Among them, the production of titanium dioxide by sulfuric acid method has a history of more than 80 years, and it is still produced in many countries in the world. Its technical route is mature, with low requirements for equipment and raw materials, and it can produce anatase and rutile products. Although the operation process is long, the operation of each process is complicated, the process variables are large and the discharge of "three wastes" is large, the production of titanium dioxide by sulfuric acid method still has strong vitality and will continue for a long time.
Titanium dioxide production by sulfuric acid method can be divided into solid phase method, liquid phase method, two-phase method and pressure method according to the acid hydrolysis reaction process. At present, the solid phase method is used in industry.
Since the solid-state process was determined in the 1920s, the mainstream has not changed much. In the late 1950s, in order to improve the weather resistance of rutile titanium dioxide, the post-treatment process of surface treatment was added. Up to now, there is no big change except for the refinement of some processes, such as increasing thermal filtration of titanium liquid to improve the purification effect of titanium liquid, increasing bleaching to improve the purification effect of metatitanic acid, and increasing sand grinding classification to improve the crushing effect. In addition, different enterprises will choose different equipment according to the regional characteristics of enterprises in some processes, but the operation of the unit remains basically unchanged.
The main production processes of sulfuric acid anatase titanium dioxide include titanium ore crushing, acidolysis, sedimentation, coarse filtration of titanium liquid, ferrous crystallization, ferrous separation, controlled filtration of titanium liquid, concentration of titanium liquid, hydrolysis, primary water washing, bleaching, secondary water washing, salt treatment, calcination, crushing and packaging. Ordinary and auxiliary processes include: mud washing, white water recovery, tail gas treatment, desalted water preparation, steam boiler, raw water treatment, sewage treatment and other processes.
Compared with the production of titanium dioxide by sulfuric acid method, the process of producing titanium dioxide by chlorination method is shorter, the production capacity of the device is greater, the degree of automation is higher and the product quality is better. However, the chlorination technology in the world, especially the core oxidation-related technology, is still only in the hands of a few companies, especially the technical blockade, which makes the development of titanium dioxide industry by chlorination in China slow.
Simply put, the process of producing titanium dioxide by chlorination mainly includes three parts: chlorination, oxidation and post-treatment.
At present, the production of titanium dioxide by hydrochloric acid is only seen in patents and laboratories.
On the basis of the first set of liquid chromium salt production in the world, the Institute of Process Engineering of China Academy of Sciences put forward a new clean production process of titanium dioxide by sub-molten salt method for the first time, which is completely different from sulfuric acid method and chlorination method, and can efficiently and selectively convert titanium in ilmenite into titanate at low temperature to produce rutile titanium dioxide. The pilot test of this method has been completed in a domestic factory.