Rolled Film vs Short Path Distillation

Rolled Film (RF Series) vs Short Path (KD Series)

The Difference between Rolled Film and Short Path Distillation

To understand the difference between Rolled Film (RF Series) and Short Path (KD Series) distillation, it is important to first understand the basics of how each process works. Both processes are used in chemical engineering to separate components from a mixture, but they do so in different ways. In this article, we will explore the differences between RF Series and KD Series distillation, as well as the advantages of each. Depending on your business needs and the materials you utilize for distillation, you will likely gravitate towards one process or the other. We will help you to have a better understanding of which unit will best suit your distillation demands, and how to move forward in getting set up.

Rolled Film (RF Series) Distillation


A roller based wiped film system has proven it has tremendous advantages in many applications over the years. The roller system consists of a cylindrical “basket”, composed of guide rods on which rollers are fixed. The rollers themselves are made of a glass fiber reinforced PTFE compound. In order to turn the roller assembly, a motor from outside the distillation chamber is utilized. When operating the unit, centrifugal force presses these rollers into the liquid film flowing downwards and thus creating an even thin film along the wall of the evaporator. Since there is no mechanical load on the evaporation surface, scratches and “fouling” are avoided.


In Rolled Film distillation (also known as RF Series distillation), the hot vapors travel through a bridge to the condenser. These condensers are cooled by a stream of chilled water, glycol, or other fluid which cause the vapors to condense and drip back into a collection vessel. Rolled film distillation is usually done under vacuum and is often used to purify materials that are difficult to distill using other methods, such as those with high boiling points or those that decompose at high temperatures. An example for this is that rolled thin film distillation is often used in the pharmaceutical industry to purify active ingredients for drugs.

Who is Rolled Film Distillation Best For?

This type of distillation is especially well-suited for businesses in the food and beverage industry, as well as in the pharmaceutical, cosmetic and chemical industries. Cannabis & hemp also benefit from Rolled Film distillation due to its ability to remove residual solvents and strip terpenes. In cases where a large amount of liquid needs to be produced in a short period of time, rolled film is the optimal choice especially when purity is of the utmost importance. With its condenser located outside of the evaporator, extremely large condensing surface area can be created making it a perfect candidate for chemicals that may be difficult to condense otherwise.

Other Industries – Essential Oil Producers

Rolled Film Distillation is best suited for medium to large scale essential oil producers. The RF Series of rolled film evaporators are an ideal solution for those looking to increase their distillation capacity and efficiency. The larger surface area provided by the rolled film technology allows for faster separation of essential oils from plant materials. This results in higher oil yields and reduced distillation times compared to traditional steam distillation equipment. The stainless steel construction and automated features of the RF Series also make Rolled Film Distillation ideal for busy commercial operations where minimal downtime and low maintenance are important. Overall, if you’re an established essential oil producer looking to scale up your operation, the Chemtech RF Series of Rolled Film Distillation could be the right choice.

Pros of Rolled Film Distillation

  • Ability for larger condenser surface
  • Faster throughput

Cons of Rolled Film Distillation

  • 1-2 orders of magnitude worse vacuum than on Short Path
  • May require higher temperatures

Short Path (KD Series) Distillation

Short path distillation, also known as SPD distillation, gets its name from the short distance that it takes for a liquid to transition from a liquid to a vapor while evaporating and then back to a liquid while condensing. In this method, the condensing of material happens inside of the evaporator, which decreases the size of the vapor cloud that can form, thus allowing for the conservation of vacuum and significantly deeper vacuum levels.


Continuous short path systems include an internal condenser which allows you to have the deepest vacuum possible. The condensing coil or tube bundle is located in the center of the evaporator and usually has a surface area that is equal to the evaporator surface area. The KD Series are great for heat sensitive molecules as they allow for distilling at very high Atmospheric

Equivalent Boiling (AET) but at relatively low temperatures due to the high vacuum levels. The KD Series is intended for continuous feed supply and can be more costly than traditional table top units.


Rollers work by creating an even thin film around the evaporator surface using centrifugal force. A cooling coil condenses the evaporated material back into a liquid and collects it. Using spds (short path distillation systems) with rollers helps with evaporation therefore increasing performance. Rollers utilize a

simple method which does not rely on springs. The evaporator wall generates the vapors as the feed moves by gravity, while being agitated and distributed evenly, down the evaporator wall.

The vapor stream travels a “short path” directly to the condenser which is located within the evaporator chamber. Since the vapor stream is immediately condensed, the short path distillation process precludes the vapor from forming vapor pressure. This allows ultimate pressures of 0.001 mbar to be attained which, in turn, allows heat-sensitive materials to undergo purification at much lower temperatures preventing degradation. It also allows for very high ambient equivalent temperatures to be achieved. Short path distillation in a plant setting is a continuous process.

Who is Short Path Film Distillation Best For?

While this type of unit adds slightly more cost and sophistication to your process, it can be a worthwhile investment due to increased production. Short path wiped film distillation is a process often used to purify or separate temperature-sensitive materials, such as oils and waxes. It also commonly finds applications in the pharmaceutical industry to purify active ingredients for drugs.

Pros of Short Path Series With Rollers

  • Creates an even thin film around the evaporator surface
  • Very short distance between evaporator & condenser
  • Small vapor cloud
  • Really deep vacuum
  • Great for heat sensitive molecules

Cons of Short Path Series With Rollers

  • Adds more cost and sophistication
  • May not work on all fluids
  • Limited space for condenser surface area

Which Distillation Series Is Best For You?

When choosing between Rolled Film (RF Series) and Short Path (KD Series) distillation for your project needs, there are several factors that should be taken into consideration such as cost effectiveness, efficiency levels and scalability requirements for your project. Ultimately though it comes down to understanding which process best suits your specific needs when separating different components from mixtures. You may either find the larger surface area offered by the external condenser offered by the rolled film series advantageous or the internal condenser and its corresponding deeper vacuum offered by the short path series. By understanding both processes you can make an informed decision on which one will work best for your business. If you still have questions, reach out to our team of experts to get individual answers.

Getting Started

When selecting a distillation systems manufacturer, trust Chemtech Services, Inc. for the best in quality systems and customer service. Our systems provide more consistency, higher throughput and easy installation. Get continuous action and increase workflow.

Call us today at (815) 838-4800 to learn more about getting your new distillation system up and running. Our engineers are also available for plant installation, start-up, and training to make sure you can move forward with accuracy and confidence.

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