Inspection by THM on 03/24/2006
1) Plant Location:
Dupont Teijin Films, Cedar Creek Site (2600198), is located
on Highway 53 (
2) Plant Description:
Dupont Teijin Films is a batch chemical manufacturing facility that uses dimethyl terephthalate and ethylene glycol to manufacture polyethylene terephthalate (PET) chips, which are used to make film products and plastic material for various commercial products. The facility (2600198) is currently permitted under Air Permit No. 08907R03, effective from July 6, 2005, until June 30, 2010.
Adjacent to Dupont Teijin Films is a continuous chemical manufacturing facility that produces polyethylene terephthalate that is used to make bottle-grade plastic (DAK Resins, formerly Dupont Cedar Creek Site). The batch plant and continuous plant were split into two separate permits and premise numbers on July 26, 2000, as a result of a joint venture agreement between Teijin and Dupont for ownership of the batch plant.
Current Specific Permit Stipulations and Limitations:
1. Applicable Regulations: 2D .0503, .0515, .0516, .0521, .0524, .0535, .1100, .1806,
.0958, 2Q .0315 and .0711.
2. Requirement to submit emissions inventory at next permit renewal.
3. Allowable boiler particulate emission rates per 2D .0503.
4. Allowable particulate emission rates per 2D .0515.
5. NSPS Subpart Dc requirements.
6. Notification requirement, excess emissions/malfunction per 2D .0535.
7. Work practices per 2D .0958.
8. Toxics limits per 2D .1100 for acetaldehyde and 1,3-butadiene.
9. Odor requirement per 2D .1806
10. Synthetic minor for SO2 and HAPs.
11. PSD avoidance for SO2.
12. Limitation to avoid MACT Subpart JJJ.
13. Opacity limitation of 20 percent per 2D .0521.
14. Sulfur dioxide limitation per 2D .0516.
15. Inspection and maintenance for the bagfilters.
16. Inspection and maintenance of the scrubbers.
17. TPER values per 2Q .0711.
3) Pre-Inspection Conference:
On
March 24, 2006, Tom
a) Mr. Iwerks briefly discussed the facility’s production process for PET chips.
b) Mr. Iwerks indicated that at some time in the future he would like to further discuss the permit requirement to “track production” when the thermal oxidizer is not operating.
4) Inspection of the Batch Plant:
The facility operates 24 hours per day and 7 days per week. The plant reacts dimethyl terephthalate (DMT) with ethylene glycol to form polyethylene terephthalate (PET). The PET product is in the form of solid chips that are used to make film and various commercial products.
The reaction process involves two fundamental steps: (1) an esterification reaction, 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 using steam jet ejectors. The primary pollutant emitted from the esterification step is methanol, although smaller amounts of unreacted ethylene glycol are emitted as well. The primary pollutants emitted from the polymerization step are VOCs, including acetaldehyde (both a HAP and TAP). Source test data indicates that 1,3-butadiene (both a HAP and TAP) is not produced as a byproduct when making the film products. It had been a concern when the facility was making “bottle-grade” PET in the batch plant several years ago.
The DMT is a raw material that is received as a molten liquid in tank trucks, while the ethylene glycol is received as a liquid in rail cars. The DMT tends to degrade to produce methanol emissions. Therefore, a gravity spray scrubber (with ethylene glycol as the scrubbing liquid) followed by a demister is used to control emissions of DMT and methanol from the DMT storage. The remaining emissions after the scrubber are then routed to the batch plant’s thermal oxidizer. Without the scrubber the DMT would sublime and clog up the line to the thermal oxidizer. The facility is using the presence of flow in the scrubber and the liquid level in the scrubber feed tank to monitor performance. The DMT scrubber flow rate was 90 gpm (permit equipment list specifies at least 65 gpm).
Several years ago they repaired the 2nd DMT storage tank used as a backup. The permit renewal issued in 2005 modified the equipment list to show that a second DMT tank had become operational (each tank can hold 300,000 gallons). The backup tank had been out of service for many years due to a leakage problem related to the heating coils.
The facility has a crude methanol storage tank and a crude ethylene glycol storage tank that are used to collect these substances from the distillation recovery process. A venturi scrubber (with ethylene glycol as the scrubbing liquid) is installed on the crude methanol tank and the remaining emissions after the scrubber are then routed to the thermal oxidizer. The venturi scrubber flow rate was 4.5 gpm (permit equipment list specifies at least 2.6 gpm).
The distillation operation includes three distillation units that operate in parallel. A reboiler is used to heat the crude glycol and drive out the methanol in the distillation process. Although the emissions are vented to the thermal oxidizer, the distillation process includes an emergency release vent at the top of the unit with a flame arrestor for protection from the flammable methanol vapors.
The batch plant has 10 operating batch reactors used to produce the PET product and has averaged 8-10 lines of production during the year. The batch reactors began operation in the mid 1970s. Nine of the batch reactors were shut down several years ago, but one of these was brought back on-line four years ago. The ten reactors are used to produce chips for making product, with a maximum production of 120 million pounds per year. This year’s production is running at approximately 70-90 million pounds. Note that many years ago the reactors were used to make “bottle-grade” PET, which is now produced more efficiently in the nearby DAK Resins continuous PET plant. The advantage of the batch operation, as compared to the continuous operation, is in producing a variety of products for manufacturing different types of film or plastic materials. The continuous operation is more efficient for producing a single type of product.
A natural gas-fired thermal oxidizer (7.5 mmBtu/hr, ID No. CD-TO) is used to control emissions from the batch operation. The thermal oxidizer controls emissions from the process vents associated with the reactors, from the vacuum jet ejectors used to create a vacuum during the polymerization process, and from the recovery vents and storage tank vents. In addition, the thermal oxidizer controls the emissions from the gravity spray scrubber installed on the DMT tank, and the venturi scrubber installed on the crude methanol tank. The thermal oxidizer was operating at the time of the inspection at a temperature of 1170 degrees F. The permit requires a minimum temperature of 1100 degrees F for the thermal oxidizer.
In addition to the scrubbers, the permit equipment list includes bagfilters to control particulate emissions from the solids handling operations. The facility’s records indicate compliance with the inspection and maintenance requirements for the control devices.
5) Dowtherm Heaters:
The facility has two non-NSPS Dowtherm heaters and one NSPS Subpart Dc Dowtherm heater. Each unit can fire natural gas or No. 2 fuel oil. During the inspection one of the non-NSPS units (DTH-2) was operating firing natural gas with zero opacity, in compliance with 2D .0521. The other non-NSPS boiler unit (DTH-3) was not operating.
The NSPS Dowtherm heater (DTH-1) was in operation firing natural gas and the opacity was observed to be zero percent. The facility maintains records of the amount of fuel fired each day and the sulfur content of the fuel oil. However, the facility burns fuel oil infrequently. Their records indicate that they have not exceeded the NSPS sulfur content limit of 0.5 percent. Note that the three Dowtherm units share the same fuel oil tank and two of the Dowtherm units share the same stack.
6) Limitation to Avoid PSD for SO2:
The facility has submitted the required PSD avoidance reports in a timely manner and these reports indicate that they are in compliance with the avoidance limit of 100 tons per year for sulfur dioxide.
7) Toxic Air Pollutants and 2D .1100 Compliance:
The permit includes 2D .1100 limits for 1,3-butadiene and acetaldehyde. The acetaldehyde emissions are reduced by use of the thermal oxidizer. However, the primary purpose of the thermal oxidizer is to reduce HAP emissions (primarily methanol) to avoid MACT Subpart JJJ requirements and to remain synthetic minor for HAPs.
Note that the facility submitted a demonstration of compliance for 1,3-butadiene to the DAQ on October 11, 2000. Gregg O’Neal, DAQ Raleigh Central Office, reviewed the report.
As background on this issue, note that permit no. 04051R24, issued on Feb. 12, 1999 through to July 26, 2000, required that the facility utilize the thermal oxidizer at least 50 percent of the time on a monthly basis to comply with toxic air pollutant limits. However, this requirement was removed in permit no 08907R00 (issued on July 26, 2000, resulting in the separation of batch and continuous plants) since test data submitted in 1999 indicated that 1,3-butadiene emissions were not a concern for the batch plant.
Note that 2D .1100 of permit no. 04051R24 only required reporting for 1,3-butadiene, not for acetaldehyde. The review for that permit (prepared by Bob Daniel, dated Feb. 12, 1999) explained that the facility had submitted a compliance demonstration for acetaldehyde with the DAQ-approved source test results showing maximum emissions at 49.8 percent of the AAL. However, there had been concerns at that time about compliance for 1,3-butadiene. This pollutant was modeled using engineering calculations with maximum emissions at 99.6 percent of the AAL and without the use of any DAQ-approved source test data. Since FRO had concerns at that time about 1,3-butadiene, permit no. 04051R24 was issued with a requirement for quarterly reporting and that the thermal oxidizer be operated 50 percent of the time that the batch plant was operating (Bob Daniel, Feb. 12, 1999).
Due
to concerns about toxic air pollutant emissions, the facility conducted
additional source testing in 1999. As a
result, there appeared to be a significant change with respect to emissions of
1,3-butadiene. The testing indicated that this
pollutant is apparently only emitted from the production of bottle-grade PET
(not film-grade PET). Note that the
batch plant no longer produces bottle-grade PET, although it still has the
capability. (See the emissions test summary from Dupont received by FRO on November 9, 1999.) The test summary also discussed how the “GC
peak” previously associated only with 1,3-butadiene
now appears to be primarily propene. These two peaks are very close together and
were previously assumed to reflect only 1,3-butadiene
emissions. Note that propene
is a VOC, but not a hazardous air pollutant (HAP) or a
Since the new test data revised the earlier test data/analysis that was previously approved by the DAQ’s Gregg O’Neal, FRO requested that Dupont submit a demonstration of compliance. The objective was to give the DAQ stationary source compliance unit an opportunity to conduct a full review of the new data outside of the constraints of the 90-day permit clock. There was concern that the previously submitted test summary may not have contained sufficient data or procedures to serve as a demonstration of compliance. Mr. Iwerks submitted the new demonstration of compliance during the inspection on October 11, 2000. As further background on this issue, note that although permit no. 04051R24 required 50 percent utilization of the thermal oxidizer, the facility’s quarterly reports at that time indicated that the actual utilization was significantly higher. At that time it ranged from approximately 70 percent to 90 percent. However, since the change from Title V to synthetic minor (and the beginning of the MACT avoidance condition) the percent utilization has been significantly higher. As discussed below, the utilization during the past 12-month period exceeds the facility’s internal guideline to operate the unit at least 95 percent of the time
8)
Synthetic Minor and MACT Avoidance for Group IV
Polymers and Resins (Subpart JJJ):
Dupont Teijin Films is synthetic minor for SO2 and HAPs to avoid Title V requirements and to avoid MACT Subpart JJJ requirements for HAPs. For HAP emissions, this has involved utilization of the thermal oxidizer to control emissions (primarily methanol) beginning prior to the first compliance date for Subpart JJJ (Feb. 27, 2001).
The thermal oxidizer was operating at the time of the inspection at a temperature of 1170 degrees F. The permit requires a minimum temperature of 1100 degrees F. The supplemental fuel is natural gas. Mr. Iwerks is able to generate printouts indicating utilization of the thermal oxidizer that consistently stays above 95 percent for rolling 12-month periods. The facility’s internal guideline is to operate the unit at least 95 percent of the time. The facility’s consultant, John Stelling, previously prepared a spreadsheet showing that a 75 percent utilization of the thermal oxidizer during a 12-month period would result in HAP emissions nearly equal to 10 tpy HAP threshold level. The facility maintains documentation of thermal oxidizer down time as required by the permit.
9) Chemical Accident Prevention and 112(r):
The facility does not use any chemical listed under the 112(r) chemical accident prevention program in excess of its threshold quantity. Note that 1,3-butadiene and acetaldehyde are 112(r) chemicals. However, they are emitted as chemical by-products of the process, and are not stored as raw materials or products. As a result, the 10,000 pounds threshold level for these two chemicals is not exceeded. Therefore, the facility is not subject to the 112(r) program. In addition, they are not subject to OSHA’s Process Safety Management Standard.
10) Compliance Statement:
The facility appeared to be in compliance with all applicable air quality requirements at the time of the inspection. A review of their 5-year compliance history indicates they have not had any compliance problems.