Wasson Chromatography Corner 15

Significance of the topic

Acid gas streams rich in H2S, CO2 and other contaminants require precise analysis to ensure safety, process efficiency and material compatibility in gas sweetening operations and industrial gas applications such as chlorine production and handling.
Proper detection of trace impurities prevents equipment degradation, supports regulatory compliance and guides treatment process optimization.

Objectives and Study Overview

This summary reviews three aspects presented in the Wasson-ECE newsletter: development of a rapid gas chromatography method for quantifying acid gas components using a dual TCD/TCD/FID configuration; analysis of trace impurities in gaseous chlorine employing thermal conductivity detection; and practical guidance for capillary column cleaning and maintenance.

Methodology

The acid gas analysis method uses sequential TCD and FID detectors on an Agilent GC to quantify hydrocarbons (C1-C5), permanent gases (CO2, O2/Ar, N2, CH4, CO, H2) with low detection limits under a six-minute cycle time.
Chlorine impurity analysis is performed in the gas phase with dual TCDs to measure CO2, O2/Ar, N2, CH4, CO and H2S at ppm levels, with system modifications to resist corrosion.
Column cleaning procedures involve sequential solvent rinses (methanol, methylene chloride or acetone, hexane) under controlled pressure and flow, followed by thermal conditioning to restore performance.

Instrumentation

• Agilent gas chromatograph configured with dual thermal conductivity detectors and a flame ionization detector
• Hastelloy valves and nickel tubing for corrosion resistance
• Proprietary stripper column for chlorine removal

Main Results and Discussion

The acid gas method achieved detection limits of 20 ppm for hydrocarbons via FID, 200-500 ppm for permanent gases via TCD, and 100 ppm for hydrogen on TCD2, with some partial coelutions of C5 olefins at rapid run speeds.
Chlorine impurity analysis reached low-ppm quantification thanks to corrosion-resistant hardware and the stripper column, ensuring detector integrity and reliable results.
Column cleaning guidelines demonstrated that proper solvent selection and flow control effectively remove persistent contaminants without damaging bonded phases.

Benefits and Practical Applications

• Rapid, simultaneous quantification of key gas components supports real-time process control in natural gas treatment and chlorine production
• Corrosion-resistant GC configurations extend instrument life when handling aggressive gases
• Standardized column maintenance protocols improve analytical consistency and reduce downtime

Future Trends and Potential Applications

Advances may include integrated automated cleaning systems, novel detector technologies with enhanced sensitivity, alternative stationary phases for improved selectivity, and on-site continuous monitoring for industrial gas streams.

Conclusion

Comprehensive GC methods combining robust hardware, optimized detector sequences and disciplined maintenance deliver reliable, low-level impurity data crucial for safety, regulatory compliance and process efficiency in acid gas and chlorine analysis.