Novel Identification Method of Seawater Contamination into Steam-Water Circuit Including Carbon Dioxide of Power Plants Based on pH, Specific Conductivity, and Cation Conductivity

Abstract

In the steam-water circuit of power plants, cation conductivity is measured to detect the contamination of impurities such as seawater promptly and prevent equipment and piping from corrosion damage. Cation conductivity is obtained by measuring the electrical conductivity of the sample after the cation exchange pretreatment, this makes it possible the highly sensitive detection of anion impurities. On the other hand, due to the policy of increasing the introduction of renewable energy, the start and stop operation of gas turbine combined cycle (GTCC) power plants is increasing. As a result, the interference of cation conductivity by carbon dioxide which is contaminated from the air during plant outage will increase, and it becomes a matter of concern of the detection delay of impurities contamination. Therefore, the novel identification method of impurities based on the pH, specific conductivity, and cation conductivity which is monitored conventionally in the steam-water circuits is investigated. As a result of the calculation of impurity concentration using a novel model for simulated water quality of steam-water circuit prepared by chemical equilibrium calculation software, OLI Analyzer, it is confirmed that the calculation error of carbon dioxide concentration not from seawater is 0.0% to 18% more than 0.1 mg/L, and that of contaminated amount of seawater is 0.0% to 20% more than 1 × 10−6 m3/m3, which is regarded good agreement, respectively. Additionally, the calculated results with the measured data in the actual plant are consistent with the assumed behavior based on the plant status. In conclusion, it is indicated that the contaminated amount of seawater is precisely estimated also in the case of the coexistence of carbon dioxide and seawater by using the novel method.

Keywords

• Chemical equilibrium
• Ammonia
• Carbon dioxide
• Ph
• Conductivity