Optimal scheduling of tanker lightering operations

Abstract

When tankers are fully loaded with crude oil, they may not be able to enter the shallow channels or refinery ports due to the draft limitation. Under such circumstances, it is necessary to transfer some part of the crude oil from the tanker to lightering vessels in order to make the tanker "lighter". A special case of the general chemical transshipment problem, i.e., the tanker lightering problem, was presented. A scheduling problem faced by a shipping company that provides lightering services to multiple refineries clustered in a region was studied. The utilization of lightering vessels in the demurrage problem was normally higher than that in the time-charter cost problem. Both two alternate linearization methods (M1 and M2) were capable of finding optimal solutions. However, M2 was simpler with fewer constraints and nonzeros. M2 performed better than M1 in most cases. The comparison of model performances between slot-based and event-based formulations showed that slot-based formulation is generally simpler and more effective. This is an abstract of a paper presented at the AIChE Annual Meeting and Fall Showcase (Cincinnati, OH 10/30/2005-11/4/2005).