Abstract: Corrosion leakage occurs frequently in the atmospheric distillation column overhead heat exchanger of certain petrochemical company. There are many corrosion pits on the inner wall of the tube bundle where the ammonium salt scaling is serious. These corrosion pits are linear and there're obvious corrosion grooves, which are typical characteristics of ammonium salt underdeposit corrosion. The management of the electrical desalting process, operation, inspection and monitoring of the device was optimized. The results show that the salt content of the electrical desalting unit decreased obviously after the secondary desalination, and only 0.15% of the data exceeded the standard. A series of process and material protective measures were adopted for the atmospheric distillation column overhead heat exchanger, such as carrying out multi-point water injection for the distillate line, installing sprinklers for each water injection line, increasing water injection volume to 24 t/h and maintaining 30% of liquid water, selecting neutralizer with lower salt scaling temperature, upgrading the tube bundle material to titanium alloy and so on. And the application effects indicated that the salt scaling area of the tube bundlewas reduced and there was slight salt scaling; there was no abnormal thinning of the inlet and outlet pipelines of the atmospheric distillation column overhead heat exchanger; and the titanium alloy tube bundle that had run for three years was corroded slightly.

Key words: distillation unit, heat exchanger, ammonium salt, under-deposit corrosion, protection