🛢️

Oil Purification Still Calculator

GPSA Ch. 16

Oil Purification Still Calculator
Sizes oil purification (stripping) stills for lean oil absorption plants. The still removes absorbed NGL (C₃+) from demethanized rich oil, regenerating lean oil for recirculation to the absorber. Supports reboiler-only and steam stripping configurations per GPSA Ch. 16.
GPSA Ch. 16 ASME VIII
Calculation Mode:
Design: Size oil purification still from oil flow, NGL loading, and stripping requirements.

Oil Feed

GPM
°F
g/mol

NGL Loading

% (gal NGL/gal oil)

Column Parameters

psig
°F
%
%
in
%

Steam Stripping

lb/gal oil

Typical Oil Purification Still Parameters

ParameterTypical Range
Still Pressure30–75 psig
Reboiler Temperature350–450°F
Theoretical Stages4–12
NGL Retention Target1–3%
Steam Rate0.3–1.0 lb/gal
Oil Loss0.02–0.10%

Engineering Basis

Stripping Efficiency:

ηstrip = (NGLin − NGLout) / NGLin × 100%

Typical stripping efficiency 85–98% depending on stages, temperature, and steam usage. Steam stripping allows lower reboiler temperatures while maintaining high NGL recovery.

Function: The oil purification still strips absorbed NGL (C₃+) from demethanized rich oil, producing lean oil for recirculation to the absorber and NGL product from the overhead.

Design Guidelines

Reboiler Temperature: Keep below 400°F for most oils. Steam stripping allows lower reboiler temperatures (350–380°F) while maintaining high NGL recovery.
Oil Degradation: Monitor oil color, viscosity, and flash point. Dark oil indicates thermal cracking. Makeup oil rate typically 0.02–0.10% of circulation.
Steam Stripping: Improves stripping at lower temperatures. Typical steam rate 0.3–1.0 lb steam per gallon oil. Requires overhead water separation.