Calculators›Nitrogen Rejection Unit
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Nitrogen Rejection Unit (NRU) Calculator

GPSA · Plant Processing of Natural Gas Ch. 10 · Cryogenic Separation

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Nitrogen Rejection Unit Calculator
Designs cryogenic nitrogen rejection units to meet pipeline methane specifications. Calculates separation column performance, refrigeration duty, and methane recovery efficiency using distillation principles.

Feed Gas Conditions

MMSCFD
mol%
psia

Product Specifications

mol%
%
Pipeline spec: typically N₂ < 4% for sales gas

NRU Configuration

°F
Cryogenic: -220 to -280°F typical

About Nitrogen Rejection

Nitrogen Rejection Units (NRU) remove excess nitrogen from natural gas to meet pipeline specifications and improve heating value. Cryogenic distillation is most common for high-purity applications.

Process Options

  • Cryogenic Distillation: Most efficient, high purity, capital intensive
  • PSA: Lower capital, moderate recovery, operational complexity
  • Membrane: Low capital, bulk removal only, staging required

Typical Performance

  • Feed N₂: 8-25%
  • Product N₂: 1-4%
  • CH₄ Recovery: 90-98%
  • Operating Temp: -220 to -280°F

Design Considerations

  • Cryogenic requires significant refrigeration
  • High methane recovery critical for economics
  • Vent stream disposal or utilization needed
  • Integration with NGL recovery possible
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