CS207300B1 - Method of making the calcium carbonate - Google Patents

Description

(54) Method of producing calcium carbonate

The invention solves the production of calcium carbonate from calcium oxide prepared by thermal decomposition of natural non-dolomitic limestone, or from its hydratade products.

Calcium carbonate CaCO ₃ is used for industrial purposes or in natural form (mainly as limestone mineral), or is produced synthetically in the form of caldera mineral by reacting carbon dioxide to calcium hydroxide (lime milk) or by reacting carbon dioxide and ammonia with aqueous chloride solution Calcium (BUCKIE, RH: Precipitation of Calcium Carbonates. Theory Properties and Applications. New York, West Virginia Pulp and Paper CO. 1948). It is usually contaminated with admixtures of silicon, iron, aluminum and magnesium compounds, depending on their content in the raw materials used. It is used in industry or directly, e.g. in the rubber, paper, food, pharmaceutical and chemical industries, both as an intermediate in the preparation of calcium oxide and calcium hydroxide, which have wear e.g. in the production of additives and greases in the oil processing industry. Industrial use requires a constant quality of calcium carbonate and products made from it, which the use of natural raw materials cannot guarantee

The above-mentioned disadvantages are overcome by the process for the production of the calcium carbonate according to the invention, which consists in the fact that in an aqueous solution containing ammonium formate by weight. 15 to 20% selectively leaches calcium or calcium hydroxide from quicklime or slaked lime, which is added in powder form and dosed according to the content of soluble calcium component, preferably in a ratio of 5 to 8 wt. parts of calcium raw material per 100 wt. Calcium carbonate is precipitated from the calcium component by filtering off the insoluble part of the feedstock with carbon dioxide and ammonia at pH 8-10. The bulk of the magnesium formate admixture remains in solution together with the regenerated ammonium formate and the admixture of optionally formed ammonium carbonate, the content of which depends on the precipitation conditions. The regenerated leachate solution is taken back into production for the selective leaching of calcium oxide from another portion of the starting calcium raw material.

The proposed production process represents a closed production cycle without harmful gaseous pollutants or waste water, while the regenerated leachate solution, containing mainly ammonium formate, is returned to production. It is advantageous to use low-grade quicklime with a high content of silicon, aluminum and iron compounds to obtain high-purity calcium carbonate (above 99% CaCO ₃ ), free of chlorides, sulphates or other undesirable anions which would be thermally decomposed they remain in the calcium oxide formed or in the product of its hydration.

Example 1

100 wt. parts of quicklime composition

95.6% calcium oxide, 3.7% calcium carbonate, 0.3% silica, 0.2% alumina, 0.1% ferric oxide, ground and sieved through a 0.06 mm sieve, with Mixing adds in portions up to 1650 wt. parts of a 20 ° C warm solution containing 250 wt. parts of ammonium formate and 1400 wt. parts of water. From the solution heated to about 50 to 60 ° C by the reaction heat, the undissolved residue is separated by filtration and from the filtrate cooled to 30 to 40 ° C with concurrently supplied carbon dioxide and ammonia, dosed in such a proportion that the reaction medium lows pH 8 to 9. , precipitates calcium carbonate in the form of mineral vaterite (yield = 99% CaCO ₃ ).

Example 2

100 wt. parts of slaked lime composition

Claims (1)

SUBJECT Process for the production of calcium carbonate, characterized in that, in an aqueous solution containing ammonium formate by weight. a concentration of 15 to 20% selectively leaches calcium or calcium hydroxide from quicklime or slaked lime, which is added in powder form and dosed according to the content of soluble calcium component, preferably in a ratio of 86.3% calcium hydroxide, 9.3% calcium carbonate, 2.1% silica, 0.4% magnesium oxide, 1.2% ferric oxide, ground and sieved through a 0.06 mm sieve, with stirring add in portions to 1300 wt. parts of a 40 ° C warm solution containing 200 wt. parts of ammonium formate, 0.1 wt. parts of ammonium carbonate and 1100 wt. parts of water. An insoluble residue is separated from the resulting calcium formate solution by filtration, and calcium carbonate as the mineral vaterite is precipitated at 20-30 ° C at pH 9-10 as described in Example 1. The yield is 118% by weight. parts of vaterite by weight above 99% CaCO ₃ . Example 3 100 wt. parts of slaked lime composition as in Example 2 are leached in 1500 wt. parts of a 20 ° C warm solution containing 300 wt. parts of ammonium formate and 1200 wt. parts of water. The insoluble residue is separated from the resulting calcium formate solution by filtration, and from the filtrate heated to 80-90 ° C carbon dioxide and ammonia, dosed in such a proportion that the reaction medium low pH 9-10, precipitates calcium carbonate in the form of aragonite mineral. The yield is above 99% of calcium carbonate. INVENTION 5 to 8 wt. parts of calcium raw material per 100 wt. parts of the leaching solution heated to 20 to 90 ° C and from the calcium component solution, after filtering off the undissolved part of the feedstock, precipitate calcium carbonate with carbon dioxide and ammonia at a pH of 8 to 10.