Mathematical modeling and experiment of breakthrough curve for deactivated adsorbents packed in a multi-layer gas adsorber : case of high deactivation

Abstract

A multi-layer adsorber consisting of commercial activated alumina and two sizes of 4A molecular sieve is one system that is used to remove water from natural gas. The removal of vapour water from natural gas passing through the adsorber can be described by using the modeling of breakthrough time based on mass balance. To predict the breakthrough time, which changes along the time of service, the adsorbents were acceleratingly aged, especially the molecular sieve, which was studied only at the low degrees of deactivation in previous works. Therefore, in this work, the two sizes of molecular sieve were boiled at 600°C, and the number of batch cycles was varied to increase the aging. The SEM results showed that the average crystal size decreased when the number of batches increased. Also, the parameters in the mass balance equation and the water adsorption isotherms of adsorbents changing with the percentage of deactivation were determined to be used in the breakthrough time model in accordance with deactivation. It was found that the curve of the adsorption isotherm becomes more flat with higher degrees of deactivation, and Aranovich-Donohue for Toth was employed to explain the adsorption isotherm at various degrees of deactivation. Then, the breakthrough time from the experiments and theorem was compared which it was found that the modified mathematical model gave good agreement with the experiments. Additionally, the breakthrough time prediction for any degree of deactivation can be accomplished by using the predicted adsorption isotherm that was written as a function of degree of deactivation.