(210d) Effect of NaCl and CaCO3 on the Density, Conductivity, and pH of MEG Solution: Implication to the Design of MEG Regeneration Process

Mono-ethylene glycol (MEG) is widely used as a hydrate inhibitor to prevent formation of hydrates in offshore gas fields and used to be regenerated in MEG regeneration process on-board platform. Typical distillation of water from MEG solution can be applied to purify the MEG, however the presence of various salts in produced water may induces difficulties in operating the process. Therefore salts such as NaCl and CaCO₃ are required to be removed efficiently to avoid the fouling of the regeneration process and to improve the energy efficiency. Through understanding on the physical properties of salt is required to better design of the MEG regeneration process. In this work, density, conductivity, pH and solubility of salts were studied in the MEG solutions containing both NaCl and CaCO₃. The concentration of MEG can be easily estimated from the concentration of NaCl, conductivity and density measurement. However the presence of CaCO₃ induces slight change in those properties, thus pH measurement is required to supplement the density and conductivity data for estimating the concentration of MEG. And it is essential to optimize distillation column considering both salt precipitation and wt% of MEG. To optimize the distillation column, thermodynamic properties such as salt solubility, vapor pressure of the fluid containing salts are required. Therefore, the salt solubility, vapor pressure of mixture (MEG+Water) with NaCl is experimentally measured. From the obtained physical properties of MEG solution, we develop the novel process to distillate the MEG solution. In the design of distillation column, the temperature has to be controlled carefully to increase the concentration of MEG in bottom product and to avoid the precipitation of NaCl especially inside the re-boiler. We propose the novel design of MEG regeneration while avoiding the precipitation of NaCl by investigating experimentally and by simulating the process using process simulation software, HYSYS V7.3 and Aspen Plus V7.3.