Why WFE/SPD? Part 2 of 5 Devolatilization
The question arises: How do you know when wiped film distillation is the better option?
This five part series will explore a few reasons or circumstances that wiped film could be a good choice for your distillation. Should you wish to discuss a specific application, please message me, and we will set up a free call.
Reason two to consider wiped film distillation: Devolatilization
Sometimes it is necessary to distill volatiles out of a mixture, leaving behind the desired product. Some common examples of materials that are often devolatilized are food products, oils, polymers and nutraceuticals. Many times the volatile component is water or a solvent and just needs to be lowered to less than 1%. Other times the volatile compound may be a starting material from the reaction and has to be removed as low as 20 ppm prior to proceeding with the process.
Whatever the exact need, wiped film distillations are the superior choice for devolatilization.
Too often, these steps are performed in reactors.
However, performing devolatilization in reactors will either take a long time or never reach the desired target. Other conventional equipment used are devices like rotovaps, simple bulb to bulb distillation, and Kugelrohrs.
All of these have the same disadvantage.
As the distillation proceeds, it becomes harder and harder to remove the volatile material from the mixture. The reason being the volatile material is heated to boiling on the heat source of the system, and then has to travel through the entire mixture to escape into the gas phase. If the volatile component cools a little, it won’t make it into the vapor phase. If your target is <0.5% ethanol, for example, you may find that the ethanol amount drops to about 1% pretty quickly. However, to complete the devolatilization, it may require heating and pulling vacuum for many hours to finish the distillation.
On the other hand, when a wiped film still is used, the volatiles have no trouble leaving the mixture.
In a wiped film still, the material is spread into a thin film and the volatiles can freely exit the mixture to the vapor phase. The feed is spread over the heated surface area of the still and violently mixed by the wiper blades, creating perfect conditions for complete devolatilization. Wiped film stills are capable of taking a mixture containing as much 5-10% volatile material and decreasing the content to as low as 0.1% in a single pass. If your process today consists of many hours in a conventional pot still, consider switching to wiped film distillation.