No abstract

Removal of SO2 from flue gas by the absorbent prepared from coal fly ash, calcium oxide, and calcium sulfate was studied under different reaction conditions to elucidate the effects of the reaction temperature, water vapor pressure, and coexistence of NO in a flue gas. The SO2 removal activity increased with an increase in NO concentration up to 500 ppm at 130 °C. The SO2 removal activity increased as the water vapor pressure increased until a monolayer coverage with water molecule is achieved. As the adsorbed water exceeded the monolayer coverage, the SO2 removal activity suddenly decreased and calcium sulfite became the main product instead of calcium sulfate. The NO removal activity increased with an increase in SO2 concentration up to 2000 ppm at 130 °C. The NO removal also increased with an increase in water vapor pressure. The NO removal markedly decreased as the adsorbed water exceeded the monolayer coverage.

The absorbents for SO2 and NO from flue gas were prepared from calcium hydroxide, calcium sulfate, silicic acid, and aluminum hydroxide. The effects of the composition of the absorbent are studied on the activity for the absorption of SO2 and NO and on the structure of the absorbent. The activity for the absorption of SO2 and NO markedly increased with the content of silica in the absorbent up to 40%. The formation of calcium silicate is suggested to be predominant in a high concentration of silica, while the formation of ettringite was observed by the XRD only for the absorbent containing silica below 30%. The distribution of the sulfur and nitrogen compounds in the absorbent revealed by XPS suggests that adsorbed nitrogen compounds are gradually replaced by sulfur compounds as the reaction proceeds.

No abstract

No abstract