SRE Postscript – Trace Oxygen in Raw Gas

Q4 2017 saw SRE complete a number of interesting projects.  For one gas plant in Canada, SRE was involved with determining the source of corrosion with our client’s gas sweetening unit.  In an amine system, corrosion problems can easily be identified by the color of the amine: pale green indicating light corrosion; brown indicating corrosion greater than the filtration capabilities; and black indicating dangerous levels.  Although there are many sources for corrosion, our client had already identified that their corrosion was most likely cause by an increased amount of Bicine.

There are several mechanisms for producing bicine in amine gas treating facilities which include (1) reaction of diethanolamine (DEA) with glyoxal – a common hydrogen sulfide (H2S) scavenger – and (2) exposure of the heated gas treating solution to an oxidizer. Bicine impacts gas treating amine solutions in two ways. First, it forms heat stable amine salts (HSAS) and second, it increases the corrosivity of the amine solution.  Here, it was thought that the oxidizer was Oxygen (O2) ingress from the field raw gas.

As such, SRE’s scope of work was to complete trace O2 analyses at various points through the gas plant, including the raw gas from each field and throughout the inlet lines to the Amine contactors.  In one day, SRE conducted 22 trace O2 measurements from 10 different locations.  Sampling was extensive as a 3-minutes sample time and portable equipment allowed the site Engineer to be able to request extra measurements for due diligence.  These capabilities are in stark contrast to a trailer full of equipment and a 2-hour run time – 1 hour to mobilize, 30 minutes to warm up line and 30 minutes to conduct analysis – used by other testing companies, where 22 samples could take a few days & cost 3 times more.

Results ranged from 20 ppm to 250 ppm with all raw gas inlets having a measurable amount of O2.  The site Engineer planned to use the data to conduct their own material balance and to continue to mitigate the amine system corrosion.