How does vacuum tray dryer work?


Vacuum tray dryers are an essential piece of equipment widely used in the pharmaceutical, chemical, food, and cosmetic industries. These dryers provide an efficient and reliable method for drying a variety of materials, including powders, flakes, granules, and paste-like substances. By creating a vacuum environment, these dryers can effectively remove moisture and other volatile substances from the product, allowing for optimal drying results. In this article, we will explore the working principles and processes of a vacuum tray dryer in detail.

How does a vacuum tray dryer function?

A vacuum tray dryer operates by utilizing a vacuum pump to create a low-pressure environment within the drying chamber. This vacuum environment significantly lowers the boiling point of water or other volatile materials, enabling them to vaporize at lower temperatures. The dryer consists of a rectangular chamber with multiple trays stacked vertically, where the material to be dried is spread evenly on these trays.

The heating process

The first step in the operation of a vacuum tray dryer is the heating phase. The heating source, commonly an electric heater, steam radiator, or hot oil circulation system, is used to elevate the temperature within the chamber. As the temperature rises, the material on the trays begins to absorb the heat, causing the moisture or volatile substances to evaporate.

During this phase, the vacuum pump continuously removes the evaporated moisture or volatile substances from the drying chamber. This removal is essential as it prevents the reabsorption of the evaporated matter and maintains the low-pressure environment necessary for effective drying. The vacuum pump also aids in speeding up the drying process by lowering the boiling point, ensuring efficient moisture removal even at lower temperatures.

The vacuum phase

After the heating phase, the vacuum phase follows. In this stage, the vacuum pump creates a vacuum by removing air and other gases from the chamber. Creating a vacuum is critical as it further lowers the boiling point of moisture or volatile substances, facilitating faster evaporation rates.

As the vacuum pump eliminates air molecules, the pressure within the chamber decreases significantly. This reduction in pressure causes the moisture trapped within the product to convert into vapor and escape from the material's surface. With proper circulation and uniform heating, the product's moisture content decreases over time.

Circulation of hot air

Proper air circulation is essential in a vacuum tray dryer to ensure uniform drying and prevent product degradation. To achieve optimal air circulation, the dryer is equipped with a fan or blower system. This system circulates the heated air within the chamber, distributing it evenly across the trays and preventing temperature variations between different sections of the dryer.

A well-designed vacuum tray dryer also incorporates adjustable air vents to control the air intake and exhaust. This allows operators to fine-tune the drying process by regulating the airflow and optimizing heat distribution. The control of these parameters ensures that the product dries thoroughly while preserving its quality attributes.

The cooling phase

Once the drying process is complete, the cooling phase begins. In this stage, the heating source is turned off, and ambient air is gradually introduced into the chamber. Cooling the product helps prevent moisture reabsorption and ensures the material's stability before further processing or packaging.

During the cooling phase, the vacuum pump continues to operate, albeit at a reduced capacity. It aids in removing any remaining traces of vapor and maintaining the low-pressure environment for a controlled cooldown. This step aims to minimize the chances of condensation and subsequent moisture absorption by the dried material.

Advantages of vacuum tray dryers

1. Efficient drying:

Vacuum tray dryers offer efficient drying capabilities due to the use of a vacuum environment. The reduced boiling points allow for quicker drying times and minimal degradation of heat-sensitive materials.

2. Consistent product quality:

The uniform air circulation and controlled drying parameters in a vacuum tray dryer ensure that all sections of the product receive equal heat, resulting in consistent drying and maintaining product quality attributes.

3. Preservation of product integrity:

The low temperature and vacuum environment minimize the risks of product degradation and maintain the integrity of temperature-sensitive materials during the drying process.

4. Flexibility in handling various materials:

Vacuum tray dryers are versatile and can handle various types of materials, including powders, flakes, granules, and paste-like substances. Their adaptability makes them suitable for a wide range of industries.

5. Cost-effective operation:

The use of a vacuum environment reduces the required energy input for drying, leading to lower operational costs when compared to conventional drying methods.


Vacuum tray dryers provide an efficient and reliable solution for drying a wide range of materials in industries such as pharmaceuticals, chemicals, food, and cosmetics. By creating a low-pressure environment, these dryers facilitate faster evaporation, leading to shorter drying times and reduced degradation. With proper air circulation, controlled drying parameters, and the ability to handle various materials, vacuum tray dryers offer consistent and high-quality drying results. Their cost-effective operation and preservation of product integrity make them a valuable asset for industrial applications. Whether it's removing moisture from powdered pharmaceuticals or drying food products, vacuum tray dryers play a crucial role in achieving optimal drying outcomes.


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