In the field of food processing, drying is a critical step that directly affects product texture, shape, safety, and shelf life. As one of the core pieces of equipment, the design, manufacturing, and application philosophy of food grade dryer production lines reflect a strong commitment to food quality and safety. A complete food-grade dryer production line is far more than a simple heating and dehydration device; it is a systematic engineering solution integrating thermodynamics, fluid mechanics, materials science, and automation control. Its purpose is to provide scientific, gentle, uniform, and efficient drying solutions tailored to various food raw materials. Below is an introduction to the dryer production line recently provided by our company for a Malaysian client specifically for drying onions.
Onions are fed via a feeding conveyor to the top of the dryer and enter the inlet, then evenly fall onto a 304 stainless steel mesh belt drive. The mesh belt operates continuously, and dry hot air is introduced from the bottom of the belt (supply air temperature 75°C). The moisture in the material absorbs heat and continuously vaporizes, producing a large amount of saturated water vapor that is carried back to the top of the mesh belt. The hot air passes through a dust filter bag to trap dust and fine particles, then recirculates from the top back to the evaporator (return air temperature 48–56°C). Through condensation dehumidification, the water vapor is collected and discharged. At this point, the air with lower moisture saturation is reheated by the condenser to 75°C, becoming dry, high-temperature hot air that is sent back to the bottom of the mesh belt, entering a periodic cycle to achieve material drying and dehydration. The mesh belt speed is controlled by a variable-frequency drive, allowing adjustable material residence time.
Design Performance Features of the Low-Temperature Onion Surface Water Dryer
Safe system operation: no explosion risk, no need for nitrogen purging.
Durable: The mesh belt is made of 304 stainless steel, with minimal mechanical wear during operation, providing a service life of 15–20 years or more.
Intelligent: Fully automatic operation with PLC + touch screen intelligent control, easy operation, and significant labor savings.
Adjustable output moisture content: can be set arbitrarily (10%–60%).
Innovative technology: Uses a patented low-temperature dehumidification technology, achieving controllable air humidity as low as below 10%, resulting in faster drying efficiency.
Energy-saving: Independent layered system meets the rapid dehydration requirements of materials, with a short low-temperature drying cycle.
Low-temperature heating and sterilization: Drying temperature of 75°C for 90–120 minutes, effectively killing over 90% of bacteria and reducing the release of harmful gases.
Small footprint.
No waste heat emission: Uses a closed-loop air circulation system with no waste heat or exhaust gas emissions, and no secondary pollution.
Advanced Intelligent Control System:
The control system of the low-temperature onion drying production line uses a programmable logic controller (PLC) specifically designed for industrial environments. It features intuitive operation, high efficiency, safety, reliability, simple use, easy maintenance, and strong scalability. The low-temperature dryer uses the PLC and touch screen to control belt conveyors, screw conveyors, mesh belt conveyors, cutting machines, circulating fans, cooling water valves, heat pumps, etc., and supports variable frequency speed control. It is equipped with alarms for air temperature, humidity, material shortage, and faults. The system uses high-quality electrical control components to enable automatic/manual operation modes. Standard signals collected by on-site online detection instruments are centrally processed, and control signals are output. When indicators such as circulating air temperature and humidity exceed set values, the system can automatically trigger alarms and take corresponding actions. This allows for automatic calculation and feedback control of data not directly displayed by many on-site instruments, comparing with set values to determine whether the system is operating normally.
