Hydrate Inhibition
Methane hydrates are ice-like compounds that occur worldwide in sea-floor sediments on continental margins. In most offshore applications, hydrate formation is controlled by injection of a thermodynamic hydrate inhibitor. Methanol and mono-ethylene glycol (MEG) are common inhibitors. MEG is safer and has become a more attractive alternative to methanol on fields that require persistent inhibition.
Conventional regeneration systems are typically used to boil off water at close to atmospheric pressure. The operational temperature will depend on the required lean MEG content. The main components of these MEG regenerators include a column equipped with a reboiler and a lean/rich MEG heat exchanger. Salt, hydrocarbons, pipeline corrosion products and chemicals accumulate in the closed MEG loop. The up-concentration of contaminants causes excessive scaling, corrosion, plugging and carry-over foaming requiring that the MEG inventory be replaced at regular intervals.
Integrating a continuous slipstream desalting system with the conventional regenerator as shown in Fig. 2 prevents salt accumulation. The salt removal rate is determined by the allowable amount of dissolved salts in the lean MEG. Investment costs are favorable compared to costs of operational losses from reduced availability, increased maintenance, and consumption of MEG. The operating costs are directly related to the quantity of salt removal that is necessary. Figure 3 shows operating energy needed to desalt typical rich MEG feeds. Figure 4 shows a typical desalted rich MEG solution compared to the spent MEG that must typically be discarded.
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Industrial Heat Transfer Fluids
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