Iron, the most widely used and consumed metal, makes up about 95% of global metal demand and is essential to modern industry and infrastructure. But how is iron obtained and separated from iron ore?
The answer lies in iron ore processing—a series of steps including crushing, grinding, magnetic separation, flotation, and gravity separation. This article introduces four major ore types and their corresponding processing methods, with Xinhai's project cases highlighting key techniques and practical solutions that enhance efficiency and economic returns.
Iron predominantly exists in compound forms in nature, most commonly as iron oxide. The following are several of the most important types of iron ore:
| Types of Iron Ore | Appearance and Specific Gravity | Key Characteristics | Maximum Grade (Theoretical) |
|---|---|---|---|
| Magnetite | Black-gray, specific gravity approx. 5.15 | Strongly magnetic, allowing direct magnetic separation for processing; dense structure with poor reducibility, weathers into hematite over time. | 72.4% |
| Hematite | Dark red, specific gravity approx. 5.26 | High iron content (up to 70% Fe naturally), making it the most important iron ore globally; classified by structure into types like massive, specular, micaceous, and earthy hematite. | 70% |
| Limonite | Yellowish-brown or brown, specific gravity approx. 3.6-4.0 | Often occurs as an accessory mineral in other ores; loose structure, contains crystal water, and is chemically unstable. | 62.9% |
| Siderite | Bluish-gray, specific gravity approx. 3.8 | Rich in calcium/magnesium salts; its carbonate decomposes exothermically (releasing CO₂) at 800-900°C, requiring roasting before further processing. | 48.3% |
The beneficiation process for iron ore depends on the type of ore, dissemination grain size, mineral structure, and associated gangue minerals. Common methods for key ore types are outlined below.
1. Magnetite Processing
Characteristics: Strongly magnetic, responds well to simple low-intensity magnetic separation (LIMS).
Typical Flow: Staged grinding and staged LIMS.
Process: Crush/grind to liberate minerals, then use LIMS (often one roughing, two cleaning, and three scavenging stages). Concentrate grade can reach 65-70% Fe with a recovery rate of more than 70%.
Applicability: Ideal for coarse-grained, simple ores.
2. Hematite Processing
Characteristics: Weakly magnetic; often requires combined processes.
Common Flows:
High-intensity magnetic separation (HIMS) followed by reverse cationic flotation (to remove silica).
Roasting magnetic separation (oxidizing roasting at 600-700°C to generate magnetite, then LIMS).
Gravity separation (using jigs or tables) is employed if there's a significant specific gravity difference between the ore and the gangue.
Outcome: Concentrate grade typically 60-66% Fe, recovery 50-65%.
3. Limonite Processing
Characteristics: Contains crystal water, unstable, and difficult to treat.
Common Methods:
Gravity separation (using jigs and spirals) is primarily due to its high density.
Roasting magnetic separation (to remove water and create magnetism).
Flotation can be added if the silica content is high.
Outcome: Concentrate grade usually 55-62% Fe, but recovery can be variable.
4. Siderite Processing
Characteristics: Contains carbonate, decomposes (releasing CO₂) upon heating; requires roasting before magnetic separation.
Primary Method: Roasting (800-900°C) to convert to magnetite/hematite, followed by magnetic separation. Combined flows, such as "roasting-HIMS-flotation," are also used.
Outcome: The roasted concentrate grade can reach 55-60% Fe, with a recovery rate of 40-55%.
5. Combined Processes
For complex or mixed ores (e.g., magnetite-hematite), combined flows, such as "magnetic separation-flotation" or "gravity-magnetic-flotation," are essential to achieve both the high grade and recovery required for smelting.
Xinhai has multiple EPC project cases in iron ore processing plant contracting and operation. Here are three of them:
1. Xinjiang 3300t/d Iron Ore Plant (Upgrade Project): Optimized existing equipment and introduced a fully closed-circuit flowsheet (three-stage grinding, six-stage separation, concentrate/tailing dewatering). Achieved 90% equipment utilization and increased iron recovery from 68% to 80%, passing full acceptance.
2. Inner Mongolia 2500t/d Iron Ore Plant (EPC+M+O): Conducted ore testing to confirm iron as the primary valuable mineral. Implemented a "single-stage grinding, two-stage classification, four-stage magnetic separation" process, consistently producing concentrate grading over 65% Fe, exceeding contractual targets by 15%.
3. Shanxi 1200t/d Iron Ore Plant (EPC+M+O): Applied a "two-stage crushing, two-stage grinding, one roughing-three cleaning magnetic separation" circuit with energy-saving ball mills (20% less power consumption) and a wastewater recycling system for zero liquid discharge. Reduced construction costs by 8% versus the industry average.
Conclusion
Each type of iron ore presents unique properties and processing challenges. Optimizing recovery and grade requires scientifically sound, economically viable processes customized to your ore’s characteristics—boosting returns while minimizing environmental impact.
With over 30 years of expertise, Xinhai China delivers end-to-end services—from testing and design to equipment, EPC, and operation—for both standard and complex ores, providing efficient and sustainable solutions.
Looking for a full-scope iron ore processing partner? Contact Xinhai for reliable, integrated project support.
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