Refinery scheduling of crude oil unloading with tank inventory management

The aim of this study is to develop a methodology for short-term crude oil unloading, tank inventory management, and crude distillation unit (CDU) charging schedule using mixed integer linear programming (MILP) optimization model as an extension to a previous work reported by Lee et al. (1996). The authors attempt to improve the previous model by adding an interval-interval variation constraint to avoid CDU charging rate fluctuation, a shutdown penalty within the scheduling cycle and a set up penalty for tank-tank transfer and introducing demand violation permit for a more flexible model against obtaining infeasible solution. Three different cases from the original paper were used to test the validity of the improved model. Comparison between Cases 1 and 2 shows the advantage of using smaller time interval as the operating cost of Case 2 is lower. Two scenarios were created from Case 3 to show the benefits of the improved model in deciding the best schedule to use. The improved model was implemented using the CPLEX solver in GAMS.