Analysis of thinning reasons for carbon steel pipeline of dehydrogenation tail gas in styrene unit.

The carbon steel pipe line of the dehydrogenation tail gas system in a certain styrene unit has a thinning rate of 55.51% and a corrosion rate of up to 5.29 mm/a after one year of use, which restricts the long-term stable operation of the plant. The corrosion of the dehydrogenation tail gas carbon steel pipeline was inspected through electromagnetic eddy current scanning, ultrasonic thickness measurement, and macroscopic inspection. The impact of corrosive medium, process operating parameters, on-site pipeline location and material on pipeline thinning in the dehydrogenation tail gas system was analyzed. The results indicate that the localized corrosion and thinning of the dehydrogenation tail gas carbon steel pipeline are caused by a combination of carbon dioxide corrosion and erosion corrosion under certain temperature and pressure. To alleviate corrosion issues, it is recommended to re-evaluate the process operating conditions of the dehydrogenation tail gas system, add cooling equipment before the dehydrogenation tail gas compressor, or upgrade the pipeline material to 304 austenitic stainless steel. Or consider adding corrosion inhibitors to the dehydrogenation exhaust system. At the same time, regular electromagnetic eddy current scanning or ultrasonic thickness measurement should be carried out to monitor the relevant pipelines and prevent leaks in a timely manner. [ABSTRACT FROM AUTHOR]