|
Vladimir Lifshits
Burner designs utilizing premix combustion principles are able to achieve
single digit NOx levels when firing natural gas with increased excess
air or higher rates of flue gas recirculation (FGR). The main challenge
for applying such burners to industrial boilers is the resultant limited
stability range with respect to the deviations in the equivalence ratio
and the rate of FGR. Satisfying narrow stability limits becomes especially
difficult, when the load modulates fast and over wide ranges. A new burner
developed by COEN company specifically addresses these challenges of ultra
low NOx combustion and operates reliably over a wider range of parameters
than other known burners. This QLA burner was developed over two years
of work on two research programs funded by The Gas Research Institute,
COEN, Southern California Gas, and California Air Resources Board. Most
of the development efforts were directed toward making the burner less
sensitive to the inaccuracy of the combustion controls, especially at
lower loads where correct ratios between the flows is more difficult to
achieve. The QLA burner has an optional variable geometry and multiple
fuel zones. While the major mechanism of NOx reduction is simulated premixed
type combustion, the burner also uses some degree of fuel staging. The
burner operates with low excess air and practically no CO emissions. It
can fire gas or oil and operate with air preheat up to 600°F. The performance
of the QLA burner in the field was demonstrated on a 60,000 pph field
erected brick set boiler equipped with two gas and oil fired burners fired
as one. The boiler operates in automatic with preheated air of 400°F and
10 to 1 turndown. The source test was passed with 7.3 ppm NOx and 3 ppm
CO (corr. to 3% O2, dry). Lower NOx - down to 5.5 ppm, was demonstrated
with reduced air preheat.
Download
in Adobe Acrobat PDF File (258 KB)
Back to top
|
