Process characteristics and process of quartz stone pickling

1. Efficient impurity removal
● Acid combination: Commonly used mixed acids (such as hydrochloric acid-hydrofluoric acid, oxalic acid-hydrofluoric acid) are used to remove metal impurities such as iron and aluminum. For example: hydrofluoric acid (HF) dissolves silicate inclusions; Oxalic acid specializes in iron oxides (such as hematite), and the iron dissolution rate can reach 40% at 90-100°C.
● Auxiliary technology: Adsorption materials: such as the patented separator tube filled with adsorbents (such as modified PP particles), real-time adsorption of dissolved metal ions, extending the life of the acid; impurity removal particles: PP particles with surface modified sodium alginate/chitosan to enhance impurity capture capacity.

2. Circulation and energy-saving design

● Acid regeneration: The acid discharged after pickling is recycled after concentration detection and supplementation with new acid, reducing costs by more than 30%;
● Heating optimization: Use PPH material reaction tank (resistant to 110°C) with electric heating (cost only RMB 3-5/ton of sand), replacing steam/biomass heating (> RMB 10/ton).

3. High corrosion resistance requirements for equipment

●Hydrofluoric acid is highly corrosive, and the equipment needs to use *graphite lining or be coated with ZS-1033 hydrofluoric acid resistant anti-corrosion coating (poly-modified phenolic fluorine resin + flake graphite), which increases the service life by 3 times.

The following is a general process for industrial pickling, combining pretreatment, pickling, and post-treatment:

Stage 1: Pretreatment (physical impurity removal)
1. Crushing and screening: jaw crusher coarse crushing → cone crusher fine crushing → vibrating screen water washing (high-pressure water jet) → 15-100 mesh screening.
2. Magnetic separation and scrubbing: Ultrasonic scrubbing: 9-10 hours at 6-12 W/m² intensity, dispersant (1.45-2.05 kg/ton sand) to assist in stripping surface impurities; high gradient magnetic separation: vertical ring pulsating magnetic separator (0.8-1.6 T increasing magnetic field), remove 99% of mechanical iron.
3. High temperature roasting (optional): roasting at 900-950℃ for 3 hours to remove organic matter/water and make quartz more acid-reactive.

Stage 2: Core process of pickling

1. Acid preparation and feeding

● Acid formula example:

●Solid-liquid mixing: quartz sand and impurity removal particles (volume ratio 0.4-0.48) are loaded into the pickling tank, and the volume of acid accounts for 70-75%.
2. Dynamic reaction control
●Temperature: 60-75℃ (general sand) → 90-100℃ (high purity sand);
●Time: 3-12 hours (depending on the quality of the original ore);
●Mixing method: Rotating pickling tank (3-4 h, 70-75℃); Air compressor bubbling or mechanical stirring to ensure uniform acid exposure.
3. Acid separation and regeneration
●After standing for 40-50 minutes, the acid is discharged, and the floating impurity removal particles are filtered and recovered;
●The acid is recycled after concentration adjustment (the oxalic acid system can be recycled 5-8 times).

Stage 3: Post-treatment (deacidification and drying)
1. Water washing and deacidification: rinse with deionized water until pH is neutral, and neutralize residual acid with alkaline solution (such as NaOH);
2. Dehydration and drying: vacuum filtration (water content ≈ 10%) → natural drying/hot air drying (water content < 5%);
3. Screening and packaging: particle size classification (such as 5-20 mesh), quality inspection of purity/whiteness before packaging.

1. Formula adaptability: The acid ratio needs to be adjusted according to the iron content/morphology of the original ore; High hematite: Oxalic acid is preferred (Fe²⁺ is enhanced at pH=3); Complex inclusions: HF concentration needs to be increased to 40–55%.

2. Wastewater treatment challenges: Fluorine/heavy metal wastewater requires lime milk precipitation → neutralization tank agent treatment (such as NH₄PF₆);
Acid mist is purified and discharged through an alkaline water spray tower.

3. Equipment innovation: PPH integrated reactor: welded pipe + injection flange to prevent leakage; Fluidized bed pickling: Oxalic acid and sand react dynamically in the fluidized bed, increasing efficiency by 30%.

●Operation protection: HF corrosion resistant equipment (mask/rubber gloves) + closed workshop ventilation;

●Circular economy: acid regeneration rate>80%; flushing water concentration tank reuse.