(29b) Effect of Beaded Activated Carbon Fluidization on Adsorption of Volatile Organic Compounds
Adsorption on activated carbon is a widely used technique for controlling emissions of volatile organic compounds (VOCs); however, one challenge in removing VOCs from gas streams is irreversible adsorption or heel formation, which occurs during successive adsorption/desorption cycles. For adsorbents to be most effective, heel buildup should be minimized. This research investigates the effect of adsorbent bed configuration on VOC adsorption with beaded activated carbon (BAC). Five-cycle adsorption/desorption tests using a single VOC (1,2,4-trimethylbenzene) and a mixture of nine VOCs intended to simulate industrial painting emissions were completed using fixed and fluidized bed adsorber configurations. Adsorption tests were completed with full loading of the adsorbent. All regeneration cycles were completed in the fixed bed arrangement to standardize the regeneration method and focus results on the impact of bed-type during adsorption. Results show that the adsorption capacity of the BAC is not affected by the adsorption bedâ??s configuration in case of reaching full breakthrough. For the VOC mixture, however, 30% less heel buildup was observed for the fluidized bed configuration. Thermogravimetric analysis of the regenerated samples and gas chromatography â?? mass spectrometry during adsorption were also completed to assess the heel buildup and adsorption kinetics, respectively. Higher accumulation of heavy adsorbates was found in fixed bed as opposed to fluidized bed, justifying the higher heel buildup in the former. On the other hand, improved mass transfer was found across the entire fluidized bed as a result of better gas-particle contact. These results show that, besides the expected engineering advantages of a fluidized bed adsorption system (e.g., lower pressure drop), decreased heel buildup is an additional advantage when using fluidized bed adsorption in industrial settings.