A comparative study of continuous-time modelings for scheduling of ...
A comparative study of continuous-time modelings for scheduling of crude oil operations Xuan Chen a , Ignacio Grossmann b , Li Zheng a,∗ a Department of Industrial Engineering, Tsinghua University, Beijing 100084, China b Department of Chemical Engineering, Carnegie Mellon University, Pittsburgh, PA 15213-3890 USA Abstract This work presents a comparative analysis of multiple time-grid representations and formulations for the crude oil scheduling problem. We compare the event-based model, the unit slot model and the multi-operations sequence (MOS) model. Pros and cons of different models are highlighted based on modeling and numerical experiments. We also propose several extensions of the previous models. The MOS model exhibits promising computational performance compared with the other two models, shedding a light on its efficient performance for industrial problems. Keywords: Crude oil scheduling; event-based model; unit slot model; multi-operations sequence model 1. INTRODUCTION The crude oil short-term scheduling problem is the first and critical stage of the crude oil refining process. The problem involves crude oil unloading from marine vessels to storage tanks, transfers and mixings in charging tanks, and a charging schedule for each crude oil mixture to the crude distillation units (CDUs). As there are many varieties of crude in the market, varying widely in properties, processing difficulties and product yields, most refineries procure and process several types of crude, yielding various products and a wide range of profit margins. Optimal crude oil scheduling enables cost reduction by using cheaper types of crude intelligently and minimizing ∗ Corresponding author. Email addresses: email@example.com (Xuan Chen), firstname.lastname@example.org (Ignacio Grossmann), email@example.com (Li Zheng) Preprint submitted to Computers and Chemical Engineering December 1, 2011
Table D.2: Results of the event-bas
Table D.6: Results of the MOS formu
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