Before specifying a landfill gas flare, confirm the gas data, the power and flange interfaces, condensate drainage, access and the compound layout on site. A tender document rarely settles all of these. This checklist is based on a pre-tender site visit for a 1,000 m³/h enclosed flare at a council-owned landfill in Oceania, and shows which questions made a difference.

The challenge: a flare to replace a temporary unit

The council had a landfill with a ring main and vertical gas wells fitted with manual throttling valves. Gas was being flared by a temporary trailer-mounted unit at a neighbouring wastewater works. An existing generator used landfill gas, and the tender made clear that its gas use should take priority over flaring. No new generator was planned.

The supplier was asked to propose a permanent enclosed flare with its own blower. The visit was a chance to check what the documents did not say.

The checklist

1. Gas quantity and quality

• The tender gave methane at 45 to 70% by volume, saturated, at roughly ambient temperature, with flows up to 1,000 m³/h.
• No pumping trial or earlier gas assessment existed.
• A month or so of gas analyses was requested, and the client was asked whether the supplier should rely on those figures or verify them.
• Siloxane levels were not known. Analyses were requested because siloxanes can affect combustion equipment.

2. Condensate

• Existing knockout pots drained to a cut-off drain pumped to the wastewater works.
• One of the two candidate flare sites was about 170 m from that drain, so a new pipe or pump would be needed.
• The scope of the knockout pot and drainage had to be agreed in writing.

3. Power, data and flange interfaces

• The client was to supply power and data to the flare site, but the supply details were not yet available.
• The client might not have a standard flange pattern for the gas field pipe, so the connection details were to be confirmed.

4. Site access and working conditions

• The only route was a narrow, single-vehicle gravel track beside a stream, with long grass either side.
• Laydown and parking space were limited. The recommendation was that the client clear an area when doing earthworks for the base slab.
• Visitors needed basic PPE, a personal gas monitor and a group sign-in. Access was limited to set hours, with weekend work possible given notice.

5. Layout and flexibility

• The client had to build a slab on reasonably sloping ground.
• Two or three smaller skids rather than one large skid might reduce earthworks.
• The client indicated that better than 10:1 turndown, and the ability to burn gas below 45% methane, would be seen as advantages.

What the proposal offered in response

The design was an enclosed ground flare with a blower on the same skid:

• Flow: 100 to 1,000 Nm³/h, a 10:1 turndown.
• Temperature: at least 1,000°C above 25% methane, with a residence time of at least 0.5 seconds.
• Pressure: suction of about -100 mbar g, delivery to the flare at about 50 mbar g, and a blower head of roughly 160 mbar.
• Safety: double block-and-bleed valves, electro-hydraulically actuated so no compressed air is needed.
• Monitoring: a datalogger recording flare temperature, gas flow, total volume, composition, pilot status, pressure and ignition operation, with a modem for remote access.

The Environment Agency’s LFTGN03 and LFTGN05 guidance describe what regulators in the UK expect from flare design and monitoring.

What to consider for your own project

1. Visit with the operator. The visit worked best when the operator and the project facilitator were both there.
2. Write down every interface. Flange, power, data and drain connections should be confirmed in writing, and shared with everyone involved.
3. Photograph the site. Include access routes, candidate compounds and the existing equipment.
4. Decide who verifies the gas. Where gas data is thin, agree whether the supplier relies on it or checks it.
5. Ask about priority. If an engine uses the gas, the flare is a back-up and its size and control logic follow from that.

FAQ

Why visit the site before tendering?

Because access, drainage, power and ground levels affect both the design and the price and are rarely in the tender documents.

What gas data does a flare supplier need?

Flow range, methane and oxygen content, temperature, moisture and any known contaminants such as siloxanes.

Do I need a pumping trial?

It is the best way to measure gas yield. Here none had been done, so the client was asked to supply analysis data instead.

Who normally provides the base slab?

In this project the client provided the slab and the supplier supplied installation drawings for it.

Preparing a flare tender?

Talk to us about your site and we will help you build the data package for a flare specification.