Low cost coal-based carbons for combined SO 2 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 SO 2/NO removal from exhaust gas at the linear gas velocity used in commercial systems (0.12 m s −1). Char is produced from carbonization and optionally activated with steam. This char is used in a first step to abate the SO 2 concentration at the following conditions: 100 °C, space velocity of 3600 h −1, 6% O 2, 10% H 2O, 1000 ppmv SO 2, 1000 ppmv NO and N 2 as remainder. In a second step, when the SO 2 concentration in the flue gas is low, NO is reduced to N 2 and steam at the following experimental conditions: 150 °C, space velocity of 900 h −1, 6% O 2, 10% H 2O, 0–500 ppmv SO 2, 1000 ppmv NO, 1000 ppmv NH 3 and N 2 as remainder. It has been shown that the presence of NO has no effect on SO 2 abatement during the first step of combined SO 2/NO removal system and that low SO 2 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 SO 2/NO removal system.