Pipelines have been proved to be an efficient and economic way to transport oil products. However, the determination of the scheduling of operational activities in pipeline networks is a difficult task, and efficient methods to solve such complex problem are required. In this contribution, a real-world pipeline network is studied, and an optimization model is proposed in order to address the network scheduling activities. A hierarchical approach is proposed on the basis of the integration of a mixed integer linear programming (MILP) model and a set of heuristic modules. This article exploits the MILP model, the main goal of which is to determine the exact time instants that products should be pumped into the pipelines and received in the operational areas. These time instants must satisfy the pipeline network management and operational constraints for a predefined planning period. Such operational constraints include pipeline stoppages, movement of batches through many areas/pipelines, use of preferential routes to avoid contamination losses, on-peak demand hours of pumping, local constraints, reversions of flow direction, and surge tank operations, while satisfying a series of production/consumption requirements. The developed continuous-time model is applied to a large real-world pipeline system, where more than 14 oil derivatives and ethanol are transported and distributed between supply and demand nodes.

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ResumoNa programação de operações de movimentação de petróleo em complexos portuários contendo navios, píeres, tanques e oleodutos, um modelo de otimização das operações é frequentemente utilizado. Entretanto, devido à complexidade do problema, o tempo computacional é um fator limitante. Neste artigo, estuda-se a aplicação de um modelo de programação linear inteira mista (PLIM) existente na literatura e propõe-se uma etapa de pré-processamento, baseada na teoria das restrições (TOC), com o objetivo de reduzir o tempo computacional. A partir da identificação do gargalo do problema, determinadas restrições são retiradas do modelo numa etapa de pré-processamento. Para verificar a escolha das restrições críticas no pré-processamento, uma análise baseada na noção de preço dual do LP é apresentada. Embora a otimalidade da solução não seja garantida, os resultados mostram uma pequena deterioração da solução em relação à ótima. Porém, com o tempo computacional significativamente reduzido.Palavras-chave: programação linear inteira mista; pré-processamento; teoria das restrições; indústria do petróleo. AbstractIn the scheduling of oil transfer operations for harbor plants containing ships, piers, tanks and pipelines, an optimization model is frequently used. However, due to the complexity involved, computational time is a real concern. In this paper, a mixed integer linear programming model (MILP) found in the literature is studied and a preprocessing procedure is proposed. This procedure is based on the Theory of Constraints (TOC), which is used to reduce the model compilation time. Since the problem bottleneck is identified, the corresponding constraints are not considered in the preprocessing step. An analysis based on LP dual price is also carried out to verify actions taken in the preprocessing step. Although optimality cannot be assured, the results obtained show a minor deviation from the optimal solution but with a significant computational time gain.

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