Fired Heaters are one of the highest energy consumers in process plant, as it consume fuel to heat a process stream, reboil a distillation column bottom or generate steam. Design and operating efficiency of a fired heater is a key factor that determine the fuel consumption required to achieve the process requirements.
Regardless of the dilemma of calculating the efficiency based on the HHV or LHV of the fuel, two known methods to calculate the fired heaters efficiency are trusted:
1- Heat Loss Method (Preferred by Manufacturer or Mechanical
2-Direct Method (Preferred by Process Engineers)
In order to enhance the fired heater operating efficiency, main variables to be monitored:
1- Stack Temperature
2- Oxygen Analyzers
3- Draft Pressure
4- Flame Color
All these factors can be adjusted through controlling the air/fuel ratio, stack dampers opening, fuel inlet temperature and air preheating.