Landfill sites generate significant volumes of methane-rich gas as organic waste decomposes. Left unmanaged, this gas poses environmental, safety, and regulatory risks. The AC Range of open flare stacks offers a proven, well-engineered solution — providing a genuine degree of control over the combustion process in an elevated flame burner, something that traditional diffusion-style flares struggle to achieve.
What Is the AC Range Flare Stack?
The AC Range is an open flare stack system designed specifically for landfill gas destruction. Unlike simple diffusion burners, where air only mixes with combustion gases after they exit the burner port — producing a long, lazy, yellow-tipped flame — the AC Range uses pre-aerated combustion. Air is introduced before the gas exits the burner tip, producing a short, sharp, high-intensity, low-luminosity flame.
This difference matters. Reduced flame luminosity means reduced radiant heat, which in turn allows for a shorter flare stack without pushing up ground-level temperatures around the unit — a practical benefit for site layout and safety.
How It Works
The burner tip arrangement controls flame temperature within a band of 850°C to 1,000°C, with the exact figure depending on methane concentration, gas flow rate, and prevailing wind conditions. Because the unit sits in the open air on an elevated stack, there is inherently limited control over secondary combustion air — the ambient air that mixes with combustion gases after they leave the burner port. Wind speed and direction will always play a role in diluting and shaping the flame.
In favorable ambient conditions, a flame temperature of 1,000°C (1,800°F) can be held with reasonable stability. However, if methane percentage is low and wind speed is high, reaching this figure becomes very difficult — a limitation common to all elevated flare systems.
Despite these environmental variables, the AC Range consistently achieves strong destruction performance:
Destruction Efficiency Ratings (DERs) of greater than 98% can reliably be obtained, meeting basic minimum standards required in the USA.
Key Features
- High-intensity, low-luminosity flame for safer, more compact operation
- Booster turn-down to zero flow without surging
- Manual flame temperature control
- DERs greater than 98%
- Fully stainless steel construction available as an option
- Skid-mounted design for easy relocation around site
- Optional instrumentation for flow rate and gas concentration measurement
- Remote access and datalogging options
- Direct spark ignition, removing the need for a standing pilot flame
Operating Modes and Control
The system’s control panel is the operational heart of the unit. As standard, it offers the option to fit programmable timers, gas analysis alarms, and telemetry indications covering power failure, flame failure, and high oxygen conditions.
Ignition is automatic on start-up, and re-ignition after a flame failure event is automatic for an operator-settable period. Two particularly useful operating modes are built in:
- Dispersal and vent mode — used when gas levels are too low to sustain combustion, allowing the unit to continue safely venting gas.
- “Run on” mode — after a flame failure, the unit attempts re-ignition for a set period, then automatically switches to vent-only operation if re-ignition is unsuccessful. This keeps migration control active even when combustion isn’t occurring, which is especially valuable as methane levels naturally decline over a landfill’s lifecycle.
Technical Specification
| Parameter | Specification |
|---|---|
| Flow rate range | 100 to 15,000 m³/hour |
| Pressure rise across gas booster | 150 mbar |
| Flame temperature | 850°C to 1,000°C |
| Retention time | Not specified |
| Minimum methane concentration for sustained combustion | 20% |
| Number of inlets (standard) | 2 flanged inlets (additional available on request) |
| Flow control | Chemical duty butterfly valves |
| Pipework finish | Hot dip galvanised to industry standard |
| Burner material | High temperature stainless steel |
| Flame arrestor | Fitted on gas booster inlet and outlet |
| Flame detection | Self-checking UV sensor |
| Colour | Battleship Grey, or to customer specification |
| Destruction Efficiency Rating (DER) | Greater than 98% |
Build Quality and Site Practicalities
The pipework is fully galvanised as standard and designed to accommodate various types of flow meter, depending on budget and monitoring preference. Instrumentation includes pressure and temperature gauges at appropriate points in the flow stream, along with access points for hand-held anemometers and pitot static flow meters.
An inlet knock-out pot fitted with a filter de-mister element provides primary protection to the gas booster, ensuring pipeline debris cannot reach the impeller chamber — protecting the mechanical heart of the system from damage and downtime.
The entire unit is skid-mounted, simplifying transport and on-site repositioning, and it can be fitted with any of the standard options available across Organics Ltd.’s flare range.
Important Considerations
While the AC Range provides meaningfully greater control over combustion than a basic diffusion flare, it’s worth being clear-eyed about what elevated flares can and can’t do. As noted above, secondary combustion air cannot be tightly controlled in an open, elevated flame system — dilution will always vary with wind conditions. Consequently, the unit is not designed to meet the flame temperature control requirements demanded by certain more stringent emerging standards, which typically call for enclosed, insulated flare designs with extended high-temperature residence times. For landfill operators needing to meet those stricter standards, an enclosed flare system would be the more appropriate choice.
Key Takeaways
- The AC Range uses pre-aerated combustion to produce a shorter, less luminous, more controllable flame than standard diffusion flares.
- Flame temperature is manually controllable within an 850–1,000°C range, subject to methane concentration and wind conditions.
- Destruction Efficiency Ratings exceed 98%, satisfying baseline US regulatory requirements.
- Flexible operating modes (dispersal/vent and “run on”) help maintain gas migration control even during flame failure or low methane periods.
- The system is robust, skid-mounted, and available in stainless steel, with a wide range of optional instrumentation and remote monitoring.
- As an open, elevated flare, it is not suited to applications requiring the tightly controlled residence times mandated by stricter enclosed-flare emissions standards.
Get in Touch
If you’re evaluating flare options for landfill gas management and want to understand whether the AC Range fits your site’s methane profile, flow rates, and regulatory requirements, our team is happy to help. Contact us today to discuss your project and find the right combustion solution for your site.