The formation of hydrocarbon gas hydrates can be greatly facilitated by subsea operating circumstances in well-heads and flowlines in deep waters, which are frequently characterized by low temperatures of 0 to 4 °C and high pressures. Gas hydrate from water vapor falls down as snow-like particles, which may settle to form plugs.
Mono Ethylene Glycol (MEG) injection at the wellhead is a widely spread method of hydrate inhibition that ensures constant gas production. In particular, generated water from the extraction of natural gas from deep-water reservoirs often comes with a large quantity of produced water that may have salinity close to saturation. Once blended with the MEG stream, where the mineral salts are often significantly less soluble, the concentrated brines represent a higher risk of scale formation and deposition in the production line, which, if left untreated, may also present a serious risk to flow assurance. If salt is introduced to the glycol system along with production fluids, its concentration will rise with each regeneration cycle until the solubility limit is eventually reached, at which point precipitation will take place. Accordingly, the installation of a MEG reclamation and regeneration system is crucial to recover MEG suitable for reuse.
There are three main steps in an integrated MEG recovery package: conditioning, reclamation, and regeneration. In conditioning section, hydrocarbons, acid gases, corrosion products, etc. are removed from the entering rich MEG. Then, in reclamation section, MEG and water vaporize under vacuum condition to produce a concentrated slurry of salts. Solvent reclamation can be carried out either by continuous or intermittent removal from either the complete circulation stream or alternatively a portion slipstream, depending on the magnitude of the contamination problem. Finally, in regeneration, water and MEG are separated under vacuum to obtain lean MEG at the appropriate concentration and water with low MEG content.