Mass Transfer and Warming during Adsorption of High Concentrations of VOCs on an Activated Carbon Bed: Experimental and Theoretical Analysis

An experimental and theoretical study was carried out to predict the warming and the mass-transfer rate during adsorption of high concentrations of volatile organic compounds (VOCs) in an activated carbon bed. A linear driving force (LDF) model is found to provide an acceptable fit to the measured data. An empirical correlation of the mass transfer rate is proposed as a function of the strength of adsorbent−adsorbate interactions and the gas velocity to design the adsorption process without using any adjustable parameter. The model was validated for an adsorption unit with high loadings (up to 100 g.m-3) of seven kinds of VOC and within the velocity range 0.139−0.556 m.s-1. The prediction of the temperature rise inside the adsorber is improved by the use of the differential heat of adsorption instead of the integral heat. A theoretical parameter sensitivity test indicates that the temperature rise is strongly dependent on the molar VOC concentration, the adsorption heat, and the volumetric heat capacity of the carrier gas. The warming of the activated carbon bed can be well predicted from these variables. The relation obtained appears to be a practical means for designing the safety of an adsorber and preventing carbon bed ignition.