engsep covers an undergraduate course in separation processes at the level of Seader, Henley & Roper's
Separation Process Principles and Wankat's Separation Process Engineering: vapour-liquid equilibrium and
azeotropes, flash, binary and multicomponent distillation, absorption and stripping, packed towers and mass
transfer, liquid-liquid extraction and leaching, adsorption and fixed beds, ion exchange and chromatography,
membrane gas separation, reverse osmosis and ultrafiltration, crystallization, drying and evaporation, and
cooling towers - with applications from refining and desalination to pharmaceuticals, biogas upgrading and
sugar. Every method is checked against analytic solutions, published data and internal consistency between
methods, and a course of executed notebooks with worked solutions teaches the ideas.
from engsep import distillation as dist
from engsep import vle
from engsep.vle import y_from_alpha
vle.azeotrope("ethanol", "water")["x"] # 0.885 mol fraction at 1 atm
alpha = vle.geometric_mean_alpha(("benzene", "toluene"), ideal=True) # 2.47
mt = dist.mccabe_thiele(lambda x: y_from_alpha(x, alpha), xD=0.95, xB=0.05, zF=0.45, R=2.0)
mt["stages"], mt["feed_stage"] # (12, 6)
dist.fug(alpha, zF=0.45, xD=0.95, xB=0.05, R_over_Rmin=1.3)["N"] # Fenske-Underwood-Gilliland: 14.3- Validated, not just tested. 140 checks in
docs/VALIDATION.md, rerun in CI: Antoine boiling points against NIST for twenty compounds; the ethanol-water, 2-propanol-water and acetone-methanol azeotropes against published values; the Wilson model against the Gibbs-Duhem equation; Fenske equal to total-reflux stepping and Underwood equal to the McCabe-Thiele pinch; Gilliland against chart readings; the Rayleigh integral against its closed form; stage-by-stage absorbers reproducing Kremser; Colburn's NTU against numerical integration; the Hunter-Nash construction closing its balances with every raffinate on a tie line; MSMPR moments against numerical integration; Bohart-Adams's equal-area time; seawater osmotic pressure; triple-effect evaporation with equal areas; Fuller diffusivities against measurements. - Self-contained. Its own Antoine table (31 compounds) and Wilson parameters (8 binaries), so VLE, psychrometrics and azeotropes need nothing beyond NumPy and SciPy.
- Honest failure modes. A Kremser target that exceeds the absorption factor's limit, a Hunter-Nash construction at or below the minimum solvent, a reflux ratio below the minimum: each raises a clear error instead of returning a number.
- Course data with stated provenance. Literature tables with sources (VLE, permeabilities, solubilities, tie lines) and pseudo-experimental files generated from the library's own models with the noise and deliberate faults documented in each header - and a month of column data that ends in a retrofit proposal.
| Module | Methods |
|---|---|
vle |
Antoine table, Raoult's law, Wilson activity coefficients, bubble and dew points, T-x-y and x-y diagrams, relative volatility, azeotrope location |
flash |
Rachford-Rice for any number of components, bubble and dew points in T and P, adiabatic flash |
distillation |
McCabe-Thiele with q-line, feed-stage location and Murphree efficiency; minimum reflux (with tangent-pinch check) and minimum stages; Fenske, Underwood, Gilliland, Kirkbride and the FUG shortcut; Rayleigh and constant-reflux batch distillation; HETP and O'Connell efficiency |
absorption |
Kremser in all forms, stage-by-stage absorbers, minimum solvent, packed towers by HTU/NTU with numerical and Colburn NTUs, two-film theory |
extraction |
immiscible-solvent single, cross-current and countercurrent stages; a Ternary class on triangular coordinates with the Hunter-Nash construction and minimum solvent; countercurrent leaching |
adsorption |
Langmuir, Freundlich and BET with fitting; batch adsorbers; ideal, Bohart-Adams and Klinkenberg breakthrough; breakthrough analysis and LUB scale-up; PSA balance |
membranes |
gas permeation by complete-mixing and cross-flow models, membrane area; reverse osmosis with coupled water and salt fluxes, recovery limit and concentration polarisation; ultrafiltration gel model; countercurrent dialysis |
crystallization |
solubility table, cooling and evaporative yields with hydrates, supersaturation, MSMPR population balance, moments and mass distribution, kinetics from a CSD, design for a target size |
drying_evaporation |
psychrometrics from the Antoine table, adiabatic saturation and wet-bulb, drying-rate analysis and drying times, single- and multiple-effect evaporators with boiling-point rise |
transport |
Fuller and Wilke-Chang diffusivities, Fick and Stefan fluxes, film and penetration theory, Sherwood correlations, Chilton-Colburn |
datasets |
the bundled literature tables and course data files with their construction |
Eighteen executed notebooks, each with learning objectives, an "Inside the algorithm" section and exercises
(including an "Implement it yourself" task); every exercise has a worked solution in solutions/.
They open in Google Colab and install engsep automatically.
| # | Notebook | Applications |
|---|---|---|
| 00 | Python for separations | Antoine, balances, root finding, x-y diagrams |
| 01 | Phase equilibrium and VLE | Raoult, Wilson, azeotropes, pressure effects |
| 02 | Flash separations | Rachford-Rice, adiabatic flash, NGL |
| 03 | Binary distillation: McCabe-Thiele | operating lines, q-line, efficiency, ethanol-water |
| 04 | Shortcut and multicomponent distillation | FUG, reflux optimisation, a depropaniser |
| 05 | Batch distillation and column efficiency | Rayleigh, batch rectification, O'Connell, flooding |
| 06 | Absorption and stripping | Kremser, minimum solvent, Henry's law and pressure |
| 07 | Packed towers and mass transfer | HTU/NTU, two-film theory, diffusivities |
| 08 | Liquid-liquid extraction | extraction factor, triangular diagrams, Hunter-Nash |
| 09 | Leaching and washing | washing factor, sugar and oilseeds, variable underflow |
| 10 | Adsorption and fixed beds | isotherms, breakthrough, LUB scale-up, PSA |
| 11 | Ion exchange and chromatography | softening, plate theory, resolution, van Deemter |
| 12 | Membrane gas separation | Robeson trade-off, nitrogen generators, biogas |
| 13 | Reverse osmosis and ultrafiltration | desalination, polarisation, gel layer, dialysis |
| 14 | Crystallization | solubility, hydrates, MSMPR, crystal size |
| 15 | Drying and evaporation | psychrometrics, drying curves, multiple effects |
| 16 | Humidification and cooling towers | Merkel's integral, approach, water losses |
| 17 | Project: column data to retrofit | data cleaning, thermodynamic checks, stages and efficiency, a packing retrofit |
Every image is computed by the library; python tools/make_images.py regenerates them.
 Ethanol-water T-x-y diagram: Wilson against data, and the azeotrope |
 The Rachford-Rice function: one monotone equation, one root |
 Kremser: the absorption factor decides what stages can do |
 Hunter-Nash construction on real tie-line data |
 Fixed-bed breakthrough: data, Bohart-Adams and the ideal shock |
 MSMPR crystal size distribution and its mass density |
pip install "engsep @ git+https://github.com/ktwyw/engsep"
# or, for development (adds sympy and the notebook tooling used by the validation suite):
git clone https://github.com/ktwyw/engsep && cd engsep && pip install -e ".[dev]"| Reference | What is checked | Agreement |
|---|---|---|
| Analytic solutions and identities | Fenske vs total-reflux stepping, Underwood vs the pinch, Rayleigh closed form, Kremser in all forms, Colburn, MSMPR moments, van 't Hoff, exchanger-analogy dialysis, shrinking limits of every model | exact to 1e-8 |
| Published data | NIST boiling points (20 compounds, within 1 K), ethanol-water VLE and azeotropes (Perry, Gmehling), Gilliland chart readings, saturation humidity, psychrometric wet-bulb, Fuller and Wilke-Chang diffusivities, seawater osmotic pressure | 0.5-5 %; 25 % for Wilke-Chang |
| Internal consistency | McCabe-Thiele vs Gilliland, flash at bubble and dew points, Hunter-Nash balances and tie lines vs Kremser on a near-immiscible system, Bohart-Adams equal-area time vs the stoichiometric time, triple-effect areas and vapour balance, cross flow vs complete mixing at vanishing cut | 1e-6 to 1 % |
| Recovery from noisy data | isotherm parameters, drying-curve critical moisture and rate, MSMPR kinetics from a CSD, Wilson-vs-Margules on VLE data | within stated tolerances |
If engsep helps your work, please cite it using CITATION.cff.
Yanwei Wang - personal open-source project. GitHub @ktwyw · ORCID 0000-0002-8488-9833 · wangyanwei@gmail.com
Also by the author: engmath, engstat, fluidmech, engrheo, engthermo, engcolloid, engdiscrete and engreact.
MIT - see LICENSE. Contributions welcome: see CONTRIBUTING.md.