Demonstration of an Ultralow NOx Burner on a Firetube Boiler

This page updated March 1, 2006.

S.T. Johnson Co.

Demonstration of an Ultralow NOx Burner on a Firetube Boiler

CARB Grant Number ICAT 02-01

The statements and conclusions in this Report are those of the grantee and not necessarily those of the California Air Resources Board. The mention of commercial products, their source, or their use in connection with material reported herein is not to be construed as actual or implied endorsement of such products.

Project Objective
The objective of this joint project between S.T. Johnson Co. (STJ) and Altex Technologies Inc. (Altex) was to demonstrate the feasibility of applying laboratory proven combustion technology to commercially available gas burners for the purpose of reducing NOx emissions below the current BACT of 9 ppm at a lower cost per pound of NOx removed. Current technology requires massive amounts of FGR, operating very close to the limits of flamability, or large amounts of excess air, to reduce NOx emissions below the 9 ppm level currently enforced in many systems in California. Operation with NOx emissions below the 5 ppm level has heretofore required the use of post-combustion treatment.
Massive FGR, especially in conjunction with operation close to the limits of flamability, requires the use of active control systems to prevent unstable operation and has resulted in systems unable to follow load demand and in some installations has resulted in equipment failure and severe property damage. These systems have a cost as high as $3,676/ton of NOx removed. Post-combustion treatment (low temperature oxidation) results in a very high cost per ton of NOx removed, has higher energy costs, and requires the handling of a sodium nitrate waste stream. The cost of LTO systems can be as high as $24,500/ton of NOx removed. For the business climate to be viable for California industry a much lower cost to achieve even lower levels of emissions has to be developed.
Burner development in the past decade has reduced NOx emissions from around 90 ppm to less than 30 ppm without the use of FGR by developing different fuel / air mixing techniques to reduce thermal NOx. The addition of FGR or high levels of excess air has further reduced these levels to less than 9 ppm but at a high cost to industry. In order for a stable combustion system to produce NOx levels less than 9 ppm at a reasonable cost the formation of prompt NOx in the initial combustion process must be addressed. Unlike thermal NOx, prompt NOx is not greatly influenced by flame temperature. Combustion techniques originally developed and patented by Altex Technologies reduces the formation of prompt NOx and thermal NOx by combusting a portion of the fuel in a reducing environment in a fuel rich reactor for a specific residence time. This technique results in combustion products comprising partially oxidized fuel (CO and soot) as well as nitrogenous species including amine species (NH3) that act as NOx reductants within the final burnout zone. The remainder of the fuel is combusted in four highly oxidizing zones and then mixed in a controlled fashion with the partially oxidized fuel and reductants in a final burn-out zone. This technique results in a total NOx production of 15 - 18 ppm @ 3 percent O2 without the use of efficiency robbing excess air. The majority of these emissions is thermal NOx which can be further reduced to around 5 ppm with the use of a moderate degree of FGR.

Funding Source

Funding Amount




$  28,950

Penny Newman, Moehlman Boiler


Click here for the entire final report.

ICAT Funded Projects