Reducing NO[sub x] emissions from magnesium sulfite liquor boilers

The Current design of liquor-combustion boilers is reviewed, along with options for lowering exhaust-gas emissions, particularly NOx. In many cases, modern boilers are being operated at or near optimal conditions for minimum NOx emissions. Possible upgrades to further reduce NOx emissions include addition of a selective noncatalytic reduction step, design modifications to lower the sectional load, a flue-gas recirculation system, and air staging. Calculated and experimental results show that these applications can lower NOx emissions by 40% or more.