Natural Gas Analysers

Significance of the Topic

The precise characterization of gaseous and liquefied natural gas composition is essential for custody transfer, quality control and energy valuation. Small variations in calorific value have substantial economic impact when volumes are large. Implementing reliable, standard-compliant gas chromatography (GC) systems ensures accurate quantification of permanent gases, hydrocarbons and sulfur compounds in a fast, repeatable manner.

Objectives and Study Overview

This application note describes a custom-configured two-channel GC analyser based on the Thermo TRACE 1300 platform. It is designed to comply with GPA 2261, 2177, 2186, 2286, ISO 6974 and ASTM D1945/D1946 methods for comprehensive natural gas analysis. The system targets simultaneous quantification of C1–C20 hydrocarbons, permanent gases (H2, O2, N2, CO, CO2), H2S and related sulfur components.

Methodology

The analyser employs two detection channels:

• TCD channel: separation of CO2, C2, H2S, H2, O2, N2, CH4 and CO on micro-packed columns housed in a heated valve oven.
• FID channel: hydrocarbon analysis from C1 up to C20 on a capillary column in a temperature-programmed GC oven, including baseline separation of neo-pentane.

Analysis times are 9 minutes for components up to C8 and 20 minutes for extended range up to C20. Sample introduction uses inert Sulfinert® tubing; optional valves allow liquid sampling, back-pressure regulation and stream selection.

Instrumentation

The system comprises:

• Thermo TRACE 1300 GC with two channels (TCD and FID)
• Robust process diaphragm valves in a dedicated valve oven for extended service life
• InstantConnect injector and detector modules for rapid maintenance
• Sulfinert® sample path for H2S analysis
• Optional liquid sample valve, additional carrier gas channel, stop-flow valve, back-pressure regulator and stream selector
• Data systems: Chromeleon, ChromCard, OpenLab, EZChrom Elite/ChromQuest
• Built-in calculation modules for superior/inferior calorific values, mean molecular weight, compression factor, density and Wobbe index

Key Results and Discussion

The analyser achieves minimum detectability better than 0.01% for most components and 0.05% for H2S. A dynamic range spanning four decades ensures accurate quantification across varying concentrations. Repeatability tests show <0.1% RSD for CH4, demonstrating high precision. Fast runtimes combined with robust hardware design deliver reliable performance for routine and high-throughput applications.

Benefits and Practical Applications

• Full compliance with major industry standards (GPA, ISO, ASTM)
• Rapid, high-precision analysis for custody transfer and QA/QC
• Flexible configuration for gaseous and liquefied samples
• Low maintenance with durable diaphragm valves and InstantConnect modules
• Comprehensive reporting including BTU, density and Wobbe index calculations

Future Trends and Potential Applications

Advances in column technology and micro-GC platforms promise even shorter run times and on-line monitoring. Integration with IoT and remote diagnostics will enhance real-time decision support. Coupling GC with mass spectrometry or novel detectors may extend capabilities to trace contaminants and isotopic analysis. Automation and data analytics will further streamline workflows in energy and environmental sectors.

Conclusion

The custom two-channel GC analyser based on Thermo TRACE 1300 offers a robust, standard-compliant solution for comprehensive natural gas analysis. Its high sensitivity, wide dynamic range and flexible configuration meet industry demands for accurate composition and calorific reporting.