Study on adsorption characteristics optimization of vertical radial flow adsorber

Abstract

In view of high energy consumption, poor flow uniformity, and short adsorption period in the actual work of vertical radial flow adsorber, computational fluid dynamics (CFD) technology and multiobjective genetic algorithm (MOGA) are used to optimize its structure. Through response surface analysis, it is found that the main structural parameters affecting adsorber performance are adsorption layer length and central channel diameter. The effect analysis of characteristic structural parameters and the calculation of multiobjective optimization show that the optimized structure has the ratio of horizontal to vertical of adsorption layer about 0.29 and the area ratio of central channel to annular channel about 0.67. Compared with the original structure, the optimized structure is reduced by 9.57% on pressure drop, increased by 0.86% on flow uniformity, and increased by 17.04% on breakthrough time. The data points on the response surface are used to fit the correlation of adsorber performance and the fitting degrees are 99.7% and 99.3%, respectively, which provided a theoretical reference for the optimal design of vertical radial flow adsorber.

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

“…Among them, the flow uniformity in the form of variance is widely used. Therefore, the definition provided by Fluent was chosen as the flow uniformity index [17]:…”

“…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.…”