The behavior of mercury in water, alcohols, monoethylene glycol and triethylene glycol

- Solubility of mercury is reported for water, several alcohols, MEG and TEG.
- Elemental Hg may be stripped from MEG solution by petroleum gas.
- Hg partitions to the distillate phase during regeneration of MEG.
- Hg after inlet separators in rich MEG is particulate HgS.

The oil and gas industry is becoming aware of the effects of produced mercury on hydrocarbon processing systems, and that produced mercury contaminates processing equipment. The use of technical information is critical to planning for decommissioning, decontamination and waste minimization. To this end, the solubility of mercury in the polar solvents - water, alcohols, monoethylene glycol (MEG) and triethylene glycol (TEG) have been determined from approximately 243 to 373 K. Elemental mercury solubility in MEG and TEG is somewhat higher than that reported previously in the literature when a mass of mercury was agitated for several days in the respective solvent. Elemental mercury was nearly quantitatively stripped from water by natural gas in a small laboratory stripping column, and in a distillation experiment, about 75% of Hg0 in 40 vol% MEG partitioned to the distillate phase. Elemental mercury is present in process inlet flow lines and can drop out. This is expected if the reservoir is both hot and saturated with elemental mercury (common), and the pipeline is colder (common). However, in the inlet separator, any dissolved mercury is removed by the drop in pressure and the flashing of C1-C4 hydrocarbons. These light hydrocarbons are very effective in stripping Hg0 from the crude and condensate. What remains in the crude and condensate is particulate metacinnabar, β-HgS. In amine treaters and glycol dehydrators a portion of the Hg0 in the gas can react with traces of oxygen to form heat-stable salts. These can further react to form Hg-rich sludges. The success of the experiments will be useful to the industry in understanding the behavior of mercury in polar solvents, gas hydrate inhibition and in glycol and amine contactors.