Emerson’s new gas chromatograph makes extended analysis easy for natural gas measurement

Emerson Process Management's new Danalyzer 700XA gas chromatograph includes specialized enhancements to help natural-gas distributors and others in the oil and gas industry accurately measure hydrocarbon dew point.  Monitoring hydrocarbon dew point enables natural gas pipeline operators to prevent condensation that can over-pressure the pipe, overwhelm liquid-handling facilities, and potentially lead to explosion hazards.  But numerous factors -- including gas composition, contaminants and additives, high pressures, and corrosive compounds -- make dew point one of the most difficult measurements to capture accurately. The 700XA gas chromatograph is designed to meet this challenge.
 
The 700XA simplifies the task by offering a fully automated hydrocarbon dew point monitoring process. A C9+ 700XA combines two detectors and a controller within a single housing – reducing complexity, minimizing maintenance and spare parts requirements, simplifying the scope of analyzers at the pipeline, and reducing the overall cost of the analytical solution.
 
The 700XA gas chromatograph features the highest stated precision available for C9+ applications – ±0.0125 percent of heating value (±0.125 BTU/1000 BTU) for controlled-environment C9+ analysis and ±0.025 percent of heating value (±0.25 BTU/1000 BTU) for uncontrolled-environment (-20 to 60 degrees C / -4 to 140 degrees F) C9+ analysis. 
 
DewCalc software incorporated in the 700XA's controller provides the exact calculations necessary for hydrocarbon dew point monitoring. No manual data entry is required. To provide more accurate inputs, the 700XA supplies actual C6/C7/C8 ratios to the calculation and adds a C9+ measurement. Because the dewpoint is a function of pressure, the application calculates the dew point at four user-defined pressures. These pressures can be set directly in the software or updated through the Modbus map.
 
The measured C6/C7/C8 and C9+ components allow for an accurate determination of the hydrocarbon dew point for pipeline-quality natural gas using reliable and low-maintenance thermal conductivity detectors (TCD), avoiding standalone dew point analyzers or flame ionization detectors (FID), which require additional utility gas requirements. For heavier gas applications where significant amounts of components above C10 are expected, a FID can be combined with a TCD to provide further extended analysis.
 

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