Date of Award
Master of Applied Science (MASc)
This thesis addresses a reactive (closed-loop) scheduling framework for integrated
scheduling of process operation and maintenance. Ethylene plant furnace scheduling is
chosen as the process example because it is concerned with optimally scheduling the
furnace operations and its periodic maintenance shutdowns. The main reason for
choosing this example is that it addresses a special class of scheduling problems where
the operations and maintenance have strong interactions and so integrated decision
making becomes necessary.
The major goal of this research was to select an appropriate closed-loop
framework and develop a reactive scheduling system. With the rolling horizon approach
being the most suitable method for closed-loop schedule implementation, a Model
Predictive Control (MPC) framework is chosen in this thesis. The presence of integer
variables in the scheduling model made the reactive scheduling systems resemble a
hybrid MPC problem.
The research was performed in two phases. In the first phase, an open-loop
scheduling model was formulated as a Mixed Integer Linear programming problem
(MILP) using discrete time representation. To ensure the tractability of the model,
tailored formulation methods (disjunctive reactor modelling, constraint reformulation and tightening constraints) and efficient solution heuristics (two-stage temporal
decomposition heuristic) were developed in this thesis. In the second phase, the openloop scheduling model was applied in the prototype closed-loop framework to develop a reactive scheduling system to assist engineers make appropriate decisions in a timely manner.
The automated scheduling system developed in this thesis was tested for several
scenarios and proved to have significant benefits over manual scheduling procedures,
confirmed that the scheduling model is tractable and achieved feasible solutions for all
the scenarios considered, including large problems with multiple feeds, multiple reactors and a long (90-day) scheduling horizon. We conclude that the technology is appropriate for further improvement and eventual application in the industry.
Pula, Ravi, "A FRAMEWORK FOR INTEGRATED REACTIVE SCHEDULING OF PLANT OPERATIONS AND MAINTENANCE" (2009). Open Access Dissertations and Theses. Paper 4078.
McMaster University Library