A continuous twin-screw wet granulator (TSG) uses two co-rotating intermeshing screws (200–1,200 RPM) inside a heated barrel to simultaneously convey, wet, and granulate powder fed continuously at 1–1,000 kg/h. With residence times of 5–60 seconds, it enables real-time PAT monitoring, rapid response to formulation changes, and direct integration into continuous solid dosage manufacturing lines — fully compliant with ICH Q13 continuous manufacturing guidance for pharmaceutical solid dosage production.
Powder blend is dosed gravimetrically into the twin-screw barrel; binder liquid is injected through dedicated barrel wall ports. The co-rotating screws convey and knead the wet mass through kneading and conveying elements — their configuration determines shear intensity and residence time distribution (RTD). Granules exit continuously and feed directly into an inline continuous fluid bed dryer. NIR and Raman probes at barrel exit monitor granule size and moisture in real time for automated process control.
Challenges
Screw Configuration Optimisation for Each Formulation
Kneading element angle and sequence must be re-optimised per new formulation — DoE required.
RTD Broadening at Scale-Up
RTD widens with barrel diameter — reduces in-process blend uniformity at larger throughputs.
Binder Maldistribution at High Powder-to-Liquid Ratio
Insufficient mixing before first kneading zone leaves unmixed dry powder regions.
PSD Sensitivity to Screw Speed and Feed Rate Variation
±5% screw speed causes ±15–20% D50 shift — tight VFD and gravimetric control essential.
Start-Up and Shut-Down Product Loss
Non-steady-state material must be diverted — continuous yield loss 1–5% per start/stop cycle.
Solutions
- DoE-Based Screw Configuration Library per API Class: Pre-validated screw configurations for hydrophilic, hydrophobic, and plastic API families.
- RTD Tracer Studies at Each Scale (UV Tracer + Inline Spectroscopy): RTD characterised at pilot; scale-up corrects throughput to maintain equivalent RTD width.
- Multiple Liquid Injection Ports (3–5 Along Barrel Length): Distributed liquid ensures full wetting of powder before first kneading zone.
- Closed-Loop Screw Speed and Feed Rate Control (RTD PID, ±1%): RTD model-based control maintains mass balance — adjusts screw speed to feed rate variation.
- Automated Divert Valve at Barrel Exit: Auto-divert during start/stop routes non-steady-state material to segregated waste — yield protected.
Applications
- Pharmaceutical (Continuous Mfg): ICH Q13 continuous solid dosage — direct integration with continuous FBD and tableting.
- Nutraceuticals: High-throughput continuous supplement granule production with minimum batch footprint.
- Chemical: Continuous specialty chemical granule production — consistent quality at high volume.
- Food Processing: Continuous instant beverage and functional food granule production.
- Research & Development: Small-scale continuous granulation for rapid formulation screening — minimal API use.
Models & Capacities
1D. Twin-Screw Wet Granulator (TSG) — Models & Capacities | ||||||||||
Model | Screw Ø [mm] | Throughput [kg/h] | Screw Speed [RPM] | Barrel L [mm] | Liquid Ports | Residence Time [s] | Motor [kW] | Overall L [mm] | Overall W [mm] | Overall H [mm] |
TSG-LAB-16 | 16 | 1–10 | 200–1,200 | 400 | 2 | 5–30 | 1.5 | 600 | 300 | 500 |
TSG-PIL-18 | 18 | 5–30 | 200–1,200 | 500 | 3 | 5–40 | 3.0 | 750 | 380 | 600 |
TSG-PIL-24 | 24 | 15–80 | 200–1,000 | 700 | 3 | 5–50 | 5.5 | 1,000 | 480 | 750 |
TSG-P-36 | 36 | 50–200 | 200–900 | 1,000 | 4 | 10–60 | 11 | 1,400 | 600 | 900 |
TSG-P-50 | 50 | 100–400 | 200–800 | 1,400 | 4 | 10–60 | 22 | 1,900 | 780 | 1,100 |
TSG-P-70 | 70 | 200–600 | 200–600 | 1,800 | 5 | 15–60 | 37 | 2,400 | 950 | 1,300 |
TSG-LP-90 | 90 | 300–1,000 | 150–500 | 2,200 | 5 | 20–60 | 75 | 3,000 | 1,200 | 1,600 |