Determination of the mass transfer coefficient of an odorant compound in a dynamic flow chamber

Name: Laize Nalli de Freitas
Type: MSc dissertation
Publication date: 02/08/2023

Namesort descending Role
Bruno Furieri Advisor *

Examining board:

Namesort descending Role
Ademir Abdala Prata Junior External Examiner *
Bruno Furieri Advisor *
Elson Silva Galvão Co advisor *
Igor Braga de Paula External Examiner *
Jane Meri Santos Internal Examiner *

Summary: Odorous compounds are pollutants present in the air, originating from various sources.
Diffuse sources, in particular, pose a challenge when it comes to quantifying their
emissions. Different techniques, categorized as indirect and direct methods, have been
developed to measure emissions from these sources. One commonly used device is the
Dynamic Flux Chamber (DFC) developed by the United States Environmental Protection
Agency (USEPA), which allows for enclosed measurements. In the context of this study,
the main objective was to investigate the global mass transfer coefficient of hydrogen
sulfide (H2S) within the USEPA DFC. Spectrophotometry was employed to analyze the
liquid phase during laboratory experiments conducted using the DFC. The calculated
mass transfer coefficient values for H2S ranged from 2.72E-06 m/s to 10.19E-06 m/s.
The impact of the mass transfer coefficient was evaluated under three different flow
rates (2.5 and 10 L/min), as well as the influence of the insertion of internal fans in
the chamber. The results revealed that the mass transfer coefficient was significantly
affected by the flow rates (p < 0.005), with higher flow rates leading to increased
coefficient values. Additionally, the presence of larger ventilators, in both flow rates,
also had a significant impact (p < 0.005) on the coefficient. These findings align with
previous studies, supporting the hypothesis that for hydrogen sulfide, which primarily
volatilizes through the liquid phase, the friction velocities at the liquid-gas interface and
in the liquid phase contribute to increased pollutant emissions and, consequently, higher
mass transfer coefficients. Another important variable that influenced the coefficient was
temperature, with higher values in both the liquid and gaseous phases resulting in higher
mass transfer coefficient values. Overall, this study contributes to a better understanding
of the mass transfer process and its influencing factors, providing valuable insights for
odor control and air quality management strategies.

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