Fast Refinery Gas Analysis System Based on the Agilent 7890B GC System and G3507A Large Valve Oven Using Micropacked Columns

Significance of the Topic

Refinery gas analysis is critical for process optimization, safety, and compliance in hydrocarbon processing facilities. Accurate and rapid quantification of light hydrocarbons, permanent gases, and sulfur species supports control of downstream operations and environmental monitoring.

Objectives and Study Overview

This work demonstrates a three‐channel analysis system based on the Agilent 7890B GC combined with a G3507A large valve oven (LVO) utilizing micropacked columns. The goal was to achieve a complete refinery gas analysis—including C1–C6+ hydrocarbons, permanent gases, hydrogen, and hydrogen sulfide—within approximately 8.5 minutes while ensuring high stability and reproducibility.

Used Instrumentation

• Agilent 7890B Gas Chromatograph (main oven)
• G3507A Large Valve Oven with up to six heated valves
• 1/16-inch UltiMetal micropacked columns (permanent gases and H2S)
• Alumina PLOT column (C1–C6+ hydrocarbons)
• Flame Ionization Detector (FID)
• Thermal Conductivity Detectors (TCD) – rear TCD (He), side TCD (N2)
• Pressure control modules and split/splitless inlet

Methodology and Procedure

The system uses three separate channels: Channel 1 (FID with alumina PLOT) for C1–C6+ hydrocarbons, temperature-programmed in the main oven; Channel 2 (TCD in LVO, isothermal at 70 °C) for permanent gases and H2S on micropacked columns; Channel 3 (side TCD using N2 carrier) for hydrogen. The main oven ramped from 60 °C to 190 °C, while the LVO remained isothermal to prevent oxygen adsorption effects. Valving configurations direct samples through appropriate detectors with minimal dead volume.

Main Results and Discussion

Repeatability studies over 45-run sequences yielded retention time RSDs below 0.1% and area RSDs under 0.7% for key components. Oxygen response remained stable over time, avoiding the decline observed in temperature-programmed porous polymers. The total analysis time averaged 8.5 minutes. Quantification limits met typical RGA thresholds (0.01 mol% for hydrocarbons, 500 ppm for H2S). Minimal peak asymmetry was noted at high concentrations but did not impair quantitation.

Benefits and Practical Applications

• Rapid, simultaneous multi-component analysis in under 9 minutes
• Independent control of LVO and main oven enhances stability
• Micropacked columns balance speed and capacity
• Reliable detection of oxygen and sulfur species
• Scalable valve configuration for complex separations

Future Trends and Potential Applications

Advances may include integration with online process monitoring, expansion to heavier hydrocarbons, coupling with mass spectrometry for speciation, and further miniaturization of valve ovens. Automated data analysis and real-time feedback loops are expected to enhance refinery control and safety.

Conclusion

The implementation of the G3507A large valve oven with micropacked columns on the Agilent 7890B GC platform delivers a fast, robust solution for comprehensive refinery gas analysis. Isothermal control of the permanent gas channel and independent temperature programming ensure high reproducibility and stable oxygen response, fulfilling stringent industry requirements.