Page 35 - Sustainability in the process industry

12 Cha p te r T w o

Reducing the consumption of resources is typically achieved by
increasing internal recycling and reuse of energy and material
streams instead of fresh resources and utilities. Projects for improving
process resource efficiencies can offer economic benefits and also
improve public perceptions of the company undertaking them.
However, motivating, launching, and carrying out such projects
requires proper optimization studies that are based on adequate
models of the process plants.

2.2 What Is Process Integration?

Process Integration (PI) is a family of methodologies for combining
several processes to reduce consumption of resources and/or to
reduce harmful emissions. It started as mainly Heat Integration (HI),
stimulated by the energy crisis of the 1970s (Hohmann, 1971; Linnhoff
and Flower, 1978; Linnhoff, Mason, and Wardle, 1979; Linnhoff et al.,
1982; Linnhoff and Hindmarsh, 1983; Linnhoff and Vredeveld, 1984).
This energy-saving methodology has been used extensively in the
processing and power generating industry over the last 30 years.
Heat Inetegration examines the potential for improving and
optimizing the heat exchange between heat sources and heat sinks in
order to reduce the amount of external heating and cooling required,
thereby reducing costs and emissions. A systematic, rule-based
design procedure has been developed that yields the maximum
energy-saving design for a given system.
There are several definitions of HI (using Pinch Technology);
most refer to the thermal combination of steady-state process streams
or batch operations for achieving heat recovery via heat exchange.
More broadly, the definition of PI, as adopted by the International
Energy Agency (Gundersen, 2000) is as follows: systematic and
general methods for designing integrated production systems
ranging from individual processes to total sites and with special
emphasis on the efficient use of energy and reducing environmental
effects.

2.3 History and Development of Process Integration
It is remarkable that PI continues to interest researchers even 35 years
after its emergence. The HI, which developed as the first part of PI,
deals with the integration of heat in Heat Exchanger Networks (HENs).
This methodology has been shown to have considerable application
potential for complete chemical processing sites, reducing overall
energy demand and emissions across the site and thus leading to a
more effective and efficient site utility system. The PI and its subset HI
method have also been successfully applied to the cogeneration of
heat and shaft power. Further details are available elsewhere