Distillation tower pressure issues
Thread Content
Will a full liquid level in the bottom of a atmospheric distillation column cause a significant increase in the top pressure and the pressure in the reflux drum? Some expert please give a detailed explanation.
There are many factors that affect tower pressure! What causes the full liquid level in the tower bottom? Is it due to a large feed rate or insufficient heating? Is the product taken out from the bottom of the tower small, or is the reflux rate high? However, none of these factors will cause the tower pressure to rise!
The column pressure drop is related to the liquid holdup in the column internals. The space at the bottom of the column serves merely as a gas-phase buffer; a high liquid level may cause frequent pressure fluctuations, but it should not affect the pressure drop
A full liquid level in the tower bottom generally does not cause a significant increase in the pressure at the top of the tower or in the pressure of the reflux tank, as there is little relationship between these two pressures. The tower pressure is primarily influenced by the heat supply from the reboiler, the cooling load of the top condenser, and the amount of non-condensable gas discharged from the top of the tower. In extreme cases, when the bottom of the tower is filled with liquid to the point where the entire tower is full, this will cause a significant increase in the pressure at the top of the tower as well as in the pressure of the reflux tank. This issue often arises during startup, due to a malfunctioning level gauge.
Based on the reactions in the downstream tower of our unit, it should be that a large amount of light components fall to the bottom of the tower. My analysis is that when such a large quantity of light components reaches the bottom of the tower, the reboiling at the bottom remains unchanged; as a result, the vaporization rate increases rapidly, which prevents the cooling equipment at the top of the tower (air cooling) from condensing all of the vapor. This leads to an increase in pressure in the reflux tank and at the top of the tower.
OP, what is the pressure difference in your tower? As some friends mentioned above, how is the pressure at the top of your tower controlled? Are there large fluctuations in the condenser? If too many light components are carried to the bottom of the tower, then your sensitivity plate temperature will be very low.
In a atmospheric pressure tower, the tower pressure changes along with the load; it remains relatively constant under normal conditions. The sensitivity plate also increases as the tower pressure rises
It may be that seeing the reactor bottom full, the steam supply to the reactor bottom was increased excessively, resulting in an increase in reactor pressure.
Ours must be completely full – it’s really severe; it’s like the tower is flooded
The reason for the increase in tower pressure may be liquid carryover or flooding in the internals； The internal components may become clogged. It is recommended to observe changes in tower pressure by reducing the load; if the internal components are blocked, they can be cleaned during maintenance.