Unstable tower pressure in a distillation column: possible causes

Plate corrosion, low column pressure, plate blockage, high column pressure. I suspect that in the owner’s tower, liquid has accumulated near the feed port, resulting in insufficient gas-liquid exchange and blocked pathways

Is there a possibility that the tray could fall off?

Reply to 1# laoshiling: 1. The feed composition is unstable. 2. The liquid level at the bottom of the tower and the temperature at the reboiler outlet are not proper. 3. The PID parameters of the instruments have not been adjusted correctly

The factors that affect the variation in column pressure are: ① top temperature of the column, ② bottom temperature of the column, ③ feed composition, ④ feed rate, ⑤ reflux rate, ⑥ refrigerant amount and refrigerant pressure. Additionally, instrument failures and freezing of equipment and pipelines can also cause changes in tower pressure.

Changes in feed composition, changes in furnace outlet temperature, moisture in the raw material, changes in heat exchange temperature, liquid accumulation at the tower inlet, instrument issues, improperly adjusted PID parameters, fluctuations in reflux, fluctuations in tower top temperature, etc

Also, it’s possible that an excessive amount of gas is being blown at the bottom of the tower, causing the gas to burst through the liquid layer in pulses

There are many factors that cause changes in the pressure at the top of the tower, which can be roughly categorized into instruments, process conditions, equipment, and the properties of the raw materials. 1. Aging, corrosion, blockage, vibration, and other issues related to the instruments occur periodically, which leads to changes in detection and transmission processes and thus causes pressure variations; it is necessary to address these issues with the relevant instruments. 2. Process-related factors include the amount of reflux, feed rate, amount of coolant at the top of the tower, and amount of steam at the bottom of the tower, as well as aspects such as reflux extraction and bottom extraction; these factors cause changes in the composition of the gas and liquid phases inside the tower, resulting in changes in the pressure at the top of the tower. 3. Equipment-related factors include the siphoning effect of the reboiler and the outlet flow rate of the pump used for extracting liquid from the bottom of the tower (this issue is more severe in cases of forced circulation); these factors lead to changes in the amount of steam at the bottom of the tower, thereby causing changes in the gas and liquid phases inside the tower, and ultimately leading to changes in the pressure at the top of the tower. 4. Regarding raw materials, it is important to analyze whether there are any changes in their composition and whether the various components are evenly distributed