Prepn of a metal oxide mixts contg magnesium carbonate and calcium carbonate

摘要

Prepn. of a metal oxide mixt. contg. magnesium carbonate and calcium carbonate comprises: (a) thermal cleavage of a metal sulphate mixt. which contains magnesium sulphate, at 900-1200 deg C in a fluidised bed reactor; (b) cooling of the reaction gases (and solids carried out with the gases) in a cooling vessel at 250-350 deg C, such that a portion of the solids are sepd. during the cooling process; and (c) carrying out further dust sepn., esp. in a cyclonic separator and/or in hot electrostatic gas cleaners (EGRs), prior to subjecting the gas to a wet cleaning process; the novelty comprises (d) collecting (separately) the magnesium sulphate-poor, coarse solids which arise in the cooling vessel (Fraction A) and the magnesium sulphate-rich finely divided solids which arise in the cyclonic separator/hot EGRs (Fraction B); (e) removing the soluble metal sulphates from fraction A from the fraction by dissolving in water, giving a magnesium sulphate soln.; (f) and mixing this soln., fraction B and (i) a 0.5-7.5 fold amt. of quicklime (CaO) or (ii) a 0.65-10 fold amt. of hydrated lime (Ca(OH)2), based on the total amt. of magnesium sulphate contained in fractions A and B.