A comparison of linear driving force and pore diffusion models for a pressure swing adsorption bulk separation process

Simulation of temperature swing adsorption process to purify hydrogen for fuel cell uses by SAPO34 as adsorbent

To purify hydrogen gas from synthesis gas using a adsorption process, SAPO 34 adsorbent was used. Due to the strong adsorption of carbon dioxide in this adsorbent, it is not possible to recover the adsorbent by reducing the pressure alone, and it is necessary to use thermal operations for recovery. For this purpose, a temperature swing adsorption (TSA) process is used to increase the purity of hydrogen for use in fuel cells. To investigate the optimum operational conditions, various temperatures and different pressures of input gas were investigated to compare the purity and recovery of adsorption process. The TSA process was simulated for pressures of 11, 22 and 33 bars and the recovery percentage of each process was calculated. According to the results obtained, the recovery value at 33 bars is better than the other two pressures, but due to the fact that operational and initial costs increase at high pressures; 22 bar pressure was chosen to present the remaining results. In this work, the total amount of material and the molar rate are also reported. The average purity of the components in the product and waste outlet streams has also been presented. Accordingly, the average molar fraction of hydrogen in the product outlet stream is 99.96% in the temperature increase stage, 99.94% and in the stream used for temperature reduction is 99.96%.

Two-dimensional modeling of volatile organic compounds adsorption onto beaded activated carbon

A two-dimensional heterogeneous computational fluid dynamics model was developed and validated to study the mass, heat, and momentum transport in a fixed-bed cylindrical adsorber during the adsorption of volatile organic compounds (VOCs) from a gas stream onto a fixed bed of beaded activated carbon (BAC). Experimental validation tests revealed that the model predicted the breakthrough curves for the studied VOCs (acetone, benzene, toluene, and 1,2,4-trimethylbenzene) as well as the pressure drop and temperature during benzene adsorption with a mean relative absolute error of 2.6, 11.8, and 0.8%, respectively. Effects of varying adsorption process variables such as carrier gas temperature, superficial velocity, VOC loading, particle size, and channelling were investigated. The results obtained from this study are encouraging because they show that the model was able to accurately simulate the transport processes in an adsorber and can potentially be used for enhancing absorber design and operation.