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.