A large-scale production ANFD scales the standard single-vessel filter-wash-dry concept to filter areas of 4–16 m², processing batch sizes of 500–15,000 kg API or fine chemical per batch in vessels of 4,000–30,000 L working volume. The agitator uses a heavy-duty centre-shaft or counter-rotating dual-blade design, driven by a dedicated high-torque gearbox (11–90 kW) to handle the increased cake mass and higher resistance encountered at full production scale. All containment, jacket heating, and vacuum systems are scaled proportionally.
At large scale, slurry charging uses closed-loop pneumatic transfer or gravity from a crystalliser or reaction vessel above — no manual transfer. The filter plate (sintered SS 316L, 20–60 µm nominal) spans 4–16 m² — equivalent to 25–100 individual 0.16 m² filter press frames in one contained vessel. Filtration and wash cycles are controlled by PLC with automated valve sequencing; drying endpoint is determined by online LOD monitoring via condenser condensate balance or NIR probe. The heavy-duty agitator torque is continuously monitored — rising torque at drying endpoint indicates cake dryness approach.
Challenges
Agitator Torque Overload at High Cake Fill and Dry Endpoint
Full-scale cake mass plus drying-induced compaction creates very high agitator torque — motor overload risk.
Non-Uniform Drying Across Large Filter Area (Centre-to-Edge Gradient)
At 4–16 m² filter area, vapour path length from cake edge to central vapour outlet creates a radial drying gradient.
Filter Plate Integrity Under Cyclic Pressure Differential (Up to 6 bar)
Large filter plates experience high bending stress under cyclic filtration pressure — fatigue cracking at plate support points.
Validation of Wash Uniformity Across 16 m² Cake Surface
Wash solvent distribution uniformity across a 4–5 m diameter cake surface is difficult to validate — impurity removal may be non-uniform.
Heavy-Duty Agitator Seal Change During Campaign Without Vessel Opening
At production scale, agitator seal replacement requires crane-assisted vessel top removal — significant downtime.
Solutions
- Torque-Limited VFD with Auto-Reverse and Speed Step-Down at Threshold: VFD limits agitator torque to rated maximum — auto-reverse and speed reduction prevent motor overload at cake dryness.
- Multiple Radial Vapour Outlets + Perforated Centre Draft Tube: Radial vapour outlets at vessel wall supplement central outlet — equalises vapour pressure across full filter area.
- FEA-Validated Filter Plate Design (316L, 40 mm Thick, Ribbed Underside): Finite element analysis validates plate design for 3:1 safety factor at 6 bar — ribbed underside provides stiffness.
- Wash Distribution System (Annular Ring Distributor + 12-Point Radial Nozzles): 12 evenly-spaced spray nozzles plus annular ring distributor ensure ±5% wash volume uniformity across full cake area.
- Cartridge-Type Mechanical Seal Assembly (Single-Lift Replacement in <4 Hours): Seal cartridge replaces as single unit without crane — swapped from top with vessel sealed; downtime <4 hours.
Applications
- Pharmaceutical (API Production): Large-batch API filtration, washing, and drying — generic, branded, and biosimilar APIs at commercial production scale.
- Fine Chemical (Multi-Tonne Batch): Specialty chemical, dye intermediate, and advanced material filter-wash-dry at 1–15 tonne batch scale.
- Agrochemical: Large-volume active ingredient final isolation — single vessel replaces multiple centrifuges and tray dryers.
- Polymer & Resin: Polymer precipitate filtration, washing, and partial drying before extruder feed — contained, single vessel.
- Inorganic Chemistry: Pigment, catalyst, and metal salt precipitation filtration and drying at production scale.
ANFD Process Parameter Reference by Filter Area
ANFD Process Parameter Reference — Filtration, Washing, and Drying by Filter Area | ||||||||||
Filter Area [m²] | Typical Batch Size [kg] | Filtration Time (Water-Like) [h] | Wash Volume Typical [L/kg] | Drying Time (LOD 30→0.5%) [h] | Filtrate Volume Max [L/h/m²] | Vacuum Drying Temp [°C] | Max Agitator Tip Speed [m/s] | Seal Gas Consumption [Nm³/h] | CIP Time [min] | Discharge Time [min] |
0.04 | 0.5–2 | 0.2–1 | 3–8 | 2–6 | 50 | 40–120 | 0.5 | 0.2 | 20 | 10 |
0.10 | 1–6 | 0.3–1.5 | 3–8 | 2–8 | 50 | 40–120 | 0.5 | 0.3 | 25 | 15 |
0.20 | 2–12 | 0.5–2 | 3–8 | 3–10 | 50 | 40–140 | 0.8 | 0.4 | 30 | 20 |
0.50 | 5–30 | 0.5–2 | 3–8 | 4–12 | 100 | 40–150 | 1.0 | 0.6 | 35 | 25 |
1.0 | 10–60 | 0.5–2.5 | 3–8 | 4–14 | 100 | 40–150 | 1.2 | 0.8 | 40 | 30 |
2.0 | 20–120 | 0.8–3 | 3–8 | 5–16 | 150 | 40–160 | 1.5 | 1.0 | 45 | 35 |
4.0 | 50–250 | 1–4 | 3–8 | 6–18 | 200 | 40–160 | 1.8 | 1.5 | 55 | 40 |
6.0 | 75–380 | 1–5 | 3–8 | 8–22 | 250 | 40–160 | 2.0 | 2.0 | 60 | 50 |
8.0 | 100–500 | 1.5–5 | 3–8 | 8–24 | 300 | 40–160 | 2.0 | 2.5 | 65 | 55 |
10.0 | 125–650 | 1.5–6 | 3–8 | 10–26 | 350 | 40–160 | 2.0 | 3.0 | 70 | 60 |
12.0 | 150–800 | 2–7 | 3–8 | 10–28 | 400 | 40–160 | 2.0 | 3.5 | 75 | 70 |
16.0 | 200–1,100 | 2–8 | 3–8 | 12–32 | 500 | 40–160 | 2.0 | 4.5 | 90 | 85 |
20.0 | 250–1,400 | 2–9 | 3–8 | 12–36 | 600 | 40–160 | 2.0 | 5.5 | 100 | 100 |