Changes of activated coke properties in cyclic adsorption treatment of flue gases

Changes of physico-chemical, sorptive and catalytic properties of two Polish activated cokes (industrial AKP-5 and laboratory SWS-6) used in flue gas cleaning with BF method were analyzed. The subsequent cycles of the process: SO2 sorption–thermal regeneration (S-R) resulted in the linear increase of the specific surface area of activated coke: from 218 to 482 m2/g for AKP and from 150 to 250 m2/g for SWS were presented. At the same time a gradual increase of a micropore volume at an unchanged volume of macropores was observed. An unfavorable drop of the ignition temperature, lowered mechanical strength and bulk density accompanied these changes. SO2 and Hg adsorptive activity is a linear function of the specific surface area. The initially dynamic sorption capacity 79 g SO2/kg of AKP increased by 67% in 15 S–R cycles. The dynamic adsorption capacity of Hg vapors increased from 0.25 to 0.9 mg Hg/kg of AKP. The degree of nitrogen oxide reduction using ammonia did not depend on the number of S–R cycles. The impact of ash content and the presence of some functional groups on the surface on denitrification degree were eliminated.

► Process of adsorptive – catalytic cleaning of flue gases was investigated. ► Successive cycles of SO2 sorption – thermal regeneration were analysed. ► Changes of sorptive and catalytic properties of two activated cokes were analysed. ► Adsorption capacity of SO2 and Hg increased with number of cycles. ► Degree of NOx reduction using ammonia did not depend on the number of cycles. ► Properties changes were correlated with the parameters characterising the coke surface.