How to simulate btx 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.
Also known as: BTX dividing-wall column, benzene toluene xylene separation.
- 1Open the ready-made model
Open the "BTX separation via dividing-wall column" model in the MaximaLabs workspace — no install, no license. It loads live on the canvas, ready to edit and run.
- 2Confirm the thermodynamics
This process is modeled with the PENG-ROBINSON property package over benzene, toluene, ethylbenzene — already selected, so the phase equilibrium and enthalpy are physically consistent from the first run.
- 3Review the flowsheet
The flowsheet chains DWC. Every block is a real, solvable unit op you can reconfigure on the canvas.
- 4Run the simulation
Click Run. The deterministic solver converges the material and energy balances (recycles included) and fills the live stream table — the AI never invents a number.
- 5Read the results and iterate
Inspect the converged streams, tweak a spec, and re-run — or ask the AI copilot to explain a result or diagnose a failed solve in plain English.
- Thermodynamics
- PENG-ROBINSON
- Components
- benzene, toluene, ethylbenzene
- Unit operations
- DWC
Opens live on the canvas — free, no install.
Explore the model & flowsheetFrequently asked questions
- What does the BTX separation via dividing-wall column model simulate?
- 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.
- Is "BTX separation via dividing-wall column" the same as a BTX dividing-wall column?
- Yes — this model covers what is also called BTX dividing-wall column, benzene toluene xylene separation. It runs the real process on the rigorous solver, so you can size and study it directly.
- Which thermodynamic method does it use?
- The PENG-ROBINSON property package, over benzene, toluene, ethylbenzene — already selected. You can switch the method on the canvas before running.
- Which unit operations are in the flowsheet?
- It chains DWC. Every block is a real, solvable unit operation you can reconfigure, add to, or remove.
- Do I need to install software or buy a license?
- No. BTX separation via dividing-wall column runs entirely in your browser on MaximaLabs — free, no install, no license. Open the model to load it live and run the deterministic solver.
More guides like this
NGL fractionation: single-shell Petlyuk dividing-wall column
A natural-gas-liquids cut (ethane / propane / n-butane) split into three on-spec products by ONE thermally-coupled dividing-wall column instead of two columns in series. This uses the native Petlyuk unit op: a prefractionator whose reflux and boilup are supplied by the main column (the single condenser + single reboiler), solved by an outer Wegstein loop that converges the bidirectional vapor/liquid coupling to self-consistency — the coupling legacy sequential-modular solvers approximate with two connected columns whose recycle fails to converge.
DME 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).
BTX aromatics train
Benzene / toluene / p-xylene split in a two-column train — 99+% purity on all three products. From the ChemSep casebook (CScasebook_BTX).
Reformate 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.
LNG 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.
Gas-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.