Less excess air (LEA)

Reduces oxygen availability

Off stoichiometric Staged combustion a. Burners out of service (BOOS)

b. Overfire air (OFA)

Low NOy burner Internal staged combustion

Flue gas recirculation (FGR)

<30% Flue gas recirculated with air, decreasing temperature

Water/steam injection Reduces flame temperature

Reduced air preheat

Air not preheated, reduces flame temperature

Easy modification

Low cost; no capital cost for BOOS

Low operating cost; compatible with FGR

High NOX reduction potential for low nitrogen fuels

Moderate capital cost; NOy reduction similar to FGR

High NOy reduction potential

Low NOy reduction a. Higher air flow for CO reduction b. High capital cost

Moderately high capital cost

Moderately high capital and operating costs; affects heat transfer and system pressures

Efficiency penalty; fan power higher

High CO; flame length; flame stability

Flame length; fan capacity; header pressure

Flame length; fan capacity; turndown capability

Fan capacity; furnace pressure; burner pressure drop; turndown stability

Flame stability; efficiency penalty

All fuels

All fuels; multiple burners required for BOOS

All fuels

All fuels

All fuels

Significant efficiency Fan capacity; All fuels loss (1%/40°F) efficiency penalty


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