The important role of titanium and titanium alloy materials in the vacuum salt production industry

Titanium is widely used in aerospace, navigation, submarines and medical industries. With the improvement of process technology, titanium is increasingly used in general civilian industries, among which titanium for vacuum salt making is one of the earliest areas for titanium application promotion.
my country's salt making industry is mainly based on sea salt, followed by well salt and lake salt. Since the 1950s, vacuum salt making factories have gradually emerged. With the continuous construction and production of vacuum salt making factories, the severe corrosion of high-temperature concentrated brine on carbon steel equipment for vacuum salt making directly affects the performance of equipment capacity and the normal operation of production. Corrosion causes frequent maintenance of equipment and a large amount of leakage, which has become a key production and technical issue that needs to be solved urgently. The correct selection of corrosion-resistant materials suitable for the salt making industry has also been urgently put on the agenda. Titanium and titanium alloys have excellent resistance to seawater and chloride solution corrosion and fluid erosion. Since 1975, Hunan Xiangli Salt Mine, Hubei Yingcheng Salt Factory, Sichuan Zigong Well Salt Factory, etc. have begun to use titanium materials to make equipment in large quantities. In the 150,000-ton refined salt project introduced by Yingkou Salt Chemical Plant, titanium was also selected for its salt evaporation equipment. In the 1990s, titanium was also widely used in heat exchangers in my country's salt industry. In the salt production process, the corrosion problem of salt slurry pipelines is particularly prominent. When using carbon steel pipes, the lower part of the pipe will be corroded into a honeycomb hole in just half a month, and leaks have to be frequently repaired, and the salt slurry pipeline needs to be replaced up to 6 times a year. Even if stainless steel is used, corrosion perforation will occur after 4 months. At the same time, corrosion and other metal compounds penetrate into the brine, which has a great impact on the quality of salts. In addition, the roughness of the tank wall such as carbon steel also makes the fouling problem more serious. As time goes by, the fouling will become thicker and thicker, and eventually form large pieces of salt scale, reduce the circulation volume, affect the heat transfer of the brine, and even block the entrance of the heating chamber, causing shutdowns and even burning the motor in severe cases. In order to provide a more practical and reliable scientific basis for the selection of titanium materials in vacuum salt production, units such as Hunan Xiangli Salt Mine and Sichuan Zigong Jing Salt Factory conducted titanium hanging sheet tests at the salt production site. Test data show that titanium has remarkable corrosion resistance under the actual conditions of chloride and vacuum salt production. After using titanium, due to its corrosion resistance and no impurity generation, the technical problems of difficulty in improving salt quality and serious loss of production equipment have been completely solved. It can be said that the application of titanium has brought a new revolution in the material selection of vacuum salt production.
In the vacuum salt production process, the heating chamber is the most critical equipment. With the birth and development of titanium and titanium alloys, they have been promoted to the salt production industry by the state because of their excellent resistance to chloride ions. Domestic salt production basically adopts the four-effect vacuum salt production process, and titanium is mainly used in heat exchangers and heat exchange tubes. The heat exchange tube is generally 9 meters long and the wall thickness is between 0.8 and 1.5 mm. Titanium has few impurities on the surface and strong corrosion resistance, so it is not easy to corrode perforation and pipeline blockage. Under the same heat transfer performance, the titanium heating chamber has the advantages of light weight and small volume compared with the steel pipe heating chamber. At the same time, in the salt production process, the brine preheater is also an important process equipment. In an environment below 100°C, titanium has strong corrosion resistance in NaCl (sodium chloride) solution. Therefore, the use of titanium in the manufacture of brine preheater tube bundles and heads can effectively prevent the corrosion of preheater parts by NaCl solution, thereby ensuring the normal use of the equipment. With the deepening of the understanding of titanium performance and application, titanium and its alloys are gradually being promoted and applied in the vacuum salt making industry. The vacuum salt making industry has become one of the major users of titanium and titanium steel composite plates.