Calcium carbonate makes up almost one-twentieth of the earth’s crust. But the abundant mineral is found in many living things, including the human body. However, calcium carbonate processing extracts the multi-purpose material from inorganic sediments, namely limestone, chalk, and marble.
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Use a rotary kiln calcium carbonate processing of limestone stock smaller than 40 millimeters
Limestone is subjected to high temperatures to strip carbon dioxide and produce calcium oxide. This calcination process is performed in a kiln, but the type of technology depends on the feed size of your raw material.
A shaft kiln typically handles limestone between 20 mm and 175 mm in size. Stones go through preheating, heating, and cooling as they travel down the shaft to discharge quicklime. A rotary kiln employs the same principle but is set at a horizontal position and tipped at an angle of around 4°. This structure accommodates finer stones in the 15 mm to 40 mm range.
Mix calcium slurry constantly to avoid crystallization of particles
Calcium oxide is hydrated to produce calcium hydroxide. Also known as slaked lime, this compound treats industrial wastewater and neutralizes gases.
Slaking temperature is critical to the structure of particles. If you heat the slurry to around the boiling point of water forms finer particles sizes with a smaller specific surface. But unless mixed well, the particles will crystallize and agglomerate in the slurry.
Precipitated calcium carbonate can achieve 99.9% purity
Precipitated calcium carbonate (PPC) is synthetically produced from the chemical reaction between carbon dioxide and “milk-of-lime” slurry. The material is a refined form of limestone using calcium carbonate processing techniques.
The white material serves as a filler in different applications such as paints, papers, and pharmaceutical products. The grain size can be controlled from submicron to more than 10 microns, and the purity can be increased to 99.9%.
Spongy form of calcium carbonate could open up new applications
Researchers stumbled upon a spongy form of calcium carbonate occurring naturally in mussels. Ground shells of the mollusc reacted to acetic acid to form a highly absorbent type of calcium carbonate.
The porous material can soak up contaminants like oils or dyes and is an object of interest for a range of biomedical applications.