(229a) Factors Affecting Overall Tray Efficiency

Kister, H. Z., Fluor Corporation

Despite decades of work on tray efficiency and the variables affecting it, engineers are still not clear what is fact and what is myth. Many of the efficiency studies have been contradictory, others have focused on observations derived from laboratory-scale towers that do not fully extend to commercial towers. With much experience gathered in the industry over the years, and a large volume of commercial-scale data released by FRI, there is enough information in the published literature to obtain a closer evaluation of the factors that affect overall tray efficiency. This paper reviews these factors and the extent to which they affect commercial-scale fractionators. It was found that errors in VLE and flow path length often have a significant effect on tray efficiency. On the other hand, factors such as weir height that intuitively are expected to affect overall tray efficiency are only minor contributors. It is hoped that this paper will provide engineers with a guide to the factors they should focus on when revamping a commercial-scale tower or designing a new one.