MILP Model for the Tank Farm Operation Problem of Finished Products in Refineries

Abstract

This paper presents a mixed-integer linear programming (MILP) model with a continuous time representation to address the Tank Farm Operation Problem (TFOP) of finished products in refineries. Real scenarios are considered, which were obtained from the planning of refineries and the external pipeline network scheduling, proposed by Ind. Eng. Chem. Res.2010495661. The developed MILP model determines the scheduling of loading and unloading operations in the tank farm of finished products at each refinery, but is subjected to time-window constraints. A decomposition approach has been applied, and multiproduct scenarios proposed by Ind. Eng. Chem. Res.2010495661 were broken in single product scenarios. Each one of these scenarios is related with the tank farm in a specific refinery. Therefore, they are presenting volumes and values of stored inventories, maximum capacity tanks, and start and end times to product movements at the refinery interfaces (production, demand, and pipelines). The proposed MILP model searches a scheduling that minimizes the movements within the refinery tank farm in order to respect the imposed operational and structural constraints. Further, for making feasible the scheduling in a smaller computational time, an iterative algorithm is developed and a new model approach, named MILP-IA, is added within the solution process. The results allow us to analyze the model computational time, the temporal and structural violations, and the number of product movements for each scenario. For the studied cases, we can also check for attending to time and monthly volume constraints for each interface. Finally, the results also indicate that the proposed MILP-IA approach finds solutions in computational times on the order of minutes. The obtained solutions contribute to improve the transfer and storage activities (TS) on two main points: (i) they minimize the number of movements, facilitating the plant operational tasks (searching for routes); and (ii) they provide feedback to the pipeline scheduling, creating a collaborative integration between refinery subsystems, linking all information about internal and external product movements at refineries.

Operation Scheduling Optimization of a Transfer Hub with Multiple Tank Farms Based on a New Continuous Time Representation

“…However, the main difference between the diesel blending and distribution scheduling problem and the TH is that the former should complete the daily demand before the end of the day, whereas the latter not only has to complete the demand but also needs to operate with a given flow rate at all times. Other researchers 20 addressed the scheduling problem of finished product tank farms with domestic production, local markets, and input and output pipeline scheduling. A MILP formulation was proposed with the objective of minimizing the tank capacity violations (factor 1), temporal violations of the operations (factor 2), and number of movements within the tank hub (factor 3).…”

“…This characteristic is similar to the scheduling problem of the M-TH addressed in this paper. However, in the previous study, 20 the capacity violations of the tanks and the temporal violations of the pipeline schedule are considered as two factors of objective functions; however, these violations would lead to infeasible results in reality. The capacity of the tanks and the pipeline schedule should be considered as constraints when the mathematical model is proposed.…”

“…Only a few studies have been conducted − on the scheduling of the third subsystem shipping of refinery, which is similar to the considered problem addressed in this paper. The tank farm receives products from the blending units and delivers them to the local markets.…”