Influence of Purge Gas Flow and Heating Rates on Volatile Organic Compound Decomposition during Regeneration of an Activated Carbon Fiber Cloth

Five-cycle adsorption/regeneration experiments using 1,2,4-trimethylbenzene (TMB) were completed at different purge gas flow and heating rates to identify their impact on heel buildup. Regeneration of a saturated activated carbon fiber cloth was completed at 400 degrees C using resistive heating at different heating rates and purge gas flow. At 1 standard liter per minute (SLPM) desorption purge gas, increasing the regeneration heating rate from 5 to 100 degrees C/min increased heel buildup from 4.6 to 10.4 wt % and adsorption capacity loss from 7.8 to 52.0%. On the other hand, at 70 degrees C/min heating rate, increasing the purge gas flow rate from 0.1 to 5 SLPM decreased heel buildup from 14.6 to 1.4% and capacity loss from 82.3 to 2.1%. Increasing the heating rate or decreasing the purge gas flow results in higher TMB concentrations being exposed to the high desorption temperature and higher residence time of TMB in the adsorbent pores. This increases adsorbate decomposition, causing deposition of pore-blocking, high carbon content residue (coke) onto the adsorbent surface. These results show the importance of optimizing desorption conditions to minimize heel buildup during cyclic use, contrary to conventional wisdom, suggesting that higher heating rates are consistently preferred, and provide improvements in energy use.