The doctoral dissertations of the former Helsinki University of Technology (TKK) and Aalto University Schools of Technology (CHEM, ELEC, ENG, SCI) published in electronic format are available in the electronic publications archive of Aalto University - Aaltodoc.
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Measuring, Modelling and Controlling the pH Value and the Dynamic Chemical State
Jean-Peter Ylén
Dissertation for the degree of Doctor of Science in Technology to be presented with due permission of the Department of Automation and Systems Technology for public examination and debate in Council Room at Helsinki University of Technology (Otakaari 1 F, Espoo, Finland) on the 14th of December, 2001, at 12 noon.
Dissertation in PDF format (ISBN 951-22-5783-1) [1753 KB]
Dissertation is also available in print (ISBN 951-22-5782-3)
Abstract
pH value is a challenging quantity to measure, model and control. In fact, pH value is a mere one-dimensional projection of a multi-dimensional quantity called chemical state and measuring, modelling and controlling the chemical state is much more challenging.
This thesis contributes to all aspects of pH processes. A new method for measuring the pH value under difficult conditions (pressure and flow variations in thick pulp) is presented. Classical physico-chemical modelling of chemical systems is extended with a concept of population principle which is a new formulation of the "reaction invariant - reaction variant" structure. Self-organising fuzzy controller (SOC) is modified to suit pH-processes better (high frequency noise and oscillations are damped more efficiently).
All the methods described above were tested with practical applications that include a pilot neutralisation process, an industrial ammonia scrubber and a paper machine wet end. The new methods showed such a significant improvement that they were installed permanently on the industrial applications.
Keywords: self-organising fuzzy control, industrial control, pH modelling, pH measurement, adaptive control, pH control
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© 2001 Helsinki University of Technology
Last update 2011-05-26