Monitoring and Control of Water Chemistry in the Power Unit Turbine Generator Water Cooling System

Abstract

Electrical conductivity, pH, and oxygen concentration, all continuously measured in circulation water, are the key water chemistry (WC) parameters monitored in a power unit turbine generator water cooling system. With a shift for the use of water cooling in the turbine generator systems at thermal power plants (TPP) and for designing of such systems for turbine generators of the T3V-1200-2AU3 series at NPPs, problems were encountered in meeting the circulation water quality standards and in WC control. The article presents a method for determining by calculation the standardized values of electrical conductivity and pH in metering NaOH in a circulating cooling system (CCS) depending on these indicators in makeup water (water medium with low buffering capacity). The turbine generator water cooling systems serve for intense heat removal from the stator (and rotor) windings and are widely used in the power units at TPPs and NPPs. The cooling (circulation) water quality is standardized with respect to several indicators, the main ones of which are electrical conductivity and pH. In view of quite stringent standards on electrical conductivity, especially for the turbine generator rotor cooling system (below 1.43 μS/cm), there is nothing to do but use deeply demineralized weakly acidic water (рН < 7.0), and it is not permitted to use ammonia. For the acidity to be neutralized with NaOH solution, very precise controlled metering is required: with an insufficient quantity of NaOH, the рН will be below 6.5 (the lower limit), and with an excessive quantity of NaOH, the pH value will exceed 9.0, which is the upper permissible limit for the CCS. A mathematical model of ionic equilibria in the CCS circulation water is constructed and solved. With NaOH solution metered within the range of permissible values, the electrical conductivity and pH value adjustment boundaries are determined depending on the source and makeup water quality. An author’s certificate for a software product has been received. Given the existing makeup water quality and unchanged CCS process circuit arrangement, the performed study makes it possible to recommend installing an automated system for metering NaOH solution into circulation water based on the prescribed electrical conductivity value.