A continuous-time formulation for refinery production scheduling problems involving operational transitions in mode switching

For the two main challenges in the discrete-time formulation: discrete approximation of time and large size of mixed-integer linear problem (MILP), an alternative continuous-time refinery scheduling model involving transitions of mode switching is presented. To reduce the difficulty in solving the large scale MILP resulting from the sequencing constraints, the global event-based formulation is chosen. Both transition constraints and production transitions are introduced and the numbers of key variables and constraints in both of the discrete-time and continuous-time formulations are analyzed and compared. Three cases with different lengths of time horizons and different numbers of orders are studied to show the efficiency of the proposed model.159