Thermal oxidation systems can treat vapor-rich and wastewater streams by injecting them into the oxidization process. Gulf Coast Environmental Systems (GCES) designs vapor-tolerant and aqueous regenerative thermal oxidizer (RTO) systems to handle these difficult streams. GCES's three-canister RTOs achieve over 99% destruction and elimination rates (DRE) and safely perform required "bake-out" cleaning cycles. GCES has installed multiple RTO systems for rendering and other industrial applications, gaining experience to optimize their designs for vapor-laden and wastewater processes.

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Thermal Oxidation of Liquid / High Moisture Processes
A Comparison of Vapor-Tolerant and Aqueous RTOs
Chad Clark, Technical Director
January 2016
Contents
Introduction ...................................................................................................................................................................1
Oxidizer Technology.....................................................................................................................................................1
Ceramic Media ..............................................................................................................................................................2
RTO Configurations......................................................................................................................................................3
Vapor-Tolerant Systems................................................................................................................................................4
Aqueous Systems ..........................................................................................................................................................5
Experience.....................................................................................................................................................................6
Conclusion.....................................................................................................................................................................6
Rendering Application Case Study................................................................................................................................7
Oxidizers treat VOCs, HAPs and other air
contaminants based on proven technology and
history. Engineering these systems to the next
level allows them to process vapor-laden streams
and even the destruction of wastewater. Known as
the “go-to” guys for rendering solutions, GCES
systems perform reliably in these harsh
environments. Based on this, GCES aqueous
systems treat wastewater using the same
principles, by injecting the water into the process
stream.
Introduction
Vapor-rich and wastewater waste streams pose challenges in treatment systems. Thermal oxidizers utilize
the combination of heat and time to combust pollutants into harmless CO2 and water. Drawing on these
proven designs and principles, and from hundreds of fielded units, Gulf Coast Environmental Systems,
LLC (GCES) provides robust, economic solutions to these challenges. Some of the most harsh pollution
control applications are in the rendering field of the food processing industry. The waste stream can
contain odors, ammonia, fats, grease, water and other vapors, and even particulate matter, all in a wide
ranging mix. GCES’ systems handle these difficult processes on a daily basis, 24/7. Wastewater
destruction systems are similar, but are actually more controlled and steady. The process is controlled
through metered injection of the water into a pre-heated inlet stream into the oxidizer for complete
destruction using the standard oxidation process. GCES is ready to solve your pollution problem.
Oxidizer Technology
Thermal oxidizers, or thermal incinerators, are combustion devices that control VOCs, CO, and volatile
HAP emissions by combusting them to carbon dioxide (CO2) and water. Thermal oxidizers are similar to
catalytic oxidizers (catalytic oxidizers use a catalyst to promote the oxidation reaction). Important design
factors include temperature (a temperature high enough to ignite the organic constituents in the waste
stream), residence time (sufficient time for the combustion reaction to occur), and turbulence or mixing of
the combustion air with the waste gas.1
1
US EPA, http://cfpub.epa.gov/oarweb/mkb/contechnique.cfm?ControlID=17

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Early applications of air pollution control equipment consisted of a direct-fired oxidizer (TO), also
referred to as an afterburner. A properly designed TO is capable of providing reliable destruction (95% or
greater) of the emissions while operating at temperatures of 1200°F or higher.
In the early 1980’s, a new technology of air pollution control was developed. The technology still
revolved around the process of thermal oxidation, but used the action of heat sink regeneration to recover
most of the waste heat. This technology was called Regenerative Thermal Oxidation (RTO). Early units
achieved around 90% heat recovery efficiency, while modern units regularly achieve efficiencies of 95-
97%. The advancement and adoption of heat recovery media significantly enhances the ability to reduce
the energy required to heat up the incoming vapor-laden and condensed wastewater streams.
Ceramic Media
Early heat recovery ceramic media used in RTO Systems was
typically a 1” saddle. These saddles are randomly packed in the
energy recovery beds to a depth of about 8’. This type of media
leaves many voids and areas where condensable organics and
particulate would build up. Coupled with the high initial pressure
drop that is an inherent property of saddles, this results in high
electricity costs due to the large horsepower motors required to push
the air through the ceramic media beds.
Modern ceramic heat recovery media is manufactured as a “structured” ceramic block, which has a higher
density and greater amount of surface area per cubic foot compared to saddle media. These features result
in a smaller area and lower depth (typ. 4’ – 5’) of the bed while achieving the same amount of heat
transfer efficiency. Structured ceramic media also has a reduced pressure drop for the air passing through
each bed, typically 4” water column (w.c.) vs. 8” w.c. or higher for saddles. This lower pressure drop
reduces the size of the fan required, consequently reducing the energy used.
Structured Media Block Detail of Structured Media

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RTO Configurations
There are three different types of RTO system configuration: single-canister, two-canister and three-
canister designs. Canister or can refers to the number of physical chambers which hold the ceramic heat
recovery media. Each design has individual advantages and drawbacks. Single-canister RTOs occupy a
small footprint and have the lowest initial procurement (CAPEX) cost, but have higher maintenance
(OPEX) costs. Two-canister RTOs have a low CAPEX and more efficient maintenance, while generating
a DRE of up to 98-99%. Three-canister RTOs are better suited to bake-out processes, have a high DRE
of 99% or higher, but have a larger physical footprint.
Three-can RTO systems are the best solution for vapor-tolerant and aqueous applications. The high DRE
in excess of 99% insures the odor and organic material is nearly completely destroyed. In rendering
applications, in order to remove the odor and constituents from the cooker air stream to a level of
undetectable emissions, a DRE over 99% is required. A single-canister RTO comes close to achieving
99% DRE, but can’t remove all odors. Two-canister RTOs experience a brief “puff” of untreated process
stream from the RTO during cycling of the chambers, which allows a minimal yet detectable release of
odor. The third chamber in a 3-canister RTO allows for one chamber being purged with clean air during
cycling, eliminating the “puff”, pushing the DRE over 99%. The additional cost of this third chamber is
negligible, making the 2-chamber RTO an improbable option.

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Vapor-Tolerant Systems
Typical oxidizer applications process a gaseous waste stream. Some special applications require the
handling of a waste stream laden with water vapor and/or other moisture or residues and possibly
particulates and other solids.
The food processing industry is one of these applications. Rendering is a process that converts waste
animal tissue into stable, value-added materials. Rendering applications require the destruction of organic
and wastewater emissions (odor, ammonia, fats, grease, and particulate) emitted from the cooker process.
These are carried over as liquid and warm air with up to 100% humidity.
Due to the amount of condensable organics and wastewater being emitted from the cooker, a residual
layer of fats, grease, and oils will build up on the ductwork, valves, and inlet ceramic media of an RTO
unit. Over time, this buildup will create conditions of flammability in the RTO. To mitigate the risk of
fire, a “bake-out” cycle is used to remove such buildup in a controlled manner during a preset schedule.
A bake-out cycle revolves around varying the timing of the inlet and outlet valves and using the heat in
the RTO to dry and incinerate the residue to ash.
Performing the bake-out of the residue safely and under a controlled method prevents undue stress and
damage to the RTO system. A three-canister RTO system is ideally suited to bake-out cycle applications
and handles bake-outs better than single or two-canister RTOs. In a three-canister system, minimal
smoke and odor is released to atmosphere during the bake-out cycle; single or two-canister units will
release visible smoke and odor. Additionally, three-canister RTOs utilize butterfly valves to control the
process cycles, which are better suited to the high temperature exposure of the bake-out cycle as
compared to the poppet valves of a two canister RTO or the rotor plate of a single canister RTO.
Due to the high temperature exposure
of bake-out cycles and the acidic and
moisture/vapor-laden nature of the
incoming exhaust stream, stainless
steel is used to fabricate the cold
condensable areas of the RTO unit.
The incoming ductwork, valves,
ceramic media supports, outlet
ductwork, fan, and exhaust stack are
exposed to the condensable liquids and
corrosive elements of the air stream.
These are manufactured from stainless
steel or other corrosion resistant alloys
(CRA).
Instrumentation, controls and safety
systems are also adjusted to
accommodate the more severe, moisture laden process stream. Due to the volatility and variety of the
process stream, the control system has special accommodations to maintain system performance across a
wide variety of operating conditions.

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The combination of these materials, components, design considerations and manufacturing techniques
extend the service life of the equipment, minimize maintenance, and insure reliable performance.
Aqueous Systems
GCES developed its aqueous oxidizer systems to handle the unique requirements vaporizing and
destroying the contaminants in wastewater. With some of the same challenges as vapor-tolerant systems,
aqueous systems are actually a more controlled version. Where a vapor-tolerant system such as those in
rendering applications noted above can see a wide variety of vapor content, residues and other
contaminants, an aqueous oxidizer processes the water in a controlled, metered manner. The particulate
that is presented in rendering applications also provides for a more challenging design compared to an
aqueous system.
The basic oxidizer is the same as a normal configuration with the added fluid-handling capability. This
consists of pumps, mixing and storage tanks as needed, spray/injection nozzles and associated piping and
controls. This system provides controlled injection and processing of the water into the inlet stream for
processing through the oxidizer, using heat from the combustion chamber to help vaporize the fluid.
Automatically synchronizing air flow, water pressure and flow, process temperature and pressure
provides steady-state, reliable operation.
As shown in the diagram, the process inlet to the RTO comes off the evaporated hot-air recirculation line
from the RTO combustion chamber. This is a controlled injection of the moisture unlike rendering
applications where water carryover cannot be controlled.
To handle potential moisture collection
due to condensation in the inlet
ductwork, fan and exhaust stack,
condensate drains are installed to allow
drainage of the liquid during
maintenance. These drains for an RTO
typically consist of multiple tap points
with manual shut-off valves and piping
routed to an appropriate drain.
The system includes the same bake-out
feature as the vapor-tolerant system.
The frequency of such bake-outs is
dependent on the make-up of the waste
water stream. If it contains organics,
oils and other solids or residues, these
cycles may be more frequent.
Similarly, CRA materials are used to
manufacture the cold condensable areas
of aqueous RTO units, including
incoming ductwork, valves, ceramic
media supports, outlet ductwork, fan,
and exhaust stack.

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Experience
GCE has installed several generations of RTO technology for vapor-tolerant, rendering applications.
Through the knowledge gained with each installation, there are many design and construction details that
are unique and important to properly fitting the unit to the application. GCES is referred to as the go-to
supplier of RTOs for the rendering industry. See the Appendix for a case study of a rendering
application.
Customer
Name/Project
Industry
Capacity
SCFM
Capacity
Nm³/h
DRE
Process
Type
Reg
or Std
Location
Value
(USD)
(000)
Install
Date
Sacramento Rendering Rendering 12,000 18 939 98% Odor Std USA $300 2003
Darling International Rendering 10,000 15 783 99% Odor Std USA $400 2004
Darling International Rendering 10,000 15 783 99% Odor Std USA $400 2004
Foster Farms Rendering 6,000 9 470 99% Odor Std USA $400 2006
West Coast Reduction Rendering 20,000 31 566 99% Odor EU Canada $700 2007
Ocean Protein Rendering 20,000 31 566 99% Odor Std USA $700 2008
Darling International Rendering 10,000 15 783 99% Odor Std USA $400 2014
Conclusion
Thermal oxidizers are a proven, reliable method of treating air pollution. GCES has taken this to the next
level for treating vapor-rich waste streams and even wastewater destruction by carefully considering and
implementing critical factors such as materials, controls, media, instrumentation and system
configuration. Vapor-tolerant systems are the more difficult solution due to the inconsistency in the
volume and make-up of the vapor, liquid, residue, and other contaminants in the waste stream. With over
half a dozen of these RTO systems reliably operating around the globe, GCES is known as the “go-to”
guys in the industry for this severe application. Drawing on these experiences and principles, GCES’
aqueous systems flawlessly process wastewater streams through careful blending, heating and injection.
Let GCES design and build the solution to your vapor or wastewater problem today.
The Author
Chad Clark is the Technical Director at
GCES, with over 16 years of experience
in pollution equipment and construction.
Clark manages GCES’ product portfolio
and works with customers to develop
optimal solutions to their unique
pollution abatement applications. He
holds a Mechanical Engineering degree
from Vanderbilt University. Gulf Coast Environmental Systems
1689 Hawthorne Dr
Conroe, TX 77301 USA
Tel +1 (832) 476-9024
Fax +1 (855) 301-9672
www.gcesystems.com

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APPENDIX:
Rendering Application Case Study
DARLING INGREDIENTS (2004 / 2014)
Darling Ingredients (formally Darling International) is one of the largest animal by-product processing
groups in the world. For odor abatement, the industry had used direct-fired Thermal Oxidizers since the
1970’s. In 2004, GCES worked closely with Darling to develop and implement a new variation of odor
abatement using a Regenerative Thermal Oxidizer (RTO) to improve performance while reducing plant
operating costs.
GCES provided 10,000 SCFM RTOs to two (2) separate Darling plants. Due to the capital budget
constraints of updating two (2) plants, the client opted to construct the combustion/heat sections of the
systems out of carbon steel. Even within this highly corrosive environment, a solid 10 years of
continuous operation was provided by the equipment. GCES was able to design, build and install these
systems with an ROI of six (6) months or less.
When the need to replace
the combustion/heat
sections of the unit arose,
Darling turned
exclusively to GCES for
a solution. In 2014,
GCES built a new
stainless steel RTO body.
Our field crew integrated
this with the existing
RTO unit – in a four (4)
day turnaround,
continuing Darling’s
successful operation with
their application-specific
GCES rendering series
equipment.
GCES 10,000 SCFM 3-Canister RTO for Darling
Contact:
Dave Bizzanelli
Darling Ingredients, Inc.
11946 Carpenter Road
Crows Landing, CA 95313
Tel. (209) 667-9153
dbizzanelli@darlingii.com
Gulf Coast Environmental Systems
1689 Hawthorne Dr
Conroe, TX 77301 USA
Tel +1 (832) 476-9024
Fax +1 (855) 301-9672
www.gcesystems.com