Why is the pressure in the reflux tank of the vapor phase unit higher than the tower pressure?
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I think the normal condition should be to keep the pressure in the reflux tank lower than the tower pressure; why is it the opposite for us? Distillation stabilization means keeping the pressure in the reflux tank lower than the pressure in the tower
In the vapor separation unit, the depropanization tower, propylene tower, and butane tower all have a tank pressure that is lower than the tower pressure; only the deethanization tower has a tank pressure that is higher than the tower pressure. This is because the coolers in our system are located above the reflux tank, and the tower pressure plus the liquid column pressure within the coolers theoretically equals the tank pressure, which is in line with theoretical principles. In the remaining towers, the cooler is at a lower level than the tank; therefore, the tower pressure equals the tank pressure plus the liquid column pressure.
I roughly understand what you mean, but I don’t fully get it. For example, in terms of stabilizing the flow rate, it is necessary to control the pressure in the reflux tanks of the fractionation tower and the stabilization tower so that it does not exceed the pressure inside the towers; only then can the material at the top of the towers move forward. In our case, the pressures in the reflux tanks of the depropanization tower, deethanization tower, and propylene tower are all slightly higher than the tower pressures, by about 0.01–0.02 MPa. I wonder how the material can flow forward when the pressure in the reflux tanks is higher than that in the towers As for the issue of equipment layout you mentioned, in our system the height of the stable air-cooling units is always higher than that of the return tanks, which is contrary to what you said.
If the pressure in the reflux tank is high, how can the material in the tower enter the reflux tank? Unless the height of your reflux tank building exceeds the height of the tower.
All the tower pressures in our gas separation unit are much higher than the pressure in the reflux tank
I think the same way, but if there’s a problem with the watches, it’s impossible for all of these watches to have issues
As long as there are sufficient perfusion heads, the pump can be started to feed material via the posterior route; this is a dynamic equilibrium.
What I mean is that as long as the tower pressure plus the height of the liquid column is greater than the tank pressure, the material will move backward; it’s a matter of balance. Don’t focus only on the pressure; the pressure ratio in the fractionation stabilizer, as well as the tank pressure, differ from those in the actual plant due to the presence of a compressor. From a purely stability perspective, everything should be fine, and this is also a characteristic of thermal bypass control.
Similar to the atmospheric distillation column in vacuum distillation, the atmospheric column also uses low-power compressors; the gas from the deethanization column is directly flared, which does not really conform to this principle either
Are the pressure gauge ranges for the tower and the tank different? Or there is an issue with the signal conversion of the DCS. If the pressure in the tank is higher than the pressure in the tower, the material at the top of the tower will not enter the reflux tank. This is a matter of fundamental principles. It’s certain.
The pressure in the stabilizer, even with heat bypass backflow to the tank, remains lower than the tower pressure