Page 37 - Sustainability in the process industry

14 Cha p te r T w o

Programming) methods. Hybrid methods have also been proposed;
these approaches incorporate heuristic rules as well as Mathematical
Programming (MPR). Much as with any decision making, process
synthesis (or design) is an activity for which no past experience can be
ignored, especially when it comes to localized details of the design.
The most popular approach is to create a superstructure for the
network being designed and then choose the best possible solution
network from the superstructure options.

2.4 Pinch Technology and Targeting Heat Recovery:
The Thermodynamic Roots
Furman and Sahinidis (2002) have compiled a comprehensive review
of works tracing the development of the research on HENs in time.
Their study shows that there was only mild interest in heat recovery
and energy efficiency until the early 1970s, by which time just a few
works in the field had appeared. But between the oil crises of 1973–
1974 and 1979 there were significant advances made in HI. Although
capital cost remained important, the major focus was on saving
energy and reducing related costs. It is exactly this focus that
resulted in attention being paid to energy flows and to the energy
quality represented by temperature. The result was the development
of Pinch Technology, which is firmly based on the first and second
laws of thermodynamics (Linnhoff and Flower, 1978).
In this way HEN synthesis—one of the most important and
common tasks of process design—has become the starting point for
the PI revolution in industrial systems design. HENs in industry are
used mainly to save on energy cost. For many years the HEN design
methods relied mostly on heuristics, as necessitated by the large
number of permutations in which the necessary heat exchangers
could be arranged. Masso and Rudd (1969) is a pioneering work that
defines the problem of HEN synthesis; the paper proposes an
evolutionary synthesis procedure that is based on heuristics. An
alternative HEN synthesis method is described in Zhelev et al.
(1985), one that exploits synergies between heuristics and
combinatorics. In this approach, several suboptimal networks are
synthesized, and in most cases they are less integrated (consist of
more than one subnetwork). A complete timeline and thorough
bibliography of HEN design and optimization works is provided in
Furman and Sahinidis (2002). The paper covers many more details,
including the earliest known HEN-related scientific article: Ten
Broeck (1944).
The discovery of the Heat Recovery Pinch concept (Linnhoff
and Flower, 1978) was a critical step in the development of HEN
synthesis. The main idea behind the formulated HEN design
procedure was to obtain—prior to the core design steps—guidelines