Variable neighborhood search with active specification switching repair strategy applied to crude distillation energy integration problem

Document Type

Conference Proceeding

Publication Date

5-29-2012

Abstract

Modern petroleum refining has become an extremely competitive business due to the deteriorating quality of crude oil coupled with tighter product specifications and more stringent environmental regulations. Furthermore, refineries today receive shipments of crude from a variety of sources. These crude oils are of different quality and composition and usually blending can improve the economics of the refinery. Thus, refineries deal with a dynamic schedule of incoming crude, which cause them to frequently change unit's operating conditions to reduce operating expenses including environmental impact. Final products in a petroleum refinery are created by combining feed stocks emerging from distillation units, reformers, and catalytic cracker. The input streams, which have varying chemical compositions and physical properties, are sent into common tanks or pools to be mixed into final products. An MILP model for short-term refinery scheduling is developed using discrete time formulation. The importance of integrating the problems on the different decision making layers by incorporating the CSP with the heat integration of the distillation units is demonstrated. To handle complex optimization models with solution spaces made of ill-defined constraints, a hybrid metaheuristic where variable neighborhood search is aided by a threshold acceptance search is demonstrated. This hybrid operates separately from the model and includes a repair strategy for a non-converging result of a D.V. set. The method is applied to a heat integration problem of a distillation train to have robust optimization under a higher level scheduler and demonstrates competitive improvement and superior handling of non-convergent models when compared to SQP, Fletcher-Reeves, and Newton-Rhapson optimization techniques with no repair strategy. This is an abstract of a paper presented at the 2012 AIChE Spring National Meeting and 8th Global Congress on Process Safety (Houston, TX 4/1-5/2012).

Publication Source (Journal or Book title)

12AIChE - 2012 AIChE Spring Meeting and 8th Global Congress on Process Safety, Conference Proceedings

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