Modeling, observer design, control, and optimization of strip annealing furnaces

Project focus

  • Mathematical modeling of a strip annealing furnace
  • Observer design for unknown process variables
  • Development of a control strategy for accurate heating of the strip

Description

In the steel industry, continuous strip annealing furnaces are used for the heat treatment of strip products. To ensure a continuous operation of the furnace, the strips are welded together to form an endless strip. The heat treatment requires a large amount of energy, is cost-intensive, and has a direct impact on the product quality.

Combined direct- and indirect-fired furnace.

To meet the high demands on the quality of the final product, the strip has to be heated to a predefined target temperature while it moves through the furnace. Since an annealing furnace is a complex thermodynamic system with multiple inputs, multiple outputs and diverse interdependencies, strip temperature control is a challenging task. This task is further complicated by a small number of available measurements, restrictions on the inputs and the process quantities, an increasing diversification of the product portfolio as well as increasing demands in terms of product quality and throughput.

Burners and strip in the direct-fired strip annealing furnace.

Burners and strip in the direct-fired strip annealing furnace, © voestalpine AG.

In this project, an optimization-based control concept for the strip temperature of a combined direct- and indirect-fired annealing furnace was developed and implemented at a pilot plant of voestalpine Stahl Gmbh in Linz, Austria. The nonlinear model predictive controller selects optimal values for both the fuel supply and the strip velocity so that the strip temperature follows its desired trajectory. In addition, the controller maximizes the product throughput and minimizes the energy consumption.

Continuous strip annealing furnace.

Continuous strip annealing furnace, © voestalpine AG.

The basis of the controller for the strip temperature is a mathematical model of the considered annealing furnace. Mol, mass, and enthalpy balances, constitutive equations, and numerical discretization methods were used to formulate this model. An ad-hoc state estimator is used to estimate process quantities and material parameters, e.g., the strip emissivity, which cannot be directly measured.

Selected publications

  • S. Strommer, C. Froehlich, M. Niederer, A. Steinboeck, and A. Kugi, Modeling and Control of the Oxygen Concentration in a Post Combustion Chamber of a Gas-Fired Furnace, in Proceedings of the 20th IFAC World Congress, Toulouse, France, 2017, p. 13766–13771.
    [BibTex]
    @InProceedings{Strommer17a,
    author = {Strommer, S. and Froehlich, C. and Niederer, M. and Steinboeck, A. and Kugi, A.},
    title = {Modeling and Control of the Oxygen Concentration in a Post Combustion Chamber of a Gas-Fired Furnace},
    booktitle = {Proceedings of the 20th IFAC World Congress},
    year = {2017},
    volume = {50},
    number = {1},
    month = {7},
    pages = {13766--13771},
    doi = {10.1016/j.ifacol.2017.08.1651},
    address = {Toulouse, France},
    issn = {2405-8963},
    }
  • C. Fröhlich, S. Strommer, A. Steinboeck, M. Niederer, and A. Kugi, Modeling of the Media-Supply of Gas Burners of an Industrial Furnace, IEEE Transactions on Industry Applications, vol. 52, iss. 3, pp. 2664-2672, 2016.
    [BibTex] [Download]
    @Article{Froehlich16,
    Title = {Modeling of the Media-Supply of Gas Burners of an Industrial Furnace},
    Author = {Fr{\"o}hlich, Christoph and Strommer, S. and Steinboeck, A. and Niederer, M. and Kugi, A.},
    Journal = {IEEE Transactions on Industry Applications},
    Pages = {2664-2672},
    Volume = {52},
    Year = {2016},
    Number = {3},
    Doi = {10.1109/TIA.2016.2521738},
    ISSN = {0093-9994},
    Publisher = {IEEE},
    }
  • F. Maislinger, M. Niederer, A. Steinboeck, S. Strommer, and A. Kugi, A Mathematical Model of a Horizontal Direct-Fired Strip Annealing Furnace, in Proceedings of the 17th IFAC Symposium on Control, Optimization and Automation in Mining, Mineral and Metal Processing (MMM), Vienna, Austria, 2016, p. 202–207.
    [BibTex]
    @InProceedings{Maislinger16,
    author = {Maislinger, F. and Niederer, M. and Steinboeck, A. and Strommer, S. and Kugi, A.},
    title = {A Mathematical Model of a Horizontal Direct-Fired Strip Annealing Furnace},
    booktitle = {Proceedings of the 17th IFAC Symposium on Control, Optimization and Automation in Mining, Mineral and Metal Processing (MMM)},
    year = {2016},
    volume = {49},
    number = {20},
    month = {8},
    pages = {202--207},
    doi = {10.1016/j.ifacol.2016.10.121},
    address = {Vienna, Austria},
    issn = {2405-8963},
    }
  • M. Niederer, S. Strommer, A. Steinboeck, and A. Kugi, Nonlinear model predictive control of the strip temperature in an annealing furnace, Journal of Process Control, vol. 48, p. 1–13, 2016.
    [BibTex] [Download]
    @Article{Niederer16,
    Title = {Nonlinear model predictive control of the strip temperature in an annealing furnace},
    Author = {Niederer, M. and Strommer, S. and Steinboeck, A. and Kugi, A.},
    Journal = {Journal of Process Control},
    Pages = {1--13},
    Volume = {48},
    Year = {2016},
    Doi = {10.1016/j.jprocont.2016.09.012},
    ISSN = {0959-1524},
    }
  • S. Strommer, M. Niederer, A. Steinboeck, L. Jadachowski, and A. Kugi, Nonlinear observer for temperatures and emissivities in a strip annealing furnace, in Proceedings of the IEEE Industry Applications Society Annual Meeting, Portland, USA, 2016, p. 1–8.
    [BibTex]
    @InProceedings{Strommer16a,
    author = {Strommer, S. and Niederer, M. and Steinboeck, A. and Jadachowski, L. and Kugi, A.},
    booktitle = {Proceedings of the IEEE Industry Applications Society Annual Meeting},
    title = {Nonlinear observer for temperatures and emissivities in a strip annealing furnace},
    doi = {10.1109/IAS.2016.7731914},
    isbn = {978-1-4799-8397-1},
    pages = {1--8},
    address = {Portland, USA},
    month = {10},
    year = {2016},
    }
  • S. Strommer, M. Niederer, A. Steinboeck, and A. Kugi, Combustion Processes Inside a Direct-Fired Continuous Strip Annealing Furnace, in Proceedings of the 17th IFAC Symposium on Control, Optimization and Automation in Mining, Mineral and Metal Processing (MMM), Vienna, Austria, 2016, p. 208–213.
    [BibTex]
    @InProceedings{Strommer16,
    author = {Strommer, S. and Niederer, M. and Steinboeck, A. and Kugi, A.},
    title = {Combustion Processes Inside a Direct-Fired Continuous Strip Annealing Furnace},
    booktitle = {Proceedings of the 17th IFAC Symposium on Control, Optimization and Automation in Mining, Mineral and Metal Processing (MMM)},
    year = {2016},
    volume = {49},
    number = {20},
    month = {8},
    pages = {208--213},
    doi = {10.1016/j.ifacol.2016.10.122},
    address = {Vienna, Austria},
    issn = {2405-8963},
    }
  • M. Niederer, S. Strommer, A. Steinboeck, and A. Kugi, A simple control-oriented model of an indirect-fired strip annealing furnace, International Journal of Heat and Mass Transfer, vol. 78, p. 557–570, 2014.
    [BibTex] [Download]
    @Article{Niederer14,
    Title = {A simple control-oriented model of an indirect-fired strip annealing furnace},
    Author = {Niederer, M. and Strommer, S. and Steinboeck, A. and Kugi, A.},
    Journal = {International Journal of Heat and Mass Transfer},
    Pages = {557--570},
    Volume = {78},
    Year = {2014},
    Doi = {10.1016/j.ijheatmasstransfer.2014.06.080},
    }
  • S. Strommer, M. Niederer, A. Steinboeck, and A. Kugi, A mathematical model of a direct-fired continuous strip annealing furnace, International Journal of Heat and Mass Transfer, vol. 69, p. 375–389, 2014.
    [BibTex] [Download]
    @Article{Strommer14,
    Title = {{A mathematical model of a direct-fired continuous strip annealing furnace}},
    Author = {S. Strommer and M. Niederer and A. Steinboeck and A. Kugi},
    Journal = {International Journal of Heat and Mass Transfer},
    Pages = {375--389},
    Volume = {69},
    Year = {2014},
    Doi = {10.1016/j.ijheatmasstransfer.2013.10.001},
    }

Applications

  • Industrial furnaces
  • Continuous production systems