Why is the pressure at the top of the atmospheric tower higher than the pressure at its bottom in the three-collapse distillation process?

Is the reflux flow too high? Also, check whether there are any air pockets or liquid obstructions in the gas line from the top of the tower to the reflux tank – causes such as differences in equipment elevation may be at play

Generally, at the top of the tower there is a large amount of vapor and oil, with significant water content in the oil; this is due to the high proportion of gaseous components. Additionally, the liquid phase reaching the bottom of the tower encounters resistance from the tray structure, so a slight increase in pressure is normal. However, if the increase is substantial, it warrants further consideration, as water in the oil can cause an increase in tower pressure upon vaporization in the atmospheric pressure tower distributor, as well as a decrease in the liquid level at the bottom of the tower. It often carries back water from the reflux zone, resulting in a large amount of reflux and an increase in the light components. Leakage in a certain return cooler tube bundle, etc. Also, when the backflow of oil and gas is constant, it leads to an increase in tower pressure; therefore, it is necessary to analyze the reasons for this increase.

The pressure at the top of the tower is indeed slightly higher than that at the bottom; however, if it’s too high, it’s not normal

Is the backflow volume high? Are there any air pockets in the vapor pipeline at the top of the tower?

It’s likely that the pressure gauge is inaccurate; just calibrate it and that will do