The continuous plant, also referred to as the M12 process, operates 24 hours per day and 7 days per week to produce bottle-grade polyethylene teraphthalate (PET). The plant reacts teraphthalic acid (TPA), and smaller amounts of isophthalic acid (IPA), with ethylene glycol to form polyethylene teraphthalate. (PET). The plant produces approximately 40,000 pounds per hour of product. The PET product is solid chips that are purchased by other companies to make plastic bottles. The reaction process involves two fundamental steps: (1) an esterification reaction where the carboxylic acids (TPA and IPA) are reacted with the glycol (ethylene glycol) to form the ester; and (2) a polymerization reaction where the smaller molecules are combined to form the long polymeric chain. The esterification reaction occurs at atmospheric pressure, while the polymerization reaction is carried out under vacuum. The process includes a wastewater stripper that is designed to remove VOCs and use them as a supplemental fuel in the Dowtherm heaters. The primary pollutants emitted from the continuous process are VOCs, including acetaldehyde and 1,3-butadiene.

The ethylene glycol is received as a liquid in rail cars. The PTA and IPA are received as powders, but are converted to slurries at the beginning of the reaction process. The continuous plant began operation in 1996, and its operation at that time resulted in the eight bottle-grade PET reactors in the nearby batch plant being taken out of service back when the DAK Resins site and the Dupont Teijin site were both part of Dupont Cedar Creek.

The emissions from the continuous plant are controlled by two scrubber/condenser systems (ID Nos. 94-2 and 94-08). One of these scrubbers (ID No. 94-02) is installed on the seal pot vent which emits VOCs (including 1,3-butadiene and acetaldehyde) generated from the esterification portion of the continuous process. The other scrubber is installed on the ejector hot well, which vents emissions associated with a polymerization portion of the continuous process. In addition the polymerization process includes a glycol wells header/hotwells vent. The glycol wells header is a common emission point for four separate emission units (the UFPP hotwell, the finishing hotwell, the secondary spray hotwell, and the glycol hold tank).

After esterification and polymerization, the resulting PET goes through several more process steps including chipping, crystallization, preheating, solid state reactor processing, cooling, and transfer to storage silos. These finishing steps generate particulate emissions that are controlled by five bin vent filters, three cyclones associated with precrystallization/crystallization, a cooler bagfilter, and a vacuum bagfilter. In addition, there is a bagfilter installed on the three cyclones associated with precrystallization/crystallization.

The precrystallization/crystallization process emits acetaldehyde emissions that are controlled with a catalytic oxidizer. The catalytic oxidizer was installed in 2001 to allow the facility to qualify as synthetic minor for acetaldehyde and to qualify for a MACT avoidance condition (Group IV Polymers and Resins). The facility has a computerized system to monitor the performance of the chemical process and the catalytic oxidizer.

The continuous PET plant is subject to the requirements of NSPS Subpart DDD (VOC Emissions from the Polymer Manufacturing Industry). The facility demonstrated compliance with the NSPS limits during source testing conducted in 2001 and approved by the Raleigh Central Office. For the esterification portion of the process, the NSPS requirements include a limit of 0.04 kg of TOC per million grams of product from the seal pot vent. For the polymerization portion of the process, an NSPS limit of 0.02 kg of TOC per million grams of product applies to the sum of emissions from the glycol wells header and the ejector hotwell. In addition, the facility is reqired to maintain the required records of the daily measurements and the 14-day rolling average of the ethylene glycol in the liquid effluent from the ejector hotwell to demonstrate compliance with the NSPS limit of 0.35 percent ethylene glycol by weight.

Two NG/No. 2 oil/No. 6 oil-fired boilers (each 222 million Btu/hr)

One NG-fired boiler equipped with low NOx burners and flue gas recirculation (100 million Btu/hr, NSPS Subpart Dc)

Two NG/No. 2 fuel oil-fired Dowtherm heaters.

DAK Resins purchased the wastewater treatment plant and boilers that were previously owned by Monsanto Company. This addition to the plant is usually referred to as the “DAK Resins Services Complex”. The wastewater treatment plant receives wastewater from both the DAK Resins process and the nearby Dupont Teijin process. It uses neutralization, air oxidation, aerobic digesters, and clarifiers for wastewater treatment. The wastewater analysis looks at broad parameters such as BOD/COD. The wastewater pollutants from both DAK Resins (acetaldehyde and ethylene glycol) and Dupont Teijin (acetaldehyde, ethylene glycol, and methanol) are included for SARA 313 reports since that program specifically requires addressing what comes from other plants.