28 Power Engineering International July-August 2017 www.PowerEngineeringInt.com
Personal noise-protective equipment
‘Dispersal’ refers to what happens to the
pollution during and after its introduction into
the atmosphere, factoring in wind conditions
and atmospheric changes. Understanding
this can help people identify and control it. The
pollution may be visible as it leaves the plant,
but it soon becomes an invisible problem,
except where it forms as smog.
Bridging the gap
While mapping technology can’t directly
reduce emissions, the ability to accurately
map their sources and distribution can be
invaluable, as can virtual testing of mitigation
options before committing time and expense
Mapping software can be used to bridge
the gap between the science needed to
understand air pollution and the engineering
required to mitigate it. Air pollution dispersal
is a central focus for environmental
conservationists and governmental
environmental protection agencies (local,
state, provincial and national) in many
countries as a means of air pollution control.
Accurate wide-scale measurements of
air pollution are diffcult to get as, even when
assessed at several monitoring stations in
different locations, the terrain and weather
factors mean that levels can vary greatly even
in small areas. Therefore, instead of relying
on potentially inaccurate measurements,
mapping software allows a number of models
to be used to map air pollution dispersal.
These range from base models to ‘simple’
Gauss models – for approximate calculations,
e.g., to estimate background concentrations
or to make worst case studies, whenever free
fow conditions can be assumed around
emission sources – up to complex prognostic
models. The model selection depends strongly
on the task and the available data.
Air pollution models are highly dependent
on the meteorological situation for the
dispersal calculation, requiring multiple
meteorological scenarios. In order to correctly
assess the pollution load for average and
various percentiles, the principal concern is
simulating the dispersal of the pollutants for a
wide variety of wind directions and scenarios.
An added variant is that the air pollutants are
often reactive gases which change over time
under the presence of UV light.
As well as looking to improve the environmental
situation, the results of air pollution models are
often critical in planning processes and need
to be robust enough to withstand the scrutiny
of the court system. It is essential that they can
be validated and have well-defned boundary
conditions, are supported by a team of experts
and are used by well-trained people.
The management of meteorological
conditions and the control of different
scenarios are a constant focus for developers
and software improvements regularly mean
what was impossible yesterday might be
possible today. Measured meteorological
data must be extremely well assessed and
modifed very cautiously, especially if the
reference meteorological station is outside the
investigation area. Developers continually add
tools to assess, complete and modify data.
Consequently, air pollution mapping
software has become a powerful tool to
save time and avoid nasty surprises when
inspecting calculation results. Some software
includes diagrams to analyze background
pollution measurement and to deliver
supporting arguments to why the background
concentrations need to be adjusted.
If poor measurements cannot be rectifed,
this software helps visualize data problems
and supplies good arguments for better data.
Once air pollution has been accurately
mapped, then the software can be used to
test different mitigation options, which may
include carbon capture initiatives. Using the
software to test in this virtual way means that
all options can be tested without incurring
costs and the best methods can be selected.
Air pollution isn’t the only emission to be
concerned about in coal plants. Like the vast
majority of industrial premises, they are also
noisy. Noise emissions are considered harmful
if people are exposed to levels of 85 decibels
(dB) or above for a continuous period; a
sudden louder noise can also be detrimental.
Whether the impact is temporary or
permanent hearing loss or other physiological
or psychological effects, it can have serious
repercussions for the victim(s).
Mapping software can once again help.
Noise can be displayed in coloured maps,
making it easy to understand the sources and
propagation. They can also be produced in
3D and animated form so that the problem is
truly understood. The most advanced software
is sophisticated enough to map a single room
or an entire country.
Using the maps in coal plants, mitigation
measures, such as replacing turbine
equipment with quieter models, for example,
can be tested and the noise contour line
established. The line is the point at which
noise levels reach 85 dB and anyone crossing
it should be wearing personal protective
equipment, such as ear defenders.
Noise sources in coal plants vary widely in
sound power, emitted frequency spectra and
directivity, and also in their time dependency.
Using mapping software is more effective than
taking measurements as the software can
break down the sources and doesn’t just work
with the overall sound.
Controlling air pollution and noise
emissions from coal plants is not just about
being good for the environment, as important
as that is. Without taking action, the health
and safety of employees, visitors and local
residents is threatened. As well as the personal
impact, this can mean costly downtime and
potentially expensive litigation. Mapping
the issues and demonstrating the mitigation
measures taken can help reduce those risks.
Arne Berndt is owner/adviser at
SoundPLAN International, which makes
noise and air pollution mapping software.
for more information