Industrial drying methods: How to choose and use the right one

Industrial drying methods

Industrial drying methods are selected according to the characteristics of the product, quality requirements and drying efficiency.

Overview of industrial drying methods

Basic Definition and Principles of industrial drying methods

Industrial drying is the process of removing moisture from materials using heat energy and various methods to evaporate water. The main purpose is to reduce the water content in the product, which helps with longer storage or preparation for further production processes.

The basic principles of the drying process include:

  • Heat Transfer: Provides thermal energy to heat the material and the water in the material.
  • Evaporation: Water moves from liquid to vapor.
  • Mass transfer: Steam moves from the inside to the surface of the material and then to the surrounding environment.

Classification of industrial drying methods

Helps increase drying efficiency and reduce drying time
Helps increase drying efficiency and reduce drying time

Industrial drying methods can be classified according to various criteria. Here are some common classifications:

By heat transfer method:

  • Convection drying: Uses a stream of hot air to transfer heat and bring moisture away from the material.
  • Thermal Conductive Drying: Heat is transferred directly from the hot surface to the material.
  • Radiation drying: Uses radiant energy (such as infrared) to heat the material.

By operating mode:

  • Intermittent drying (in batches): Materials are dried in separate batches.
  • Continuous drying: The material is fed in and out of the drying equipment continuously.

According to working pressure:

  • Normal pressure drying: Takes place at atmospheric pressure.
  • Vacuum Drying: Use a pressure lower than atmospheric pressure.

According to the special method:

  • Spray drying: The material is sprayed into small droplets into a stream of hot air.
  • Sublimation drying: The water in the frozen material is directly sublimated from the solid state to the vapor.
  • Microwave drying: Uses high-frequency electromagnetic waves to heat the material from the inside.
  • Lyophilization: Combine freezing and sublimation to remove water.

By device type:

  • Fluidized bed drying: The material is floated in a stream of hot air.
  • Rotary Drum Drying: The material is dried in a rotating drum through which hot air flows through.
  • Conveyor drying: The material placed on the conveyor belt moves through the drying zone.

Each drying method has its own advantages and disadvantages, suitable for different types of materials and production requirements. Choosing the right drying method depends on many factors such as the properties of the material, product quality requirements, energy efficiency, and investment costs.

Popular Industrial Drying Methods

Convection drying method

Principle: Uses hot air flow to transfer heat and bring moisture away from the material.


  • Effective with a wide variety of materials.
  • The temperature and air flow rate can be adjusted.
  • Popular in many industries.

Application: Drying food, wood, paper, pharmaceutical.


  • Flexible, applicable to a variety of materials
  • Easy to adjust and control drying parameters (temperature, wind speed)
  • The initial investment cost is relatively low
  • Can dry large volumes Suitable for both intermittent and continuous drying


  • Low energy efficiency due to heat loss into the environment
  • May cause deformation of the surface structure of some sensitive products
  • Uneven temperature in the drying chamber, which may result in uneven drying products
  • Drying time may be extended with some materials

Thermal Conductive Drying Method

Materials are quickly dried by a stream of hot air
Materials are quickly dried by a stream of hot air

Principle: Heat is transferred directly from the hot surface to the material through contact.


  • Effective with thin or powdery materials.
  • More energy efficient than convection drying.
  • Can be combined with pressure to increase efficiency.

Application: Drying paper, fabric, thin films.


  • High energy efficiency due to direct heat transfer
  • Good temperature control, little influence on product structure
  • Suitable for thin or powdery materials
  • Fast drying speed with thin materials


  • Only suitable for certain types of materials
  • May cause cracking or deformation with some heat-sensitive materials
  • The initial investment cost may be higher than convection drying
  • Difficult to apply to thick materials or complex structures

Radiation drying method

Principle: Uses radiant energy (usually infrared) to heat materials.


  • Heat is transferred directly into the material without the need for an intermediate medium.
  • Effective with flat or irregular surfaces.
  • The temperature and drying time can be precisely controlled.

Application: Drying paint, printing ink, drying wood, metal surfaces.


  • High efficiency with flat surfaces, less heat loss
  • Retains the color and flavor of the product well
  • Precise control of temperature and drying time
  • Fast drying speed with surface


  • May be uneven with thick or heterogeneous material
  • High initial investment cost
  • May cause surface fire if not well controlled
  • Significantly reduced efficiency with highly reflective materials

Vacuum Drying Method

Principle: Drying in a pressure environment lower than atmospheric pressure.


  • Reduce the boiling point of water, suitable for heat-sensitive materials.
  • Increase the evaporation rate and reduce the drying time.
  • Better product quality protection.

Application: Pharmaceutical drying, frozen food, electronic components.


  • Energy savings due to reduced boiling point of water
  • Preserve good product quality, retain taste and color
  • Suitable for materials sensitive to high temperatures
  • Faster drying speed than conventional drying at the same temperature


  • High investment and operating costs due to the need for vacuum forming equipment
  • Consumes energy to maintain low pressure
  • May change the structure of some products
  • Difficult to apply to large-scale production

Lyophilization method

Principle: Combine freezing and sublimation to remove water.


  • Retains the original shape and structure of the product.
  • Preserve quality, taste, and nutritional value.
  • High cost and long drying time.

Application: Drying of high-end food, pharmaceuticals, biological specimens.


  • Preserve the best product quality, keep the same structure
  • Retains most of the nutritional and bioactive ingredients
  • The product has good rehydration ability
  • Suitable for high-value, heat-sensitive products


  • Investment and operating costs are very high
  • Highest energy consumption in drying methods
  • Lowest drying speed, long drying time
  • Low productivity, not suitable for large-scale production

Criteria for choosing suitable industrial drying methods

The material is continuously guided through the drying chamber
The material is continuously guided through the drying chamber

Characteristics of the material to be dried

  • Initial humidity and final humidity requirements
  • The size and shape of the material
  • Sensitivity to heat
  • Physical and chemical properties (e.g., heat resistance, mechanical strength)


  • Heat-sensitive materials (such as pharmaceuticals): vacuum drying or lyophilization should be chosen.
  • Powder or granular materials: suitable for fluidized bed drying or spray drying.
  • Thin sheet material: thermal conductive drying or radiation drying can be used.

Product quality requirements

  • Keep the structure and shape the same
  • Preserve color, taste, and nutritional ingredients
  • Uniformity of the product after drying
  • Ability to rehydrate (if needed).


  • High structural preservation requirements (as in frozen food drying): freeze-drying should be chosen
  • It is necessary to preserve color and taste: vacuum drying or radiation drying can be used
  • High uniformity requirements: fluidized bed drying or spray drying can be good choices.

Production Scale

  • Required output
  • Continuity of the production process
  • Future scalability


  • Small-scale, batch production: cabinet drying, vacuum drying can be used
  • Large-scale, continuous production: suitable for conveyor drying, rotary drum drying, spray drying
  • Need to be flexible in production: convection drying can be a good choice due to its versatility

Environmental conditions and available energy

  • Available energy sources (electricity, gas, fossil fuels)
  • Climatic and environmental conditions
  • Requirements for environmental protection
  • Energy costs


  • Areas with cheap electricity: radiation drying or microwave drying may be considered
  • High energy saving requirements: heat pump drying or solar drying can be good options
  • Areas with hot, dry climates: you can take advantage of natural drying or solar drying

Instructions for the use of effective industrial drying methods

Prepare ingredients before drying

Cleaning and sorting:

  • Remove impurities, foreign objects, and damaged parts
  • Sorting by size, doneness (for food) to ensure uniform drying

Preliminary handling:

  • Cut, slice or crush to increase the contact surface area
  • Blanching fruits and vegetables to inactivate enzymes and retain color
  • Chemical treatment (if necessary) such as immersion in an antioxidant solution

Checking and adjusting humidity:

  • Measure the initial moisture content of raw materials
  • Pre-drying if the humidity is too high (e.g. to drain)

Arrangement of raw materials:

  • Spread evenly on a tray or conveyor, avoiding piling up
  • Ensure the spacing between batches of ingredients so that air/heat flows through evenly

Adjust the drying parameters accordingly

  • Temperature: Determine the optimum temperature based on the type of raw material and drying method
  • Set the temperature regime in stages (e.g., high at the beginning, descending towards the end)
  • Continuous temperature monitoring and adjustment during drying


  • Estimation of drying time based on raw material characteristics and final moisture requirements
  • Divide into drying stages as needed (e.g. fast drying initially, then slow drying)
  • Adjust the time based on the results of the periodic humidity test

Airflow rate (for convection drying):

  • Set the right wind speed to optimize the evaporation process
  • Adjust the wind speed according to each drying stage if necessary
  • Ensure even airflow throughout the drying chamber

Air Humidity:

  • Inlet air humidity control (use a dehumidification system if necessary)
  • Monitor the output air humidity to evaluate drying efficiency
  • Adjust the ventilation system to maintain optimal humidity

Special parameters (depending on the drying method):

  • Pressure in vacuum drying
  • Radiation intensity in radiation drying
  • Surface Temperature in Thermal Conductive Drying

Contact Information


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