Ultra Low NOx Gas-Fired Burner with Air Preheat Demonstration

This page updated November 28, 2005


Coen Company


Ultra Low NOx Gas-Fired Burner with Air Preheat


CARB Grant Number 95-354


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 Summary
Industrial steam generators face increasingly stringent NOx emissions limits. As industry continues to expand, steam demands increase, requiring installation of new boiler equipment. In the United States, all new and modified boilers must install either Best Available Control Technology (BACT) or Lowest Achievable Emission Rate (LAER) technology depending on the attainment status of the region in which they are located. In California, only the term BACT is used, and its meaning is equivalent to the federal definition of LAER. At present, LAER (or California BACT) for NOx ranges from 7 to 12 ppm for industrial boilers, though regulatory agencies are pushing to reduce this further to 5 ppm.
Until recently, the only way an industrial boiler could achieve single digit NOx emissions was through the use of selective catalytic reduction (SCR) in conjunction with a conventional low NOx burner. A 5 ppm alternative recently introduced is the Cannon Low Temperature Oxidation (LTO) process. The LTO process consists of an oxygen plant to generate ozone that is injected into the flue gas to oxidize the NO to water soluble NO2. The NO2 is subsequently removed in a scrubber. The LTO process can achieve 5 ppm, but it has not clearly been demonstrated in practice and both the capital and operating costs are very high. In the mid 1990's, a 9 ppm burner became available however, it has had a history of trouble with stability and control. The market and the regulators needed a safe and reliable ultra low NOx burner (ULNB) to provide a lower cost alternative to SCR and the Cannon LTO process.
Coen Company has developed and demonstrated a new ULNB for industrial gas fired steam generators. The new burner is called the Quantum Low NOx or QLA burner. Coen Company, the Gas Research Institute, and Southern California Gas Company funded the project. The California Air Resources Board ICAT program cofunded the demonstration phase. During the development phase, most of the emphasis was placed on widening the margin of stability such that the new burner would operate safely with conventional control systems at 9 ppm. Coen Company is also developing an advanced controls system that will enable safe operation of the burner down to 5 ppm.
In the demonstration phase, the QLA was installed on Boiler 1 at the State of California's Central Steam Plant in Sacramento, California. The plant provides steam for heating and cooling (through the use of steam driven chillers) to 23 state government buildings, including the Capitol. In compliance with the local RACT rule, the plant had previously installed low NOx burners. However, not only did the burners limit boiler load and reduce boiler efficiency, they were also only marginally compliant with the 30 ppm limit. Table 1 documents the improvements in both emissions and efficiency due to retrofit with the QLA burner. In addition, the steam flow turndown ratio is 10 to 1 and the burner is stable over a wide range of excess air levels and FGR flows. Figures 1 and 2 show the boiler with the QLAs installed. Figure 3 is the QLA flame at full fire.
The most important result of the retrofit is that the customer is happy with the performance of the burners over the past year, and wants QLA burners in the new boiler that he is planning to install. The QLA burner is now considered a commercial product, and Coen Company will guarantee NOx emissions of 9 ppm. Coen Company is currently developing an advanced burner control system, which will allow for a 5 ppm guarantee.
Table 1. Comparison of Pre- and Post-Retrofit Operation.
  Pre-Retrofit Post-Retrofit
Operating Conditions    
  Water Injection yes no
  Steam Injection yes no
  Air Preheat no 400F
  FGR % 10 40
  Maximum Load (pph steam) 52,000 61,000
Emissions (dry ppm, 3% O2)    
  NOx 30 7.5
  CO 15 2.9
Heat Loss Efficiency 71.6 78.4
Fan Power (hp) 91 216
Fuel & Power Cost ($/1000 lb stm) 3.89 3.55
Figure 1. New QLA burners installed at Central Plant Boiler #1.
Figure 2. Side view of Central Plant Boiler 1 showing new FD fan.


Funding Source Funding Amount

ICAT $195,304
Grantee $459,000
Gas Research Institute, Southern California Gas Company, and Southern California Edison $1,3338,000


Click here for the entire final report.


ICAT Funded Projects Page