07/04/2026
🔧 1. Basic Drying Principle
The operation relies on two key processes:
Heat transfer → Warm air heats the grain
Mass transfer → Moisture inside the grain evaporates and is carried away by airflow
🌬️ 2. Airflow System (Convection Drying)
A fan/blower forces air through the grain mass.
Hot air passes through grain layers
Moisture evaporates from the grain surface
Wet air is expelled out
👉 This is called forced convection drying
🔥 3. Heating System
The air is heated before entering the grain chamber using:
Diesel burner
Gas burner
Biomass furnace (common in Africa)
Electric heaters (less common)
Important:
Temperature must be controlled:
Too high → cracks or damages grain
Too low → inefficient drying
🔄 4. Grain Movement (Mixing Principle)
To ensure uniform drying, mobile dryers use:
Batch mixing (recirculation dryers)
Grain is circulated repeatedly through the drying chamber
OR
Continuous flow
Grain moves slowly from top to bottom
This prevents:
Overdrying at the bottom
Wet pockets at the top
💧 5. Moisture Gradient Principle
Moisture moves from inside the grain kernel to the surface:
Inner moisture migrates outward
Surface moisture evaporates
Process repeats until target moisture is reached (e.g. 13–14% for maize)
🌡️ 6. Temperature & Moisture Control
Key controls include:
Air temperature sensors
Moisture meters
Adjustable airflow rates
Proper control ensures:
Grain quality preservation
Energy efficiency
Avoidance of mold or aflatoxin risks
🚛 7. Mobility Advantage
Unlike fixed dryers, mobile dryers:
Can be transported to farms
Reduce transport of wet grain
Lower post-harvest losses
Ideal for rural or decentralized operations
⚙️ 8. Typical Components
A mobile dryer usually includes:
Hopper / intake
Drying chamber
Burner or furnace
Blower fan
Augers or elevators (for movement)
Control panel
Trailer chassis (for mobility)
📊 9. Drying Cycle (Simple Flow)
Load wet grain
Heat air
Blow hot air through grain
Evaporate moisture
Recirculate or discharge
Cool grain before storage