(124d) Troubleshooting a Benzene Splitter Capacity Limitation

A Benzene/Toluene Splitter in the aromatics Solvent Extraction Unit of a Refinery was experiencing a capacity limitation. The maximum achievable throughput corresponded to tray loads that fell short of the expected flood point. Attempts to increase throughput would result in increased pressure drop in the top part of the column together with higher than desired toluene in the benzene side-draw. This presentation will review the test runs, diagnostic scans and other troubleshooting steps that were performed to better understand the column constraints. One of the key observations was an unexpected high liquid level on the benzene partial draw tray. Careful consideration of the test run and other diagnostic data led to a number of recommended tray modifications. These modifications were implemented and following start-up the column was able to achieve significantly higher throughput without increased toluene in the benzene. One of the interesting aspects of this case study was the interaction that was observed between the column and side-draw receiver due to the location of an equalizing line nozzle.