A fractional distillation unit separates multi-component liquid mixtures using a vertical fractionating column (Ø100 mm–3 m) containing 5–60 theoretical separation stages achieved by structured packing (Sulzer MellapakTM equivalent), random packing (Pall rings, Raschig rings), or bubble-cap/sieve trays. Achieving column efficiencies of 70–90% HETP, it separates components with boiling point differences as small as 2–5°C at throughputs of 0.5–5,000 kg/h the standard purification technology for pharmaceutical solvent recovery, fine chemical separation, and food-grade ethanol production.
Challenges
Column Flooding at Excessive Vapour Rate
Vapour velocity exceeds liquid down-flow capacity entrainment flooding collapses separation.
Tray Weeping at Low Vapour Rate
Insufficient vapour velocity allows liquid to drip through tray holes theoretical plate efficiency falls.
Fouling of Structured Packing with Viscous or Polymeric Feed
High-viscosity or polymerising feed coats structured packing channels efficiency loss.
High Reflux Ratio Energy Penalty
Required reflux ratio of 5:1 means 5× more energy input than minimum separation energy.
Safe Handling of Flammable Azeotrope Overhead Cut
Flammable enriched overhead composition at condenser outlet requires ATEX design.
Solutions
- Operational Vapour Velocity at 60–75% of Flooding Velocity: Column designed for 75% flooding stable operation with headroom for throughput variation.
- Minimum Vapour Loading Interlock (VFD on Reboiler Duty): VFD on reboiler heating controls minimum vapour rate prevents tray weeping below setpoint.
- Random Packing (Pall Rings) for Fouling-Prone Feeds: Open-structure Pall rings resist fouling easier to clean or replace than structured packing.
- Optimal Reflux Ratio (1.2–1.5 × Minimum Reflux): McCabe-Thiele-based design minimises energy at 1.2× minimum reflux balance of cost vs. purity.
- ATEX Zone 1 Column, Condenser, and Receiver Design: Fully classified electrical equipment; nitrogen blanketing of overhead condenser and receiver.
Applications
- Pharmaceutical: Ethanol purification for pharma-grade alcohol, acetonitrile recovery, solvent upgrade.
- Chemical: Benzene/toluene separation, isomer separation, azeotrope processing.
- Food & Beverage: Food-grade ethanol concentration to 95%, aroma compound isolation, essential oil fractionation.
- Petroleum & Fine Chemical: Light hydrocarbon separation, fine chemical isomer purification.
- Research: Analytical-scale fractional distillation for pure compound isolation and identification.
Models & Capacities
11B — Fractional Distillation Unit (FD) — Ø50 mm Lab to Ø3,000 mm Large Production — 5–60 Theoretical Plates — Throughput 0.1–5,000 kg/h — ΔBP ≥ 2–5°C | |||||||||
Model | Scale | Column Ø [mm] | Height [m] | Theoretical Plates | Throughput [kg/h] | Reflux Ratio | Op. Pressure [bar] | Reboiler Duty [kW] | Overall H [mm] |
FD-LAB-050 | Lab | 50 | 1.0 | 5 – 15 | 0.1 – 1 | 1:1 – 10:1 | Atm – 0.05 | 0.5 – 3 | 3,500 |
FD-PIL-100 | Pilot | 100 | 3.0 | 10 – 30 | 1 – 10 | 1:1 – 10:1 | Atm – 0.05 | 3 – 20 | 7,500 |
FD-PIL-300 | Pilot | 300 | 5.0 | 15 – 40 | 5 – 50 | 1:1 – 8:1 | Atm – 0.05 | 20 – 80 | 12,000 |
FD-PRD-600 | Production | 600 | 8.0 | 20 – 50 | 50 – 300 | 1:1 – 6:1 | Atm – 0.05 | 80 – 300 | 18,000 |
FD-PRD-1500 | Production | 1,500 | 12 | 30 – 60 | 200 – 1,500 | 1:1 – 5:1 | Atm – 0.05 | 300 – 1,200 | 25,000 |
FD-LP-3000 | Large Prod | 3,000 | 18 | 40 – 60 | 500 – 5,000 | 1:1 – 4:1 | Atm – 0.05 | 800 – 4,000 | 35,000 |