METHOD FOR INDUSTRIAL MANUFACTURE OF PRECIPITATED CALCIUM CARBONATE (CaCO3) FROM CARBONATE BEARING ROCKS

摘要

Method for industrial manufacture of pure (precipitated) CaCO₃ comprising providing at least one naturally occurring carbonate bearing rock and comminuting said rock to increase its surface area. In a first reaction zone (R₁) the comminuted carbonate bearing rock is contacted with water and CO2 at a pressure higher than standard pressure, at a temperature in the range 30-500° C. and at a pH lower than 5 to thereby dissolve the carbonate. Dissolved material is conveyed from the first reaction zone (R₁) to a second reaction zone (R₂) held at a lower pressure than the first reaction zone and a pH higher than that of the first reaction zone, the presence of H⁺ ions in first and second reaction zones being caused by the reaction between CO₂ and water. In the second reaction zone the calcium carbonate is precipitated at a pH higher than 5.