Chemical Engineering July 2023 - 25

Part 1
Cover Story
Technologies for
Air-Pollution Control
Effective control technologies are crucial for mitigating the adverse effects of air pollution.
The selection of combustion-based or non-combustion-based technologies requires careful
consideration of numerous factors
Anoosheh Oskouian
and Anu D. Vij
Ship & Shore Environmental
A
ir-pollution control technologies
are critical for reducing
the
negative
impacts
of
industrial operations on
human health and the environment.
However, choosing between combustion-based
and non-combustion-based
technologies can be a
challenging decision, because both
approaches have their advantages
and disadvantages.
The detrimental effects of air pollution,
caused by various sources,
such as industrial emissions, vehicle
exhaust and biomass burning, have
spurred the development of innovative
control technologies. These technologies
aim to minimize the release
of harmful pollutants into the atmosphere
and improve air quality.
This article explores some of the
different combustion- and non-combustion-based
air-pollution control
technologies.
Depending on the
waste-gas pollutants being controlled,
the most suitable air-pollution
control system will require special
design, engineering, installation and
startup considerations.
The choice between combustionbased
and non-combustion-based
technologies can be a complex
decision-making process. Both approaches
have their advantages and
disadvantages, and
the
selection
depends on various factors, such as
the specific pollutants being targeted,
the characteristics of the emission
source and location-specific regulatory
requirements. Factors like energy
efficiency, operational costs, waste
management and the potential for
secondary pollutant formation also
play a significant role in the decisionmaking
process. In some cases, a
combination of technologies may be
required (Figure 1).
Combustion-based technologies,
such as fluegas desulfurization and
selective catalytic reduction, utilize
controlled burning to convert pollutants
into less harmful substances.
Non-combustion-based technologies,
including electrostatic precipitators,
wet scrubbers and various
filtration systems, focus on physical
or chemical methods to capture
and remove pollutants from the
gas stream. The following sections
outline some of the most prevalent
pollution-control technologies in industry
and provide some guidance on
their applications.
Non-combustion technologies
As stated previously, non-combustion
pollution-control technologies
typically will involve a chemical or
physical process designed to eliminate
polluting species and prevent
their associated environmental harm.
There are numerous such technologies
in use in industry today in a
broad range of applications. It is important
to note that aerial gaseous
streams are not the only source of air
pollution - contaminated water and
soil can also contribute.
Soil vapor extraction (SVE) systems.
SVE systems employ a technique
that removes contaminants
and hazardous vapors from the soil
subsurface. It uses vacuum pressure
to pull air through soil that has been
saturated with hydrocarbons or volatile
organic compounds (VOCs). SVE
can be combined with a thermal oxidizer
(see below) to further treat any
remaining pollutant gases.
Chemical scrubber systems. When
chemical scrubber systems are used,
there is thorough contact between
the gas stream to be treated and
water in the presence of a chemical
reagent. The treatment capacity of
the scrubber depends on the type
of waste-gas pollutants found in the
process. For instance, if H2S is found
in the waste gas, caustic treatment
with an oxidation chemical is
required.
If NH3 is found in the waste
gas, sulfuric acid with an oxidation
chemical is required. If organic comShip
& Shore Environmental
FIGURE 1. The selection of the best technology for air-pollution control - or combination of technologies
- depends on many factors beyond the pollutant profile, including energy efficiency, secondary pollutant
formation and more
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