Vertical Raw Mills (VRMs) are widely used in the cement and mining industries for grinding raw materials like limestone, clay, slag, and other additives into fine powders. They are energy-efficient alternatives to traditional ball mills and offer better drying capabilities when integrated with hot gas sources.
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Key Features of Vertical Raw Mills:
1. Grinding Mechanism
– Uses rollers and a rotating table to crush and grind materials under pressure.
– Typically has 2-4 rollers that apply hydraulic pressure to the grinding bed.
2. Drying Capability
– Hot gases (from kiln exhaust or auxiliary heat sources) pass through the mill, drying raw materials while grinding.
3. Energy Efficiency
– Consumes 30-50% less energy compared to ball mills due to efficient grinding mechanics.
4. Compact Design
– Takes up less space than horizontal ball mills.
5. Adjustable Fineness
– Particle size can be controlled by adjusting roller pressure, airflow, and separator speed.
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Main Components of a Vertical Raw Mill:
1. Grinding Table – Rotates to disperse material under rollers.
2. Rollers – Apply pressure to crush and grind material.
3. Classifier/Separator – Separates fine particles from coarse ones, recycling oversize material.
4. Drive System – Includes motor, gearbox, and hydraulic system for roller pressure.
5. Hot Gas Inlet – Provides heat for drying moist raw materials.
6. Mill Housing & Foundation – Supports the structure and dampens vibrations.
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Advantages Over Ball Mills:
✔ Lower power consumption
✔ Better drying efficiency (can handle up to 20% moisture)
✔ Smaller footprint
✔ Quieter operation
✔ Easier maintenance (modular roller replacement)
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Common Manufacturers & Models:
– Loesche (LM series) – Pioneers in VRM technology
– FLSmidth (OK Mill) – High-efficiency design
– Polysius (RM series) – Robust construction
– Atox (by FLSmidth) – Compact and reliable
– Ube (UM series) – Japanese engineering
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Typical Applications:
– Cement production (raw meal preparation)
– Coal grinding in power plants
– Mineral processing (phosphate, gypsum)
– Slag grinding for blended cements
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