Evaluation of models for the steam supply system to improve control of the paper dryer

The possibility of reducing the transient times at grade changes in paper production and machine start-ups on the paper machines has highlighted the need for increased knowledge of the steam supply system. Models in this area have been presented in previous work and it is of interest to compare these models with each other and evaluate them against experimental data. This paper reports on the results obtained from measurements on an industrial paper dryer. Step responses as well as the dynamic changes caused by new set points for the control system are examined. The two models are derived from different disciplines and comparison between these will be presented. The first model will provide estimations of the heat transfer coefficients in the condensate layer as well as the coefficient between the cylinder and the paper. This model is based on physical properties and first principles. The second model is a linear process model, written in the Laplace operator as a transfer function. This model is based on input-output data, a black box model, where the input and the output are the experimental data from the paper machine.