Ethylene glycol plant: closed water loop + multi-effect evaporator dehydration — a PENG-ROBINSON process flowsheet
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).
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- Rigorous PENG-ROBINSON thermodynamics, solved by the same engine every simulation runs on.
- 7 unit operations modeled: 5× COND Water, 5× RXN3, 2× Cool1, Condense, 5× DEG COL, 2× Evap2, Water Split.
- Focus areas: Ethylene glycol, MEG, Water recycle, Multi-effect evaporator, Steam economy, Fiber-grade.
- Thermodynamics
- PENG-ROBINSON
- Components
- ethylene, oxygen, ethylene_oxide, co2, water, ethylene_glycol, diethylene_glycol, triethylene_glycol
- Unit operations
- 5× COND Water5× RXN32× Cool1Condense5× DEG COL2× Evap2Water Split
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Reproduce 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("ethylene-glycol-closed-loop")
sim = client.create_simulation(example["title"], example["flowsheet"])
result = client.run_and_wait(sim["id"])
print(result["status"]) # "converged"
streams = client.streams(sim["id"])