Production Process of Hydrofluoric Acid (HF)
31 Jul.,2025
What is Hydrogen Fluoride?
Hydrogen Fluoride also referred to as hydrofluoric acid or Anhydrous hydrofluoric acid is a clear, colorless corrosive liquid that is extremely hazardous. HF is a versatile chemical with diverse industrial applications, but its handling requires meticulous attention to safety due to its corrosive nature and potential health hazards. When HF acid is dissolved in water, it may be called hydrofluoric acid. HF is a weak acid. It’s called a weak acid because it doesn’t fully detach or separate into its ions in water, but it’s still a very dangerous acid due to the potential of acute fluoride toxicity.
Production Process of Hydrofluoric Acid (HF)
1. Raw Material Preparation
- Fluorspar (CaF₂): Crushed and dried to moisture content <0.1% for optimal reactivity36.
- Sulfuric acid (H₂SO₄): Concentrated or fuming sulfuric acid (20-25% SO₃) is used68.
2. Main Reaction (Fluorspar-Sulfuric Acid Process)
Chemical Copy Code
CaF₂ + H₂SO₄ → 2HF↑ + CaSO₄
- Conditions:
- Temperature: 150–250°C (material layer), with furnace jacket at 450°C36.
- Byproducts: SiF₄ and SO₂ generated from impurities (e.g., silica)613.
- Conversion rate: >97%3.
3. Gas Purification & Condensation
- Washing & Cooling:
Reaction gases (HF/SiF₄/SO₂) pass through scrubbers to remove dust and cool to 60°C69. - Condensation:
- Primary condenser at 19.5°C: Liquefies HF gas9.
- Secondary condenser at 10°C: Further separates residual gases6.
4. Refining
- Distillation:
- Crude HF undergoes fractional distillation to remove H₂SO₄ and H₂O impurities39.
- Degassing tower eliminates light components (SO₂/SiF₄)6.
- Output: Anhydrous HF (AHF) with purity >99%613.
5. Electronic-Grade HF Production
- Absorption: AHF absorbed in ultra-pure water (resistivity >18 MΩ·cm)19.
- Filtration:
- Removes particles via 0.2 μm ultrafiltration membranes1.
- Chelating resins eliminate metal ions (e.g., Fe, Cu)111.
- Sub-boiling distillation: Final purification for semiconductor-grade HF
