Exploration of the application of titanium and titanium alloy materials in vacuum salt making industry

China's salt industry is dominated by sea salt, followed by well mine salt and lake salt. Since the 1950s, vacuum salt-making plants have gradually emerged. However, from the 1970s, salt production equipment faced increasingly serious corrosion and dripping problems, especially the corrosion of chloride ions. Restricted by the development of metal materials in China at that time, most of the main equipment in the salt industry was made of carbon steel, but the service life was short, such as 20 carbon steel pipe in the heat exchanger, the general service life of no more than one year, or even a few months after the beginning of perforation phenomenon. Later try to use copper, the use of time has been extended, but about two to three years later still need to be replaced, equipment damage is serious, the replacement cost is high, and affect the production.
In order to solve this problem, since 1975, Hunan Xiangli Salt Mine, Hubei Yingcheng Salt Plant, Sichuan Zigong Well Salt Plant and so on began to use a large number of titanium production equipment. Yingkou Salt Chemical Plant in the introduction of 150,000 tons of refined salt project, its salt evaporation equipment also selected titanium. By the 1990s, China's salt industry heat exchangers also began to widely use titanium.
In the salt production process, the salt slurry pipeline corrosion problem is particularly prominent. The use of carbon steel pipe, only half a month of the lower part of the tube will be corroded into a honeycomb hole, had to frequently fill the leak, the annual need to replace the salt slurry pipeline as many as 6 times. Even with stainless steel, corrosion perforation occurs after 4 months. At the same time, due to corrosion and other metal compounds penetrate into the brine, the quality of the salts have a great impact. In addition, the roughness of the tank wall, such as carbon steel, makes the fouling problem even more serious. Over time, the fouling will become thicker and thicker, eventually forming a large area of salt scale, which reduces the circulation volume, affects the heat transfer of the brine, and even blocks the inlet of the heating chamber, resulting in a shutdown shutdown and, in severe cases, burns out the electric motor.

In order to provide a more practical and reliable scientific basis for the selection of titanium in the vacuum salt production, Hunan Province, Xiangli Salt Mine, Zigong Well Salt Plant in Sichuan Province, and other units in the salt production of titanium on-site hanging test. Test data show that titanium in chloride and vacuum salt production site under actual conditions of corrosion resistance is very significant. After the use of titanium, due to its corrosion resistance, no impurities, completely solve the salt quality is difficult to improve and production equipment loss of serious technical problems. It can be said that the application of titanium material has brought a new revolution in the selection of materials for 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 alloy, because of its excellent anti-chlorine ion performance, it is promoted to the salt industry by the state. Domestic salt production basically adopts four-effect vacuum salt production process, titanium is mainly used in heat exchangers and heat exchanger tubes. Heat exchanger tube is generally 9 meters long, wall thickness between 0.8 and 1.5 mm. Titanium surface impurities, strong corrosion resistance, so it is not easy to corrosion perforation and pipe clogging phenomenon. Under the same heat transfer performance, the titanium heating chamber has the advantages of light weight and small volume compared with the steel tube heating chamber.
Meanwhile, brine preheater is also an important process equipment in the salt production process. Titanium has strong corrosion resistance in NaCl (sodium chloride) solution in the environment below 100℃. Therefore, the use of titanium in the production of tube bundles and heads of brine preheaters can effectively avoid the corrosion of NaCl solution on the preheater parts, thus ensuring the normal use of the equipment.