Mathematical Modeling Of Adsorption And PSA Separation Of Acetone/air Mixtures

Presently, study on disposal and control of Volatile organic compounds in environment protection area is a tropic subject. Adsorption is commonly used for purifying VOCs for its advantage of simple equipment, easy operation and low energy consumption.The acetone a kind of VOCs is chosen as study object. Adsorption/desorption and pressure swing adsorption are adopted to separate acetone-air mixtures in this study. The experimental research is mainly focus on two parts: (1) effect of operation parameters such as inlet acetone concentration, adsorption/desorption temperature and desorption pressure on dynamic of concentration and temperature in column. (2) characteristics of temperature variations in adsorption column in PSA process. According to the experimental results, here we come to the conclusion that: (1) adsorption and desorption curves are affected by inlet acetone concentration, the lager the inlet acetone concentration is, the bigger the slope rate of concentration curves are. (2) The adsorption and desorption curves are just shift with time without shape varying at different adsorption/desorption temperature condition.(3) The equilibrium adsorption amount of adsorbent is relation with adsorption pressure. In vacuum desorption condition, the smaller the vacuum degree is, the larger craggedness of desorption curves are. At low pressure condition, the desorption curves appear lasting for capillary condensation. (4) Temperature curves takes on normal school in adsorption/desorption step at different location in adsorption column.(5) In pressure swing adsorption process, effective heat transfer coefficient has effects on temperature variations. In adsorption step, the smaller the effective heat transfer coefficient is, the larger of the ascend rate of the temperature is. In desorption, the bigger the effective heat transfer coefficient is, the larger of the descend rate of the temperature is.In this paper, according to the development of modeling on adsorption and by considering the main factors which play an important role in adsorption and PSA performance and the simplicity but without losing calculation accuracy of the numerical method, we brought up a series of models for the simulation of adsorption and PSA mathematical model. The axial dispersed plug flow model represented the flow pattern. The linear driving force (LDF) model was applied to accounting for the resistance to mass transfer between the fluid and porous adsorbents particles. We chose the D-R model to define the adsorption isotherm model. The heat effective is considered. The Clausius-lapeyron is adopted to calculate the adsorption heat, and the Cpa used in the model is followed by Krista S.Walton. The controlled partial differential equations are described into ordinary differential equations in space by finite difference method and the model is solved by chemical software named Athena visual workbench. Axial dispersion, heat effective and mass transfer resistance are taken into account in our models and they make the models more realistic. The discretization method is simple with adequate accuracy and the procedure with friendly interface.Our model and numerical method are applied to the adsorption and PSA process of the separation and recovery of acetone for for acetone-air mixtures. The dynamic of concentration and temperature in column at different operation conditions are simulated. The temperature variations in stable and non-stable state are also simulated. This indicated that our model and numerical method could be used to model the process of adsorption and PSA.Our calculation has showed that the models and numerical method in our paper are very efficient to study the adsorption and PSA process, such as concentration and temperature dynamic swing history, and effects of operating conditions on performance of PSA. The simulation will help experiment work, process design and optimization and modeling industrial process with multi-component adsorbate.