Problems at a processing unit caused the ExxonMobil refinery in Lockwood to flare gases to the air last week.
Flares are safety devices used to burn off excess gases but can be significant sources of pollution.
Montana Department of Environmental Quality’s Debbie Skibicki, an environmental engineer in the air compliance section, said the refinery reported the emissions as required to the DEQ and to the state emergency duty officer on Nov. 29. The refinery also is required to follow up in seven days with a written report.
There were two problems on Nov. 29. At about 8 a.m., a problem occurred at the fluid catalytic cracker, a main processing unit, Skibicki said. A second flaring event happened at about 12:30 p.m. involving a problem with a compressor that feeds the unit, she said.
ExxonMobil reported flaring an estimated 500 pounds of sulfur dioxide and 100 pounds of hydrogen sulfide during the episodes, Skibicki said.
ExxonMobil spokeswoman Pam Malek said, “We realize flaring may cause concern among the members of our community, and we apologize for that.”