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 
radiant tube.

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.

0.0

5.0

10.0

15.0

20.0

25.0

30.0

35.0

40.0

45.0

50.0

0

250

500

750

1000

1250

1500

1750

Average Radiant Tube Temperature, °F

Typical NOx 

vs.

 Radiant Tube Temperature

NOx Corrected at 3% O

2

, ppm

Installation | Rasert™

Bulletin 4748

Page 4

FLAME SUPERVISION

½  

" 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.

LIGHTING ARRANGEMENTS

INSTALLATION CONSIDERATIONS

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 
distance. 

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.

.