(570n) Oil Scheduling Incluing Smoothening Transitions in Distillation Units

Oil blending is part of the normal scheduling operations in oil refineries. Mix of different petroleum types are prepared in charging tanks to meet a variety of quality specifications normally imposed by required production profiles and/or equipment design and defined on the planning level. Changing from one mix to another results in changeover costs because distillation units have to dynamically go from one operating condition to a new one. Oil companies may adopt the strategy of simultaneously feeding a distillation unit with the tank leaving the feeding operation and the tank taking over for a short period of time with the purpose of smoothening transition. The temporary simultaneous feeding operation has not been addressed in past literature. Most of the works reported in the literature disregard changeover times. This work conducts a study of the effects of incorporating such a smoothening transition step as part of the decisions involved in the scheduling of oil supply. The MOS (Multi-Operation Sequencing) model proposed by Mouret et al. [Comp & Chem Eng, 35, 1038 (2011)], was taken as the starting development point since it is considered one of the state-of-the-art models for oil scheduling. A real-world case has been used as a testing problem. Results show that the produced scheduling can be quite different from that in which transition is considered abrupt.