In a biogas power plant, a large amount of recoverable energy is discharged through the engine exhaust gas. Instead of releasing this heat directly to the atmosphere, a finned tube exhaust gas heat exchanger can be installed behind the biogas engine to recover waste heat and generate useful hot water. This solution improves the total energy efficiency of the engine system and helps reduce fuel waste, operating cost, and carbon emissions.
For this project, the biogas engine capacity is approximately 1053 kW, and the required heat exchanger capacity is 460 kW. The exhaust gas enters the heat exchanger at about 490°C and is cooled to a minimum outlet temperature of 180°C. The exhaust gas flow rate is 5634 kg/h, with a maximum available gas-side pressure drop of 40 mbar. The recovered heat is transferred to water, with water entering the heat exchanger at 60°C and leaving at up to 160°C. The water flow rate is 4.7 m³/h, and the available water-side pressure drop is 300 mbar.
A finned tube heat exchanger is very suitable for this application because exhaust gas has a much lower heat transfer coefficient than water. By using finned tubes on the gas side, the heat transfer surface area is greatly increased, allowing efficient heat recovery within a reasonable equipment size. The hot exhaust gas flows across the finned tube bundle, while water flows inside the tubes and absorbs the recovered heat to produce high-temperature hot water.
For biogas engine exhaust, the material and structure of the heat exchanger must be selected carefully. Although the stated sulphur content is low, with a maximum of 7 ppm, the design should still consider corrosion risk, exhaust gas condensation, and long-term fouling. Keeping the exhaust gas outlet temperature not lower than 180°C is a practical design requirement because it helps avoid low-temperature condensation and acid corrosion inside the exchanger and exhaust duct.
The heat exchanger can be designed with high-temperature resistant finned tubes, a reinforced casing, thermal insulation, inspection doors, drain connections, and flanged inlet and outlet connections. Depending on the exhaust composition and site requirement, stainless steel tubes or corrosion-resistant materials can be selected for better service life. The tube bundle should also allow easy cleaning, because engine exhaust may contain fine carbon particles or deposits after long operating periods.
On the water side, the system is designed to produce hot water up to 160°C, so it should be used in a properly pressurized closed water circuit. The final design pressure, safety valve setting, expansion tank selection, pump head, and control system should be confirmed before manufacturing. Temperature sensors, bypass control, water flow protection, and exhaust gas temperature monitoring are recommended to protect both the heat exchanger and the engine exhaust system.
This type of exhaust gas heat recovery unit can be used for many heating demands in biogas plants, including digester heating, process hot water, building heating, sludge drying, absorption chiller driving heat, or other industrial thermal loads. By recovering 460 kW of exhaust heat, the plant can significantly improve the overall utilization of the biogas engine and reduce the need for separate boilers or auxiliary heating equipment.
Vrcoolertech can customize the finned tube exhaust gas heat exchanger according to the actual engine model, exhaust gas flow rate, inlet and outlet temperature, water temperature, pressure drop limit, installation space, material requirement, and maintenance access. For this biogas engine project, the key design points are 460 kW heat recovery capacity, 490°C exhaust gas inlet temperature, 180°C minimum exhaust outlet temperature, 60–160°C hot water generation, 40 mbar gas-side pressure drop, and 300 mbar water-side pressure drop.
A well-designed finned tube heat exchanger is not only a waste heat recovery device. It is an important part of the biogas plant energy system, helping the owner convert engine exhaust heat into valuable hot water while improving plant efficiency and long-term operating economy.
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发表于：2026-9-15 09:16:37
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