Longan Drying Case

I.Project Background

Longan, a specialty fruit of southern China, demands extremely high quality and taste during drying. Traditional drying methods, such as air drying or coal-fired drying, are susceptible to weather conditions, consume high energy, and cause significant pollution. To improve longan drying efficiency and reduce energy consumption, a food processing company introduced an air-energy heat pump drying system equipped with a 7-meter multi-layer mesh belt dryer, achieving intelligent, energy-saving drying.

II.Customer Requirements

Energy saving and environmental protection: Avoiding highly polluting heat sources such as coal and oil, complying with environmental protection policies.

Efficient and stable: Ensures even drying of longan, achieving a golden color, plump flesh, and a moisture content that meets standards (≤18%).

Automated control: Reduces manual intervention, precisely controls temperature and humidity, and improves production efficiency.

III. Solution

1.Equipment Configuration

Heat Source System: 25P Air-to-Air Heat Pump Unit (Heating Capacity ≥ 75kW, COP ≥ 3.5)

Drying Unit: 7-meter multi-layer mesh belt drying room (304 stainless steel mesh)

Control System: PLC intelligent temperature and humidity control, supporting staged adjustment (preheating → high-temperature drying → uniform humidity distribution → cooling)

2.Drying Process

Phase 1 (Preheating): Temperature set to 50°C ± 2°C for 1 hour to remove surface moisture.

Phase 2 (Main Drying): Temperature raised to 60°C ± 2°C for 12 hours, uniform dehydration.

Phase 3 (Uniform Humidification): Temperature lowered to 55°C for 2 hours to balance internal and external moisture.

Total Drying Time: Approximately 15 hours (conventional drying requires 3-5 days).

3.Energy-Saving Advantages

Air-to-Air Heat Pumps save over 60% more energy than electric heating and reduce carbon emissions by 90% compared to coal.

The waste heat recovery system recycles exhaust heat, improving overall energy efficiency by 20%.

IV.Operational Results

Improved Quality: The finished dried longan has a uniform color, is free of burnt or cracked products, and maintains a high sugar content.

Production Capacity Meets Target: A single batch processes approximately 2,000 kg of fresh longan, producing over 500 kg of dried longan daily.

Economic Benefits: Compared to traditional coal-fired drying, the drying cost per ton of longan is reduced by approximately 40%.

V.Customer Feedback

Customers highly praised the stability and energy efficiency of the air-source drying equipment, particularly its intelligent control system, which significantly reduces manual operation complexity. Future plans include expanding production and extending the application to other agricultural product processing, such as lychees and goji berries.

This case demonstrates the significant advantages of air-source heat pumps in the longan drying industry, balancing environmental protection with high efficiency, and providing a new direction for sustainable development in the agricultural product processing industry.