Liquefaction

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Liquefaction

• uses
• liquid propane fuel
• Liquid hydrogen as fuel (fuel cells)
• liquid nitrogen as coolant
• liquid oxygen for rocket fuel
• OBJECTIVES
• To describe how liquefaction is accomplished
• To analyze a liquefaction process

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Liquefaction Process

• accomplished by cooling a gas to a T in the
  2-phase region

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Liquefaction Processes

• simple process
• Linde process

cooler
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Example

• A process is set up to produce liquid methane
  (natural gas) from an initial T of 280 K and P of
  1 bar. Leaving the heat exchanger, methane is at
  200 K and 100 bar. The flash drum is well
  insulated and has a P of 1 bar. The compressor
  operates isentropically. Because of the large
  pressure change, a 3-stage compressor with
  interstage cooling is used. In the first stage,
  the gas is compressed from 1 to 5 bar, in the
  second from 5 to 25, and in the third from 25 to
  100 bar. After each compression stage, the gas
  is isobarically cooled to 280 K. Calculate the
  amount of work required in the compressor for a
  simple liquefaction process and for a Linde
  process, assuming that, in the Linde process, the
  recycled methane leaving the heat exchanger is at
  210 K and 1 bar. The thermodynamic properties of
  methane are given in the accompanying figure.

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