Abstract: Overhead water injection, as an important part of the anti-corrosion measures “one removal and three injections” for crude atmospheric and vacuum distillation units, has been promoted and applied in most refineries, and has been summarized and improved in practice, achieving good results. Due to the fact that water injection at the tower overhead can not only change the dew point temperature and increase the stream pH around dew point temperature to alleviate dew point corrosion, but also reduce salt and scale deposition in the system, thereby reducing under-deposit corrosion. In order to ensure the optimal effect of water injection, multiple factors need to be considered, mainly including water quality, injection position, injection volume, etc. Based on analyzing of the factors related to optimizing water injection, combining the industrial practical experience, the best guidance were proposed. Practical case results show that the measures such as optimizing water quality, dynamically adjusting injection volume, and selecting proper injection positions can bring significant economic benefits, improve anti-corrosion effects, and reduce safety hazards.

Key words: crude oil distillation unit, water injection, anti-corrosion, dew point, Pathfinder model