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Turbo-Expander Calculator

API 617 / GPSA Standards

Turboexpander Performance Calculator
Calculates turboexpander performance per GPSA Section 13 and API 617: power recovery, outlet temperature, and refrigeration duty. Compares expander vs. JT valve cooling for NGL recovery plant design.

Process Conditions

MMscfd
psia
psia
°F

Gas Properties

Air=1
-

Expander Performance

%
%
%

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About This Calculator

Calculates turboexpander performance for NGL recovery and energy recovery per GPSA Section 13 and API 617.

Key Features:

  • Power Output: Shaft and generator power (kW/HP)
  • Temperature: Polytropic outlet vs. isentropic ideal
  • JT Comparison: Expander benefit over throttling valve
  • Real Gas: Z-factor correction (DAK correlation)

Typical Applications:

  • NGL recovery plants (C2+ extraction)
  • Cryogenic gas processing
  • Pressure letdown with power recovery
  • LNG mixed refrigerant cycles

Design Guidelines:

  • Expansion ratio: 2.5:1 to 4:1 per stage
  • Polytropic efficiency: 80-88% typical
  • Mechanical efficiency: 97-99%

Frequently Asked Questions

What is a turboexpander used for in gas processing?

Turboexpanders recover power while cooling gas streams for NGL recovery, providing deeper cooling than JT valves for higher liquid recovery.

What standards does this turboexpander calculator follow?

This calculator follows GPSA and API 617 standards for turboexpander performance calculations.

How does a turboexpander compare to a JT valve?

A turboexpander achieves lower outlet temperatures and recovers shaft power, resulting in higher NGL recovery compared to a JT (Joule-Thomson) valve.

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