Lecture hall of knowledge phase I heavy calcium carbonate

Ground calcium carbonate molecular formula CaCO3 relative molecular weight 100.09

1. Properties of heavy calcium carbonate

White powder, colorless and tasteless. Stable in air. Almost insoluble in water, insoluble in alcohol. In case of dilute acetic acid, hydrochloric acid and nitric acid, it will boil and dissolve. When heated to 898 ℃, it began to decompose into calcium oxide and carbon dioxide.

Heavy calcium carbonate, referred to as heavy calcium, is made by grinding natural carbonate minerals such as calcite, marble and limestone. It is a commonly used powdery inorganic filler with the advantages of high chemical purity, great inertia, not easy chemical reaction, good thermal stability, no decomposition below 400 ℃, high whiteness, low oil absorption, low refractive index, soft quality, dry, no crystal water, low hardness, small abrasion value, non-toxic, tasteless, odorless, good dispersion, etc.

According to the needs, we can provide ordinary calcium carbonate powder, ultra-fine calcium carbonate, wet grinding ultra-fine calcium carbonate and ultra-fine surface modified heavy calcium carbonate with different particle size requirements.

Calcium carbonate is an important and widely used inorganic salt. Heavy calcium carbonate, also known as ground calcium carbonate (GCC for short, kotamite in the United States), is made by directly crushing natural calcite, limestone, chalk, shells, etc. by mechanical method. Because its settling volume (1.1-1.9ml / g / g) is smaller than that of light calcium carbonate (2.4-2.8ml / g) produced by chemical method, it is called heavy calcium carbonate.

The chemical formula of calcium carbonate is CaCO3, and its crystal mainly consists of calcite with trihedral metatrihedral crystal and aragonite with orthorhombic crystal. Under normal temperature and pressure, calcite is stable and aragonite is quasi stable. At present, calcite is mainly used.

Under normal pressure, calcite is heated to 898 ℃ and aragonite is heated to 825 ℃, which will decompose into calcium oxide and carbon dioxide; calcium carbonate reacts with strong acid to produce water and corresponding calcium salts (such as calcium chloride CaCl2) and release carbon dioxide at the same time; at room temperature (25 ℃), the concentration product of calcium carbonate in water is 8.7 × 1029, the solubility is 0.0014, and the pH value of calcium carbonate aqueous solution is 9.5 ~ 10.2, The pH value of air saturated calcium carbonate aqueous solution is 8.0 ~ 8.6. Calcium carbonate is non-toxic, odorless, non irritating, usually white, with a relative density of 2.7 ~ 2.9. The Mohs hardness of calcite is 3, aragonite is 3.5 ~ 4. Calcite has three groups of rhombohedral cleavage, aragonite also has cleavage. The sedimentation volume of heavy calcium carbonate is 1.2 ~ 1.9ml/g, and the specific surface area is about 1m2 / g; the oil absorption value of heavy calcium carbonate is about 48ml / 100g due to its large particle size, smooth surface and small specific surface area.

2 production process

There are two production processes of heavy calcium carbonate. Dry production process: firstly, the calcite, limestone, chalk (E), shell, etc. transported from the quarry are selected by hand to remove gangue; secondly, the limestone is roughly crushed by crusher, and then the fine limestone powder is obtained by Raymond (pendulum) grinding, and then the powder is graded by classifier, and the powder that meets the particle size requirements is packaged and put into storage as product, otherwise it is returned to the mill for grinding again. Wet production process: first, the dry fine powder is made into suspension, which is further crushed in the mill, and then the ultra-fine heavy calcium carbonate is prepared after dehydration and drying.

3. Characteristics of heavy calcium carbonate

The shape of heavy calcium carbonate is irregular, its particle size is different, and the particles have certain edges and corners, rough surface, wide particle size distribution, large particle size, the average particle size is generally 1 ~ 10 μ M. According to the original average particle size (d), heavy calcium carbonate can be divided into coarse ground calcium carbonate (> 3 μ m), fine ground calcium carbonate (1 ~ 3 μ m) and ultra-fine calcium carbonate (0.5 ~ 1 μ m)

The powder characteristics of heavy calcium carbonate are as follows: A. irregular particle shape; B. wide particle size distribution; C. large particle size.

4. Function of heavy calcium carbonate

Heavy calcium carbonate, referred to as heavy calcium, is a white powder made of high-quality calcite as raw material. Its main component is CaCO3. It is characterized by high whiteness, good purity, soft hue and stable chemical composition. Therefore, heavy calcium is a very good filler commonly used in industry. Heavy calcium is usually used as filler. It is also widely used in artificial floor tiles, rubber, plastics, papermaking, coatings, paints, inks, cables, building supplies, food, medicine, textile, feed, toothpaste and other daily chemical industries. As a filler, it can increase the volume of products and reduce production costs. Used in rubber, it can increase the volume of rubber, improve the processability of rubber, play a semi reinforcing or reinforcing role, and adjust the hardness of rubber.