No abstract

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.

The acid dissociation constants (pK a) of four organic acids (formic, acetic, propanoic, and butanoic) commonly found in monoethylene glycol (MEG) regeneration systems and methyldiethanolamine (MDEA) were measured via potentiometric titration. Dissociation constants were measured within varying concentration of MEG solution (0, 30, 40, 50, 60, 70, and 80 wt %) and at varying temperature (25, 30, 40, 50, 60, 70, and 80 °C). Thermodynamic properties of the dissociation process including Gibbs free energy (ΔG° kJ mol–1), standard enthalpy (ΔH° kJ mol–1), and entropy (ΔS° kJ mol–1 K–1) were calculated at 25 °C using the van’t Hoff equation. Comparison of the reported experimental pK a values and calculated thermodynamic properties in aqueous solution to the literature demonstrated good agreement. Two models have been proposed to calculate the pK a of acetic acid and MDEA within MEG solutions of varying concentration, temperature, and ionic strength. The proposed models have an average error of 0.413% and 0.265% for acetic acid and MDEA, respectively.

Methyldiethanolamine (MDEA) is a widely used chemical in the natural gas processing industry as a solvent for CO 2 and H 2 S capture and as a basic compound for pH stabilization corrosion control. During pH stabilization corrosion control, the removal of MDEA during the (mono)ethylene glycol (MEG) regeneration process may occur under vacuum conditions during reclamation in which the removal of salt cations is performed. Isobaric vapor−liquid equilibrium data for the binary MEG−MDEA system is presented at (20, 10 and 5) kPa and water−MDEA system at (40, 20, 10) kPa to simulate its behavior during MEG reclamation under vacuum. Vapor and liquid equilibrium concentrations of MDEA were measured using a combination of ion chromatography and refractive index. The generated experimental VLE data were correlated to the UNIQUAC, NRTL, and Wilson activity coefficient models, and the respective binary parameters were regressed.

The experiments performed as a part of this study were conducted to evaluate the effect of magnetic field treatment upon the scale forming tendency of brine solution composed primarily of calcium bicarbonate ions. The reported results were generated using a Dynamic Scale Loop system with the brine solution exposed to a magnetic field generated by a 6480 Gauss magnet of grade N45SH in a diametrical orientation for 2.5s. Following magnetic exposure, the brine solution was exposed to an elevated temperature 150°C at 1bar to promote the formation of scale within a capillary tube. The extent of scaling was measured by recording the differential pressure across the tube as scaling proceeded. Three important conclusions regarding the effect of magnetic field treatment upon scale formation in calcium bicarbonate solutions were reached. Firstly, the ratio of calcium to bicarbonate plays a key role in determining how magnetic fields influence scale formation, whether promoting or inhibiting it. Solutions containing high concentrations of the bicarbonate, or equal concentrations of the bicarbonate and calcium species showed inhibited scale formation following magnetic exposure. Secondly, the electrical conductivity of the calcium carbonate solution was noticeably impacted by the exposure to the magnetic field through manipulation of the ionic hydration shell and may also provide a measure of the extent of scale formation. Finally, the application of magnetic field treatment for scale inhibition may provide an alternative eco-friendly scale inhibition strategy in place of traditional chemical scale inhibitors.