Parallel GC for Complete RGA Analysis

Significance of the Topic

Refinery gases are complex mixtures that require rapid and precise quantification in refinery operations and quality control.

Objectives and Study Overview

This study presents an updated configuration for the Agilent 7890A GC featuring a fifth valve and parallel detection channels to achieve a complete refinery gas analysis in under six minutes.

Methodology and Instrumentation

• Single Agilent 7890A GC instrument configured with three parallel channels: an FID for C1–C5 hydrocarbons, a TCD with helium for permanent gases, and a TCD with nitrogen or argon for enhanced hydrogen detection.
• 10-port valve assembly with a backflush pre-column (DB-1) to remove late-eluting C6+ compounds, eliminating the need for splitters.
• Separation columns including HayeSep Q and molsieve 5A cages for light hydrocarbons and permanent gases, HP-PLOT Al2O3 for hydrocarbon isomers, and an EPC module for precise flow control.
• Capillary flow union connectors to streamline column and valve integration and improve peak shapes.

Main Results and Discussion

The optimized method achieves baseline separation of C1–C5 isomers (22 distinct compounds) and simultaneous detection of permanent gases within six minutes. Detection limits reach 50 ppm for most analytes and 500 ppm for hydrogen sulfide. The dedicated TCD channel for hydrogen improves linearity and sensitivity compared to helium.

Benefits and Practical Applications

• Rapid analysis suitable for atmospheric overhead, FCC gases, fuel gas, and recycle streams.
• Comprehensive profiling of hydrocarbons and permanent gases in a single run without additional temperature programs.
• Automated data processing via ChemStation macros compliant with ASTM, GPA, and ISO standards for mole%, weight%, and volume% reporting.
• Enhanced process optimization and quality control in refinery and petrochemical settings.

Future Trends and Potential Applications

Advances in detector sensitivity, miniaturized valve systems, and real-time analytics may further reduce run times and expand analyte coverage. Integration with process analytical technology (PAT) and machine learning offers prospects for predictive maintenance and adaptive process control.

Conclusion

The updated parallel GC approach on the 7890A platform provides a fast, robust, and high-resolution refinery gas analysis. Its modular design and automated reporting support diverse industrial applications and strict quality assurance protocols.

References

• Wang, C. Parallel GC for Complete RGA Analysis. Agilent Application Brief 5989-6103EN, 2007.
• ASTM D1945-03. Standard Test Method for Analysis of Natural Gas by Gas Chromatography. ASTM International, 2003.
• ASTM D1946-90 (2006). Standard Practice for Analysis of Reformed Gas by Gas Chromatography. ASTM International, 2006.
• UOP Method 539. Refinery Gas Analysis by Gas Chromatography. ASTM International.