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.
Multistream exchanger: one core, three streams, one free outlet
A cryogenic cold box is not a network of two-stream exchangers — it is one brazed-aluminium core with several streams exchanging heat simultaneously, and the multistream exchanger models it as such. Three streams share this core: 300 mol/s of 300 K feed gas being chilled, 250 mol/s of 190 K residue gas being rewarmed, and 60 mol/s of 200 K cold liquid. You specify outlet temperatures for all but one — 225 K for the feed gas, 280 K for the residue — and the remaining stream is the free one: its outlet, 230.1 K, is not specified but SOLVED, because it is what closes the adiabatic energy balance across the core. That is the correct number of degrees of freedom for an adiabatic exchanger, and specifying all three would over-specify it. The 1.08 MW duty and a composite-curve pinch check against a 3 K minimum approach come with it, so a specification that would need heat to flow the wrong way is rejected rather than reported. Bounded: this is a thermal feasibility and duty model, not a mechanical design. There is no core geometry, no layer stacking, no fin type, no per-stream pressure drop from passage dimensions — a real cold box datasheet needs all of those, and a vendor computes them from proprietary correlations.
7 unit ops • PENG-ROBINSON
9 0
View & openWellhead compression: what the reservoir gives and what it costs to move
A gas well is not a feed whose flow you type in. The rate is an OUTCOME of how hard the facility pulls on the reservoir, and this example starts there. The well runs the Vogel inflow-performance relationship: at a 250 bar reservoir pressure and a 5e-5 mol/s/Pa productivity index its absolute open flow is J x p_r / 1.8 = 694 mol/s, and the fraction of that you actually get follows 1 - 0.2(p_wf/p_r) - 0.8(p_wf/p_r)^2. Holding 180 bar at the bottomhole delivers 306 mol/s, 44% of open flow. Squeeze to 150 bar and it rises to 411; back off to 240 and it collapses to 49. The curve is deliberately not a straight line — that curvature is why compression pays for itself, and why the last increment of drawdown buys less than the first. Compression is where the stage count earns its keep. Taking that gas from 30 to 150 bar in ONE stage lands the discharge at 508 K (235 C) — past what reciprocating machine valves and lube oil tolerate, before any efficiency argument. Split it into three with intercooling to 313 K and the discharge is 362 K; four stages give 349 K. The temperature, not the power, is what sets the stage count on a real machine. Read the reported duty carefully. duty on this unit is the NET of the compression work and the intercooler heat removed, summed into one number — it goes from +2094 kW at one stage to -384 kW at three, not because compression got cheaper but because there is now intercooling to subtract. It is not shaft power, and this example does not present it as such.
3 unit ops • PENG-ROBINSON
8 0
View & openGas dehydration: why the property package decides the answer
A wet pipeline gas at 70 bar and 40 C is chilled to 15 C, the condensed free water is knocked out, and a 4A molecular-sieve bed takes the rest down to the cryogenic 0.1 ppmv spec. It is the standard front end of every gas plant, and it is one number wide: how much water the gas holds at saturation. Everything downstream is arithmetic on that number — the knockout drum's liquid rate, the sieve's cycle time, the bed size, the regeneration duty. Here the feed carries 1500 ppmv (71 lb/MMscf). Chilling to 288 K drops the saturation limit to 313 ppmv (14.9 lb/MMscf), so 3.57 mol/s of essentially pure water (99.9 mol%) falls out in the KO drum for a 3.91 MW chilling duty, and the sieve carries the remaining 0.94 mol/s. A 4000 kg bed then sizes out at 2.69 m diameter by 0.96 m deep on a 7.8-hour cycle — the 8-hour cycle real molecular-sieve dehydrators are built around — with 108 kW of regeneration duty and 11 kPa of bed pressure drop. This example runs on CPA (Cubic-Plus-Association) and not on a cubic, deliberately. Water in a hydrocarbon gas is the case a bare cubic equation of state is worst at: its hydrogen bonding is not a small correction to be absorbed into a binary interaction parameter, it is the thing that sets the answer. CPA adds a Wertheim association term on top of SRK and switches it on only for the hydrogen-bonding species, so hydrocarbons still behave exactly as SRK. Bounded, and the bound is measured. Against the McKetta-Wehe chart's ~60 lb/MMscf for methane at 100 F and 1000 psia, CPA lands at ~55, PR at ~50 and SRK at ~45 — CPA is the closest, and all three still underpredict. None of them has a cited methane-water binary interaction parameter, and extrapolating CPA's published n-alkane correlation (kij = 0.1915 - 0.026*n_carbon, fitted C₃..C₁₀) down to methane would fabricate the number that decides the answer, so it stays absent. Good for a first-cut dehydration duty; not a guarantee-grade contract number.
6 unit ops • CPA
9 0
View & openCrude unit: why a CDU needs pumparounds
A pumparound draws liquid off a tray, cools it, and returns it a few trays higher. It removes no material — its entire job is heat. This example solves the same atmospheric crude unit twice, with its two pumparounds and without, and the difference is not a matter of degree. With them the rigorous column converges and cuts correctly: every product is dominated by the pseudocomponent it is named for (naphtha cut_1, kerosene cut_2, diesel cut_3 at 0.857, residue cut_4 at 0.677), the cut ladder spans 134 K, the pumparound duty reads back as exactly the -7.00 MW specified, and the reboiler sits at +2.25 MW against a 1.25 MW condenser. It solves in about 5 seconds. Without them the rigorous energy-balance MESH does not converge at all at this operating point — it stalls at a residual of 7.9e-3 with a component balance off by 0.45. That is the honest result, and it is the whole point: the feed arrives at 660 K from the fired heater carrying far more enthalpy than the overhead condenser's 1.26 MW can remove, and with no pumparound to take the rest there is no operating point for the solver to find. What comes back instead is FlowSim's screening carve, the fallback model, which has no rigorous stage energy balance — and it says so, in a warning on the result. Its answer is worth looking at precisely because it is the degraded one: the naphtha cut comes back dominated by the second-lightest pseudocomponent rather than the lightest, the residue by cut_3 rather than cut_4, the ladder collapses from 134 K to 85 K, and the reboiler duty goes negative at -5.23 MW — the column asking to be cooled rather than heated. Those numbers are the carve's, not a rigorous solution's, and this example is built so you can see the difference between the two rather than be handed one as the other. A pumparound is only meaningful against a rigorous stage energy balance, so this example runs ns_energy and rigorous_draws: under constant molal overflow the vapour rates are PINNED, and removing heat provably cannot move an internal flow. Specifying a pumparound therefore switches the energy balance on for you. Bounded — read the size before you scale it up. This is 12 stages on 4 pseudocomponents because that is what the rigorous-energy path can currently afford: the same column at Brent's full 20 stages and 8 cuts did not converge in 48 minutes, against 115 s on the constant-molal-overflow path. The cost is the flash inner loop, which profiling puts at 82% of the solve, evaluated once per unknown per Jacobian (332 unknowns at that size) by finite differences — and on petroleum pseudocomponents that loop is pure Python, because CoolProp has no entries for them. Analytic K-value derivatives are the fix at this size; the dense Jacobian's O(n^3) factorization is what binds at full commercial scale. Both are known, and this example is deliberately small rather than quietly slow.
9 unit ops • PENG-ROBINSON
10 0
View & openHydrotreater HP separator (Chao-Seader)
The high-pressure separator on a hydrotreater: reactor effluent — mostly hydrogen, with light ends and liquid product — is flashed hot and at pressure to recover recycle gas overhead, then let down to release the dissolved gas from the product. This runs on Chao-Seader, the semi-empirical K-value method refiners actually use for hydrogen-rich hydrocarbon systems, and which the app offers but no example used. It is not a relabelled cubic: K = gamma*nu/phi builds the liquid fugacity from the Curl-Pitzer corresponding-states correlation and the activity from regular-solution theory, with SRK supplying only the vapour fugacity. On this feed it lands at 89.2% vaporised and 61.7% recycle-gas hydrogen, against Peng-Robinson's 91.7% / 59.3% and SRK's 90.4% / 60.2% — a real, if modest, difference on the number a recycle-compressor is sized from. Honest about what is approximate: the package ships as Chao-Seader, and the Grayson-Streed 1963 special coefficients for hydrogen are a documented follow-up rather than transcribed, so the HYDROGEN K itself comes from the general correlation and is approximate — it saturates the solver's K bound here. Read the hydrocarbon splits and the phase fractions, which is what the method is good at; do not read the H₂ K-value as rigorous. Chao-Seader is a K-value method only, so enthalpy and density come from the inherited SRK — the pairing Aspen also uses.
7 unit ops • CHAO-SEADER
36 0
View & openFCC riser: the gasoline optimum
A fluid catalytic cracking riser — the unit that makes most of a refinery's gasoline — showing the one result that decides how you run it. Gas oil cracks to gasoline, but gasoline overcracks to gas and coke, and the catalyst deactivates as coke lays down. Those three together mean gasoline goes through a MAXIMUM in contact time: past the optimum, running the riser harder destroys product while conversion keeps climbing. Open the sensitivity and the curve draws itself — that hump is the whole point. A first-order network (all hydrocracker can express) makes gasoline rise monotonically with conversion and would recommend exactly the wrong operation. The cat/oil ratio is computed, not chosen: cracking is endothermic and the only heat source is the sensible heat of hot regenerated catalyst, so the circulation follows from a heat balance and lands in the real 5-10 band. That is the number tying the riser to the regenerator an operator actually turns — raise the regenerator temperature and watch it fall. The rate constants here are illustrative and are NOT any real feed's kinetics. The unit op deliberately ships none: an FCC lump matrix is regressed from one feed on one catalyst, it is licensor-proprietary, and a fabricated one would decide the answer while looking authoritative. A riser without constants fails validation and says why. Bring your own regression and this becomes your riser. Bounded: three lumps (no per-cut gasoline detail), isothermal riser (a real one drops 30-60 K as the endotherm bites), no catalyst/vapour slip, and no regenerator — coke burn and the air rate are a separate unit this does not model.
3 unit ops • PENG-ROBINSON
33 0
View & openWellhead gathering — cold separation and the hydrate check
A wet-gas wellhead through a JT choke, a cold separator and a gathering line — the flowsheet that gives HYSYS Upstream's own tools (well IPR, hydrates, water content, gas pipeline) something real to work on. All four are in the Analysis panel and none had a curated example. From the flowsheet. 800 mol/s of wet gas lets down 120 to 60 bar across the choke, cooling itself to 294 K by Joule-Thomson alone; a chiller takes it to 250 K (2.6 MW) and the cold separator drops 88.5 mol/s of condensate (11%), sending 711.5 mol/s of sales gas down 25 km of 300 mm line for a 3.8 bar drop at 2.4 m/s. Well deliverability (Analysis > Well IPR). Vogel's composite IPR from one test point (0.045 at 200 bar flowing bottomhole, against a 240 bar reservoir and a 180 bar bubble point) gives an absolute open flow of 0.18 and, at 120 bar flowing pressure, a deliverability of 0.125 — the curve that says whether the well can actually feed this train. The hydrate check (Analysis > Hydrates, Water content). This is the pair that matters and the reason the two tools belong together. At 60 bar the gas is water-saturated at 21.2 lb/MMscf with free water present; Towler-Mokhatab puts the hydrate formation temperature at 291.2 K. Operating anywhere near seabed or winter temperature — 288 K, say — is 3.2 K inside the hydrate envelope, calling for about 20.5 wt% MEG to stay clear with a 3 K margin. A line that is hydraulically fine can still plug solid. **.
7 unit ops • PENG-ROBINSON
81 1
View & openFeed-effluent preheater — duty from the flowsheet, geometry from EDR
A feed/effluent preheater, built so the shell-and-tube rating in the Analysis panel has a real duty to rate. The flowsheet answers how much heat; the rating answers whether this exchanger can move it — the split Aspen sells as EDR, and it had no curated example. From the flowsheet. Hot reactor effluent (130 mol/s at 420 K) preheats 120 mol/s of cold feed to 360 K, transferring 1.53 MW and leaving the hot side at 373 K, against an LMTD of 66.4 K. Those are the numbers you carry into the rating. The rating (Analysis > HX design). Put a candidate bundle against that duty — a 0.6 m shell, 320 tubes of 19 mm OD on a 4.88 m length, two tube passes, 0.25 m baffle spacing — and the Bell-Delaware method returns U = 681 W/m2K, 93.2 m2 available against 53.6 m2 required: 74% over-surface, adequate. It also exposes the correction factors that actually decide the shell-side coefficient (segmental-cut j_c = 0.91, leakage j_l = 0.67, bypass j_b = 0.54, combined 0.33), which is where a real rating lives — most of the difference between an ideal bank and the bundle you can buy is leakage and bypass. Reading the margin. 74% over-surface is generous, not automatically right: it buys fouling allowance and turndown, and costs capital and residence time. The rating is the tool for trading those off — shrink the bundle and watch the margin close. **.
5 unit ops • PENG-ROBINSON
76 0
View & openLPG storage — fire case, PSV sizing and flare radiation
An LPG storage and truck-loading facility, built so the relief study that follows it is the real one: rundown from the fractionator is cooled, let down to storage pressure, held in a sphere, and pumped to a loading line. The process itself is deliberately simple — the demonstration is what you do with it next, using the Analysis panel's API 520/521 tools, which is the workflow HYSYS sells its Depressuring and Flare utilities on. Fire case (Analysis > Fire-case relief). The governing scenario for a pressurised LPG vessel. A 160 m2 wetted sphere in a pool fire with adequate drainage takes 2.77 MW of absorbed heat (API 521 environment factor 1.0); at a relieving pressure of 18 bar abs the stored 70/30 propane-butane boils at 338 K with a latent heat of 270 kJ/kg, so the PRV must pass 10.3 kg/s — an API 526 M orifice. Reaction force (Analysis > Relief reaction force). That same 10.3 kg/s leaving a 150 mm tailpipe chokes at 9.5 bar and 260 m/s, putting 17.7 kN on the pipe — the load the tailpipe supports have to carry, and the number that decides whether the discharge piping needs bracing. Flare radiation (Analysis > Flare radiation). Burning that relief load (46 MJ/kg, 30% radiated) releases 473 MW. From a 40 m radiant centre the API 521 exclusion zones come out at 64 m horizontal for continuous exposure, 18 m for emergency personnel access, and zero for equipment. The actionable result: a receiver 60 m away sees 2.5 kW/m2 — comfortably under the 4.73 kW/m2 personnel limit, but above the 1.58 kW/m2 continuous limit, so a permanently manned building there needs shielding or relocation. Thermal relief (Analysis > Thermal relief). A second, entirely different scenario on the same facility: the loading line blocked in full of liquid and warmed by the sun. 12 kW into trapped LPG (cubic expansion coefficient 3.9e-3 /K at 526 kg/m3) needs only 0.017 kg/s — a D orifice, the smallest API 526 size. Sizing this line for the fire case instead would oversize the valve by three orders of magnitude in area, which is exactly the mistake the separate tool exists to prevent. **.
7 unit ops • PENG-ROBINSON
75 0
View & openRelief system — the fire case, on the flowsheet
Two vessels on one fire zone, each protected by a relief valve, both discharging into a shared flare header. The point is that nothing here is retyped: the relieving temperature, pressure, composition and molecular weight come from the solved streams, and the flare's load is the sum of what the valves actually send it. The relief study, block by block. PSV_SEP is on the separator overhead: its scenario is the API 521 external fire, Q = C·F·A^0.82 over 45 m² of wetted surface, and the vapour rate is Q/λ with the latent heat taken from the property package at the relieving pressure rather than assumed. PSV_SURGE protects the surge drum on the classic blocked-outlet case — it relieves the whole inlet flow, which is a number the canvas already knows. Each reports its required orifice area with the API 526 letter above it. Why they are drawn as lifted. Both carry relieving: true, which models the relief case rather than normal operation. Turn it off and each valve is shut — the process passes through untouched and only the sizing is reported — but then the flare has no load to size against, and says so instead of inventing one. A design load only becomes a flow when you say the valve is open. What the flare adds that valve-by-valve sizing misses. A fire zone lifts every valve in it at once, so the header carries both loads together: that is what sets the built-up back pressure, and it is checked against the lowest-set valve on the header, because a back pressure a 20-barg PSV shrugs off will chatter a 6-barg one beside it. The tip is checked against the API 521 ~0.5 Mach blow-off limit, and the radiant flux at a receiver 60 m away against the 4.73 kW/m² personnel level, with the heat of combustion computed from the relief gas itself. Bounds, stated. A single header (the multi-branch network with per-source back pressures is the Flare network tool); a point-source radiation model with no wind tilt; no knock-out or seal drum; and the fire case is API 520's peak instantaneous rate, not a depressuring transient — that is the Depressuring / blowdown tool.
7 unit ops • PENG-ROBINSON
47 0
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
126 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
124 1
View & openCold-separator NGL recovery / dew-point control
A rich natural gas is chilled in the gas/gas exchanger + propane-chiller train (lumped here as one cold box) to -33 degC and let into a cold separator. The heavy hydrocarbons (C3+) drop out as a raw NGL liquid, leaving a leaner sales gas that meets its hydrocarbon dew-point spec — so no more liquid forms as the gas cools in the export pipeline. The cold separator is modelled as an adiabatic flash fed by the chiller, so the single knob (the chill temperature) drives both the NGL recovered and the refrigeration duty: colder recovers more NGL but costs more refrigeration (the built-in sensitivity). Peng-Robinson handles the hydrocarbon VLE; the companion gas-conditioning utilities (hydrate risk, water content, Joule-Thomson choke cooling, and compressor sizing for the sales-gas recompression) quantify the rest of the plant around it.
5 unit ops • PENG-ROBINSON
120 0
View & openNaphtha steam cracker: furnace, quench, compression, cryo train
The full ethylene-plant process shape (steam-methane-cracking's headline technology, e.g. Linde's steam cracking line): a fired-heater convection preheat, a three-reactor lumped pyrolysis furnace, a transfer-line-exchanger quench, a primary fractionator pulling off pyrolysis gasoline, two-stage compression with interstage knockouts, selective acetylene hydrogenation, and a cryogenic cold train (cold-flash light-gas rejection, deethanizer, C₂ splitter, depropanizer) delivering four real products — ethylene, propylene, a butadiene-rich C₄ cut, and a pygas/heavy-ends byproduct — plus an H₂/CH₄-rich tail gas and two knockout condensate streams.
30 unit ops • PENG-ROBINSON
180 2
View & openCryogenic NGL recovery (GERG-2008 EoS)
A natural-gas dew-point-control / NGL knockout run on the GERG-2008 reference equation of state — the multiparameter Helmholtz model the LNG and custody-transfer industries use because cubic EoS (Peng-Robinson/SRK) are off by several percent on cryogenic natural-gas density. Rich pipeline gas is chilled, let down across a Joule-Thomson valve into the two-phase region, and flashed cold to drop out an NGL liquid (propane/butane-rich) from the methane sales gas. The value is accuracy: on this flowsheet GERG predicts an NGL liquid density ~10% different from Peng-Robinson at cryogenic conditions — enough to change vessel and exchanger sizing. Implemented via CoolProp's multiparameter Helmholtz mixture model (GERG-2008 binary reducing/departure functions), a validated implementation — not a hand-transcription of GERG's thousands of coefficients. Scope: natural-gas / light-hydrocarbon components only (every species must be a CoolProp fluid); see.
6 unit ops • GERG-2008
169 2
View & openClaus sulfur recovery unit (SRU): the 2:1 ratio that sets the ceiling
The back end of the amine train, and the unit that keeps a refinery's sulfur out of the atmosphere. Acid gas off an amine regenerator (60% H₂S, 36% CO₂) is part-burned in a reaction furnace, then reacted over two catalyst beds with sulfur condensed between them. The whole design follows from one number. The furnace burns a fraction phi of the H₂S to SO₂ (H₂S + 3/2 O₂ → SO₂ + H₂O); the Claus reaction then consumes them at 2:1 (2 H₂S + SO₂ → 3 S + 2 H₂O). Burn exactly one third and the effluent arrives at precisely 2 H₂S per SO₂, so neither reagent is left over — which is why air demand, not catalyst, is the manipulated variable in every real Claus plant. Off-ratio, the excess reagent walks straight through to the tail gas and recovery is capped by a stoichiometric ceiling min(3phi, 3(1-phi)/2) that no amount of catalyst can beat. Run the built-in combustion-fraction sweep to see it: recovery peaks at 95.3% at phi = 1/3 and falls away symmetrically — 85.8% at phi = 0.30 and also 85.8% at phi = 0.40, 71.5% at phi = 0.25 and also at phi = 0.50, because the ceiling's two branches cross at one third. Air demand is not symmetric though (128.6 vs 171.4 mol/s at those same two points), so over-firing costs blower duty on top of the lost sulfur. At the design point the unit makes 57.17 mol/s of liquid sulfur from 60 mol/s of H₂S against a 142.9 mol/s air demand, and the 2.84 mol/s of sulfur reaching the tail gas is still at exactly 2:1 H₂S/SO₂ — the unconverted reagents leave in the ratio they were fed, which is what a tail-gas treating unit downstream is sized for. The sulfur atom balance closes exactly (60.000 mol/s S in, 57.165 as liquid sulfur + 2.835 in the tail gas). Staging is why two beds get to 95%: each converts a fraction of what is left, so X_total = 1 - (1-X_thermal)*prod(1-X_i) — 0.65 thermal then 0.70 and 0.55 catalytic.
4 unit ops • PENG-ROBINSON
33 0
View & openC5/C6 isomerization: why the colder catalyst wins
The light end of a gasoline pool. Straight-chain C₅/C₆ paraffins have poor octane, their branched isomers have good octane, and the reaction between them is a simple reversible exothermic rearrangement. Which means the equilibrium gets worse as the reactor gets hotter — and that single fact, not activity, is the technology choice in this unit. Run the built-in temperature sweep: this light straight-run naphtha reaches 74.9% iso-C₅ and 67.2% iso-C₆ at 400 K (the chlorided-alumina window) and only 65.3% and 57.6% at 530 K (the zeolitic window). A chlorided-alumina catalyst does not beat a zeolite by being more active; it beats it by approaching a better equilibrium. That is also why the two are not interchangeable in a revamp — a zeolitic unit cannot be pushed to alumina octane by running harder, only by running colder than its catalyst allows. Two things the flowsheet shows directly: moles are conserved exactly (one molecule in, one molecule out — 100.00000 mol/s out for 100 in, the module's own gate), and the benzene and cyclohexane in the feed pass through untouched at 4.00% and 6.00%, because a component named in no pair is not something this block pretends to convert. Only two pairs are written (n-pentane/isopentane and n-hexane/2-methylpentane) and that is deliberate: pairs are applied in sequence over a shared mole pool, so two pairs sharing one normal would let the second redistribute what the first already converted. A real C₆ network (n-hexane / 2-MP / 3-MP / 2,2-DMB / 2,3-DMB, each with its own equilibrium) is a coupled problem this block does not solve — see the.
3 unit ops • PENG-ROBINSON
34 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
178 0
View & openRenewable diesel & SAF: HEFA hydrotreating train
The HEFA (Hydroprocessed Esters and Fatty Acids) pathway to sustainable aviation fuel and renewable diesel from fats/oils/greases: a triglyceride feed (triolein) plus a large hydrogen excess is hydrodeoxygenated (HDO) to n-paraffins + propane + water, the paraffins are hydrocracked/isomerized toward the jet range, the H₂-rich recycle gas and the HDO process water are knocked out, the light ends are stabilized, and a two-column fractionation splits the product into light naphtha, a jet-range SAF cut, and renewable-diesel bottoms.
17 unit ops • PENG-ROBINSON
170 2
View & openPatent benchmark: selective C3 diene/acetylene hydrogenation (US6495732B1)
Real patent replication: US6495732B1's palladium-catalyzed selective hydrogenation of a cracked-gas C₃ stream, removing methylacetylene (propyne) and propadiene down to trace levels while leaving propylene and propane untouched — the patent's own Example 1 feed (82.7 mol% propylene, 2.37% methylacetylene, 1.30% propadiene) reacted here to '>99.5% removal of both dienes/acetylenes, no propylene-to-propane over-hydrogenation' (propane's mole fraction is unchanged before/after — the actual selectivity claim the patent is about).
6 unit ops • PENG-ROBINSON
165 0
View & openFLNG dual N2-expander liquefaction
A reverse-Brayton (turboexpander, not vapor-compression) liquefaction train — the compact, offshore-friendly FLNG alternative to mixed-refrigerant cycles like C3MR. Natural gas is acid-gas-scrubbed and mol-sieve-dried (fixed-recovery separators, the same simplification the existing carbon-capture example uses for amine treating), then cooled in two cascaded closed nitrogen loops: a warm loop precools the gas and the cold loop's own N₂ charge, and a cold loop finishes the liquefaction to ~113 K in a main cryogenic multi-stream exchanger. Both loops are pure compressor + turboexpander cycles — no phase change in the refrigerant, no JT valves — the real differentiator from every other LNG example here. Single precool level and a single MCHE bundle (a real train uses more); refrigerant charges are set via tear_specs.
17 unit ops • PENG-ROBINSON
166 1
View & openDiesel hydrotreater with closed H2 recycle + amine wash
Diesel (an n-hexadecane carrier with a dibenzothiophene sulfur slice) and hydrogen react over a trickle-bed-equivalent reactor (dibenzothiophene + 3H2 → biphenyl + H₂S, the real HDS desulfurization route) after a fired-heater preheat. Hot and cold high-pressure separators knock the light gas off the treated oil; an amine wash (a fixed-recovery separator — the same simplification the existing carbon-capture example uses, not a full electrolyte amine model) scrubs H₂S from the recycle gas before a compressor closes the loop back to the reactor feed, with a small purge controlling buildup. A pressure-letdown valve + stripper finish the treated oil, removing dissolved light ends before the desulfurized diesel leaves the bottoms.
18 unit ops • PENG-ROBINSON
169 0
View & openDeep ethane recovery with propane-refrigerated feed chilling
Associated gas is chilled by an external propane refrigeration package before a demethanizer recovers ethane and heavier as NGL bottoms from a methane-rich residue gas overhead — the cryogenic-chilling role Ortloff's CCS/GSP processes play ahead of the turboexpander in a real deep-ethane-recovery plant. The mechanical refrigeration loop itself (compressor/condenser/valve) isn't separately modeled here; the chiller's duty is represented directly as the feed's cooled outlet temperature (the same honest-simplification pattern used for LNG cold-box examples elsewhere in this library).
5 unit ops • PENG-ROBINSON
166 0
View & openCO2/ethane extractive distillation with n-decane
CO₂ and ethane are close-boiling (both around 195 K at 1 atm) and form a near-azeotropic VLE at NGL-processing pressures, a known problem for straight distillation in CO₂-flood-associated gas and acid-gas-rich NGL streams. A heavy n-decane solvent shifts CO₂'s relative volatility enough to take it overhead in far fewer stages than an ordinary deethanizer would need; a second column then strips the solvent from the ethane bottoms for recycle. The extractive column runs at a moderately high reflux (R=4.5) — the operating point a genuinely close-boiling pair needs to hold a sharp CO₂/ethane split with a heavy solvent — and both columns converge.
7 unit ops • PENG-ROBINSON
164 0
View & openReformate splitter via dividing-wall column
A refinery catalytic-reformer stream (benzene/toluene/o-xylene plus a non-aromatic n-heptane proxy) is split into three purified aromatics cuts by a single thermally-coupled dividing-wall column instead of two ordinary columns in series — the same DWC economics as the BTX example, applied to a genuine reformate splitter duty. Dejanovic, Matijasevic, Jansen, Olujic, "Designing a Packed Dividing Wall Column for an Aromatics Processing Plant," Ind. Eng. Chem. Res. 2011, 50, 5680.
5 unit ops • PENG-ROBINSON
166 0
View & openPhenol + acetone via the Hock process (cumene peroxidation)
The route that makes ~95% of the world's phenol — and co-produces acetone, the classic two-products-from-one-feed economics. It completes the cumene story: the existing cumene-synthesis example makes cumene from benzene + propylene; this oxidizes it onward. Two atom-balanced steps: air peroxidation (cumene + O₂ → cumene hydroperoxide, CHP) at low per-pass conversion, then acid-catalyzed cleavage (CHP → phenol + acetone, near-complete). The spent air is vented, and the crude is separated by boiling point (acetone 56 C < cumene 152 C < phenol 182 C < CHP): high-purity phenol, crude acetone as the co-product, and unreacted cumene recovered for recycle. HONEST SCOPE: rigorous atom-balanced reaction stoichiometry; cumene hydroperoxide is a databank pseudo-component (no CoolProp entry) flashed under Peng-Robinson. The purification is spec-based component-split separators (the Aspen 'Sep'-block technique), not rigorous columns. The acetone product comes out ~98% because residual dissolved air (O₂/N₂) reports overhead with it — a real plant adds a light-ends/degassing column for polymer-grade acetone; phenol comes out essentially pure. Recovered cumene is shown as an open recycle stream.
16 unit ops • PENG-ROBINSON
165 0
View & openButene/isobutane alkylation
Sulfuric-acid alkylation of butene with excess isobutane produces high-octane alkylate gasoline blendstock; a conversion reactor stands in for the acid-catalyzed carbocation chemistry (a literal acid/hydrocarbon settler would need H₂SO₄ electrolyte thermodynamics this package doesn't carry — out of scope, same as the reactor already being a stand-in for the chemistry itself), and a deisobutanizer-style column recovers unreacted isobutane overhead. The high isobutane:olefin ratio real alkylation units run is maintained almost entirely by recycling that isobutane back to the reactor feed — closed here as a real Wegstein-converged tear loop, with only a small makeup feed replacing what the reaction actually consumes, rather than the previous version's isobutane leaving as an unrecycled product. Luyben, Principles and Case Studies of Simultaneous Design, Wiley (2011); Ind. Eng. Chem. Res. 2009, 48, 11081.
6 unit ops • PENG-ROBINSON
166 0
View & openCumene production (benzene alkylation)
Benzene and propylene alkylate over a fixed-conversion reactor to cumene (isopropylbenzene, the feedstock for phenol/acetone via the Hock process); a downstream column recovers unreacted benzene overhead for recycle-quality purity while cumene leaves the bottoms. Luyben, Ind. Eng. Chem. Res. 2010, 49, 719.
7 unit ops • PENG-ROBINSON
166 0
View & openTAME synthesis via reactive distillation
Tert-Amyl Methyl Ether (TAME) is etherified from a cracked C₅ cut's reactive isoamylenes (2-methyl-1-butene / 2-methyl-2-butene) and methanol over the reactive stages of a column, pulling unreacted light C5s overhead while methanol-free TAME leaves the bottoms — reaction and separation in one shell, the same reactive-distillation pattern as the DME etherification example. Luyben, Ind. Eng. Chem. Res. 2005, 44, 5715.
5 unit ops • PENG-ROBINSON
165 0
View & openTEG natural gas dehydration
Wet natural gas is contacted counter-currently with lean triethylene glycol (TEG) in an absorber, pulling water vapor into the glycol to meet a pipeline water spec; the rich glycol is then let down in pressure and regenerated in two flashes — the first flashes off the bulk of the co-absorbed methane, the second (hot) flash boils the absorbed water off the now nearly gas-free glycol, leaving hot lean glycol bottoms (its recycle back to the absorber is reported as a product, the same open-loop simplification used elsewhere in this library). Water is the most common undesirable natural-gas impurity — it forms hydrates that plug valves and fittings once the gas is compressed or cooled.
10 unit ops • PENG-ROBINSON
165 2
View & openBrent Blend CDU (characterized from a real assay)
An atmospheric crude unit fed by a named, cited crude rather than invented pseudocomponents: Brent Blend (NOAA ADIOS oil EX00009, API 40.1, SG 0.8246, 0.35 wt% sulfur; the underlying assay is ExxonMobil's published Brent distillation curve). The bundled assay library (561 crudes, flowsim.backend.crude_assays) supplies the true-boiling-point curve; assay_to_pseudocomponents cuts it into 8 equal-volume pseudocomponents and characterizes each by Riazi-Daubert (Tc/Pc/MW from NBP + SG) and Edmister (acentric factor) — the eight cut_N entries below are that output verbatim, not hand-tuned numbers. The train is preflash drum → fired heater (660 K) → 20-stage atmospheric column with two side draws, yielding naphtha overhead, kerosene and diesel side cuts, and atmospheric residue. Three things worth knowing: (1) an assay reports one whole-crude gravity, but density rises steeply with boiling point, so the cuts are characterized at constant Watson K — Kw is fitted by requiring the cuts' volume-average SG to return the measured bulk 0.8246, giving Kw = 11.95 (the published paraffinic band is 11.4–12.1, which the fit was not tuned to hit) and per-cut gravities running 0.689 for the light naphtha to 0.971 for the 595 °C residue; (2) mole fractions follow from that — equal volume means mass ∝ SG, so each cut's mole fraction is proportional to SG/MW; (3) the column runs with rigorous_draws — real MESH liquid withdrawals — because the default carve mode (side products sliced out of a converged 2-product profile) returns two near-identical draws here and does not fractionate. Bounded: constant Kw is itself an idealization (a real crude's Kw drifts a few tenths across the barrel, and aromatic/naphthenic crudes differ), but it is the standard characterization and is strictly better than one gravity for every cut.
9 unit ops • PENG-ROBINSON
49 0
View & openCrude distillation unit (full train)
A fuller atmospheric CDU: a crude/residue preheat exchanger, a desalter (wash water mixed in, then split off as brine), a fired heater, the multi-draw column, three steam side-strippers recovering kerosene / light gas oil / heavy gas oil, and an overhead condenser + three-phase reflux drum (fuel gas / naphtha / sour water). A pumparound heat-integration loop (drawing liquid off an interior stage, cooling it externally against crude, and returning it colder to preheat the column's own upper trays) was attempted — both a 2-loop and a 1-loop version — but proved too numerically expensive to converge in reasonable time and was dropped rather than shipped half-tuned; everything else in the reference PFD is real. From the ChemSep casebook (crude distillation).
27 unit ops • PENG-ROBINSON
166 3
View & openSnohvit mixed-fluid-cascade LNG liquefaction
A simplified Statoil/Linde MFC train: three independent, cascaded closed refrigerant loops (propane precool, an N₂/methane/ethane liquefaction MR, and an N₂/methane subcooling MR) each condense/precool through the previous stage's cold box before their own JT expansion — the same cross-stage coupling TEALARC uses, one level deeper. Natural gas is cooled 300 K → 255 K → 175 K → 112 K across the three multi-stream exchangers before letdown to LNG storage (~114 K). All three circulations are set via tear_specs. From the ChemSep casebook (Snohvit MFC).
17 unit ops • PENG-ROBINSON
167 0
View & openEthylbenzene synthesis
Benzene alkylation with ethylene (exothermic, 98% ethylene conversion) followed by a recovery column — 100% EB bottoms. From the ChemSep casebook (AIChE J 57, 655).
6 unit ops • PENG-ROBINSON
167 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
168 0
View & openBTX aromatics train
Benzene / toluene / p-xylene split in a two-column train — 99+% purity on all three products. From the ChemSep casebook (CScasebook_BTX).
6 unit ops • PENG-ROBINSON
189 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
168 0
View & openTEALARC LNG liquefaction
A simplified Technip TEALARC train: two closed mixed-refrigerant loops — a heavy C₁/C₂/C₃ precool MR that also cools itself in a 4-stream exchanger, and a light N₂/C₁/C₂/C₃ liquefaction MR — bring natural gas to 120 K before letdown to storage (LNG at ~115 K). Both circulations are set via tear_specs; the precool MR runs rich for pinch feasibility (screening fidelity). From the ChemSep casebook (TEALARC).
13 unit ops • PENG-ROBINSON
167 1
View & openFour-stage cascade (≈−190 °C)
Propylene → ethylene → methane → nitrogen cascade reaching ≈81 K — four coupled closed loops, the full ChemSep cascade ladder (Refrigeration_4-Stage-190C). Air-separation-grade cold from stacked vapor-compression cycles.
13 unit ops • PENG-ROBINSON
166 0
View & openThree-stage cascade (−150 °C)
Propylene → ethylene → methane cascade to −150 °C: each colder loop condenses against the next-warmer loop’s evaporator. From the ChemSep casebook (Refrigeration_3-Stage-150C).
10 unit ops • PENG-ROBINSON
167 0
View & openTwo-stage cascade (−100 °C)
Propylene + ethylene cascade: the ethylene loop condenses inside a heat exchanger against the evaporating propylene loop and serves a −100 °C load. Two coupled closed cycles. From the ChemSep casebook (Refrigeration_2-Stage-100C).
7 unit ops • PENG-ROBINSON
167 0
View & openPropylene refrigeration (−50 °C)
The same propylene loop pulled to −50 °C by sub-atmospheric evaporation (0.8 bar) — COP drops as the lift grows. From the ChemSep casebook (Refrigeration_Propylene-50C).
4 unit ops • PENG-ROBINSON
166 0
View & openPropylene refrigeration (−30 °C)
Closed propylene cycle for −30 °C process cooling — the workhorse olefin-plant refrigerant. From the ChemSep casebook (Refrigeration_Propylene-30C).
4 unit ops • PENG-ROBINSON
164 0
View & openGas-condensate LNG train: condensate, LPG and LNG
The LNG plant that is also a liquids plant, at real capacity: this is one 4.4 Mtpa train (a two-train plant is two of these), not a scaled-down sketch. A condensate-rich field arrives by trunkline as a two-phase stream: the slug catcher drops ~20 mol% of it out as raw condensate before a single molecule reaches the cold end, and the plant then runs two trains side by side off one feed. Liquids: the raw condensate is let down to an MP flash that strips the dissolved methane (without it the stabilizer's shortcut total condenser tries to condense methane at 8 bar, which is not a real stabilizer overhead), then stabilized to a C₅/C₆ product. Gas: sweetened and dried, chilled to 245 K to knock out an NGL cut, and the NGL demethanized and split by a deethanizer / depropanizer / debutanizer sequence into commercial propane (~98 mol%) and butane (~98 mol%) LPG plus a natural-gasoline bottoms. LNG: the lean gas goes to the same APCI C3MR cold end as the 'c3mr-lng-liquefaction' showcase — propane precool, mixed-refrigerant MCHE to 120 K, JT letdown to a 1.5 bar end-flash drum. Five sold products come out of one flowsheet, each a stream the solver computed. Watch the end-flash boil-off: it leaves at ~13 mol% nitrogen against 1 mol% in the feed, because the flash drum is where an LNG train actually rejects its nitrogen — nobody specified that, the flash found it. Dehydration is the real molecular-sieve bed, not a stand-in: a 4A sieve sized by length-of-unused-bed, which is what actually takes the gas to the <=0.1 ppmv the cold box needs — 95 t of sieve on a 5.5 x 5.5 m bed, a 17.5 h cycle and 1.4 MW of regeneration duty, with 0.47 bar of Ergun pressure drop. The AGRU spec is checked against the physics rather than assumed: 99.9% CO₂ removal leaves 33 ppmv, and at the coldest point in the train (115.9 K) the solid-CO₂ solubility limit is 232 ppmv on the measured-data basis — a 7x margin, so the sweetening spec demonstrably clears freeze-out instead of merely looking tight.
35 unit ops • PENG-ROBINSON
51 1
View & openLNG front end and storage: guard beds, tank boil-off, driver limit
The parts of a 5.2 Mtpa LNG train that are not the cold box, and the four questions they answer that no bulk unit can — at real capacity, so the vessel sizes and duties are ones an engineer can check against their own plant. Guard beds: a sulfur-carbon bed takes mercury from 200 to 0.01 µg/Nm³ — the brazed-aluminium limit, because mercury attacks the plate-fin cold box by liquid-metal embrittlement — on a 4.8 m x 6.6 m bed with 4.2 years of life from a capacity balance — inside the 3-5 year window these non-regenerable beds are actually replaced on, which is what a turnaround plan needs. A 4A molecular sieve then dries the gas to 0.1 ppmv, the only route to a cryogenic water spec (a glycol contactor tops out near a −30 °C dew point), on a 4.9 m x 5.1 m bed running a 13.8 h cycle for 1.3 MW of regeneration duty. Storage: the LNG goes to a tank whose boil-off rate comes from a 0.05%/day guarantee but whose boil-off composition comes from a real equilibrium flash — and that is the interesting part, because the vapour leaves at ~11 mol% nitrogen against 1.1% in the feed. Nitrogen and methane are far more volatile at 113 K, so the boil-off is light and the stored liquid weathers heavier: nobody specified that, the flash found it. Recondensing: the boil-off goes back into the send-out LNG rather than to a flare, and the unit reports the LNG:BOG ratio (1999) against the minimum the energy balance demands (3.8), which is the constraint a terminal is actually operated against. The driver: a gas turbine burning plant fuel gas, rated 97.5 MW at ISO conditions, delivers only 84.5 MW at 35 °C — 5.5 MW short of its 90 MW refrigeration load, and flagged as such. That derate is computed from two physical effects (a fixed-geometry compressor swallows a fixed volume so mass flow follows air density, and hotter air costs more to compress), not from a vendor curve, and it comes out at 0.66%/K — mid-band for industrial machines. It is why a tropical LNG train makes less product in summer.
17 unit ops • PENG-ROBINSON
50 0
View & openC3MR LNG liquefaction
A simplified APCI C3MR train: natural gas and the mixed refrigerant are precooled by a closed propane loop, liquefied to 120 K in a multi-stream main cryogenic exchanger against a closed N₂/C₁/C₂/C₃ refrigerant cycle, then let down to storage — LNG at ~115 K. Single-level precool and a single MCHE bundle (a real train uses three propane levels and two bundles); refrigerant charges are set via tear_specs.
13 unit ops • PENG-ROBINSON
168 0
View & openRefinery sour water stripper (NH₃ + H₂S)
The standard refinery sour water stripper: sour water carrying ammonia and hydrogen sulfide is steam-stripped in a 10-stage column, sending both overhead as sour gas and returning stripped water fit for reuse. Runs on the new sour-water weak-electrolyte package, which is what makes the result meaningful — ammonia and H₂S suppress each other's volatility (ammonia raises pH and holds sulfide down as HS⁻; H₂S lowers pH and holds ammonia down as NH₄⁺), and heat reverses both, which is precisely why a stripper works. The two removals come out asymmetric for the real reason: H₂S strips essentially completely while ammonia, five orders of magnitude more soluble, is the duty that sets the steam rate.
5 unit ops • SOUR-WATER
76 0
View & openCrude distillation (preset cuts)
An atmospheric crude column fractionating a petroleum feed (naphtha → kerosene → diesel → residue) into ordered side cuts — refinery support via pseudos.
6 unit ops • PENG-ROBINSON
169 6
View & openSulfolane liquid-liquid extraction of aromatics
Liquid-liquid extraction of aromatics from a refinery catalytic-reformer stream with sulfolane, after Figure 10.1 of T. Brouwer (PhD thesis, TU Twente, 2021). A countercurrent extraction cascade pulls benzene and toluene preferentially into the sulfolane-rich extract, leaving a methylcyclohexane-rich raffinate.
5 unit ops • NRTL
168 0
View & openSulfolane extractive distillation of aromatics
Extractive distillation recovering benzene and toluene from a stabilized reformate's C₆-C₇ non-aromatics (represented by methylcyclohexane) using sulfolane, after Figure 10.2/10.6 of T. Brouwer (PhD thesis, TU Twente, 2021). A vacuum solvent-recovery column then splits the aromatics from the sulfolane (reported as its own product rather than recycled). Both columns converge (ED 44 iterations, SR 98, residuals ~1e-5): methylcyclohexane leaves overhead at 91.3 mol%, the aromatics product carries no sulfolane at all (0.00000 mole fraction) at 95.2% recovery of the feed's benzene and toluene, and the recovery column returns sulfolane 99.96% pure at 490 K. Both columns were originally mis-specified in the same way, and it is worth seeing once because the symptom looks like a thermodynamic failure rather than an arithmetic one. distillate_to_feed is a fraction of a column's TOTAL feed, and both were set above the amount of light key actually present, so each column was forced to drag its heavy key overhead to make up the flow. The ED asked for 0.15 of 140 mol/s = 21 mol/s of overhead when only 17.5 mol/s of non-aromatics exists, so 3.5 mol/s of aromatics had to come over — that was the 19.4% benzene lost to the raffinate. The recovery column asked for 0.42 of its bottoms against roughly a quarter of it being aromatics, so ~20 mol/s of solvent had to come over — that was the 42 mol% sulfolane in the product. Setting each to the light key's real share (0.125 and 0.265) removes both. The property method is the whole story here, and it is why this example ran unconverged for a long time. Extractive distillation exists because of solvent selectivity, so a cubic with van der Waals mixing rules — Peng-Robinson as this was originally written — cannot represent the one effect the column depends on; it was being asked to converge on a model that did not contain the physics. A plain activity model cannot be used either: sulfolane boils at 558 K, so a reboiler hot enough to strip it drives benzene past its 562 K critical point, where a gamma-phi formulation has no answer at all. What the system needs is both at once, which is exactly what a Ge mixing rule provides — PSRK is a cubic (no supercritical ceiling) whose mixing is driven by UNIFAC (real selectivity). pr-mhv1 converges here too, in 47 iterations.
7 unit ops • PSRK
165 0
View & openMCHT extractive distillation with phenol
Extractive distillation of methylcyclohexane (MCH) and toluene using phenol as the selective solvent, adapted from Tiverios and Van Brunt (Ind. Eng. Chem. Res. 2000, 39, 1614). Phenol raises toluene's relative volatility away from MCH enough to split an otherwise close-boiling pair; a solvent-recovery column then splits toluene from the phenol (reported as its own product rather than recycled).
7 unit ops • PENG-ROBINSON
169 0
View & openPropane dehydrogenation cold box
Propane dehydrogenation (PDH) to propylene over a Pt/Cr catalyst, followed by a cold-box separation recovering liquid propylene from the H₂-rich reactor off-gas, after US Patent 6,333,445 (Chart Inc., 2002). The refrigeration loop itself is not modeled — the cold box is represented here as a net cooling duty to condense the propylene, a bounded simplification. Unreacted propane recycle is not modeled either (reported as its own product stream).
6 unit ops • PENG-ROBINSON
169 0
View & openNatural 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).
10 unit ops • PENG-ROBINSON
169 0
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
166 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
169 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
169 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
167 1
View & openDME synthesis via reactive distillation
Methanol dehydrates to dimethyl ether over the reactive stages of a column — reaction and separation in one shell, pulling DME overhead while unconverted methanol and water leave the bottoms (Peng-Robinson EoS avoids the missing UNIFAC group-decomposition for ethers that blocks this under an activity-coefficient package).
4 unit ops • PENG-ROBINSON
167 0
View & openBTX separation via dividing-wall column
Benzene/toluene/ethylbenzene split into three purified products by a single rigorous dividing-wall column (prefractionator + two coupled main columns) instead of two ordinary columns in series — the thermally-coupled route real DWC retrofits use.
5 unit ops • PENG-ROBINSON
165 0
View & openAssociated gas conditioning
Field gas is compressed, chilled below its dew point, and flashed to knock out NGL/condensate — the sales-gas vs. liquids split every midstream gathering plant runs (Peng-Robinson).
6 unit ops • PENG-ROBINSON
169 0
View & openPerry Ch.13 Example 6: reboiled light-ends stripper
A reboiled stripper removing dissolved light gases (nitrogen, methane through propane) from a heavier liquid, using reboil vapor as the stripping gas, from Chapter 13 of Perry's Chemical Engineers' Handbook.
5 unit ops • PENG-ROBINSON
167 0
View & openPerry Ch.13 Example 5: two-step absorber with intercooling
Two absorption stages in series with intercooling between them (removing the heat of absorption, which otherwise raises K-values and hurts recovery) to maximize LPG recovery, from Chapter 13 of Perry's Chemical Engineers' Handbook.
9 unit ops • PENG-ROBINSON
170 1
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
169 1
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
171 0
View & openPerry Ch.13 Example 2: lean-oil absorber
Simple absorber recovering butane and pentane from a process gas into a lean-oil (n-dodecane) absorbent, from Chapter 13 of Perry's Chemical Engineers' Handbook.
5 unit ops • PENG-ROBINSON
167 0
View & openHydrocracking fractionation train
The standard downstream train a hydrocracker reaction section feeds into: a high-pressure separator knocks the H₂-rich recycle gas off the reactor effluent, a letdown valve drops the liquid to low pressure for a second flash (LPG-range off-gas), then a fractionator (crude_distillation, one side draw) splits what remains into light naphtha, a kerosene/diesel cut, and unconverted oil bottoms. A textbook train topology (Gary & Handwerk-style HP-sep → letdown → LP-sep → fractionator), not a replication of any specific published paper's numbers — the reaction lumps/kinetics are the same illustrative n-paraffin network as the 'hydrocracker-unit' example, not a real assay.
11 unit ops • PENG-ROBINSON
166 1
View & openHydrocracking reaction section
A refinery hydrocracker: heavy VGO (modeled as n-dodecane) plus excess H₂ is cracked over catalyst into lighter products via a discrete lumped first-order kinetic network, then flashed to knock out recycle H₂/light gas from the liquid product (Peng-Robinson). Conversion is set by reactor temperature and LHSV.
5 unit ops • PENG-ROBINSON
167 0
View & openGas 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.
4 unit ops • PENG-ROBINSON
80 0
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