Gas Sub-Cooled Process (GSP) Design Calculator
Evaluates the Ortloff GSP cryogenic process for NGL recovery. Calculates turboexpander power, demethanizer reflux requirements, and achievable ethane/propane recovery based on split-vapor flow configuration per GPSA Section 16.
Feed Gas Conditions
MMSCFD
psia
°F
Typical: 600-1200 psia inlet; feed must be dehydrated
Feed Composition
mol%
mol%
Lean gas: 2-5% C2; Rich gas: 6-12% C2
GSP Process Configuration
%
°F
psia
Expander split: 60-75% typical; Subcooler: -80 to -120°F
📚 Learn the Theory
Understand GSP process design, split-vapor reflux, turboexpander operation, and cryogenic NGL recovery optimization
The Gas Sub-Cooled Process (GSP), developed by Ortloff Engineers in the 1970s, is the most widely adopted cryogenic NGL recovery method. It splits cold separator vapor into two streams:
Main stream (60-75%): Expanded through turboexpander for power recovery and cooling
Subcooler stream (25-40%): Cooled by demethanizer overhead, then feeds column top as cold reflux
Typical Performance
Ethane recovery: 85-96% (standard GSP)
Propane recovery: 98-99.5%
Specific power: 20-35 HP/MMSCFD
Expander efficiency: 82-88% isentropic
Design Considerations
Feed must be dehydrated to <0.1 ppmw H₂O to prevent hydrate formation
CO₂ content >2% requires special attention below -70°F (freeze risk)
Higher subcooler split increases recovery but reduces expander power
RSV or CRR process variants achieve >96% ethane recovery