There are many issues that reduce fired heater safety, reliability, or environmental performance. Many of these issues are often related to the firebox. Burner design, burner arrangement inside the firebox, firebox dimensions and shape, fuel composition, ambient effects all play a significant role in the success of a fired heater. When these factors do not come together properly, several issues can appear:  

  • Temperature excursions (‘hot spots’) on radiant coils, lower convection tube supports, or firebox refractory walls

  • Exceeding stack emissions limits on NOx or CO

  • Excessive flame length, fire clouds, or flame instability


The interaction between burners is the least understood by heater designers. Some knowledge resides with the burner vendor, but they usually enter the new heater design process when the burner arrangement and firebox shape have already been determined. At that time, substantial design changes are no longer possible. 

Adverse flue gas patterns and flame shapes can be caused by a multitude of reasons:

  • Uneven spacing between burners

  • Burners placed too close together

  • Imbalance in burner velocities

  • Uneven distances between radiant coils relative to burner heat release

  • Asymmetric firebox shape

  • Incorrect burner design

The XRG Team has the experience and skillset to approach these problems from a different approach.


We have a strong team that has used CFD in heater design and analysis for over 18 years.  They have devoted time and effort investigating the effects of heater design and burner spacing on flue gas recirculation patterns.

XRG Technologies will combine its expertise in combustion and CFD to determine the optimal burner layout and firebox shape for new fired heaters.  

This will ensure that:

  • Burners produce flames with optimal shape

  • Flame impingement on coils and flame clouds that result in safety and reliability risks are prevented

  • Firebox thermal efficiency is guaranteed 

  • Firebox temperatures are calculated accurately, ensuring that burner vendors can meet guarantees

  • Firebox dimensions are minimized by ensuring heaters are not overdesigned, saving on capital cost  

  • Heat distribution is improved, resulting in lower fouling rates, longer coil life and improved thermal efficiency (lower fuel consumption equaling savings to the owner)

  • Technology such as selective non-catalytic NOx reduction can be accurately applied inside the firebox (a technique that requires precise knowledge of temperature field and residence times inside the firebox)