Through a variety of techniques and equipment setups, a distillation of compounds can occur. A highly effective and popular method is wiped film distillation. Though it’s also common to refer to it as thin film distillation, the two terms are interchangeable.
These systems are highly effective in working with heat-sensitive products and methods of distillation with high boiling values. Also, they are generally excellent for industrial or large-scale production where regulations and guidelines are in place.
The system is intricate and dense to understand, but it’s more straightforward to grasp once broken down. Here is a digestible and complete guide to wiped film evaporators.
There are a variety of names for a wiped film system. The one you use is dependent upon the method used inside the evaporator to create the thin film. The wiped film is the most common name. The wiper blade component spreads compounds evenly across the evaporator’s interior lining, which creates a “wiped” film that covers the entire surface of the evaporator.
The term “thin film” refers to a similar process. And in broader scopes, it can work with any system that wipes a thin film across the inner surface of an evaporator.
The rolled film refers to hollow cylinders or rollers stacked on top of each other around a retainment rod; these rollers are in the place of the wiper blades. A rolled film offers extended lifecycles for a wiper system due to drastically reduced contact with the evaporator’s exterior body surfaces.
As the wiper basket pivots, radial forces allow the roller to make contact with the exterior surface, resulting in a thin or wiped film.
Rather than an internal condenser, wiped film evaporators also work well with external condensers, which would be a short path distillation design. External condensers are an excellent system for solvent recovery or devolatilization.
Short Path Distillation
A wiped film system and a benchtop short path system function similarly, as there is not much distance from the original evaporating location to where the compound re-condenses in the form of distillate. The drop in pressure between the evaporation and condensation areas creates thermally sensitive compounds, and distillation occurs successfully.
Generally, there are only a few inches of space between the evaporator and the interior condenser. And in the event of a short path wiped film, the condenser inside the evaporation column re-condenses the compound in the distillation process. The vapor only has a short distance to travel as the compound in distillation makes its way from the evaporator wall directly to the condenser in the center.
Components of Thin/Wiped Film Evaporators
Wiped film systems are complex in design and construction. However, each system has a specific set of primary components that contribute to its overall function to accurately and effectively boil at high temperatures. Below is a list of the primary components and how they function within the system:
The body or column of the evaporator is commonly known as the still. This is the location at which the distillation process physically occurs. The still is one of the most complex segments of the entire system and comes with a mechanical wiper, an internal condenser, a feed connector, and two separate runoffs for residue and distillate. Depending on the setup, it could come with an external condenser. The still’s body includes an outer jacket that helps create heat for distillation.
In almost all systems, there is a pumping mechanism between the still and the feed supply, which helps maintain flow consistencies. Crude oil then goes through a distillation process inside the evaporator, known as the feed supply. Before distillation occurs, the oil goes through purification and preparation to create optimal yields and consistent results.
Residue and Distillate
The end results of a wiped film process are one of two outcomes—residue or distillate. In most cases, there are pumping components at the discharge points for residue and distillate. The pumping components create a continuous feeding system, which is why most wiped film systems have an advantage over traditional batch systems.
A distillate occurs after a specific boiling point creates a purified compound. This is usually the goal compound, while a residue is more the leftovers from the distillation. Any feed components that did not evaporate contain micro amounts of the goal compound. Often, the residue is a waste product and is salvageable for other purposes.
Vacuum System and Cold Trap
An essential part of the entire wiped film operation is the vacuum system. This is the segment that allows distillation to happen at low temperatures. Compounds evaporate in a vacuum at decreased temperatures far better than atmospheric pressure.
A vacuum system typically has at least one, but sometimes multiple, vacuum pumps, in addition to a cold trap or secondary condenser after the still. A cold trap will catch leftover vapors or soft compounds that can reach beyond the interior or exterior condenser before making it to the vacuum system. This plays a significant role in increasing the longevity of a vacuum pump and maintaining the vacuum’s levels.
Wiped film distillation systems can differ due to construction and functionality. When you conduct research for a system, it’s essential to understand the main parts to identify the performance needs quickly, as well as estimate how much it could cost. It’s worth noting that depending on the system, there are several pieces and parts for installation. But understanding the core components help you clearly define your needs.
A high-value system with an intricate design can increase your overall processing speeds and decrease the footprints compared to a batch system. They run continuously, distill at high-boil values, and break down thermally-sensitive compounds better than most other distillation systems.
Hopefully, the process is easier to grasp with the help of our complete guide to wiped film evaporators. Though each system has complex instrumentation and piping, each operation shares a few components that effectively and efficiently create a thin or wiped film and properly distill compounds.
Contact Beaker & Wrench today for a complete turnkey distillation kit. We can answer all your questions and provide the best knowledge to support your distillation operation needs.