Titanium dioxide is considered to be the most superior white pigment in the world. It is non-toxic with the best opacity, whiteness and brightness, and widely used in coatings, plastics, papermaking, printing inks, chemical fibers, rubber, ceramics, cosmetics, food and medicine industries. Titanium dioxide is known as "industrial monosodium glutamate", and its per capita consumption serves as an important indicator of a country's economic development level, as well as a strong evidence of the country's market potential. There are two titanium dioxide production processes: sulfate process and chlorination process.
The chlorination process was industrialized in the United States in 1956. It mainly uses rutile or titanium chloride slag as raw materials and only produce rutile products. The specific process is as follows: Firstly, chlorinate rutile or titanium chloride slag at high temperature to produce titanium tetrachloride, and then purify and oxidize the titanium tetrachloride. The oxidation process is the core of the chlorination process, and finally the titanium dioxide product is obtained through washing, drying, crushing and other post-treatment processes. The chlorination and oxidation processes are both continuous production except the post-treatment process.
Today, we mainly introduce the titanium dioxide production sulphate process.
The main raw materials of sulfate process are titanium raw material and sulfuric acid. Titanium raw material can be either titanium concentrate or acid soluble titanium slag. The product can be anatase or rutile titanium dioxide.
The operation procedure of TiO2 sulfate process is very complex. The basic chemical reactions include a series of simple chemical reactions, such as acid hydrolysis, hydrolysis and calcination with iron ore concentrate as the raw material. In the sulfate process, ilmenite and sulfuric acid are used as raw materials. First, decompose the ilmenite into TiOSO4 solution with sulfuric acid, and remove insoluble impurities from the titanium solution by filtration, then remove FeSO47H2O by vacuum crystallization and solid-liquid separation. After the concentration and thermal hydrolysis, the metatitanic acid can be prepared, and romove the soluble sulfate by washing and bleaching and then drain it. After calcination, dehydration and desulfurization, it is converted into titanium dioxide. Anatase products can be obtained after dry grinding, or uncoated rutile initial products or products can be obtained by adding accelerant for the crystal transformation during the calcination process. For example, in the production of high-grade rutile products, the initial products must be pulped, and then it should be depolymerized and classified by wet grinding. After inorganic surface treatment, the salt in the material should be washed away, and then the superfine grinding and organic treatment should be carried out after drying.
1. The difference of particle size: The atomic size of chlorination process titanium dioxide is 190-250 nm, while that of sulfate process titanium dioxide is 250-450 nm;
2. Color difference: Due to the particle size and impurities, the color phase of sulfate process titanium dioxide belongs to yellow phase, while that of chlorination process titanium dioxide is blue phase;
3. The difference of dispersion: There is no significant difference between them. At present, high dispersion products that are suitable for water-based, oil-based, plastic and other systems have been developed;
4. Price difference: Due to the high requirements of raw materials and large investment in production equipment, the overall cost of chlorination process is higher than that of sulfate process, and so is the price of chlorination process TiO2 products.