Volume 46 (2013) Issue 12 Pages 802-810
The purpose of this research is the development of a hybrid volatile organic compounds (VOCs) treatment process, which consists of adsorptive separation and catalytic oxidation. This process greatly reduces energy consumption compared with conventional thermal or catalytic combustion processes. Low concentrations of VOCs in polluted air are initially separated and concentrated into a small stream in the adsorptive step, and the concentrated VOCs are oxidized on an electrically heated alumite catalyst. Numerical system evaluation was carried out to estimate the effect of the concentration of VOCs in the air on the material and energy balances. Experimental and theoretical studies were performed on the adsorption of toluene in nitrogen gas, and desorption and concentration by hot nitrogen purging, in fixed-beds charged with activated carbon. A linear driving force mass-transfer model with an averaged overall mass-transfer coefficient was found to provide an acceptable fit to the measured desorption data. The experimental and modeling results were used to assess the influence of the purge gas flow rate and regeneration temperature on the bed length and cyclic steady-state convergence times using cyclic dynamic simulation of thermal swing adsorption. The evaluation results showed that a large amount of energy could be saved, and the unit cost lowered, by combining the adsorption step with electrically heated catalytic oxidation in the treatment of gases with low VOCs concentrations.