Agricultural product dryer: Structure and principle of operation

Agricultural product dryer: Structure and principle of operation

The use of agricultural product dryer brings many advantages such as helping to preserve agricultural products for a longer time, preventing spoilage, and being able to dry many different types of agricultural products,…

Overview of Agricultural Product Dryer

Definition of agricultural product dryers

An agricultural product dryer is a device specifically designed to remove moisture from agricultural products such as grains, seeds, fruits, vegetables, and other agricultural products. The main purpose of the drying process is to reduce the water content in the product for long-term storage, reduce the shipping volume, and prepare for the next processing process.

Agricultural product dryers work by creating an environment with controlled temperature and humidity, allowing the water in the product to evaporate efficiently while maintaining the quality and nutritional value of agricultural products.

Common types of agricultural product dryers

Batch dryer:

  • Operation in batches, suitable for small and medium-sized
  • For example, cabinet dryer, tray dryer, silo dryer

Continuous dryer:

  • Continuous operation, suitable for large scale
  • For example, conveyor dryers, tower dryers, rotary drum dryers

Solar Dryer:

  • Using solar energy for drying, eco-friendly
  • Can be knockout or indirect

Heat Pump Dryer:

  • Using heat pump technology to reuse heat, save energy
  • Suitable for high-temperature sensitive products

Fluidized bed dryer:

  • Use hot air to create a “boiling” layer of seeds, drying evenly
  • Suitable for granules and small granular products

Microwave dryer:

  • Using electromagnetic waves for drying, short drying time
  • Suitable for some special agricultural products

Advantages of using agricultural product dryer

Preserving and improving the quality of agricultural products
Preserving and improving the quality of agricultural products
  • Extend storage time, and reduce damage caused by microorganisms
  • Preserve the quality and nutritional value of the product
  • Reduce shipping volume, save logistics costs
  • Allows preservation of products for sale at times of high prices
  • Humidity control, consistent quality assurance
  • Allows for high-volume drying, meeting the needs of industrial-scale production
  • Adjustable drying parameters (temperature, time, wind speed)
  • Flexibility in adjusting the drying process for each type of product
  • Reduced labor requirements compared to traditional drying methods

Structure of agricultural product dryer

Drying chamber – the main component of the agricultural product dryers


  • Usually in the form of a rectangular box or cylinder
  • Made from heat-resistant and corrosion-resistant materials such as stainless steel
  • There is insulation to reduce heat loss to the environment


  • Varies according to capacity and dryer type
  • It can be from a few cubic meters to hundreds of cubic meters

Internal layout:

  • There are trays or conveyors for placing agricultural products
  • Designed to ensure a steady flow of hot air throughout the product
  • There are feed and discharge outlets


  • Capable of withstanding high pressures and temperatures
  • Designed for easy cleaning and maintenance
  • There is a closed-door system to prevent outside air from entering

Heat supply system in agricultural product dryers

Good control of drying parameters, improve product quality
Good control of drying parameters, improve product quality

Heat source:

  • Resistance: Uses electricity to generate heat
  • Fuel burning: Uses gas, oil, coal, or biomass
  • Heat Pump: Uses the principle of heat pump to generate and reuse heat
  • Solar Energy: Uses direct or indirect solar radiation

Heat exchanger:

  • Helps transfer heat from the heat source to the drying air
  • Usually made of metals with high thermal conductivity such as copper or aluminum

Heat pipes:

  • Distribute hot air evenly throughout the drying chamber
  • Insulated to reduce losses

Thermostatic system:

  • Fuel flow control valve (for combustion system)
  • Power Controller (for electrical systems)

Fan and ventilation system of agricultural product dryer

Main fan:

  • Creating convection airflow in the drying chamber
  • Usually a centrifugal fan or axial fan
  • Capacity varies according to dryer size

Auxiliary fans:

  • Supports gas circulation in specific areas
  • Helps to homogenize temperature and humidity

Air hose:

  • Distribute hot air evenly throughout the drying chamber
  • Adjustable to optimize airflow

Moisture discharge system:

  • Remove moist air from the drying chamber
  • Includes exhaust fan and exhaust pipe

Air filter:

  • Filters dust and impurities from the inlet air
  • Protection of the product and internal parts of the dryer

Controllers and sensors in agricultural product dryer

Central controller:

  • Usually PLC (Programmable Logic Controller) or industrial computer
  • Control and monitor the entire drying process
  • Storage of drying programs for different agricultural products

User interface:

  • Display screen (LCD or touch)
  • Keyboard or buttons for input and adjustment

Temperature sensor:

  • Temperature measurement in the drying chamber and in critical locations
  • Usually use a thermistor sensor or thermocouple

Humidity Sensor:

  • Measuring the humidity of the air in the drying chamber
  • Measuring the moisture content of the product (some advanced dryers)

Flow sensors: Measure the speed and air flow in the system

Pressure Sensor: Pressure monitoring in the drying chamber (especially important in vacuum dryers)

Safety system:

  • Fire and smoke detection sensors
  • Safety switches for doors and moving parts

Data recording system:

  • Storing information about the drying process
  • Allows for later data retrieval and analysis

All of these components work together to create a complete agricultural dryer that has precise control over the drying process, ensuring product quality and energy efficiency.

The principle of operation of the agricultural product dryer

Agricultural product dryer
Agricultural product dryer

Agricultural product dryers work on the principle of blowing continuous convection heat to reduce the water content in agricultural products to the desired level. This process includes the following key steps:

Heat generation process in agricultural product dryer

The heat required for the drying process is provided by various heat sources such as:

  • Fossil fuels: coal, firewood, oil, gas,…
  • Power: use resistance rods or heat pumps.
  • Solar energy: use solar cells to generate electricity.

The heat is transferred to the drying medium through the following methods:

  • Transmission: through the walls, walls of the drying chamber.
  • Convection: through the circulation of hot air.
  • Radiation: infrared.

Hot air circulation mechanism in agricultural product dryer

  • The blower plays an important role in creating a continuous flow of hot air in the drying chamber
  • This hot air will come into direct contact with agricultural products, evaporating water from the surface of agricultural products
  • The speed and direction of the hot air flow affect the drying efficiency and product quality.

The process of removing moisture from agricultural products using an agricultural product dryer

  • The water in agricultural products diffuses from the inside to the surface due to the difference in water vapor pressure.
  • The water on the surface of agricultural products evaporates into the hot air stream. Steam is drawn out of the drying chamber by means of a ventilation system.
  • The drying process takes place continuously until the water content in the agricultural products reaches the desired level.

Temperature and humidity control in agricultural product dryer

The temperature and humidity in the drying chamber need to be strictly controlled to ensure product quality. Automatic or manual control systems are used to regulate temperature and humidity. Some factors to consider when controlling temperature and humidity:

  • The type of agricultural products that need to be dried.
  • The initial water content of agricultural products.
  • Desired product quality.
  • Ambient conditions.

In addition, a number of other factors also affect the performance of agricultural product dryers:

  • The size and shape of the drying chamber.
  • The amount of air circulating in the drying chamber.
  • How to arrange agricultural products in the drying chamber.

Please contact us immediately to receive professional advice and optimal solutions for your needs.

Contact Information


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