Batch Distillation Model By: Jason Hixson Jennifer Potter Wayne Johnson

dddddd Objective: To develop a batch distillation model that can accurately adjust a batch process to provide constant distillate composition. Problem: Batch distillation will have a variable bottoms concentration and minimum reflux ratio, therefore requiring a variable system operating line.

x, y Diagram Shows Vapor Liquid Equilibrium (VLE) Van Laar Fit Determines Theoretical Stages Perry’s Data Van Laar Model

x, y Diagram x B = Bottoms Composition x D = Distillate Composition 3 Theoretical Stages Required x B =0.24x D =0.85

Effect of Bottoms Composition Decreasing bottoms composition with time. x B =0.05 x D =0.73

Influence of Operating Lines x B =0.35x B =0.25x D =0.77x B =0.13 x d =0.77

Method Solve x, y Diagram for Binary Mixture Determine minimum Reflux Ratio (R D ) Vary R D by:  Setting theoretical stages = Actual Stages  Setting Distillate composition = constant

Model Requirement Input: Binary Mixture Heat Volume Pressure Trays D & B Composition Output: x, y Diagram R D vs. B M x B vs. B M D vs. B M

User Interface (UI) 12 previously solved mixtures. Van Laar Fit available for any binary mixture data “other”.

“Other” Model UI Requirements: x, y, T Data Antoine Constants  Log Based Physical Properties  Specific Volume  Heat of Vaporization

Precautions Requires Accurate Fit Azeotrope Complications

Model Output

Model Verification 12 tray distillation column. Power=2.7 kW Reflux varies to keep reflux temperature constant.

Model Results Controller Gain = 1 %/°C

Model Results Controller Gain = 9 %/°C

Conclusions Model accurately predicts required reflux ratio. Useful for column design and optimization. Future work – To vary column reflux ratio based on model output.