NOx SUPPRESSION TECHNOLOGIES
The annular combustion in the North American RASERT™ burner
inherently results in lower combustion temperatures hence
lower NOx emissions. Additionally, other NOx suppression
techniques, including air staging and self recirculating FGR (fl ue
gas recirculation) are used. Air staging works by adding the
air to the fuel in controlled "stages" which delays combustion,
and reduces the concentration of oxygen in the hottest part of
the fl ame. It also helps maintain temperature uniformity on the
The 4748 design internally entrains FGR into the combustion air
streams. The addition of FGR lowers the peak fl ame tempera-
ture by reducing the concentration of oxygen in the combus-
tion air. The reduction of peak temperature greatly lowers the
amount of NOx generated in the fl ame.
The graph below shows typical NOx in the fl ue of a 4748-650
RASERT burner, operating with 140 cfh natural gas. The fl ue
gases exit the burner at approximately 1050°F and the burner
combustion air is preheated to approximately 1200°F.
Average Radiant Tube Temperature, °F
Radiant Tube Temperature
NOx Corrected at 3% O
Installation | Rasert™
" NPT male fi tting
which will fi t many UV fl ame detector cells without additional
adapters. See Bulletin 8832 for additional choices of fl ame
detectors and adapters, which must be ordered separately.
The RASERT burner has been tested as explosion resistant as
defi ned in NFPA86 2003 Section 3.3.16.
The radiant tube mounting fl ange should be located 26 inches
from the hot face of the furnace wall. This will ensure that the
stabilizer is "inside the furnace" and not in the furnace wall. If
the radiant tube is not long enough to meet this requirement, a
spool piece should be added to the radiant tube to make up the
The fi re tube inside the radiant tube must be engineered for
each application. Besides identifying the proper material, it
must be sized for the outlet of the burner, the length of the
furnace, and the inside diameter of the radiant tube.