UNIQUE NEWS

Rock salt (NaCl) is a versatile mineral used across various industries, from road de-icing to chemical production. Its unique properties make it different from other stones like limestone or granite, especially in how it’s processed. The crushing stage is particularly critical, as it determines the salt’s final particle size, which directly affects its application.

Key Properties of Rock Salt

Understanding the key properties of rock salt is essential for efficient processing:

• Main Component: Sodium chloride (NaCl)
• Mohs Hardness: 2–2.5 (softer than most other stones)
• Structure: Brittle, easy to break
• Hygroscopicity: Absorbs moisture easily, potentially leading to clumping
• Corrosive: Can cause damage to metal equipment

Given these characteristics, it’s important to carefully control the crushing process to minimize wastage and excessive powder formation.

Crushing Stages of Rock Salt

The crushing process involves multiple stages and is typically dry:

1. Raw Material
   Mined rock salt is usually found in blocks ranging from 200–800 mm, sometimes larger, and needs primary crushing to reduce the size for further processing.
2. Primary Crushing
   The goal is to reduce large blocks into manageable sizes. Common equipment used includes:
   • Jaw crushers
   • Double-tooth roller crushers
     Output size: ≤100–150 mm.
     Note: Heavy-duty cone crushers are generally unnecessary due to the soft nature of rock salt.
3. Secondary / Fine Crushing (Optional)
   For applications requiring smaller particle sizes, fine crushing is introduced.
   Common equipment:
   • Double-roller crushers
   • Low-speed hammer crushers
     Output size: 0–50 mm or 0–30 mm.
     It’s important to avoid high-speed impact crushers to minimize excessive fines.
4. Screening and Grading
   After crushing, rock salt is passed through vibrating screens to separate particles into different sizes:
   • 0–5 mm
   • 2–6 mm
   • 3–8 mm
   • 10–30 mm
     Oversized pieces are returned to the crusher for a closed-loop system, which helps improve yield and consistency.

Particle Sizes and Their Uses

Different particle sizes of crushed rock salt are suited for different industrial applications:

• Road De-icing Salt:
  Particle size: 2–6 mm or 3–8 mm
  Reason: Coarse enough to resist wind, fine enough to dissolve quickly for melting ice.
• Industrial Salt:
  Particle size: 0–10 mm (sometimes 0–5 mm)
  Uses: Water softening, leather processing, dye manufacturing, metallurgy.
• Chemical Raw Material:
  Particle size: ≤5 mm
  Uses: Chlor-alkali production, soda ash manufacturing, and other high-purity chemical processes.
• Large Particle Salt:
  Particle size: 10–30 mm
  Uses: Special industrial applications or export-grade de-icing salt.

Why Controlled Crushing Is Crucial

The goal of rock salt crushing isn’t just to create the finest particles possible. Excessive fines can:

• Lower market value
• Increase moisture absorption and clumping
• Complicate storage and transport
• Generate dust, raising environmental and safety concerns

Thus, achieving accurate particle size control is crucial, rather than over-crushing.

Simplified Processing Flow

The typical process for rock salt is as follows:

• Mining → Primary Crushing → Secondary/Fine Crushing (Optional) → Screening & Grading → Finished Product by Size

Conclusion

Crushing is a critical stage in rock salt processing, with particle size control playing a significant role in determining its end use. Whether for road de-icing, chemical manufacturing, or industrial applications, proper crushing methods ensure efficient transport, storage, and application of the product. Achieving the right balance of particle sizes guarantees the best performance for specific uses while minimizing environmental impact.