Measuring, modelling and controlling the pH value and the dynamic chemical state

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Doctoral thesis (monograph)
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Date

2001-12-14

Department

Department of Automation and Systems Technology
Automaatio- ja systeemitekniikan osasto

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Language

en

Pages

145, [1]

Series

Report / Helsinki University of Technology, Control Engineering Laboratory, 127

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.

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Keywords

self-organising fuzzy control, industrial control, pH modelling, pH measurement, adaptive control, pH control

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https://urn.fi/urn:nbn:fi:tkk-003251

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[diss] Sähkötekniikan korkeakoulu / ELEC