Leakage Cause Analysis And Corrosion Prevention For Air Cooler At The Top Of Depentanizer Of Continuous Catalytic Reformer

The air cooler at the top of depentanizer is one of the important equipments in CCR.In the daily operation,the tube bundle leaks frequently.Because the medium is flammable and explosive components such as C₄and C₅of liquefied gas,it is extremely dangerous and easy to cause major accidents such as fire and explosion.Taking Dalian Petrochemical 2.2 million tons/year continuous reforming unit as the background,through the leakage analysis and research of pentane tower top air cooler of the unit,the appropriate anti-corrosion measures were found to ensure the long-term safe operation of the equipment.Through the analysis and detection of equipment leakage and salt deposition,the source,content and corrosion mechanism of ammonium chloride,chlorine and nitrogen are analyzed and studied.It is confirmed that the leakage in the area with low flow rate and low temperature at the outlet of air cooler is caused by salt deposition corrosion of ammonium chloride.By comparing and analyzing the operation data and anticorrosion measures data of similar domestic devices,the operation parameters and Anticorrosion Scheme Design of the device are determined.In this paper,the anticorrosive mechanism of anticorrosive coating,liquid phase dechlorination and water washing of air cooler are studied,and the process and parameters are designed.The on-line corrosion monitoring technology was used to study the comprehensive application of various anti-corrosion technologies.According to the change of corrosion rate,the liquid phase dechlorination and depentane tower top air cooling online water injection were adjusted to change passive anti-corrosion into active intervention anti-corrosion.The effectiveness of the anti-corrosion measures was verified by judging the service life of the air cooler.The results show that the main reason for the leakage of depentanizer overhead air cooler is the corrosion of ammonium chloride salt deposition.The main measures to remove salt deposition and anticorrosion are as follows:pipe bundle anticorrosion,liquid phase dechlorination,water injection.The theoretical dosage of liquid phase dechlorination is 33.39t to 41.66 T,and the content of HCl after dechlorination is less than 0.5 mg/kg.The water quantity of air cooling water injection is 5%（W）of tower top material quantity,and the water quantity is 2438.68kg/h.After water injection,the chloride ion content in the washing water decreased from 1200 ppm to below 100 ppm.At the same time,according to the data provided by online corrosion monitoring,the specific anti-corrosion measures are optimized in time.The corrosion rate of the tube bundle of the depentanizer overhead air cooler was controlled below 0.2mm/n.