An Experimental and Modeling Study of the Adsorption Equilibrium and Dynamics of Water Vapor on Activated Carbon

Abstract

In this work, the adsorption of water vapor on a commercial activated carbon is studied by means of static and dynamic measurements. To this end, two customized setups are used, which are able to deal with the challenges associated with adsorption measurements under humid conditions. In the first part, the equilibrium of water vapor on activated carbon during adsorption and desorption at 45 °C is characterized. The equilibrium adsorbed amount of water vapor exhibits a pronounced hysteresis loop, requiring the use of an isotherm model with hysteresis to describe the data. In the second part, fixed-bed experiments for both adsorption and desorption conditions at three feed velocities are presented. These dynamic experiments are described by a nonisothermal detailed column model, which considers the linear driving force model for mass transfer and axial dispersion. Heat and mass transfer coefficients are estimated so as to describe the fixed-bed experiments. The results from the static and dynamic measurements are shown to be consistent with each other for both adsorption and desorption conditions, provided the hysteretic behavior of the adsorption equilibrium is considered. Finally, it is shown that the use of an average value for the mass transfer coefficient results in good agreement between experiment and simulation, and the improvement due to a more complex model is minimal.

Separation of CO2 in a Solid Waste Management Incineration Facility Using Activated Carbon Derived from Pine Sawdust

“…Although the adsorption equilibrium and mechanisms of water vapor adsorption on activated carbon have been widely investigated [16][17][18][19], very few studies have used fixed-bed experiments to gain insight into the adsorption dynamics of water vapor on activated carbon [20][21][22].The impact of water vapor on the capacity of biomass-based activated carbons to capture CO 2 has been evaluated: adsorption equilibrium data, measured for CO 2 , N 2 , O 2 and H 2 O, and breakthrough experiments performed under different relative humidity were conducted to explore the mutual influence of CO 2 and H 2 O adsorption.…”

Measurement of water vapor adsorption isotherms in mesoporous materials using the zero length column technique

“…The fact that at higher flowrates the system is under kinetic control indicates that it is also possible to use the same instrument to measure kinetic properties, but the focus of this contribution is that of determining accurate equilibrium properties. It is important to note that the interpretation of kinetic experiments requires the knowledge of the derivative of the adsorption isotherm (Chmelik and Kärger, 2016;Glover et al, 2008;Hefti et al, 2015;Kärger et al, 2012;Lin et al, 1996;Ruthven, 1984) and clearly this can be estimated accurately from ZLC measurements given the large number of points available, particularly in the adsorption and desorption branches.…”

Molecular simulation and experiments of water adsorption in a high surface area activated carbon: Hysteresis, scanning curves and spatial organization of water clusters

“…Brunauer et al The models formulated by Rajniak et al [60] and Liu et al [54] have been used for the simulation of pressure swing adsorption processes in packed beds for water vapor removal [62][63][64][65]. Therefore, such models are probably considered the most appropriate analytical expressions for the correlation of type IV isotherms.…”

“…Due to the large adsorbed phase concentration change when adsorbing a condensable vapor, the mass transfer coefficient is strongly dependent on the amount adsorbed. In many experimental studies [63], the mass transfer coefficient has shown a clear minimum located in the hysteresis region of the equilibrium isotherm. This phenomenon has been theoretically predicted considering different approaches.…”

“…Šoóš et al[95,96] developed a lattice percolation model for the evaluation of the adsorption kinetics of nitrogen on Vycor glass and water on silica-gel. Hefti et al[63] used an empirical equivalent linear driving force model to predict the dynamics of water vapor adsorption in a column packed with activated carbons. However, more than ten empirical parameters were needed for a good prediction of the experimental breakthrough curves.…”