Modeling of multicomponent and multitemperature adsorption equilibria of water vapor and organic compounds on activated carbons

Abstract

Adsorption equilibria of the pure component and binary gaseous mixtures of water vapor and organic compound (toluene or n-butanol) on two selected activated carbons: Sorbonorit 4 and BPL 4Â6 were studied. A mathematical model of the adsorption equilibrium for binary systems with the virial mixture coefficients has been developed based on the two-dimensional virial equation of state. In the modeling, the experimental adsorption equilibrium data of pure components were correlated by the Toth isotherm for organic compounds, and Talu-Meunier or Qi-LeVan models for water vapor. Additionally, multitemperature isotherms for pure component were calculated to determine virial mixture coefficient of the two-dimensional virial equation of state depending on temperature. Adsorption isotherms determined for twocomponent systems were compared with multicomponent adsorption equilibrium data obtained experimentally by a dynamic method at relative humidities of the carrier gas set at 25, 50, 75, and 90%. A fairly good agreement between simulations and experimental results was obtained using expansion of the two-dimensional virial equation of state through D terms.

Modeling the Effect of Relative Humidity on Adsorption Dynamics of Volatile Organic Compound onto Activated Carbon

“…This is because water vapor can compete with VOCs for adsorption onto the carbon, reducing the adsorbent’s capacity for VOCs adsorption, particularly at high RH. − For this reason, some adsorption-based VOC capture systems utilize air preheating in order to reduce RH. The majority of experimental work from the literature observed similar effects. − ,− …”

“…4−6,12−20 Theoretical studies on the effect of water vapor on VOCs' adsorption are limited; therefore, mathematical models describing the competitive adsorption equilibria and dynamics between water vapor and VOCs are scarce. 5,6,8,12 In addition, the majority of adsorption dynamics models are one-dimensional and focus only on the axial variation of the adsorption process parameters. They fail to analyze important factors such adsorbed-phase concentration kg/m 3 eq C se,i equilibrium adsorbed-phase concentration ρ b (q v or q mv ); ρ b (q w or q wv ) kg/m C so,i adsorbed phase concentration of the ith component in equilibrium with its inlet gas phase concentration ρ b (q v or q mv ); ρ b (q w or q wv ) kg/m as radial dispersion and channeling effects in an adsorption column and therefore have limitations in comprehensively simulating a fixed bed adsorption process.…”

“…Activated carbon adsorption is a widely used method to capture volatile organic compound (VOC) emissions from industrial gas streams. − In such streams, water vapor tends to be ubiquitous, and may compete with VOCs during the separation/purification/recovery process. − Typical relative humidity (RH) values ranged from 0 to 95%. ,− For instance, in the automotive manufacturing process, painting operations take place in spraybooths, which include a spraying section to apply paint to the vehicle and a water scrubber system that captures paint overspray . However, contact between the VOC-laden air stream and the water scrubber system increases the humidity of the air stream.…”

“…Theoretical studies on the effect of water vapor on VOCs’ adsorption are limited; therefore, mathematical models describing the competitive adsorption equilibria and dynamics between water vapor and VOCs are scarce. ,,, In addition, the majority of adsorption dynamics models are one-dimensional and focus only on the axial variation of the adsorption process parameters. They fail to analyze important factors such as radial dispersion and channeling effects in an adsorption column and therefore have limitations in comprehensively simulating a fixed bed adsorption process. − In recent years, a few studies have carried out two-dimensional (2D, axial and radial) mathematical modeling to predict the transport processes (mass, momentum, and energy) in a fixed-bed adsorber, with good agreement between experimental and modeled results (overall mean relative absolute error = 6%). − However, these models did not consider the impact of water vapor on VOC adsorption.…”

Isobutanol Vapor Adsorption on Activated Carbons: Equilibrium and Kinetic Studies

“…They are used as solvents, chemical intermediates, extract agents, and recently as liquid fuels or fuel additives . Despite the growing demand of both alcohols, only few studies have focused on their adsorption behavior on various adsorbents to date. , In addition, most of them were dedicated to the n -butanol adsorption. , The main objective of this study was to compare the adsorption performance of three heterogeneous activated carbons for i-BuOH vapor removal from air. Three multitemperature isotherm models were found to best fit the experimental equilibrium data.…”