Page 291 - Sustainability in the Process Industry Integration and Optimization

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reuse design requires a minimum of five new pipes, and the
regeneration reuse design requires seven new pipes. The reuse
analysis predicted a short payback period, but the regeneration
analysis was not definitive for the reasons described previously. In
sum, a Water Pinch Analysis for this citrus plant demonstrated that
the consumption of freshwater could be reduced by as much as 30
percent with low investment and few changes to the existing
plant.

11.4 Efficient Energy Use in Other Food and
Drink Industries
Many studies have employed Pinch Technology (and its associated
Heat Integration Analysis) in the food-processing industry. This
industry has a far different thermodynamic profile than that of the
refining and petrochemical industries. The food-processing industry
is characterized by process streams of relatively low temperature
(normally 120–140°C), a small number of hot streams, low boiling-
point evaporation of food solutions, considerable deposition of scale
in evaporators and heat recovery systems, and seasonal operation.
However, a number of studies have also found that the application
of Pinch Technology and Heat Integration is hampered by particular
aspects of the food-processing systems. These aspects include direct
steam heating, difficulties in cleaning heat exchanger surfaces, and
high utility temperatures. Despite these drawbacks, the benefits that
can be obtained by applying the Pinch Technology (e.g., optimized
heat recovery systems and reduced energy consumption) far outweigh
the difficulties of performing the studies. There are also other
advantages that can be realized by technological improvements:
reduced deposition of scale due to reduced utility temperatures, self-
regulation of heat processes, and reduced emissions.
A case study of the production of refined sunflower oil (Klemeš,
Kimenov, and Nenov, 1998) exemplifies the benefits of process
analysis based on Pinch Technology and Heat Integration. The
process studied operated with a minimal temperature difference of
65°C at the Process Pinch. The external heating required by the
system was provided by two types of hot utilities—Dowtherm steam
and water steam; the required external cooling was provided by two
cold utilities—cooling water and chilled water. The analysis proposed
that heat recovery be increased and that the minimum temperature
difference be reduced to 8–14°C. The increase in heat recovery
(provided by a reduction in the minimum driving force for the
process) entailed an increase in the heat transfer area, but this was
more than offset by reductions in the hot and cold utility requirements.
A further benefit of the analysis was a reduction in the number of
utilities needed: eliminating water steam and cooling water
considerably simplified the overall design.