Application Background
In biogas treatment systems, gas cooling is required to reduce gas temperature before downstream processing, gas cleaning, compression, or utilization. The gas stream normally contains methane, carbon dioxide, water vapor, and a small amount of oxygen. Because the medium may contain moisture and corrosive components, material selection is critical.
For this application, the customer required one heat exchanger to cool biogas with water as the cooling fluid. The selected design is a full stainless steel brazed plate heat exchanger, without copper, rated for approximately 30 bar pressure class. The exchanger uses stainless steel brazing technology and front/back reinforced clamping plates to improve mechanical strength and pressure resistance.
Design Conditions
| Parameter | Biogas Side | Water Side |
|---|---|---|
| Flow Rate | 814 kg/h | 4500 kg/h |
| Inlet Temperature | 70.4°C | 8°C |
| Outlet Temperature | 25°C | 18°C |
| Maximum Allowable Pressure Drop | 20 kPa | According to hydraulic design |
| Material Requirement | 100% SS316 stainless steel | |
| Design Standard | Designed in accordance with ASME requirements | |
Why Copper-Free Full Stainless Steel Construction Is Used
Standard copper brazed plate heat exchangers are widely used in HVAC and water-to-water applications. However, for biogas cooling, copper is not always the preferred choice because the gas may contain moisture, acidic condensate, sulfur compounds, or other corrosive contaminants depending on the upstream process.
A copper-free full stainless steel brazed heat exchanger eliminates copper from the heat transfer core. The plates and brazing material are stainless steel based, making the unit more suitable for applications where corrosion resistance, cleanliness, and material compatibility are more important than the lowest initial cost.
Heat Exchanger Structure
The selected unit is not a traditional gasketed plate heat exchanger and not a conventional shell and plate unit. It uses a compact plate pack made by stainless steel brazing. The flow channels are formed between corrugated stainless steel plates, creating high turbulence and efficient heat transfer within a very small footprint.
To increase pressure resistance, the brazed stainless steel core is supported by front and rear reinforced clamping plates. This structure improves mechanical stability and allows the exchanger to handle higher pressure duties compared with a light-duty brazed unit.
Main Structural Features
- 100% SS316 stainless steel wetted construction
- Copper-free brazed plate core
- Reinforced front and back plates for higher pressure resistance
- Compact plate channel structure with high heat transfer efficiency
- Suitable for approximately 30 kg/cm² pressure class design
- Smaller footprint compared with shell and plate heat exchangers
Comparison with Shell and Plate Heat Exchanger
Shell and plate heat exchangers are also suitable for gas cooling and industrial services, especially where very high pressure, large flow rate, or special mechanical requirements are involved. However, for this medium-sized biogas cooling duty, a full stainless steel brazed plate heat exchanger provides a more economical and compact solution.
| Item | Full Stainless Steel Brazed Plate Heat Exchanger | Shell and Plate Heat Exchanger |
|---|---|---|
| Cost | Lower for compact duties | Higher due to shell, welding, and heavier fabrication |
| Heat Transfer Efficiency | Higher, due to thin plates and turbulent channels | Good, but usually requires larger surface area |
| Footprint | Very compact | Larger and heavier |
| Material | 100% SS316, copper-free | Can be stainless steel, but cost increases significantly |
| Pressure Resistance | Enhanced by reinforced front and rear plates | Strong mechanical design, suitable for severe conditions |
| Best Fit | Compact gas cooling, water cooling, industrial process cooling | Large duty, very high pressure, special code requirements |
Performance Advantage in Biogas Cooling
The biogas enters the heat exchanger at 70.4°C and leaves at 25°C. Cooling water enters at 8°C and leaves at 18°C. This temperature program is suitable for a compact plate design because the plate channels provide strong turbulence, high surface utilization, and efficient heat transfer even with a small exchanger volume.
Compared with bulkier shell and plate equipment, the full stainless steel brazed plate solution reduces installation space, lowers equipment weight, and simplifies piping arrangement. For packaged biogas systems, skid-mounted equipment, and modular process units, this compact construction is a major advantage.
Typical Applications
- Biogas cooling before gas treatment
- Gas cooling before compression
- Wastewater treatment plant biogas systems
- Landfill gas cooling and conditioning
- Anaerobic digestion gas cooling
- Compact industrial gas-to-water cooling packages
Why HEXNOVAS Recommends This Solution
For this project, the full stainless steel brazed plate heat exchanger provides a practical balance between corrosion resistance, cost, size, and thermal efficiency. It is more economical than a shell and plate exchanger for this duty, while still offering a copper-free stainless steel construction suitable for demanding biogas cooling conditions.
The reinforced clamping plate design also gives the exchanger better pressure resistance, making it suitable for industrial systems where compact size and reliable pressure performance are both required.
FAQ
Why not use a standard copper brazed plate heat exchanger?
Biogas may contain moisture and corrosive contaminants. A copper-free full stainless steel brazed exchanger provides better material compatibility than a standard copper brazed unit.
Is this design the same as a shell and plate heat exchanger?
No. This is a compact stainless steel brazed plate structure with reinforced front and rear plates. It is smaller and generally more economical for this type of duty.
What is the advantage of reinforced plates?
The reinforced front and back plates improve mechanical support and pressure resistance, allowing the unit to handle higher pressure requirements than a light-duty brazed plate exchanger.
Can this exchanger be used for other gas cooling applications?
Yes. It can be considered for other gas-to-water cooling duties where stainless steel construction, compact size, and high thermal efficiency are required.
Need a Copper-Free Stainless Steel Heat Exchanger for Gas Cooling?
HEXNOVAS can provide compact full stainless steel brazed plate heat exchangers for biogas cooling, industrial gas cooling, process water cooling, and corrosion-sensitive thermal applications.
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