Studying mercury partition in monoethylene glycol (MEG) used in gas facilities

Mercury partitioning from monoethylene glycol (MEG) during natural gas production is a highly complicated process. Understanding this process will help determine the distribution of mercury species within a given industrial process so that appropriate mercury removal control systems can be effectively managed. In this study, the partitioning of elemental mercury (Hg0) from the gaseous phase into MEG solutions is investigated under standard laboratory conditions. Additionally, the partitioning of dissolved ionic mercury (Hg2+) from MEG solutions into the gaseous phase is also investigated under atmospheric pressure and room temperature conditions. It was found that the solubility of Hg0 in MEG ranged from 0 to 60 ppb (ng/mL) with slight increase to ∼80 ppb when the pH was reduced from ∼9 to ∼6 at room temperature. On the other hand oxidized mercury (Hg2+) was found to be retained in the laboratory grade MEG and industrial samples of MEG (industrial-MEG). However, in the case of the industrial-MEG, the dissolved mercury (HgCl2 salt) was found to be unstable with approximately 3.6% and 10% converting within the solution and leaving in the gas phase as Hg0 and Hg2+, respectively, while the balance was retained in the MEG solution. The distribution was found to be highly pH dependent and was not observed when the experiments were repeated using laboratory grade MEG solutions. These findings help in better understanding the type and ratio of mercury species that are partitioned in and out of MEG in the gas processing facilities.