Air Measurements, Monitoring and Controls (AM)

Modeling the Long-Term Performance of Activated Carbon in Cyclic Adsorption-Desorption of Volatile Organic Compound

983319 - Modeling the Long-Term Performance of Activated Carbon in Cyclic Adsorption-Desorption of Volatile Organic Compound (Student Poster 10)

Author(s)

AS

Amin Sadeghi Ardekani

M.Sc. Student
University of Alberta
Edmonton, Alberta, Canada

Activated carbon (AC) has attracted tremendous scientific and industrial interest in adsorption-based air treatment. Nonetheless, a major challenge associated with the use of ACs in adsorption-regeneration processes is the decline in adsorption capacity with time as a result of heel buildup (i.e. accumulation of non-desorbed species). Therefore, a model that can predict the effect of heel formation on AC's textural properties and, thus, capacity over time can be very useful for designing a reliable adsorption system and minimizing the AC loss.
The objective of the present work is to develop a model that can predict the long-term performance of AC during adsorption-desorption of a representative volatile organic compound (VOC). This research comprises two main components: 1) Modeling the impact of heel on AC’s pore size distribution (PSD), adsorption isotherm, and capacity, and 2) verifying the model using cyclic adsorption-desorption of 1,2,4-trimethylbenzene (TMB) (a common solvent in automotive painting operations) on beaded activated carbon (BAC). The model predicts the cyclic adsorption capacity of AC by applying the Dubinin-Radushkevich-Langmuir (D-R-L) isotherm based on AC’s limiting pore volume and adsorbate-adsorbent affinity coefficient.
The cyclic adsorption-desorption experiment results indicated that the cumulative heel build-up and the adsorption capacity followed ascending and descending trends with cycle number, respectively. The rate of heel formation per cycle decreased with time and almost plateaued at the 20th cycle. The model predicted a 18% drop in the adsorption capacity after 20 cycles, which is close to the experimental value of 24%. The accuracy of the model was further confirmed by comparing the PSD and VOC adsorption isotherm of used BAC provided by the model with those obtained experimentally. The proposed model can be useful for assessing the long-term performance of adsorbents.