Browsing by Issue Date, starting with "2010-06-06"
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- Parametric programming technique for global optimization of wastewater treatment systemsPublication . Teles, João P.; Castro, Pedro; Matos, Henrique A.This paper presents a parametric programming technique for the optimal design of industrial wastewater treatment networks (WTN) featuring multiple contaminants. Inspired in scientific notation and powers of ten, the proposed approach avoids the non-convex bilinear terms through a piecewise decomposition scheme that combines the generation of artificial flowrate variables with a multi-parameterization of the outlet concentration variables. The general non-linear problem (NLP) formulation is replaced by a mixed-integer linear programming (MILP) model that is able to generate near optimal solutions, fast. The performance of the new approach is compared to that of global optimization solver BARON through the solution a few test cases.
- Effective decomposition algorithm for multistage batch plant schedulingPublication . Castro, Pedro; Harjunkoski, Iiro; Grossmann, Ignacio E.This paper presents a new algorithm for the scheduling of batch plants with a large number of orders and sequence-dependent changeovers. Such problems are either intractable or yield poor solutions with full-space approaches. We use decomposition on the entire set of orders and derive the complete schedule in several iterations. The key idea is to allow for partial rescheduling without altering the main decisions in terms of unit assignments and sequencing, so that the complexity is kept at a manageable level. It has been implemented with a unit-specific continuous-time model and tested for different decomposition settings. The results show that a real-life 50-order, 17-unit, 6-stage problem can effectively be solved in roughly 6 minutes of computational time.
- Assessing performance and degradation in PEM Fuel Cells by electrochemical impedancePublication . Rangel, C. M.; Silva, R. A.; Paiva Luís, Teresa
- Rolling-horizon algorithm for scheduling under time-dependent utility pricing and availabilityPublication . Castro, Pedro; Harjunkoski, Iiro; Grossmann, Ignacio E.This work addresses the scheduling of continuous single-stage multiproduct plants with energy intensive processing tasks and time-dependent electricity cost and power supply. A new rolling horizon algorithm is proposed that consists of a planning model to predict the production levels and a continuous-time model for detailed scheduling. The results from a set of test problems from the literature show that the algorithm can generate global optimal solutions much more rapidly than standalone discrete or continuous-time formulations in problems involving unlimited power availability.