USEPA Method 11

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Hydrogen Sulfide Content of Fuel Gas Streams in Petroleum Refineries – USEPA Method 11

USEPA Method 11 involves the determination of the H₂S content of fuel gas streams at petroleum refineries. The method is executed by extracting a sample and passing it through a series of midget impingers containing a cadmium sulfate (CdSO₄) solution. H₂S is absorbed, forming cadmium sulfide (CdS), which is measured iodometrically.

Any compound that reduces iodine (I₂) or oxidizes the iodide ion interferes in this procedure if it is collected in the CdSO₄ impingers. Sulfur dioxide in concentrations of up to 2,600 mg/m3 is removed with an impinger containing a hydrogen peroxide (H₂O₂) solution. Thiols precipitate with H₂S. In the absence of H₂S, only traces of thiols are collected. When methane- and ethane-thiols at a total level of 300 mg/m3 are present in addition to H2S, the results vary from 2 percent low at an H₂S concentration of 400 mg/m3 to 14 percent high at an H₂S concentration of 100 mg/m3. Carbonyl sulfide at a concentration of 20 percent does not interfere. Certain carbonyl-containing compounds react with iodine and produce recurring end points. However, acetaldehyde and acetone at concentrations of 1 and 3 percent, respectively, do not interfere.

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Last Update: October 25, 2006