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The formation of hydrates in deep sea natural gas tie-back lines had been traditionally inhibited by injecting Triethylene Glycol (TEG) or Methanol at the subsea manifold. Unfortunately, gelling of the TEG at the manifold or in the delivery umbilical and lack of recovery of the methanol were persistent drawbacks to their continuous use. CCR Technologies Ltd. (CCR) was instrumental in moving the offshore flow assurance mindset away from TEG and Methanol and towards Monoethylene Glycol (MEG) as the hydrate inhibitor ofchoice for multiphase tie back production lines. CCR designed and delivered the first commercial MEG Recovery Unit (MRU), which was started up in 1999 for Shell Mensa WD-143 Offshore Project in the Gulf of Mexico, USA.
This paper outlines some of the information required to properly specify a MRU and follows the decision points and opportunities for optimization that arise as the design develops from initial concept to a more detailed proposal. Although the MRU is typically considered a utility within the plant, the impact it can have on flow assurance should not be overlooked.