Distillation Process Flowsheets & Simulations
Explore 19 validated, solved Distillation simulation flowsheets in MaximaLabs — real components: ethanol, water, n_butane, n_pentane, propane, acetone. Open any one directly in your browser.
Solved via: NRTL, PENG-ROBINSON, NRTL-ASSOCIATE.
Ethanol–water distillation
An 8-stage column concentrating ethanol overhead toward the azeotrope (the headline demo).
4 unit ops • NRTL
231 3
View & openTray 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).
4 unit ops • NRTL
144 0
View & openDistillation column startup dynamics (feed-rate step)
An 8-stage ethanol-water column at a reduced startup feed rate. Solves the steady state normally; switch to the Dynamic solve mode with weir/level-controlled hydraulics enabled and step the feed rate up (e.g. 6 → 9 mol/s) to watch the bottoms draw genuinely rebalance to the new throughput as the tray inventories fill — a feed-rate disturbance no fixed-hydraulics dynamic model (incl. this same column's own default rigorous mode) can show at all. Honest bound: the vapor traffic is held at its steady-state value in this mode, so the distillate draw (condenser-level-controlled off vapor inflow) does not move for a feed-rate-only step — only the liquid/bottoms side responds.
4 unit ops • NRTL
165 0
View & openPerry Ch.13 Example 3: butane/pentane splitter
A simple two-cut distillation splitting butane overhead from pentane bottoms, from Chapter 13 of Perry's Chemical Engineers' Handbook.
4 unit ops • PENG-ROBINSON
232 0
View & openPerry Ch.13 Example 4: sloppy-butane three-cut splitter
A three-cut column with a side draw producing a deliberately 'sloppy' (off-spec, cheaper-to-make) butane cut between a propane overhead and a pentane-plus bottoms, from Chapter 13 of Perry's Chemical Engineers' Handbook.
5 unit ops • PENG-ROBINSON
230 1
View & openAcetone–water distillation
A 12-stage column recovers acetone overhead from a dilute aqueous solvent-recovery feed — a common industrial acetone/solvent-recycling duty.
4 unit ops • NRTL
236 0
View & openAromatics column (Strigle)
A simple aromatics splitter recovering benzene overhead from a toluene/xylene-heavy feed, as described by R. Strigle (Gulf Publishing, 1987) — a classic packed-column textbook design case.
4 unit ops • PENG-ROBINSON
228 1
View & openDepropanizer (Strigle)
A depropanizer recovering propylene and propane overhead from a C₄-and-heavier hydrocarbon feed, as described by R. Strigle (Gulf Publishing, 1987).
4 unit ops • PENG-ROBINSON
230 0
View & openIndustrial i-butane/n-butane splitter
A close-boiling isobutane/n-butane splitter as reported by Klemola and Ilme (Ind. Eng. Chem. Res. 1996, 35, 4579) — the relative volatility between the two isomers is small (~1.3), so the column needs many stages and a high reflux ratio for a sharp split, unlike the wider-boiling LPG splits elsewhere in this library.
4 unit ops • PENG-ROBINSON
230 1
View & openVapor re-compression propane/propylene splitter
Propylene/propane splitters have a notoriously low relative volatility (~1.1-1.15), so they run at high reflux and benefit from heat pumping: the overhead vapor is compressed and used to reboil the same column at a lower operating pressure (here 12 bar vs. a conventional ~20 bar), cutting the compressor shell cost (Christopher et al., Ind. Eng. Chem. Res. 56, 14557, 2017). The reboiler heat-integration loop itself is not modeled here (that would need a recycle-coupled duty match) — this shows the column plus the overhead compression/condensing train, a bounded simplification.
6 unit ops • PENG-ROBINSON
227 0
View & openLPG dividing-wall splitter
Propane / isobutane / n-butane separated in one thermally-coupled dividing-wall column (shortcut splits): three on-spec products from a single shell. From the ChemSep casebook (LPG_DWC, Gas Processing Dec 2018).
5 unit ops • PENG-ROBINSON
229 0
View & openReformate splitter
A single column cutting catalytic reformate into a light benzene/hexane overhead and a toluene/xylene bottoms — the IECR 50, 5680 configuration from the ChemSep casebook.
4 unit ops • PENG-ROBINSON
229 0
View & openBio-ethanol: energy-integrated distillation + MVR stillage concentration
A dilute beer (10% ethanol) is concentrated toward the azeotrope in a beer column, and the water-rich stillage bottoms are concentrated in an evaporator whose vapor is recompressed by a mechanical-vapor-recompression (MVR) compressor — recovering the stillage vapor's latent heat as high-grade heating duty instead of venting it, the energy-integration route that eliminates a separate thermal oxidizer.
9 unit ops • NRTL
230 0
View & openAcetic acid recovery — NRTL with vapor-phase dimerization
Concentrating dilute aqueous acetic acid (30 mol%) by distillation, modeled with the NRTL activity package and chemical-theory vapor-phase association (acetic acid dimerizes, 2 A → A2, in the vapor). This is the physics a cubic equation of state gets wrong: the pinned NRTL acetic-acid/water binary (DECHEMA) plus the cited dimerization constants (Nagy et al., Molecules 2020) give the real bubble curve and latent heat, so the close-boiling acid/water pair actually separates and converges where Peng-Robinson does not.
4 unit ops • NRTL-ASSOCIATE
228 0
View & openRate-based distillation (Maxwell-Stefan, ChemSep-style)
A depentanizer split (n-pentane overhead from an n-pentane/n-hexane/n-heptane feed) solved with a rigorous rate-based (nonequilibrium) stage model rather than the usual equilibrium-stage assumption. Every stage carries separate bulk vapor and liquid compositions with a vapor-liquid interface in equilibrium and finite Maxwell-Stefan mass-transfer fluxes across each film, and the per-stage transfer coefficients come from the real Chan-Fair (1984) tray-efficiency correlations off estimated tray geometry — the exact physics ChemSep and Aspen RateSep are built on. The result: real trays lag equilibrium, so the finite-transfer distillate is measurably less pure (~98.7% C₅) than an equilibrium-stage model predicts (~99.8%) on the identical column — roughly 5x more hexane slips overhead. Open the equivalent equilibrium column ('ethanol-water-distillation' or any 'distillation' node) to see the gap the equilibrium-stage assumption hides. As the mass-transfer coefficients grow the model collapses back onto the equilibrium column (the built-in validation limit).
4 unit ops • PENG-ROBINSON
239 0
View & openDepropanizer (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).
4 unit ops • PENG-ROBINSON
189 1
View & openNGL 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.
6 unit ops • PENG-ROBINSON
190 0
View & openShortcut column sizing (Fenske-Underwood-Gilliland)
Before anyone builds a rigorous column they size it in about a second, and this is that step — Aspen's DSTWU, the calculation every distillation design starts from. State the two keys and how well you want them separated, and the shortcut answers the four questions that set the capital cost. For a depropaniser feed (30% propane, 40% n-butane, 30% n-pentane) at 10 bar recovering 98% of the propane overhead and 98% of the n-butane in the bottoms: Fenske gives 8.34 minimum stages — the count at total reflux, where you spend infinite energy to buy the fewest trays. Underwood gives a minimum reflux of 1.54 — the reflux at infinite stages, the opposite corner. Neither is buildable; the real column lives between them, and Gilliland interpolates: at 1.3x the minimum reflux you need 17.7 theoretical stages, with Kirkbride putting the feed on stage 7.85. That is a little over twice the minimum stage count for 1.3 times the minimum reflux, which is the trade every column is designed on. The energy follows: 1.67 MW reboiler against a 1.35 MW condenser. Bounded, and this is the important part. These are screening numbers, not a design. The shortcut assumes constant relative volatility and constant molal overflow — it cannot see a pinch, a tangent, an azeotrope, or a temperature profile. Its job is to give a rigorous MESH column a starting point that converges, not to replace it. Run the distillation unit op on 18 stages with a feed at 8 to check it.
4 unit ops • PENG-ROBINSON
71 0
View & openTray efficiency: 20 real trays are not 20 stages
Every equilibrium column model quietly assumes each tray reaches equilibrium. Real trays do not, and the gap is not small enough to ignore when you are buying a shell. The same depropaniser is solved twice at 20 trays, a 2.5 reflux ratio and a 50/50 split. As 20 equilibrium stages it puts 99.61% propane overhead. As 20 actual trays on the rate-based model it manages 96.63% — the tower is the same height and the separation is measurably worse, because the model applies an efficiency instead of assuming one. Left to itself it derives that efficiency from the feed's relative volatility and liquid viscosity through the O'Connell correlation; give it a stage_efficiency and it uses yours, and at a punishing Murphree 0.5 the overhead drops further to 95.33%. The practical reading: an equilibrium model sized this column at 20 trays and the tray efficiency spent roughly three points of product purity. Size on equilibrium stages and you will under-build the tower — that is what the efficiency is for. Bounded: this applies a single overall efficiency to every tray, which is a screening treatment. It is not a rigorous rate-based column — for genuine two-film Maxwell-Stefan transfer with per-stage interface composition and energy coupling, use nonequilibrium_distillation instead. O'Connell itself is a correlation fitted to commercial tray data, so it carries that scatter.
4 unit ops • PENG-ROBINSON
75 0
View & open