Finned Tube Heat Exchangers for Landfill Gas Recovery

Finned tube heat exchangers play a crucial role in landfill gas (LFG) recovery, primarily serving to dehydrate and cool the gas during the pretreatment stage. They are essential equipment for ensuring the stable operation of subsequent purification, combustion, or power generation systems.

After collection from landfills, landfill gas typically enters at temperatures between 35-45°C and contains significant amounts of water vapor (saturated humidity). Direct introduction into downstream equipment can cause pipeline corrosion, equipment clogging, or efficiency degradation. The core function of finned tube heat exchangers is specifically designed to address these issues.

Cooling Treatment: Utilizing air or circulating water as the cooling medium, the finned tubes achieve efficient heat exchange, reducing LFG temperature to 20-25°C to prepare for subsequent dehydration.

Condensation Dehydration: During cooling, water vapor in LFG condenses into liquid water. Combined with separators, this process removes moisture from the gas stream, reducing LFG humidity to meet feed requirements for downstream equipment (e.g., methane purification units, gas generators) typically demanding a dew point ≤10°C.

Waste Heat Recovery (Optional): If LFG is subsequently used for combustion power generation, fin-tube heat exchangers can recover waste heat from combustion exhaust gases to preheat incoming LFG or heat circulating water, enabling secondary energy utilization.

Landfill gas exhibits complex composition (containing methane, carbon dioxide, hydrogen sulfide, ammonia, etc.) and is characterized by corrosiveness and dust content, imposing stringent design requirements on finned tube heat exchangers.

Material Corrosion Resistance:

The base tube should preferably be made of 316L stainless steel or duplex steel to withstand corrosion from gases like hydrogen sulfide and ammonia, preventing pipeline leaks.

Fins must be compatible with the base tube material. Common choices include aluminum fins (requiring anti-corrosion coatings like epoxy resin) or stainless steel fins to prevent corrosion and detachment.

Anti-clogging Design:

Wide-spaced fins (typically ≥8mm spacing) reduce dust and impurity accumulation between fins in LFG, minimizing clogging risks.

Structural Sealing:

Corrosion-resistant gaskets (e.g., fluororubber) must be used at flanges and interfaces to prevent corrosive gas leakage and ensure site safety.

Key Operational Maintenance Points: Ensuring Long-Term Stability

Regular Corrosion Inspection: Inspect the heat exchanger shell, fins, and piping for corrosion every 3-6 months. Promptly repair or replace components showing localized corrosion.

Cleaning Fins and Piping:

Based on clogging severity, blow out fins with compressed air every 1-2 months. Shut down equipment every six months to flush the tube side (cooling medium side) with a neutral cleaning agent to prevent scale buildup affecting heat transfer.

Monitoring Heat Transfer Efficiency:

Continuously monitor LFG inlet/outlet temperatures and cooling medium temperature differentials to assess efficiency decline. If temperature differentials significantly decrease, investigate for clogging or corrosion issues.