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

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 corrosion inhibition and buffering using stable, nonscaling, and nondepleting additives. Traditional amine treatments are unstable in gas streams containing carbon dioxide (CO₂). Traditional inorganic salt glycol inhibitors are unstable and cause scaling in the presence of intruded mineral salts. 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. Corrosion rates and dehydration fluid chemistries were monitored. Field tests demonstrated effectiveness of the nonamine-based technology in reducing corrosion rates and maintaining alkalinity of the glycol dehydration fluid. Corrosion rates at the reboiler in systems treated with the alternative technology averaged 10 times less than the average rate in 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. 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 traditional technologies revealed no significant benefits over the alternative technology alone. However, the alternate technology showed significant improvements in corrosion control and stability over traditional amine inhibition.