Two Dimensional Modelling of Volatile Organic Compounds Adsorption in a Fixed Bed Adsorber

Abstract

In this research two-dimensional mathematical models were developed to study adsorption of single component volatile organic compounds (VOCs) and competitive adsorption of n-component mixtures of VOCs from dilute gas streams in a fixed-bed adsorber. The models consist of the macroscopic mass, energy and momentum conservation equations and isotherm equations. Langmuir isotherm was used for single component VOC adsorption, while a new multicomponent isotherm model was derived to predict adsorption equilibria of VOCs mixture from single component isotherm data. The models were validated with experiments wherein deviation between measured and modeled data was quantified using the mean absolute relative error (MARE). The single component adsorption model predicted the breakthrough curves of the tested VOCs (acetone, benzene, toluene and 1, 2, 4-trimethylbenzene as well as the pressure drop and temperature during benzene adsorption with MRAE of 2.6, 11.8, and 0.8%, respectively. The model also showed very good sensitivity to the changes in operations variables such as temperature and superficial velocity of the carrier gas, channeling, and adsorbent particle size. The competitive adsorption model predicted the breakthrough profiles of binary and eight-component VOCs mixtures with 13 and 12%, MRAE respectively while that of the adsorbed amounts was 1 and 2%, respectively. These results indicate the accuracy of the models to simulate a fixed bed adsorber and their potential to be used for enhancing absorber design and optimization.