Page 90 - Design of Simple and Robust Process Plants

4.1 Process Synthesis 75
. Application of interactions between the different development layers; break
with the doctrine of solving problems sequentially.
. Reduction of the size of the synthesis problem by dividing the process into
sections for optimization (see Sections 4.1.4 and 4.1.5).
. Inclusion of idea generation as a place for reconsideration of the design and
implementation of process simplification and inherently safer design tech-
niques in the methodology.
Further details on the methodology for process synthesis are discussed in the fol-
lowing sections, while the potential options for simplification are discussed within
the different synthesis layers.

4.1.2
Constraints to Process Synthesis

Constraints play an important part in the synthesis process, and must be recognized
in advance if unnecessary work is to be avoided. Typical constraints include:

. Availability of physical and chemical properties
. Safety
. Environmental
. Decomposition reactions
. Fouling constraints
. Corrosion constraints
. Utility constraints
. Controllability (to be discussed under the controllability layer)
. Patents
. Product specification (most products have more specifications)

4.1.2.1 Physical and chemical property data
These represent a severe constraint for process synthesis studies. In order to achieve
an optimal design, the intention is to evaluate several feasible flowsheets. Although
some physical properties such as vapor±liquid equilibrium can be reasonably well
predicted for most other units, the prediction of such properties is much more diffi-
cult and requires laboratory investigations to be performed. The availability of these
data considerably limits the number of options for evaluation. However, this handi-
cap of the process synthesis is still valuable, not only by identifying these shortcom-
ings but also to increase the number of design options, which can be considerable.

4.1.2.2 Safety
Safety decisions during process synthesis have long-term consequences for the
process and its logistic situation. These decisions must be taken not only for the
reaction section and the main reactants, but also for all other chemicals used in the
process. Raw material, (intermediate) product storage and transportation should
also be included.