Retrofit design for increasing the processing capacity of distillation columns 1. A hydraulic performance indicator

Increasing the throughput of an existing distillation process is an important objective of retrofit design of distillation processes. When the throughput is increased, entrainment flooding may create a bottleneck in the column. Important goals of retrofit design are to identify and remove such a bottleneck. This work develops an analysis tool for retrofit design of distillation columns. A new measure, fractional utilization of area (FUA), is proposed to identify the extent to which the area available for vapour flow on an existing stage of the column is utilized. The area utilization is assessed relative to an acceptable approach to flooding conditions in the column section. FUA is defined as the ratio of the area required for vapour flow on a stage to the maximum area available for vapour flow in the column section. An FUA curve, indicating area utilization on every stage in the column, can be generated from converged simulation results and existing sizing correlations. The FUA curve is a useful analysis tool, as it allows the bottleneck in the column to be identified and allows the effectiveness of proposed modifications to be evaluated.