Binary Distillation for Process & Chemical Engineering

Review mass transfer to build a foundation for binary distillation, and quickly cover tt x y diagrams, easy drop concepts, and the difference between partial pressure and vapor pressure.

Explore the ideal gas model and its assumptions, including elastic collisions and frictionless motion. Relate pressure, volume, and temperature using PV = nRT for gas and vapor behavior.

An ideal solution assumes similar or negligible interactions, yielding linear properties like density, boiling points, and vapor pressure; requires similar size and structure.

Vapor pressure is the pressure exerted by a vapor in equilibrium with its condensed phase at a fixed temperature in a closed system, rising with temperature as kinetic energy increases.

Partial pressure is the pressure contribution of each gas in a mixture; Dalton's law says total pressure equals the sum of these partial pressures for ideal gases.

Study vapor-liquid equilibrium where vapor pressure balances gas-phase pressure, varying with temperature. Explore how composition affects liquid and vapor concentrations and apply Raoult's, Dalton's, and Henry's laws to relate phases.

Explore Raoult’s law for binary distillation, linking component partial pressures to their mole fractions and pure-component vapor pressures, and examine ideal gas and ideal solution assumptions, low-pressure behavior, and deviations.

Define flux as rate of transport of species per unit area normal to transport, referenced to fixed frame, linking it to concentration gradients and mass transport by bulk flow velocity.

Introduce Ja, the diffusion flux, and a reference velocity. Subtract the reference velocity from the material velocity to obtain the true diffusion flux, illustrated with a pipe example.

Use convection to model mass transfer when diffusion or fixed-law approaches fail; employ correlations with mass transfer coefficients and concentration differences, guided by Grashopper's number and Prandtl numbers.

Maximize interfacial area and residence time in gas–liquid dispersion, improving mass transfer between gas and liquid through bubble columns, spray towers, and packed columns.

The spray column in absorption disperses liquid into fine droplets to maximize gas-liquid contact, with upward gas flow and downward liquid flow, producing cleaner exit gas.

Explore bubble column operation where gas forms bubbles in a liquid, creating a liquid phase with high contact area for mass transfer, while highlighting the drawback of high pressure drop.

Explore packed columns for gas–liquid contact, using random or structured packing to increase surface area and contact time, and learn design and calculations for absorption equipment.

Explore the tray column design, including gas and liquid flow, various tray types such as bubble caps and sieve trays, and the concept of equilibrium stages in absorption.

Analyze counter-current gas-liquid contact in absorption, contrast cocurrent flow, and trace solute transfer from the gas phase to the liquid, driven by gravity and density differences affecting mass transfer.

Explore single-stage and multi-stage absorption, assessing gas–liquid interactions, tray towers, and counter-current versus co-current flow to optimize gas scrubbing and stage efficiency.

Explore tray columns for binary distillation, where each tray provides gas x and liquid y contact and an equilibrium stage to drive mass transfer.

Sieve trays use a perforated flat metal sheet to allow gas-liquid contact; liquid may whip through holes at low vapor, while high flow reduces contact, offering a simple, low-cost design.

Investigate valve trays in binary distillation, where liquid weight moves valves to regulate gas and liquid flow, offering a wide operating range and maintenance considerations.

Bubble cap trays use a slotted cap on a central riser to direct gas up and liquid through annular gaps, with a built-in liquid seal at low flow rates.

Explore the three tray types, spacing and sizing guidelines, common layouts and materials, the purpose of a man way, and typical maintenance and cost considerations for tray design.

Explore tray spacing in a distillation column, focusing on the typical 24 inch spacing for space and maintenance, while noting that increasing spacing raises column height, cost, and safety concerns.

Explore how tray sizing in distillation depends on diameter, including hole design, tray thickness, and internals, with diameter influencing height, stages, and emitter as the course scope.

Explore tray layouts in binary distillation, focusing on counterflow trays, single-pass design, and the tradeoffs of multi-pass columns for diffusion, convection, and efficiency.

Trays are typically made of stainless steel for strength, inertness, and corrosion resistance to avoid reactions with gas, solid, and liquid phases.

This lecture explains tray manways, showing maintenance is done by a person inside the unit to clean and add materials, with one manway per three passes and restricted access.

Explore bubble cap trays with a positive liquid seal, operating at very low gas flow rates, and compare them to simpler, cheaper sieve trays and their operating ranges and costs.

Explore tray pressure drop in binary distillation when gas flows against liquid or requires compression, and how tray design, diameter, and height influence the pressure drop.

Compare the costs of different tray types, noting seed trays are cheap while bubble cap trays are the most expensive due to sizing, fit, and installation requirements.

This lecture explains maintenance of distillation trays, with emphasis on bubble cap trays, detailing when to perform cleaning, the challenges of fouling and clogging, and the costly service requirements.

Identify the three tray types, noting that the cheapest trays suit most applications and low vapor flow, while avoiding bubble caps due to high cost and maintenance.

Explore the role of trays in a distillation column, and how upward gas flow and downward liquid flow enable gas-liquid interaction on each tray.

Explore the bubbling area where gas-liquid interactions in crossflow create turbulent foaming, increasing interfacial area and driving mass transfer between gas and liquid.

The lecture analyzes the contact area between liquid and paper, defines the disengagement space, and explains how tray spacing reduces droplets and improves tray efficiencies.

Explore how a weir on distillation trays maintains a desired liquid level, affecting tray pressure drop and mass transfer efficiency, with notch types and typical heights.

Design and size the downcomer to ensure smooth liquid flow, prevent flooding and choking, and provide adequate disengagement time for column operation.

Explore stage efficiency in binary distillation by comparing real and theoretical mass transfer, and learn methods to predict and assess whole-column efficiency.

Murphree's efficiency measures the actual separation achieved on each tray by the ratio of concentration change to equilibrium change, assuming well-mixed liquids on the tray and downcomer.

Analyze how liquid and gas flow rates drive damping, priming, dumping, and fluting in column operation, and how proper downcomer flow prevents flooding and maldistribution.

Explore tray diameter in binary distillation, showing how column cross-sectional area controls gas superficial velocity and pressure drop, with correlations for surface tension, foaming, and perforation area.

Understand how tray spacing shapes the design of a binary distillation column. Relate diameter, 2 m; spacing 0.6 m; and 10 trays to real stages and a 6 m height.

Explore how pressure drop arises in tray distillation columns, from friction, liquid holdup, and surface tension, and review head loss and typical ranges like 0.3 to 1 kPa.

Analyze dry sieve pressure drop in trays, considering gas velocity, perforation diameter, tray thickness, density changes along the column, and dilute vs concentrated liquid density.

Calculate hl, the equivalent height of clear liquid holdup on a tray, and estimate the pressure drop using ksak and clc with h_w and superficial gas velocity.

Explore head loss from surface tension in gas–liquid flow, where bubbles form and cause a pressure drop, depending on gravity, liquid density, perforation diameter, and surface tension.

Explore six absorption column operation regimes governed by gas and liquid flow—normal operation, flooding, priming, Koning condition, weeping, dumping; the best operation resembles a bubble or foam formation.

Explore the normal case of column operation with correct liquid and gas flow rates to prevent weeping, leakage, or flooding, and maximize gas-liquid interaction across trays.

Flooding in column operation arises from excess liquid flow and pressure drop, causing liquid accumulation and reduced tray efficiency, with loading and flooding velocities guiding design to avoid reverse flow.

Priming raises gas flow to carry liquid droplets upward, increasing liquid hold-up and contact time for mass transfer, though it can indicate design issues and is not routinely recommended.

Explain how coning occurs when gas flow rate or pressure is high relative to liquid flow velocity, causing poor gas-liquid interaction at perforations.

weeping is leakage through tray holes caused by low gas velocity and insufficient pressure, allowing liquid to pass through openings; increase gas flow rate to reduce leakage.

Examine dumping operation where low gas flow causes liquid to accumulate and weep through tray holes, risking flooding. Adjust gas and liquid flows, using the Weber number as a guide.

Compare packed columns and tray columns, explaining differential contact versus stage-wise interaction, and highlight cost, materials, pressure drop, and suitability for corrosion, foaming, and thermal changes.

introduces packings for gas–liquid contact, emphasizing inert, non corrosive, and strong materials with high surface area; compares random packings, Tuku packing, and grid packings, and stresses replaceability and flow balance.

Assess packing materials for distillation: metal packings offer strength and durable liquid contact; plastics are inexpensive but have limited wetting; ceramics resist high temperatures but are brittle.

Stacked packing alters flow in the column, improving gas and liquid distribution while reducing pressure drop and flow path length.

Explore random packing in a distillation column, where randomly arranged packings enable gas-liquid contact for separation. See examples like Russian rings and the spread of liquid across column packing.

Explore structural packing in distillation, featuring repeating units designed for smooth flow; it lowers pressure drop, increases efficiency per unit volume, and enhances liquid-gas transfer capacity, at a higher cost.

Explore how column internals, including liquid redistributors and distributors, ensure even liquid distribution while the vortex breaker and impingement baffle prevent droplets and flooding.

Describe how a liquid distributor spreads liquid evenly across trays and packing, using gravity or pressure to reduce maldistribution and create multiple streams similar to sparging devices.

Learn how liquid/vapour redistributors insert intermediate liquid feeds to improve distribution between packed sections in tall distillation columns, ensuring even liquid flow and better vapor-liquid contact.

Use a demister or mist eliminator at the top of the column to remove droplets from the gas, keeping overhead gas clean and allowing liquid to be recovered as product.

Learn how vapour distributors feed gas at the bottom and distribute it evenly through the column via small pipes, with chimney trays and packing rings providing support.

Explore the role of a vortex breaker in a distillation column, preventing vortex formation and pool buildup by redirecting liquid flow into a controlled stream toward the bottom.

Packing supports prevent downward migration of packing pieces and ensure open area for unrestricted liquid and vapor flow, with corrugated supports commonly fixed in place to maintain size.

Identify how hold-down plates and bed limiters retain packing in a distillation column, limit bed size, and prevent packing from shifting under high gas flow.

Explore the top of the distillation column, including liquid outlets, baffles, and gravity-driven condensate that fills sections before moving to the product line, while vapor outlets remain simpler.

Explore the middle column structure, noting feed placement at the fifth stage, dunkleman dropouts, and chimney trace for collection and vapor redistribution, with attention to pressure drop and column height.

Analyze bottom column structure in binary distillation, focusing on liquid management, bottom sump and baffle arrangements, impingement plates, and how flooding and corrosion influence nozzle sizing and flow control.

Design a benzene–toluene distillation to achieve high benzene recovery using minimum stages, determine feed tray location, and compute actual stages with 1.5× minimum stages, including efficiency and final purities.

Learn modeling of a WKS RadFrac distillation for C3 and iC4 separation with recycle, focusing on stage design, pressure drop, and achieving up to 99.96% recovery with a condenser.

Explore column internals, comparing trays and packings, and examine how column height, diameter, and pressure drop affect flooding and separation for water and methanol feeds.

This lecture demonstrates sensitivity analysis on a RadFrac distillation, showing how changing feed stages, reflux ratio, and column pressure impacts methanol-water separation, purity, and distillate flow.

Dive into top unit operations Q&A, covering pump curves, heat and mass transfer, reactor engineering, hazop basics, condensers, distillation versus reactors, and practical design questions.