Gas, oil and dual-fuel burners
The burner decides the emissions, most of the efficiency, and nearly all of the reliability complaints.
| Turndown | 4:1 typical emissions guarantee; 8:1 – 10:1 available |
|---|---|
| NOx: low | ~30 ppm, typically with flue gas recirculation |
| NOx: mid | 20 ppm with higher FGR rates or newer burner heads |
| NOx: ultra low | Sub-9 ppm; sub-5 ppm achievable on some designs |
| Fuel | Natural gas, propane, #2 oil, dual-fuel |
| Ratio control | Mechanical linkage, or linkageless parallel positioning; fully metered on the largest plants |
| Trim | Oxygen trim closes the loop on air/fuel ratio |
| Gas pressure | Flowing pressure at the train inlet, not at the meter |
Emission figures are technology ranges, not permits. The limit that governs is set by your air district.
The short version
A new packaged boiler arrives with its burner already matched to the vessel and firing rate at the factory; a retrofit burner is selected and engineered onto an existing boiler, which is the more common conversation. Either way the burner is where fuel, air, and controls meet, and it is where most operating problems on a well-built boiler originate.
In California the emissions limit usually leads the selection rather than following it. The air districts set NOx limits that rule out whole classes of burner, so the compliant options are established first and the rest of the selection happens inside that set.
What decides the selection
- The NOx limit
- District rules govern, and the limit varies by district and by boiler size. This is the first question, not the last. It determines which burners can be permitted, and no amount of downstream tuning recovers a selection that cannot meet the limit.
- Firing rate and turndown
- Rate has to match the vessel, not the peak load on paper. Turndown decides whether the burner modulates through light load or short-cycles, and short-cycling drives both fuel waste and nuisance lockouts.
- Available gas pressure
- Measured at the train inlet, not at the meter. Insufficient gas pressure is one of the most common reasons a correctly specified burner will not make its rating on site, and it is discovered at startup far more often than at selection.
- Linkage or linkageless
- Mechanical linkage is simple and cheap to maintain; parallel positioning holds the fuel-air ratio far more precisely across the firing range and enables oxygen trim. The payback depends almost entirely on annual run hours.
- Fuel arrangement
- Single fuel, or dual-fuel with an oil backup for curtailment or reliability. Dual-fuel changes the train, the controls, and the permitting.
- Code and listings
- CSD-1 and the applicable NFPA requirements shape the safety train and the burner management system. The jurisdiction and the insurer both have a say, and it is cheaper to know which before quoting.
What to send us
Send what you have and we'll tell you what's missing. Knowing this up front is the difference between a quote this week and a quote after three rounds of questions.
We're finalizing manufacturer agreements now. Need something priced before then? We quote today.
- The boiler
- Make, model, and rating of the vessel the burner fires, from the nameplate. A photo of it is faster than transcribing.
- Firing rate
- Input in BTU/hr, or the boiler horsepower and efficiency it has to deliver.
- Fuel and pressure
- Fuel type, and gas pressure available at the train inlet.
- Emissions
- Air district and the NOx limit that applies to this unit.
- Controls
- Whether the existing burner management stays or is replaced, and the control voltage available.
- New or retrofit
- A conversion on an existing vessel is a different quote from a matched package.
The rest of the room
- Firetube Boilers The workhorse of the commercial boiler room: packaged, factory-assembled, and the default answer for most steam and hot water loads under a few hundred horsepower.
- Watertube Boilers Where the load is bigger, the pressure is higher, or the demand swings faster than a firetube can follow.
- Combustion Controls Two different jobs that get discussed as one: keeping the boiler safe, and keeping it efficient.
- Feedwater & Deaerators The equipment that decides how long the boiler lasts. Most premature vessel failure is a feedwater problem wearing a boiler-shaped disguise.
- Auxiliary Equipment The equipment around the boiler that decides whether the boiler behaves: blowdown handling, condensate return, surge capacity, and water treatment.
Have a spec, or just a nameplate?
Send what you have. We'll come back with selections, pricing, and lead times.
Get it priced