GPSA Ch. 16 ASME Section VIII GPA 2140

Calculation Mode:

Design Rate

Design: Size deethanizer from feed composition and product specifications.

Feed Conditions

NGL Feed Rate

BPD

Feed Temperature

°F

Column Pressure

psig

Feed Composition (mol%)

Methane (C₁) Lighter than light key

Ethane (C₂) — Light Key

Propane (C₃) — Heavy Key

iso-Butane (iC₄)

n-Butane (nC₄)

Pentane+ (C₅+)

Product Specifications

Max C₂ in Bottoms

mol%

Max C₃ in Overhead

mol%

Condenser Type

Column Design Parameters

Reflux Ratio Multiplier (R/R_min)

Overall Tray Efficiency

Tray Spacing

Design Flood Fraction

Typical Deethanizer Operating Conditions

Parameter	Range
Pressure	350–500 psig
Overhead Temp	−20 to 20°F
Bottoms Temp	150–250°F
Reflux Ratio	1.0–3.0
Trays	25–40

Engineering Basis

Fenske Equation (Minimum Stages):

N_min = ln[(x_LK,D / x_HK,D)(x_HK,B / x_LK,B)] / ln(α)

Where x_LK,D = light key mole fraction in distillate, x_HK,B = heavy key mole fraction in bottoms, α = average relative volatility of light key to heavy key.

Gilliland Correlation:

(N − N_min) / (N + 1) = f[(R − R_min) / (R + 1)]

Correlates actual stages N to actual reflux ratio R given minimum stages N_min and minimum reflux R_min from the Underwood equation.

Underwood Equation: Determines minimum reflux ratio R_min from feed composition, feed condition (q), and relative volatilities. Combined with Gilliland correlation to find actual stages at the design reflux multiplier.

Column Diameter: Sized from vapor/liquid traffic using Fair’s flooding correlation at the design flood fraction.

📚 Learn the Theory

Understand deethanizer design, NGL fractionation principles, and shortcut distillation methods

Read Engineering Guide →

Results

Actual Trays

trays

N_min (Fenske) -

R_min (Underwood) -

R_actual -

N_theoretical -

Feed Tray -

Rectifying / Stripping -

Column Dimensions

Diameter -

Height -

Tray Spacing -

% Flood -

Shell Thickness -

Weight -

Duties & Utilities

Condenser Duty -

Reboiler Duty -

CW Flow -

T_condenser -

T_reboiler -

Design Guidelines

Operating Pressure: Deethanizers typically operate at 350–500 psig to condense overhead C₂ with available refrigeration.

Ethane Specification: Ethane specification in bottoms (<2 mol%) prevents vapor pressure issues in downstream products.

Condenser Type: Partial condensers produce vapor overhead; total condensers produce liquid for further fractionation.

Deethanizer (DeC2) Sizing Calculator