Restraining NO_x Formation during Coal Combustion in Packed Bed

The effects of various combustion conditions (i.e. particle size of coals, oxygen concentration in combustion gas and coal content in the fuel bed, etc.), on reducing conversion of NO_x during coal combustion were studied. Under the present combustion conditions, coals with smaller particle size gave the lower conversion of NO_x, and as expected that an decrease in overall stoichiometric ratio, whether by an decrease in O₂ content in combustion gas or by an increase in coal content in fuel bed would lead to a lower conversion of NO_x. In order to investigate the effect of metallic oxide layers on restraining NO_x formation, the combustion experiments for coal granules with adhering layer of various metallic oxides including Fe₂O₃, Ni₂O₃ and mixed oxides Fe-Ni-O_x were conducted in a packed bed combustor. The combustion experiments have shown that most of adhering materials gave considerable effect on reduction of NO_x emission during coal combustion.