The column unit may be used to simulate a liquid-liquid extraction unit. Although liquid-liquid extraction columns are generally not trayed, the distillation column nomenclature is used and the term tray denotes an equilibrium stage. A liquid-liquid extraction column normally contains at least two trays but Single Tray Columns are allowed.
There is no limit on the Number of Trays that may be considered in a column model. The trays are considered linked, with the light liquid from each tray entering the next higher tray and the heavy liquid from each tray feeding the next lower tray. Every liquid-liquid extraction column model must have feeds to the top and bottom trays. The pressure for every tray in the model must be defined in the Column Pressure Profile Window.
Feeds and Products
A column may have any number of feeds, with a feed to any tray. All columns must have at least two products, an overhead product leaving tray one and a bottoms product leaving the highest numbered tray. Optionally, columns may have light or heavy liquid phase side products withdrawn from any tray. The Column Feeds and Products Window gives additional information regarding column feeds and products. It is also possible to create Column Pseudoproducts corresponding to column internal flows.
Heat Sources and Sinks
Column Side Heaters/Coolers may be attached to any tray to add or remove heat.
Performance Specifications
Specifications on column products, internal flows and tray temperatures may be used to determine the values for column operating variables including feed rates and heat duties. There must be a calculated variable for each specification as described in the Column Specifications and Variables Window. Specifications are discussed in the Generalized Performance Specifications .
Calculation Algorithm
The Liquid-Liquid is selected from the Column Algorithms in order to specify a liquid-liquid extraction column. The algorithm is iterative in nature starting from Column Initial Estimates which you supply and/or internal estimation techniques. You may supply tuning factors and revised convergence criteria for the algorithm as described in the Column Convergence Data Window and may change the limit on the number of calculated trial solutions. See Number of Iterations for more details.
Reactive Distillation
Chemical reactions can be modeled on column trays for the Liquid-Liquid Column Algorithms. See Reactive Distillation for more details.
Thermodynamic Systems
The system selected in the Column Thermodynamic Systems Window must be an activity method which can model the equilibrium between two separate liquid phases.
Distillation Column Unit Operation - Technical Information