GPSA Ch. 16 / Cryogenic Processing
| Parameter | Range |
|---|---|
| Demethanizer Pressure | 350–450 psig |
| Expander Outlet Temp | −130 to −150°F |
| C₂ Recovery (GSP) | 85–95% |
| C₂ Recovery (Conv.) | 40–60% |
| Expander Efficiency | 78–87% |
Turboexpander Isentropic Work:
Where m = mass flow rate, hin = inlet enthalpy, hout,s = isentropic outlet enthalpy, ηexp = expander isentropic efficiency.
C₂ Recovery Efficiency:
Recovery efficiency depends on process configuration: CRR > ISS > GSP > Conventional JT.
Gas Subcooled Process (GSP): Splits the chilled gas into two streams — one feeds the demethanizer top as reflux (subcooled liquid), the other is expanded through the turboexpander. This configuration achieves 85–95% ethane recovery.
Demethanizer Sizing: Column diameter sized from vapor/liquid traffic. Number of theoretical stages determined by required separation sharpness between C₁ and C₂.
Understand cryogenic ethane recovery processes, turboexpander design, and demethanizer operation
The calculator evaluates GSP (gas subcooled process), CRR (cold residue recycle), ISS (internal stripping sequence), and conventional JT expansion configurations for cryogenic ethane recovery per GPSA Ch. 16.
Modern turboexpander-based cryogenic plants achieve ethane recovery efficiencies of 85ā95%+ depending on the process configuration. GSP and CRR processes offer the highest Cā recovery at equivalent power consumption.
The demethanizer column diameter is determined from the vapor and liquid traffic at the design flood fraction. The calculator uses feed composition, expander outlet conditions, and GPSA Ch. 16 methods for column sizing.
The turboexpander provides isentropic cooling by expanding high-pressure feed gas, generating cryogenic temperatures needed for ethane condensation. Recovered shaft power drives the residue gas recompressor, improving plant efficiency.