Method 15A

Determination of Total Reduced Sulfur emissions from sulfur recovery plants in petroleum refineries

This method is applicable for the determination of emissions of  Total Reduced Sulfur emissions (TRS) from sulfur recovery plants where the emissions are in a reducing atmosphere such as in Stretford units.  Samples are analyzed by barium-thorium titration as in EPA Method 6.

Sulfur reacts with metal and can bias results, therefore, all components of the sampling train need to be Teflon or Teflon lined.  Components of the sampling train include a probe, filter, and a series of four impingers.  The first two impingers contain a 3% hydrogen peroxide solution, the third impinger is empty and the fourth impinger contains silica gel.   During sample collection, combustion air is added to the oxygen deficient gas at a known rate.  This causes the sulfur to be thermally oxidized to SO2 which is collected in the hydrogen peroxide impingers as sulfate ion.  When sampling is completed, the hydrogen peroxide contents for each sample run are combined in a polyethylene bottle,  the impingers are rinsed with water which is combined with the impinger contents, and sent to the laboratory for analysis.

The oxidation process is non-discriminating and will oxidize other reduced sulfur compounds that are present in the gas.  These compounds will also be converted to SO2 and cause a positive bias in the results.  Calcium and aluminum found in particulates from these types of sources can interfere with the sample titration.  The Teflon filter in the sampling train is needed to remove the particulates.

(EPA 40CFR Part 60 Appendix A)


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Method Data

Hold Times, Preservatives, Preps, Collection, Analytical & Documentation
Holding Time:   None specified in method.
Preservatives:   None specified in method.
Required Preps:   Teflon filter
Collection Method:   Sampling train following EPA Method 15A procedures.
Analytical Methodology:   Barium-thorium titration following EPA Method 6.
Documentation:   15A

Analyte List*

Analyte Formula CAS Number Detection Limit
Carbonyl sulfide
Carbon disulfide
Hydrogen sulfide

* The analytes and detection limits listed for each method represent the typical detection limits and analytes reported for that particular method. Keep in mind that analyte lists may vary from laboratory to laboratory. Detection limits may also vary from lab to lab and are dependent upon the sample size, matrix, and any interferences that may be present in the sample.