Programação da produção para o problema de suprimento de petróleo com a eliminação da discrepância da composição nos tanques e a especificação dos produtos da destilação

Abstract

An optimal oil supply scheduling allows the reduction of the total costs of a refinery through smarter use of cheaper oil, minimizing the exchange of charges in distillation units, and the reduction of demurrage of ships. This present work aims the development of models for schedule of the supply of oil refineries under the following aspects: i) the existence of composition discrepancy between the crude oil mixture in the charging tanks and the mixture in the outlet flow of this units; ii) the development of a mathematical model that is able to eliminate such discrepancies, therefore ensuring the perfect mix condition in the tanks; iii) the properties specification not only in the crude oil mixture, but in the distillation products as well; iv) the utilization of a model based on yields also known as separation model to attend this properties specifications, applied to production campaigns of diesel and naphtha. The objective functions used considered cost minimization and production maximization. First is addressed the discrepancy issue between the generated mixtures; for such the results of two models are compared, an MILP that allows discrepancy between mixtures, and a MINLP that eliminates the discrepancy issue by adding nonconvex constraints in its formulation. Consideration of the discrepancy issue is made by applying this models to four case studies of different complexities, considering time horizons of 8, 10, 12 and 15 hours for different numbers of crude oil, ships and property specifications in the tanks loading and different considerations about mixing of oil in intermediate tanks. In one case is considered the ballast on intermediate tanks. A second MINLP model with discrepancies elimination is developed in this paper, applied to optimization of campaigns to produce diesel and naphtha, considering the minimization of costs and maximization of total output, specifying the sulfur concentration in the product pools rather than in incoming tanks. This model, known as separation model, adopts the concept of yields for calculating the flow of intermediate product streams. This model is applied to four cases: no mixing and blending in intermediate tanks and ballast and no ballast in incoming and intermediate. It is also considered the loading partition between tanks. The results shows the importance of the elimination of composition discrepancy for the problem of oil supply, furthermore it can be seen that the addition of modeling the generation and specification of the distillation products implies in a significant gain in the analysis of the problem . All the models were implemented on GAMS®.