Application Of Titanium in The Chemical Industry

The application of titanium in the chemical industry is widely used in many sectors of the national economy due to its excellent corrosion resistance, mechanical properties, and process properties. Especially in chemical production, the use of titanium instead of stainless steel, nickel-based alloys, and other rare metals as corrosion-resistant materials will increase production, improve product quality, extend equipment service life, reduce consumption, reduce energy consumption, reduce costs, and prevent pollution. , Improving working conditions and increasing productivity are of great significance. In recent years, the scope of titanium used in my country's chemical industry has been expanding, and the amount used has increased year by year. Titanium has become one of the main anti-corrosion materials in chemical equipment. Titanium, as a corrosion-resistant structural material used in chemical equipment, has established its position, and as an ideal material in chemical equipment, titanium has attracted more and more attention from engineers and technicians. (1) Chlor-alkali industry 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 better than that of commonly used stainless steel and other non-ferrous metals. At present, titanium is widely used in the Chlor-alkali industry to manufacture metal anode electrolyzers, ion-exchange membrane electrolyzers, wet chlorine coolers, refined brine preheaters, dechlorination towers, chlorine cooling scrubbers, etc. In the past, the main components of this equipment used 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 was bulky, energy-consuming, and short-lived. , And affect product quality and pollute the environment. Therefore, since the 1970s, my country has successively replaced graphite cells with metal anode cells and ion-exchange membrane cells and replaced graphite coolers with titanium wet chlorine coolers, all of which have achieved good results. For example the application of titanium wet chlorine cooler. The production of caustic soda by the electrolysis of table salt is to produce a large amount of high temperature and humid chlorine gas, the temperature is generally 75~95℃, and it needs to be cooled and dried before it can be used. The production of chlorine produced by electrolysis of table salt in my country has previously affected the production and quality of chlorine due to unreasonable cooling processes or corrosion of cooling equipment, and also seriously polluted the environment. Titanium coolers that are resistant to corrosion by high temperature and wet chlorine gas were put into production, which changed the appearance of chlorine production in the Chlor-alkali industry. Titanium is extremely resistant to corrosion in a high temperature and humid chlorine environment. The corrosion rate of titanium in chlorine water at room temperature is 0.000565mm/a; in chlorine water at 80°C, the corrosion rate of titanium is 0.00431mm/a; when it contains 95% In wet chlorine, the corrosion rate of titanium at room temperature is 0.00096mm/a. Many Chlor-alkali wet chlorine gas coolers made of titanium are often used, and some have been used for nearly 20 years and are still intact. (2) Soda ash industry Soda ash is one of the most basic chemical raw materials, and it is directly related to the development of the national economy. In the production process of soda ash, the gas media are mostly NH3 and CO2, and the liquid media are mostly NaCl, NH4Cl, NH4HCO3, and Cl-  solutions with higher concentrations. Carbon steel and cast iron are used for carbonization tower tubes and hot mother liquor coolers. The main equipment such as cooler, crystallization external cooler, etc., are not corrosion-resistant, with serious corrosion and leakage, and the service life is not more than three years. From 1975 to 1977, Tianjin Soda Plant and Dalian Chemical Industry Company built factories to carry out titanium application demonstration work, carbonization tower cooling pipe 63×2mm, titanium plate heat exchanger, titanium external cooler, titanium pump, CO2 turbocompressor rotor The application effect of Ti-6Al-4V alloy impeller is very good, which has played a model role for the whole industry to carry out technical transformation with titanium and to build three new soda ash plants with an annual output of 600,000 tons.

For example, the ammonia condenser at the top of the distillation tower of a soda ash plant uses pure titanium pipes instead of cast iron pipes. An ammonia condenser is a device for condensing ammonia vapor from the distillation tower during the production process of soda ash. It consists of two cast iron cooling boxes, each with a diameter of 2.5m and a height of 1.2m. The original box is Φ63×6. ×2986mm cast iron small tubes 214 pieces, two boxes total 428 pieces. Both the inside and outside of the tube are anticorrosive with thermosetting novolac, and the medium outside the tube is NH3, CO2, H2O vapor, and the temperature is about 95℃. The mother liquor of NH4Cl is taken inside the tube to exchange heat with the medium outside the tube. Under this condition, the cast iron pipes are severely corroded, and some pipes will corrode and perforate after one year of use, and have been corroded and damaged severely after two years, so stop using them. In order to solve the serious corrosion problem of the cast iron pipe in the ammonia condenser, all the cast iron pipes were replaced with TA2 titanium pipes with a specification of Φ60×2×3010mm. The end of the titanium pipe and the cast iron flower plate were sealed with an O-shaped rubber ring. This is the first distillation tower in my country's soda ash industry whose cooling tube uses pure titanium tubes. It has been in production for more than two years, and the pipe has been drawn for macro inspection, and no corrosion has been found. The expected service life can reach more than 20 years, which is 10 times longer than that of cast-iron pipes. Due to the corrosion resistance of the titanium tube, the heat transfer efficiency is maintained well (the cast-iron tube has a good heat transfer efficiency in the early stage, poor in the middle stage, and failure in the later stage during a three-year overhaul). Temperature can save a lot of steam, economic benefits are obvious.