BP Plc spokesman Scott Dean said part of the refinery was evacuated although no one was hurt. The residual hydrotreater remained closed following the fire, but the rest of the refinery's units, including crude distillation and gasoline plants, were operable. The residual hydrotreater uses hydrogen to remove sulfur from crude oil residuals before they are processed in refining units. Crude oil residuals are heavy, tar-like portions of a barrel of crude oil.