Doubts about distillation column operation
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Approximately 60% of the EO aqueous solution enters the tower from the side, and high-purity EO (99.99%) is obtained from the middle and upper sections of the tower. There are two coolers at the top of the tower, followed by a reflux tank. Recently, the high-purity EO product has not met the required standards. Lowering the temperature at the bottom of the tower reduces the liquid level in the reflux tank, but increasing the reflux flow at the top again fails to maintain a stable liquid level in the tank. The operations were normal before; it’s not clear what’s causing the problem now. During recent maintenance, several screws were found at the bottom of the tower, raising suspicions that there might be an issue with the internal components of the tower. If the problem does not lie with the internal components, I would appreciate any advice regarding possible operational errors. Thank you!
There isn’t enough information. If the operating parameters of the tower remain unchanged, one should pay attention to the temperature at the discharge point, as well as the temperature differences between the discharge point and the bottom and top of the tower, as well as the pressure drop across the entire tower. These factors can help determine whether it is a buildup of light components, heavy components, or a decrease in the tower’s separation efficiency
With the operating parameters unchanged and the test failing, could it be that the components of the feed material have changed? Also, could the tower pressure drop increase, leading to liquid phase entrainment or flooding? Screws were found; damage to the tray also increases the likelihood of entrainment
As mentioned above, first check whether there have been any changes in the feed components. Check again to see if the tower top cooler is leaking. If everything else is fine, then check whether there is a problem with the packing (trays) inside the tower. Let’s look at other issues first; after all, the cost of dismantling a tower is quite high~~
How has the condensation temperature at the top of your tower been recently? What is the amount of material returning? Have you checked this first?
Plate failures lead to a decline in separation efficiency; currently, the only option is to increase the reflux and raise the reactor temperature to maintain the specified product quality.
The variations in the process components are unlikely to be significant; even if there are changes, they won’t be substantial. However, the pressure drop across the tower is indeed high. The issues of liquid entrainment or flooding you mentioned could occur. So what should I do to address this?
Is the pressure drop always high, or does it start to increase only when a problem occurs? My understanding is that pressure drop is the resistance of the gas; the greater the resistance, the greater the pressure drop, and vice versa. If the pressure drop is high only when problems occur, consider whether the tray might be blocked. Of course, if there is a condenser at the top of the tower, the enhanced condensation effect will also result in a greater pressure drop; when the weather gets cooler, the amount of cooling water used can be reduced appropriately. If the pressure drop remains high and liquid phase entrainment occurs, it is generally due to improper operation that results in large fluctuations in air pressure. In such cases, it is necessary to operate as smoothly as possible; in particular, when adjusting the steam supply to the reboiler, this should be done in coordination with the pressure control valve at the top of the tower as well as the subsequent systems. In fact, all these components should be adjusted as part of a single system.