Combined desulfurization, denitrification and reduction of air toxics using activated coke .1. Activity of activated coke

Activated coke (AC) acts both as an adsorbent for SO2 and air toxic materials and as a catalyst for NOx reduction in flue gas treatment at temperatures of 100-200 degrees C. AC has a surface area of 150-250 m(2)g(-1), which is less than that of conventional activated carbons, and an SO2 adsorption capacity of 60-120 mg g(-1) which is less influenced by the SO2 adsorption-desorption cycle than that of activated carbons. Two types of DeNOx reaction (SCR and non-SCR) can proceed over AC. Used AC shows 80-85% NOx removal efficiency, which is much greater than that of the fresh material, for SCR-type NOx reduction with NH3 at 140 degrees C and space velocity 400 h(-1). Acidic functionality in the used AC is believed to be an important factor in increasing SCR-type DeNOx activity. Non-SCR DeNOx proceeds without NH3 addition and may be attributed to an active N species on the AC surface that reacts with NOx. NH3 treatment at 400-500 degrees C is effective in activating AC for the non-SCR reaction. The N species on the AC surface also influences the DeSOx activity. Used AC has a higher adsorption capacity for Hg(0) vapour adsorption than fresh AC, demonstrating the effect of the surface functionality of AC. (C) 1997 Elsevier Science Ltd.