Standard chemical industries like oil and gas have multiple processes to achieve quality products. Distillation columns are some of the necessary equipment a processing plant must have. Therefore, all engineering services must ensure the integrity of these devices to operate optimally. However, every engineering project is not safe from problems. Your column may operate smoothly initially, but it will be problematic along the way. In worst cases, you will need a distillation column manufacturer to build a new one because you cannot fix them once you install them. To be on the safe side, take note of these factors affecting the operation of distillation columns to build a desirable system.
Distillation Column
A distillation column is a tall structure with built-in trays for distilling liquids. It carries flammable and combustible fluids in a hazardous process with high-temperature pressure conditions.
Problems in the Distillation Column
Various problems could occur within a distillation column. These problems are classified into flow, feed, tray, and weather conditions. Here is a complete breakdown of these factors.
1. Feed Conditions
The feed composition and mixture condition impact the operating lines and the number of stages needed in separation. During operations, excessive deviation from the design specifications may cause the column not to handle separation tasks. A distillation column manufacturer builds columns with multiple feed points to manage problems associated with the feed.
2. Reflux Conditions
An increase in the reflux ratio pushes the gradient of the operating line for the rectification section moves towards the maximum value of 1. In this situation, liquids with more volatile components recycle back into the column. By improving separation, the lesser the need for trays to achieve the same level of separation. Total reflux conditions require minimum trays because there is no distillate withdrawal. Alternatively, as reflux decreases, the operating line for the rectification section moves close to the equilibrium line. The more trays required, the more pronounced the pinch between equilibrium and operating lines.
3. Vapour Flow Conditions
In case of adverse vapour flow conditions, the column operation could experience;
- Flooding
- Entrainment
- Dumping
- Foaming
Flooding
Flooding occurs when excess vapour flows, causing the vapour’s entrainment in the column. Increasing pressure from excess vapour backs up the liquid in the downcomer, leading to fluid holdup on the above plate. The maximum capacity of the column could be severely reduced depending on the flooding degree. Any sharp increase in the column differential pressure and decrease in separation efficiency could signify flooding.
Entrainment
Entrainment is the amount of liquid the vapour carries to the overhead tray during high vapour flow rates. It is dangerous because it reduces efficiency due to the less volatile material to a plate with higher volatility liquid carries. This could additionally contaminate the highly pure distillate.
Dumping
Dumping is a result of a low vapour flow when the vapour’s pressure is not enough to hold up the liquid on the tray. Therefore, the liquid may start leaking via the perforations. During dumping, the liquid on the trays will crash via the column’s base. A sharp pressure drop indicates weeping, which reduces the efficiency of separation.
Foaming
Foaming is the expansion of liquid from passing gas and vapour. Even though it provides high interfacial liquid-vapour contact, too much foaming can cause flooding in the trays. The foam will mix with the liquid on the above tray in extreme foaming cases. The chances of foaming occurring depend on the physical properties of the liquid mixtures and tray designs.
4. Column Diameter
Most issues affecting column operation stem from poor column diameters by the distillation column manufacturer. Weeping outlines the minimum vapour flow requirement, while flooding outlines the maximum allowed vapour flow. Therefore, a poorly sized column diameter will not perform optimally. While it may cause operational problems, it could affect the separation duties.
5. Weather Conditions
Distillation columns from heavy engineering companies in India are usually placed in the open. Despite insulating these columns, constantly changing weather conditions could affect the operation of the columns. Therefore, a perfectly-sized boiler is needed to generate enough vapour in cold and windy weather. During hot seasons, it could be turned down, even in condensers.
These are the major factors that affect the performance of distillation columns. Some other factors to consider along the way include changing operation conditions and throughputs caused by upstream condition changes. These factors must be considered in the designing phase because it will be hard to rectify the errors after installing the column. Therefore, before installation, reach out to column manufacturers to build one according to your specifications.
