2019年12月19日星期四

Application of titanium and titanium alloy materials in petrochemical industry

Titanium heat exchangers, condensers and related auxiliary equipment have been successfully used in petrochemical enterprises for more than 20 years. The most commonly used industrial titanium in titanium (the most widely used is TA2), Ti-6Al-4V (when a certain strength is required), and Ti-0.8Ni-0.3Mo (when a gap exists or in a non-oxidizing medium) .
(1) In the crude oil refining with high sulfur and high salt content, titanium equipment is ideal. Many foreign countries have successfully selected titanium equipment for many years in atmospheric distillation equipment, sewage treatment equipment, condensers for desulfurization separation towers, and radiators for stripping towers. China has also used cast titanium seawater pumps, titanium condensers in catalytic cracking fractionation, cryogenically separated titanium condensers, and porous titanium plates in this system, all of which have been in normal operation for more than ten years.
(2) Chlorinated hydrocarbons are one of the largest varieties in petrochemical industry. Because of the chlorination reaction involved, stainless steel equipment has become incompetent. Dichloromethane rectification towers, trichloroethane heat exchangers, condensation towers and fractionation towers, trichloroethylene condensation towers, perchloroethylene heat exchangers and polychloride coil heaters have been manufactured from titanium materials abroad. In the production of vinyl chloride in China, Ti-0. 2Pd lining has been used for the cooling tower, waste water stripping tower and waste water storage tank's tray supporting frame, piping and flange sealing surface. It has not been used for nearly ten years. Titanium pipes, joints and gas distributors have been used for many years.
(3) Phenol is an important raw material for petrochemical industry. It is a new process to obtain phenol and acetone from cumene and cumene peroxide using propylene and benzene in oil and gas refining as raw materials. Titanium equipment has been used in foreign countries for more than a decade, and this process is still under development in China. In the old process, benzene sulfonated alkali solution was used to produce phenol. In China, a neutralization reactor made of titanium, a titanium coil cooler, and a stirrer shaft sleeve made of ionized titanium nitride have been used in China. The effect is very good.
(4) In the device for oxidizing ethylene to acetaldehyde, acetaldehyde to acetic acid, and propylene to synthesize acetone, in addition to the raw materials and products being corrosive, the main corrosive medium is the catalyst, stainless steel corrodes very quickly, only titanium Has good corrosion resistance. As early as 1963, the United States successfully applied titanium in the production of ethylene to acetaldehyde. China's first ethylene oxidation to acetaldehyde unit was put into use in 1976, and the titanium equipment has been operating well so far. Foreign titanium-lined reactors are up to 9.6m in diameter and 3m in diameter. There are also 11 titanium equipment such as heat exchangers, catalyst regeneration towers, and acetaldehyde solution coolers. Since the 1980s in China, Shanghai and Jilin have introduced foreign complete sets of equipment for ethylene oxidation to acetaldehyde. Many of these equipment and pump valves are made of titanium. Compared with stainless steel, it has obvious advantages and the use effect is very satisfactory. The final design of the oxidation of propylene to acetone. There are 12 titanium equipment, a factory with an annual output of 30,000 tons of acetone, and a titanium equipment of 40t.
(5) Oxidation of acetaldehyde to acetic acid is a common process in China. Titanium has been used as a high-boiler reboiler, first-grade acetic acid column reboiler and condensation cooler. Titanium equipment is used abroad in rectification towers, fractionation towers and distillation towers. Especially in the oxidation of lower alkanes to acetic acid, there are many by-products. The content of formic acid reaches 8%, which is extremely corrosive. At this time, the use of titanium instead of stainless steel is very effective.
(6) Terephthalic acid is a raw material for synthetic polyester. It is industrially prepared by the para-xylene oxidation method. No matter high temperature oxidation or low temperature oxidation, there is high temperature corrosion of acetic acid and bromide. In a medium with a temperature higher than 135 ° C, pitting corrosion occurs in 316L stainless steel after tens of hours. Therefore, the design code stipulates that titanium must be used above 135 ° C. Beijing Petrochemical Plant introduced a complete set of titanium equipment, including 16 oxidation reactors, solvent dehydration towers, heaters, condensers, reboilers and so on. Nanjing Yangzi Petrochemical Company has introduced an annual output of 450,000 tons of terephthalic acid equipment, 56 titanium equipment and a large number of titanium pipeline valves. The oxidation reactor introduced by Shanghai Petrochemical Plant has a height of 32m, an upper diameter of 4m, a lower diameter of 5.3m, a volume of 505m, and a weight of 175t. The use of titanium has a good effect, and it has a bright future for application.
(7) Urea is a high-quality chemical fertilizer and a petrochemical raw material. Since the first titanium-lined urea synthesis tower was put into production in 1963, nearly 10,000 devices have been running around the world. Practice has shown that there is no significant corrosion in the titanium-lined synthesis tower. The reduced corrosion rate of 316L stainless steel is 4.1-4.5mm / a. Therefore, titanium has better economic benefits than stainless steel. In addition to titanium-lined urea synthesis towers, since the 1970s, C02 stripping towers, heat exchangers, mixers and pump valves have been used in China.
Titanium is widely used in petrochemical industry, with numerous examples.
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