What is in this article?:
- Getting to Know Your Landfill Gas Collection and Control System
- Routine monitoring of BFS operations should include measurements of:
- SIDEBAR: GCCS Troubleshooting Guide
Understanding the basics of landfill gas collection system (GCCS) maintenance.
A typical landfill gas (LFG) collection and control system (GCCS) is extensive and includes several major mechanical components. Thus, with high energy costs, staying on top of operations and maintenance (O&M) is not only critical for continuity of service, it is crucial to make sure the system doesn’t incur costs, or worse, regulatory fines, associated with poor performance and unscheduled downtime.
Basic System Components and Checks
A GCCS is a common and major component of most sanitary landfills, designed to help:
- LFG migration control (to reduce potential for an explosion);
- LFG odor control;
- Control non-methanogenic organic compound release to the atmosphere;
- Provide LFG to an energy project; and
- Meet regulatory requirements.
Care should be taken to understand the basics of O&M, system troubleshooting and management of all the data it takes to keep a system functioning efficiently.
The GCCS includes two basic components:
Blower – flare station (BFS). The BFS is usually a skid-mounted equipment station that includes a condensate removal vessel and pumping system, one or more electric powered gas movers (either a centrifugal or positive displacement blower), LFG piping, a suction side shut-off valve, possibly a discharge throttling valve, a gas flow metering station, thermocouples and a flare.
The flare will include a flame arrester, a pilot gas supply and the main gas burner assembly. A control panel and an automated data recorder are also provided.
LFG collection wellfield. The LFG collection wellfield consists of two major integrated components: vertical wells and horizontal trenches for LFG collection; and main LFG header piping and branch piping connections to wells, trenches and leachate system cleanouts.
Good LFG well performance starts with proper design. This includes the proper number and spacing of collection wells and trenches, adequate size and depth of well boreholes, proper packing and sealing around the well screens and solid casings.
The wellhead should be completed with fittings that allow easy and direct access into the well casing, a flow adjustment valve and multiple points for gas measurements. Provide some extra flexible tube connecting the wellhead to the header to allow for differential settlement. There must be reasonable and safe access for personnel to each wellhead for routine monitoring and maintenance.
The main LFG header piping and branch connecting piping are responsible for distributing the vacuum produced by the BFS out to all collection devices. The piping also must carry some condensed LFG liquid to collection points. Thus, it must be designed conservatively and with an eye toward changes that occur over the life of the landfill that can potentially reduce its capacity.
The main header should form a closed loop, if possible, to more evenly disperse the vacuum and reduce overall vacuum loss. The pipe diameters should be judicious to allow for higher-than-predicted gas flow and/or vacuum, and possible future wellfield expansion. Pipe runs should include adequate slope to account for consolidation and uneven settlement of the waste over time and still allow for continual flow of condensed liquid. A design with undersized pipe and inadequate pipe slope can result in continual problems with lower-than-expected system performance.