Abstract: In order to solve the dew point corrosion problem in the atmospheric distillation column overhead line in a petrochemical enterprise, the PR (Peng-Robinson) state equation method based on the binary interaction of hydrocarbon and water was adopted, and the process calculation model of the overhead system under standard conditions was established. Based on the mechanism of the dew point formation, the state changes of the corrosive medium in the oil-gas-water three-phase before and after the dew point were analyzed. The distribution of HCl and H₂S in the overhead line of the column under different water injection ratios and the influence of top pressure, stripping steam volume and water injection ratio on dew point temperature under different S and N contents in the feed oil and constant oil content were studied. The results showed that HCl and H₂S were the key factors causing dew point corrosion. With the condensation process, the content of HCl in the overhead line of the column increasesd, and the content of H2S increased first and then decreased. The dew point temperature of the overhead water is 100.45 °C, and there is a positive correlation between the column top pressure, stripping steam quantity, the water injection ratio and the dew point temperature, the average dew point temperature increases by 2.97 °C per 0.02 MPa of top pressure increases.

Key words: atmospheric distillation column, overhead reflux line, dew point temperature, overhead pressure, stripping steam volume, water injection ratio