This paper presents an approach for the operational optimisation of potable water distribution networks. The maximum of the use of low-cost power (e.g. overnight pumping) and the maintenance of a target chlorine conce...
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This paper presents an approach for the operational optimisation of potable water distribution networks. The maximum of the use of low-cost power (e.g. overnight pumping) and the maintenance of a target chlorine concentration at final delivery points were defined as important optimisation objectives. The first objective is constrained by the maintenance of minimum emergency volumes in all reservoirs, while the second objective would include the minimisation of chlorine dosage and re-dosage requirements. The combination of dynamic elements (e.g. reservoirs) and discrete elements (pumps, valves, routing) makes this a challenging predictive control and constrained optimisation problem, which is being solved by MINLP (mixed integer non-linear programming). Initial experimental results show the performance of this algorithm and its ability to control the water distribution process.
In the present paper an essential problem in the process industry, the trim-loss problem, is considered. The problem can be identified in many different industries (for instance in the paper and metal industry) but he...
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In the present paper an essential problem in the process industry, the trim-loss problem, is considered. The problem can be identified in many different industries (for instance in the paper and metal industry) but here, the main focus is on the paper industry or more precisely, the paper-converting industry. In the trim-loss problem at a paper-converting mill, an optimal strategy is sought for cutting a wide raw-paper reel into narrower, customer-specified product reels in such a way that the appearance of waste, the trim loss, is minimized. Besides being a numerically challenging non-convex mixed integer non-linear programming problem, the choice of objective is of great importance and a non-trivial task in order to alter sustainable and environmentally benign solutions. Therefore, in the following some transformation techniques for overcoming bilinearity and solving the original problem into its global optimality are presented. The transformations are followed by an analysis and comparison of different ways to formulate the objective function. Finally, a set of example problems are solved in order to project the theoretical considerations to more practical level. (C) 1999 Elsevier Science Ltd. All rights reserved.
The growing need to achieve high availability for large integrated chemical process systems demands higher levels of system reliability at the operational stage. In these circumstances, it has become critical to consi...
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The growing need to achieve high availability for large integrated chemical process systems demands higher levels of system reliability at the operational stage. In these circumstances, it has become critical to consider the reliability aspects of a system and its components at the design stage. Traditional reliability/availability analysis methods and maintenance optimization frameworks, commonly applied at the design stage, are limited in their application, as in most of these methods the designer is required to specify the process system components, their connectivity and their reliabilities a priori. As a result, these traditional methods do not provide the flexibility to reconfigure a process or select initial reliabilities of equipment in a way that maximizes the inherent plant availability at the design stage. In this paper, we developed an optimization framework by combining the reliability optimization and process synthesis challenges and the combined optimization problem is posed as a mixed integer non-linear programming optimization problem. The proposed optimization framework features an expected profit objective function, which takes into account the trade-off between initial capital investment and the annual operational costs by supporting appropriate estimation of revenues, investment cost, raw material and utilities cost, and maintenance cost as a function of the system and its component availability. The effectiveness and usefulness of the proposed optimization framework is demonstrated for the synthesis of the hydrodealkylation process (HDA) process. (C) 2002 Elsevier Science Ltd. All rights reserved.
In this paper, a system for parallel solution of large scale disjunctive optimization problems is presented. Disjunctive optimization problems occur in process engineering;both in production scheduling and in process ...
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In this paper, a system for parallel solution of large scale disjunctive optimization problems is presented. Disjunctive optimization problems occur in process engineering;both in production scheduling and in process synthesis. In general these problems are computationally very hard to solve. This system combines the demands of process engineering optimization problems with the potential CPU-power of the computers connected to the Internet. The system is capable of using an arbitrary number of computers connected to the Internet for distributed solution of rigorous industrial optimization problems.
In this paper, a mixedintegernonlinearprogramming (MINLP) algorithm for minimizing pseudo-convex functions under pseudo-convex constraints is proposed and illustrated. The solution procedure is iterative and relie...
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In this paper, a mixedintegernonlinearprogramming (MINLP) algorithm for minimizing pseudo-convex functions under pseudo-convex constraints is proposed and illustrated. The solution procedure is iterative and relies on successive linear approximation of the objective function and on a line-search technique. The whole procedure is then embedded within the framework of a existing cutting plane method for mixedintegernon-linear programs. This enables us to solve general MINLPs with pseudo-convex objective and pseudo-convex inequality constraints to global optimality. (C) 2000 Elsevier Science Ltd. All rights reserved.
In this paper, a novel mixed integer non-linear programming model for single component refrigerant design is presented. At the heart of the approach is a new formulation for structural feasibility that allows multiple...
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In the present paper, convexification strategies for certain kinds of discrete and integernon-convex optimization problems are introduced and discussed. We show how to solve problems with both posynomial and negative...
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In the present paper, convexification strategies for certain kinds of discrete and integernon-convex optimization problems are introduced and discussed. We show how to solve problems with both posynomial and negative binomial terms in the constraints. The convexification technique may in some cases be generalized to include continuous variables. Posynomial functions are non-convex and for such functions no straightforward methods for finding the optimal solution exist. Such functions appear frequently in different kinds of chemical engineering problems. The different transformation techniques are illustrated in the form of short examples. The techniques are finally applied to a large, bilinear, trim loss problem regularly encountered at paper-converting mills. (C) 1999 Elsevier Science Ltd. All rights reserved.
In this paper, a general method for handling disjunctive constraints in a MINLP optimization problem is presented. This method automates the reformulation of an, in a abstract modeling language given, optimization pro...
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In this paper, a general method for handling disjunctive constraints in a MINLP optimization problem is presented. This method automates the reformulation of an, in a abstract modeling language given, optimization problem into a mathematical problem that is solvable with existing optimization tools. This implementation can use common MILP solvers for linear problems and nonlinear methods for quasi-convex optimization problems. It also includes the possibility to use the logics in the system and solve the system logically using subproblems.
Stochastic optimization approaches are achieving growing interest in application to difficult optimization problems common in chemical and process engineering. They are easy to use especially in cases where there are ...
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Stochastic optimization approaches are achieving growing interest in application to difficult optimization problems common in chemical and process engineering. They are easy to use especially in cases where there are disjunctive functions and logical conditions. M-LI optimization algorithm from adaptive random search (ARS) strategy has been developed for most advantageous optimization problems, i.e. MINLP ones. This method is an extension of LJ algorithm developed by Jaakola and Luus (1974) for problems with continuous variables. The main modification in M-LJ method is the change of distribution function for integer variables. The results of tests are presented and the comparison with the performance of other stochastic methods as e.g. MSIMPSA algorithm from Cardoso et al. (1997). M-LJ has shown high robustness and can be seen easy to use optimization tool for certain MINLP problems. Also, the re-formulation of difficult optimization MINLP problem for batch processes from Kocis and Grossmann (1988) has been developed which allows for solving it as NLP task.
Stochastic optimization approaches are achieving growing interest in application to difficult optimization problems common in chemical and process engineering. They are easy to use especially in cases where there are ...
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Stochastic optimization approaches are achieving growing interest in application to difficult optimization problems common in chemical and process engineering. They are easy to use especially in cases where there are disjunctive functions and logical conditions. M-LI optimization algorithm from adaptive random search (ARS) strategy has been developed for most advantageous optimization problems, i.e. MINLP ones. This method is an extension of LJ algorithm developed by Jaakola and Luus (1974) for problems with continuous variables. The main modification in M-LJ method is the change of distribution function for integer variables. The results of tests are presented and the comparison with the performance of other stochastic methods as e.g. MSIMPSA algorithm from Cardoso et al. (1997). M-LJ has shown high robustness and can be seen easy to use optimization tool for certain MINLP problems. Also, the re-formulation of difficult optimization MINLP problem for batch processes from Kocis and Grossmann (1988) has been developed which allows for solving it as NLP task.
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