Short Path Distillation Unit Theory, Design, and Operation

Short Path Distillation Unit: Theory, Design, and Operation

In the world of chemical processing and purification, a powerful technique known as short-path distillation has emerged as a game-changer. This method allows for the separation and purification of liquids with exceptional precision and efficiency, making it an indispensable tool in various industries. In this blog post, we will explore the theory behind a short path distillation unit, discuss the key design considerations, delve into the different types of units available, and explore the best practices for operating them effectively.


What is a short path distillation unit, and how does it work?

A short path distillation unit is specialized equipment used to separate and purify liquids based on their boiling points. It employs the principles of distillation, a process that involves the vaporization and subsequent condensation of a liquid mixture to separate its components. What sets short-path distillation apart is the use of a short-path evaporator, which minimizes the distance between the heated surface and the condenser, thereby reducing the residence time and minimizing the chance of thermal degradation. The short path distillation unit (SPDU) operates on a similar principle to a thin film evaporator, with the key difference being the presence of an internal condenser within a rotor cage assembly.

The feed is introduced into the unit from the top and evenly distributed onto the inner surface of the shell, forming a thin film. A heating medium circulates through the jacket, causing the volatile components in the feed to evaporate. The vapors generated move across the rotor and condense on the internal condenser. This short vapor path eliminates pressure drop, enabling high vacuum evaporation at pressures as low as 0.001 mbar(a).

The distilled product and residue are collected separately through dedicated outlets.

Key Features:

  • Operating pressure as low as 0.001 mbar(a), allowing distillation at lower temperatures to prevent degradation.
  • Enables the distillation of highly boiling components with the combination of high vacuum and high heating temperatures.
  • The short residence time of a few seconds.
  • Single-pass evaporation.
  • Excellent turn-down capability.
  • Minimal product hold-up.
  • Metal blades provide greater flexibility than graphite rollers when operating at high temperatures.


What are the key design considerations when building a short path distillation unit?

Designing a short path distillation unit requires careful consideration of several key factors. First and foremost is the selection of appropriate materials that can withstand the high temperatures and corrosive nature of certain liquids. Stainless steel is commonly used for heat resistance and chemical compatibility.

Another critical design consideration is the choice of the vacuum system. Maintaining a low-pressure environment is essential to prevent the unwanted degradation or volatilization of the target compounds. An efficient vacuum system ensures optimal performance and product quality. Additionally, the condenser design plays a crucial role in achieving effective separation. Various condenser types offer different advantages in terms of heat transfer efficiency and ease of cleaning.

The key factor of SPDU is the selection of an entrainment separator; which drives results for color in the distillate. If distillate is the product then this is a key design aspect. 


What are the different types of short path distillation units available, and what are their respective advantages and disadvantages?

Short path distillation units are wiped film units.

Wiped film distillation units consist of a rotating wiper blade that creates a thin film of liquid on the heated surface, promoting efficient heat transfer and minimizing residence time. This design enables high evaporation rates, making it suitable for processing heat-sensitive materials. However, it may require more power and can be susceptible to fouling.


How is a short path distillation unit typically operated, and what are some best practices for achieving optimal results?

Operating a short path distillation unit requires attention to detail and adherence to best practices. The following steps outline a typical operational procedure:

  • Prepare the unit: Ensure that all components are clean and properly installed, including the feed tank, SPDU, condenser, and collection receivers. Verify the vacuum system is functioning correctly.
  • Heat the system: Gradually increase the temperature to the desired range for distillation. Take care to avoid rapid temperature changes that could cause thermal stress.
  • Adjust the vacuum: Set the vacuum level to maintain the desired pressure, considering the boiling points of the target compounds. Monitor and adjust as necessary to optimize separation efficiency.
  • Collect the distillate: As the liquid mixture vaporizes and condenses, collect the purified product in designated receivers. Monitor the temperature and adjust parameters as needed to achieve desired results.


To achieve optimal results, here are some best practices to consider:

  • Use standardized starting materials to ensure a consistent feed.
  • Monitor and control temperature and pressure parameters carefully.
  • Regularly inspect and clean the unit to prevent fouling and maintain efficiency.
  • Properly handle and dispose of any hazardous or toxic materials involved in the distillation process.

Short-path distillation is an effective method for purifying liquids and isolating specific compounds. Its ability to achieve high separation efficiency, handle temperature-sensitive materials, and minimize thermal degradation has made it an invaluable tool in various industries, including pharmaceuticals, essential oils, and chemical processing. By understanding the theory, design considerations, different types of units available, and operating best practices, one can harness the power of short-path distillation to obtain pure, high-quality products. 

Want to elevate your distillation process to new heights? 

Reach out to Economy Process Solutions and tap into our expertise in short-path distillation units. Let our team guide you toward achieving optimal results and maximizing your product purity. Connect with us now!

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