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May/June 2009
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Sulfur Compounds

Sulfur compounds are known for their smell, but odor isn’t the only issue that these substances create, at least when found in various kinds of gas. Too much sulfur in gaseous fuels, such as natural gas, petroleum gases and biogases, can be corrosive to equipment, result in regulatory issues and can inhibit or destroy catalysts used in gas processing and utilization equipment.

However, sulfur gases used as odorants are essential for the safe distribution of natural gas because they inform users and the public in general of leaks in distribution systems and in appliances such as natural gas fueled water heaters. Accurate online measurement of sulfur compounds is essential to ensure gas quality, protect hardware and catalysts, and ensure safety.

A new ASTM standard covers an online sulfur measurement method that is widely used throughout Europe and the United States. ASTM D7493, Test Method for Online Measurement of Sulfur Compounds in Natural Gas and Gaseous Fuels by Gas Chromatograph and Electrochemical Detection, was developed by Subcommittee D03.12 on On-Line/At-Line Analysis of Gaseous Fuels, part of ASTM International Committee D03 on Gaseous Fuels.

“This online sulfur measurement method provides accurate measurement data as feedback information for effective sulfur removal and maintenance using various gas process schemes to achieve the desired fuel gas quality,” says Sherman Chao, Analytical Solution Inc., Willowbrook, Ill., and a D03 member.

Chao notes that small amounts of sulfur odor and compounds are added to natural gas and other fuel gases to facilitate gas leak detection and explosion prevention. D7493 provides a way of quickly monitoring the accurate addition of sulfur odorants to ensure appropriate odorant levels for public safety.

“Instrumentation using electrochemical sulfur gas measurement has wide usage in Europe,” says Raul Dominguez Jr., Ph.D., chair of Committee D03. “The technology is gaining greater usage in the United States, particularly in custody transfer transactions among natural gas providers and distributors. This increased usage in part prompted the initiation of D03.12 activity resulting in the preparation of D7493.”

According to Dominguez, the creation of this test method was also prompted by the need of natural gas distributors to provide local, regional or state public utility commissions with a standard test method for sulfur gas measurement as part of their regulatory compliance activity. D7493 is a companion to the laboratory-based ASTM D5504, Test Method for Determination of Sulfur Compounds in Natural Gas and Gaseous Fuels by Gas Chromatography and Chemiluminescence, that is in wide usage among stakeholders as the primary reference method in sulfur gas measurement operations. D7493 is also an alternative to D7165, Practice for Gas Chromatograph Based On-Line/At-Line Analysis for Sulfur Content of Gaseous Fuels, and D7166, Practice for Total Sulfur Analyzer Based On-Line/At-Line for Sulfur Content of Gaseous Fuels.

While D7493 has applications for other types of gases, including landfill, sewage digestor and refinery fuel gases, Dominguez notes that natural gas providers and distributors are, for the time being, the primary users of the new standard.

All interested parties who would like to participate in the activities of D03.12 are invited to participate in an upcoming interlaboratory study for D7493.

CONTACT

Technical Information: Raul Dominguez, South Coast Air Quality Management, Diamond Bar, Calif.

Phone: 909-396-2225

ASTM Staff: Brynn Murphy

Phone: 610-832-9640