Summarize the problems that should be paid attention to when using titanium equipment

Since titanium's passivation film is dependent on the presence of oxygen, titanium is suitable for use in an oxidizing or aerobic environment. In seawater and other chloride-containing solutions, titanium and its alloys have excellent resistance to pitting at room temperature and at elevated temperatures. It is in the presence of wet chlorine gas. Almost no corrosion in the solution. In the vacuum salt production process, the impact of salt sand accelerates the corrosion of the salt production equipment. Usually, the higher the flow rate, the more the corrosion is. It destroys the oxide film on the metal surface and causes the metal to be exposed in the solution. Titanium recovers quickly. The ability of the passivation film, the alloy also has excellent comprehensive performance, so titanium and its alloys can be applied to the salt process. The application of titanium in the main equipment requires preheating before the brine preheater brine enters the heater to save energy. Preheaters often use tube-type heat exchangers. The material of heat exchange tubes is made of carbon steel. It is easy to block and corrode the tubes. The heat exchange tubes are often replaced and the production is stopped for maintenance. This brings great inconvenience to production. There is also a preheater using copper tubes. Corrosion conditions still exist. The service life is extended to one year, but it is still very short, and the cost of copper tubes is high. In the last decade, titanium plate heat exchangers have appeared one after another.

Heating and Evaporation System In the history of salt production at the well salt factory, the heater was originally made of steel and the corrosion was quite severe. The effect heater has the highest temperature and the corrosion is the most serious. Corrosion and pipe wear often occur. As the heat exchange tubes are closely arranged on the tube plates, maintenance and inspection are time-consuming and the heat pipes need to be replaced once a year. Outages during major repairs delayed production, production was reduced, production was seriously affected, and maintenance costs were high. Some manufacturers used copper for the heating chamber and the situation improved. In view of the characteristics of titanium materials, if titanium is used as a heater, the situation will be greatly improved. The self-heating evaporator is used in the well-salt factory and its heating chamber is outside the evaporator. The effective temperature decreases in turn, the heating tube can be made of pure titanium, and the value can be adjusted to a suitable position when used. The anticorrosion effect is good. So far, the heating tube of the Roots vacuum pump has been intact, no corrosion phenomenon has occurred, and the time for maintenance and repair has been greatly reduced, and the number of workers has been reduced. The labor intensity.

Titanium equipment should pay attention to the problem, in almost all cases, titanium is a relatively large pole in the galvanic couple, it will not increase corrosion due to the formation of galvanic coupling, but can increase the corrosion of another metal, the design should be minimized Small potential difference, to avoid galvanic corrosion as much as possible. Before production, the quality of raw materials should be inspected. The welding performance of titanium materials is poor, and welding quality is not easy to guarantee. When welding, strict inert gas protection should be adopted to ensure the welding conditions. Due to the large investment and difficult processing, in order to prolong its service life, it should be operated strictly in accordance with the operating procedures to control the temperature and pH of the medium and the concentration of the medium, protect the passivation film, and do not use acid to clean the equipment. The working state. Since the formation of the passivation film requires oxygen, the deoxidation step set when using the carbon steel as a heating pipe should be eliminated. The application of titanium material in other equipment The application of titanium material in other equipments is less in Zigong, mainly because one-time investment is large. The pump is the heart of the chemical plant. The circulating pump is used to deliver salt slurry. The circulating pumps currently used are large-flow, low-lift axial-flow pumps. The material is corrosion-resistant cast iron, but the corrosion is still present and the maintenance volume is large. . If its flow components such as impellers, guide vanes, etc. are made of titanium, their normal working hours should be greatly increased. Xiang Heng Salt Mine uses a titanium pump and has not been repaired except to replace wearing parts. In addition, the important valve parts are made of titanium materials. If the design is used properly, it should be able to achieve good economic benefits. This issue needs to be further discussed. From the comprehensive characteristics of titanium materials, especially the corrosion resistance and the use of wells in salt wells; the use of titanium in its process system is feasible, because of its good corrosion resistance, low maintenance costs, long production time , has achieved very good economic benefits, is a good prospect of development of materials, its application can be expanded.

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