Chemical Engineering July 2023 - 27

Ship & Shore Environmental
Ship & Shore Environmental
Final thoughts
In conclusion, 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, and many pollutioncontrol
applications may require tailored
solutions that align with specific
needs and regulatory requirements.
Ultimately, the goal of air-pollution
control is to minimize the release
of
harmful
FIGURE 3. In certain direct-fired thermal oxidizers, it is possible to recover heat and potentially use waste
streams as fuel gas
temperatures sufficiently low to avoid
the reformation of thermal oxides of
nitrogen (NOx). A quench media is
required to minimize the temperature
of subsequent stages, and recycle
fluegas (RFG) provides maximum
heat recovery.
There are two primary processes
for the subsequent stages in a multistaged
thermal oxidizer: one process
uses two additional stages (for a total
of three stages). The initial stage is the
reducing stage. A second stage is a
quench stage, employing a quench
media to cool the initial stage fluegas
to about 1,400°F, and a third oxidation
stage uses air for final oxidation of
the combustibles.
The second process has two
stages consisting of the initial reducing
stage, employing RFG for
quench, and a second oxidizing
stage whereby RFG and excess air
are combined and injected into the
fluegas from the initial stage. The
two-stage process is usually an improvement
over the three-stage
process, because it reduces costs
of an extra refractory-lined chamber
and simplifies control of the
staged process.
Catalytic thermal oxidizers. Catalytic
systems dilute waste gases
with a destruction efficiency of 95
to 99% at an operating temperature
of 700 to 800°F. Thermal efficiencies
of 50 to 65% can be achieved
with use of a heat exchanger. Catalytic
thermal oxidizers can be subject
to poisoning, sintering and masking,
and the catalyst is often very
expensive to replace. This system
is not recommended for abating
waste-gas emissions.
Recuperative thermal oxidizers.
Recuperative systems are suitable for
applications with VOC concentrations
of 10 to 35% LEL with moderate to
high solvent emissions. Recuperative
thermal oxidizers can achieve a destruction
efficiency of over 99%, and
use a shell-and-tube heat exchanger
with thermal effectiveness of up to
70%. This system can result in high
operating costs if there is a LEL solvent
load of less than 15%.
Steam-generating thermal oxidizer
(SGTO) systems. SGTO systems
are designed so that a standard twopass
firetube boiler with certain modifications
can be utilized as an effective
air-pollution control system to destroy
VOCs. Part of the process emissions
are sent through the combustion air
blower of the boiler burner. The remainder
is passed to the incinerator
section at the rear of the boiler. In this
manner, the infrared heat released
by combustion is utilized in the boiler
furnace. Thus, the SGTO is more efficient
than the DFTO waste-heat boiler
system. It also requires less space.
Selective catalytic reduction
(SCR). SCR units are widely used in
power plants and industrial facilities to
control NOx emissions. SCR systems
work by injecting a reducing agent,
typically ammonia or urea, into the
fluegas stream. As the gas passes
over a catalyst, NOx molecules react
with the reducing agent, converting
them into nitrogen and water vapor,
which are less harmful to the environment.
SCR systems have shown
significant success in reducing NOx
emissions and are particularly effective
when combined with other pollutioncontrol
technologies.
CHEMICAL ENGINEERING WWW.CHEMENGONLINE.COM
JULY 2023
pollutants
into
the
atmosphere,
improve air quality and
protect human health and the environment.
The urgency to address
air pollution is amplified by the interconnectedness
of environmental
challenges, with air pollution exacerbating
climate change and vice
versa. By reducing air pollution, we
not only improve air quality but also
contribute to the global effort to
combat climate change and create
a sustainable and habitable world for
future inhabitants. ■
Edited by Mary Page Bailey
Authors
Anoosheh Oskouian is president
and CEO of Ship & Shore Environmental,
Inc. (S&SE; 2474 North
Palm Drive, Signal Hill, CA 90755;
Phone:
562-997-0233; Email:
anooshehm@shipandshore.com),
a woman-owned business specializing
in air-pollution capture and
control systems for industrial applications.
Ship & Shore helps
manufacturers meet volatile organic compound abatement
challenges by providing customized air pollutionabatement
systems for various industries. Oskouian is
the environmental industry's only female CEO. She has
expertise in air-pollution abatement and energy recovery,
with over two decades of experience in industrial and
commercial project construction of air design and fabricating
combustion equipment, including thermal and
catalytic oxidizers, boilers, burners, carbon and zeolite
absorption mechanisms.
Anu D. Vij is chief operating officer
(COO) of Ship & Shore Environmental,
Inc.
(same address
as
above; Email: avij@shipandshore.
com; Website: www.shipandshore.
com). Vij has over 20 years of experience
in the environmental,
chemical, petrochemical and airpollution
control industries, and
has specific expertise in thermal
oxidation technologies. As COO of Ship & Shore, he oversees
several business units, including Sales, Engineering,
Project Management, Procurement and Production.
Prior to joining Ship & Shore, Vij directed several engineering
teams at different companies. He holds a
M.S.Ch.E from the University of Southern California, and
a B.S.Ch.E from Panjab University in India.
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Chemical Engineering July 2023

Table of Contents for the Digital Edition of Chemical Engineering July 2023