A large hydrated lime (calcium hydroxide) producer in Iran mainly supplies products for water treatment, construction materials, food additives, and metallurgical desulfurization. The customer’s original process, based on a traditional Raymond mill combined with a cyclone separator, suffered from several limitations:
- Final product D50 only 25–30 μm, unable to meet high-end market demand for ultrafine powder (D50 ≤ 10 μm)
- Low fine powder yield (< 10 μm particles accounted for only 15–20%)
- High energy consumption, severe dust emissions, and frequent maintenance
- With increasing exports to European and Middle Eastern premium markets, requirements for particle size consistency and whiteness became increasingly stringent
Project Requirements
The customer clearly defined the following targets:
- Final product D50: 10 μm ± 1 μm
- D97 ≤ 30 μm (to eliminate oversized particles)
- Capacity ≥ 2 t/h (based on hydrated lime)
- Whiteness ≥ 92% (to avoid graying caused by over-grinding)
- Equipment must be alkali-corrosion resistant and suitable for long-term continuous operation
Episch poeder Technical Solution Design
Considering the physical characteristics of hydrated lime, the engineering team selected a high-precision Air Classifying Mill (ACM) system, which integrates mechanical grinding and centrifugal classification in one unit.
Key process features:
- Closed-loop circulation system:
A negative-pressure collection system ensures dust-free operation and full compliance with local environmental regulations. - High-precision classifier wheel:
To achieve the strict 10 μm target, the system precisely controls the classifier wheel speed through a variable-frequency drive, ensuring an accurate cut point. - Secondary air adjustment:
The system introduces filtered, dry air into the classification zone to effectively disperse agglomerated particles and improve classification efficiency. - Wear-resistant design:
For continuous industrial operation, both the grinding rotor and classifier blades are made of wear-resistant stainless steel.
Project Results
After on-site commissioning and continuous operation, the system demonstrated excellent stability and performance:
| Parameter | Customer Requirement | Actual Result |
|---|---|---|
| Particle size D50 | ≤ 10 μm | 8.2 μm |
| Particle size D97 | ≤ 35 μm | 28.5 μm |
| Throughput | 2–3 t/h | 2.8 t/h |
| Product whiteness | No reduction | Maintained |