Deep desulfurization of natural gas by a commercial ZnO adsorbent: A mathematical study for fixed-bed reactors

Abstract

Natural gas deep desulfurization process by zinc oxide adsorbent is an example of noncatalytic gas-solid reactions, which plays a crucial role in petrochemical and refinery industries. In this paper, it was tried to model the desulfurization process using grain model. In order to analyze the adsorbent properties, a commercial sample was tested by BET, XRF, SEM and, mercury porosimetry. The results of the numerical model were validated against the experimental data from a packed-bed reactor. The breakthrough time of the model was estimated with less than 5% error, indicating a good correspondence with experiments.The concentration profiles along the bed and inside the pellets have been also explored under the industrial conditions. The predicted breakthrough time for the commercial adsorbent has been estimated around 215 days. To identify the influential process parameters on the lifetime of the adsorbent bed, and degree of the bed conversion, the sensitivity analysis was performed in terms of natural gas flow rate and hydrogen sulfide concentration. Interestingly, the obtained results indicated that increasing the unit capacity by 10%, will decline the breakthrough time by 30 days. Furthermore, varying the H2S content of the inlet gas by 25% will shorten the breakthrough time of the commercial sorbent by 60 days.