Hydrogen sulfide (H2S) and carbon dioxide (CO2) are often found in natural gas streams. These gases are removed using amine-rich solutions (e.g., monoethanolamine (MEA), diethanolamine (DEA), methanolamine, and methyldiethanolamine (MDEA)) before the natural gas can be transported/ used. However, amine solutions extract other contaminants during this process, which is also known as the amine-sweetening process. The contaminants in the acid gas removal processes are called heat stable salts (HSS). HSS are formed as a result of an irreversible reaction of the amine with certain acidic components present in process gases/liquids. Their strong chemical bonding with the amine molecule forms a salt that cannot be regenerated by the addition of heat. The increased HSS levels lead to several problems in an amine gas treating plant. The major problem is corrosion that leads to operation problems, resulting in unscheduled outages. Thus, it is important to monitor HSS in amine solutions so appropriate action can be taken to control them and avoid unscheduled outages. Ion chromatography (IC) has long been used to determine the presence of HSS in amine solutions. Here we demonstrate that a Thermo Scientific™ Dionex™ IonPac™ AS25A column can be used to analyze various refinery samples for the presence of common inorganic anions as well as heat stable amine salt anions (Figure 1). This column is a high-capacity, hydroxide-selective anion-exchange column ideally suited for determination of sulfur species in wastewater effluents from the chemical and petroleum industries. Using this column, a fast gradient method was developed and validated for the analysis of industrial amine scrubbing samples for 14 heat stable salts. Fourteen anions were separated within 30 min. The method showed good precision and accuracy with a recovery range of 83–105% for thiosulfate and thiocyanate in the samples tested.

Fast separation of heat stable salts

256th National Meeting (2018)

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