TOC-Analyser for Condensate Return
Detection of Impurities in Condensates and Ultrapure water
One precondition for a continuous trouble free boiler operation is an almost perfect protective coating on both sides of the heat exchangers. The quality of these passivation layers is a function of the conductivity in the water - steam cycle, i. e. the concentration of ionic species.
Inorganic and organic ionic species are removed by ion exchange resins, and don´t pose any thread to the protective layers. Neutral organic compounds are not removed and they are decomposed to organic and inorganic acids under conditions found in modern boilers. This yields to an increase in conductivity, higher corrosion and reduced maintenance intervals.
An analytical method that detects traces of organic impurities in feed water is therefore mandatory.
The Organic X value gives better information than the DOC-value.
DOC-Value
Most instruments for the determination of the DOC (Dissolved Organic Carbon) decompose the organic compounds and measure the amount of carbon dioxide formed (DIN 38 409). In most cases there is no correlation between the DOC and the conductivity increase due to the decomposition of these compounds in the boiler!
By simulating the decomposition process that takes place in the boiler the Organic X Monitor LC is able to determine the quality of boiler feed water unambiguously.
The following figure illustrates results from experiments that had been performed in a power plant be injecting small quantities of organic compounds into the boiler feed water. The different behaviour of various organic compounds in boiler and in the process of UV-treatment as performed by the Organic X Monitor LC is presented in the following figure. As can be seen the increase in conductivity for halogenated compounds is much higher than for halogen-free compounds. Furthermore decomposition of halogenated compounds starts at lower temperatures. Even during pre-heating at 270°C some decomposition of chlorinated compounds occurred. This indicates that even in older power stations with moderate steam temperatures some decomposition may happen.
The following figure illustrates results from experiments that had been performed in a power plant be injecting small quantities of organic compounds into the boiler feed water. The different behaviour of various organic compounds in boiler and in the process of UV-treatment as performed by the Organic X Monitor LC is presented in the following figure. As can be seen the increase in conductivity for halogenated compounds is much higher than for halogen-free compounds. Furthermore decomposition of halogenated compounds starts at lower temperatures. Even during pre-heating at 270°C some decomposition of chlorinated compounds occurred. This indicates that even in older power stations with moderate steam temperatures some decomposition may happen.
- Principle of operation: Conductivity after UV-digestion
- Range: 0,01 – 2 mg-C/l
- T90: > 1 Min. < 3 Min.
- Detection limit: 10µg/l, lower for some compounts
- Measuring channels: Max. 8 (option)
- Sample: Condensate, ultra pure water, cond. < 20µS/cm
- Alarms: System fault, NC/NO; Threshold, NC/NO (option); Maintenance request, NC/NO (option)
- Analog outputs: (0)4 – 20mA, galvanically isolated, max. 500 Ohms; Max.8
- Display: 4”-colour-touch panel
- Communication: Ethernet, Profibus (optional), Modbus (optional)
- Housing: Wall mounting, steel and plastic
- Dimensions: Width: ±400 mm x depth: ±270 mm x highth: ±910 mm
- Weight: ±30 kg