Studies of Thermal Behavior on Activated Carbons for the Selection of Regeneration Scheme

Abstract Activated carbon is the most potential candidate for the sorption of various gases including hydrogen and helium. Because of its large internal surface area greater than 1000 m 2 /gm, activated carbons in different forms are widely used in many industries like gas and liquid purification, fuel storage and chemisorption. Recent progress of vacuum and cryogenic technologies leads to the wide application of activated carbons in sorption cryopumps. Cryopump is defined as a kind of entrapment vacuum pump which captures the gas by surfaces cooled to temperatures below 120 K and hence after a certain operational time there is a need of regeneration. To define the regeneration scheme of the newly developed sorbents thermo-gravimetric analysis were carried out to study their thermal behavior. Based on the thermal behavior and the regeneration gas loads the required regeneration temperature needs to be fixed. Hence a system is established and experiments were carried out to know the thermal behavior of different forms of activated carbons. Before performing thermal degassing the sample chamber with activated carbon samples are also evacuated to a pressure less than 10 -3 mbar for the natural desorption to take place. Studies were carried out for knitted fabric, granular and spherical charcoal samples. It was observed that evacuation increases desorption by 1.5 to 2 times. From the thermal studies it was estimated that after heating till 100 0 C followed by continuous evacuation 80-95% of gases are removed from the sorbent. Therefore degassing or regeneration above 100 0 C will not be much effective for regeneration.