A falling film evaporator distributes feed liquid as a thin continuous film down the inner wall of vertical heated tubes — gravity draws the film downward while steam condenses on the outer shell side. Processing 500–200,000 kg/h evaporation duty at temperature differences of 5–25°C, it achieves gentle evaporation with product residence times below 60 seconds — the standard configuration for heat-sensitive food, pharmaceutical, and chemical concentration duty.
Feed liquid enters the top tube sheet through a distribution system — each tube receives an equal liquid load that spreads into a circumferential film. Vapour generated within the falling film exits co-currently downward into the vapour-liquid separator at the tube bottom. A central vapour outlet discharges vapour to the condenser while concentrated liquid recirculates or exits as product. Multiple passes reduce solids content progressively. Evaporation capacity scales directly with effective heat transfer area.
Challenges
Uneven Liquid Distribution Across Tube Bundle
Maldistribution creates dry patches and overheating — localised product degradation and fouling.
Fouling at Low Wetting Rate in Concentration Service
As viscosity rises near evaporation endpoint, film breaks and tubes run partially dry.
Limited Viscosity Range (<500 cP at Operating Temperature)
Film stability collapses above 500 cP — product pools at tube base rather than filming.
Foaming from Surface-Active Components in Feed
Foam breaks liquid film continuity — reduces heat transfer and causes vapour-side carry-over.
Scaling from Inverse Solubility Salts (CaSO₄, CaCO₃)
Inverse solubility salts crystallise preferentially on heated tube surface — progressive scaling.
Solutions
- Precision Distribution Tray (±5% Film Uniformity per Tube): Calibrated overflow notch or spray nozzle distribution maintains equal liquid load per tube.
- Minimum Wetting Rate Control (PLC Feed Flow Interlock): Feed pump maintains liquid rate above critical wetting threshold — prevents tube dry-out.
- Pre-Heating to Reduce Viscosity Before Entry: Feed preheated to reduce viscosity below 200 cP at tube entry — restores film stability.
- Anti-Foam Dosing System (10–100 ppm Silicone Defoamer): Inline dosing suppresses foam — maintains film continuity in protein and detergent-containing feeds.
- Acid Clean-in-Place (HNO₃ 2%, 70°C, 30 min): Scheduled CIP cycle dissolves scale deposits — restores design U-value between campaigns.
Applications
- Food & Beverage: Milk and dairy concentration, fruit juice evaporation, glucose syrup, beer wort concentration.
- Pharmaceutical: API solution concentration, solvent removal, fermentation broth gentle concentration.
- Chemical: Caustic soda concentration, organic acid evaporation, polymer solution concentration.
- Nutraceuticals: Plant extract, herbal concentrate, vitamin solution gentle evaporation at reduced temperature.
- Environmental: Landfill leachate evaporation, wastewater concentration, black liquor pulp evaporation.
Models & Capacities
Falling Film Evaporator — Models & Capacities | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
Model | Scale | Evaporation Capacity [kg/h] | Heating Area [m²] | Tube Length [mm] | Tube Count | Tube Ø [mm] | Steam Temp [°C] | Vacuum [mbar] | Max Viscosity [cP] | Installed Power [kW] | Overall H [mm] | Weight [kg] |
FFE-LAB-01 | Lab | 5–50 | 0.1 | 1,500 | 3 | Ø25 | 60–120 | 50–500 | <200 | 0.37 | 3,500 | 180 |
FFE-LAB-05 | Lab | 20–200 | 0.5 | 2,000 | 6 | Ø25 | 60–130 | 30–500 | <300 | 0.75 | 4,500 | 380 |
FFE-PIL-2 | Pilot | 100–1,000 | 2 | 3,000 | 9 | Ø38 | 60–140 | 20–500 | <400 | 2.2 | 6,500 | 1,200 |
FFE-PIL-5 | Pilot | 300–2,500 | 5 | 3,000 | 18 | Ø38 | 60–140 | 20–500 | <400 | 4.0 | 7,000 | 2,500 |
FFE-P-010 | Production | 600–5,000 | 10 | 4,000 | 25 | Ø50 | 60–140 | 10–300 | <400 | 5.5 | 8,500 | 5,000 |
FFE-P-025 | Production | 1,500–12,000 | 25 | 5,000 | 40 | Ø50 | 60–140 | 10–300 | <500 | 11 | 10,500 | 11,000 |
FFE-P-050 | Production | 3,000–25,000 | 50 | 6,000 | 55 | Ø50 | 70–150 | 10–300 | <500 | 18.5 | 12,500 | 22,000 |
FFE-P-100 | Production | 6,000–50,000 | 100 | 6,000 | 106 | Ø50 | 70–160 | 10–300 | <500 | 37 | 14,000 | 45,000 |
FFE-LP-200 | Large Prod | 12,000–100,000 | 200 | 7,000 | 148 | Ø63 | 80–170 | 10–200 | <500 | 55 | 17,000 | 90,000 |
FFE-LP-400 | Large Prod | 25,000–200,000 | 400 | 8,000 | 200 | Ø63 | 80–180 | 10–200 | <500 | 90 | 20,000 | 180,000 |
Â