Gas hydrate formation and corrosion
within gas pipelines are two
major flow assurance problems. Various chemical inhibitors are used
to overcome these problems, such as monoethylene glycol (MEG) for
gas hydrate control and methyl diethanolamine (MDEA) and film formation
corrosion inhibitor (FFCI) for corrosion control. As an economical
solution, MEG is regenerated due to the large volume required in the
field. MEG regeneration involves thermal exposure by traditional distillation
to purify the MEG. During this process, MEG is subjected to thermal
exposure and so might be degraded. This study focuses on evaluating
six analytical techniques for analyzing the degradation level of various
MEG solutions consisting of MDEA and FFCI that were thermally exposed
to 135 °C, 165 °C, 185 °C, and 200 °C. The analytical
techniques evaluated are pH measurement, electrical conductivity,
change in physical characteristics, ion chromatography (IC), high
performance liquid chromatography–mass spectroscopy (HPLC-MS),
and gas hydrate inhibition performance (using 20 wt % MEG solutions
with methane gas at pressure from 50 to 300 bar). Most of the analytical
techniques showed good capability, while electrical conductivity showed
a poor result for solution without MDEA and IC showed poor results
for solution exposed to 135 and 165 °C. The primary aim of this
paper is thus to provide the industry with a realistic evaluation
of various analytical techniques for the evaluation of degraded MEG
solutions and to draw attention to the impact of degraded MEG on gas
hydrate and corrosion inhibition as a result of the lack of quality
control.