Sources familiar with plant operations said earlier that the refinery was running all production units, with the 45,000-bpd coking unit completing on Wednesday its first 24-cycle run since the refinery was shut by the storm.

"The refinery is now at normal operations," said Exxon spokeswoman Charlotte Huffaker.

Exxon restarted the coking unit on Tuesday finishing a restart of production units at the Beaumont refinery that began on Sept. 25.

Portions of the refinery were heavily flooded by intense rainfall from Harvey.

Prior to the coker's restart, the refinery had been running, but at reduced production levels.

Two drums of the eight-drum coker had been filled with petroleum coke sludge as floodwaters from Harvey's intense, heavy rain disrupted steam supply to the unit, the sources said.

The two drums had to be cleared of the sludge before the unit restarted, according to the sources.

Cokers convert residual crude into motor fuel feedstocks or petroleum coke, which can be used as a coal substitute.

To make petroleum coke, residual crude is spun at high speed under high temperature in long drums. The crude hardens into coke on the walls of the drums, which are pulled out at 24-hour intervals. Then the coke is cut away from the drums by high-pressure, high-temperature water jets.

The residual crude comes from the crude distillation units.

(Reporting by Erwin Seba; Editing by Marguerita Choy)