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Louisiana Refinery Accident Database

Shell Chemical East (26336), Norco

LDEQ Accident Report

Pollutants Released

Accident Classified As: Reportable Quantity

Cause of Problem: Process Upset

On the morning of August 31, 2013, Shell Chemical's OL-5 Process Unit experienced a higher than normal level of carbon monoxide (CO) in the furnace feed. The additional unexpected CO in the feed came from Enterprise, a supplier of feed to OL-5, and as a result of recent decoking activities. The higher level of CO was initially consumed by the Product Hydrogen and Converter Hydrogen Methanators, however, this did not resolve the issue. Without taking action, continued high levels of CO would have led to the ethylene product going off specification which in turn would have led to substantial additional flaring. Therefore, as per normal operating procedures, OL-5 opearations began routing the high AC converter stream to the flare to lower the CO levels in the process in an effort to prevent a further, more severe, upset in the OL-5 Process Unit. Once the AC converter effluent was within specifications, it was routed back to normal operation.

Discharge Preventable - No

The increase in carbon monoxide in the furnace feed was unexpected.

Notes/Remedial Actions

To minimize impacts, OL-5 operations adjusted unit operations in order to consume the excess CO in the Product Hydrogen and Converter Methanators. Once the Product Hydrogen and Converter Hydrogen Methantators became overwhelmed, OL-5 operations immediately diverted the AC converter effluent to the OL-5 flare system. Operations then used a different source of hydrogen that did not contain elevated carbon monoxide. Once the AC converter effluent was within specifications OL-5 operations positioned the stream back to its normal routing, eliminating flaring. An investigation is occurring. The results will be incorporated, where applicable, into the standard work processes at the OL-5 unit to prevent recurrence. Shell Chemical confirmed that reportable quantities for carbon monoxide, nitrogen oxide, and High Volatile Organic Compounds were exceeded. In addition, the maximum permitted limits were exceeded for carbon monoxide, nitrogen oxide, particulate matter, and volatile organic compounds at the OL-5 elevated flare. Shell admitted that Carbon Monoxide exceeded RQ for August 31, but not Sept 1. Carbon Monoxide exceeded RQ on both dates. Similarly, VOCS exceeded RQ for both Aug 31 and Sept 1, but was only reported as exceeding for the first. VOCs are mislabeled as HRVOCs (highly reactive VOCs).