Significance and Use

Gaseous fuels, such as natural gas, petroleum gases and bio-gases, contain varying amounts and types of sulfur compounds. These sulfur compounds are generally odorous, corrosive to equipment, and can inhibit or destroy catalysts employed in gas processing and end use, such as those used in fuel cell. Their accurate on-line measurement is essential to gas processing, operation and utilization, and of regulatory interest.

Small amounts (typically, total 4-6 PPMv) of sulfur odorants are added to natural gas and other fuel gases for safety purposes. Some sulfur odorants can be reactive, and may be oxidized, forming more stable sulfur compounds having lower odor thresholds. These gaseous fuels are analyzed for sulfur odorants to help in monitoring and to ensure appropriate odorant levels for public safety.

This method offers an on-line technique to continuously identify and quantify individual target sulfur species in gaseous fuel with automatic calibration and validation.

1. Scope

1.1 This test method is for on-line measurement of volatile sulfur-containing compounds in gaseous fuels by gas chromatography (GC) and electrochemical (EC) detection. The test method is applicable to hydrogen sulfide, C1-C4 mercaptans, sulfides and tetrahydrothiophene (THT).

1.1.1 Carbonyl sulfide (COS) is not covered in this test method.

1.1.2 The detection range for sulfur compounds is approximately from 0.1 to 100 PPMv or 0.1 to 100 mg/m ³ . The detection range may vary depending on the sample injection volume, chromatographic peak separation and the sensitivity of specific EC detector.

1.2 This test method describes a GC-EC method employing packed GC columns and a specific detector as an illustration for natural gas and other gaseous fuel containing mainly light hydrocarbons. Alternative GC columns, detector designs and instrument parameters may be used for the same analysis or for different types of gaseous fuel, provided that appropriate chromatographic separation and optimal detection of these compounds can be achieved.

1.3 This test method does not intend to identify and measure all individual sulfur species, and is mainly employed for monitoring natural sulfur and sulfur odorant compounds commonly found in fuel gases or employed as an odorous warning agent in fuel gases.

1.4 The test method is normally employed for repetitive on-line monitoring of sulfur components in fuel gases with a single sulfur standard. The test method may be employed for laboratory-quality measurement with more extensive calibration. (See Test Methods D 5504 , D 5623 , D 6228 , D 6968 , ISO 19739, ISO 6326-2, and GPA 2199.)

1.5 The test method can be used for measurement of all listed sulfur compounds in air or other gases, provided that no compound, which can interfere with the GC separation and electrochemical detection, is present.

1.6 This test method is written in conjunction with Practices D 5287 , D 7165 and D 7166.

1.7 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.

1.8 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

2. Referenced Documents (purchase separately) The documents listed below are referenced within the subject standard but are not provided as part of the standard.

ASTM Standards

D3609 Practice for Calibration Techniques Using Permeation Tubes

D4150 Terminology Relating to Gaseous Fuels

D4626 Practice for Calculation of Gas Chromatographic Response Factors

D5287 Practice for Automatic Sampling of Gaseous Fuels

D5504 Test Method for Determination of Sulfur Compounds in Natural Gas and Gaseous Fuels by Gas Chromatography and Chemiluminescence

D5623 Test Method for Sulfur Compounds in Light Petroleum Liquids by Gas Chromatography and Sulfur Selective Detection

D6228 Test Method for Determination of Sulfur Compounds in Natural Gas and Gaseous Fuels by Gas Chromatography and Flame Photometric Detection

D6968 Test Method for Simultaneous Measurement of Sulfur Compounds and Minor Hydrocarbons in Natural Gas and Gaseous Fuels by Gas Chromatography and Atomic Emission Detection

D7165 Practice for Gas Chromatograph Based On-line/At-line Analysis for Sulfur Content of Gaseous Fuels

D7166 Practice for Total Sulfur Analyzer Based On-line/At-line for Sulfur Content of Gaseous Fuels

ISO Standards

GPA Standard

Keywords

electrochemical detection; gas chromatography; odorants; on-line measurement; sulfur compounds;

ICS Code

ICS Number Code 75.160.30 (Gaseous fuels)

DOI: 10.1520/D7493-08

ASTM International is a member of CrossRef.

ASTM D7493