Development of a Low NOx Burner for Use with Preheated Combustion Air

In industrial high temperature heating operations the conversion of energy into process heat is associated with high stack losses. The recovery of heat from the flue gases for preheating of combustion air substantially reduces the consumption of fuel and thus also the emissions of CO2. Energy savings in the range 25% to 500/0 can result from preheating the combustion air between 1200 F and 2400 F. However, as the temperature to which the combustion air is preheated rises, the flame temperature increases and results in substantial increase in emissions of NO x implicated in the smog and acid rain problems. The increase raises the NOx output from conventional burners to levels exceeding the threshold limit values laid down is pollutant emission regulations. As the threshold limit values for NOx emissions become more stringent, to maintain efficiency of production this problem is addressed either by post-combustion treatment of the flue gases, external flue gas recirculation to reduce NOx formation, oxy-fuel combustion, or a combination of these measures. All of the above carry cost penalties per unit of fuel consumed and therefore per unit of product produced.