| 摘要 |
PROBLEM TO BE SOLVED: To produce a high purity gypsum powder which has high bulk density and can easily be mixed with a different gypsum powder. SOLUTION: The objective neutralized gypsum powder 18 is produced by reacting sulfuric acid with calcium carbonate in a reaction vessel 13 to form a slurry 14 containing a neutralized gypsum powder; recycling the slurry 14 to the reaction vessel 13 to obtain the neutralized gypsum powder as first seed crystals. In the case, a gypsum powder different from the above neutralized gypsum powder which is obtained by only reacting sulfuric acid with calcium carbonate, is added to the reaction vessel 13 as second seed crystals by 3-30 wt.% of the neutralized gypsum powdery product. As the second seed crystals, a flue gas desulfurization gypsum powder, ground material formed from a gypsum ore, gypsum powder formed by reacting a sulfate with calcium carbonate, or the like, is used.
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