Page 84 - Design of Simple and Robust Process Plants

4.1 Process Synthesis 69
4.1
Process Synthesis

Process synthesis is the activity which sets the economics for the process for at least
the first part (if not longer) of its lifetime. Most process design improvements
occurred as the result of an evolutionary process, and in general a process is adapted
on three or four occasions during its lifetime in order to update it with respect to the
actual economic market and recent developments in technology.
In this chapter we concentrate on the development process, but advantage will
also be taken of developments in synthesis tools. The latter topic is currently under-
going a particularly rapid development cycle: consider the high availability of model-
ing tools that are available as static and dynamic simulations and optimizations for
process design, control design, and operation optimization. Despite the emphasis
that academia is placing on the development of the synthesis tools in the short term,
their contribution to industry will be limited, for the following reasons:
. The number of new designs is limited, as in general a process is retrofitted
several times during its lifetime. During such retrofits the degrees of free-
dom (DOF) are limited due to hardware and logistic situations that current
synthesis tools are incapable of handling. Currently, development exist to
address retrofit pinch analysis techniques for heat integration (Asante and
Zhu, 1996; Briones and Kokossis, 1996).
. The risk of design modifications for new designs that are acceptable from a
management perspective is limited. Businesses take risks with new designs,
and this can lead to losses over a period of months. In reality, improvements
are introduced in step-wise fashion. Licensors who build similar processes
have a better change for these gradual improvements, but they are also lim-
ited from a guarantee perspective.
. Grass-root process designs ultimately have many DOF, but these are also
restricted. The physical and kinetic data required for these designs often are
of very limited availability and need to be measured at laboratory scale. More-
over, they also require extensive verification if they are outside current opera-
tional experience, in order to minimize the risk.
The advantages of process synthesis techniques will be ± next to development of
grass root designs ± its application as instrument for process analysis and the identi-
fication for opportunities. They will show the direction in which process research
and developments should proceed. The requirements for sustainable technology
development are also setting opportunities which will drive for wider application of
synthesis tools.