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.