Parallel GC for Complete Refinery Gas Analysis

Importance of the Topic

Fast and accurate determination of refinery gas composition is crucial for refining operations optimization, product quality control and environmental compliance. Refinery gas comprises permanent gases, light hydrocarbons and trace sulfur compounds, requiring rapid, reliable and comprehensive analytical methods.

Objectives and Study Overview

This study demonstrates a six-minute, high-resolution analysis of complete refinery gas using an Agilent 7890A gas chromatograph configured with three parallel channels operating simultaneously. The approach enables simultaneous quantification of permanent gases (H2, He, N2, O2, CO, CO2), C1–C5 hydrocarbons and a grouped C6+ fraction. Instrumental flexibility for extended analyses of H2S and COS is also explored.

Methodology and Instrumentation

The system comprises one Agilent 7890A GC equipped with one flame ionization detector (FID) and two thermal conductivity detectors (TCDs). The FID channel separates light hydrocarbons (C1–C5 and group backflush of C6+) using a DB-1 column and an HP-PLOT Al2O3 S column. One TCD with helium carrier analyzes permanent gases except H2, while a second TCD with nitrogen or argon carrier enhances H2 sensitivity and linearity. Valves (10-port for sampling/backflush, 6-port for sequence reversal) and a capillary-flow union connector optimize peak shapes. A macro automates gas properties calculations and compositional reporting in accordance with ASTM/GPA or ISO standards.

Main Results and Discussion

Complete separation of permanent gases and C1–C5 hydrocarbons is achieved within six minutes with RSD values below 0.1% for retention times and below 1% for peak areas. Adjustable backflush timing allows grouping of C6+ or C7+ and full individual hydrocarbon speciation up to C9 with extended run times. Hydrogen analysis benefits from the second TCD carrier option, and high-concentration H2S/COS detection is feasible with extended backflush delays. Natural gas samples show similarly robust performance under identical conditions.

Benefits and Practical Applications

The parallel GC configuration significantly reduces analysis time while maintaining high sensitivity and reproducibility. Flexibility in backflush schemes enables tailored hydrocarbon profiling without hardware changes. Integrated data reporting streamlines compliance with industry standards and provides comprehensive compositional and energy value outputs for process control.

Future Trends and Potential Applications

Emerging trends include integration of mass spectrometric detection for improved selectivity, miniaturized and portable GC systems for on-site monitoring, and advanced software leveraging AI for automated peak identification and quantification. Coupling with multi-dimensional chromatography and real-time data analytics will further enhance refinery and natural gas quality assurance and process optimization.

Conclusion

The triple-channel Agilent 7890A GC method delivers rapid, accurate and comprehensive refinery gas analysis in six minutes, with extended capability for sulfur compounds and natural gas matrices. Its flexibility, sensitivity and automated reporting support diverse industrial applications in refining and gas processing.

References

1. ASTM D1945-03, Standard Test Method for Analysis of Natural Gas by Gas Chromatography, ASTM International.
2. ASTM D1946-90 (2006), Standard Practice for Analysis of Reforming Gas by Gas Chromatography, ASTM International.
3. UOP Method 539, Refinery Gas Analysis by Gas Chromatography, ASTM International.