Antiseptic Application of Titanium and Titanium Alloys in Chemical Industry-Chlor-Alkali Industrial Equipment
Titanium is characterized by strong corrosion resistance, which is due to its strong affinity to oxygen, can form a dense oxide film on its surface, which can protect titanium from medium corrosion. Metal titanium can form a passivation oxide film on the surface in most aqueous solutions. Therefore, titanium has good stability in acidic, alkaline, neutral salt solution and oxidizing medium, and has better corrosion resistance than existing stainless steel and other non-ferrous metals, and even comparable to platinum. However, if a titanium surface oxide film is continuously dissolved in a certain medium, titanium is corroded in such a medium. For example, titanium is corroded in hydrofluoric acid, concentrated or hot hydrochloric acid, sulfuric acid, and phosphoric acid because these solutions dissolve the titanium surface oxide film. If oxidant or some metal ions are added to these solutions, the oxide film on the surface of titanium will be protected, and the stability of titanium will increase.
The chlor-alkali industry is an important basic raw material industry, and its production and development have a great impact on the national economy. This is because the corrosion resistance of titanium to chloride ions is superior to that of commonly used stainless steels and other non-ferrous metals. At present, titanium is widely used in the chlor-alkali industry to manufacture metal anode electrolyzers, ion membrane electrolyzers, wet chlorine coolers, refined brine preheaters, dechlorination towers, chlorine gas cooling scrubbers, and the like. The main components of these equipment used to be non-metallic materials (such as graphite, polyvinyl chloride, etc.). Due to the unsatisfactory mechanical properties, thermal stability and processing performance of non-metallic materials, the equipment is cumbersome, energy-intensive, short-lived, and affects product quality and environmental pollution. Therefore, since the 1970s, China has successively replaced the graphite electric trough with metal anode electric tank and ion film electric trough, and replaced the graphite cooler with titanium wet chlorine cooler, which has achieved good results.
For example, the application of wet chlorine cooler made of titanium.
Salt electrolysis produces caustic soda to produce a large amount of high-temperature wet chlorine gas, the temperature is generally 75 ~ 95 ° C, need to be cooled and dried before use.
China's salt electrolysis to produce chlorine gas production. Previously, due to unreasonable cooling processes or corrosion problems due to cooling equipment, chlorine production and quality were affected, and the environment was seriously polluted. The production of titanium cooler with high temperature and wet chlorine corrosion resistance has changed the production efficiency of chlorine production in chlor-alkali industry. Titanium is extremely resistant to corrosion in a high temperature wet chlorine atmosphere, and the corrosion rate of titanium in chlorinated water at normal temperature is 0.000565 mm/a; In chlorine water at 80 ° C, the corrosion rate of titanium is 0.00431 mm / a; In a 95% wet chlorine gas, the corrosion rate of titanium at room temperature is 0.00096 mm/a. Many chlor-alkali plants have used titanium wet chlorine gas coolers, and some have been in use for nearly 20 years and are still intact.