Development and utilization of Low Dosage Hydrate Inhibitors (LDHI) have been attracted researchers and industry for almost two decades. These inhibitors are known to be more effective, more environmental friendly, less corrosive and havelower capital and operational expenses. These inhibitors are usually classified to Kinetic Inhibitors (KI) and Anti-Agglomerants (AA). While kinetic inhibitors prevent hydrate formation by prolonging induction time of hydrate formation more than the residence time of free water in pipeline, anti agglomerants inhibits pipeline plugging acting as a hydrate emulsifier. Environmental aspects of commercial LDHI’s have encouraged researches to look for more environmentally friendly LDHI’s. Considerable efforts have been made to develop non-ionic surfactants e.g. Alkylamide or zwitterionic surfactants, which can be effective inhibitors or to utilize environmentally friendly materials like starch or anti-freeze proteins. In present paper, these research activities, patents and industrial reports are reviewed, including: chemicals with kinetic or anti agglomeration effects, their mechanism of acts, Compatibility, chemical screening and selecting methods like molecular Dynamics simulations, experimental procedures, data reproductivity, stochasticity, inhibitors synergism, multifunction inhibitors, inhibitors surfactant effects and surface interfacial properties, biodegradability, toxicity and environmental impacts.
Gas Hydrates are crystalline solids wherein guest (generally gas) molecules are tapped in cages formed from hydrogen bonded water molecules (host). CH4, H2S, CO2, C2H6, C-C3H6, (CH2)3O, C3H8, i-C4H10, n-C4H10 are some of these hydrate former gases. Gas hydrates ould form in pipelines causing serious operational and safety problems. Gas expansion and cooling effect, start up and shut down, well clean-up and testing, subsea separators and deepwater production are some of the scenarios for hydrate formation. For hydrate to be stable necessary conditions are Presence of water, suitably sized gas/liquid molecules, Suitable temperature and pressure conditions. To avoid hydrate problems, injecting inhibitors have been utilized as the most economical method. this chemicals based on their operational concentration are classified to: 1) thermodynamic inhibitors e.g. Methanol, ethanol, glycols, 2) Low Dosage Hydrate Inhibitors which are classified to 1- Kinetic hydrate inhibitors (KHI), 2- Anti-Agglomerants (AA). A widely used thermodynamic method is based on methanol injection. Thermodynamic methods using methanol and glycol are costly in offshore developments and onshore processing facilities because of the high treatment amounts required (10–50% of the water phase). Thermodynamic inhibitors prevent hydrate formation by shifting the equilibrium conditions so hydrate form in lower temperatures and higher pressures. Although there are opportunities to optimize thermodynamic inhibitor requirements, the high cost of thermodynamic inhibitors has stimulated the search for kinetic inhibitors.
Publisher : 2nd National Iranian Conference on Gas Hydrate (NICGH)
By : Amir Erfani , Farshad Varaminian, Milad Muhammadi
File Information: English Language/ 21 Page / size: 0.99 KB
سال : 1392
ناشر : دومین کنفرانس ملی هیدرات گاز (NICGH)
کاری از : امیر عرفانی، فرشاد ورامینین، میلاد محمد
اطلاعات فایل : زبان انگلیسی / 21 صفحه / حجم : KB 0.99