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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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This study was conducted to investigate the operation of a packed distillation column and analyse its performance during the separation of mono-ethylene glycol from water. The column was designed and constructed by the Curtin Corrosion Engineering Industry Centre (CCEIC) and operated in collaboration with a reputable oil company to generate experimental field data. A secondary investigation was then performed into the impacts of dissolved salts within the rich MEG feed upon the purity of the lean MEG product. It was observed through application of the FUG shortcut distillation design equations that six equilibrium stages were required to attain the experimental separations reported under continuous operation of the column. It was further determined that the packing utilised within the column had a Height Equivalent to a Theoretical Plate (HETP) of approximately 0.34 metres when no dissolved salts were present corresponding to an estimated packing height of approximately 1.7 metres. The impact of dissolved salts upon the performance of the column was evident through lower lean MEG purities observed during experimental operation of the column in comparison to salt free trials. The reduction in column performance was reaffirmed by Aspen HYSYS and Aspen Plus simulations of the field data, where salt trials resulted in lean MEG purities noticeably less than corresponding salt free experimental trials and simulated predictions. Overall, it was observed that the presence of dissolved salts during operation led to a reduction in MEG mass fraction of the final lean MEG product by on average 7.2%. The impact of dissolved salts on lean MEG purity was successfully predicted by Aspen Plus simulation with an average accuracy of 1.61% through the inclusion of monovalent salt cations using the ELECNRTL equation of state with modified binary parameters. The reduction in lean MEG purity was attributed to boiling point elevation of the MEG-Water solution and the impact of the dissolved salts on the systems vapour liquid equilibrium.

Magnesium, with its low density, is a very interesting metal in applications in which weight is important. In this work the initiation of corrosion attacks on magnesium alloy AZ91D has been investigated under atmospheric conditions, using confocal laser scanning microscopy and SKPFM. The corrosion attack starts in the ␣ phase in larger grains and is under atmospheric conditions initiated at the boundary between the ␣ phase and the eutectic ␣-/␤ phase. The SKPFM measurement shows that a high Volta potential difference exists between the larger grains and the surrounding eutectic ␣-/␤ phase and the ␤ phase. A microgalvanic element is formed in the thin adlayer on the surface, with anodic Mg dissolution in the ␣ phase and the cathodic reaction primarily in the eutectic ␣-/␤ phase. The initiation in the larger grains could be explained by the smaller aluminum content in the larger grains due to the solidification process. Even though intermetallic Al-Mn particles show a high Volta potential difference with the connecting ␣ phase, they are not involved in the initiation of the corrosion. This is explained by the position within the microstructure of Al-Mn particles embedded in the ␤ phase and located away from the ␣ phase.Magnesium alloys have low density and high specific strength, and these properties have created a great deal of interest in the use of these alloys in the motor and aerospace industries and in portable electronics. All of these industrial areas deal with applications in which weight is important. However, a big problem with magnesium alloys is their unsatisfactory corrosion properties. Understanding the corrosion properties of these alloys is vital if they are to become suitable alternatives for lightweight automotive components.In recent years, significant improvements have been made in achieving better corrosion resistance, particularly by reducing the contents of impurities such as Fe, Cu, and Ni. Intermetallic phases, a result of the casting process, play an important role in the corrosion process. The role of these intermetallic phases has been addressed in a number of article. 1-6 However, despite the fact that magnesium alloys as structural materials are mostly used in atmospheric environments, the interpretation of the effect of microconstituents is almost exclusively based on electrochemical data obtained from measurement in solutions. The corrosion processes in aqueous solutions are different from those occurring in an atmospheric environment.In an earlier work 7 the authors investigated the local nobility of the different intermetallic phases in the AZ91D alloy with the help of scanning Kelvin probe force microscopy ͑SKPFM͒. The results showed that under laboratory air conditions both the Al 8 Mn 5 and the ␤-Mg 17 Al 12 phases of the AZ91D alloy had a Volta potential which was, respectively, approximately 400 and 200 mV more noble than that of the ␣-magnesium phase. In the present work the influence of these intermetallic phases on the initial atmospheric corrosion process has been investi...