Expert-level separation processes covering distillation, absorption, extraction, crystallization, membrane separations, and adsorption for chemical engineering applications.
VLE: vapor-liquid equilibrium, Raoults law for ideal systems. Relative volatility: alpha = y1 over x1 divided by y2 over x2. McCabe-Thiele: graphical method for binary distillation design. Operating lines: rectifying and stripping sections defined by material balance. Minimum reflux: infinite stages required, Underwood equation for multicomponent. Efficiency: Murphree tray efficiency accounts for non-ideal stage.
Absorption: gas component transferred to liquid solvent. Operating line: L over G ratio determines separation. Minimum solvent rate: pinch point at equilibrium line crossing. NTU and HTU: number and height of transfer units for packed column design.
Distribution coefficient: ratio of solute concentration in extract to raffinate phase. Selectivity: ratio of distribution coefficients for desired vs undesired solute. Mixer-settler: contacting stage with phase separation. Kremser equation: number of theoretical stages for given separation.
Reverse osmosis: pressure drives water through semipermeable membrane. Ultrafiltration: size exclusion of macromolecules, proteins, colloids. Gas permeation: solution-diffusion mechanism, selectivity from permeability ratio. Concentration polarization: solute buildup at membrane reduces flux.
| Pitfall | Fix |
|---|---|
| Assuming ideal VLE | Use NRTL or UNIQUAC for non-ideal liquid mixtures |
| Ignoring azeotropes | Check for azeotropes before designing distillation sequence |
| Membrane fouling not addressed | Include cleaning protocol and replacement in design |
| Wrong solvent selection for extraction | Screen solvents by selectivity and distribution coefficient |