Refinery short-term scheduling using continuous time formulation: Crude-oil operations

This paper addresses the problem of crude-oil short-term scheduling, which is the first part of the overall refining operations. The problem involves the optimal operation of crude-oil unloading from vessels, its transfer to storage tanks, and the charging schedule for each crude-oil mixture to the distillation units. A novel model is developed based on a continuous-time representation and results in a mixed-integer linear programming (MILP) problem. The state-task network representation is used throughout this paper. The proposed formulation is applied to several case studies and leads to fewer binary and continuous variables and fewer constraints compared with existing discrete-time models. Thus, an efficient solution can be achieved using available MILP solvers.