Titanium dioxide is a commercial name, its chemical name is titanium dioxide, and its molecular formula is TiO2. Titanium dioxide has high refractive index, ideal particle size distribution, good covering power and coloring power. It is a kind of white chemical pigment with excellent performance. It is widely used in coatings, rubber, plastics, paper making, printing ink, daily chemical industry and other industries. In recent years, with the rapid development of China's national economy and the continuous improvement of people's living standards, titanium dioxide industry presents a rapid development trend.
Generally speaking, there are two main types of titanium dioxide production technology in China: sulfuric acid process and chlorination process. Because a large number of scab particles are produced in the process of chlorination titanium dioxide gas-phase oxidation, they cannot be completely dispersed in the beating process. If these scab particles are not sand ground, they will be directly coated in the coating process. After crushing by the steamer, the scab particles are incomplete and irregular in shape, which affects the product quality, It is an important reason for low dispersion and color difference of products. In order to solve this problem, screening experiments were carried out on oxidized incoming material and mortar after grinding to determine the number of scars and to study the role of grinder in the post-treatment process of titanium dioxide. The development of production technology of titanium dioxide in China has gone through three stages: the first stage is from the middle of 1950s to the end of 1970s. The annual production capacity of titanium dioxide in China is only 20,000 tons, and most of them are low-grade varieties. In 1978, the total output of titanium dioxide in China was less than 20,000 t, of which the proportion of pigmented titanium dioxide was less than 15% .This stage is characterized by backward technology and slow development.
The second stage started from the end of 1970s to the end of 1980s. The technical level of production process of titanium dioxide by sulfuric acid method has been rapidly developed, and anatase and rutile products have been produced one after another. The national capacity of titanium dioxide has increased dramatically from 20,000 t to 100,000 t.During this period, new breakthroughs in production technology of titanium dioxide by sulphuric acid method were achieved due to the scientific and technological key problem of comprehensive utilization of Panzhihua vanadium-titanium magnetite resources, which promoted the rapid improvement of technical level in production plant of titanium dioxide by sulphuric acid method in the middle of 1980s. And the third stage is from the 1990s to now, the production capacity and output have expanded year by year, the national titanium dioxide output reached 1.472 million tons in 2010. At the same time, new breakthroughs have been made in production technology. The large-scale production units of rutile titanium dioxide by sulfuric acid method imported from abroad have been put into operation successively, and the large-scale production units of titanium dioxide by chlorination method imported have been digested and absorbed in China, and have also been put into operation smoothly. The introduction and use of titanium dioxide production equipment not only improves the production technology of titanium dioxide in China, but also changes the backward situation that only small-scale workshop sulfuric acid production method and low-grade anatase titanium dioxide can be produced in China.
Sand mill is an important process of titanium dioxide after treatment, which is not only required by sulfuric acid method, but also by chlorination method. Sand mill is a kind of super particle dispersion machine produced by wet continuous production. The role of sand grinding is to further crush the agglomerated particles, agglomerated particles and flocculation particles produced in the previous process. Because of the weak binding force between the particles, it is easy to open them by mechanical grinding, and prevent them from agglomerating together under the action of dispersant, this makes some coarse particles, after grinding, reach the particle size range with application performance.
Application of sand mill in titanium dioxide production
The sand milling process is an important process link to produce high-grade rutile titanium dioxide. Abroad, the material before coating is ground by grinder starts early and is widely used.
In the production of rutile-type titanium dioxide, the role of grinder cannot be underestimated because it can separate large agglomerated particles, and after grinding, the titanium dioxide particles are spherical and have no edges and corners. The particle size is less than 1um and the particle size distribution is relatively concentrated. Therefore, the coated products have excellent pigments and optical properties. There are many sand mills manufactured at home and abroad, but the horizontal sand mill by FARFLY has a high reputation in the titanium dioxide industry at home and abroad, which has been proved and unanimously recognized by many users.
Due to the compact structure, the motor is placed above the grinding drum and the grinding simplicity is placed below, which not only ensures smooth operation, but also greatly reduces the total height of the equipment. Besides, large-type sand mills have simple slides for easy maintenance.
The new structure and horizontal type of mixing plate of the sand mill overcome the disadvantage of non-uniform distribution of grinding medium existing in traditional vertical grinder, thus greatly improving grinding efficiency. Due to the uniform distribution of the abrasive medium, sufficient contact can be made between the abrasive medium and the abrasive material, avoiding collision and friction between the particles of the abrasive medium in areas with high density caused by the uneven distribution of the abrasive medium.This not only affects the grinding efficiency, but also reduces the service life of the grinding medium. At the same time, due to the wear of the grinding medium, the components of the grinded medium will pollute the material to a certain extent. Where the density of the abrasive medium is low, the density of the material increases, so that the material cannot be grinded well and the grinding efficiency is reduced.
3.1.3 Double-end mechanical seal for mixing shaft
Double-end mechanical seal system with forced coolant circulation cooling guarantees clean mechanical seal fluid, avoids abrasion of mechanical seal system, has good sealing effect and prolongs service life of mechanical seal system.
3.2 Material of cylinder and stirring grinding plate
According to the specific grinding and crushing materials, stainless steel, ceramics, polyurethane and other materials can be used for grinding drum and stirring grinding disc. These materials not only have certain strength, but also have good wear resistance, which will not pollute the abrasive material.
3.3 Grinding process
ccording to different production process requirements, grinding processes of grinders are also different.
3.3.1 Continuous grinding process
The slurry for grinding is fed quantitatively by the feed pump into the grinding mill with the grinding medium for grinding. The grinded material is separated by a dynamic graded rotor separator and discharged at the outlet. Continuous grinding process can adopt single or multiple continuous grinding processes according to different requirements for fineness of the abrasive material.
Cyclic grinding processThe slurry to be ground is fed quantitatively into the grinding drum of the grinder by the feed pump. After the grinded material is separated by a dynamic stage separator, the material is returned to the feed storage tank of the grinder through the return pipe for re-grinding. The length of lapping time can be determined by the fineness requirements of the material. The process is suitable for situations requiring high fineness of materials.
The application of sand mill in the titanium dioxide industry has its unique role and position. The sand mill is used to grind the intermediate material of titanium dioxide to be coated, so that the material particles are fine and uniform, the particle size distribution is concentrated, and the particle shape is geometric spherical, thus improving the pigment performance, optical properties and dispersibility of the final product of titanium dioxide. In a sense, the grinding effect of sand mill is irreplaceable.
In the face of the increasingly fierce competition in the titanium dioxide market and the challenge of high-grade products from foreign titanium dioxide manufacturing companies, we should try our best to adopt advanced technology and equipment, improve product quality and build our own brand, so that the quality of our titanium dioxide products can gradually rank among the international advanced level of titanium dioxide, and reach the level of approaching, catching up or competing, The application of sand mill will play a more positive role in promoting the development of titanium dioxide industry with Chinese characteristics.