The front-end crude scheduling (FECS) is very important for the entire supply chain management of refineries. It is used to tackle the crude movement problem covering crude vessel unloading at ports, temporarily storing at storage tanks, multi-oil transferring through long-distance pipelines, crude blending in charging tanks, and continuously feeding to refineries under specifications. Through FECS, an optimal crude movement schedule considering both profitability and operability can be identified. In previous studies, however, such a schedule was normally obtained under the scenario that all process units were under normal and deterministic operating conditions without the consideration of any possible abnormal situations such as the demand of certain unit maintenance. Note that the crude supply process is a highly unit-intensive and interactive process coupling both batch and continuous operations under heavy duties. Thus, the unit depreciation and performance degradation cannot be neglected, and maintenance should be regularly planned and conducted [1,2]. For instance, all equipment needs to be periodically checked, repaired and even replaced; otherwise, equipment failures may results in significant economic loss, and severe safety and environment problems. Some research papers have been published on various uncertainties during normal operations, such as shipping delays, demand change and tank malfunctions [3,4,5], these studies focused on the identification of post remedial measures for some uncertainty scenarios, instead of proactively considering unit maintenance operations in advance. Therefore, there still lack of FECS studies with the consideration of the planning of unit maintenance. In this paper, a novel FECS model combined with the planning of unit maintenance has been developed. It can provide optimal schedules for both front-end crude movement and maintenance operations (starting time and duration) toward the minimal operational cost. The efficacy and performance of the proposed model has been tested and demonstrated through various case studies.
References
[1] Amaran, S., Sahinidis, N., Sharda, B., Morrison, M., Bury, S., Miller, S., & Wassick, J., (2015) Long-term turnaround planning for integrated chemical sites. Computer and Chemical Engineering, 72, 145-158.
[2] Vieira, M., Varela, T., Povoa, A., (2017) Production and maintenance planning optimization in biopharmaceutical processed under performance decay using a continuous-time formulation: A multi-objective approach. Computer and Chemical Engineering, 107, 111-139.
[3] Xu, J., Qu, H., Wang, S., & Xu, Q., (2017) A new proactive scheduling methodology for front-end crude oil and refinery operations under uncertainty of shipping delay. Industrial & Engineering Chemistry Research, 56, 8041-8053.
[4] Li, J., Misener, R., & Floudas, C., (2012) Scheduling of crude oil operations uncer demand uncertainty: A robust optimization framework coupled with global optimization. AIChE Journal, 58, 2373-2396.
[5] Zhang, S., Wang, S., & Xu, Q., (2015) A new reactive scheduling approach for short-term crude oil operations under tank malfunction. Industrial & Engineering Chemistry Research, 54, 12438-12454.
