(76a) Tray Stability at Low Vapor Load

Tower operation at low vapor rates is typically limited by the onset of weeping which can severely hurt tray performance. Many authors have attempted to study the onset of weeping on distillation trays as well as to determine the amount of weeping present. This paper will address this issue from a different perspective which is the uniformity of vapor passage through the tray deck at low vapor loads. It will be shown that there exists a relationship between the onset of weeping, tray performance, dry tray pressure drop and hydrostatic head of liquid on the tray. In addition, this relationship will be addressed with regards to single pass as well as multi-pass trays.