Total Sulfur Analysis in Liquefied Petroleum Gas in Accordance with ASTM D6667

Night view of an oil and gas refinery.

The EST NEXIS GM model, Gas & LPG Sample introduction module, is able to accurately sample and automatically introduce Gases and LPG samples into the EST NEXIS model Total Sulfur Analyzer. This feature results into a fully automatic calibration and sample analysis for trace level Total Sulfur content with the EST NEXIS series TS analyzers. Liquefied Petroleum Gas (LPG) is a group of hydrocarbon gases easily liquefied at moderate pressures which typically comprise C1 up to C10 hydrocarbons and S hetero compounds. The most common forms of LPG are methane (CH4),

Ethane (C2H6), propane (C3H8), propylene (C3H6), butanes (C4H12) and butylenes (C4H8). The most common S compounds found in LPG are sulfides, thiophenes and mercaptans.

LPG originates from two main sources: Associated gases in crude oils and gases produced in the refining processes. Because of its origin the composition of LPG varies in a wide range of components and concentrations. When processed industrial and domestic use as a fuel, hydrocarbons >C3 are removed since they are very valuable in petrochemical processes and gasoline blending operations. This type of fuel is a colorless and odorless mixture to which a certain amount of S compounds odorants is added to facilitate its detection. The determination of the total sulfur (TS) content in LPG streams is important to prevent sulfur related pipelines and equipment corrosion; to improve the quality of final products and to reduce pollutant emissions into the atmosphere.

LPG and other light hydrocarbons also find use as feedstocks for a variety of new refining catalytic technologies. The need for low sulfur measurements in this part of the industry is of growing importance since sulfur compounds poison the catalysts and negatively impact the economics of the processes. Furthermore, LPG is increasingly used as an automotive fuel and must therefore comply with stringent legislations concerning their Total Sulfur content.The Total Sulfur analysis of LPG by UV-Fluorescence detection is governed by ASTM D6667 and is applicable to samples containing sulfur in the range of 1.0 to 100 mg/kg. This application note describes a direct sampling and injection technique, which is fully compliant with ASTM D6667, for measuring low level sulfur in LPG using the EST NEXIS model Total Sulfur Analyzer in conjunction with the EST NEXIS GM model, Gas & LPG Sample introduction module.

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