LFG Collection System Utilizes QED’s Revolutionary LFG Measurement and Control Technology
At a landfill in British Columbia, Canada, construction of an LFG collection system has just been completed. The system, designed by Sperling Hansen, will be online in spring 2015 and includes QED’s Quick-Change™ Orifice Plate Wellheads** which combine easy plate exchanges for accurate flow measurements with precise adjustment control over a broad flow range.
“The main advantage, to me, is the Fine Tune™ Control Valve* that is used on the QED wellhead - it’s one of those revolutionary things in the landfill gas industry. Gate valves don’t give you very good control unless you always want the valve 100% open and you can apply as much vacuum as possible. But when it comes to low-flow wells then it’s important to be able to balance the field, and with a gate valve you really can’t do that,” said Ali Abedini of Sperling Hansen Associates Inc.
“The second advantage is being able to read more accurate landfill gas flow rates allowing you to more precisely balance the field. With QED’s orifice plate wellhead, you can quickly change the plate to have a proper pressure drop through the orifice and then get an accurate reading. I used to use wellheads with pitot tubes. Besides the tubes getting clogged and condensate freezing in them, the pitot readings fluctuated a lot.”
“With pitot tubes, especially at low-flow wells, the pressure drop (which will then be translated into flow rate) keeps fluctuating within a large range. The best you can do is to “fix” the reading when it’s around the average number using your judgment. For larger sites with several field technicians involved the readings are even more inconsistent. With the orifice plate wellheads, if you use a correct orifice plate and are in the optimum pressure drop range – 0.5 to 5.0 inches – you will have much less fluctuation, sometimes no fluctuation,” added Abedini.
QED’s New LFG Flex Hose is Easier to Install than Traditional Flex Hose
All types of landfill gas flex hose claims to have a long life on paper. But in conditions like British Columbia, temperatures can fluctuate from 40° C to -20°. Within a year or so, flex hose can get very fragile and lose elasticity. Abedini installed QED’s Solarguard™ Flex Hose† on some wells to compare it to other flex hose at the site. “So far, Solarguard looks great and it was less difficult to install on-site. You have to install flex hose at a certain angle, and if it’s too rigid you have a hard time, but the Solarguard is flexible enough to make that easier,” he said.
QED’s Well Cap Allows Measurements Without Disrupting Vacuum to the Field
QED has designed the first engineered gas well cap that does not have to be removed to take liquid level measurements; this reduces the release of gas and odors and means landfill workers are not exposed to those gases or leachate.
Abedini’s first impression of the QED Well Cap was good as far as look and feel, and he said that having access ports already there for any kind of monitoring is great, and the installation was easy. “The QED products all seem to be well thought out. It looks like whoever designs these products has been in the landfill gas industry for quite a while, knows about the operation of the system and its challenges, and has tried to resolve those challenges.”“If I adjust the applied vacuum on one wellhead I am affecting the wells around it. If I have to remove a wellhead to do a measurement I have to turn off the vacuum to that well, in doing so I have affected everything around that well. Then, I have to reassemble the well and readjust it, but I have to come back in a few hours or the next day to see if the wellfield is back to balance, because I have disrupted the vacuum distribution to the field. But when I don’t have to remove the wellhead, I don’t have worry about that,” Abedini said.
About Ali R. Abedini, Ph.D.
Ali is a Landfill Gas Specialist with Sperling Hansen Associates Inc. who are consultants specializing in providing solid waste management services including landfill design, operation, and closure plans; transfer station design and operation plans; landfill fire extinguishments and risk management, and training; landfill gas control and utilization systems design, and construction supervision. Abedini completed his Ph.D. at the University of British Columbia where he studied landfill gas generation and emission at the Vancouver landfill. He developed a new landfill gas generation model – iModel-110© – as well as methodologies to quantify GHG emissions from landfill surface. He has worked with the QED wellhead at the Vancouver landfill, as well as a few other sites where he conducted landfill gas pump test studies. In one of the gas pump test studies he utilized different types of wellheads and compared the results. Abedini was pleased with the results from the QED wellhead and that is why QED products are now being used in his designs.
* U.S. Patent Number 8,800,597
** U.S. Patent Number 8,800,597 & Patents Pending
† The Solarguard™ trademarks contained in this publication are trademarks of Kuriyama of America, Inc.
