Combined control of secondary air flaring angle of burner and air distribution for opposed-firing coal combustion

• We propose a novel combustion adjustment method with burner flaring angle.
• We combine burner flaring angle with air distribution to control combustion.
• The effect of combustion adjustment on temperature distribution is studied.
• The burnout and NOx emission are improved through combination adjustment.

A novel swirl burner with adjustable inner secondary air flaring angle β is proposed and tested in an opposed fired pilot-scale furnace. The influences of five different flaring angles (β = 11.4/17.1/26/31.7/35.5) are studied on combustion and emissions under different air distributions. Two different rank coals are used. Changing β with air distribution helps coal ignition and promotes burning temperature level. Low-rank coal requires larger β for ignition and burning fiercely than high-rank coal. Enlarging β to 31.7° helps to decrease CO emission effectively. The specific β corresponding to a certain air distribution can limit NOx emission further. The high burnout of two coals corresponds to different β of burner. Inner secondary air flaring angle variation, combining with air distribution adjustment, can improve coal adaption, and help burning more effectively and cleaning.