Page 159 - Design of Simple and Robust Process Plants

144 Chapter 5 Process Simplification and Intensification Techniques
. Extraction
. Adsorption
. Heat exchange
. Fluid transport
. Piping
. Instruments
The objective of this chapter is to show that simplification/intensification is techni-
cally achievable. This may be illustrated by technically analyzing the process func-
tions. The reasons why simplification is so difficult originates not only from the
history of design and its evolution, but also on how engineers address the problems
encountered.
History has an impact on development engineers, and often forces their thinking
along well-known roads. Some may call this conservatism; others would call it pro-
ven/solid design. As illustration which can be used is the design of a food process
plant which, historically, were built on gravity flow. The raw products were brought
to the top floor and the manufacturing process passed gradually downwards
through the different units at the different floors, the final stages being conducted
at ground floor level for transportation, or in cellars for ultimate storage. A typical
examples of this is a brewery. However, when pumping became accepted as a stand-
ard unit (this was indeed a breakthrough), gravity flow became to be considered only
in very limited cases. Hence, evolution showed an alternative pass which became
trendsetting for the next generation of plants.
Sequential thinking is another barrier, though this is often not realized. It is
determined by the methodology applied during the design process, though engi-
neers are trained in sequential thinking rather than integrated thinking. The devel-
opment of a flowsheet is a sequential activity. Following many years of development
in process units, functional integration of process units has been applied for only a
short time. An exception might be found in energy integration, which was strongly
stimulated by the energy crises of the 1970s and 1980s, though integration of energy
during flowsheet development has been applied only to some limited degree.
Solving problems in an existing situation results in an attitude that restrict peo-
ple's thinking. In existing process plants the operational emphasis is often restricted
to add-on provisions. The attitude of developing ªwhat ifº scenarios, to strengthen
the safety of an operation, is a very useful tool, and most often leads to add-on provi-
sions. Similar questions are raised during design reviews, which often suffer from
the same restrictive thinking.
The effort during design should based more on the prevention and avoidance of
problems, as this invariably results in cheaper solutions. As Kletzonce declared:

What you do not have can't leak.

From the simple and robust point of view, this could be re-phrased as:

What you do not have can't leak and does not cost anything.