A low-methane flare is built to burn gas that is too weak for a standard flare to hold a stable flame, using a low-calorific burner and automatic temperature control. In a quotation for a project developer in Canada, the package was a skid-mounted unit rated at 600 standard cubic feet per minute (roughly 1,000 m³/h), with a larger 2,000 SCFM unit offered as an option.

The challenge: gas that barely wants to burn

Gas from older landfills and from some digesters can contain so little methane that its heating value is low. A standard burner needs gas of a certain richness to keep a stable flame. As the methane falls, the flame can lift off the burner or go out, and unburned methane escapes. Methane is a potent greenhouse gas, so a flare that fails on weak gas defeats the reason for installing it.

The answer is a burner designed around low heating value, with the temperature controlled so the gas is fully burned.

The approach: the LM range flare

The proposal covers a flare in Organics’ LM range, supplied as a skid. The main elements are:

• Gas blower and motor rated at 600 SCFM, with a total pressure head of 60 inches water gauge (roughly 150 mbar), to push the gas through the system.
• Inlet knockout pot with a coalescing mesh filter that removes entrained water droplets.
• Low-calorific burner and stack for high-temperature combustion, with automatic temperature control.
• Safety fail-safe gas valve and flashback flame arresters.
• Pressure and temperature gauges for the operator.
• Stainless steel pipework and stack on a galvanised steel frame.

The skid is about 3.5 m long and 2.0 m wide, the stack is 9 m high and the whole unit weighs about 2,500 kg. It runs on a 480 V, three-phase, 60 Hz supply, which is the standard in North America. The flare is delivered by sea.

Plug and play, with an option for help

The flare is offered ready to run for suitably qualified staff, with an optional commissioning engineer to set it up and train operators. This suits a client that has its own engineers and wants to keep costs down, while giving the less experienced buyer a route to support.

Two sizes

The base proposal covered a single 600 SCFM unit. A revised quotation added an option for a flare rated at 2,000 SCFM, about three times the capacity. Offering two sizes lets a developer decide whether to cover only the current gas flow or to allow for a larger source.

Why it works

The three features that matter on weak gas are the burner, the temperature control and the water removal. A burner designed for low calorific value holds its flame in conditions that a standard burner would not. Automatic temperature control keeps the combustion temperature where it should be. A coalescing filter takes out water droplets that would otherwise absorb heat and may disturb the flame.

What to consider for your own project

1. Measure methane, not just flow. A flare rated by flow alone may not hold a flame at your methane concentration. Give the supplier your lowest expected methane and your oxygen content.
2. Check the electricity supply. Voltage and frequency differ by region. This unit was built for 480 V, 60 Hz.
3. Decide how much help you need. A plug-and-play unit saves cost, but a commissioning visit is worth it if your staff have not commissioned a flare before.
4. Allow for lead time. This unit is made in Thailand and shipped by sea, so allow roughly 20 weeks from order to arrival, including sea freight.
5. Check local permit requirements. For the UK, see the Environment Agency’s guidance on managing landfill gas and its enclosed flare monitoring guidance.

For flares designed around richer gas, see our post on enclosed flare design criteria.

FAQ

What is a low-methane flare?

It is a flare with a burner designed to hold a stable flame on gas with low heating value, usually because the methane content is low.

What does SCFM mean?

It stands for standard cubic feet per minute, a flow measure used in North America. 600 SCFM is roughly 1,000 m³/h.

Why does the flare have a knockout pot?

The pot and mesh filter remove water droplets from the gas before it reaches the blower and burner.

Can the flare be installed by the client?

The proposal assumes suitably qualified staff will set it up and run it, with an optional commissioning engineer.

Burning weak gas?

Tell us your methane range and flow and we will recommend a low-methane flare size.