On-Line Monitoring of Water in Ethylene Glycols with a ClearView® db Photometer

Purpose:

To determine water content in ethylene glycol (EG) without sample temperature control.

Experimental:

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 path length SST probe. The resulting data were then used to define the wavelengths for our on-line process photometer.

Results:

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 Ethylene Gycol Mixtures at Various Temps

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

Conclusion:

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 path 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.

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

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