Inventory pinch gasoline blend scheduling algorithm combining discrete- and continuous-time models

• MPIP-C inventory-pinch based three-level scheduling algorithm for nonlinear processes.
• Approximate scheduling of coarse time scale decisions via discrete-time model.
• Detailed scheduling via continuous-time model.
• MPIP-C solves linear problems to less than 0.5% optimality gap.
• MPIP-C solves problems 2–3 orders of magnitude faster than prior methods.

This work introduces multi-period inventory pinch-based algorithm to solve continuous-time scheduling models (MPIP-C algorithm), a three level method which combines discrete-time approximate scheduling with continuous-time detailed scheduling and with inventory pinch-based optimization of operating states. When applied to gasoline blending, the top level computes optimal recipes for aggregated blends over periods initially delineated by inventory pinch points. Discrete-time middle level uses fixed blend recipes to compute an approximate schedule, i.e. what, when, and how much to produce; it also allocates swing storage and associated product shipments with specific storage. Continuous-time model at the third level computes when exactly to start/stop an operation (blend, tank transfer, shipment). MPIP-C algorithm solves linear or nonlinear problems 2–3 orders of magnitude faster than full-space models.