Sodium and Silica in Power Plants
Both sodium and silica play a major role in corrosion in cooling water. For power plants, it is essential to keep the concentrations of these substances under control. With the ALERT-ion equipped with the Metrohm Na-ISE, it is possible to measure sodium concentrations down to 1 ppb. In case lower detection limits are required, the ALERT can be exchanged for the more accurate ADI2018 analyzer. Silica in cooling water or high purity water can be measured with the ALERT color, in concentrations as low as a 1 ppb.
Hydrazine in Ultra Pure water
Hydrazine is used as a corrosion inhibitor and oxygen scavenger. It is effective in treating boiler feed waters. The overall reaction with oxygen is
N2H4 + O2 = N2 + 2 H2O
It is a well known fact that oxygen free water is practically noncorrosive to steel as compared with water containing oxygen. However, due to the toxicity of the chemical it is important to be monitored throughout the process.
Condensate Measurement
The recovery of condensate in a power plant requires stable, reliable TOC values since
organic carbon (especially organic acids) can do serious damage at steam producing
devices. Such condensate may contain higher amounts of salt (up to 10-15%) which puts
special demands on the TOC analyser because such high salt contents can easily inhibit
the efficiency of the catalyst which is used in most of the high temperature TOC analysers.
An analyser using the UV oxidation method is of course totally inefficient at such high salt
concentrations. The TOC concentration of condensate water is usually <500ppb.
Furthermore the speed of the analysis is an issue, too. The capacity of the buffer tanks
usually is limited, the reaction time therefore hardly exceeds 30 minutes.
