Ground calcium carbonate production process

Ground calcium carbonate (GCC) is a powdered material produced by mechanically crushing minerals such as limestone, chalk, and marble. It is the most widely used and produced inorganic non-metallic mineral powder in various industries. The ground calcium carbonate production process primarily includes steps such as beneficiation, ore crushing, grinding, ultrafine grinding, and surface modification. This process ensures the production of high-quality GCC with specific particle sizes and surface properties for diverse applications.

Mineral Processing

Due to the abundant resources of limestone, high-quality calcite with a CaCO₃ content ≥ 97% is relatively plentiful. Currently, the production of ground calcium carbonate typically only involves simple washing and manual sorting of the ore.

Crushing

Crushing of ores generally involves two stages. In the first stage, manufacturers mainly use a jaw crusher, while in the second stage, they employ a hammer crusher or impact crusher. When the raw ore has a smaller block size and the feed size for the grinding mill is coarser, they can also use a single-stage hammer crusher or impact crusher.

Fine Grinding and Ultrafine Grinding

Currently, the Ground Calcium Carbonate (GCC) production process for producing GCC with a d97 ≥ 5μm primarily employs dry production methods. Equipment such as improved Raymond mills, roller mills (e.g., vertical mills, ring roller mills), and ball mills are commonly used in this process.

For ultrafine GCC with d97 ≥ 5μm, dry production is still the main method, although some applications utilize a combination of wet grinding and drying. This process typically involves the use of ball mills + classifiers, roller mills (including internal classification), and dry stirred mills + classifiers.

For GCC with a d97 ≤ 5μm, especially when a d90 ≤ 2μm is required for paper coating applications, wet production is generally preferred. The main equipment in this process includes stirred mills and sand mills, which are ideal for producing fine calcium carbonate with specific particle size distributions.

Surface Modification

Surface modification is one of the most important deep-processing technologies for ground calcium carbonate (GCC) and ultrafine GCC. In the past decade, the demand for surface-modified products has been growing at a rate of over 12% annually.

The surface modification of GCC mainly uses organic coating and composite modification methods. Organic coating modification involves coating GCC powder with organic substances, such as stearic acid and its salts, aluminum coupling agents, titanium coupling agents, and water-soluble polymers.

Currently, dry modification is the mainstream process for GCC. Unless manufacturers use wet ultrafine grinding, they rarely employ wet modification. In dry modification, they disperse the powder in a surface modification device in a dry state or after drying, adding surface modifiers at a certain temperature. Continuous surface modification machines have become the mainstream equipment for dry surface modification of GCC.

Composite Modification

Composite modification involves physically or chemically mixing or coating another inorganic powder onto the surface of GCC or ultrafine GCC. For example, manufacturers composite modify GCC with magnesium hydroxide or aluminum hydroxide. This results in a flame-retardant GCC powder. Manufacturers then use the modified powder as a filler in cables, providing both its original functions and enhanced flame retardancy.

Manufacturers often perform surface modification of GCC simultaneously with fine or ultrafine grinding. In this process, they directly add surface modifiers during the grinding, thus achieving both grinding and surface modification in the same equipment. For instance, manufacturers carry out surface modification of GCC used as a filler in unsaturated polyester-based composites (such as artificial stone) during the fine grinding stage in a vertical roller mill.

Application Areas

• Food Industry: Can be used as an additive.
• Construction and Paper Industries: Widely used for various applications.
• Under 200 mesh: Can be used as a feed additive with a calcium content of 55.6% or more and no harmful components.
• 250-300 mesh: Used as raw material for plastic factories, rubber factories, coating factories, and waterproof material factories. Suitable for interior and exterior wall painting with whiteness above 85%.
• 350-400 mesh: Used in the production of ceiling panels, downspouts, and chemicals. Whiteness above 93%.
• 400-600 mesh: Used in toothpaste paste and soap production, with whiteness above 94%.
• 800 mesh: Used in rubber, plastics, cables, and PVC, with whiteness above 94%.
• 1250 mesh: Used in PVC, PE, paints, coatings, paper base coatings, and surface coatings. Whiteness above 95%. It features high purity, high whiteness, non-toxicity, no odor, low oil absorption, and low hardness.
• Calcium Supplement: Manufacturers use calcium carbonate as a calcium supplement, which has an absorption rate of up to 39%, second only to calcium citrate. It dissolves in gastric acid and becomes one of the most widely used calcium supplements.

Development Trend

In industries such as rubber, paper, plastics, coatings, and composites, the demand for calcium carbonate products is increasing due to the varying matrices and required performance. This growing need highlights the importance of the Ground Calcium Carbonate (GCC) production process, which is essential for producing finely ground, high-quality calcium carbonate tailored to meet the specific performance and material properties required by these industries.

Complexity of Calcium Carbonate Particle Structure:
Various shapes of calcium carbonate particles, such as spindle-shaped, cubic, needle-like, spherical, and amorphous forms, are already available. Different shapes lead to different performances and applications. Researchers study the effects of various additives on the particle structure and morphology of calcium carbonate. This allows them to develop new types of calcium carbonate products, opening up new application possibilities.

Surface Treatment of Calcium Carbonate Particles:
The main drawback of using ordinary calcium carbonate as a filler in organic polymers is its hydrophilic and oleophobic surface, leading to poor dispersion in organic polymers. Since calcium carbonate cannot absorb into organic polymers, it has almost no reinforcing effect. Surface treatment of calcium carbonate powder has injected new vitality into its applications.

Deaggregation and Dispersion of Nano calcium Carbonate Particles:
In current nano calcium carbonate production, the secondary particle size is much larger than the primary particle size. Nanoparticles have a high surface energy and are highly active, making them prone to adsorption and agglomeration, which affects their stability and performance. Therefore, solving the dispersion problem of nano calcium carbonate particles is crucial.

Epic Powder

Epic Powder, 20+ years of work experience in the ultrafine powder industry. Actively promote the future development of ultra-fine powder, focusing on crushing,grinding,classifying and modification process of ultra-fine powder.  Contact us for a free consultation and customized solutions! Our expert team is dedicated to providing high-quality products and services to maximize the value of your powder processing. Epic Powder—Your Trusted Powder Processing Expert !