Shortcut column Process Flowsheets & Simulations
Explore 2 validated, solved Shortcut column simulation flowsheets in MaximaLabs — real components: methanol, water, acetone. Open any one directly in your browser.
Solved via: NRTL.
Methanol column sized by design spec
A methanol-water column sized by design specification rather than by trial and error — Aspen's Design Spec / SimCentral's Adjust, and a capability that had no curated example despite being solver-native. The column is specified the way a shortcut (FUG) column is: light and heavy keys with their recoveries (98% of the methanol overhead, 2% of the water). What is not specified is the reflux ratio. Instead the flowsheet carries a design_specs entry — vary COL.reflux_ratio until the metric shortcut_n_stages equals 14 — and the solver root-finds it, re-solving the whole flowsheet each trial. Open the Design Spec panel to see it, or the solved result: reflux settles at 1.06 for exactly 14.00 stages. Why that is the interesting question. Reflux and stages trade off against each other, and against energy. Left at the initial 1.6, this separation needs only 10.8 stages but 4.35 MW of reboiler duty; pulled down to 1.06 it needs 14 stages and just 3.49 MW — a 20% energy saving bought with three more trays. A design spec lets you state the column you can afford to build and have the solver tell you how to run it, instead of guessing a reflux ratio and reading off whatever height falls out. The Sensitivity tab comes preloaded with that trade-off as a sweep (reflux ratio against reboiler duty) so the curve behind the single design-spec answer is one click away. **.
4 unit ops • NRTL
79 1
View & openAcetone recovery — batch still vs. continuous column
A spent-solvent stream (60 mol% acetone, 40% water) recovered two ways, so the Analysis panel's Batch distillation (Rayleigh) tool has something to be compared against — it had no curated example, and a batch calculation only means anything next to the continuous alternative. The flowsheet is the continuous answer: a shortcut column recovering 98% of the acetone overhead and rejecting 98% of the water, giving 59.8 mol/s of distillate at high purity for 4.4 MW of reboiler duty. The batch answer (Analysis > Batch distillation). Charge 100 mol of the same mixture to a still and boil it down until the pot falls to 10 mol% acetone: you distil 67.4 mol and the average distillate is only 84.2 mol% acetone. That is the Rayleigh result and it is the whole lesson — a simple batch still has one theoretical stage, so the vapour it makes is enriched but never pure, and the composition drifts the entire time. Reaching column-grade purity in a batch needs reflux and cuts (a batch rectifier), or a second pass. Why the comparison is the point. Batch equipment is cheap, flexible, and right for small or campaign volumes; the column is right when the duty is continuous and purity matters. Having both numbers on the same feed is what makes that a decision rather than a preference. **.
4 unit ops • NRTL
78 0
View & open