Adsorption of hydrocarbon gas mixtures at high pressure

In this study, a water- and heavy hydrocarbon-removal process of a natural gas refinery currently in operation using the temperature swing adsorption method is modeled and investigated. The aim of this process is to decrease the hydrocarbon dew point to −10 °C and diminish the water content of the gas to about 0.1 ppm. This unit consists of four beds with two layers in which two beds are in the adsorption state, while the others are kept in the regeneration state. The gas composition and the bed specification are obtained from the available data from the refinery. The Ergun equation is considered for the pressure drop calculation. The results show that the developed model can predict the outputs with good accuracy. Sensitivity analysis of operating condition parameters such as temperature, pressure, and regeneration gas flowrate are carried out. Analysis of the regeneration temperature proved that temperature reduction from 268 °C to 210 °C can improve recovery of the heavy components. In addition, the regeneration gas flow rate can be reduced to about 0.4 kmole·s−1 as an optimum value. Moreover, 303 to 310 °C is the optimum range for the feed temperature. Due to the presence of the air cooler in the upstream process, and according to the ambient air temperature, feed temperature can be decreased to obtain better results.

show abstract

“…Equilibrium data of the hexane were derived from [23]. ∆H values for the components were from [24][25][26] (see Table 3):…”

Section: Adsorption Equilibriummentioning

confidence: 99%

Modeling and Investigation of an Industrial Dehydration and Hydrocarbon-Removal Process by Temperature Swing Adsorption

et al. 2022

View full text Add to dashboard Cite

show abstract

Adsorption of multicomponent mixtures by solid adsorbents

González

Holland

1970

AIChE Journal

View full text Add to dashboard Cite

A procedure based on kinetic principles is presented for the development of models for the adsorption of mixtures of gases in any number of layers by solid adsorbents. Equations of state for two-dimensional gas mixtures which are thermodynamically consistent with the adsorption models are also presented. The constants in the adsorption models for mixtures are obtained from the isotherms for the pure components. Good accuracy for the predicted adsorption of mixtures for the data available was obtained by use of a model for the in bimolecular layers.The increased use of solid adsorbents in separation processes has led to the need for methods for predicting the equilibria of multicomponent mixtures from a knowledge of the equilibrium adsorptions for pure components. Hill (9) followed by Arnold (1) proposed extensions of the BET equations ( 3 ) for the description of multicomponent adsorption. Mason and Cooke (17) used Hill's equations for two-layer adsorption to describe the equilibria of multicomponent mixtures. Lewis et al. (14,15) followed by others (6, 7, 11) extended the application of the Polanyi theory to include the correlation of the adsorption equilibria for multicomponent mixtures.Recently, Myers and Prausnitz (19) proposed a method that makes use of Gibbs' equation for pure component, the experimental isotherm for each pure component, and the expression for an ideal adsorbed solution in the presence of perfect gas vapors. Subsequently, Kinay and Myers (12) suggested a modification which improved the accuracy of the method of Myers and Prausnitz (19) at low pressures. To include the deviations of the adsorbed phase, Henson and Kabel (8) proposed a method based on the supposition of a hypothetical liquid phase in equilibrium with the adsorbed phase. And, more recently, Myers (18) presented a simplified method to handle ideal adsorbed solutions. DEVELOPMENT OF THE KINETIC MODELS FOR THE ADSORPTION OF MIXTURES OF GASES I N BIMOLECULAR LAYERSThe development of the models for the adsorption of mixtures of gases is a rather obvious extension of Langmuir's kinetic model for the adsorption of a pure component. The model for the adsorption of mixtures in unimolecular layers was first proposed by Markham and Benton ( 4 ) , and others, the following assumptions are made:1. The adsorbent is inert; that is, all of its thermodynamic properties are the same in the presence as in the absence of adsorbate molecules. As pointed out by Hill ( 9 ) , this approximation may well be inaccurate in the chemisorption of gases by solids.2. The surface area of the adsorbent is independent of temperature and pressure. This assumption is subject to the same inaccuracies as those encountered in the determination of surface areas ( 3 ) where relatively large gas molecules and porous adsorbents are involved.In addition, the kinetic model presented inherits some of the basic assumptions of Langmuir (13) :1. Molecules striking either the bare surface or the covered surface are candidates for adsorption.2. The probability of the evaporat...

show abstract