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7.5 The Optimization of an Integrated Complex 259
. Products which are difficult to be separated from other components, but do
not harm the receiving process. Examples include isomers (ethane/ethylene,
propane/propylene, butenes) and benzene from a C 6 mixture of components.
. Consumer plants that achieve a high level of conversion; for example, ethyl
benzene and cumene plants achieve a high conversion of olefins.
. Reactants which are diluted with components in the receiving process and
were separated during up-front processing. Examples include the cumene
process, where propylene is diluted with propane at the reactor inlet; the
same applies to drying of ethylene oxide and butadiene before their use in
respectively the ethylene glycol and latex plants. In the last processes the
reactants are diluted with water at the inlet of the reaction.
. Reactants where additives are supplied for transportation or product stabiliza-
tion and need to be removed in the receiving plant.
The use of lower-grade product streams is a major advantage at an integrated site,
and can create considerable benefits. This, therefore, requires for creative thinking.

7.5.2
Site Utility Integration

Site integration takes place at different levels. The logistic integration and integra-
tion of mass flows by means of specific product grades were discussed above. Site
utility integration in the past has mainly concentrated on energy integration, or
more specifically heat integration. Currently, the integration is broadened to include
mass flow integration.

7.5.2.1 Mass flow integration
The area of energy integration has been broadened during the last decade to water
integration and hydrogen integration, and can be extended further to (generically
speaking) mass flow integration. The pinch analysis technique evolved from heat
integration representation with the temperature against heat duty in (grand) compo-
site curves. As the quality parameter for heat, temperature was selected, while tar-
gets for minimum heat consumption could be easily determined (see Chapter 4).
The extended pinch analysis techniques for integration of mass streams as water
and hydrogen are based on representation of purity against mass flow, where purity
or a specific contaminant is the quality parameter. The disadvantage is that multiple
contaminants are difficult to handle during design. The analysis is similar to that of
the heat integration technique. The target values can be determined and also
upgrading steps (purification of streams) are comparable with heat pumps which
are positioned across pinch points (Wang and Smith, 1994; Doyle and Smith, 1997;
Serriere et al., 1994). The interest in mass transfer integration is growing. For water,
it was the cost related to its scarcity, but also the cost of waste water treatment that
were the drivers. For hydrogen, it was the scarcity which led to the need to design
for minimum usage and upgrading of lower-purity streams, particularly refineries
which have a growing shortage on hydrogen. The utilization of mass integration