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Seminars
Process
Operability
Professor Christos Georgakis
Department of Chemical and Biological Engineering
Tufts University
When: Thursday, November 9, 2006
Time: 2:30 PM to 3:30 PM
Where: 1070 Duncan Hall
Abstract:
It is well known that the effectiveness of a chemical process is dependant
both on its steady state and its dynamic characteristics. Traditional approaches
address the issue in a sequential manner, by first designing the plant from
the steady state point of view and addressing the dynamic characteristics
and the controller design tasks after the plant is built. This often results
in a substantially over-designed and sub-optimal plant with dynamic and
control characteristics that are difficult to handle with simple single-input-single-output
controllers. Efforts to build more optimal and less polluting processes
have resulted in the introduction of a substantial number of heat integration
schemes and a large number of recycle streams, making the process more complex
than before by several orders of magnitude. Such processes are very difficult
to operate or are totally inoperable, unless their dynamic and control characteristics
are examined very early in the design phase. The need to examine the interaction
between process design and control has recently started to be recognized
in the literature.
This seminar presents a new and systematic approach that examines
the operability of a plant design prior to its physical construction.
This enables the examination of the operability characteristics of several
alternative
designs and suggests design changes that improve process operability.
It can also be used to quantify the characteristics of an existing plant
to
achieve increases in plant productivity and flexibility. The
proposed operability measure is multivariable and nonlinear, based on
concepts such as the Available
Input or the Expected Disturbance Spaces and their transformations
by either the steady state or dynamic model of the process. After the
initial definition
of the new concepts, the proposed approach is applied to several
example unit operations such as reactors and multi-unit processes, concluding
with
the examination of a plant-wide problem. The extension of the
operability concept to non-square systems is used to design the output
constraints for
Multivariable Model-based controllers.
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