Real-time monitoring of water levels in glycols using a solid state FTIR-based sensor
For the chemical and petrochemical industries, monitoring water content in glycols is key to many production processes. Glycol dehydration, for example, is a common step in petrochemical production. Standard methods of measuring water in glycols have their challenges that force many to juggle speed of results versus expense and accuracy. Manufacturers are looking for a better way to monitor this process. Keit has developed the solid-state IRmadillo™ FTIR spectrometer for in situ monitoring of industrial processes to provide continuous real-time results.
But how do you monitor the level of water in glycols?
Common water quantifying techniques – all with different challenges
- Karl Fischer titration – this is a common technique for quantifying water levels in liquids. It is highly accurate and precise but requires taking a sample extract, is slow, and expensive.
- Mass loss calculations –a straightforward technique but is affected by all volatile compounds present and can be very inaccurate. It still requires a sample extraction and can be very slow.
- Online spectroscopic techniques – these are real-time measurements with good levels of precision and accuracy. Until recently they haven’t been truly suitable for online analysis, but the development of Keit’s IRmadillo enables real-time, online measurements.
The need for a robust solution
Spectroscopic measurements typically fall into three main types for process analysis: near infrared (NIR), Fourier transform infrared (FTIR) and Raman spectroscopy. Both Raman and NIR instruments can be used in industrial processes, but they lack any real sensitivity for water. Conventional FTIR spectrometers are more sensitive to water but necessitate the use of fragile fibre probes, which are wholly unsuited for the industrial environment.
Keit now offers a novel technology to address this challenge.
Keit has developed a novel FTIR sensor that is inherently vibration resistant and goes beyond what a conventional FTIR spectrometer can endure. With avoidance of all moving parts and fibre probes, Keit’s IRmadillo offers a tough and resilient method of process monitoring enabling real-time online process monitoring. Suitable insertion points for the IRmadillo into a typical glycol dehydration process are shown in Figure 1.
IRmadillo and analysis of water in MEG & TEG
The Keit IRmadillo is an innovative solid-state technology certified safe for use in hazardous environments. This makes it ideal for application in chemical and petrochemical manufacturing. But, how well can it measure water in glycols?
As it turns out, excellently.
In our application note, the IRmadillo was used to analyse individual samples of monoethylene glycol (MEG) and triethylene glycol (TEG) with known concentrations of water. Samples were acquired and spectra were used to build chemometric models. The data were analysed using orthogonal signal correction (OSC) and partial least squares (PLS) models to predict the concentrations in real time.
After analysis, the results show that the IRmadillo produced results showing an excellent correlation between the measured and reference samples. This means that the IRmadillo can accurately measure the water concentration with great precision.
In fact, the results showed that it is possible for the Keit IRmadillo to monitor drying of MEG and TEG to >99.985 and 99.990 % respectively.
The IRmadillo™ is an effective, accurate and precise sensor for measuring water in glycols. It has been demonstrated directly for monoethylene glycol and triethylene glycol, but the technique is applicable to any glycol dehydration mix. It is possible to monitor water contents to 139 ppm in MEG and 96 ppm in TEG.
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