Which thermodynamic method does it use?

The PENG-ROBINSON property package, over ethane, propane, n_butane, n_pentane — already selected. You can switch the method on the canvas before running.

Which unit operations are in the flowsheet?

It chains Deprop. Every block is a real, solvable unit operation you can reconfigure, add to, or remove.

Do I need to install software or buy a license?

No. Depropanizer (NGL fractionation) runs entirely in your browser on MaximaLabs — free, no install, no license. Open the model to load it live and run the deterministic solver.

All guides

Gas processing (NGL fractionation train)

How to simulate depropanizer (ngl fractionation)

The raw NGL recovered by a cold separator is fractionated: a depropanizer column splits it into a C₃-and-lighter overhead (propane + a little ethane, the LPG product) and a C4+ bottoms (butanes + natural gasoline). The column is solved with the component-flow Naphtali-Sandholm MESH (method "ns"), which carries every component flow as an unknown so the feed-vs-products material balance is an equation the solver closes by construction — the right tool for a sharp C₃/C₄ cut, where a reduced-form column would drag the split off and leak a few percent of a component. Peng-Robinson handles the light-hydrocarbon VLE; the built-in sensitivity sweeps the reflux ratio against the reboiler duty (the classic distillation energy trade-off).

NGL

feed

dist

btms

Deprop

C3prod

C4plus

1
Open the ready-made model
Open the "Depropanizer (NGL fractionation)" model in the MaximaLabs workspace — no install, no license. It loads live on the canvas, ready to edit and run.
2
Confirm the thermodynamics
This process is modeled with the PENG-ROBINSON property package over ethane, propane, n_butane, n_pentane — already selected, so the phase equilibrium and enthalpy are physically consistent from the first run.
3
Review the flowsheet
The flowsheet chains Deprop. Every block is a real, solvable unit op you can reconfigure on the canvas.
4
Run the simulation
Click Run. The deterministic solver converges the material and energy balances (recycles included) and fills the live stream table — the AI never invents a number.
5
Read the results and iterate
Inspect the converged streams, tweak a spec, and re-run — or ask the AI copilot to explain a result or diagnose a failed solve in plain English.

What you'll build

Thermodynamics: PENG-ROBINSON
Components: ethane, propane, n_butane, n_pentane
Unit operations: Deprop

Open this model in the workspace

Opens live on the canvas — free, no install.

Explore the model & flowsheet

Frequently asked questions

What does the Depropanizer (NGL fractionation) model simulate?: The raw NGL recovered by a cold separator is fractionated: a depropanizer column splits it into a C₃-and-lighter overhead (propane + a little ethane, the LPG product) and a C4+ bottoms (butanes + natural gasoline). The column is solved with the component-flow Naphtali-Sandholm MESH (method "ns"), which carries every component flow as an unknown so the feed-vs-products material balance is an equation the solver closes by construction — the right tool for a sharp C₃/C₄ cut, where a reduced-form column would drag the split off and leak a few percent of a component. Peng-Robinson handles the light-hydrocarbon VLE; the built-in sensitivity sweeps the reflux ratio against the reboiler duty (the classic distillation energy trade-off).
Which thermodynamic method does it use?: The PENG-ROBINSON property package, over ethane, propane, n_butane, n_pentane — already selected. You can switch the method on the canvas before running.
Which unit operations are in the flowsheet?: It chains Deprop. Every block is a real, solvable unit operation you can reconfigure, add to, or remove.
Do I need to install software or buy a license?: No. Depropanizer (NGL fractionation) runs entirely in your browser on MaximaLabs — free, no install, no license. Open the model to load it live and run the deterministic solver.

More guides like this

Gas processing (NGL fractionation train)

NGL fractionation train (depropanizer + debutanizer)

The full two-column NGL fractionation train of a gas plant: a raw NGL is split into three products. The depropanizer takes a propane-and-lighter overhead (the propane product), and its C4+ bottoms feed a debutanizer that splits butane overhead from a natural-gasoline (C5+) bottoms. Both columns use the component-flow Naphtali-Sandholm MESH (method "ns") so each sharp cut conserves every component exactly; the two columns solve in sequence (no recycle) and the whole train closes on mass. Peng-Robinson handles light-hydrocarbon VLE; the debutanizer runs at a lower pressure (7 bar vs 18) so its reboiler stays within a reasonable temperature.

Gas plant, Permian Basin, Texas, USA

Natural gas fractionation train

A four-column NGL fractionation train — demethanizer, deethanizer, depropanizer, debutanizer — recovering pipeline-spec sales gas plus ethane, propane, and butane products from wellhead-pressure raw natural gas, after Luyben (Ind. Eng. Chem. Res. 2013, 52, 10741).

Mont Belvieu NGL fractionation complex, Texas, USA

NGL fractionation: single-shell Petlyuk dividing-wall column

A natural-gas-liquids cut (ethane / propane / n-butane) split into three on-spec products by ONE thermally-coupled dividing-wall column instead of two columns in series. This uses the native Petlyuk unit op: a prefractionator whose reflux and boilup are supplied by the main column (the single condenser + single reboiler), solved by an outer Wegstein loop that converges the bidirectional vapor/liquid coupling to self-consistency — the coupling legacy sequential-modular solvers approximate with two connected columns whose recycle fails to converge.

Pekin, Illinois, USA

Ethanol–water distillation

An 8-stage column concentrating ethanol overhead toward the azeotrope (the headline demo).

Tray efficiency — real trays vs ideal stages

The same ethanol–water column solved with a Murphree vapor tray efficiency of 0.7 instead of ideal equilibrium stages. A real sieve/valve tray never reaches full vapor-liquid equilibrium — the vapor leaving it only partly approaches the equilibrium composition with the tray liquid, mixing in un-equilibrated vapor from the tray below: y = E·K·x + (1−E)·y_below (Murphree 1925). At E = 0.7 each of these 12 trays does 70% of an ideal stage's work, so the overhead ethanol is lower than an equilibrium column of the same tray count would predict — which is exactly why a real column needs more trays than a shortcut (ideal-stage) calculation says. Both HYSYS and Aspen RadFrac expose this per-tray efficiency; set murphree_efficiency back to 1.0 to recover the ideal-stage column. The efficiency auto-selects the component-flow Naphtali-Sandholm solver (the reduced-form solvers carry no explicit per-tray VLE row to apply an efficiency to).

Reference model

Gas compressor air-cooled aftercooler (fin-fan)

A natural-gas booster compressor followed by an air-cooled (fin-fan) aftercooler — the standard way to reject compression heat where no cooling water is available. The compressor raises the gas from 8 to 24 atm (hot discharge ~150 °C); the air cooler then rejects that heat to ambient air, cooling the gas back to 49 °C. Unlike a plain cooler, the air_cooler op closes the air side: from the process duty and the 35 °C design ambient it solves the air mass flow (a 15 °C air rise) and reports the fan power from the given fan static pressure. Honest scope: screening air-side model (fixed cp_air, ideal-gas air density, no fin/row geometry rating); an air cooler cannot cool below ambient, so the 49 °C target sits safely above the 35 °C air inlet.