Suncor reports nine emissions readings above listed limits at Commerce City refinery
The nine entries are measurements from four events, which Suncor attributed to equipment problems and operating changes.
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Suncor reported nine emissions readings above listed permit-condition limits during four operating events at its Commerce City refinery from Aug. 19 to Sept. 7, according to the company’s report covering Aug. 15–Sept. 15. Commerce City materials prepared for the City Council’s Nov. 9 study session also summarize the events and readings.
The nine entries are separate pollutant or operating-condition measurements, not nine incidents: one was listed on Aug. 19, four on Aug. 26, two on Aug. 29 and two on Sept. 7. The report lists these readings:
| Date and time listed | Unit or location | Measurement: listed limit → reported reading |
|---|---|---|
| Aug. 19, 5 a.m.–Aug. 20, 3 a.m. | Plant 1 Steam Plant, Boiler B-8 | Carbon monoxide (CO), 24-hour rolling average: 0.060 lb/MMBtu → 0.087 lb/MMBtu |
| Aug. 26, 7–8 p.m. | Plant 1 Hydrogen Plant, Tail Gas Incinerator H-25 | Sulfur dioxide (SO₂): 15.68 lb/hr → 20.9 lb/hr |
| Aug. 26, 9–9:24 p.m. | No. 1 fluid catalytic cracking unit (FCCU) | Opacity, six-minute rolling average: 20% → 25% |
| Aug. 26, 9–10 p.m. | No. 1 FCCU | CO, corrected to 0% oxygen: 500 ppmv → 605 ppmv |
| Aug. 26, 9–10 p.m. | No. 1 FCCU | CO: 500 ppmv → 524 ppmv |
| Aug. 29, 4–5 a.m. | Plant 1, No. 1 FCCU | CO, corrected to 0% oxygen: 500 ppmv → 762 ppmv |
| Aug. 29, 4–5 a.m. | Plant 1, No. 1 FCCU | CO: 500 ppmv → 739 ppmv |
| Sept. 7, 8–9 a.m. | Plant 1, No. 1 FCCU | CO, corrected to 0% oxygen: 500 ppmv → 761 ppmv |
| Sept. 7, 8–9 a.m. | Plant 1, No. 1 FCCU | CO: 500 ppmv → 729 ppmv |
Here, lb/MMBtu means pounds per million British thermal units, lb/hr means pounds per hour, and ppmv means parts per million by volume. Suncor describes the entries as emissions deviations. A reported deviation is not itself a regulator’s determination of a permit violation; the Colorado Department of Public Health and Environment reviews compliance through its air-quality enforcement process.
Suncor attributed the Aug. 19 boiler reading to elevated CO after boiler tuning the previous day. The company said operators adjusted the air supply, operating rate and burner settings, then reviewed and made further tuning adjustments.
For Aug. 26, Suncor said a failed valve in the hydrogen plant’s pressure-swing adsorption system caused an unexpected partial shutdown and operating instability. The company linked the instability to elevated sulfur dioxide at the hydrogen plant and opacity and CO readings at the FCCU. Suncor said crews stabilized the system and adjusted operations, then performed valve maintenance and installed software patches. The company reported that the unit returned to normal operation Sept. 11.
On Aug. 29, Suncor said an air-blower relief valve on the FCCU opened unexpectedly, reducing airflow and oxygen and raising CO. Operators adjusted blower settings and reduced the unit’s charge rate until oxygen and CO returned to expected ranges, the company said.
For Sept. 7, Suncor said operators reduced the FCCU charge rate after a heavy-cycle-oil pump developed noise and vibration ahead of maintenance. The reduced rate lowered regenerator temperatures; the company said it used torch oil to maintain operating conditions while CO readings rose. Suncor reported that maintenance replaced the pump’s damaged shaft and returned the pump to service.