(107e) Effects of a Trapped Trace Component on Operation of a Wastewater Stripper/Organic Recovery Tower

A wastewater stripper was installed in a production unit in 2005 to remove low levels of methanol and other light compounds to reduce the load of organics to the site wastewater treatment facility. To purify the stripped methanol for potential use in other processes or for outside sale, a rectification section was added to the stripper to hold down water and other heavy impurities. Shortly after startup, an inability to hold water down out of the distillate and a series of significant tower upsets were eventually linked to the presence of a previously unidentified low-concentration intermediate component that became trapped in the tower. Changes to the tower allowed stable tower operation and reduced the amount of water carryover. This paper describes the observed effects of a trapped component on tower operation including damage to tower internals, the vapor-liquid equilibria of the multicomponent system resulting in the trapped component, the operational changes that resolved the problem, and the circumstances and pitfalls that caused the problem to remain unidentified prior to startup.