Production Process and Technology of Pyrite Powder

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• Stable-chemical-property Pyrite Powder
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Abstract

Pyrite (FeS₂), also commonly known as iron disulfide or fool’s gold, is widely used in sulfuric acid production, metallurgy, construction fillers, battery materials and other industrial fields. Pyrite powder production mainly adopts dry mechanical crushing, wet grinding and calcination purification processes. This paper systematically introduces the production technology, processing equipment and quality control methods of pyrite powder, providing a reference for industrial production and product optimization.

1. Main Production Processes of Pyrite Powder

1.1 Dry Grinding and Air Classification (Mainstream Process)

Dry processing is the most widely applied technology for bulk pyrite powder production, featuring high efficiency, low water consumption and no wastewater discharge.

The process flow is as follows:

1. Primary crushing: Raw pyrite ore is crushed to 20–30 mm by jaw crusher.
2. Secondary and fine crushing: Cone crushers or hammer crushers further reduce the particle size to below 5 mm.
3. Superfine grinding: Materials are ground into fine powder by vertical roller mills, ring roller mills or ball mills.
4. Air classification: Turbine air classifiers accurately control particle size distribution.
5. Purification: Magnetic separation and screening remove magnetic impurities and coarse particles.
6. Drying and packaging: Hot-air drying ensures low moisture content, followed by sealed packaging.

This process is suitable for medium-to-high grade pyrite ore and meets the requirements of general industrial applications such as sulfuric acid manufacturing.

1.2 Wet Superfine Grinding and Dehydration

Wet grinding is adopted for high-value applications requiring fine particle size and narrow distribution.

The process flow is as follows:

Crushing → wet ball milling (with water and dispersants) → hydraulic classification → filter pressing or centrifugal dewatering → low-temperature vacuum or hot-air drying → dispersion → packaging.

Although this method produces finer and more uniform powder, it has higher energy consumption and generates wastewater, so it is mainly used for high-grade fillers and functional materials.

1.3 Roasting and Magnetic Separation Purification

For low-grade raw ore or products requiring high purity, roasting combined with magnetic separation is used to remove impurities.

The process includes:

Pyrite concentrate → oxidizing roasting at 600–700 °C → magnetic separation to remove iron-bearing impurities → cooling → re-grinding → classification → finished product.

This process effectively reduces harmful impurities and improves sulfur and iron grades.

2. Key Processing Technologies and Equipment

2.1 Crushing and Milling Equipment

• Primary crushing: Jaw crusher
• Fine crushing: Cone crusher, hammer crusher
• Dry milling: Vertical roller mill, ring roller mill, ball mill
• Wet milling: Wet ball mill, stirred mill
• Classification: Hydrocyclone, screw classifier, turbo air classifier

2.2 Purification Technologies

• Flotation: The core beneficiation method using xanthate collectors under pH 6–9 to separate gangue and heavy metal impurities.
• Magnetic separation: Removes magnetite and other magnetic minerals.
• Gravity separation: Separates impurities based on density differences.

2.3 Drying and Surface Modification

• Drying systems control moisture below 0.5% to prevent oxidation and agglomeration.
• Surface modification with coupling agents or stearic acid improves dispersibility and compatibility in composite materials.

3. Quality Control Methods

3.1 Raw Material Control

Incoming ore is strictly tested for FeS₂ grade, total sulfur, total iron and harmful impurities (As, Pb, Zn, SiO₂). High-quality raw ore typically has FeS₂ content above 45%.

3.2 In-process Control

• Monitor particle size during crushing and grinding to ensure stable feeding.
• Adjust pH, reagent dosage and slurry concentration in flotation to guarantee purification effect.
• Control drying temperature and time to avoid overheating and oxidation.

3.3 Finished Product Quality Indicators

Key quality parameters and testing methods are listed below:

• Total sulfur (S): ≥48% tested by combustion titration or coulometric titration
• Total iron (Fe): ≥42% tested by chemical titration or atomic absorption spectrometry
• Particle size: D50 = 8–25 μm measured by laser particle size analyzer
• Moisture: ≤0.5% tested by oven-drying method
• Harmful impurities: As ≤0.05%, Pb ≤0.1%, SiO₂ ≤3% tested by AAS or ICP

3.4 Packaging and Storage

Pyrite powder must be packed in moisture-proof, sealed bags and stored in dry and ventilated warehouses to avoid moisture absorption, oxidation and reaction with acidic or alkaline substances.

4. Conclusion

Dry grinding and air classification is the preferred process for large-scale pyrite powder production due to its economic and environmental advantages. Wet grinding and roasting purification provide solutions for high-purity and fine-particle applications. Full-process quality control, including raw material inspection, particle size management, impurity removal and finished product testing, is essential to ensure stable performance and meet downstream industrial requirements.