Heavy calcium carbonate is a kind of calcium carbonate powder material produced by mechanical crushing method using calcite, chalk, marble and other ores as raw materials. It is currently the most widely used and the largest amount of inorganic non-metallic mineral powder. Its production technology mainly involves Beneficiation, ore crushing, powder grinding and superfine grinding or superfine grinding, surface modification, etc.
1. Beneficiation
Due to the abundant calcite resources, high-quality calcite resources with a CaCO3 mass fraction ≥97% are relatively abundant. At present, only simple ore washing and manual sorting are generally carried out in the production of heavy calcium carbonate in China.
2. Broken
Generally, two stages are used for ore crushing. The first stage mainly adopts a jaw crusher, and the second stage adopts a hammer or impact crusher. When the raw ore lump size is small and the feed granularity of the mill is relatively coarse, one-stage hammer crusher or impact crusher can also be used.
3. Fine grinding and superfine grinding
At present, heavy calcium carbonate with d97≥5μm is mainly produced by dry method. The equipment includes improved Raymond mill (suspension roller mill or pendulum mill), roller mill (including pressure roller mill/vertical mill, ring roller mill) Etc.) and ball mills.
Superfine heavy calcium carbonate with d97≥5μm generally adopts dry production process, and some adopt wet grinding + drying process. Dry production mainly adopts cylindrical ball mill + classifier, roller mill (including ring roller mill with in-band classification, vertical mill/pressure roller mill), dry mixing mill + classifier, etc.
d97≤5μm, especially papermaking coating grade ultrafine heavy calcium carbonate slurry with d90≤2μm is generally produced by wet method, and the main equipment is agitating mill and sand mill.
4. Surface modification
Surface modification is one of the most important deep processing technologies for heavy calcium carbonate and ultrafine heavy calcium carbonate. In the past ten years, the demand for surface modified products has increased at a rate of more than 12% per year.
The surface modification of heavy calcium carbonate mainly adopts organic coating and compound modification methods. Organic coating modification is based on organic matter, such as stearic acid and its salts, aluminate coupling agent, titanate coupling agent, water-soluble polymer, etc. as surface coating/modifying agent, for heavy calcium carbonate The method of coating powder to modify it.
At present, dry modification is the mainstream process for heavy calcium carbonate. Unless a wet ultrafine grinding process is used, wet modification is rarely used. The dry modification process is a process in which the powder is dispersed in the surface modification equipment in a dry state or after drying, and a configured surface modifier is added at the same time to perform surface modification at a certain temperature. Continuous powder surface The modifier has become the mainstream equipment for dry surface modification of heavy calcium carbonate.
5. Compound modification
Composite modification is a surface modification method in which heavy calcium carbonate or ultrafine heavy calcium carbonate powder is uniformly mixed or coated with another inorganic powder on the surface of particles by physical or chemical methods, such as in heavy calcium carbonate Medium composite magnesium hydroxide or aluminum hydroxide, this modified heavy calcium carbonate powder is used for cable filler, in addition to the original function, it also has a flame retardant function.
The surface modification of some heavy calcium carbonate is carried out simultaneously with the fine grinding or ultra-fine grinding, that is, the surface modifier is added during the fine grinding and ultra-fine grinding, and the fine grinding of heavy calcium carbonate is completed in the same equipment. Superfine grinding and surface modification. For example, the surface modification of the heavy calcium carbonate filler used for unsaturated polyester-based composite materials (artificial stone) is completed in the fine grinding process of a vertical roller mill.
