Control of Solids Formation in Spent MEA and MMA Triazine H2S Scavengers

Abstract Triazine-based H2S scavengers are widely used in sweetening sour gas in bubble towers (scrubbers) and contactors due to the attractive combination of low cost, rapid reaction kinetics, and the high capacity for H2S removal. However, triazines are known to form troublesome solids known as dithiazines upon reaction with H2S. These deposits are exceptionally insoluble in typical solvent packages in scavengers and substantial quantities can deposit throughout the system. It has been reported that in the application of monoethanolamine (MEA) triazine scavengers, the severity of dithiazine precipitation and its nature could be improved by partial replacement of MEA with diglycolamine (DGA).1 In this study, MEA and monomethylamine (MMA) triazine scavenger solutions containing a variety of triazines based on the amines; dimethylaminopropylamine (DMAPA), monoisopropylamine (MIPA) and methoxypropylamine (MOPA), were examined to determine the efficacy towards mitigation of solids formation. Triazine solutions were substantially spent inside autoclaves and solids formation was monitored over time. The results of the performed tests indicated severe solids formation tendency for highly spent MEA and MMA triazine solutions. The test results confirmed that aging temperature could play a role in the severity of solids formation. Depending on the type of triazine, the addition of specific alternate amines significantly reduced solids formation tendency.