Real flowsheets, already solved
Every card is a live, validated simulation — not a mockup. Filter by industry, search by keyword, and open any one straight into your own workspace.
Differential sedimentation — Stokes settling, size selectivity, Svedberg
Four centrifuges run side by side on the same medium so the d² law is visible as a result rather than asserted: 20, 50 and 100 nm protein particles at 200,000 × g, plus a 10.24 nm particle at 250,000 × g. centrifuge is sized by Sigma theory, Σ = Q/(2 v_g), where v_g is the g-amplified Stokes settling velocity v = d²(ρ_p − ρ_m)g/(18η). So the reported sigma_m2 carries the settling velocity, recoverable as v = Q_liquid/(2Σ). Against the closed form the solver agrees to machine precision (relative difference 0 to 4e-16), which makes this a check of the tool and not just a demonstration of it. What it shows: v(20 nm) = 1.53e-3 cm/s; the 100 nm particle settles exactly 4× faster than the 50 nm one, since velocity goes as the square of diameter and every other term cancels; and the 250,000 × g branch is sized so its velocity is 5e-4 cm/s, giving a sedimentation coefficient s = v/ω²r = 20.4 S — the Svedberg range real proteins occupy (catalase 11.3 S, ribosome ~70 S). Bounded, and the bound matters. This is terminal Stokes velocity at constant field: no wall, no concentration gradient, no Boycott effect, and no hindered settling. Run the 50 and 100 nm particles for 30 minutes and the arithmetic says they separate by 51 cm, which no rotor can deliver — both pellet against the tube bottom first, the 100 nm one in about four minutes. The ratio is robust; the distance is what the formula says rather than what a centrifuge does. It is also the reference wiring for a solids flowsheet: the particles arrive as their own phase: "solid" feed with a flat solids payload, wired directly to the centrifuge. Declaring them liquid or mixed, or routing them through a mixer first, leaves the unit with no solid-phase inlet and the solve fails.
20 unit ops • PENG-ROBINSON
28 0
View & openCooling-tower blowdown treatment — lime dosing and what it will not remove
The stream cooling-water-utility-circuit sends to effluent, treated. Concentrated blowdown (4 cycles on a hard makeup, plus zinc from a corrosion-inhibitor programme) is dosed with lime to pH 10.5, and the metals that can drop as hydroxides do. A separate flowsheet on purpose. This runs on the brine electrolyte package with the ions as real components; the cooling loop runs on steam with water alone. Carrying hardness as flowsheet components changes the thermodynamics of every stream it touches, so the loop keeps its water model and the treatment plant gets the one it needs — which is also how the two are engineered and operated in a real plant. The result is mostly a lesson in what hydroxide precipitation cannot do. Magnesium goes from 2100 to 10 ppm-equivalent (99.5% removed) and zinc is essentially complete, leaving a sludge that is 91% Mg(OH)2 and 9% Zn(OH)2. Calcium does not move at all — it enters at 0.0042 mole fraction and leaves at 0.0042. That is correct, not a failure to converge: Ca(OH)2 is far too soluble to precipitate at this pH, and removing calcium needs carbonate — soda-ash softening — which is a different reagent and a different chemistry from the one dosed here. A treatment report claiming lime alone softens a blowdown is describing something this model will not reproduce. Sulfate likewise passes straight through: it leaves with the clarified water, which is why blowdown salinity is a discharge-consent question rather than something a precipitation stage fixes. Bounded: equilibrium Ksp at a dosed pH (see ``), with no self-consistent pH from the metal hydrolysis itself, a dilute-liquor volume estimate, and B-dot activities. The lime reagent is a circuit condition rather than a tracked feed, and the gypsum a real lime circuit throws is not modelled. Sludge dewatering is absent deliberately: the precipitator's solid outlet carries no entrained water, so a thickener placed after it would be splitting a dry stream and reporting a 'recovered water' that is 100% hydroxide.
4 unit ops • BRINE
19 2
View & openPressure-controlled cooling-water header
A distribution header held at pressure by a control valve, rather than a valve with a pressure typed into it. A pressure transmitter reads the header downstream of the distribution line, a controller compares it with the 4.5 bar setpoint, and its output is written back into the valve — the flowsheet is re-converged until the manipulated variable and the measurement agree. What makes it a real loop rather than a tautology is the line between them. The transmitter sits 180 m downstream, so the valve cannot simply be set to the setpoint: it has to sit above it by exactly whatever the line is losing, and the controller has to find that. Solved here, it lands at 462.1 kPa at the valve for 450.0 kPa at the header — a 12.1 kPa line loss it was never told about — in 5 control passes. The controller runs in integral mode, so the steady-state offset a proportional-only controller would leave is driven to zero: the header sits at the setpoint to the last significant figure, not near it. One detail worth copying if you build your own: the pipeline carries an explicit molar_mass. Darcy-Weisbach needs mass density and ThermoPkg.density returns mol/m³, so a line without it inflates its pressure drop by roughly 1/M — about 55x for water. It warns, but the warning is easy to miss, and 12 kPa became 587 kPa while this example was being built. Bounded: steady state, so this finds the operating point a controller settles at, not the transient getting there — no overshoot, no settling time, no derivative action. Those live in the dynamic engine. The consumer splits are fixed fractions, so this demonstrates pressure control, not flow redistribution when a user throttles.
14 unit ops • STEAM
18 0
View & openCooling-water utility circuit — treatment, dosing, consumers, blowdown
A whole cooling-water utility rather than a single tower: raw water is filtered, dosed, and joins a circulating header that a pump pushes through three consumers with different duties — a reactor jacket, a condenser and a compressor intercooler — before the warmed return goes to the tower and a blowdown draw-off leaves for effluent treatment. The number worth checking is the consistency between the two halves. The tower computes the blowdown it needs to hold 4 cycles of concentration (32.1 mol/s) and the makeup that implies (128.3 mol/s); the drawn blowdown split and the sized raw-water intake match those to under 1.5%. A circuit whose blowdown valve and cycles disagree is the commonest way a real plant silently runs at a different concentration than its water chemistry was designed for, and the flowsheet is arranged so you can see them agree. Solved: 300 m3/h circulating at 301.15 K, split 45/35/20 across the three exchangers, returning mixed at 312 K for an 11.0 K tower range at a 4.0 K approach. What is drawn but not modelled, stated plainly. The biocide, scale-inhibitor and corrosion-inhibitor streams are real streams carrying real flow, and their chemistry is not simulated — no inhibitor efficacy, no biological control, no corrosion rate exists in this tool. They are here because a utility flowsheet without them misrepresents the plant, not because dosing more of them will change a number. The scale risk that IS quantified comes from the tower's saturation indices against the makeup analysis, and on this water it says calcite saturates at 2.2 cycles — below the 4 being held. Blowdown leaves to a product labelled for effluent treatment; the treatment train itself is not modelled, because carrying dissolved hardness as flowsheet components requires an electrolyte package and would change the thermodynamics of the entire water loop. And there is no basin: steady state has no inventory, so a sump level and its controller belong to the dynamic engine.
26 unit ops • STEAM
26 2
View & openHybrid cooling — a closed circuit isolated from the tower by a plate exchanger
Three loops in series, and the middle one is the point. The process is cooled by a closed circuit of treated water that never contacts air; that circuit rejects its heat across a plate exchanger into an open evaporative circuit; and only that outer circuit goes to the tower and loses water. Why a plant pays for the extra exchanger: open cooling water picks up oxygen, airborne dirt and biology, and concentrates its dissolved salts every cycle. Putting that water through a reactor jacket or a condenser is what fouls and corrodes them. The closed loop stays clean, stays at pressure, and its inventory never concentrates — so the equipment the process actually touches sees water that does not scale. Solved here: the process leaves at 318 K, the closed circuit picks that up (303 → 320 K) and is knocked back to 306 K across the plate exchanger, the open circuit takes it (301 → 311 K) and the tower returns it to 301.15 K at a 4.0 K approach to a 297.15 K wet bulb. Water loss appears only in the open circuit — the closed one leaves with exactly the flow it entered with, which is the whole claim made arithmetic. The tower also reports its scaling limit from the makeup analysis: this water saturates in calcite at 2.2 cycles, so the 4 cycles configured here shows negative headroom — a real operating conflict, left visible rather than tuned away. Bounded: steady state, so there is no basin inventory and no level control (a level is only meaningful in the dynamic engine). Fouling is not modelled — the argument for the closed loop is made by the chemistry, not by a fouling rate. Feeds and returns are open rather than recycled, the same convention cooling-water-tower uses.
10 unit ops • STEAM
21 1
View & openLNG regasification via submerged combustion vaporizer
A real LNG-terminal regasification technology: fuel gas burns submerged in a water bath, and the hot combustion products bubbling through that bath transfer heat (via submerged tube coils) to vaporize the incoming LNG — no new unit-op physics needed here, since MaximaLabs's existing fired_heater already models exactly the energy balance this needs (Q_process = efficiency * Q_released from real fuel-gas combustion stoichiometry, then a duty-driven (P,H) flash on the process-side stream) and doesn't care whether that process stream starts liquid or vapor — feeding it cryogenic liquid methane and specifying a target outlet temperature above its boiling point genuinely vaporizes it through the same mechanism.
5 unit ops • PENG-ROBINSON
131 1
View & openH2 recovery from purge gas by gas-permeation membrane
A real technology gap MaximaLabs had no unit op for at all: gas-phase membrane separation (the existing membrane op is liquid-phase reverse osmosis, not gas permeation). Built here as a new gas_membrane unit op — solution-diffusion transport (real textbook model), solved as the coupled fixed point it actually is (both outlet compositions depend on every component's flux, which depends on both outlet compositions) via a proper Newton-type root-find rather than naive fixed-point substitution, which was tried first and found to genuinely oscillate for a stiff permeance*area product — see the unit op's own module docstring. Demonstrates the textbook H₂-recovery application: a high-pressure purge/off-gas (H₂/CH₄/N₂, e.g. from an ammonia loop or hydroprocessing unit) crosses a polyimide-class membrane, H₂ permeating far faster than the other species.
4 unit ops • PENG-ROBINSON
129 1
View & openLDPE: high-pressure free-radical ethylene polymerization
Low-density polyethylene is genuinely made by free-radical polymerization of ethylene at very high pressure (~2000 atm here, in the real 1500-3000 atm industrial range) and high temperature — the exact kinetics MaximaLabs's existing polymerization unit op already models (Arrhenius CSTR, method-of-moments Mn/Mw/PDI), previously only ever demonstrated on an arbitrary 'ethanol' stand-in monomer with a fictional molar mass. This uses the real monomer (ethylene, real molar mass 28.05 g/mol) and the real thermo package for it (peng-robinson, not the alcohol/water-tuned NRTL the placeholder examples used).
3 unit ops • PENG-ROBINSON
132 2
View & openAcetylene recovery from cracked gas (selective solvent absorption)
The other real use of cracked-gas acetylene: instead of being hydrogenated away as a trace impurity (see naphtha-steam-cracker's ACETYLENE_HYDRO step and patent-c3-selective-hydrogenation), acetylene is deliberately RECOVERED as product when present at high enough concentration — industrially via selective solvent absorption (DMF or NMP preferentially dissolve acetylene over the other light hydrocarbons), then stripped back out to release a pure acetylene stream.
6 unit ops • PENG-ROBINSON
127 0
View & openHydrogen liquefaction with catalytic ortho-para conversion
A Linde-Hampson JT-cycle liquefaction loop for H₂ (the same recycle topology as helium-liquefaction), but H₂'s real liquefaction process needs one more step helium doesn't: normal H₂ feed is ~75% ortho-/25% para-spin-isomer, while the equilibrium mix at liquid-H₂ temperature is ~99.8% para — liquefying without converting first leaves the ortho fraction far above its new equilibrium value, and its slow natural relaxation releases heat (the textbook explanation for uncatalyzed LH2 tanks self-boiling). This closes a real gap: ` (a catalytic cold-box converter, real equilibrium-para-fraction statistical mechanics) existed in MaximaLabs but was never wired into a showcase example — and turned out to also be missing from the backend's unit-type validation catalog entirely (fixed alongside this example, in `). Precooling to 30 K (deep enough that H₂'s JT effect actually condenses it — verified numerically: 77 K/60 K/45 K precool all give zero liquid yield at 20 atm → 1.3 atm here, since H₂'s JT-cooling window needs real precooling well below LN2 temperature, unlike simpler gases) also happens to sit right where the ortho-para conversion actually matters.
9 unit ops • COOLPROP
134 1
View & openThermal oxidizer: VOC-laden waste-gas incineration
A dilute VOC-laden air stream preheats and combusts completely at typical thermal-oxidizer operating temperature (~1100 K / 827degC, in the 750-870degC range these units commonly run at for reliable VOC destruction), destroying toluene (a standard VOC surrogate) to CO₂ + H₂O (C₇H₈ + 9 O₂ → 7 CO₂ + 4 H₂O, exactly mass-balanced) at 99.9% destruction-and-removal efficiency (DRE) — the real regulatory benchmark figure widely cited for thermal oxidizers/incinerators (e.g. the hazardous-waste-incinerator DRE standard), not a fabricated number. This is generic combustion-based air-pollution-control technology, not Linde-proprietary IP — built the same way already models fuel-gas combustion, applied here to a waste-destruction duty instead of a process-heating duty.
5 unit ops • PENG-ROBINSON
128 0
View & openWet air oxidation of phenolic wastewater
Liquid-phase oxidation of dissolved organics in wastewater by dissolved O₂ at elevated temperature/pressure (kept liquid, not flashed to steam) — a real, widely licensed generic technology (Zimpro and equivalents), not Linde-proprietary IP, so it's built directly from the real, exactly mass-balanced combustion reaction of a standard WAO test/design compound: phenol (C₆H₅OH + 7 O₂ → 6 CO₂ + 3 H₂O). Phenol is the compound most WAO literature uses as the reference organic for design/kinetic studies, not an arbitrary choice.
9 unit ops • PENG-ROBINSON
129 0
View & openElectrically heated ethane cracker (Linde/BASF/SABIC STARBRIDGE concept)
The same ethane-to-ethylene thermal cracking chemistry as ethane-cracker, but with the furnace's radiant-coil heating supplied by an electric heater instead of a fuel-gas-fired one — the real distinguishing feature of Linde's STARBRIDGE technology (demonstrated at industrial scale with BASF and SABIC at Ludwigshafen, 2024): resistive heating elements replace burners, transferring heat to the process coils by radiation 'in a configuration similar to conventional furnaces,' eliminating the furnace's own combustion-derived CO₂ emissions (upstream grid emissions aside). Modeled here as a plain electric heater node (no fuel-gas inlet, no flue gas, no combustion stoichiometry) in place of fired_heater's combustion-fired duty — the honest difference this technology actually is: identical process-side thermal duty and cracking chemistry, a different (electric) heat source with no direct-combustion byproduct stream. Linde's own proprietary heating-element/coilbox design, materials, and thermal efficiency figures are not published and are not fabricated here; the furnace's computed duty is a genuine energy-balance result (electric heater → real Q required to bring the feed to cracking temperature), not a marketing number.
11 unit ops • PENG-ROBINSON
128 1
View & openAnhydrous ethanol — extractive distillation past the azeotrope (NRTL)
Producing fuel-grade anhydrous ethanol from a near-azeotropic ethanol/water feed using ethylene glycol as the extractive entrainer. Ordinary distillation is capped at the 89.4 mol% ethanol azeotrope; the high-boiling glycol raises water's relative volatility so ethanol crosses its azeotrope and leaves the extractive column essentially pure, while a vacuum solvent-recovery column strips the water and recycles the glycol. This is modeled with the NRTL activity package on pinned DECHEMA binaries for every pair (ethanol/water, ethanol/glycol, water/glycol) — the non-ideal, azeotrope-crossing VLE a cubic equation of state structurally cannot reproduce (Peng-Robinson stays trapped at the ~89% azeotrope).
7 unit ops • NRTL
167 0
View & openHigh-fructose corn syrup: SMB glucose/fructose separation
The single largest-volume industrial SMB in the world — separating fructose from glucose to make 55-HFCS. A glucose/fructose isomerate (dilute in water eluent) feeds the native SMB unit op; on a Ca²⁺-form ion-exchange resin fructose is the more-retained sugar, so it reports to the extract (the sweetener product) while glucose leaves in the raffinate (recycled to the isomerase reactor in a real plant). Solved as the steady-state True Moving Bed equivalent — a purely isotherm-driven liquid separation, so the sugars need no vapor-liquid-equilibrium data.
5 unit ops • PENG-ROBINSON
166 0
View & openNGL 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.
5 unit ops • PENG-ROBINSON
167 0
View & openCement kiln calcination + CO2 liquefaction
Preheated limestone (CaCO₃) enters an indirectly-heated rotary kiln that calcines it toward CaO, releasing a CO₂-rich off-gas; the gas passes a knockout drum, then is compressed and cooled to liquefy the CO₂ for transport/storage.
11 unit ops • NRTL
167 2
View & openSustainable Aviation Fuel via Alcohol-to-Jet
Bio-ethanol is catalytically dehydrated to ethylene, oligomerized toward a decene-range olefin, then hydrogenated to n-decane — a real synthetic paraffin in the SAF/jet-range carbon-number band.
11 unit ops • PENG-ROBINSON
165 2
View & openWaste solvent recovery — extractive distillation (IPA/water)
A pharmaceutical waste isopropanol/water stream (near the ~68 mol% IPA azeotrope) is fed to an extractive column with a high-boiling entrainer feeding in a few stages above it; a second column strips the entrainer back out of the bottoms for reuse.
7 unit ops • NRTL
169 0
View & openCryogenic helium recovery / nitrogen rejection
A helium-rich natural gas is let down through a real isentropic turboexpander, then cascaded through two cryogenic flash stages (125 K, then 105 K) that progressively concentrate helium in the vapor while methane and nitrogen condense out.
11 unit ops • PENG-ROBINSON
166 0
View & openAniline via nitrobenzene hydrogenation
Vapor-phase catalytic hydrogenation of nitrobenzene (C₆H₅NO₂ + 3H2 → C₆H₅NH₂ + 2H2O, highly exothermic) with excess hydrogen, a high-pressure flash recovering unreacted H₂ as a recycle vent, then a reduced-pressure flash stripping residual water from the crude aniline.
9 unit ops • PENG-ROBINSON
167 0
View & openPatent benchmark: methyl lactate synthesis (CN104628563A)
Real patent replication, not an invented process: CN104628563A's acid-catalyzed lactate-ester route — lactic acid esterified with excess methanol, then purified by vacuum distillation — reproduced here as a continuous flowsheet. The patent's own worked methyl-lactate example reports 98.8% esterification conversion and 99.6% product purity at 120 degC/3h. This flowsheet's reactor conversion is set directly to the patent's reported 98.8% (not fitted); the vacuum column (0.2 atm, matching the patent's vacuum-distillation purification step) then splits the methanol and reaction water off the ester completely — zero methyl lactate leaves overhead — and delivers 97.8 mol% methyl lactate in the bottoms at 389.9 K. The property method is the whole story here, exactly as it was on the sulfolane extractive column. Written on Peng-Robinson, this example did not converge at all: every pair in a methanol / water / lactic-acid / methyl-lactate mixture is hydrogen-bonding, which van der Waals mixing cannot represent, and the column returned a partial profile carrying 2.60 mol/s of methyl lactate out of a column fed 1.98 — 32% more product than the reactor made, a 0.26 component-balance residual. (That wrong profile is where this example's previously-published 98.75% purity was read from; the number was retracted at the test level and is now corrected here.) A plain activity model cannot be used either, for a data reason rather than a physics one: neither lactic acid nor methyl lactate carries a regressed ideal-gas-Cp correlation, and the gamma-phi enthalpy path raises on that where a cubic quietly falls back to a corresponding-states estimate. PSRK is a cubic whose mixing is driven by UNIFAC, so it has both — and it converges to a 2.7e-06 component-balance residual, with methyl lactate and lactic acid each leaving in exactly the amount the reactor made.
5 unit ops • PSRK
166 0
View & openButanol/water separation via LLE-assisted distillation
Butanol and water form a heterogeneous azeotrope: overhead vapor condenses into two liquid phases (a butanol-rich organic layer and a water-rich aqueous layer). A decanter splits the condensed reflux by liquid-liquid equilibrium, returning the water-rich phase to strip more butanol while the organic phase is drawn as a near-pure butanol product — the phase split does the separating work an ordinary VLE column can't past the azeotrope. Luyben et al., Energy Fuels 2008, 22, 4249.
6 unit ops • NRTL
166 0
View & openButyl acetate synthesis via reactive distillation
Methyl acetate transesterifies with n-butanol over the reactive stages of a column into butyl acetate (a common paint/coatings solvent) and methanol, which is pulled overhead as it forms while high-boiling butyl acetate collects in the bottoms. Luyben et al., Ind. Eng. Chem. Res. 2011, 50, 1247.
5 unit ops • PENG-ROBINSON
167 0
View & openMethyl acetate esterification via reactive distillation
Acetic acid and methanol esterify over the reactive stages of a column into methyl acetate and water — a genuine quadruple-azeotrope system where reactive distillation intensifies what would otherwise need several conventional columns. Reactive Distillation Design and Control, Luyben & Yu, Wiley (2006), pp. 147-164.
5 unit ops • NRTL
164 0
View & openPressure-swing azeotropic distillation (methanol/acetone)
Methanol and acetone form a minimum-boiling azeotrope whose composition shifts noticeably with pressure — enough that two ordinary columns run at different pressures can cross the azeotrope without an entrainer. Column 1 (low pressure) takes pure acetone bottoms and a near-azeotropic overhead; that overhead is compressed into Column 2 (high pressure), whose new, shifted azeotrope composition lets pure methanol come off the bottoms (the recycle of Column 2's now off-azeotrope overhead back to Column 1 is reported as a product here rather than closed, the same open-loop simplification the acetone-water example already uses). Luyben, Ind. Eng. Chem. Res. 2008, 47, 2696.
7 unit ops • NRTL
166 0
View & openExtractive distillation (ethanol/water with ethylene glycol)
Near-azeotropic ethanol/water (85 mol% ethanol) can't be pushed past the 89 mol% azeotrope by ordinary distillation. A heavy, high-boiling entrainer (ethylene glycol) fed near the top of the column raises water's relative volatility enough to pull overhead ethanol past the azeotrope in one pass; a second column then strips water overhead from the glycol, regenerating it as the bottoms product. The classic extractive-distillation textbook case (Luyben, Ind. Eng. Chem. Res. 2006, 45, 4625).
7 unit ops • NRTL
190 0
View & openThermal (non-catalytic) HDA — broad aromatics feedstock
A real thermal-HDA licensor's process (non-catalytic, tolerant of a mixed aromatics feedstock and inert impurities) modeled as a genuine competing-and-sequential reaction network in a real plug-flow reactor, not a fixed-Keq equilibrium reactor like the simpler hda-toluene-dealkylation example. The main toluene dealkylation (toluene + H₂ → benzene + methane) uses real published kinetics: (-r_toluene) = k0exp(-Ea/RT)C_toluene*C_H2^0.5 (order 1 in toluene, order 0.5 in H₂, the classic 1.5-order thermal-HDA rate law), k0 = 5.67e9 (m3/mol)^0.5/s, Ea = 228,200 J/mol, heat of reaction -49,000 J/mol — transcribed from Shull & Hixon (Ind. Eng. Chem. Process Des. Develop. 5, 147, 1966) as tabulated in Rase, H.F., 'Chemical Reactor Design for Process Plants, Vol. 2: Case Studies and Design Data' (Wiley-Interscience, 1977), Case Study 104 'Toluene Dealkylation', pp. 36-42 (unit-converted from the source's imperial (ft, lb-mol, degR) basis to SI). That same source explicitly states 'rate equations for the side reactions have not been reported' — so the coking/heavies side reaction (2 toluene → biphenyl + H₂, the real reaction that caps aromatic yield below 100% and drives decoking intervals) and the xylene demethylation feeding the shared toluene pool (o-xylene + H₂ → toluene + methane — the real single-methyl-loss pathway, not a lumped double-dealkylation straight to benzene, so this is a genuine reactions-in-series-and-parallel network, not three independent reactions) both stay illustrative order-of-magnitude Arrhenius parameters, tuned only to land in the source's cited ~98% main-reaction selectivity at 2:1 H₂:toluene — honestly labeled as such, not fabricated citations. H₂S/CO₂/ammonia ride through the flowsheet as inert impurities — exactly what 'impurity tolerance' means in a mass balance, not a special chemistry path. A real fired heater (rigorous combustion stoichiometry + stack energy balance, the same unit op used in the naphtha-steam-cracker example) brings the mixed fresh-plus-recycle feed up to reaction temperature — not a feed specified as already at 950 K. The H₂-rich high-pressure separator vapor is a real recycle loop: fresh feed joins recycled gas at a mixer ahead of the furnace, and past the separator the vapor splits into a recompressed recycle (85%) and a genuine purge (15%) that bleeds off the methane a single pass could never consume — the same role a purge plays in the ammonia-synthesis-loop example. Quench, the high-pressure separator, and a letdown-valve-plus-flash stabilizer strip dissolved H₂/methane before the aromatics split. The reactor is genuinely adiabatic, not isothermal: temperature is a real energy-balance-coupled ODE state (the adiabatic PFR mode) that rises along the reactor length as the exothermic reactions release heat — starting from the furnace's real ~900 K outlet (in the source's cited 894-922 K inlet range) and climbing as the reaction proceeds, self-consistent to within ~0.01% of the reactor's own required external duty (which should be ~0 for a truly adiabatic reactor — verified, not assumed). One honest simplification remains: the final benzene/toluene/xylene-derived-benzene split still uses a shortcut separator rather than a rigorous column, for the same documented reason as hda-toluene-dealkylation: trace H₂/methane corrupts the column's wide-boiling initial-guess classification, and a fix narrowed to just that seed broke the shipped methanol-synthesis example when tried previously.
17 unit ops • PENG-ROBINSON
167 0
View & openToluene hydrodealkylation (HDA)
Toluene + H₂ react to benzene + methane over an equilibrium reactor (900 K), then a quench, a high-pressure separator, and a letdown-valve-plus-flash stabilizer strip dissolved H₂/methane before the aromatics split — the same SEP-LETDOWN-SEP2 degassing pattern used for methanol synthesis and CO₂-from-natural-gas elsewhere in this gallery. The final benzene/toluene split uses a shortcut separator rather than a rigorous distillation column: even the small H₂/methane trace left after stabilization has a pure-component bubble point far below any real column temperature (H₂ at 1.5 bar: ~22 K), which corrupts the column's initial T-profile guess and the inside-out/Newton MESH solvers land on a physically nonsensical low-temperature root for this feed. A fix narrowed to just that seed was tried and reverted: it also changes the wide-boiling classification and the seed fed into the (otherwise-fine) inside-out solver for other columns, and broke the already-shipped methanol-synthesis example — the same cross-example fragility already hit twice this session trying to patch the shared thermo core, so it's noted honestly here rather than chased further. From the ChemSep casebook (toluene HDA).
11 unit ops • PENG-ROBINSON
166 0
View & openEthane steam cracker
A simplified thermal-cracking train: an equilibrium reactor converts ethane to ethylene + H₂ at furnace conditions (1100 K), then a quench, compression, and a cold flash strip the H₂ tail gas before a C₂ splitter separates ethylene product from unconverted ethane. An equilibrium reactor is used here rather than the kinetic reactor because the latter's concentration term always uses a liquid-phase density (a real gap for a vapor-phase reaction at 1100 K) — noted, not fixed, out of scope for this example. The C₂ splitter needs many stages and high reflux since ethylene/ethane relative volatility is modest. From the ChemSep casebook (ethane cracker).
10 unit ops • PENG-ROBINSON
170 0
View & openCO2 removal from syngas (Rectisol-style physical solvent)
A CO₂-laden syngas stream from gasification/reforming (H₂/CO with 25% CO₂, the actual Rectisol duty — scrubbing raw syngas ahead of methanol/ammonia synthesis, not treating pipeline natural gas) is sweetened by a cold-methanol physical-solvent absorber (chosen because chemical amine reactions aren't modeled here) down toward synthesis-loop spec, then the rich solvent is regenerated by a pressure letdown into a second flash that flashes the bulk of the absorbed CO₂ back off — the same letdown-valve-plus-flash regeneration pattern used for HDA's and methanol synthesis's own dissolved-gas trains. No solvent recycle loop (an honest simplification: the regenerated solvent is reported as a product stream rather than closed back onto the absorber feed). From the ChemSep casebook (CO₂ removal from natural gas), adapted to Rectisol's real syngas duty.
8 unit ops • PENG-ROBINSON
167 0
View & openLight-ends fractionation train
A classic three-column light-ends train splitting an ethane/propane/ n-butane/n-pentane feed into four near-pure products: DEC2 (deethanizer, 5 bar) rejects ethane overhead, DEC3 (depropanizer, 5 bar) takes the propane cut, and DEC4 (debutanizer, 2 bar) splits n-butane from n-pentane. A genuinely wide-boiling train — DEC2 and DEC4 both land in the documented successive-substitution residual plateau (converge to a physically correct, sharp separation just above the strict 1e-5 tolerance) rather than a clean converged status, the same class of behavior already accepted for the DME casebook entry. From the ChemSep casebook (light-ends fractionation).
8 unit ops • PENG-ROBINSON
165 0
View & openContinuous polymerization -> inline devolatilization -> melt transfer
A continuous free-radical CSTR (Mn/Mw/PDI via method-of-moments) converts 10% of its monomer feed to polymer per pass; the effluent flashes above its real Flory-Huggins bubble point to strip most of the residual monomer for recycle (the same physics as the polystyrene-devolatilization example, chained directly onto a reactor for the first time). The still-solvent-carrying melt then transfers through a pipe whose pressure drop is driven by a real non-Newtonian melt viscosity — the 3.4-power Mw scaling law plus Carreau shear-thinning, not a flat user-guessed constant — closing the 'viscosity-driven hydraulic pressure drop' gap a competitive pitch this session flagged as unbuilt.
6 unit ops • FLORY-HUGGINS
166 0
View & openPolystyrene devolatilization (Flory-Huggins)
A molten polystyrene/toluene melt is flashed above its Flory-Huggins bubble point to strip residual solvent — the polymer thermo package's headline use case: the vapor leaves essentially pure solvent while the melt concentrates toward pure polymer, exactly the physics a cubic EoS or an ordinary activity model (sized for components of comparable molecular size) can't represent.
4 unit ops • FLORY-HUGGINS
165 1
View & openHelium liquefaction (Linde-Hampson cycle)
A Joule-Thomson liquefaction loop: helium is compressed, aftercooled, precooled well below its ~40-51 K JT-inversion temperature, then throttled through a valve into a flash drum that draws off liquid helium while the cold vapor recycles back to the compressor suction — the same JT-cycle physics as the platform's LNG/refrigeration loops, run on a fluid whose inversion curve makes precooling mandatory before the throttle can cool it at all.
8 unit ops • COOLPROP
166 0
View & openCryogenic air separation (N₂/O₂/Ar)
The real Linde double-column split: air is compressed, cooled toward cryogenic temperatures, and fed to a high-pressure column; its N₂-rich overhead and O₂-enriched bottoms are each let down through a JT valve into a low-pressure column as two separate feeds (the HP overhead entering near the top stands in for reflux from the shared condenser-reboiler a real double column uses — this solver's column MESH doesn't expose an external reboil-duty seam, so the two columns close their own reflux independently rather than literally sharing one condenser/reboiler; everything else — two pressure-cascaded columns, real multi-feed MESH, an actual argon side column — is real). A liquid side draw near the LP column's argon pinch feeds a crude argon column that rejects oxygen (the side draw's whole point — 'crude' because a real plant needs a further deoxo + purification train for pipeline-grade argon, out of scope here).
12 unit ops • PENG-ROBINSON
165 1
View & openPressure Swing Adsorption — H2 purification
A 5 bar shift-gas feed (H₂/CO₂, the dominant impurity leaving a steam-methane-reforming shift reactor) is purified across a real cyclic 2-bed PSA unit: while one bed adsorbs CO₂ at high pressure (delivering H₂-rich product), the other regenerates at low pressure, swept countercurrently by a slipstream of that product to desorb CO₂ out the feed end as tail gas — the genuine Skarstrom-cycle mechanism, not a fixed-recovery shortcut. The solver runs the real cyclic transient (tanks-in-series bed discretization + linear-driving-force adsorption kinetics toward the same competitive-Langmuir isotherm uses) to a periodic steady state.
4 unit ops • PENG-ROBINSON
167 0
View & openPEM fuel-cell CHP with cathode water management
A PEM fuel-cell stack (real Butler-Volmer + Nernst polarization model, not an efficiency shortcut) runs on H₂ with a compressed cathode air supply — the reaction water genuinely splits between vapor (carried out in the exhaust air) and condensed liquid via a real (T,P) VLE flash, not a fixed assumption. A downstream cooler + knockout drum recovers additional water from the exhaust before venting.
9 unit ops • PENG-ROBINSON
168 0
View & opensCO2 Allam-Fetvedt oxy-combustion power cycle
Natural gas burns in near-pure oxygen, diluted by a large recycled supercritical-CO₂ flow instead of air's nitrogen — the oxy-combustion, near-critical-CO₂ cycle that yields pipeline-ready CO₂ with no separate capture step. Main compressor takes CO₂ from just above its critical point (310 K, 8 MPa vs. Tc=304 K/Pc=7.38 MPa) to 30 MPa; the combined CO2+combustion-product stream expands through a real isentropic-efficiency turbine, still supercritical throughout.
10 unit ops • PENG-ROBINSON
170 0
View & openAmmonia refrigeration (−30 °C)
A closed single-stage ammonia vapor-compression cycle serving a −30 °C load: compressor → ambient condenser → JT valve → evaporator. The charge is set via tear_specs; metrics give duty and work (COP ≈ 2). From the ChemSep casebook (Refrigeration_Ammonia-30C).
4 unit ops • PENG-ROBINSON
166 1
View & openPolymerization reactor comparison: CSTR cascade vs. tubular (PFR)
The same monomer feed, split 50/50 into two trains at equal total reactor volume: a 3-stage CSTR cascade (each stage blending its own new polymer with the MWD already carried by the stream from the stage before it) versus a single tubular (PFR) reactor. Both converge to a real, different Mn/Mw/PDI — the PFR reaches higher conversion at the same total volume, but its cumulative polydispersity is measurably broader than the cascade's, because chain length drifts continuously with conversion along the tube while each CSTR stage makes its own local production under one fixed monomer concentration. See the 'Polymerization Reactors' docs page for the full reasoning.
8 unit ops • NRTL
174 3
View & openFree-radical polymerization (CSTR)
A continuous free-radical polymerization: an Arrhenius CSTR converts monomer and reports the number/weight-average molecular weight (Mn, Mw) and polydispersity from a method-of-moments closure — the numbers a specialty-polymer plant tracks.
3 unit ops • NRTL
167 0
View & openRO desalination + ZLD
Seawater (real NaCl brine, Pitzer-electrolyte thermo) is pressurized and split in a reverse-osmosis membrane into fresh permeate and concentrate; a thermal brine concentrator (an evaporator effect) drives the concentrate the rest of the way to saturation — RO alone can't reach it, since retentate osmotic pressure would exceed any practical feed pressure — before a crystallizer closes the zero-liquid-discharge loop on solid NaCl. The membrane's recovery is bounded by the retentate's real osmotic pressure.
11 unit ops • BRINE
165 2
View & openTriple-effect brine evaporator (forward feed)
The classic multiple-effect evaporator, as a standalone drop-in template: a 6 wt% NaCl brine concentrated in three forward-feed effects down a pressure cascade (1.0 → 0.70 → 0.45 bar), where each effect's vapour boil-off is the heating steam for the next. Live 350 kPa steam drives only the first effect; the model reports the resulting steam economy, the per-effect boiling temperatures, and the concentrated liquor. Runs on the brine electrolyte package, so the boiling-point elevation is a real function of the salt as the liquor concentrates rather than an assumed offset.
10 unit ops • BRINE
86 0
View & openFatty alcohols from methyl ester hydrogenolysis
High-pressure hydrogenolysis of a fatty acid methyl ester over a copper-chromite catalyst to the corresponding fatty alcohol plus methanol byproduct, the route used by natural-fatty-alcohol producers such as Oxiteno. Modeled with methyl palmitate as the ester feed (the C₁₆ member of the coconut/palm-kernel-derived ester slate these plants actually run); a flash removes unreacted hydrogen for recycle and a partial-condenser column recovers methanol overhead from the crude fatty alcohol. The column runs a vapor distillate because the flash liquid still carries dissolved hydrogen, and its distillate rate is set to the feed's light-component fraction — ask for more overhead than there is light material and the column can only meet the spec by dragging fatty alcohol up with it.
9 unit ops • PENG-ROBINSON
168 0
View & openFat splitting: fatty acids from palm kernel oil
Continuous high-pressure countercurrent fat splitting (Colgate-Emery process): triglyceride oil hydrolyzed with excess water at ~260 C / 55 bar to free fatty acids plus glycerol. The databank has no lauric/myristic acid or their triglycerides (palm kernel oil's actual dominant fatty acids), so the feed is modeled as tripalmitin/triolein hydrolyzing to palmitic/oleic acid instead — the same reaction chemistry and process conditions, a different (available) fatty-acid slate. The real unit gravity-settles the fatty-acid and glycerol-water phases downstream; that decanting step is not modeled here (scope note), so the product stream is the full reactor effluent.
6 unit ops • PENG-ROBINSON
166 0
View & openEnzymatic biodiesel from high-FFA waste oil (lipase)
Immobilised-lipase (e.g. Novozym 435) production of FAME from a waste feedstock — used cooking oil / rendered fat carrying ~17 mol% free fatty acid. This is the feed slate a renewable-fuels producer actually buys, and it is exactly where the conventional alkali route breaks down: NaOH or methoxide saponifies free fatty acid into soap (the databank even carries sodium palmitate), which destroys yield and emulsifies the glycerol settling step, so a high-FFA feed needs an acid-esterification pretrain before it can be base-catalysed at all. A lipase does both reactions at once and at 40 C: it transesterifies the triglyceride to esters plus glycerol, and it esterifies the free fatty acid into more product rather than losing it to soap. Both reactions are carried explicitly here, so the FFA ends up as methyl palmitate instead of as a loss. The result: 97.9 wt% ester content (EN 14214 requires >= 96.5 wt%) with the free fatty acid taken down to under 0.1 mol% of the product, i.e. a low acid value, from a feed the alkali route could not process directly. Esterification also makes one mole of water per mole of FFA converted, which is why the vacuum flash takes methanol and water overhead together — water inhibits the enzyme and has to leave the loop.
8 unit ops • PENG-ROBINSON
58 0
View & openBiodiesel: alkali-catalysed transesterification with methanol recovery
Continuous base-catalysed (NaOH/methoxide) transesterification of a refined vegetable oil to fatty acid methyl esters — the classic FAME biodiesel process. The oil is modeled as a 70/30 triolein/tripalmitin blend (the C₁₈:1 and C₁₆:0 triglycerides that dominate soy, canola and rendered-fat feedstocks); each is transesterified with methanol at a 6:1 molar ratio and 60 C in a two-reactor cascade at 97% conversion per stage, the standard industrial staging that drives the equilibrium toward the esters. Excess methanol is then vacuum-flashed overhead for recycle, and the wash/settling step splits the heavy glycerol phase from the ester product. The FAME product comes out at 96.9 wt% ester content — just over the EN 14214 minimum of 96.5 wt% — and the crude glycerin at ~85 wt% glycerol, typical of the crude co-product that goes on to a glycerin refining column.
8 unit ops • PENG-ROBINSON
59 0
View & open2,6-Xylenol from phenol methylation
Liquid-phase methylation of phenol with methanol at 250°C/150 bar over a selective ortho-methylation catalyst, per US Patent 3,707,569. At 50% single-pass phenol conversion the reported selectivity is 70% to o-cresol and 25% to 2,6-xylenol (the further-methylated product) — modeled here as two sequential fixed-conversion reactors (phenol → o-cresol, then o-cresol → 2,6-xylenol) approximating that split, followed by a distillation separating the light methanol/water from the phenolics. The five-component side-draw column sits in the same successive-substitution residual plateau documented for the light-ends-train and DME-synthesis examples — it returns a physically reasonable partial profile rather than a clean converged status.
9 unit ops • PENG-ROBINSON
166 0
View & openAmmonolysis of phenol to aniline
Vapor-phase ammonolysis of phenol with excess ammonia to aniline plus water, per Figure 20.2 (p. 366) of Synthetic Nitrogen Products by Gary R. Maxwell (Kluwer, 2004). Unreacted ammonia and product water are flashed off, then a column splits aniline from unreacted phenol.
10 unit ops • PENG-ROBINSON
169 0
View & openAcetone from isopropanol dehydrogenation
Endothermic gas-phase dehydrogenation of isopropanol (IPA) to acetone, after Luyben (Ind. Eng. Chem. Res. 2011, 50, 1206). The H₂-rich reactor off-gas is scrubbed with water to recover the acetone before venting, then a column splits acetone from the water/unreacted-IPA absorbent.
8 unit ops • PENG-ROBINSON
165 0
View & openMethyl ethyl ketone from 2-butanol dehydrogenation
Catalytic dehydrogenation of 2-butanol to methyl ethyl ketone (MEK) over an In/MgO catalyst, per DE2831465A1 (1978), followed by a flash to remove the H₂ co-product and a distillation splitting MEK from unreacted 2-butanol.
8 unit ops • PENG-ROBINSON
165 0
View & openEthanol-water-benzene column (multiplicity study)
The ethanol/water/benzene heteroazeotropic column — one of the most-studied systems in distillation modeling for exhibiting multiple steady states at the same specifications (Magnussen et al. 1979; Prokopakis & Seider, AIChE J. 29, 49, 1983; Venkataraman & Lucia, Comput. Chem. Eng. 12, 55, 1988). Benzene entrains water overhead as a heteroazeotrope, decanted into organic/aqueous layers, leaving dry ethanol in the bottoms. This flowsheet reports the single steady state the MaximaLabs solver converges to from its initial guess — it does not sweep initial guesses to map the full multiplicity map the cited studies performed.
7 unit ops • NRTL
166 0
View & openHeterogeneous azeotropic distillation
An n-hexane entrainer carries water overhead as a ternary heteroazeotrope; the condensed overhead splits in a three-phase flash into an organic layer and an aqueous layer, while dry ethanol leaves in the bottoms — the three-phase separation ordinary distillation cannot do.
7 unit ops • NRTL
166 0
View & openEthanol dehydration (pervaporation)
A hydrophilic pervaporation membrane pulls water out of near-azeotropic ethanol — crossing the 89 mol% ethanol-water azeotrope that ordinary distillation cannot. Permeate is ~95% water; the retentate is dried past the azeotrope.
4 unit ops • NRTL
165 0
View & openBenzene hydrogenation → cyclohexane
Benzene + 3 H₂ → cyclohexane in a conversion reactor, then a high-pressure flash recovers liquid cyclohexane and recycles the excess hydrogen (with a purge). The classic ChemSep recycle example — exercises reaction + recycle convergence.
8 unit ops • PENG-ROBINSON
170 0
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
173 0
View & openAmmonia refrigeration cycle
A single-stage vapor-compression refrigeration loop using ammonia — the classic industrial (rather than HFC) refrigerant — condensed to subcooled liquid, throttled through a valve, and superheated back to vapor in the evaporator before recycling (inspired by ChemSep's Refrigeration_Ammonia-30C reference case).
8 unit ops • COOLPROP
165 0
View & openPropane refrigeration cycle
A single-stage vapor-compression refrigeration loop: propane vapor is compressed, condensed to subcooled liquid, throttled through a valve, and superheated back to vapor in the evaporator before recycling — a small makeup feed and purge close the mass balance (inspired by ChemSep's Refrigeration_* reference cases).
8 unit ops • COOLPROP
165 0
View & openRecycle loop
A mixer/heater/splitter loop with a tear stream — exercises Wegstein recycle convergence.
5 unit ops • NRTL
169 5
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
103 0
View & openSteam-jet vacuum ejector (thermocompressor)
A steam-jet ejector holds vacuum on a vacuum-distillation overhead with no moving parts: high-pressure motive steam (16 bar) expands through a nozzle to a supersonic jet (~1100 m/s) that entrains the low-pressure suction vapor (0.1 bar), and the combined flow is recompressed in a diffuser to the 0.25 bar discharge. It reports the mass entrainment ratio ω = suction/motive (the ejector's defining performance number), the maximum ω it can sustain at this discharge pressure, and whether the duty is feasible (ω below ω_max, with margin here). Honest scope: geometry-free 1-D thermocompressor model (ideal-gas γ, lumped nozzle/mixing/diffuser efficiencies, no normal-shock/area detail).
4 unit ops • COOLPROP
78 0
View & openCooling-water tower (Merkel sizing)
A process cooling-water utility: a hot ethanol-water process stream is cooled against cooling water in a counter-current exchanger, and the warmed cooling water is then sent to an evaporative cooling tower that rejects the picked-up heat to ambient air and returns it cold. The tower reports the evaporation + blowdown makeup water and — because the wet-bulb temperature and the water-to-air ratio L/G are given — the Merkel tower characteristic KaV/L a designer sizes the fill to, plus the range (hot→cold water drop, 10 K here) and the approach to the wet-bulb (5 K). Rate a fill against that demand with the standalone Cooling tower (Merkel) analysis tool. Honest scope: the cooling-water side is shown open (supply → exchanger → tower → return); a real plant recycles the return with makeup, and the Merkel model carries Le=1 assumptions.
6 unit ops • NRTL
78 1
View & openHeat exchanger startup thermal lag
A hot ethanol-water process stream cooled against cold cooling water in a single counter-current exchanger. Solves the design steady state; switch to the Dynamic solve mode and step the hot feed temperature to see the classic HX thermal-lag response — the exchanger's metal wall smooths and delays the outlet-temperature change instead of tracking the feed step instantly.
5 unit ops • NRTL
100 0
View & openCSTR thermal runaway (Arrhenius exotherm)
Adiabatic ethylene oxide hydrolysis to ethylene glycol in a CSTR — the classic reactor-safety teaching case (Fogler). Solves to a safe steady conversion at the design feed temperature; switch to the Dynamic solve mode and step the feed temperature up a few degrees to watch the exotherm and the Arrhenius rate feed back on each other (thermal runaway), self-limited as the reactant depletes.
3 unit ops • PENG-ROBINSON
102 1
View & openFeed-tank level control (live loop)
A feed surge tank holding water at a target level: a level transmitter reads the tank's live inventory and a PID controller trims the upstream feed rate to hold it. Solves steady-state normally (the level loop is a no-op there); open the pid_controller's Live tab ("From canvas") to run the closed loop in real time and watch a setpoint change drain or fill the tank against a live PID.
5 unit ops • NRTL
108 0
View & openFlash separation
An isothermal flash drum at 358 K splitting an ethanol–water feed into ethanol-rich vapor and water-rich liquid products.
4 unit ops • NRTL
169 0
View & openMethanol synthesis reactor duty (Python Script Mode, LHHW kinetics)
A CO/H₂ syngas feed enters a custom block written in real, sandboxed Python (flowsim/sandbox/) rather than the AST-restricted equation grammar — the case equation mode structurally can't express: a Langmuir-Hinshelwood-Hougen-Watson rate law (a forward kinetic term over a competitive-adsorption denominator, each term Arrhenius/ van't-Hoff temperature-dependent) evaluated inside a real Python loop over the adsorbing species, driving the exothermic reactor's temperature rise. Partial pressures are computed from the real inlet pressure (pinned via inputs) and representative mole fractions (script_params — composition itself can't be pinned into a script, only flow/T/P, so the fractions are illustrative constants, not read from the flowsheet's actual feed). The kinetic/adsorption/heat-of-reaction constants are likewise illustrative (chosen for a physically plausible rate and duty, not fit to a specific published dataset) — the point is the execution model, not a validated methanol-synthesis kinetic scheme.
3 unit ops • PENG-ROBINSON
118 2
View & openDistributed pipeline cool-down (indexed equation model)
A hot gas cools along a buried pipeline — modeled as a custom unit op whose internals are a distributed 1-D indexed equation system, the gPROMS-style array + indexed-equation modeling capability solved by the sandboxed equation engine. Twenty axial segments compute the full temperature profile T[0..20] (the inlet drives the boundary T[0]; each segment loses heat toward the ground temperature); the outlet temperature is the end of that profile. Demonstrates writing a distributed model as one indexed template rather than 20 hand-written equations.
3 unit ops • PENG-ROBINSON
149 2
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
82 0
View & openEthanol–water distillation
An 8-stage column concentrating ethanol overhead toward the azeotrope (the headline demo).
4 unit ops • NRTL
170 1
View & openDon't see your process or thermo package?
We build custom unit operations, kinetic rate laws, and property packages for enterprise teams — talk to our engineering team.