Page 103 - Design of Simple and Robust Process Plants

88 Chapter 4 Process Synthesis and Design Optimization
. The second layer to be executed during synthesis step 2 is supportive to:
± selection of the reactor configuration;
± ultimate selection of separation sequence; and
± determination of the preliminary operational conditions and equipment
dimensioning.
The continuous optimizations are based on DFC/NPV calculations with a limited set
of DOFs for the preliminary design of process sections. Modeling is carried out
based on short-cut (reduced) models to achieve rapid solutions, but also to avoid
mixed integer problems as introduced by equilibrium stage-to-stage calculations.
. The third layer is after the final flowsheet has been selected, to determine
the overall equipment dimensions and operational conditions for the process
sections
The continuous optimizations are based on DFC and NPV calculations with a max-
imum set of design and operational DOFs for the final flowsheet.
. The fourth layer of optimization is performed on the overall process. Its pri-
mary purpose is to verify the results of the process section in the overall pro-
cess. The impact of price variations on the design and operation are evaluated
at this stage.

The optimizations are based on DFC and NPV calculations with a reduced set of
DOFs per section, covering major equipment dimensions and all operational DOFs.

4.1.6
Creativity

The most important aspect of process synthesis is creativity, because that is the way
to achieve competitive designs. It is during the simplification / idea generation
where creativity plays a dominating role. Creativity begins with recognizing an
opportunity ± when people recognized the need to wipe the car's windscreen, some-
one invented a screen-wiping mechanism. A similar comment might be made
about the building of an airplane having been derived from an interest to fly. Most
new things or inventions come from a recognized opportunity, or:

Opportunities are the nutrients for creativity.

The opportunity to design simple and robust plants that are competitive, is a chal-
lenge, and in order to achieve this much alternative thinking is required. That does
not necessarily mean that new things will be invented ± often it is simply the right
combination of known elements that clicks into place and leads to a new invention.

Creating new things is more often based the combination of known elements than by
inventing something new