Problem
A plastic injection molding company in Wisconsin is known as a
world-class leader in the industry for their secondary decorating
and assembly capabilities. One of their eleven facilities not only
performs plastic injection molding but also provides the
organization with decorating capabilities such as painting, laser
etching, laser marking, pad printing and assembly of automotive,
telecommunication and consumer products.
Over the years and through the 1990's the operation ran
successfully with a minor source air pollution control operation
permit. This permit consists of very specific requirements to meet
the Environmental Protection Agencies (EPA) LACT (Latest Available
Control Technology) regulation. These included restricted limits on
volatile organic compounds (VOC) per gallon of paint, catalyst,
thinner and cleaning solvent as purchased. This limited the types
of paints and colors they could offer customers but given the
customer needs and production volume at the time, this was a
manageable situation.
Action
As the business grew, requests by customers for more exotic
forms of paint and colors increased and they realized the need to
increase their paint capabilities in order to compete. In December
2000 they applied for two new permits with The Department of
Natural Resources (DNR), one for an air pollution construction
permit to install a new state of the art robotic paint line system
and the other for the ability to paint small metal parts. This
permit modification changed the facility from a minor source of
less than 100 tons per year of volatile organic compound emissions
to a major source with the potential to emit over 225 total
tons.
With the new permit, they not only had to meet the LACT
requirements for the painting of plastic parts but now also needed
to meet the MACT (Maximum Achievable Control Technology)
requirements for the painting of small metal parts. The MACT
requirements added a higher level of restrictions to VOC's per
gallon of paint as applied to metal parts. These restrictions were
applicable and once again manageable.
Although the new permit allowed them to meet additional painting
volume capacity requirements, they observed continued demand by
their customers for paints for which could not be used under the
air permit. Additionally, with the acceptance into the ISO
14001:1996 standards, they realized the need to significantly
reduce their VOC emissions.
The only way to meet the customer demands and reduce emissions
was to evaluate various forms of pollution control technologies. An
internal group was formed to explore the various control
technologies currently available on the market. Consideration was
given to equipment/concepts such as:
- Catalytic Oxidizers
- Thermal Oxidizers
- Regenerative Thermal/Catalytic Oxidizers
- Rotor Concentrator Coupled with a Regenerative Thermal
Oxidizer
- Microwave VOC Reduction Technologies
- Biofilter VOC Reduction Technologies
The company began to work very closely with the sales and
engineering team at Anguil and the DNR to establish the best
available control technologies to meet the pollution control
requirements. With some simple calculations, Anguil was able to
show how a Regenerative Thermal Oxidizer (RTO) would be the most
cost effective control technology for their current and future
process demands.
Solution
After thoroughly evaluating several suppliers the company
decided to go back to the Department of Natural Resources and
request a new air pollution control construction permit to install
a Anguil Model 400 / 40,000 SCFM (62,800 NM3/hr) Regenerative
Thermal Oxidizer (RTO) for their existing paint operations.
The oxidizer would achieve destruction through the
process of high temperature thermal oxidation, converting the VOCs
to carbon dioxide and water vapor while reusing released thermal
energy to reduce operating costs. Process gases, with VOC
contaminants enter the oxidizer through an inlet manifold. Dual
disk poppet valves direct this gas into energy recovery chambers
where the process gas is preheated, then progressively heated in
the ceramic beds as they move toward the combustion chamber.
The VOCs are oxidized in the combustion chamber, releasing
thermal energy in the structured ceramic media beds that are in the
outlet flow direction from the combustion chamber. These outlet
beds are heated and the gas is cooled so that the outlet gas
temperature is only slightly higher than the process inlet
temperature. Fasting acting, vertical poppet valves alternate the
airflow direction into the ceramic beds to maximize energy recovery
within the oxidizer. The VOC oxidation and high energy recovery
within these oxidizers reduces the auxiliary fuel requirement and
saves operating cost. For example, at 95% thermal energy recovery,
the outlet temperature may be only 70`F (40`C) higher than the
inlet process gas temperature with an RTO. The oxidizer can reach
self-sustaining operation with no auxiliary fuel usage at low
concentrations.
Allen Bradley, Programmable Logic Controllers (PLCs) control the
automatic operation of the oxidizer from startup to shutdown, so
minimal operator interface is required. These controls also provide
for remote telemetry to enable the system's operation to be viewed
and altered via a modem connection to reduce maintenance costs.
Later that fall the permit was accepted by the DNR for an air
pollution control construction permit to install an Anguil
Regenerative Thermal Oxidizer. Anguil Environmental Systems was
able to complete the design, fabrication, delivery, installation
and startup of the RTO so it could go on line early the next
year.
After startup of the new RTO, a stack test measured 99% destruction
rate efficiency for volatile organic compound (VOC) emissions at
100% capture. This equated to a net reduction of 58 tons of VOC
emissions in the first 6 months of operation.
The benefits of installing the RTO included the ability to offer
customers a large variety of paints and colors to meet their more
unique paint finish requests. Also, the RTO allowed the
manufacturer to use previously restricted thinners and paints to
better process their products with fewer rejects. This allowed the
business to grow and succeed in an increasingly competitive
environment and meet the new demands from customers while
significantly reducing the amount of volatile organic compounds
released into the environment.