This invention is a method and apparatus for monitoring the concentration of
carbon dioxide dissolved in water by means of
conductivity. It distinguishes between the
conductivity resulting from
carbon dioxide and the
conductivity resulting from other constituents dissolved in water. It can be used to monitor the quality of demineralized water,
boiler feedwater, steam, or condensate in
electric power generation and other industrial facilities. It is constructed by adding a column containing
weak base anion exchange resin and a conductivity instrument to a typical cation conductivity monitor. A sample of the water to be monitored flows first through a typical cation conductivity monitor, then through a
weak base anion exchange column, and then through an additional conductivity instrument.
Conductivity measured at the outlet of the
weak base anion exchange column will be essentially due to whatever concentration of
carbon dioxide is dissolved in the sample because other dissolved constituents that affect conductivity have been essentially removed by either the cation exchange resin that is part of a typical cation conductivity monitor, or by the weak base anion exchange resin. By subtracting the value of conductivity due to carbon dioxide (at the outlet of the weak base
anion exchange column) from the value of cation conductivity (at the outlet of the cation exchange column), the value of degassed cation conductivity is obtained. In the title of the invention, CWB conductivity is an abbreviation for cation—weak base conductivity.In combination with existing methods for oxidizing organic compounds dissolved in water, this invention is also a method and apparatus for monitoring the concentration of dissolved or
total organic carbon in water by means of conductivity. It distinguishes between the conductivity resulting from organic carbon and the conductivity resulting from inorganic constituents dissolved in water including carbon dioxide.