May 8, 2012:

Imperial Oil Ltd. (IMO)’s Sarnia oil refinery in Ontario began several weeks of maintenance on one of its units on May 7, local radio station CHOK Country said on its website yesterday. The plant’s coker unit was taken out of service on May 6, resulting in a plume of thick black smoke that lasted a couple of hours that morning, CHOK said. Other units will remain in operation, the radio station said. The refinery can process 121,000 barrels a day, according to data compiled by Bloomberg.

Imperial didn’t immediately return a phonecall to the Calgary, Canada-based company’s media relations department before normal business hours today.

By Bloomberg