Nov. 6 (Bloomberg) -- Royal Dutch Shell Plc reported a breakdown at its Dutch Pernis oil refinery, the biggest in Europe.

“There was a process upset in the western part of the refinery,” Wim van de Wiel, a Shell spokesman based at company headquarters in The Hague, said today by phone, declining to specify the units affected or when repairs are likely to be completed.

Earlier, the local environmental regulator said a furnace broke down, causing a “rotten egg” odor to surround the area. Shell released hydrogen sulfide in the incident, the company said on its Web site.

The Pernis plant, in Rotterdam’s refining hub, has the capacity to process 416,000 barrels of oil a day, according to data compiled by Bloomberg.

In the refining process, toxic hydrogen sulfide is produced in units that remove sulfur from petroleum. It’s typically later converted into sulfur or sulfuric acid.

To contact the reporters responsible for this story: Timothy Coulter at tcoulter@bloomberg.net Nidaa Bakhsh in London at nbakhsh@bloomberg.net

Last Updated: November 6, 2009 05:02 EST