Roy Rahul 
Liquid constituent separation is an essential process in industrial applications. Whether it’s wastewater treatment, petrochemical processing or pharmaceutical manufacturing, an effective and safe compound removal method is vital in ensuring safe and clean environmental byproducts. There exist several liquid-liquid separation methods. Each has its benefits and downsides, as well as its best-suited applications. For instance, there are the extraction, distillation and stripping columns. However, this guide tries to explain in detail about stripping columns in refinery; keep on to find out more.
What Is A Stripping Column?
It is a piece of chemical equipment usually used in physical separation. It’s used where there is the need to remove more than one component from a liquid stream using a vapour stream. While in use, like in industrial applications like refineries, the vapour and liquid stream can have countercurrent or co-current flows. The working basis of tripping is based on mass transfer.
The main objective is to make the working conditions favourable for the component in the liquid phase to transfer to the vapour phase. This process usually involves a gas-liquid interface that the components have to cross.
Furthermore, stripping columns can be categorised into three:
· Spray Column
· Plate Column and
· Packed Bad Column
The Working Principle Of Stripping
The stripping column uses the principle of absorption in its work. It is a chemical process in which a bulk phase of molecules, solid or liquid, is transferred into a gaseous substance. In the context of stripping columns in refineries, heavy engineering companies in India use steam as the gas responsible for absorbing the fluid molecules. Additionally, in the stripping column, the liquid particles separated from the feed are absorbed by the water vapour. It eventually leads to effective isolation from the preferred product.
In some instances, steam stripping is also referred to as scrubbing, as it entails removing the molecule constituents from the feed. Stripping introduces the steam feed at the top of the column. Distillation, though, introduces the feed in the middle of the column. The steam, usually gaseous boiling water, is introduced into the stripping column from the bottom. The process is countercurrent because the feed and the steam are injected from the column’s opposite ends.
As the feed travels downward from the top of the stripping column, it washes over the trays designed to increase the contact surface where steam and feed meet.
As the steam is introduced into the feed, volatiles with low boiling points are absorbed into the steam upon contact. The volatiles with the highest boiling points can’t undergo this process, but they will get absorbed into the steam and later removed because of their lower water solubility.
Afterwards, the steam with the absorbed components leaves the top of the stripping column, where it is collected, condensed and purified. It’s usually released directly into the atmosphere.
Advantages Of Stripping
Stripping is essential in refineries because it can decrease the pollutants expelled into the atmosphere or water sources. Some of its advantages include the following:
· Its Highly Effective
Industrial processing facilities are equipped with the responsibility to prevent harmful components like volatile organic compounds(VOCs)from getting into the atmosphere. Steam stripping does this job effectively and helps achieve environmental sustainability.
· It Doesn’t Have Boiling Point Restrictions
The distillation method is usually limited to the boiling points of each of the compounds. However, steam stripping doesn’t have these restrictions. Moreover, although it can’t absorb all organic compounds from the feed, an additional scrubbing process is usually implemented to help increase the stripping rate.
· Its Cost Effective
Steam stripping doesn’t need much energy to boil or cool the feed. There is a significant reduction in overall operational costs compared to distillation columns. Furthermore, this advantage makes it the best industrial investment for large processing industries.
Disadvantages Of Stripping
Steam stripping has one major disadvantage; a high initial investment cost. Steam stripping columns need to be pretty tall to increase their efficiency. Accommodating all the layers of packing trays, in turn, increases the contact surface area between the steam and the feed.
Therefore, the initial cost needed to cater for the labour and construction materials is always high.
For processing industries, choosing the best liquid-liquid separation process is an essential stage. It helps maximise the productivity and efficiency of the plant. Steam stripping is the best option because of its cost-effectiveness and high separation rate in handling VOCs.
