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Strategies to Minimize Springback in Briquette Production
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Material Preparation
Moisture Control: Maintain 8–12% moisture for biomass (lignin activation) or <5% for metal powders. Excessive moisture causes expansion; too little reduces natural binding.
Particle Size Distribution: Use <3 mm particles with 20–30% fines (e.g., sawdust) to fill voids and limit rebound.
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Binder Optimization
Natural Binders: For biomass, exploit lignin plasticity by pre-heating to 80–100°C.
Synthetic Binders: Add 2–5% starch, molasses, or lignosulfonate to metal/coal powders for cohesion.
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Press Parameters
Compression Force: Apply gradual pressure (e.g., 2-stage compression) to allow particle rearrangement. Target 100–150 MPa for biomass, 200+ MPa for metals.
Dwell Time: Hold pressure for 3–10 seconds to relax material stresses.
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Tooling Design
Die Geometry: Use tapered dies (1–3° angle) to ease ejection and reduce expansion. Longer compression zones improve density uniformity.
Surface Finish: Polish die walls to Ra <0.8 μm for lower friction-induced rebound.
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Post-Processing
Curing: For binder-based briquettes, cure at 60–80°C for 2–4 hours to stabilize bonds.
Cooling Control: Avoid rapid cooling (induces thermal stress cracks).