Collection System and Flare
Typical LFG collection systems have three components:
- Collection wells and headers
- A condensate collection and treatment system for water and foreign materials
- A compressor
In addition, most landfills with energy recovery systems will have a flare for the combustion of gas not utilized in energy sales or production.
- Gas Collection System: Gas collection systems consist of a series of wells drilled into the trash in the landfill. Wells are traditionally perforated PVS pipe with well depth dependent upon the characteristics of the landfill. These wells are connected through a series of headers to a blower/compressor skid. The blower/compressor skid applies a vacuum to the collection system which draws the LFG into the wells and through the headers. The number of wells for a particular project is dependent upon the size of the landfill and the operating characteristics of landfill operations. Wells are installed as the landfill is filling. As the landfill continues to accept trash, existing wells are extended and new wells are installed in order to accommodate the additional LFG produced by the trash. The gas collection system must be expanded to comply with state and federal regulations pertaining to the landfill owner's requirement to control LFG. The gas collection system transports the LFG to the generating facility or to the pipeline for delivery to the industrial customer.
- Condensate Collection and Treatment: A condensate collection and treatment system is critical to the operation of the gas collection system. Condensate forms when warm gas from the landfill cools while it travels through the collection system. If condensate is not removed, it can clock the collection system and disrupt the energy recovery process. Condensate control typically begins in the field collection system where sloping pipes and headers are used to allow drainage into collecting ("knockout") tanks or traps.These systems are typically augmented by post-collection condensate removal as well. Some of the methods for disposal of condensate are discharge to the public sewer system, on-site treatment and recirculation to the landfill.
- Flare: A flare is included in the design of a gas collection and utilization system in order to properly handle LFG not utilized in the energy facility. This combustion of unused LFG is necessary for the landfill owner to maintain compliance with their state and federal LFG management obligations. Flare designs include open (or "candle") flares and enclosed flares. Enclosed flares are more expensive however may be preferable (or required) as they allow for stack testing and can achieve slightly higher combustion efficiencies. In addition, enclosed flares may reduce noise and light nuisances.