What flows produce low-iron quartz sand (<30ppm Fe₂O₃) for photovoltaic glass?

2025-10-22

Producing low-iron quartz sand (<30 ppm Fe₂O₃) for applications like photovoltaic (PV) glass requires specialized processes to reduce impurities, particularly iron oxide (Fe₂O₃). The production flows typically involve the following steps:

Raw Material Selection

1. High-purity quartz: The process starts with selecting natural quartz deposits with very low iron and other impurities. Geological exploration identifies quartz with high purity, specifically targeting deposits with minimal iron content.

Processing Steps

2. Crushing and Screening:

   • Quartzite rocks or raw quartz are crushed into smaller particles, ensuring they remain free of contamination (e.g., ferrous metals from equipment).
   • Screening removes coarse material, ensuring a consistent grain size.

3. Attrition Scrubbing:

   • Scrubbing is used to remove surface impurities, clay, iron coatings, and other contaminants bonded to quartz particles.

4. Washing and Desliming:

   • Washing with water removes fine particles and other impurities. Desliming further filters out ultrafines and clay.

5. Magnetic Separation:

   • High-capacity magnetic separators are employed to remove iron-bearing minerals (magnetite, hematite, etc.) from the quartz sand. This step is critical for reducing the Fe₂O₃ content to very low levels.

6. Chemical Leaching:

   • Acid treatment, often with dilute sulfuric acid (H₂SO₄) or hydrochloric acid (HCl), dissolves iron contaminants trapped in the quartz structure.
   • This step ensures the removal of residual iron oxides and other metallic impurities.

7. Flotation:

   • Flotation techniques are used to separate any remaining non-quartz minerals, such as feldspar or mica, which may contain iron.

8. Ultrafiltration/Advanced Washing:

   • Advanced washing methods using clean water or ultrafiltration systems ensure the sand surface is free of impurities.

Quality Control and Analysis

9. Sorting and Testing:

   • Optical sorting or manual inspection is conducted to ensure particle purity.
   • Detailed chemical analysis (XRF, ICP-MS) verifies Fe₂O₃ content and ensures it meets the sub-30 ppm target.

10. Drying and Packaging:

    • Quartz sand is dried in oxygen-controlled drying ovens to prevent contamination.
    • Packaging is done in a contamination-free environment for transport.

This overall process is designed to achieve a high degree of purity, ensuring the quartz sand has Fe₂O₃ levels that make it suitable for high-transparency and high-performance PV glass. Each processing step must be precisely controlled to avoid contamination and maximize the removal of iron and other impurities.

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