ASTM D6667 Total Volatile Sulfur in Gaseous Hydrocarbons/Liquefied Petroleum Gases
ASTM D6667 Standard Test Method for Determination of Total Volatile Sulfur in Gaseous Hydrocarbons and Liquefied Petroleum Gases by Ultraviolet Fluorescence
3. Summary of Test Method
3.1 A heated sample valve is used to inject gaseous samples. Liquefied petroleum gas (LPG) samples are injected by a sample valve connected to a heated expansion chamber. The gaseous sample then enters a high temperature combustion tube where sulfur is oxidized to sulfur dioxide (SO2) in an oxygen rich atmosphere. Water produced during the sample combustion is removed and the sample combustion gases are next exposed to ultraviolet (UV) light. The SO2 absorbs the energy from the UV light and is converted to an excited sulfur dioxide (SO2). Fluorescence emitted from the excited SO2 as it returns to a stable state SO2 is detected by a photomultiplier tube, the resulting signal is a measure of the sulfur contained in the sample. (Warning - Exposure to excessive quantities of ultraviolet light is injurious to health. The operator shall avoid exposing their person, especially their eyes, not only to direct UV light but also to secondary or scattered radiation that is present.)
4. Significance and Use
4.1 The sulfur content of LPG, used for fuel purposes, contributes to SOx emissions and can lead to corrosion in engine and exhaust systems. Some process catalysts used in petroleum and chemical refining can be poisoned by sulfur bearing materials in the feed stocks. This test method can be used to determine sulfur in process feeds, to measure sulfur in finished products, and can also be used for compliance determinations when acceptable to a regulatory authority.
