"Trouble in a major Delaware City Refinery unit sent dark smoke billowing from a stack at the plant early [Tuesday] morning, triggering calls to regulators from nearby residents."

"A Department of Natural Resources and Environmental Control alert said the problem involved a combined energy recovery and pollution control system linked to PBF Energy’s petroleum 'coker,' a unit that extracts products from heavy, high-sulfur leftovers emerging from other parts of the complex.

Amy Roe, an area resident and Sierra Club Delaware chapter officer, said some residents had expressed concern about the smoke releases."

Jeff Montgomery reports for the Wilmington News Journal June 11, 2013. [2]