Experimental study of mass transfer between the liquid and gas phases inside a portable wind tunnel used to estimate emission rates for odors compounds.

Name: Philipe Uhlig Siqueira
Type: MSc dissertation
Publication date: 29/08/2022
Advisor:

Namesort descending Role
Bruno Furieri Advisor *

Examining board:

Namesort descending Role
Bruno Furieri Advisor *
Igor Braga de Paula External Examiner *
Jane Meri Santos Co advisor *
Neyval Costa Reis Jr. Internal Examiner *

Summary: Wastewater treatment plants and landfills are major sources of odor in urban environments and,
despite not being necessarily associated with toxic and harmful effects on human health, this
pollutant causes annoyance. In wastewater treatment plants, the presence of liquid passive
emission sources is common, WHERE the direct method is one of the ways to quantify emissions
from these sources. The portable wind tunnel is one of the devices applied in the direct method
and this is characterized by the incidence of a carrier gas on the liquid surface through a flow
parallel to the surface, however, this equipment is not capable of simulating all the significant
phenomena for mass transport. Thus, mass transfer studies between the liquid-gas interface are
extremely important to understand the behavior of this device. Therefore, this work aims to
study the mass transfer at the liquid-gas interface inside the portable wind tunnel used to
estimate the emission rates of volatile odorant compounds from passive liquid surfaces through
the spectrophotometry technique. The results showed that, for hydrogen sulfide, the global mass
transfer coefficient (KL) did not change with different flow rates due to the non-disturbance of
the liquid phase, and it obtained an average value of 2,48×10-5 m s
-1
. No variation of KL was
noticed between the 6 sample points analyzed. When compared with field situations, which
were represented by the model proposed by Prata et al. (2018), the tunnel represented the same
mass flow for wind speeds of 5.85, 6.07 and 7.12 m s
-1
for upstream relative roughness of,
respectively, 0.005.0 .01 and 0.1 "m", considering the effective length of 50 m. As for the
effective length of 300 m, there was less influence of the relative roughness upstream, WHERE
the same respective roughness provided the same measured flow in the tunnel for wind speeds
of 5.30, 5.34 and 5.26 m s
-1
. The experimentally estimated coefficients (KL) were compared
with the empirical models present in the literature considering the flow conditions applied in
the laboratory. Therefore, it was found that the portable wind tunnel, when compared with these
models, overestimates the emission between 4.8 and 17.5 times. When comparing the values
presented in this work with the experimental data obtained by Santos et al. (2012), the
overestimation caused by the portable wind tunnel is also noted. It was not possible to analyze
n-butanol and acetic acid by the proposed methodology.

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