Page 18 - Sustainability in the process industry

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strategic view of Process Integration is outlined; this includes an
overview of the hierarchy of process design, the meaning of
performance targets, and the practical issue of identifying heat
recovery problems from process flowsheets. These three topics are
closely interrelated. Without properly applying the process design
hierarchy, the performance targets cannot find a practical application
and use. However, the process design hierarchy would be difficult to
apply without employing performance targets and estimating upper
bounds on process performance or lower bounds on total cost.
Meaningful and practically useful heat-integrated designs cannot be
obtained without appropriate identification of the heat recovery
problem, a process referred to as data extraction. The chapter
proceeds to describe the use of Composite Curves to set heat recovery
targets, the Problem Table Algorithm for numerical targeting, and
the Heat Recovery Pinch. These tools and concepts form the basis of
Pinch Technology, defining the thermodynamic capabilities of the
heat recovery problems. The more advanced aspects are discussed
next; these include threshold problems, targeting multiple utilities
via the Grand Composite Curve, and establishing targets for heat
transfer area, capital cost, and total cost. There is a short overview of
options for modifying the core process (which defines the heat
recovery problem) that highlights the usefulness of Pinch Technology
and targeting for improving its energy efficiency. The chapter then
focuses on the synthesis of Heat Exchanger Networks; the approach
mainly follows the Pinch Design Method, but there is discussion of
the superstructure-based and hybrid methods used for HEN
synthesis. The next step is Total Site Integration, which provides the
necessary knowledge for energy recovery over complete industrial
complexes and sites.
Chapter 5 deals with an extension of PI known as Mass Integration,
the most widely used instance of which is Water Integration (WI).
The chapter begins with a description of the methodology and bases
for minimizing water use and maximizing water reuse, and the
importance of legislatively imposed constraints is discussed. Best
available techniques are analyzed and recommended for usage, and
the concept of a water footprint is described. At this point, the stage
is set for the main task: minimizing freshwater usage and wastewater
effluents. For this, the methodology of Water Pinch Analysis is
introduced. Also described is a related Mass Integration and
targeting technique, the material recovery Pinch diagram. The
chapter concludes with water minimization using the mathematical
optimization approach. Both the WI and the mathematical
approaches to optimization are illustrated with case studies.
Chapter 6 addresses further PI opportunities that have arisen as
the methodology was developed. These include: Hydrogen Networks
Design and Management; Oxygen Pinch Analysis; combined analyses
(energy-water, oxygen-water, Pinch-emergy, budget-income-time,