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.
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.
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.