Phosphoric acid concentration: microwave heating (29 → 54% P2O5) — a STEAM process flowsheet
The same duty with the steam exchanger replaced by volumetric microwave heating: 42.6 MW absorbed in the acid, then the same vacuum flash to 54.0 wt% P₂O₅ and the same 64.0 t/h of water removed — the microwave does not remove water, it supplies the latent heat. At a 65% wall-plug magnetron efficiency (915 MHz industrial units reach ~85%) that is 65.5 MW of electricity, 1,640 kWh per tonne of P₂O₅ (1,250 at 85%). The comparison that decides it is the energy carrier, not the heating mechanism: at Jorf Lasfar the baseline's 1.76 t/t of steam is a co-product of the sulfuric-acid plants, and the site turns that steam into electricity at roughly 30%. Sending it through a turbine, a magnetron and back into the acid delivers about a fifth of the heat the exchanger delivers directly (0.30 × 0.65 ≈ 0.2), so on this site the microwave route needs roughly five times the primary steam energy of the baseline. Where microwaves do earn their place is not here but at the superphosphoric end (>70% P₂O₅, viscous, fouling, where the recent literature targets them), and an electric route for the 29-54 step should be compared against mechanical vapour recompression, which reuses the latent heat at a coefficient of performance of 10-30. Sweep the absorbed duty to see the product concentration and the electricity follow it. Model scope, stated up front. No property package in the tree can flash aqueous phosphoric acid honestly: the databank carries no heat capacity for H₃PO₄, NRTL has no binary and no UNIFAC groups for it, and the cubic equations of state give a boiling-point elevation of the wrong sign and an enthalpy flash that vaporised most of the feed from a 1 MW input. So this is the water-side model on IAPWS steam tables: the streams carry the acid's water only, and the 55.2 t/h of H₃PO₄ (40.0 t/h as P₂O₅) ride along as a non-volatile spectator in the mass balance the user variables compute. What that gets right is what the comparison turns on — the water removed and its latent heat, exact from IAPWS. What it leaves out, and by how much: the acid's own boiling-point elevation (tens of kelvin at 54% P₂O₅ — 85 wt% acid boils at 158 °C at atmospheric pressure — so the real acid runs 20-30 K hotter than these flash temperatures and the 320 K feed here stands in for a hotter plant feed), and the acid's sensible heat (of order 5% of the latent duty). Both move the temperatures, not the energy-carrier comparison. Microwave penetration depth (about a centimetre in a conductive acid at 2.45 GHz) and the HF attack on quartz windows are equipment questions this model does not carry.
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- Rigorous STEAM thermodynamics, solved by the same engine every simulation runs on.
- 2 unit operations modeled: MW, Flash.
- Focus areas: Phosphoric acid, Microwave, Electrification, Vacuum flash, Comparison study.
- Thermodynamics
- STEAM
- Components
- water
- Unit operations
- MWFlash
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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("phosphoric-acid-concentration-microwave")
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
Phosphoric acid concentration: steam evaporator baseline (29 → 54% P2O5)
The conventional wet-process step, at the scale of one Jorf Lasfar concentration line: 138 t/h of 29% P₂O₅ acid, heated by 3.5 bar LP steam in a graphite exchanger and flashed under vacuum (0.12 bar) to 54% P₂O₅, evaporating 64.0 t/h of water. The steam feed is tuned so the concentrate lands on 54.0 wt% P₂O₅ (the user variable p2o5_wt_product), which takes 70.4 t/h of steam — 1.76 t steam per tonne of P₂O₅, 42.6 MW of condensing duty. That is the single-effect ideal; the published plant benchmark of ~2.8 t/t carries exchanger approach, losses and off-design operation on top. The point of the number here is what it costs the site: at Jorf Lasfar this steam is a co-product of the exothermic sulfuric-acid plants, which is the fact any electric alternative has to beat. Compare the two sibling examples, phosphoric-acid-concentration-microwave and -hybrid. Model scope, stated up front. No property package in the tree can flash aqueous phosphoric acid honestly: the databank carries no heat capacity for H₃PO₄, NRTL has no binary and no UNIFAC groups for it, and the cubic equations of state give a boiling-point elevation of the wrong sign and an enthalpy flash that vaporised most of the feed from a 1 MW input. So this is the water-side model on IAPWS steam tables: the streams carry the acid's water only, and the 55.2 t/h of H₃PO₄ (40.0 t/h as P₂O₅) ride along as a non-volatile spectator in the mass balance the user variables compute. What that gets right is what the comparison turns on — the water removed and its latent heat, exact from IAPWS. What it leaves out, and by how much: the acid's own boiling-point elevation (tens of kelvin at 54% P₂O₅ — 85 wt% acid boils at 158 °C at atmospheric pressure — so the real acid runs 20-30 K hotter than these flash temperatures and the 320 K feed here stands in for a hotter plant feed), and the acid's sensible heat (of order 5% of the latent duty). Both move the temperatures, not the energy-carrier comparison. The water heated at 1 atm here reaches its 1-atm boiling point in the exchanger; the real acid is kept liquid under static head and flashes in the chamber.
Phosphoric acid concentration: microwave-then-steam hybrid (29 → 42 → 54% P2O5)
The transition path the concept proposes: microwaves take the acid from 29 to 42% P₂O₅ in a first vacuum flash (28.6 MW absorbed), a pump returns the 42% acid to atmospheric pressure, and the existing steam exchanger and second flash finish it to 54.0 wt% — 23.2 t/h of steam (0.58 t/t) plus 1,100 kWh of electricity per tonne of P₂O₅ at 65% magnetron efficiency, the same 64.0 t/h of water removed in total. The split is not free: two-thirds of the latent duty moved from a co-product steam to purchased electricity, and nothing about the second stage got easier. What a hybrid does buy is a pilot that can be run beside the existing evaporator without betting the line on it, and the freedom to put the microwave stage where it has a case — the viscous, fouling end — rather than on the dilute feed. Compare phosphoric-acid-concentration-steam and -microwave. Model scope, stated up front. No property package in the tree can flash aqueous phosphoric acid honestly: the databank carries no heat capacity for H₃PO₄, NRTL has no binary and no UNIFAC groups for it, and the cubic equations of state give a boiling-point elevation of the wrong sign and an enthalpy flash that vaporised most of the feed from a 1 MW input. So this is the water-side model on IAPWS steam tables: the streams carry the acid's water only, and the 55.2 t/h of H₃PO₄ (40.0 t/h as P₂O₅) ride along as a non-volatile spectator in the mass balance the user variables compute. What that gets right is what the comparison turns on — the water removed and its latent heat, exact from IAPWS. What it leaves out, and by how much: the acid's own boiling-point elevation (tens of kelvin at 54% P₂O₅ — 85 wt% acid boils at 158 °C at atmospheric pressure — so the real acid runs 20-30 K hotter than these flash temperatures and the 320 K feed here stands in for a hotter plant feed), and the acid's sensible heat (of order 5% of the latent duty). Both move the temperatures, not the energy-carrier comparison.
Aniline 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.
Ethylene glycol plant: closed water loop + multi-effect evaporator dehydration
The water-integrated evolution of the fiber-grade MEG plant. Two changes turn the once-through EO/glycol chain into a real, water-economical process: (1) the recovered process water is RECYCLED back to the hydration reactors through a purge splitter. A pure recycle is inventory-singular (reactors are keyed on the shrinking EO pool, so water consumption is fixed regardless of how much water circulates), so an 8% purge pins the loop and makes it well-posed, cutting fresh water makeup from 10 to ~1.75 mol/s (a >80% reduction). (2) The bulk dehydration is done by a genuine TWO-EFFECT EVAPORATOR TRAIN (forward-feed, real steam economy: effect 1's low-temperature vapor is the heating steam for effect 2) doing rigorous (P,H)-flash water removal, rather than a single spec-based split. The recycle converges through the solver's Wegstein tearing (~15 outer passes) and MEG still comes out fiber-grade (>=99.9%). HONEST SCOPE: the reaction chemistry is rigorous stoichiometry (real atom balances, ~90/9/1 selectivity) and the evaporators are real energy-balanced flash effects — but flash evaporation CANNOT reach glycol dryness without slipping glycol into the overhead vapor (MEG has a real vapor pressure at 90 C), so the evaporators run cool and only pre-concentrate. An overhead knockout returns the ~1-2% slipped glycol to the product (no yield loss), and a final vacuum-refining polish (still a spec-based split, representing the refluxed dehydration column a flash cannot replicate) removes the last water. This mirrors a real MEG plant's multi-effect-evaporator + vacuum-refining dehydration section. The product columns remain spec-based (a converged 99.9% fiber-grade MEG column is not tractable under Peng-Robinson here — the MEG/DEG relative volatility is too narrow for the wide-boiling MESH path).
Pressure-swing ethanol dehydration (Gᴱ mixing rule)
Ethanol–water is the classic azeotrope, and pressure-swing distillation breaks it without an entrainer: the azeotrope moves with pressure, so a low-pressure column and a high-pressure column pass each other's azeotropic distillate and each recovers a pure product. The whole process only works if the property package tracks that shift — which is exactly where a conventional package choice falls between two chairs. This flowsheet runs the high-pressure column at 15 bar on pr-mhv1: Peng-Robinson with an MHV1 excess-Gibbs mixing rule, so the cubic equation of state gets its attraction parameter from NRTL's excess Gibbs energy instead of from a single binary interaction constant. Switch the thermo package (Solver menu) and compare the predicted azeotrope: | package | 1 atm | 15 bar | valid at 15 bar? | |---|---|---|---| | NRTL | 0.891 | 0.802 | no — γ-φ is a low-pressure formulation (~10 bar) | | Peng-Robinson (kij) | 0.586 | 0.613 | yes, but a kij cannot represent this azeotrope | | pr-mhv1 | 0.949 | 0.798 | yes | (mole fraction ethanol; the repo's DECHEMA-validated 1 atm anchor is 0.894.) At 15 bar pr-mhv1 lands within 0.005 of NRTL while remaining a genuine equation of state, whereas plain Peng-Robinson is off by ~0.19 and puts the azeotrope in the wrong place entirely. Selecting nrtl here also trips the applicability guard, which warns that the activity model is past its pressure ceiling and names the fix. The flowsheet demonstrates the mechanism on itself. Drop the column pressure to 1 atm and re-run, changing nothing else: the solve fails with SPEC_THERMODYNAMICALLY_IMPOSSIBLE, because at atmospheric pressure the requested bottoms purity sits beyond the azeotrope and no column can reach it. At 15 bar the same specification converges and the bottoms leaves at x_EtOH ≈ 0.924 — past the atmospheric azeotrope of 0.894, which is precisely the composition an atmospheric column cannot cross.
Industrial water reuse: RO + membrane distillation to near-ZLD
A chemical-site water-reuse train of the kind large industrial water users build when the intake is salinising and freshwater is getting scarce: reverse osmosis makes reuse-grade water, the RO concentrate is warmed by low-grade waste heat and pushed further by membrane distillation, and the MD concentrate is crystallised to salt. Overall water recovery comes out at 94.9%. The point of the flowsheet is why MD is there at all. RO is pressure-driven, so its ceiling is osmotic pressure — and this feed hits that wall hard: at 25 bar the same 75% recovery is infeasible, and the model says so with a number rather than a shrug (osmotic pressure 27.2 bar against a 25 bar feed, a structured SPEC_THERMODYNAMICALLY_IMPOSSIBLE error, which is why the feed here runs at 45 bar). Membrane distillation is driven by a vapour-pressure difference instead, so only vapour crosses and there is no osmotic ceiling at all: it takes the RO concentrate from 2.0 mol% to 9.7 mol% salt, recovering 81% of the water RO had to leave behind, and its distillate is solvent-only. The waste-heat coupling is not decoration. At the RO concentrate's own 25 C the MD flux is about 1 kg/m2/h and the module is pointless; warmed to 60 C it runs at 21.5 kg/m2/h, inside the 10-50 kg/m2/h band real DCMD modules achieve. That is the entire commercial case for MD — it is a heat-driven process, so it is only cheap where low-grade heat is already being vented.