PEFTEC 2019 - Abstract

Abstract Title: A robust and rugged FTIR spectrometer to measure online water content during glycolic dehydration for the petrochemical industry
Abstract Type: Oral
Session Choice: Analytical Techniques: Molecular Spectroscopy and On-Line Analysis
Presenter Name: Dr Dan Wood
Co-authors:Mr Jonathon Speed
Company/Organisation: Keit Spectrometers
Country: United Kingdom

Abstract Information :

Removal of water from natural gas and petrochemicals is an important part of the petrochemicals production process, and a common method of this is glycol dehydration. This process involves feeding lean and water-free glycol (with a purity of > 99%) into a dehydration unit, which then forms physico-chemical interactions with water, removing it from the stream. Typical glycols used are mono-, di-, tri-, and tetra-ethylene glycol (MEG, DEG, TEG and TREG respectively). To maintain a cost-effective, process the glycol must be re-used and recirculated through the process, but it is important to effectively dry the glycol before reuse to ensure the process remains efficient.

There are numerous different methods of studying and quantifying the constituents of glycol-water mixtures, including physical methods such as differential scanning calorimetry1 or Karl Fischer titration, and spectroscopic measurements such as near2 (NIR) and mid3 (MIR) infrared spectroscopies. The physical methods cannot be used for online and in process measurements, making them unsuitable for many industrial applications. NIR measurements can be performed online, but the technology is often not sufficiently sensitive to ensure the glycols are sufficiently dry. MIR measurements are highly sensitive to water, but conventional MIR FTIR spectrometers contain fragile assemblies of moving mirrors and/or delicate fibre optic probes, both of which make them unsuitable for the industrial environment.

Here we present the use of a novel vibration resistant FTIR spectrometer to study the water content in glycols. The spectrometer has been designed to contain no moving parts or fibre cable, ensuring that it is robust and rugged, but maintaining the sensitivity and selectivity benefits of FTIR systems. The water content of both MEG and TEG was studied as well conventional organic solvents. By using a simple partial least squares (PLS) model the spectrometer can be used for process analytical technology (PAT) to quantify water in real-time. The LOD for water was found to be < 1000 ppm, meaning a purity of 99.9% glycol was reliably measured. This PAT approach enables a plant to run at higher efficiency, reducing both cost and waste.