materials to produce quartz sand for transparent quartz glass, the shortage of high-quality quartz resources will be fundamentally solved.
The silica sand processing plant
adopts the following technical scheme:
Step 1: Take quartz gravel and crush it into pieces.
Step 2: Put quartz gravel fragments into the autogenous mill
, and add water to the autogenous grinding machine according to the mass ratio of quartz gravel to water of 1:035-0.5 for autogrinding.
Step 3: In the quartz gravel fragments after self grinding, the qualified gravel fragments are obtained after removing the quartz gravel fragments containing impurities, and then the qualified quartz gravel fragments are calcined at 900℃-950℃ for 2-2.5 hours, then water quenching is carried out to soften the qualified quartz gravel fragments, and then the softened quartz fragments are crushed by the dobule roller crusher to obtain quartz sand.
Step 4: place the softened qualified quartz gravel fragments in alkali solution (sodium hydroxide content > 20%), heat them to boiling and keep them for 30-45 minutes, take out quartz sand, then immerse them in acid solution (sulfuric acid > 10%) at 50-60 ℃ for 15-25 minutes, and then take them out. Finally, clean the quartz sand with deionized water to make the pH value of 6.8-7.0, and then dry them at 70 ℃-80 ℃.
This sand processing plant has the following technical advantages:
1.This sand processing plant adopts self grinding with water, which can not only lubricate but also clean the surface. Through self grinding, iron pollution and impurities in the cracks on the gravel surface can be removed. That is to say, the gravel fragments and water are put together in the autogenous mill for self grinding, the fragments collide with each other, and the iron film on the surface can be removed. When the gravels collide with each other, they will break along the fracture surface, so that the fillings between the fractures and the attached iron film on the fracture surface can be exposed and separated from the gravels with friction. In this way, the problem of difficult separation caused by mixing the iron film, sundries and quartz fragments caused by crushing the gravels directly can be avoided, and the SiO2 content of quartz sand can be increased and the impurity content can be reduced.
2.In this sand processing plant, the qualified quartz is selected by the method of light selection, that is, the quartz fragments that have been peeled off the skin by self grinding with a certain intensity of light, which can not only distinguish the transparency of the quartz fragments, but also can distinguish whether there are opaque impurities inside the quartz fragments, so as to remove the unqualified fragments containing opaque (many impurities) or dark spots inside and select the qualified quartz.
3.This sand processing plant adopts alkali leaching, that is, dissolving and decomposing fine aluminosilicate minerals with alkali solution such as sodium hydroxide, which has better effect and further reduces environmental pollution. The purity of quartz sand is improved by using acid, especially sulfuric acid to remove trace aluminum and iron in sand, while sulfuric acid is colorless, tasteless and relatively environmental friendly.
4.This sand processing plant processing quartz gravel to produce quartz sand for transparent quartz glass will effectively improve the utilization value of quartz gravel resources, alleviate the contradiction of high-purity quartz resources shortage, and greatly reduce the heavy environmental pollution in the acid treatment process such as hydrofluoric acid.
5.The SiO2 content of quartz gravel (raw ore) is 97% - 98.5%, the iron content is more than 0.8%, and the impurity content of aluminum and potassium is more than 0.5%. Iron is mainly deposited on the surface of gravel or cracks in the form of film, and more than 99% can be removed by self grinding with water and screening. Aluminum, potassium and other elements are mainly distributed in fine (0.05mm) muscovite minerals, muscovite is often distributed on the fracture surface, a few are distributed between crystalline quartz particles, and more than 97% can be removed by self grinding with water, screening and grading (mainly distributed in powder less than 0.125mm, a few are in the form of particles on the surface of quartz sand). The SiO2 content of quartz sand is 99.85% - 99.89% which is prepared by the physical non pollution processing process such as self grinding, optical separation, calcination, grinding, grading (powder removal) etc. sodium hydroxide reacts with muscovite to form water-soluble salt. When heated sodium hydroxide solution boils muscovite, the decomposition (dissolution) rate of muscovite is more than 99%. Sulfuric acid can dissolve iron oxide, aluminum (salt) and other trace metal elements, wash quartz sand with hot sulfuric acid solution, remove residual aluminum salt, iron oxide and other metals, so that the total amount of trace metal element impurities in quartz sand is less than 50ppm, and the content of SiO2 is greater than 99.99%, meeting the requirements of raw materials for transparent quartz glass tube production.
Remarks: Sinonine can provide EPC service for high-purity quartz sand processing plant.