A basic elevated landfill gas flare burns gas at around 850°C and suits remote sites that do not need to meet tight emission limits. The options that most often earn their place are pressure gauges across the filter and flame arrester, a condensate level switch, a slam-shut valve and a way to move condensate without a pump. This post walks through the choices using a quotation for two landfill sites in southern Europe.

The challenge: two sites, two sizes, one specification

A local agent asked for budget prices for flares at two landfills. One site needed a 1,000 m³/h unit and the other 250 m³/h. A pumping trial was also requested for the larger site. The base package was the same design at two sizes, which is a good way to compare options on equal terms.

The approach: a simple, serviceable base unit

What an AC Range elevated flare includes

• a skid-mounted package, assembled and tested in the factory;
• a galvanised condensate knockout pot with a polypropylene dewatering filter;
• a direct-drive gas booster with an explosion-protected motor (15 kW for 1,000 m³/h, delivering about 150 mbar) and a stainless steel impeller;
• a flame arrester, a manual trim valve and a pressure switch to detect loss of flow;
• a 5 m stack with a 321 stainless steel tip and shroud, with manual adjustment to hold 850°C;
• UV flame detection and PLC-controlled automatic ignition.

The flare offers moderate control of combustion through manual adjustment of the air:fuel ratio. That is enough where emission concentrations to European standards are not required, and it keeps the unit simple.

Why direct drive

The booster is direct-drive, so there are no belts to change. The supplier noted that a direct-drive unit it supplied in 1987 has run since without difficulty. Direct drive also makes an acoustic enclosure easier to fit. Unenclosed, the booster produces about 80 dB(A) at 1 metre. A belt-driven booster is offered for sites where flow varies widely.

Why options matter: a tour of the list

The options list is where a basic flare becomes a fit-for-site flare. The ones below solve real operating problems:

Monitoring

• Pressure gauges across the flame arrester and knockout pot. They show when an item is blocking. Most useful where silt or debris is expected.
• Vacuum gauges on the inlet lines. They give a continuous reading of suction from each part of the gas field.
• Temperature gauges on the booster inlet and outlet and on inlet lines.
• Anemometer or pitot tube insertion points. A low-cost way to measure flow in each inlet line.

Protection

• Level switch in the knockout pot. The unit will already shut down on low outlet pressure if the pot floods. A level switch gives earlier warning.
• Slam-shut valve on the feed to the flare. It stops gas burning back down the feed pipe when the booster stops and stops air being drawn into the extraction system when the unit is off.
• Flame arresters on sample points, where ignition through a sample point is a concern.
• Trace heating and lagging on condensate lines, where freezing is a risk.

Condensate handling

There are two routes. A pump moves condensate to a storage vessel. Alternatively, a buffer vessel with timed valves uses the pressure generated by the booster to push condensate to storage. No moving parts touch the condensate, and experience has shown that such systems can run for many years without breakdown.

Operation

• Automatic flame temperature control or a flame temperature readout for elevated flares.
• A programmable timer for automatic start and stop.
• Extra inlet pipes where more than one gas main connects to the flare.
• Enclosures: a walk-in weld mesh enclosure, a strengthened housing or an acoustic cover around the booster only.

What to consider for your own project

1. Start with your emission requirement. If the permit expects tight control, an elevated flare may not be the right base. See the Environment Agency’s landfill gas guidance for the UK position.
2. Add instruments where blockage or flooding is likely. Gauges and level switches are cheap compared with an unplanned shutdown.
3. Choose condensate handling for the site. A buffer vessel avoids pumps. A pump is simpler where storage is nearby.
4. Ask about noise early. If neighbours are close, price the acoustic enclosure with the flare.
5. Specify delivery and commissioning. The quote included delivery to port, one week on site for commissioning and a training course for site staff.

FAQ

What is an elevated landfill gas flare?

It is a vertical stack flare where the flame is visible at the top. Combustion air is pre-mixed and adjusted manually, and temperature is typically held around 850°C.

When is an elevated flare enough?

For remote sites, or where emission concentrations to European standards are not required. Otherwise a high-temperature ground flare is the usual choice.

What does a slam-shut valve do on a flare?

It closes the feed line when the booster stops, preventing flame burn-back and air being drawn into the gas extraction system.

Is a pumped or unpumped condensate system better?

A buffer vessel that uses booster pressure has no moving parts in contact with condensate. A pump is a simpler arrangement where a storage vessel sits close by.

Comparing flare options?

Send us your gas flow, location and permit requirements and we will help you choose the right base unit and options.