Application Of Titanium In Petrochemical Industry
Titanium heat exchangers, condensers and related auxiliary equipment have been successfully used for more than 20 years in petrochemical enterprises. Among the titanium materials, the most commonly used industrial pure titanium (TA2 is the most widely used), Ti-6Al-4V (when a certain strength is required) and Ti-0.8Ni-0.3Mo (when there is a gap or in a non-oxidizing medium) . When hydrogen absorption and hydrogen embrittlement may occur, especially in the case of weld corrosion and hydrogen absorption, low iron .
(1) In the refining of crude oil with high sulfur and salt content, titanium equipment is ideal. In foreign countries, titanium equipment has been successfully used in many processes such as atmospheric distillation equipment, sewage treatment equipment, desulfurization separation tower condenser and stripping tower radiator for many years. Our country has also used cast titanium seawater pumps, titanium condensers in catalytic cracking fractionation, cryogenic separation 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 of petrochemicals. Due to the chlorination reaction involved, stainless steel equipment has been difficult to handle. In foreign countries, titanium materials have been used to manufacture methylene chloride rectification towers, trichloroethane heat exchangers, condensation towers and fractionation towers, trichloroethylene condensation towers, perchloroethylene heat exchangers and polychloride coil heaters. In the production of vinyl chloride in my country, the cooling towers, waste water stripping towers and waste water storage tanks have used Ti-0. 2Pd linings for the tray support frames, connection pipes, and flange sealing surfaces, which have been used for nearly ten years without corrosion. Titanium pipes, joints and gas distributors have all been made of titanium 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 refining oil and gas as raw materials. Foreign countries have adopted titanium equipment more than ten years ago, and this technology is still under development in my country. The old process used benzene sulfonated alkali solution to produce phenol. Our country has adopted titanium neutralization reactor, titanium coil cooler and ion titanium nitride agitator shaft sleeve, and the effect is very good.
(4) In the device where ethylene is oxidized to acetaldehyde, acetaldehyde is oxidized to acetic acid and propylene is oxidized to synthesize acetone, in addition to the corrosiveness of raw materials and products, the main corrosive medium is catalyst. Stainless steel corrodes quickly, and only titanium Has good corrosion resistance. As early as 1963, the United States successfully applied titanium in the production of acetaldehyde by oxidation of ethylene. my country's first ethylene oxidation to acetaldehyde plant was put into use in 1976, and the titanium plant has been operating well so far. Foreign titanium-lined reactors are as high as 9.6m, with a diameter of 3m, and there are 11 titanium equipment including heat exchangers, catalyst regeneration towers, and acetaldehyde solution coolers. After the 1980s in my country, Shanghai and Jilin each introduced foreign complete sets of equipment for the production of acetaldehyde by ethylene oxidation. Many of the equipment and pump valves are made of titanium, which has obvious advantages over stainless steel and has very satisfactory results. For the finalized design of propylene oxidation to acetone, there are 12 titanium equipment, a plant with an annual output of 30,000 tons of acetone, and the titanium equipment reaches 40t.
(5) Oxidation of acetaldehyde to acetic acid is a common process in my country. Titanium has been used as a high-boiling reboiler, first-grade acetic acid tower reboiler and condensation cooler and other equipment. Foreign countries have adopted titanium equipment in rectification towers, fractionation towers and distillation towers. Especially in the oxidation of lower alkane to produce acetic acid, there are many by-products, the formic acid content is up to 8%, and the corrosiveness is extremely strong. At this time, the effect of replacing stainless steel with titanium is very ideal.
(6) Terephthalic acid is the raw material of synthetic polyester, which is prepared by the p-xylene oxidation method in industry. No matter high temperature oxidation or low temperature oxidation, there is high temperature corrosion of acetic acid and bromide. In the medium with temperature higher than 135℃, pitting corrosion of 316L stainless steel will occur after dozens of hours. Therefore, the design specification stipulates that titanium must be used above 135°C. Beijing Petrochemical General Plant has introduced a complete set of titanium equipment, including 16 oxidation reactors, solvent dehydration towers, heaters, condensers, and reboilers. Nanjing Yangzi Petrochemical Company introduced an annual output of 450,000 tons of terephthalic acid equipment, 56 sets of titanium equipment and a large number of titanium pipeline valves. The oxidation reactor introduced by Shanghai Petrochemical Plant is 32m high, with an upper diameter of 4m, a lower diameter of 5.3m, a volume of 505m, and a weight of 175t. The effect of using titanium material is very good, and the prospect of promotion and application is bright.
(7) Urea is a high-quality fertilizer and a raw material for petrochemical industry. Since the first titanium-lined urea synthesis tower was put into production in 1963, nearly 10,000 equipments have been in operation all over the world. Practice has shown that the titanium-lined synthesis tower has no obvious corrosion. The converted corrosion rate of 316L stainless steel is 4.1-4.5 mm/a. Therefore, titanium has better economic benefits than stainless steel. In addition to the titanium-lined urea synthesis tower, CO2 stripping towers, heat exchangers, mixers and pump valves have been used in China since the 1970s.
