Mitigate H2S Spike in 4A Molecular Sieve Gas Dehydration

摘要

Dealing with wet sour natural gas is a global challenge faced in many plants worldwide and dehydration units are to be optimized to reduce the overall project cost. Normally 3A molecular sieve is preferred in sour gas dehydration applications as it does not adsorb H2S. The design illustrated in this paper depicts an innovative method for designing sour gas dehydration units using 4A molecular sieve that can mitigate H2S spike, reduce molecular sieve unit capital cost and operating cost of regeneration system by use of variable adsorption cycle. The variable adsorption cycle increases water loading in beds by maximizing adsorption time to desorb H2S molecules and thereby mitigate H2S spike during regeneration. This also prolongs mole sieve bed life by reducing the number of bed regeneration cycles as compared to fixed adsorption cycle. This design can be used in gas dehydration units downstream of acid gas removal units. This paper also proposes to avoid mixing of regeneration gas with main feed gas of mole sieve bed and instead propose to treat the regeneration gas at upstream acid gas removal unit to accommodate the H2S spike.