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|State Police #||12-00544|
|Pollutant||Duration||Point Source||Greenhouse Gas||Criteria Pollutant||Ozone forming chemical||Amount of Release|
|Sulfur Dioxide||5d 20h 48m||OL-5 Elevated Flare (EPN 6-84)||NO||YES||NO||BRQ|
Accident Classified As: Below Reportable Quantity (BRQ)
On January 28, 2012 Shell Chemical's OL-5 Process Unit experienced an upset. This upset led to a false indication that there was flaring of acid gas at the OL-5 Elevated Flare (EPN 6-84). OL-5 experienced an unexpected high level in the DEA Stripper column trays due to plugging which carried over to the DEA accumulator. The elevated level in the accumulator forced a high pressure indication in the DEA overhead system and caused the flare valve to open to safely relieve the pressure on the system (as designed). However the liquid buildup in the overhead system due to this upset prevented any acid gas from being vented through the control valve to the flare. A review of the process data during the upset indication was a result of high liquid level in the overhead system.
It was confirmed that although the control valve had opened to the flare, no flaring through this path was possible as the overhead system was liquid full. The flare was smoking for 0 minutes according to Shell's initial and follow up reports. Once it was determined that the DEA Stripper was plugged and causing the flooding conditions in the overhead system, OL-5 Operations lowered the heat on the column and pumped the level in the accumulator down to lower the pressure indication/close the vent valve and stabilize the system. The DEA treatment system was shutdown and decontaminated for maintenance to completely clean the system. The cleaning removed plugging issues that lead to the unexpected flooding and high pressure indication in the overhead system. The DEA treatment system was safely returned to normal operating conditions once the cleaning activities were completed. Initial State Police Hazmat Hotline report states there was offsite impact, and up to time of call and 24-hour update there was still minor and occasional flaring. Shell's Notification Release Form states that occasional flaring may occur until system was returned to normal conditions.