I usually play with Aspen and HYSIS to optimize process but in my opinion the design for process optimization has to be included on a global cycle called the process optimization cycle. You could read some information about the continuous process improvement by clicking the link below.
http://www.pmi.co.uk/
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Kumar Prashant , Petrochemical & Refining Technical Assistant , Process Integration Limited
Aspen plus, HYSYS, UNISIM can be use to used to optimize process. Heat-int can be used for optimizing heat exchanger network, Site-int can be used for optimizing utility systems.
