Corrosion and protection effects on the oil-gas side of carbon steel water cooler tubes in petrochemical industries
Thread Content
Corrosion and protection effects on the oil-gas side of the tube bundles in carbon steel water coolers in the petrochemical industry: As the quality of crude oil deteriorates, equipment corrosion becomes severe during processing. When processing crude oil, a sulfur content of 0.62%, a salt content of 248 mg Nace/g, and an acid value of 0.35 mg NaOH/g indicate poor quality. During crude oil processing, +Ice generated by the hydrolysis of calcium and magnesium salts, along with H2S produced by the decomposition of sulfides, dissolve in water in the initial cooling zone of the equipment, thereby causing corrosion of the equipment due to the HCl-H2S-H2O medium. The oil-side tube walls of the heat exchanger tube bundles are among the areas most susceptible to corrosion. In the past, there were no effective protective measures; the average service life of these tubes was only about two years. Moreover, perforations led to leaks that caused product contamination and affected production stability, making this a problem that petrochemical companies have been striving to resolve for many years. Similar to the protection of carbon steel coolers, finding a corrosion-resistant coating is the method that offers the best overall benefits. In the past, some oil-resistant coatings were also used in petrochemical industries, but due to high temperatures and aggressive corrosive environments, their performance was not good. The refinery experimentally applied lacquer-modified coatings on the outside of the tube bundles in the reduced-pressure distillation unit’s top condenser. After one production cycle (11 months) of use, the coating remained intact without any bubbling and retained its original brightness, demonstrating excellent corrosion resistance. The greatest advantage of applying this coating is that it effectively slows down the corrosion of the tube bundles, extending the service life of the equipment (from two years without protection to about four years). It also reduces the need for shutdowns for repairs, improves the quality and speed of maintenance work, and saves the company considerable amounts of money. Taking a Ф900 tube bundle as an example: the price of the tube bundle is 7,000 yuan per ton × 4.7 tons = 32,900 yuan; after being used for two years, the cost amounts to 16,450 yuan per year. The cost of coating protection is 100 yuan/m2 × 240 m2 = 24,000 yuan. Assuming the protection lasts for four years, the annual cost is 14,225 yuan per year. It can be seen that installing a Ф900 heat exchanger core saves the enterprise an average of 2,225 yuan per year.
In the petrochemical industry, the processing of crude oil can lead to severe equipment corrosion, especially when the crude oil being processed contains high levels of sulfur, salts, and acid value. Chloride ions produced by the hydrolysis of calcium and magnesium salts, along with hydrogen sulfide (H2S) generated by the decomposition of sulfides, combine with water in the initial cooling section of the equipment, causing severe corrosion of the materials involved; this corrosion is primarily caused by hydrogen chloride (HCl), hydrogen sulfide, and water (H2O). The tube wall on the oil side of the tube bundle in carbon steel water coolers is one of the areas where this type of corrosion is most severe. In the past, due to the lack of effective protection measures, the average service life of the tube bundles (cores) in these heat exchangers was only about two years; moreover, perforations and leaks would cause product contamination as well as problems with production stability. To solve this problem, developing and applying corrosion-resistant coatings is an effective approach. Petroleum companies have previously tried some oil-resistant coatings, but due to the high temperatures and strong corrosiveness of the operating environment, the performance of these coatings was not satisfactory. However, when a refinery experimentally applied lacquer-modified corrosion-resistant coatings on the outside of the cooler tubes in its vacuum distillation unit, after one production cycle (11 months) of use, the coatings demonstrated good durability, remained intact without bubbles, retained their gloss, and provided effective corrosion protection. The greatest advantage of applying corrosion-resistant coatings is that it significantly slows down the rate of corrosion of the tube bundles, thereby extending the service life of the equipment from two years to about four years. It also reduces downtime for repairs caused by corrosion, improves the quality and speed of maintenance work, and saves the company substantial amounts of money. The text provides a specific example for calculating economic benefits: without any protective measures, the price of Ф900 tube bundles is 7,000 yuan per ton; with a total weight of 4.7 tons, the total cost amounts to 32,900 yuan. If it needs to be replaced every two years, the average annual cost is 16,450 yuan. The cost of using coating protection is 100 yuan per m^2; with an area of 240 m^2, the total cost is 24,000 yuan. Assuming a service life of four years after protection, the average annual cost is reduced to 14,225 yuan. At this rate, it can save the company 2,225 yuan per year. This case shows that although the initial investment in coating protection is high, it can save costs for businesses in the long run by extending the lifespan of equipment, thereby improving production efficiency and equipment reliability. .