Page 213 - Sustainability in the Process Industry Integration and Optimization

190 Cha p te r E i g h t

containing both serial and parallel subsystems. They include several
equipment units, each with its own degree of availability and
reliability. Scheduled outages need to be differentiated from the
downtimes caused by unexpected faults. Maintenance actions—
including scheduled outages—should be updated as needed to cope
with changes that occur within the system. The recommendations of
reliability engineers inform the designer’s task of effectively modeling
and optimizing all the specified objectives.
Many things need to be improved in waste management. These
include policy focus and popular opinion, which should both pay
more attention to the importance of this process and its effects.
Landfill space is decreasing while solid waste is increasing, so public
and private landfills compete for municipal clients to ensure the
capital required to extend landfill life while coping with new permits.
The situation varies in different countries and geographic regions, so
investigation is needed to devise appropriate solutions for specific
scenarios.

8.6 Summary

This chapter presented several examples of combined PI and
optimization. The main focus was on exploiting the advantages of
graph-theoretic (P-graph and/or S-graph) frameworks. These
methods are well tested and have demonstrated their efficiency
across many applications.