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

Abstract

Activated coke (AC) acts both as an adsorbent for SO x and air toxic materials and as a catalyst for NO x reduction in flue gas treatment at temperatures of 100–200°C. AC has a surface area of 150–250 m 2g −1, which is less than that of conventional activated carbons, and an SO 2 adsorption capacity of 60–120 mg g −1 which is less influenced by the SO 2 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% NO x removal efficiency, which is much greater than that of the fresh material, for SCR-type NO x reduction with NH 3 at 140°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 NH 3 addition and may be attributed to an active N species on the AC surface that reacts with NO x . NH 3 treatment at 400–500°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.