Case Study - D36 Single Tower Dryer at a landfill in Fairfax County, VA.
LAKE CITY, PA, USA -- Van Air Systems announces the successful application of a model D36 single tower dryer at a landfill in Fairfax County, Virginia. The dryer removes water vapor from landfill gas, allowing the fuel to be efficiently transported and combusted.
The I-66 Landfill in Fairfax County opened in 1962 and closed in 1982 with approximately eight million tons of Municipal Solid Waste in place. The decomposition of buried solid waste produces approximately 600 cubic feet per minute of landfill gas (LFG). The LFG is a mixture of mostly carbon dioxide and methane, which is a greenhouse gas.
In 2005 the Fairfax County Board of Supervisors funded a project for using a portion of the LFG, in lieu of natural gas, to heat an adjacent vehicle maintenance shop and truck wash facility. The scope of the project included installation of gas compression and clean-up equipment, gas transmission pipeline, and radiant heaters to burn LFG.
LFG emerges from the ground laden with water vapor and other impurities. The water vapor can condense as the gas cools, potentially clogging or freezing pipelines and reducing combustibility.
Wayne Blake-Hedges, a Senior Engineering Technician with Fairfax County’s Division of Solid Waste & Resource Recovery says that the project’s design engineer specified a refrigerant-type gas dryer for cleaning and drying the LFG. “The County wanted some redundancy, an insurance policy in case the refrigerated dryer malfunctioned.” During winter the vehicle maintence facility needs heat all the time, and the flow of LFG cannot be interrupted.
Wayne Blake-Hedges contacted Van Air Systems and its Richmond-based distributor, PBE Incorporated. After reviewing the design conditions at the I-66 Landfill, Van Air engineers recommended dryer model D36. The dryer consists of a single pressure vessel filled with 10BF tablets. 10BF is a specially formulated drying media for absorbing water vapor from any gas. The dryer has no moving parts and requires no outside power for operation.
Fairfax County purchased the D36 from Van Air and installed it as a back-up to a refrigerant dryer. In the fall of 2008 the County completed the project and began heating the vehicle maintenance shop with dry LFG.
“We had some operational issues with the refrigeration system,” says Blake-Hedges. Icing occurred in that dryer’s heat exchangers, causing problematic fluctuations of gas pressure. (Van Air Systems did not supply the refrigeration system.) In early winter 2009 the refrigeration compressor failed, and Van Air Systems’ D36 was put in to full-time service and it performed well, according to Fairfax County.
Blake-Hedges carefully monitored the performance of the D36, measuring and recording water vapor content upstream and downstream of the dryer. “The dryer has worked wonderfully,” he says. “The dew points [moisture content] were right where we needed them to be.”
“LFG to energy projects account for an important and growing share of our business,” say Mike Caldwell, National Sales Manager at Van Air Systems. “Our single tower drying process has long been established in compressed air and natural gas applications. We’re very glad to see the success Fairfax County is having with our technology.”
To view a list of operational LFG to energy projects around the U.S., follow this link to an EPA-compiled database.
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