The Determination of Sulfur Gases in Point Source Emissions of a Pulp Mill

Significance of the Topic

The Kraft pulping process releases multiple sulfurous byproducts that contribute to odor nuisance and air pollution. Monitoring hydrogen sulfide, methyl mercaptan, dimethyl sulfide, and dimethyl disulfide at regulated emission levels is essential for environmental compliance and process control.

Objectives and Study Overview

This application note presents a full-scan Saturn ion trap GC/MS method to simultaneously determine four sulfur gases in point source emissions at a pulp mill. The study aimed to demonstrate linear quantitation across regulatory concentrations and confirm compound identities via library matching.

Methodology and Instrumentation

Sample Collection:

• Heated probe inserted into stack gas stream collects emissions into Tedlar bags.
• Cooled phosphoric acid trap removes excess moisture before analysis.

Instrumentation:

• Gas Chromatograph: SPB-1 sulfur column (60 m × 0.32 mm, 4 µm film), helium flow 1 mL/min, oven ramp 40 °C (3 min) to 140 °C at 10 °C/min.
• Injector and valve ovens held isothermal at 170 °C and 260 °C respectively.
• Mass Spectrometer: Saturn ion trap, mass range 33–150 m/z, scan rate 2 scans/sec, temperature 260 °C, amplitude modulation voltage 3.8 V.

Main Results and Discussion

The SPB-1 column provided low bleed and excellent peak symmetry for all analytes. Calibration curves exhibited linear response from 1 to 800 ppm for each sulfur gas. Representative chromatograms of a recovery boiler sample showed well-resolved peaks, and mass spectra matched NIST library entries, ensuring accurate identification.

Benefits and Practical Applications

Using an ion trap GC/MS with PEEK sampling lines delivers sensitive, reliable multi-analyte quantitation at regulatory levels. The approach supports routine emission surveillance, regulatory reporting, and troubleshooting in pulp and paper industries.

Future Trends and Potential Applications

Advances may include enhanced ion trap detectors for lower detection limits, integrated automated sampling for continuous monitoring, and real-time data analysis for process optimization. Coupling with predictive analytics could further improve environmental performance and operational efficiency.

Conclusion

The described Saturn ion trap GC/MS method offers a robust, sensitive, and confirmatory approach to measure key sulfur gases in pulp mill emissions, meeting regulatory requirements and supporting environmental management.

References

No external literature cited in the original application note. Varian Application Note Number 42, 2010.