This paper presents a new approach of superstructure mathematical programming combined with total site pinch analysis for utilities and multi-processes optimal synthesis.For the heat integration retrofit

the total site pinch analysis can give the targets of utilities usage and heat recovery

but cannot offer practical designs of optimal network.Based on the total site pinch analysis

a superstructure of utilities heat exchanger network retrofitting can be built which involves only the feasible and better retrofit options.Then an improved Mixed Integer Nonlinear Programming(MINLP)model for the network superstructure is proposed which contains non- convex non-linear objective and constraints.It can be solved with the improved mixed continuous evolutionary algorithm.The presentation has advantages of making use of the results of total site pinch analysis

reducing the scale of superstructure

and having the capability of reaching global optimum.A numerical example of energy integration retrofit in a 300000 t·a -1 ethylene plant illustrates that the combined method can reach the total site pinch analysis targets(of minimum utilities usage and maximum steam generation)and can reach global optimum of utilities heat exchanger network.