Year 2004
Taina Björkman

Tuning methods of the temperature control of the reactors at a pharmaceutical plant

The aim of this thesis was to model the process of temperature control between the inside temperature of the reactor and control valve controlling the temperature of the jacket surrounding the reactor, and to find a proper method for controller tuning. In addition, the aim was to prepare the instructions for tuning the inside temperature of all the reactors and to make use of the tuning tool of the plant's automation system.

In the literature survey part, different solutions for temperature control and heat transfer in the batch reactors were examined and the process was modeled with energy balances. In addition, three examples of temperature control in the batch reactor were studied more closely.

In the experimental part, the structure of the temperature control and automation of a particular pharmaceutical plant were explained. In addition, the process was modeled with Simulink. The tests were run on five different reactors taking into account many variables. On the basis of the tests the nonlinearity and the integrating character of the response were seen. In addition, the primary loop has a very long time constant, which makes it more difficult to find a tuning method. Tuning parameters for temperature control were estimated and calculated with various methods and finally the most appropriate methods for tuning the secondary and primary loops of the cascade control were chosen.

As a solution for improving control, the tuning parameter schedule based on range of activity and change of the control logic, already prepared at the plant, were presented. With these measures, the control would make the process stable. Also, the valves with more linear character would make the control better. The tuning tool of the automation system was found to be of use in the rough tuning of the secondary loop.

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