Quantitative gas composition analysis method for a wide pressure range up to atmospheric pressure-CO₂ plasma case...

Area of Science:

• Analytical Chemistry
• Physical Chemistry
• Plasma Science

Background:

• Accurate gas composition analysis is crucial for understanding chemical processes, especially in reactive environments like plasma torches.
• Traditional mass spectrometry sampling systems can suffer from gas demixing, leading to inaccurate concentration measurements.
• Quantifying carbon dioxide (CO2) conversion efficiency requires precise measurement of reactant and product gases.

Purpose of the Study:

• To present a novel mass spectrometer sampling system designed for accurate gas analysis over a wide pressure range.
• To demonstrate the system's capability in measuring relative concentrations of CO2, carbon monoxide (CO), oxygen (O2), and nitrogen (N2).
• To validate the system's performance through a case study of CO2 conversion in a microwave plasma torch.

Main Methods:

• Development of a custom mass spectrometer sampling system with one fixed and one variable orifice.
• Optimization and calibration of the mass spectrometer for analyzing CO2, CO, O2, and N2 mixtures.
• Implementation of a conversion determination routine to calculate relative molar flows and distinguish between CO and N2.

Main Results:

• The custom sampling system enables gas composition determination in the pressure range of 5–1000 mbar with low gas-demixing (<1.5%).
• The optimized mass spectrometer achieved an absolute error of less than 1.6% for measured CO2 conversion to CO.
• The system successfully distinguished between CO and N2, crucial for accurate CO2 conversion calculations in mixtures or with air impurities.

Conclusions:

• The developed mass spectrometer sampling system offers high accuracy and low gas-demixing for gas composition analysis across a broad pressure range.
• The system provides a reliable method for quantifying CO2 conversion in plasma processes, with demonstrated low absolute error.
• This technology is valuable for applications involving gas mixtures, air impurities, or precise monitoring of CO2 conversion.