Online Monitoring of Water in Ethylene Glycols with a ClearView® db Photometer

NIR spectroscopy can be used to determine water content in ethylene glycol (EG) without sample temperature control. The NIR-O spectrometer was used to measure the NIR spectra of 0 to 100% water in EG in the 18- 43°C temperature range using a 10 mm optical path length SST probe. The resulting data were then used to define the wavelengths for our online process photometer.

Data Analysis of Water in Ethylene Glycol

The resulting spectra are shown in Figure 1 for five concentrations ranging from 0-100% water in EG, each at 20, 25, 30, 35, 40 and 45°C. To test the viability of a photometer for the real time monitoring of water in ethylene glycol. A multiple linear regression was performed, see Figure 2. Excellent linearity (R2>.9999) is achieved using 4 wavelengths in the range tested showing data at all temperatures.

Figure 1: Spectra of Water in Ethylene Gycol Mixtures at Various Temps

Figure 2: Actual vs. Predicted Percent Water in Ethylene Glycol

Guided Wave’s dual beam ClearView db photometer with four filters can be used to determine water from 0-100% in ethylene glycol using a 10 mm optical pathlength insertion probe, or a flow cell (for a slip stream) on-line. The ClearView db can be configured with 4-20 mA analog outputs (six answers max on a single channel system, and four per channel on a dual channel system) and corresponding contact closure outputs to alert error states. Modbus communication over Ethernet is also standard.

Application Note

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