 |  Plant Design and Economics for Chemical Engineers, 5/e Max S. Peters,
University of Colorado
Klaus Timmerhaus,
University of Colorado, Boulder
Ronald E. West,
University of Colorado, Boulder
Optimum Design and Design Strategy
Chapter OverviewI
n engineering process design, the criteria for optimality can ultimately be reduced
to a consideration of costs or profits. The factors affecting the economic performance
of the design include the types of processing technique used, processing
equipment used, arrangement and sequencing of the processing equipment used in the
design, and the actual physical parameters for the equipment. Of course, the operating
conditions for the equipment are also of prime concern and import. Thus the optimum
for a process design is the most cost-effective selection, arrangement, sequencing of
processing equipment, and operating conditions for the design.
Optimization of process design follows the general aspects and processes for
optimization in general. First the optimization criteria must be established; this is done
by using an objective function that is an economic performance measure. Next, the
optimization problem must be defined. This requires the establishment of the various
mathematical relations and limitations that describe the aspects of the design. These
relations are used to explore their effects on the objective function, and then to determine
the optimal values of the parameters that affect the economic performance of the
design.
Although cost considerations and economic balances are the basis of most optimum
designs, at times factors other than cost can determine the most favorable conditions.
For example, in the operation of a catalytic reactor, an optimum operation
temperature may exist for each reactor size because of equilibrium or reaction rate limitations.
This particular temperature could be based on the maximum percentage
conversion or on the maximum amount of final product per unit of time. Ultimately,
however, cost variables need to be considered, and the development of an optimum
operation design is usually merely one step in the determination of an optimum economic
design. |
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2003 McGraw-Hill Higher Education