Simultaneous Production and Maintenance Scheduling for Refinery Front-End Process with Considerations of Risk Management and Resource Availability

Effective unit maintenance is critically important for the front-end crude transfer process (FCTP) to ensure production reliability and safe operations in refineries. It should be prioritized based on risk ratings of all maintenance tasks and constrained by the availability of various maintenance resources, such as budget, manpower, equipment, and supplies, as well as having minimal impact on the normal production of refineries. In this paper, a new methodology for the simultaneous production and maintenance scheduling for refinery FCTP systems has been developed. It can generate optimal schedules for both crude movement and unit maintenance plans with considerations of dynamic risk management and resource availability constraints. As such, a new multiobjective and mixed-integer nonlinear programming (M-MINLP) model has been developed to minimize the total FCTP operating cost, as well as to minimize the total risk from all maintenance tasks. The scheduling model can handle multiunit maintenance assignments with optimal determination of when to isolate a unit to perform its maintenance and how to resume its service after maintenance under the satisfaction of all strict constraints for crude storage, blending and movements, unit maintenance requirements, and resource limitations. The efficacy of the development has been demonstrated by multiple large-scale case studies.