1. Sources and Characteristics of Waste Heat from Seafood and Aquatic Products Drying
Seafood and aquatic products (such as shrimp, fish, shellfish, etc.) are typically dried using hot air drying equipment, with heat sources primarily consisting of coal-fired, gas-fired boilers, or electric heating systems. The drying process generates a large amount of high-temperature, high-humidity exhaust gas (flue gas), with temperatures typically ranging from 50-100°C, containing significant sensible heat and latent heat:
Sensible Heat: The heat inherent in the high-temperature flue gas itself.
Latent heat: The heat released by the condensation of water vapor in the flue gas. Due to the high moisture content of seafood, the proportion of latent heat is particularly significant.
Exhaust gas characteristics: High humidity (containing a large amount of water vapor), may contain salts or organic matter, which can cause equipment corrosion or scale buildup on heat exchanger surfaces.
If these exhaust gases are directly emitted, not only will thermal energy be wasted, but thermal pollution and wet pollution will also increase, affecting the environment.
2. Features of the BXB Plate Heat Exchanger
The BXB plate heat exchanger is a highly efficient, compact heat exchange device widely used in industrial waste heat recovery, particularly suitable for handling high-temperature, high-humidity exhaust gases. Its main features include:
High-efficiency heat exchange: The plate structure provides a large heat exchange area, resulting in high heat transfer efficiency with recovery rates of up to 60-80%.
Compact design: Compared to shell-and-tube heat exchangers, it has a smaller footprint, making it suitable for space-constrained drying equipment.
Corrosion resistance: Stainless steel or titanium alloy plates can be selected to withstand corrosion from salts and organic compounds in seafood drying exhaust gases.
Easy maintenance: The removable design facilitates cleaning to address scaling or deposits in exhaust gases.
Low pressure drop: Minimal fluid resistance reduces system energy consumption.
3. Application of BXB Plate Heat Exchangers in Seafood and Aquatic Product Drying
(1) System Design
Process Flow:
Exhaust Gas Collection: High-temperature, high-humidity exhaust gas (50-100°C) emitted from drying equipment is conveyed through pipes into the hot-side inlet of the BXB plate heat exchanger.
Heat Transfer: The sensible and latent heat in the exhaust gas is transferred through the heat exchanger plates to the cold-side medium (typically cold air or cooling water).
Heat Utilization:
Preheating of Incoming Air: The recovered heat is used to preheat the incoming air to the drying chamber, reducing the energy consumption of the heater.
Hot water production: Heat is transferred to water to produce hot water for equipment cleaning or facility heating.
Dehumidification optimization: After cooling, the exhaust gas's humidity decreases, improving the efficiency of the dehumidification system.
Exhaust gas emission: The cooled exhaust gas (temperature reduced to 40–50°C) is further treated through the dehumidification system before emission, reducing thermal pollution.
Equipment Configuration:
Heat Exchanger Type: BXB plate heat exchangers are selected, with stainless steel 316L or titanium alloy plates recommended to prevent salt corrosion.
Plate Design: Corrugated plates are used to enhance turbulence, improve heat transfer efficiency, and reduce scaling.
Auxiliary Systems: Equipped with exhaust gas filtration devices (to remove dust and organic compounds) and an automatic cleaning system to extend the heat exchanger's lifespan.
(2) Working Principle
Heat from the exhaust gas is transferred to the cold-side medium through the metal plates of the plate heat exchanger. The narrow channels between the plates enhance heat transfer efficiency.
During the heat exchange process, part of the water vapor in the high-temperature, high-humidity exhaust gas condenses, releasing latent heat and further improving heat recovery efficiency.
The cold-side medium (such as air or water) absorbs the heat, increasing its temperature, and can be directly used for drying preheating or other process requirements.
(3) Application Scenarios
Preheating of Incoming Air: Recovering exhaust gas heat to heat fresh incoming air for drying rooms reduces heat source consumption.
Hot Water Supply: Utilizing recovered heat to produce 40-60°C hot water for cleaning seafood processing equipment or providing hot water for industrial use.
Dehumidification Optimization: Reducing exhaust gas humidity through cooling and condensation improves dehumidification efficiency and enhances drying performance.
4. Benefit Analysis
Energy Conservation and Emission Reduction: The BXB plate heat exchanger can recover 50-80% of exhaust gas heat, reducing drying energy consumption by 20-40%, and decreasing fuel consumption and CO2 emissions. For example, recovering 60% of residual heat can significantly reduce energy costs per ton of seafood processing.
Economic Benefits: By reducing fuel and electricity consumption, equipment investment typically recovers costs within 1-2 years.
Environmental Benefits: Lowering exhaust gas temperature and humidity reduces thermal and moisture pollution, meeting environmental protection requirements.
Product Quality: Maintaining stable drying temperatures prevents overheating or excessive humidity, enhancing the quality of seafood drying.
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