What is the difference between short path and wiped film evaporator?

2023/10/21

What is the Difference between Short Path and Wiped Film Evaporator?


Introduction:

Evaporators are crucial equipment used in various industries, including pharmaceuticals, food processing, chemical manufacturing, and more. They are used to separate a solvent from a liquid mixture, leaving behind a concentrated form of the desired product. Two commonly used types of evaporators are short path evaporators and wiped film evaporators. In this article, we will explore the differences between these two types of evaporators and highlight their unique features and applications.


Understanding Evaporators:

Evaporators work on the principle of gentle heating to separate the volatile components from a liquid mixture. They utilize the difference in boiling points of the components to evaporate the more volatile substance, leaving behind the less volatile one. This process is commonly used for solvent recovery, concentration of heat-sensitive products, and purification of compounds.


1. Short Path Evaporators:

A short path evaporator, also known as a molecular distillation system, is a compact and effective evaporator design that operates under high vacuum conditions. It features a vertically arranged glass or metal cylinder with a short path distance between the evaporator and condenser. The short path distance minimizes the pressure drop and reduces the chances of product degradation due to prolonged heat exposure.


A. Design and Operation:

The short path evaporator consists of a rotating wiper blade that spreads the liquid mixture into a thin film on the heated inner surface of the cylinder. The evaporator is heated with a heating medium, typically oil or steam, on the outer jacket. The low-pressure environment inside the evaporator prevents thermal degradation of the product, making it suitable for heat-sensitive compounds. The vapor generated is condensed on a separate condenser, where it is collected as the distillate.


B. Applications:

Short path evaporators are commonly used for distillation processes that require the separation of heat-sensitive substances. They find applications in the production of essential oils, high-purity chemicals, pharmaceutical intermediates, and fine chemicals. The short path distillation helps achieve high product purity and is ideal for compounds with low boiling points and molecular weights.


2. Wiped Film Evaporators:

A wiped film evaporator, also referred to as a thin film evaporator, is another popular type of evaporator used for similar applications as the short path evaporator. It operates under low pressure and efficiently handles heat-sensitive and viscous materials. The design of the wiped film evaporator allows for a continuous and uniform film formation, ensuring maximum heat transfer and efficient separation.


A. Design and Operation:

In a wiped film evaporator, the liquid mixture is fed into a heated cylindrical vessel. The vessel is equipped with a rotor that rotates at a high speed, forming a thin film of the mixture on the inner surface of the vessel. The high rotational speed of the rotor creates a wiping action, continuously renewing the liquid film. The generated vapor is withdrawn from the top of the vessel and condensed separately.


B. Applications:

Wiped film evaporators are widely used in various industries, including chemical processing, pharmaceuticals, and food production. They are suitable for removing solvents or concentrating heat-sensitive products in a gentle and efficient manner. These evaporators are particularly effective for the production of CBD distillates, vitamin E purification, and flavor and fragrance extraction.


3. Key Differences between Short Path and Wiped Film Evaporators:

While both short path and wiped film evaporators serve similar purposes, they differ in terms of design, operation, and applications.


A. Design:

Short path evaporators have a vertically arranged cylinder with a short path distance between the evaporator and condenser. Wiped film evaporators, on the other hand, have a rotating wiper blade and a heated cylindrical vessel for continuous film formation.


B. Heat Transfer:

Short path evaporators provide gentle heating with minimal heat exposure, thanks to the short path distance. Wiped film evaporators, with their continuous wiping action, offer excellent heat transfer and efficient separation.


C. Pressure Range:

Short path evaporators operate under high vacuum conditions, while wiped film evaporators typically operate under low vacuum or atmospheric pressure.


D. Application Focus:

Short path evaporators are best suited for distilling heat-sensitive compounds and achieving high product purity. Wiped film evaporators excel in handling viscous materials and continuous processing of delicate products.


E. Scale of Operation:

Short path evaporators are typically used for small to medium-scale production, while wiped film evaporators can efficiently handle large-scale production requirements.


Conclusion:

In summary, both short path evaporators and wiped film evaporators are valuable tools in the field of separation and concentration processes. They have distinct designs and operating mechanisms that suit different applications and requirements. Understanding the differences between these evaporators can help industries choose the most appropriate solution for their specific needs, ensuring efficient and reliable operation while maximizing product quality and yield.

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