Coal liquids distillation tower corrosion: Chloride pathways in the Wilsonville, Alabama SRC-I pilot plant when processing a high chloride coal

Abstract

The pilot plant was operated during a three-week period with a coal containing about 0.25 wt.% chloride. During this period, samples were collected at about 20 sample points throughout the process. The mass balance and chloride content of these samples provided data to define the chloride pathway to the atmospheric distillation tower where it subsequently caused severe corrosion problems. A fortuitous processing change, made about half-way through the period, provided a marker that helped define the chloride pathway through the process. About 10% of the chloride entering the dissolver flashed overhead in the high pressure separator; this fraction remained constant even thought the total chloride entering this separator area changed by a factor of 5 to 10. In the Wilsonville plant about 50% of the total chloride entering the reactor was carried to the atmospheric tower in the highest boiling distillate process stream. Essentially all of the chloride entering the atmospheric tower was converted to iron chloride by corrosion of a lower portion of the tower.