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Sum Parameter – Total Organic Carbon
Monitoring of cooling water with TOC-4200
No. SCA-130-610
Thermal power stations as well as the chemi- ■ TOC determination in cooling water
cal industry use water as an energy carrier to The TOC parameter provides information on
dissipate heat in various processes. The heat organic pollution. The TOC can be easily
energy of a process medium is absorbed by determined and is easy to implement in
cooling water via heat exchangers. process analysis. Two oxidation techniques
The absorbed heat in turn is emitted by means are now commonly used in TOC analysis:
of a cooling process. The cooling water is in- • Catalytic combustion, where carbon
troduced either directly into a water body (con- compounds are converted into CO 2 using
tinuous flow cooling), or cooled down by a a catalyst under high temperatures with
cooling tower beforehand. Water which did not subsequent detection of the resulting CO2
evaporate in the cooling tower is then being using an NDIR detector
discharged (discharge cooling) or reused in • Wet chemical oxidation, which uses a
the cooling circuit (closed circuit cooling). combination of UV irradiation and
Constant evaporation in the cooling circuit persulfate for oxidation. The resulting CO2
leads to an increase of salinity and to for- is either detected via an NDIR detector or
mation of carbonate scale, so that the water via conductivity detector.
has to be diluted or exchanged regularly.
When applying TOC determination to cooling
water, usually few particles are expected, but
here as well, it is better to be on the safe side
with the higher oxidation potential offered by
catalytic combustion. It is important to be able
to quickly and reliably detect every possible or-
ganic contamination. The analyser availability
is maximized by a combustion at temperatures
below the melting points of common salts.
■ TOC-4200
The high-performance TOC-4200 analyser ap-
plies catalytic combustion at 680 °C. Depend-
ing on the sample characteristics, the total in-
Usually cooling water is taken from a natural organic carbon (TIC) and the volatile organic
water body and purified by filtration systems. carbon (POC) can be measured in addition to
This avoids clogging of equipment and de- TOC and TC. In order to measure the total
creasing heat transfer rates. bound nitrogen (TN), the TOC-4200 can be
Organic contaminants in the cooling water or upgraded with a specific module.
fractured heat exchangers can cause reduced
process efficiency and damage to the plant
and the environment.
