Coal Liquids Distillation Tower Corrosion. Chloride Pathways in the Wilsonville, Alabama SRC-1 Pilot Plant when Processing a High Chloride Coal

摘要

The Wilsonville pilot plant experienced severe corrosion (> 1,000 mils/year) in the atmospheric fractionation column when processing a high chloride (0.25 wt. %) coal. The operators found that the addition of sodium carbonate to the coal feed greatly reduced this corrosion but designers of a commercial plant could not use this corrosion control method. Hence, it was necessary to define the chloride pathway through the process. Samples collected during a brief operation without carbonate addition permitted a tentative conclusion about the chloride pathway. To provide a more definite pathway, the plant was operated for a three week period with a high chloride coal and samples were collected daily at more than 20 crucial sample points. Analysis of these samples clearly defined that the chloride pathway to the atmospheric fractionator was in the highest boiling distillate stream from the vacuum distillation column. A processing change near the mid-point of the three week run provided a marker to trace chloride through the process and provided further support for the pathway. Amines provide a transport mechanism for the chloride and provide, in addition, through thermal dissociation and recombination in fractionation columns, a mechanism for concentrating chlorides in a narrow region in the columns.