In the actual production process, the main chemical component like iron and other impurities that affects the whiteness of calcium carbonate. Therefore, most companies pay attention to the strict selection of lime. In addition, in the process, limestone is calcined and digested. The refining process also has an effect on the whiteness of calcium carbonate.
1 Limestone quality
In limestone, the main chemical component that affects the whiteness is the content of impurities such as iron, manganese, and hydrochloric acid insolubles. Among them, iron is mainly in the form of ferric ions in calcium carbonate, which is the main cause of the decrease in whiteness of calcium carbonate. Therefore, the whitening of calcium carbonate is the removal of iron by physical and chemical methods.
In the beneficiation stage, the quality of limestone is not up to standard, the impurity content is too high, and harmful impurities such as silica, alumina and iron oxide react with calcium oxide to form a low-melting viscous substance during calcination, causing “nodulation” in the shaft kiln, which will attach to the surface of calcium oxide, reduce product whiteness.
Different digestive devices have different effects on whiteness, and the effects from low to high are: digestive tank, paddle digestion, and drum digesting machine.
The refining process is one of the important factors affecting the whiteness of the slurry. The quality of the refining process can make the whiteness greatly different. The purpose of the refining process is to remove all kinds of impurities in the finished product. The more thorough the impurities is, the higher the whiteness is.
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16th Oct 2018