How to analyze the ODACON concentration to make the application safe and cost effective?
Measuring the right concentration is one of the key parameters to successfully implement a film forming amine (FFA) treatment program. It doesn’t matter if this is done in a low-pressure industrial boiler or a fossil power plant or for a short-term application like preservation or continuous dosing. It´s not only to safe chemicals and therefor reduce the operational costs. Controlling the concentration of FFA is critical to avoid overfeeding, which can cause serious problems like formation of “gunk balls”.
A bit of History
Starting in the 1970s ODA was chosen as the preferred FFA for the application in nuclear power plants. An enormous R&D program started to develop a safe and efficient treatment program for the secondary circuit of nuclear power stations with film forming amines. One of the key success parameters was, to develop a simple but accurate and reliable measurement methodology. Based on the Silverstein Method a procedure was developed using Methyl Orange to form a yellow complex with ODA which is soluble in Chloroform. The intensity of the colored complex is proportional to the total amount of the FFA in the sample.
The importance of accurate samples
Measuring ODA or any other FFA requires a grab sampling. This needs to be done very accurate as it has a major impact on the results. Besides the standards for grab sampling, like having a cooled sample, use only adequate sample bottles, etc. the sample taking for FFA analytic requires a bit more sensitivity. For example, it is recommended to always use the same bottles for the same sampling point. Also, the sample bottles need to be flushed with sample media 3 – 4 times.
For our procedure we provide an additional buffer solution. This buffer solution needs to be filled into the sample bottle before taking the sample. It adjusts a pH of 3.4 – 3.6 in the sample to decrease the reaction rate of ODA and avoid a filming of the sample bottle. Also, this weakly acidic pH is necessary to form the complex between ODA and Methyl Orange.
How to do it in the lab?
The laboratory procedure is a photometric method, and it covers the determination of ODA in a range of 30 to 2000 ppb.
In a separating funnel the sample is mixed with Methyl Orange and Chloroform. To achieve a homogeneous distribution the funnel is closed with a stopper and must be shaken for five minutes. After a further waiting time of three minutes the chloroform phase at the bottom is separated in a beaker. To remove a possible turbidity caused by water, isopropanol can be added and well mixed. The absorbance of the colored (yellow) solution is measured immediately with a spectrophotometer at 430 nm in a 1 cm cuvette. As there is a linear relationship between ODA concentration and extinction up to an ODA concentration of 2 ppm the concentration can be easily calculated by dividing the extinction with 0.392.
Is there a field test available?
Of course, we provide an easy-to-use field test to measure the concentration without having a spectrophotometer or laboratory. We recommend using the CHEMets filming amine kit (K-1001). It is based on the same Methyl Orange Method as we are using for the laboratory procedure. The test kit contains 20 test ampoules as well as a comparator. The comparator contains a set of color standards (sealed ampoules) containing dye mixtures that are formulated to match the colors produced by the test ampoules. The color standards are yellow in color and cover a range of 0-1 ppm ODA.
Is there any possibility to measure ODACON online?
Especially for critical applications in power stations with turbine operation or industrial applications with higher restrictions of the steam purity, like food processing industry, a continuous reading of the FFA concentration is often requested. Since a few years Waltron Bull & Roberts LLC is offering a Filming Amines analyzer. Firstly tested in 2019 the analyzer operated successfully on several different FFA products. The measurement methodology is based on the Bengal Rose method in combination with a colorimeter. The measurement range is between 0 and 500 ppb with an accuracy of +/- 10 ppb. Every 20 minutes it performs a reading of the FFA concentration in the sample stream.
In 2023 the first Waltron Filming Amines analyzers were installed at customers sites in New Zealand to control the concentration of ODACON in the steam used in a hospital. Further applications are planned in Australia and Sweden.
3054 Filming Amines Analyzer Quelle: SysAdmin. (2023, 22. Juni). 3054 Filming Amines Analyzer | Low Cost of Ownership. Waltron - Experts in water chemistry since 1903. https://waltron.net/analyzers/3054-filming-amines-analyzer/
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