The Influence of Some Factors on the Water Electrical Conductivity Variation Rate in the Low-Frequency Contact Sensors of Conductometers

Abstract

The aim of the work is to study ways to improve the accuracy of water and steam condensate electrical conductivity measurements by evaluating the effect the parameters of the medium analyzed have on the time constant of the conductometer low-frequency contact sensors. Conductometers are currently among the most widely used and reliable instruments applied in cycle chemistry monitoring systems. The electrical conductivity of process media at thermal and nuclear power plants is measured predominantly with the use of contact low-frequency sensors of conductometers. In this regard, a study of the influence of individual factors on the accuracy of electrical conductivity measurements is a topical and demanded issue. The article presents the results obtained from a study of the effect the sample temperature, flow rate and ionic composition have on the electrical conductivity variation rate in dosing ammonia used for main condensate and feed water correction treatment. A comparative analysis of the obtained dependences of the electrical conductivity time constant on the studied perturbations as applied to low-frequency conductometers of various manufacturers is performed. The experiment conducting procedure and the technical characteristics of the instruments used for electrical conductivity measurements are given. As a result of the accomplished study, the factors affecting the time constant of low-frequency flow conductometers of various manufacturers have been substantiated by experiment, and the accuracy of the obtained measured electrical conductivity values for various sample parameters has been given. The study of the effect the sample qualitative composition has on the conductometer sensor time constant has shown a high variation rate of electrical conductivity values at an ammonia concentration in the medium analyzed up to 300 µg/dm3 followed by a gradual decrease in the conductivity variation rate in the interval up to 1000 µg/dm3. It is shown that the combined dosing of ammonium ions and bicarbonates leads to an increase in the time constant value in comparison with the case of dosing only an aqueous solution of ammonia. Optimal sample parameters (temperature and flow rate) are recommended to obtain more reliable measurements of the process water electrical conductivity at thermal and nuclear power plants.