Aim of the Experiment
To study the operation of a distillation column, to determine tray efficiency using the McCabe-Thiele graphical method, and to study the effect of reflux ratio on product composition and column performance.
Apparatus Required
- Distillation column (sieve tray or bubble cap column)
- Reboiler with heater and temperature controller
- Condenser with cooling water supply
- Reflux divider / splitter
- Refractometer or hydrometer (for composition measurement)
- Thermometers / temperature sensors at each tray
- Sampling ports at feed, distillate, and bottoms
Theory
Distillation is a separation process based on differences in volatility (boiling points) of components in a liquid mixture. In a distillation column, vapour rises up the column and liquid flows downward. At each tray, vapour and liquid come into contact and approach equilibrium — the more volatile component (MVC) concentrates in the vapour phase.
Reflux Ratio: R = L/D, where L is liquid returned to the column (reflux) and D is distillate product flow.
Operating Line (Rectifying section): y = [R/(R+1)] × x + x_D/(R+1)
McCabe-Thiele Method: Graphical construction on a vapour-liquid equilibrium (VLE) diagram. Theoretical trays are stepped off between the equilibrium curve and operating lines. Tray efficiency = (actual trays) / (theoretical trays needed).
Murphree Tray Efficiency: E_mv = (y_n − y_{n+1}) / (y*_n − y_{n+1})
Procedure
- Charge the reboiler with a known feed mixture (e.g., ethanol-water, 30–40% ethanol by volume).
- Switch on the heater. Set the reflux ratio to a known value (e.g., R = 3).
- Allow the column to reach steady state (approximately 45–60 minutes). Monitor temperatures at each tray — they should stabilise.
- Collect samples from the distillate and bottoms outlets.
- Measure compositions (mole fractions) of distillate (x_D) and bottoms (x_B) using a refractometer or calibrated hydrometer.
- Draw the McCabe-Thiele diagram: plot VLE curve, rectifying operating line, stripping operating line, and step off theoretical trays.
- Calculate overall column efficiency: E_o = N_theoretical / N_actual.
- Repeat for a different reflux ratio (e.g., R = 5) and compare distillate composition and efficiency.
Observation Table
| Parameter | Run 1 (R=3) | Run 2 (R=5) |
|---|---|---|
| Feed composition x_F (mole fraction) | ||
| Distillate composition x_D | ||
| Bottoms composition x_B | ||
| Reboiler temperature (°C) | ||
| Distillate temperature (°C) | ||
| Theoretical trays (McCabe-Thiele) | ||
| Actual trays | ||
| Overall efficiency E_o (%) |
Result
Overall tray efficiency at R = 3: E_o = _______%. At R = 5: E_o = _______%. A higher reflux ratio gives purer distillate but reduces column capacity and increases energy consumption. The McCabe-Thiele construction confirms the number of theoretical stages required.
Internal Links
Related: Process Engineering Lab Equipment | Process Engineering Lab Setup Guide | Dissolution Apparatus Experiment | Instruments in Chemistry Lab
Get Process Engineering Lab Equipment
Scientico India manufactures ISO 9001:2015 and CE-certified process and chemical engineering lab apparatus including distillation columns, heat exchangers, and fluid handling systems.
Scientico India manufactures this and the full range of Process Engineering equipment — CE-certified and supplied to engineering colleges worldwide.
Explore Process Engineering Equipment → or request a quoteLab Equipment Featured in This Guide
Manufactured in-house by Scientico India — ISO 9001:2015 & CE certified, exported to 60+ countries. Request a CIF quote within 24 hours.
Multi-Purpose Teaching Flume (Length 10 m) | FluidoSurge-X 248View details & get quote →
Gas Turbine Jet Engine | ThermoFlux – 7086View details & get quote →
Vibration of Spiral Spring Apparatus | Vibrano X – 03View details & get quote →
Pipe Surge and Water Hammer Apparatus | FluidoSurge-X 324View details & get quote →
Air Flow Reaction Turbine | ThermoFlux – 7093View details & get quote →
Orifice Discharge Apparatus | FluidoSurge-X 128View details & get quote →