PERFORMANCE DIAGRAMS
ALL YOUR DISTILLATION TRAY HYDRAULICS IN ONE PLACE
Daniel R. Summers, P.E.
Presented at the AIChE Annual Meeting
Distillation: Advances in Tray and Packing Technologies
Paper 228f
November 9, 2004
Austin, Texas
Unpublished
Abstract
The performance diagram is a graph of potential operation for a given distillation or fractionation tray geometry. The theory behind such a diagram is that once a particular distillation tray geometry is established (diameter, tray spacing, number of openings, downcomer size etc.) then a window of potential operation can be generated. If plotted on a volumetric basis, this window of potential operation is then independent of the operating system employed. In other words, this diagram can represent any separation and any operating pressure one wishes to subject the given tray geometry.
The performance diagram is a 2–dimensional plot using liquid volumetric loads as the x-axis and vapor volumetric loads as the y-axis. On these axes, several lines can be drawn to represent various hydraulic correlations. These lines form the “window” of potential operation where tray performance should be best. It is possible that on a single graph, all capacity and pressure drop curves can be represented such than an engineer or operator can easily and quickly determine if an operating mode is acceptable or even possible.
Background
Performance diagrams have been around for decades(1). The author has been asked to provide these diagrams for his tray designs since the late 1970’s. For many companies it is important to understand the full potential capacity of their equipment under ever-changing or even extreme conditions. The Performance Diagram is intended to provide the user with that ability to generate a graph of all potential operating points for a given tray geometry. It has been known for years that as long as the distillation equipment is operated properly, tray efficiency is fairly constant(2).Since distillation equipment operate at many different liquid and vapor flow conditions (and not simply constant liquid, constant vapor loads or constant L/V ratios) one needs to understand the full two-dimensional operating range of this equipment. Therefore, a two dimensional plot would represent the full operational potential of a piece of distillation equipment better than a linearly defined operating range.