Bench and pilot scale assessment of 5A molecular sieves for tail gas treatment applications

Abstract

The modified Claus Process stands out as the predominant method for sulfur recovery within natural gas and crude oil processing facilities. Over the past five decades, in a bid to mitigate the environmental consequences of SO2 emissions, the efficiencies of sulfur recovery units have been enhanced through the integration of tail gas treating units (TGTU). Globally, it is imperative that this sulfur recovery efficiency attains a minimum of 99.95%. This paper delves into both bench- and pilot-scale evaluations of utilizing commercial 5 A molecular sieves to extract H2S from specific tail gas streams, as part of scrutinizing the efficacy of a novel tail gas treatment process, delineated in Patent No. US 10662061 B1 (May 26, 2020). The evaluation revealed that employing a 5 A molecular sieve to remove H2S from dry tail gas treating presents distinct advantages. Notably, the CO2 adsorption capacity on 5 A molecular sieves, being several times that of H2S, did not substantially impair the physical stability and removal capacity of 99.95+% tail gas treating, even after 99 adsorption/desorption cycles. Furthermore, the evaluation demonstrated that extended regeneration at 300°C (as opposed to 250°C) following the 50th and 90th cycles could effectively reinstate the original removal capacity of the 5 A molecular sieves. Additionally, the gas emanating from the 5 A molecular sieve bed could be reused as regeneration gas for the second stage of the patented process. The H2S removal capacity of 5 A molecular sieves from dry tail gas, approximately 1.3 mmol/g, aligns with the reported capacities of other adsorbents, which range from 0.37 to 1.53 mmol/g. Given the cost-effectiveness of 5 A molecular sieves compared to AgY molecular sieves, and based on the evaluation outcomes, it is judicious to conclude that the use of 5 A molecular sieves will be a compelling option for future tail gas treating within sulfur recovery units.