Distillation columns : Principles , Operation & Design

Explore distillation fundamentals, including vapor–liquid equilibria, volatility, and boiling points, and examine industrial distillation columns, instrumentation, and control loops. Model and optimize column performance with process simulations.

Discover distillation fundamentals through thermodynamics and vapor liquid equilibria, learn principles of operation, and explore process control loops and equipment construction, aided by Aspen Plus simulations and downloadable resources.

Distillation separates liquid or vapor mixtures by heating and condensation, exploiting components with lower boiling points. The course covers distillation column construction and operation for industrial separations.

Classify distillation processes by mode, composition, method, and equipment—batch vs continuous, binary vs multi-component, rectification, stripping, and fractionation—alongside trays, packing, and vapor–liquid equilibria.

Investigate the limits of distillation by examining closed boilers, distributed keys, and AISI drops, then assess how these thermodynamic problems affect separation and mass transfer operations.

Explore how successive vapor liquid equilibrium steps separate a multi-component feed by volatility, yielding a distillate of A and B and a bottom stream of C, D, E, and F.

Explore how distillation columns achieve separation via countercurrent liquid and vapor flow, vapor-liquid contact, and external and internal reflux, distinguishing rectification and stripping sections.

Explore how a distillation column uses gravity, heat transfer, and perforated trays with bubble caps to separate light and heavy components, employing downcomers, side draws, reflux, and reboiling.

Explore how intimate vapor–liquid contact in the distillation column condenses heavier components and vaporizes lighter ones, using perforated trays or packing backings to improve separation.

Understand the vapor-liquid equilibrium of pure components as a prerequisite for distillation column operation, with practical examples and graphics to reinforce concepts before tackling mixtures.

Explore vapor–liquid equilibrium in distillation, where liquid and vapor phases exchange mass through vaporization and condensation, driving phase contact in the boiler and condenser.

Explore vaporization of butane at constant pressure, distinguishing sensible heat, latent heat of vaporization, and the progression from saturated liquid to saturated vapor.

Explain the condensation of a pure component at constant pressure, illustrating saturation at 80.8 degrees Celsius, latent heat of condensation, and the vapor-to-liquid transition in distillation contexts.

Under constant pressure, pure components vaporize and condense at the same temperature, the boiling point for that pressure, and at one atmosphere this is the normal boiling point.

Explore how a pure component's boiling point rises with pressure, illustrated by butane data and its vapor pressure curve, linking vaporization and condensation across pressures.

Explore the vapor pressure curve of pure components, read the curve to determine boiling points, and identify the vapor zone, liquid zone, and vapor-liquid equilibrium.

Examine the vapor pressure curve of water at 0.5 atm and 20 °C to show heating at constant pressure moving from liquid to vapor, with bubbles forming on the curve.

Demonstrate vapor-liquid equilibrium using vapor pressure curves, with propane data at 20–40 C and 8.3–13.5 atm; analyze dew point in boiler as it cools from 150 C to 100 C.

Explore flash vaporization of a pure component at constant temperature by lowering pressure to meet the liquid-phase vapor pressure on the curve.

The enthalpy of vaporization is the energy to turn a liquid into vapor, dependent on temperature, while the heat of condensation is its opposite at the same temperature.

Propane experiments at increasing pressure show rising boiling points, converging liquid and vapor properties, and a heat of vaporization nearing zero, defining the critical point where phase boundaries vanish.

Explore how to read and apply the enthalpy diagram for a pure component to perform thermal and material balances in distillation columns, including heat calculations for reflux and reboiling.

Analyze the propane enthalpy diagram, distinguishing saturated liquid and vapor regions, noting the critical point at 97 degrees Celsius and how pressure affects the superheated vapor lines.

Use an enthalpy diagram to determine heat required to raise one kilogram of propylene at 30 atm from 20 C to 130 C, tracing liquid, vaporization, and superheated vapor.

Demonstrate ethylene-ethane fractionation by determining reflex drum pressure from ethylene vapor pressure at -25 degrees Celsius (21.8 atm) and relate overhead and bottom pressures to their respective temperatures via vapor pressure curves.

Assess reboiler operation under three steam pressures by determining condensing temperatures from the water vapor pressure curve, and apply this to boiler pressure drops in a distillation column.

Explore vaporization of a hydrocarbon mixture at constant pressure, identifying bubble point and dew point, and transitions from saturated vapor to superheated vapor driven by sensible heat.

We learn that vaporization at constant pressure creates a vapor-liquid equilibrium between bubble point and dew point, with subcooled liquid and superheated vapor, and liquid fraction rising toward bubble point.

Explore vapor-liquid equilibrium by tracing the bubble and dew curves across pressures, revealing liquid, partially vaporized, and superheated zones with hydrocarbon examples.

Determine vessel pressure for vapor–liquid mixtures by two cases: negligible vapor fraction uses bubble point pressure, while significant vapor uses operating temperature and vapor molar refraction.

Apply Raoult's law to compute the mixture's vapor pressure from component vapor pressures and liquid fractions, as shown with propane and butane giving 5.94 atmospheres.

Apply Dalton's law to determine vapor phase composition from vessel pressure and partial pressures, calculating propane and butane molar fractions and their split in the vapor.

Apply the equilibrium coefficient to predict how feed components split between vapor and liquid in distillation and flash separators, based on operating temperature, pressure, and component vapor pressures.

Learn to use a graphical equilibrium coefficient chart to predict distillation splits, drawing lines at 30 degrees Celsius and 1 atmosphere to classify ethane as overhead and octane as bottom.

Explore how distillation uses volatility differences and relative volatility (alpha) to identify the more volatile component, predicting separation efficiency via vapor pressures at near-constant pressure.

Separate propane and lighter components from butane using columns with over 80 stages. Note the relative volatility between ethylbenzene and xylene is about 1.06, signaling challenging separations.

Increasing operating pressure in a distillation column and flash separator lowers relative volatility, reducing separation capability and enriching bottom liquid with volatile components while the overhead vapor gains heavier components.

Practice hydrocarbon flash separation at 13 bar. Achieve 30 percent overhead and 70 percent bottom using heater, pump, and valve with control to 79 degrees Celsius and 13 bar.

Use vaporization curves to determine the percent vaporized at temperature and pressure in a distillation column, then maintain the target vaporization with cooling, a heat exchanger, and a control valve.

Analyze overhead operation of a distillation column, including condenser, reflux drum, and reflux split. Determine operating pressure (4.3 bar) and temperature (56 °C) from vaporization percent and vapor–liquid equilibrium data.

Analyze a flash separator at 74 °C to determine percent vaporization and equilibrium coefficients for ethane, propane, and isobutane; identify cut point and separation line separating light and heavy streams.

Learn the typical distillation column arrangement with countercurrent vapor and liquid flows, including feed stage, rectification and stripping sections, reflux, condenser, boiler, and key control loops.

Examine the depropanizer distillation column in steam cracking, separating propane and lighter hydrocarbons from butane and heavier components at low pressure, with 42 stages and feed at tray 25.

Apply material balance to a distillation column by balancing feed, distillate, and residue flow rates, using the cut point and separation line to define light and heavy fractions.

Explain reflux drum pressure as a function of temperature and overhead vapor composition, distinguishing pure component vapor pressure from mixture bubble-curve intersections; note 20–50 C typical cooling and cryogenic extremes.

The lecture explains why a distillation column maintains a fairly constant pressure despite internal drops, and notes typical values: reflux drum 7 bar and overhead 6.8 bar.

Explore distillation column pressure control through five methods, primarily by manipulating the condenser and reflux drum with cooling water flow and flooded condenser configurations to regulate top composition and pressure.

Explore pressure control for distillation columns, focusing on overhead and reflux drum pressure, valve strategies, and vapor flow through the condenser. Learn split-range and differential-pressure controllers for fast regulation.

Explore overhead composition control in distillation columns using reflex rate, reflex ratio, and distillate rate; examine reflex control valves, reflux effects on temperature, and maintaining set points with controllers.

Explore alternative control strategies for distillation columns, including pressure, overhead and bottom rate, and composition control, across configurations with partial condensers and reflux drum dynamics.

Set up a simple thermal balance for a distillation column by classifying feed and boiler as in and distillate, residues, and condenser as out, neglecting small losses.

Explore the condenser thermal balance for overhead vapor, linking heat duty to latent heat of condensation and overhead flow, and define the reflex ratio for distillate and external reflux.

Discover the optimum reflux ratio and its trade-off with stage count, where total costs minimize by balancing fixed costs of larger equipment against operating costs from increased heat and utilities.

Explore the flow rate profiles of liquids and vapors in a distillation column, detailing reflux, feed effects, external reflux, distillate, and boiler-based vapor flow.

Explore temperature and component concentration profiles in binary distillation, linking equilibrium temperatures to vapor and liquid compositions at constant pressure, and using binary vapor-liquid equilibrium diagrams to predict column behavior.

Explore concentration profiles of a five-component feed (A–E) in a distilling column, showing light components rising overhead, heavy components descending, and intermediates C and D peaking at tray temperatures.

Explain how temperature depends on molar composition and pressure, link dewpoint to overhead product composition, bottom bubble point to bottom product composition, and show temperature rising from top to bottom.

Introduces the basic equipment of a distillation column—vertical shell for separation, packing internals, boiler for vaporization, condenser, reflux drum, and feed, product handling, and control instrumentation.

The distillation shell is a vertical cylindrical column that encloses the internals, condenser, and reflux drum. It provides feed, vapor, reflux connections and outlets for overhead vapor and bottom product.

Explore how trays in distillation columns enable gas-liquid contact in trade towers, using bubble cap trays and downcomers in the active zone to promote vapor bubbling and heat transfer.

Explore tray arrangements in distillation columns, including cross flow, reverse flow, split flow, and radial flow, and how liquids travel top to bottom.

Explore tray types in distillation columns, including bubble cap trays, trays with perforated holes, and valve trays, and see how liquid level and gas flow affect vapor liquid contact.

Explore packed towers where liquid trickles down packing while gas rises, achieving vapor-liquid separation with high interfacial surface and inert materials. Contrast random and regular packings, noting cost and throughput.

Design packing supports to maximize vapor distribution with open space, minimal flow restriction, and weight-bearing capacity, using bar grids or specially designed supports that create separate vapor and liquid passageways.

Ensure proper liquid distribution at the top of the distillation column for effective mass transfer, avoiding spray nozzle entrainment. Use perforated pipe distributors or redistributors for large towers.

Collector trays manage liquid between bagged beds, enabling draw off and redistribution for cooling in absorbers before the next bed, with types for varying vapor liquid flow rates.

Apply packing restrainers to prevent expansion of the packed bed and keep the top surface level, acting as bed delimiters for random as well as directorate packing.

Explore the combined tray and packed distilling column internals, from feed device and liquid distributor to random packing, liquid collector trays, redistributor, structure and backing, and valve trays.

Heat the liquid with reboilers to produce vapor at the bottom, using steam, heat transfer oils, or hot fluids, with jacketed, table heat exchanger, or cattle-type boilers.

The condenser condenses vapor from the Gullane top, collects condensate in the reflex drum, with some distillate and the rest returned as external reflux by a centrifugal pump.

Learn how to model a distillation column with asprin plus chemical engineering simulation software and assess how feed, temperature, feed stage location, and the reflux ratio affect performance and separation.

analyzes a base case Aspen model of a distillation system splitting propane from butane, exploring how temperature, feed stage location, and the reflux ratio affect the distillate-residue split.

Explore how the reflux ratio affects a distillation column: overhead temperature remains unchanged with pure propane, while the stripping zone cools and lighter components concentrate, per Aspen Plus results.

Analyze how varying feed stage location in a distillation column using Aspen Plus affects temperature profiles and overhead versus bottom products, and the rectification enrichment.

Conduct a sensitivity analysis of feed temperature with the Aspen Plus model, evaluating Gullane temperature profiles, liquid and vapor flow rates, propane and butane concentrations, and plots to interpret results.

Access downloadable resources for distillation columns, covering principles, operation, and design, and gain essential references to support study and practical understanding.

Explore bonus insights into distillation columns, highlighting principles, operation, and design considerations for efficient separation.