Comparison of Four Types of Vertical Radial‐Flow Adsorbers Based on Binary Adsorption of CO₂ and H₂O

Abstract

A mathematical model was established to investigate the binary adsorption process of CO 2 and H 2 O in vertical radial-flow adsorbers. The results showed that the variation law of the adsorption performance of the four types of adsorbers is similar to that of the flow uniformity. The flow uniformity can be used to indirectly reflect the adsorbent utilization and the adsorption performance of the adsorbers. The breakthrough regions and main adsorption regions of the different flow forms of the adsorbers are different. The centrifugal π-type adsorber has the best performance among the four types of adsorber. Compared with the centripetal Z-type adsorber, the pressure drop of the centrifugal π-type adsorber is reduced by 12.0 %, and the adsorption time of the centrifugal π-type adsorber is increased by 134 %.

Performance Evaluation of a Vertical Radial Flow Adsorber Based on Binary Adsorption of CO2 and H2O

“…1 and Tab. 1, respectively, which is a commonly used centripetal Z-type structure in the industry [3,17,18]. The flow regions in the VRFA consist of four parts: gas flows around the diversion zone into the annular channel, then vertically flows through the activated alumina layer and the molecular sieve layer, and finally flows out of the VRFA through the central channel.…”

“…There are many complex physical processes in the actual VRFA, such as impurity adsorption, flow and heat transfer in porous media. Therefore, based on existing research, in order to establish the mathematical model of binary adsorption of CO 2 and H 2 O, the adopted assumptions include [17,18]: (1) The working media is a ternary mixture gas composed of air, CO 2 , and H 2 O. (2) The binary adsorption of CO 2 and H 2 O is considered with the constant adsorption heat in the temperature range.…”

“…where C 2 represents the inertial resistance coefficient of the grating plates, j is the opening ratio. d represents the thickness of the grating plates, and C 3 is an empirical constant, taken as 0.98 [17,18]. Energy equation:…”

“…where C p,s and C p,f represent the specific heat of the solid phase and fluid phase, respectively, T is the temperature, l s and l f are the thermal conductivity of solid phase and fluid phase, respectively, S e represents the energy source term, and ΔH is the adsorption heat. The operating pressure in the VRFA is 10 325 Pa, and the operating flow Q is 2000 m 3 h -1 with 293 K inlet temperature and a gas volume composition of air comprising H 2 O:CO 2 = 99.76 %: 0.20 %:0.04 % [3,17,18]. The relevant calculation parameters of the porous media are given in Tab.…”

“…(4) The temperature change in the adsorption layers is small, so it is assumed that the solid phase and the gas phase of the adsorption layers are in thermal equilibrium. The linear driving force (LDF) model and the extended Dubinbin-Astakhov (D-A) model are used to describe the binary adsorption of CO 2 and H 2 O [3,17,18]. The mass transfer process is expressed by the LDF model [3,15]:…”