Refinery Gas Analysis Using the Agilent 990 Micro GC

Significance of the Topic

Refinery gas analysis (RGA) is a critical gas chromatographic technique for characterizing light hydrocarbons, noncondensed permanent gases and sulfur compounds generated during crude oil refining processes.
Accurate and rapid RGA supports process monitoring, emission control and quality assurance in refinery operations.

Objectives and Study Overview

This study evaluates two rapid RGA configurations based on the Agilent 990 Micro GC platform. The work compares a four-channel method for individual C6+ hydrocarbon speciation with a three-channel approach that provides total C6+ quantitation. The goal is to reduce analysis time while maintaining resolution and sensitivity.

Methodology and Instrumentation

Simulated refinery gas mixtures containing H2, O2, N2, C1–C5 paraffins/olefins, H2S and C6–C9 hydrocarbons were analyzed. Key parameters included rapid injection (40 ms), carrier gases (argon for molecular sieve channel; helium elsewhere), optimized column head pressures (100–300 kPa), temperature programming (80–150 °C) and precise backflush timing for selective elution.

Used Instrumentation

• Channel 1: 10 m CP-Molesieve 5 Å with traditional backflush for permanent gases (excl. CO2)
• Channel 2: 10 m CP-PoraPLOT U with backflush for CO2, C2 paraffins/olefins and H2S
• Channel 3 (four-channel solution): 10 m CP-Al2O3/KCl with normal backflush for C3–C5 paraffins/olefins
• Channel 3 (three-channel solution): 10 m CP-Al2O3/KCl with backflush-to-detector for C3–C5 paraffins/olefins and bundled C6+ peak
• Channel 4: 8 m CP-Sil 5CB straight column for detailed C6–C9 hydrocarbon analysis

Main Results and Discussion

Both configurations achieved total analysis times of 2–3 minutes for C1–C5 compounds; the three-channel method quantified total C6+ in under 2 minutes, while the four-channel method resolved individual C6–C9 species in under 3 minutes. The BF2D configuration improved peak resolution for C3–C5 olefins and yielded narrow peaks with high signal-to-noise ratios. Inert metal–deactivated flow paths ensured stable retention times and symmetrical peaks for active analytes like H2S at low ppm levels.

Benefits and Practical Applications

• Significantly shorter run times increase laboratory throughput and reduce operational costs
• High inertness and stability support reliable quantitation of sulfur compounds and unsaturated hydrocarbons
• Flexible configuration allows selection between detailed speciation and rapid total quantitation of heavy hydrocarbons
• Suitable for routine QA/QC, emission monitoring and process optimization in refineries

Future Trends and Applications

Further advances may include integration of micro GC with real-time process control systems, enhanced detectors for multi-component detection, mobile and portable analyzers for on-site measurements and data analytics tools for automated peak identification and trend monitoring.

Conclusion

The Agilent 990 Micro GC provides versatile, fast and robust solutions for refinery gas analysis. Choosing between three-channel and four-channel methods allows balancing speed and compositional detail to meet diverse operational requirements.

References

1. Duvekot C. Fast Refinery Gas Analysis Using the Agilent 490 Micro GC QUAD. Agilent Technologies Application Note. 2012;SI-02233.
2. Zhang J. Ultra-Fast Refinery Gas Analysis With a 490 Micro GC 3-Channel Configuration Equipped With a Backflush-to-Detector Option. Agilent Technologies Application Note. 2018;5994-0040EN.
3. Poole CF, Ed. Gas Chromatography. Chapter 5, Gas-Solid Chromatography. Elsevier; 2012.