‘Good Value’ on Lots of Data

Monitoring flare gas at a landfill

When Walter Mahoney of The Louis Berger Group Inc. needed a cost-effective solution to monitor a landfill gas flare at a former solid waste disposal facility in Rhode Island, he found the perfect fit with the Mission model M-800. He needed real-time alerts to ensure that the gas flare was operating and methane gas was not migrating from the landfill. He also needed to monitor gas flow, stack temperature and the level of water in a condensate recovery tank.

According to Mahoney, "A pump is a pump, whether it is pumping liquid or air." Instead of monitoring lift station pumps, he needed to monitor a gas blower system used to extract and burn methane from the landfill gas collection system. "I like the pump status feature of the Mission system because it tells me when the blower is down and offers good value on lots of data," he said.

The monitoring system requires two analog inputs and one digital input. Mahoney uses a gas flowmeter with a 4-20 mA output to monitor the flow of methane from the collection system. He uses a second 4-20 mA input to monitor temperature at the flare stack where the methane is burned off. Knowledge of gas flow and stack temperature allows one to ensure the gas is being safely burnt off and is not migrating from the landfill site. Flow measurements and pump runtime data are also used to calculate the quantity of gas removed from the landfill.

Opting for Celluar SCADA Connectivity

As gas is compressed in the blower system, moisture is released into a knock-out pot where it subsequently flows to a below-grade storage tank. Two dry contact level sensors in the tank indicate "high" and "high-high" water levels. The switch contacts are connected to the M-800, allowing the Mission system to send instant alerts when the tank requires pumping.

A one-hour drive from Walter's office, the landfill is fairly remote. Walter opted for cellular SCADA connectivity because "a leased line was not a good option and would have resulted in high construction costs due to distance from the road." Walter added, "Mission is a great low-cost option that gives me the features I need."

It took Mahoney approximately four hours to install the M-800. He plans to install M-800s at another landfill gas flare site in the near future.