In the production of liquefied natural gas (LNG) methane is compressed from initial conditions  of {P =1bar, T = 30o C} to a final pressure of P =100bar , in a three compression stages (see 116  process diagram below). The first compressor delivers a discharge pressure of P2 and the second  a discharge pressure P4 . The intermediate coolers, cool the hot compressed gas to a temperature    of T = T = 30o C using process cooling water. The final compressed methane stream is cooled {} 

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with liquid propane available at a temperature T = −45o C down to T = −40o C . After the {}{} 

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 refrigeration the propane which is now saturated vapor is compressed and subsequently cooled 

with process cooling water so it can be recycled. The following data are available: The flow rate of methane is {F = 200 MMSCFD}, the cost of process cooling water is 0.354$/GJ, the cost of 

electricity is $16.8/GJ and the cost of the refrigeration $13.11/GJ. The cooling water is available 

at a temperature of 30o C . Calculate the annual operating cost of the process.  Assume that all compressors have an efficiency of 80%. 

 

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Question Calculate the annual operating cost of the liquefied natural gas LNG production process To ... View the full answer