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Email：sales@rotarykilnchina.com
Henan Hongke Heavy Machinery Co., Ltd. ("Henan Hongke Machinery") has designed, manufactured, and delivered a complete magnesium metal rotary kiln production line in Henan Province, China. The system calcines dolomite ore at high temperatures, producing active calcined dolomite (CaO·MgO) for magnesium metal extraction through the silicothermic (Pidgeon) process.
The quality of calcined dolomite directly determines magnesium yield, energy efficiency, and overall economics of the downstream reduction process.
Why a Rotary Kiln for Dolomite Calcination?
Dolomite (CaCO₃·MgCO₃) must be calcined at 1,100–1,250 °C to decompose both carbonates:
CaCO₃·MgCO₃ → CaO·MgO + 2CO₂
The calcined product must meet strict specifications for magnesium reduction:
| Parameter | Requirement |
|---|---|
| Activity | ≥ 340 mL (4N-HCl method) |
| Loss on ignition (LOI) | ≤ 2.0% (ideally < 1.0%) |
| MgO content | ≥ 35–38% |
| CaO content | ≥ 55–58% |
| Calcination degree | > 95% |
The rotary kiln is preferred over shaft kilns for medium-to-large producers because it offers continuous operation, uniform calcination, precise temperature control, and fuel flexibility.
Equipment Specification
| Parameter | Specification |
|---|---|
| Kiln type | Direct-fired rotary kiln |
| Shell size | φ2.5 × 50 m |
| Shell material | Q345B carbon steel, 16–25 mm |
| Rotational speed | 0.5–3.5 rpm (VFD) |
| Inclination | 3–4% |
| Dolomite feed size | 20–60 mm |
| Calcination temperature | 1,150–1,250 °C |
| Capacity | 150–250 t/day calcined dolomite |
| Fuel | Pulverized coal / natural gas |
| Specific heat consumption | 1,100–1,300 kcal/kg |
| Drive motor | 55 kW |
Complete System Scope
| Subsystem | Function |
|---|---|
| Crushing | Hammer crusher reduces raw dolomite to 20–60 mm |
| Raw material storage | Covered stockpile with live-bottom reclaim |
| Kiln feed system | Gravimetric weigh feeder and belt conveyor |
| Rotary kiln | Main calcination reactor with optimized L/D = 20 |
| Kiln head system | Hood, multi-channel burner, primary air fan |
| Clinker cooler | Rapid cooling of calcined dolomite below 100 °C |
| Exhaust gas treatment | Cyclone + bag filter (stack emissions ≤ 30 mg/Nm³) |
| Product handling | Conveying, crushing to 10–40 mm, and storage |
| Electrical & control | DCS/PLC, VFDs, field instruments |
Design Highlights
Optimized L/D ratio (20:1) — ensures adequate residence time (30–60 min) for complete calcination, with a long burning zone for full CaCO₃ and MgCO₃ decomposition and a proper preheat zone to prevent thermal shock cracking.
Application-specific refractory — magnesia-chrome or magnesia-spinel brick in the burning zone (1,150–1,250 °C), high-alumina brick in the preheat zone. Selected for the corrosive high-CaO environment of calcined dolomite.
Multi-channel burner — long, adjustable flame with ±20 °C temperature control in the burning zone, low NOx staged combustion, and coal/gas dual-fuel capability.
Internal heat exchange lifters — in the preheat zone, increase effective heat transfer surface area and improve overall thermal efficiency.
How It Works
1.Preheating (100–800 °C): Raw dolomite gradually heated by counter-current exhaust gas
2.Calcination (800–1,150 °C): MgCO₃ decomposes (above 750 °C) and CaCO₃ decomposes (above 900 °C), releasing CO₂
3.High-temp soaking (1,150–1,250 °C): Complete decomposition ensured in the burning zone
4.Cooling: Rapid cooling below 100 °C to prevent re-carbonation
5.Crushing: Calcined dolomite crushed to 10–40 mm for retort loading
Performance Results
| Parameter | Result |
|---|---|
| Calcination degree | > 95% |
| LOI | ≤ 1.5% (typically 0.8–1.2%) |
| Activity | ≥ 350 mL |
| MgO content | 36–38% |
| CaO content | 56–58% |
| Specific heat consumption | 1,100–1,300 kcal/kg |
| Refractory life (burning zone) | 8–12 months |
Consistent calcined dolomite quality directly translates to higher magnesium yield and lower energy consumption in the retort furnaces.
Henan Hongke Machinery's Magnesium Kiln Range
| Kiln Size | Daily Capacity | Scale |
|---|---|---|
| φ1.6 × 32 m | 50–100 t/day | Small |
| φ2.0 × 40 m | 100–180 t/day | Medium |
| φ2.5 × 50 m | 150–250 t/day | Medium-large (this project) |
| φ3.0 × 60 m | 250–400 t/day | Large |
| φ3.5 × 70 m | 400–600 t/day | Major facility |
Every system is engineered for the client's specific dolomite chemistry, capacity, and fuel type — supplied as a complete turnkey line from crushing through product handling.
Client Feedback
"The rotary kiln from Henan Hongke Machinery has significantly improved the quality and consistency of our calcined dolomite. LOI is consistently below 1.5%, activity above 350 mL — exactly what our retort furnaces need. The kiln runs reliably with minimal maintenance."
About Henan Hongke Machinery
Henan Hongke Heavy Machinery Co., Ltd., based in Henan Province, China, manufactures rotary kiln systems for magnesium, zinc oxide, cement, lime, and metallurgical applications. Complete in-house manufacturing with global shipping, installation supervision, and after-sales support.
