RETROFIT OF COMPLEX AND ENERGY INTENSIVE PROCESSES .1.

Thermodynamic methods of process synthesis are very useful for the des ign of complex and energy intensive processes, but they cannot be used simultaneously with material balances. Algorithmic methods are simult aneous, but they are difficult to solve for complex and energy intensi ve processes because the number of variables increases with the number of combinations. We can approach the optimal design for complex and e nergy intensive processes if we combine the two methods. The combined approach is composed of two steps, the thermodynamic and the algorithm ic one. In the first one we eliminate unpromising structures and we in clude new, potentially good ones by studying an Extended Grand Composi te Curve. In the second one we can optimize the superstructure obtaine d by using Mixed-Integer Nonlinear Programming. The combined approach can be used for optimal design of energy and material parameters of co ntinuous processes as well as for energy recovery. In a retrofit case study we have targeted energy saving using rigorous models and fixed a mount how rates to find two promising structures, and then we have use d parameter and simultaneous structural optimization to determine the best alternative and its parameters.