Low cost coal-based carbons for combined SO2 and NO removal from exhaust gas

Abstract

The aim of this paper is to show how a cheap carbonaceous material such as low rank coal-based carbon (or char) can be used in the combined SO2/NO removal from exhaust gas at the linear gas velocity used in commercial systems (0.12 m s21). Char is produced from carbonization and optionally activated with steam. This char is used in a first step to abate the SO2 concentration at the following conditions: 100 8C, space velocity of 3600 h21, 6%O2, 10% H2O, 1000 ppmv SO2, 1000 ppmv NO and N2 as remainder. In a second step, when the SO2 concentration in the flue gas is low, NO is reduced to N2 and steam at the following experimental conditions: 150 8C, space velocity of 900 h21, 6% O2, 10% H2O, 0–500 ppmv SO2, 1000 ppmv NO, 1000 ppmv NH3 and N2 as remainder. It has been shown that the presence of NO has no effect on SO2 abatement during the first step of combined SO2/NO removal system and that low SO2 inlet concentration has a negligible effect on NO reduction in the second step. Moreover, this char can be thermally regenerated after use for various cycles without loss of activity. On the other hand, this regenerated char shows the highest NO removal activity (compared to parent chars, either carbonized or steam activated) which can be attributed to the activating effect of the sulfuric acid formed during the first step of the combined SO2/NO removal system.