Accurate sampling of PCDD/F in high temperature flue-gas using cooled sampling probes

Area of Science:

• Environmental Chemistry
• Combustion Science
• Analytical Chemistry

Background:

• Accurate measurement of pollutants like PCDD/Fs is vital for environmental monitoring.
• Flue gas sampling can be challenging due to high temperatures and potential artifact formation.
• Existing sampling methods may not adequately prevent contaminant generation at elevated temperatures.

Purpose of the Study:

• To evaluate the efficiency of two different water-cooled sampling probes in preventing artifact formation of PCDD/Fs.
• To compare a standard probe (EN-1948:1) with a modified sub-zero probe at high flue gas temperatures.
• To assess the impact of probe cooling capacity on PCDD/F concentrations in flue gas samples.

Main Methods:

• Laboratory-scale combustion reactor used for flue gas generation.
• Two water-cooled probes were employed: an original probe (EN-1948:1) and a sub-zero probe with salt/ice cooling.
• Internal probe temperatures were measured at 5cm intervals.
• Flue gas samples were analyzed for polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs).

Main Results:

• Higher PCDD/F concentrations were observed with the original probe at 700°C compared to the sub-zero probe.
• No significant differences in PCDD/F concentrations were found between probes at 400°C.
• Artifact formation of PCDD/Fs was confirmed at high temperatures with insufficient probe cooling.

Conclusions:

• Insufficient probe cooling during high-temperature flue gas sampling leads to artifact formation of PCDD/Fs.
• Enhanced cooling capacity, as provided by the sub-zero probe, effectively mitigates this artifact.
• These findings are critical for research in high-temperature post-combustion zones, though may not impact regulatory sampling of exit gases.