Supervised Machine Learning for Understanding and Improving the Computational Performance of Chemical Production Scheduling MIP Models

We adopt a supervised learning approach to predict runtimes of batch production scheduling mixed-integer programming (MIP) models with the aim of understanding what instance features make a model computationally expensive. We introduce novel features to characterize instance difficulty according to problem type. The developed machine learning models trained on runtime data obtained from a wide variety of instances show good predictive performances. Then, we discuss informative features and their effects on computational performance. Finally, based on the derived insights, we propose solution methods for improving the computational performance of batch scheduling MIP models

Supervised Machine Learning for Understanding and Improving the Computational Performance of Chemical Production Scheduling MIP Models

We adopt a supervised learning approach to predict runtimes of batch production scheduling mixed-integer programming (MIP) models with the aim of understanding what instance features make a model computationally expensive. We introduce novel features to characterize instance difficulty according to problem type. The developed machine learning models trained on runtime data obtained from a wide variety of instances show good predictive performances. Then, we discuss informative features and their effects on computational performance. Finally, based on the derived insights, we propose solution methods for improving the computational performance of batch scheduling MIP models

Supervised Machine Learning for Understanding and Improving the Computational Performance of Chemical Production Scheduling MIP Models

We adopt a supervised learning approach to predict runtimes of batch production scheduling mixed-integer programming (MIP) models with the aim of understanding what instance features make a model computationally expensive. We introduce novel features to characterize instance difficulty according to problem type. The developed machine learning models trained on runtime data obtained from a wide variety of instances show good predictive performances. Then, we discuss informative features and their effects on computational performance. Finally, based on the derived insights, we propose solution methods for improving the computational performance of batch scheduling MIP models

Supervised Machine Learning for Understanding and Improving the Computational Performance of Chemical Production Scheduling MIP Models

We adopt a supervised learning approach to predict runtimes of batch production scheduling mixed-integer programming (MIP) models with the aim of understanding what instance features make a model computationally expensive. We introduce novel features to characterize instance difficulty according to problem type. The developed machine learning models trained on runtime data obtained from a wide variety of instances show good predictive performances. Then, we discuss informative features and their effects on computational performance. Finally, based on the derived insights, we propose solution methods for improving the computational performance of batch scheduling MIP models

Supervised Machine Learning for Understanding and Improving the Computational Performance of Chemical Production Scheduling MIP Models

We adopt a supervised learning approach to predict runtimes of batch production scheduling mixed-integer programming (MIP) models with the aim of understanding what instance features make a model computationally expensive. We introduce novel features to characterize instance difficulty according to problem type. The developed machine learning models trained on runtime data obtained from a wide variety of instances show good predictive performances. Then, we discuss informative features and their effects on computational performance. Finally, based on the derived insights, we propose solution methods for improving the computational performance of batch scheduling MIP models

Mixed-Integer Programming Model and Tightening Methods for Scheduling in General Chemical Production Environments

We develop a mixed-integer programming (MIP) model to address chemical production scheduling problems in a wide range of facilities, including facilities with many different types of material handling restrictions and a wide range of process characteristics. We first discuss how material handling restrictions result in different types of production environments and then show how these restrictions can be modeled. We also present extensions for some important processing constraints and briefly discuss how other constraints and characteristics can be modeled. Finally, we present constraint propagation methods for the calculation of parameters that are used to formulate tightening constraints that lead to a substantial reduction of computational requirements. The proposed model is the first to address the generalized chemical production scheduling problem

Reformulations and Branching Methods for Mixed-Integer Programming Chemical Production Scheduling Models

Mixed-integer programs for chemical production scheduling are computationally challenging. One characteristic that makes them hard is that they typically have many symmetric solutions, that is, solutions that are different in terms of the values of the decision variables but have the same objective function value, which means that the algorithms used to solve these models must search through all such solutions before improving the bound on the objective. To address this challenge, we propose three reformulations of the widely used state–task network formulation. Specifically, we introduce additional constraints to define the number of batches of each task as an integer variable. Branching on this new integer variable quickly eliminates schedules that have the same number of batches, which, in turn, leads to the elimination of many symmetric solutions. We also study different branching strategies and variable selection rules and compare them. The proposed solution methods lead to orders-of-magnitude reductions in the computational requirements for the solution of scheduling problems

An Optimization-Based Approach for Simultaneous Chemical Process and Heat Exchanger Network Synthesis

We propose a mixed-integer nonlinear programming (MINLP) model for simultaneous chemical process and heat exchanger network synthesis. The model allows process stream inlet/outlet temperatures and flow rates to vary and can be extended to handle unclassified streams, thereby facilitating integration with a process synthesis model. The proposed model is based on a generalized transshipment approach in which the heat cascade is built upon a “dynamic” temperature grid. Both hot and cold streams can cascade heat so that exchanger inlet and outlet temperature, heat duty, and area can be calculated at each temperature interval. We develop mixed-integer constraints to model the number of heat exchangers in the network. Finally, we present several solution strategies tailored to improve the computation performance of the proposed models

Reformulations of Mixed-Integer Programming Continuous-Time Models for Chemical Production Scheduling

Although several optimization models have been proposed for chemical production scheduling, there is still a need for effective solution methods. Accordingly, the goal of this work is to present different reformulations of representative continuous-time models by introducing an explicit variable for the number of batches of a given task. This idea, which has been successfully applied to discrete-time models, results in significant computational enhancement. We discuss how different objective functions benefit from particular reformulations and show significant improvements by means of an extensive computational study that includes several instances containing different process networks and scheduling horizons

Design of Cellulosic Ethanol Supply Chains with Regional Depots

The conversion of lignocellulosic biomass to fuels has the potential to reduce our dependence on fossil fuels. To ensure biomass supply meets biofuel demand, it is necessary to have an effective biomass supply network. Toward this end, the concept of regional biomass processing depot, where biomass is pretreated and/or densified to a higher density intermediate, has been introduced to improve the performance of supply network in terms of costs and emissions. In this article, we develop a mixed-integer nonlinear programming model for the capacity and inventory planning problem of biofuels supply chain including depots. Importantly, the proposed model accounts for variable locations of depots, which is a subject that has not been studied in the literature. In addition, our models account for biomass selection and allocation, technology selection and capacity planning at depots and biorefineries, and biomass seasonality