(442c) Retrofit of Distillation Columns Together with Their Heat Transfer Devices

Distillation columns are integral to most chemical processes. Increasing the throughput of an existing column can create significant economic benefits. However, capacity limits (or bottlenecks) of the column and its associated heat transfer devices must be considered when throughput is increased. Retrofit options for distillation processes include modifications, such as feed conditioning, intermediate heat exchange and adjusting operating conditions. Hydraulic analysis tools have been developed to screen for effective retrofit modifications based on column hydraulic performance.  However, the effects of these modifications on the performance of heat transfer devices associated with the column have not been investigated. This research considers bottlenecks in the reboiler if the feed to the column is increased.  A systematic approach for distillation retrofit is proposed using process simulation, hydraulic analysis and heat transfer models. These models capture interactions between the column and associated heat transfer devices. The new methodology complements existing column retrofit methodologies by systematically generating and evaluating options to overcome bottlenecks in the reboiler when column throughput is increased.  A case study illustrates the approach.