Aspects of the Use of Conversion Calcium Carbonate — the Solution of the Ecological Problem of Utilization

Abstract

Studies have been carried out to improve the quality of conversion calcium carbonate. The process of extraction of insoluble iron-containing impurities at the stage of obtaining calcium carbonate from calcium nitrate melt was studied. It has been determined that the preliminary removal of the acid-insoluble residue from the melt of Ca (NO₃)₂ by filtration or settling allows the Fe₂O₃ content to be reduced by more than 50 % in the form of magnetically susceptible impurities and further increases the whiteness of the final product. The effect of grinding and heat treatment of conversion calcium carbonate on the evolution of nitrogen-containing impurities is studied. It has been established that the amount of water-soluble substances in the sample increases exponentially with increasing shredding time of the material. Heat treatment can significantly reduce (in almost 3 times) the total content of water-soluble substances in the crushed product. Simultaneously with the removal of the "bound" nitrogen, the content of the main component increases by 1.5–2 %. A positive effect of heat treatment is also an increase in the rate of refinement of conversion calcium carbonate, which makes the dispersed composition of the product more homogeneous. A technological scheme for processing conversion calcium carbonate into a disperse filler with specified properties has been developed.