Research on pH control strategy for internal cooling water in generators with dissolved CO2

Abstract

The core of generator internal cooling water treatment is to control the pH of the internal cooling water within the range of 8.0-9.0, to realize the control of copper wires corrosion through a slightly alkaline environment. It is quite important to monitor the pH of the internal cooling water in generators. However, due to the low conductivity of the internal cooling water and the influence of factors such as liquid contact potential, flow potential, and pure water temperature compensation, it is difficult to accurately determine its pH using traditional pH electrodes, and it is very easy to dissolve CO2 in the internal cooling water. Therefore, conventional computational pH instruments are not suitable. A mathematical model was established for the relationship between pH, electrical conductivity, and hydrogen conductivity in internal cooling water of generator with dissolved CO2 and NH3 as alkalization agent, based on Kohlrausch’s law of ion independent movement. The accuracy of the model was verified through dynamic simulation experiments. The maximum error of pH calculated using the model was 0.03, indicating the high accuracy of the model. This model was applied to guide the on-site NH3 dosing in on-site industrial experiments. Compared with using traditional pH electrodes to control the dosage of alkalizing agents, the copper concentration in the internal cooling water was reduced from above 60.0 μg/L to below 5.0 μg/L, indicating that the corrosion of copper wires was suppressed with good application results.

Keywords

• internal cooling water
• ph
• conductivity
• hydrogen conductivity
• model