If you’re in the natural gas business, you know that a fundamental requirement for gas safety and contract sale of natural gas is to measure the amount of H2S and Total Sulfur. The level of these contaminants and sulfur-based odorants is strictly controlled to avoid equipment damage and risk to site personnel in transmission and distribution infrastructure. The Total Sulfur in Natural Gas standard application provides measurements down in the ppm range for Hydrogen Sulfide (H2S), Carbonyl Sulfide (COS), mercaptans, and sulfides (measured as RSH+). A Flame Photometric Detector (FPD) is used to give high specificity to sulfur species and enables high sensitivity ppm level measurements.
In order to achieve optimum repeatability and efficiency, it is essential to understand the need for a backflush measurement. Emerson’s Total Sulfur in Natural Gas standard application measures H2S and COS as discrete components and measures all other sulfur components as a single backflushed (RSH+) peak. The use of a backflush measurement is critical for Total Sulfur measurement as it allows all sulfur components to be grouped and measured, irrespective of their concentration. Without the use of a measured backflush peak, minor components can escape detection and a repeatable Total Sulfur value cannot be determined. This method also simplifies the analysis and reduces cycle time by not trying to resolve individual sulfur components.
To create this highly accurate and efficient sulfur measurement system, Emerson combines a C9+ Gas Chromatograph (the industry leading 700XA) and a flame photometric detector (Emerson’s FPD module). An FPD measures trace sulfur compounds. It uses the combustion of sulfur components in a hydrogen rich flame as a source for analytical detection. The system is an explosion-proof design that requires no instrument air supply for purging. This makes it an excellent choice for unmanned gas metering locations which are often very remote. The elimination of instrument air greatly reduces utility cost. The system’s MON2020 software enables remote maintenance and diagnostics, reducing time in the field.
The 700XA Total Sulfur measurement in natural gas can be done in 3 minutes. The measurement ranges are:
How do you currently measure sulfur in natural gas?