The transportation of wet gas fluid in carbon steel pipelines for onshore processing offers an economically attractive strategy. Although a substantial saving in capital cost can be realised, the risks of hydrate formation and corrosion damage are two of the main issues with such an approach. The standard industrial practice is to apply chemical solutions to reduce the risks. A thermodynamic hydrate inhibitor, such as monoethylene glycol (MEG) and corrosion inhibitors are commonly utilized to provide hydrate and corrosion control, respectively. Other production chemicals, such as an oxygen scavenger, may also be deployed as part of the risk management process. Consequently, the main challenge to the corrosion inhibitor is to provide corrosion protection throughout the production and processing facility while subjected to high temperatures in the MEG regeneration process and exposure to other production chemicals. Thermal stability and performance assessments should be an important aspect of the qualification process in the selection of corrosion inhibitors. This paper presents data from laboratory corrosion inhibitor evaluation programs, using thermally stressed MEG/chemicals under simulated wet gas pipeline operating conditions, which resulted in the successful qualification of a corrosion inhibitor for the production facility. In addition, the performance of oxygen scavengers for use in MEG systems is reviewed, including details of an oxygen scavenger that performs in lean MEG.

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Summary This study investigates the oxygen-scavenging behavior of bisulfite ions in monoethylene glycol (MEG)/water mixtures at concentrations commonly found in gas-transportation pipelines. Temperatures and pH values were varied. The influence of transition-metal (TM) ions to catalyze the bisulfite oxygen scavenging was studied. Experimental results indicate that MEG significantly inhibits bisulfite oxygen removal, which is hindered at low pH values and, to some extent, temperature. TMs can accelerate the oxygen-scavenging reaction in pH-unadjusted solutions, although the rate was still lower than that of the pH-adjusted solutions. The possible mechanism for such behavior and industrial implications are discussed.

The pit stability product of 316L stainless steel (SS) under a salt film was examined by experimental techniques, analytical methods, and numerical modeling. Both analytical and numerical results suggested that electromigration had a measurable contribution to the dissolution current during stable pit growth under a salt film, preventing the use of the 1D Fick's law of diffusion to obtain the pit stability product under such conditions. Moreover, the numerical results indicated that migration contributed to almost ⅔ of the mass transport limiting current. Although the diffusion coefficient of metal cations decreased with an increasing concentration inside the pit, it could be replaced by a constant diffusion coefficient, defined as an equivalent diffusion coefficient. When the complexation reaction was cconsidered, the modeling results agreed with the experimental data, indicating that a 4.2 M FeCl 2 could be used as a simplified pit-like electrolyte to estimate the pit stability product under a salt film for 316L SS.

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