Experimental study on no heterogeneous reduction by char

Abstract

The NO heterogeneous reduction by char is one of the most prominent options to control NOx emissions from coal-fired power plants. Experiments on the char-NO heterogeneous reaction were carried out in an electrically heated fixed-bed reac-tor to investigate the effect of temperature, type of char, pretreatment method, additives and reaction atmosphere on the NO reduction capacity of char. The re-sults showed that temperature plays a crucial role in the NO reduction by differ-ent char. The kinetic analysis showed that char-NO heterogeneous reaction is controlled by chemical kinetic below Tt and by diffusion kinetic above Tt. The value of transition temperature Tt depends on the types of char and ranges from 600?C to 800?C. The synergistic effect of specific surface area, mineral abun-dance and reactivity combine to result in the reduction efficiencies of different char. Oxygen has a promoting effect on the char-NO heterogeneous reaction, and the oxygen content of the promoting peak moves to low oxygen content with in-creasing temperature. At 1050 ?C, the denitrification efficiency at 0.25% O2 con-tent is 12.7% higher than that under oxygen-free conditions. At high tempera-tures, the promotion of the char-NO heterogeneous reaction by CO and the inhi-bition of the reaction by CH4 were more obvious.