SOUR WATER STRIPPERS EXPOSED

摘要

Sour water strippers (SWS) are moderately-large reboiled or live-steam-injected towers (30 to 60 trays) in which ammonia and other gases are removed from the sour water by steam stripping. Heretofore they have been designed using equilibrium stages. However, tray efficiencies have remained obscure with quoted values anywhere from 15% to 45%, a factor of three range. Designers therefore have less than complete confidence in the reliability of their final design. The consequence of uncertainty is either overdesign and, therefore, excessive costs or sleepless nights because of an underperforming unit. Recently a mass transfer rate-based simulation model has become available for designing and troubleshooting sour water strippers. In this paper, we use the model to determine tray efficiencies for ammonia and H_2S stripping, how they vary across the height of a tower, and what operating variables affect them. We also predict quantitatively how the presence of heat stable salts affects the treat-ability of sour water to specified residual levels of ammonia and H_2S.