A thesis submitted to the Faculty of Engineering, University of the Witwatersrand,
Johannesburg, South Africa in fulfilment of the requirements for the degree of
Doctor of Philosophy. / The aim of process synthesis is to select process equipment and interconnections in
order to achieve some performance goal, such as the composition of one or more
products, in an optimal manner. This work focuses on the synthesis and
optimization of vapour-liquid equilibrium (VLE) separation processes.
The regions of feasible products for a range of VLE separation processes (including
simple distillation, simple condensation and processes comprised of one or two flash
stages and mixing) are determined and analyzed. Binary and ternary systems, both
ideal and non-ideal, are considered. It is shows .at the products of VLE separation
processes are not inherently restricted; limitations in product composition are
therefore introduced by the choice of separation equipment. The products on the
boundary of the region of feasible products are often found to be associated with
infinite costs. Therefore costs and, product composition should he considered
simultaneously in process synthesis.
This work introduces a pair of variables which are proposed as cost indicators for
VLE separation processes. These variables, which are called "capacity variables",
pertain to distillation columns and a wide range of other VLE separation processes,
allowing their comparison. The variables incorporate both capital and energy costs
of a process and are thus related to total annual costs. They accommodate costs of
both boiling and condensing. They ate simple to calculate from the mass balance
equations. The capacity variables are analogous to mean residence time, which
serves as a cost indicator for processes invoi ving reaction.
The capacity variables are evaluated for a range of processes separatins binary and
ternary mixtures and a range of thermodynamic systems. The capacity variables
reflect the impact of the operating parameters, such as product specifications and
reflux ratio, on process costs. In distillation processes, the optimum reflux ratio is
found to be close to the beuristic value of 1.2 times the minimum reflux ratio. The
capacity variables are proposed as useful tools for the initial stages of process
synthesis. / Andrew Chakane 2018
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:wits/oai:wiredspace.wits.ac.za:10539/25855 |
| Date | January 1996 |
| Creators | Jobson, Megan Ruth |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | application/pdf |
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