Sustainable Aviation Fuel via Alcohol-to-Jet — a PENG-ROBINSON process flowsheet
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.
Modeling assumptions & limitations
- 1All three reaction steps are stoichiometric conversion models (this solver has no ethanol-dehydration, oligomerization, or hydrogenation kinetics specific to these catalysts), and the oligomerization step is lumped to a single representative product (1-decene, 5 C₂H₄ → C₁₀H₂₀) rather than the real broad C₄-C16+ olefin distribution a real oligomerization catalyst produces. The final flash is a light-ends/product split, not a full multi-cut fractionation into light-ends/SAF/diesel bands (this build only makes one heavy product, so there's nothing yet to fractionate into separate SAF and diesel cuts).
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- Rigorous PENG-ROBINSON thermodynamics, solved by the same engine every simulation runs on.
- 3 unit operations modeled: 3× Hydrogenate, 2× Fractionate, MIX.
- Focus areas: SAF, Alcohol-to-Jet, Ethanol dehydration, Oligomerization, e-Fuels.
- Thermodynamics
- PENG-ROBINSON
- Components
- ethanol, ethylene, water, 1_decene, hydrogen, n_decane
- Unit operations
- 3× Hydrogenate2× FractionateMIX
Opens in a new tab, loaded straight into the app — no setup.
Read the step-by-step guideReproduce this exact result from Python — the real client.get_example() → run_and_wait() path, not a mockup.
from flowsim.sdk import FlowSimClient
client = FlowSimClient()
example = client.get_example("saf-alcohol-to-jet")
sim = client.create_simulation(example["title"], example["flowsheet"])
result = client.run_and_wait(sim["id"])
print(result["status"]) # "converged"
streams = client.streams(sim["id"])Related models
CO₂ methanation (e-fuels / power-to-gas)
The Sabatier reaction (CO₂ + 4H₂ ⇌ CH₄ + 2H₂O) converts captured CO₂ and green H₂ into synthetic natural gas at a 97% single-pass-equivalent conversion (real plants stage several adiabatic beds with intercooling to reach this; lumped into one reactor here), then a cooler and knockout drum condense the reaction water from the SNG — the e-fuels loop that closes the loop on captured carbon instead of just storing it.
Ethanol 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.
Renewable 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.
e-Fuels (Power-to-Liquids): rWGS + Fischer-Tropsch
The Power-to-Liquids / e-SAF pathway: captured CO₂ and green hydrogen are converted to synthetic hydrocarbons. A reverse water-gas-shift reactor turns CO₂ + H₂ into CO + H₂O (solved to real chemical equilibrium), the water is knocked out, and the syngas feeds a Fischer-Tropsch reactor that builds a whole hydrocarbon slate via the Anderson-Schulz-Flory chain-growth law. The single knob that sets the product spectrum is the chain-growth probability alpha (here 0.90): a high alpha shifts the slate toward diesel/wax, a low alpha toward LPG/naphtha — the reactor distributes the reacted carbon across n-paraffins C₁..C₈ (the tail lumped as C₈ wax) with exact C/H/O atom balances, so it conserves atoms wherever the distribution is cut.
Ionic liquid breaks the ethanol-water azeotrope
The ethanol-water azeotrope is a wall: at 89.4 mol% ethanol the vapour and the liquid have the SAME composition, relative volatility is 1, and no number of trays gets you past it. This flowsheet walks through it by adding an involatile ionic liquid, [EMIM][BF₄], which binds water preferentially and pulls the two apart. The numbers are the demonstration. NRTL puts the relative volatility at the azeotrope at 0.996 — that is the wall, computed, not asserted. Add the IL and it climbs to 2.10 at 10 mol%, 2.98 at 20%, and 3.66 at 30%. Flash the IL-laden mixture here and the vapour comes off at an ethanol:water ratio of 22.6 against the azeotrope's 8.43 — decisively across. Run the same feed with no IL and there is nothing to separate: the mixture goes straight from all-liquid to all-vapour with no useful two-phase band, which is precisely what an azeotrope means. Why an IL rather than the usual glycol entrainer (see 'anhydrous-ethanol-extractive-distillation'): an ionic liquid has effectively no vapour pressure, so it never contaminates the distillate and it regenerates by flashing rather than by a second column. Bounded, and this is why the example is a flash and not a column: the IL package models the phase behaviour — which is what decides whether an entrainer works — but omits the IL's own pure-component enthalpy, so a rigorous column energy balance is a follow-up. The separation shown here needs only the phase equilibrium. The IL also carries no molar mass in the databank, so mass-basis readouts show a dash; the mole-basis flash is exact.
Polymerization 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.