An elevated landfill gas flare can be programmed to light only when the gas is combustible, retry at set intervals, and vent harmlessly in between. This post describes that logic using a 10 to 50 m³/min elevated flare package quoted to an engineering contractor in the Middle East, with two booster sets and a 5 m stack.
The challenge: gas quality changes
Landfill gas methane content rises and falls. A flare that insists on lighting whatever the gas quality either burns fuel for nothing, or tries to ignite a mixture that will not burn. The question is how to make the flare patient.
The approach: ignite on the landfill gas itself
The elevated flare is lit using landfill gas as the ignition gas. The supplier regards this as more reliable than bottled fuel, because the flare operates only when combustible gas is available. The flare is programmed to attempt ignition for a set time, for example 45 seconds. If the gas is not combustible it shuts down and tries again after another period, for example 45 minutes.
Three operating modes
- Burn: the normal mode.
- Vent only: the gas is released without burning.
- Continuous run: the flare vents when gas is not combustible (for example methane below about 21%) and automatically attempts ignition at pre-programmed intervals.
The supplier noted over 150 elevated flares of this type installed around the world.
The package
- Two blower assemblies with ExN motors, each 25 m³/min, with stainless steel impellers, direct drive and star-delta starters.
- A condensate knockout pot with a polypropylene dewatering filter and a liquid seal holding about 180 mbar.
- A 321 stainless steel flare tip and shroud, 5 m high, with manual flame temperature adjustment up to 850°C.
- A UV flame sensor, PLC-run ignition, an outlet pressure switch and a flame arrester on the blower outlet.
- A galvanised pipework, skid-mounted with Battleship Grey finish, and an IP55 control panel.
The units suit remote locations or sites where emission concentrations to European standards are not a requirement. The package was function-tested before delivery, with on-site commissioning not included and available on request.
Why it works
Making ignition depend on the gas avoids wasted fuel and wasted attempts. Retrying on a timer means the flare recovers without an operator, and the vent mode keeps the gas moving safely when it cannot burn. The trade-off is accepting a lower, manually set flame temperature, so it is the wrong choice where a regulator needs a measured high temperature.
What to consider for your own project
- Choose retry intervals to suit how fast gas quality recovers at your site.
- Check where emissions rules apply. See ground flare or elevated flare.
- Define the vent route for unburnt gas.
- Allow for two boosters if you want redundancy.
FAQ
Does the flare need LPG?
No. It ignites on landfill gas.
What if methane drops?
In continuous run mode the flare vents and retries at preset intervals.
Remote site flare?
Tell us your site and gas quality. Related: an elevated flare specification example.