Thermal (non-catalytic) HDA — broad aromatics feedstock — a PENG-ROBINSON process flowsheet
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) = k0*exp(-Ea/RT)C_tolueneC_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 benzene → 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: the reactor's external duty, which an adiabatic reactor must have at zero, comes out at about 0.03% of the heat its reactions release (checked by its test, 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.
353 views 0 forks
- Rigorous PENG-ROBINSON thermodynamics, solved by the same engine every simulation runs on.
- 9 unit operations modeled: MIX, Furnace, RX, Quench, 2× SEP2, Recycle Split, Recycle COMP, Letdown, COL.
- Focus areas: Hydrodealkylation, Thermal cracking, Multi-reaction kinetics, Benzene, Recycle loop, Purge, Fired heater.
- Thermodynamics
- PENG-ROBINSON
- Components
- toluene, o_xylene, benzene, biphenyl, h2, methane, h2s, co2, ammonia
- Unit operations
- MIXFurnaceRXQuench2× SEP2Recycle SplitRecycle COMPLetdownCOL
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("thermal-hda-broad-feedstock")
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
Toluene 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).
Ammonia synthesis loop (Haber-Bosch, ChemSep casebook)
The classic industrial ammonia loop: fresh syngas joins recycled unconverted gas, reacts over an equilibrium reactor (N₂ + 3H₂ ⇌ 2NH₃) at synthesis conditions, is chilled to condense high-purity liquid ammonia, and the remaining vapor splits into a recycle (back to the loop) and a purge — the purge exists specifically to bleed off the inert argon a single-pass reactor could never consume, which would otherwise concentrate in the recycle forever.
Benzene 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.
LNG 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.
DAP granulation loop: pre-neutralizer, ammoniating granulator, scrubbers
Diammonium phosphate at the scale of one Jorf Lasfar (JESA) granulation train: 40.2 kg/s (145 t/h) of wet-process phosphoric acid is neutralised by ammonia in two steps and granulated in a loop that recycles four times its own product. The acid carries the composition Handley (IFA, 1984) gives for a commercial merchant-grade acid, per 100 g: 54.82 g H₃PO₄ (39.7% P₂O₅), 3.90 g H₂SO₄, 5.68 g of metal and fluoride impurities (carried as one inert lump) and 35.60 g water. It is pumped first through the tail-gas scrubber and the pre-scrubber, which take back the ammonia the reactors do not absorb, then into the pre-neutralizer, which holds a mole ratio NH₃:H₃PO₄ of 1.44 at 114 °C (near the ratio of highest ammonium phosphate solubility, so the least water keeps the slurry fluid) and boils off water with its own reaction heat. The slurry is sprayed onto the rolling bed of the ammoniating granulator, where sparged ammonia lifts the ratio to 1.845. New solid layers onto the recycled granules (an equal-thickness growth law on the full size distribution), the bed is dried to 3% moisture, a double-deck screen splits it at 3.35 and 1.70 mm, the oversize is crushed, and fines, crushed oversize and 73% of the on-size go back to the granulator. The rest is cooled and sold. The 73% is the split that puts the loop at the recycle ratio Handley reports, 4: a plant sets its recycle to absorb the slurry's water, so here it is an input, not a prediction. Solved: 33.7 kg/s of product (121 t/h), 18.7% N and 47.6% P₂O₅ on a dry basis, above the 18-46-0 commercial grade, which is set by the acid's sulfate and impurities rather than by the 21.2-53.8 of pure DAP. Consumption per tonne of product is 0.227 t NH₃ and 0.474 t P₂O₅. An 18-46-0 product carries 0.219 t of NH₃ as nitrogen and 0.46 t of P₂O₅ per tonne by its grade alone; the difference is this product's richer grade and the ammonia lost at the stack. The recycle ratio is 4.0, and the loop converges on its own tear machinery (six tears, Wegstein). The pre-neutralizer releases 19.1 MW of reaction heat and evaporates 7.3 kg/s of water; the granulator releases 6.9 MW and evaporates 5.2 kg/s; the dryer takes 1.7 kg/s more for 7.1 MW. 0.029 kg/s of ammonia leaves the stack, 0.4% of what is fed, which is what two scrubbers at 90% recovery each give.
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.