The moisture requirements of roller extrusion granulators for materials need to be determined based on a combination of material type, equipment parameters, and process objectives. The specific standards are as follows:

Core Moisture Range

• General Recommendation: Material moisture is typically controlled within the 10%-20% range. This interval balances forming quality and equipment stability. Moisture levels below 10% may cause loose particles and reduced yield, while levels above 20% can lead to roller sticking, die hole blockage, and post-drying deformation.
• Adjustments for Special Materials:
  • Organic Materials (e.g., livestock manure, biomass): Due to viscous components, moisture can be relaxed to 15%-25%, but should avoid exceeding 30% to prevent severe sticking. For example, fresh cow manure (60%-80% moisture) requires pretreatment to 30%-40% before granulation.
  • Inorganic Materials (e.g., fertilizers, mineral powders): Moisture must be strictly controlled within 5%-10%, as higher levels exacerbate powder caking and equipment wear.
  • Highly Hygroscopic Materials (e.g., herbal extracts, starch residues): Environmental humidity (workshop relative humidity ≤65%) and anti-caking agents must be managed to prevent sticky masses clogging screens.

Key Influencing Factors

• Material Properties: Particle size distribution (recommended 80-120 mesh), viscosity, and water absorption directly affect moisture thresholds. Coarse particles (>2mm) require higher pressure or moisture for bonding; excessive fines reduce flowability.
• Equipment Parameters:
  • Roller Pressure: Viscous materials (e.g., chicken manure) need 8-10 MPa; less viscous materials (e.g., straw powder) require 10-12 MPa.
  • Speed & Gap: High-moisture materials require reduced speed (10-12 r/min) to extend extrusion time. Excessively small roller gaps cause sticking; overly large gaps weaken pellet strength.
  • Temperature Control: Granulation zone temperature should be 40-60°C. Higher temperatures risk microbial inactivation (e.g., organic fertilizers); lower temperatures impair flowability.
• Post-Processing: Drying temperature/time must align with moisture levels—over-drying causes cracking; insufficient drying leads to excess moisture. Cooling stabilizes structure; sieving removes fines/powders.

Operational Optimization Recommendations

• Pretreatment: High-moisture materials can be dried via sun exposure, ovens, or solar dryers; low-moisture materials may be humidified with water or binders (e.g., 3%-5% starch).
• Dynamic Adjustment: Adjust moisture based on real-time pellet strength and yield feedback—e.g., increase moisture slightly if pellets are fragile; reduce moisture and clean rollers if sticking occurs.
• Maintenance: Regularly inspect roller wear, bearing lubrication, and drive systems to prevent equipment failures from exacerbating moisture issues. Clean die holes to avoid residue affecting subsequent batches.

Summary: Moisture control requires tailoring to material properties and equipment conditions. Pilot testing is recommended to determine optimal parameters, supplemented by in-line monitoring (e.g., moisture sensors, pellet strength testing) for precision control, ensuring efficient production and high-quality granulation.