Column Profile Maps: A Tool for the Design and Analysis of Complex Distillation Systems
Date
2006-10-31T08:29:11Z
Authors
Holland, Simon Thornhill
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Abstract
Techniques for the design and analysis of simple column separations are well
established. Shortcut design techniques have been employed in the initial design of
these “traditional” distillation systems for a number of years and these columns are
well understood. However, few currently available techniques are useful in the
design of novel or complex configurations. The techniques that are available tend
to be configuration specific. An all inclusive or universal, design and analysis tool,
that can be applied to any and all configurations, is required.
Tapp et al (2004) introduced Column Profile Maps (CPMS) as a means of
addressing this issue. These are maps of composition profiles for column sections
with defined net-molar-flow and reflux ratio. It is suggested that by producing
CPMs for a configuration a designer can essentially superimpose these, determine
feasible operating profiles and hence column operating parameters.
In this thesis we show that this technique can be used to, not only produce quick
and easy complex column designs but gain a comprehensive understanding of the
steady-state operation of these arrangements. We demonstrate this analytical
potential first by application of the CPM technique to the two-product feed
distribution problem. It is shown that feed distribution can lower the minimum
required reflux ratio for non-sharp separations and in some cases produce feasible
separations from previously infeasible product specifications. A composition
region of operation for all distributed feed policies is also found.
The potential for detailed analysis, design and optimisation of complex
configurations is demonstrated via application of the CPM procedure to the fully
thermally coupled (Petlyuk) distillation column at both sharp and non-sharp split
conditions. A detailed design methodology for any configuration results from this.
It is found that the Petlyuk column can operate under five possible bulk/net flow
conditions and that very interesting and counter-intuitive net-molar-flows are
possible. A feasible column parameter region equivalent to the optimality region
(Halvorsen and Skogestad, 2001) is found for zeotropic systems. Importantly a
minimum reflux condition for the Petlyuk column is found. This condition can be
applied to all zeotropic systems for all product specifications. It is also
demonstrated that the CPM technique can be used for design optimisation of
separation systems.
Description
Student Number : 9510423G
PhD Thesis
School of Chemical and Metallurgical Engineering
Faculty of Engineering and the Built Environment
Keywords
distillation, column profile maps, petlyuk, difference point equation, distributed feed, complex distillation configurations, separtion synthesis