Buffering and Inhibition of Glycol in Gas Dehydration Applications: an Alternative to Amines

Abstract Corrosion in gas dehydration systems can be attributed to many factors, including chloride intrusion, acid gas absorption, and glycol degradation. Inhibition systems for glycol dehydration systems must incorporate both corrosion inhibition and buffering, utilizing stable, non-scaling, non-depleting additives. Traditional amine treatments are unstable in carbon dioxide containing gas streams; traditional inorganic salt glycol inhibitors are unstable and cause scaling in the presence of intruded mineral salts. The instability of these inhibitors leaves a dehydration system unprotected against high chloride intrusion; and results in high costs in maintaining inhibitor levels. An alternative inhibitor technology was tested in three field test programs, under various dehydration conditions. Traditional nitrite, molybdate, and amine inhibitors were tested in combination with the alternative technology; uninhibited and amine inhibited control units were included in the study. Corrosion rates and dehydration fluid chemistries were monitored. The field tests demonstrated the effectiveness of the non-amine-based alternative technology in reducing corrosion rates and maintaining the alkalinity of the glycol dehydration fluid. Corrosion rates at the reboiler in systems treated with the alternative technology averaged ten times less than the average rate in the control units, and had a substantially lower incidence of localized corrosion. The pH of the treated glycol stayed alkaline throughout the testing, varying within 0.85 pH units; whereas corresponding control units showed wide swings in pH, ranging from an acidic 4.1 to an alkaline 10.3. No operational difficulties, including foaming, inadequate drying, or excess glycol loss, were experienced in the treated dehydration units. Testing of the alternative technology in combination with more traditional technologies revealed no significant benefits over the alternative technology alone; however, the alternate technology showed significant improvements in both corrosion control and stability over traditional amine inhibition.