Strategies for global optimization of MINLPs

19 dezembro 2019, 09:30 • Pedro Castro

Two-stage MILP/NLP decomposition algorithms for MIQCPs. Spatial brand-and-bound for general problems.

Alternative formulations to a problems.Multiperiod blending of refined petroleum products (MINLP formulation). Solving one such problem in GAMS.

Design of wastewater treatment networks

16 dezembro 2019, 09:30 • Pedro Castro

Mixed-integer quadratically constrained problems (MIQCPs) as an important class of mixed-integer nonlinear programming problems (MINLPs). Relaxation techniques for non-convex bilinear terms: (I) McCormick envelopes (LP relaxation); (ii) Piecewise McCormick envelopes (MILP); (iii) Multiparametric Disaggregation (MILP). 

The wastewater treatment network (WTN) design problem. NLP formulation and its three relaxation models (of different strengths). Illustration by solving a WTN problem in GAMS. Comparison of performance to commercial global optimization solver BARON.

Design of water-using networks

12 dezembro 2019, 09:30 • Pedro Castro

Difficulties associated to nonlinear problems. NLP formulation for the design of water using networks featuring non-convex bilinear terms in the mass balances.

Avoiding circular references in networks with recycling. 
Implementing and solving the water-using network design problem for a multicontaminant system in Excel.

Heat Integration (Part 3)

9 dezembro 2019, 09:30 • Pedro Castro

Part 3 deals with the minimisation of the total investment cost of the heat exchanger network. The problem can be formulated as a non-convex NLP that is built from a superstructure that includes all heat-exchanger possibilities between any pair of hot and cold streams.

Implementation of the model in GAMS, followed by its solution for the complete network and the regions above and below the pinch. The results are interesting in the sense that the option with the fewest heat exchangers is not the one leading to the lowest total cost.

Heat Integration (Part 2, class 2)

5 dezembro 2019, 09:30 • Pedro Castro

MILP model to minimize the number of heat exchanger units. Implementation and solution in GAMS for the complete network as well as for the regions above and below the pinch.