DOUBLE DECOMPOSITION METHOD

摘要

PROBLEM TO BE SOLVED: To disturb the surface of a soln. to prevent the reprecipitation of overflowing magnesium hydroxide slurry and to uniformize the property of the discharged magnesium hydroxide slurry by supplying a part of the soln. discharged from the bottom part of a double decomposition tank to the outside part in the double decomposition tank. SOLUTION: In the double decomposition tank 1, the aq. soln. consisting essentially of the magnesium sulfate sent from an oxidation tank and a desulfulizing column of a desulfulizing system is reacted with a calcium hydroxide slurry to be converted to magnesium hydroxide and gypsum dihydride. On the other hand, in a slurry tank 2, a basic calcium compd. and water are mixed to prepare calcium hydroxide slurry. Then a part of the slurry discharged from the bottom part of the double decomposition tank 1 is supplied in circulation to the upper part of the double decomposition tank 1 and also the slurry in the slurry tank 2 is supplied to the double decomposition tank 1. An agitating means is disposed in an inner cylinder 3 of the double decomposition tank 1 so that the influence of the agitation is prevented to be applied to the outside part in the double decomposition tank 1 by the inner cylinder 3.