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Optimization of Dynamic Systems

Dynamic optimization is a key thread that runs through much of our work. It involves solution of an optimization problem that includes a differential or differential-algebraic equation system as constraints. Applications that we consider include optimization of plant operation in response to demand and electricity price fluctuations, optimization of industrial batch process operations, and optimal response under plant failure conditions, examples of which are given below.

  • Optimization of Air Separation Unit (ASU) Operation
    Cryogenic air separation plants separate air into oxygen, nitrogen and argon products by distillation. They are huge consumers of electricity, primarily due to the compression required to liquify the air feed, and would consequently benefit from demand response operation, where the production levels are adjusted in accordance with electricity price fluctuations. MACC researchers have been involved in the development of first-principles dynamic models for air separation plants, as well as their use within optimization formulations to determine optimal operating policies in response to demand and electricity price fluctuations, and to identify design limitations to plant agility. We are also determining optimal start-up operation of ASUs that takes into account discontinuous plant behaviour due to, for example, sequential filling up of distillation column trays.

  • Steel Process Optimization
    Electric arc furnaces (EAFs) are widely used in the steel industry for melting scrap. The highly energy intensive nature of these operations, coupled with their complexity, make them prime candidates for optimization. Our group developed a first-principles based dynamic model of the EAF which was calibrated to an industrial operation by estimating model parameters using plant data. Optimization of input trajectories for a number of constraint and objective function scenarios demonstrated significant potential savings. A current related study involves modeling and optimization of basic oxygen furnaces (BOFs); they are used to adjust the chemistry and temperature of steel from a blast furnace to appropriate levels for casting. The goal is to develop an optimization-based decision support system for BOF operation in order to minimize the operational cost (for example through reducing the total oxygen utilization) through adjustment of operating parameters such as lance height and oxygen flow rate over the duration of the batch.

  • Optimal Response under Partial Plant Shutdown
    Shutdowns in chemical processing plants are detrimental both to plant economics and critical product characteristics. These situations can be due to routine maintenance, or due to the more extreme case of equipment failure. We have developed a formulation and computational strategy for determining optimal operating policies in the face of shutdowns in multi-unit operations, with application to a Kraft pulp mill. Extensions have included the optimal design of additional storage tank capacities in accordance with probability distributions of failure type and duration; and consideration of model uncertainty via multi-scenario optimization. Related work under way involves the development of a multiperiod refinery planning optimization formulation to mitigate the detrimental economic impact of refinery unit shutdowns.

Dr. Chris L. E. Swartz
Professor and Director, MACC
Daniela Dering
Ph.D. Candidate
Ian Gough
Ph.D. Candidate
Anthony Quarshie
Ph.D. Candidate
Dr. Pranav Bhaswanth Madabhushi
ORF-RE Project Officer
Dynamic Optimization of Basic Oxygen Furnace (BOF) Operation)
Dering, D.Swartz, C. L. E., Neslihan, Dogan
AIST, 420-426 (2019)  -  [ Publisher Version ]
Design for dynamic operation-A review and new perspectives for an increasingly dynamic plant operating environment
Swartz, C. L. E., Kawajiri, Y
Computers & Chemical Engineering, 128 329-339 (2019)  -  [ Publisher Version ]
Design for dynamic operation–A review and new perspectives for a dynamic manufacturing environment
Swartz, C. L. E., Kawajiri, Y
Computer Aided Chemical Engineering, 44 571-576 (2018)  -  [ Publisher Version ]
Preemptive Dynamic Operation of Cryogenic Air Separation Units
Cao, Y., Flores-Cerrillo, J, Swartz, C. L. E.
AIChE J (2017)  -  [ Publisher Version ]
Practical optimization for cost reduction of a liquefier in an industrial air separation plant
Cao, Y., Flores-Cerrillo, J, Swartz, C. L. E.
Computers & Chemical Engineering, 99 13-20 (2017)  -  [ Publisher Version ]
Optimization-based Online Decision Support Tool for Electric Arc Furnace Operation.
IFAC-PapersOnLine , 50 (1) 10784–10789 (2017)  -  [ Publisher Version ]
Dynamic Modeling and Collocation-Based Model Reduction of Cryogenic Air Separation Units
Cao, Y.Swartz, C. L. E., Flores-Cerrillo, J, Ma, J
AIChE J, 62 (5) 1602-1615 (2016)  -  [ Publisher Version ]
Optimal response under partial plant shutdown with discontinuous dynamic models
Computers & Chemical Engineering, 86 120-135 (2016)  -  [ Publisher Version ]
Optimal Dynamic Operation of a High-Purity Air Separation Plant under Varying Market Conditions
Cao, Y.Swartz, C. L. E., Flores-Cerrillo, J
Ind Eng Chem Res, 55 (37) 9956-9970 (2016)  -  [ Publisher Version ]
Optimal operation of process plants under partial shutdown conditions
AIChE Journal, 59 (11) 4151-4168 (2013)  -  [ Publisher Version ]