Application Analysis on the Bias and Air Staged Combustion Technology in the Opposed Firing Boiler

The bias combustion technology has been widely used in the swirling burner. Take the distribution of the pulverized-coal concentration at the primary air outlet as the division principle, there are three kinds of bias combustion models: radial model with inside dense and outside lean, radial model with outside dense and inside lean, and circumferential model. Considering stable ignition and low NOx emission, at the phase of the pulverized-coal ignition, the dense pulverized-coal flow should be heated by the high temperature flue gas intensively and quickly to ensure the coal’s timely ignition and form an In-flame NOx reduction zone for low NOx emission. Hence the bias combustion technology should be in accordance with the recirculation zone. So the radial bias model with inside dense and outside lean suits to central recirculation zone while radial bias model with outside dense and inside lean suits to annular recirculation zone. The circumferential bias model suits to both recirculation zones. Furthermore, appropriate measures should be taken on the burner’s arrangement and furnace’s design to prevent the obvious increase of slagging problem and unburned carbon in fly ash when using bias and air staged combustion technology.