Process for preparing magnesium hydroxide

Claim 1

IN THE PROCESS FOR PREPARING MAGNESIUM HYDROXIDE COMPRISING MIXING AQUEOUS MAGNESIUM SALT SOLUTION WITH MAGNESIUM HYDROXIDE SEED AND REACTING SAID MIXTURE WITH DRY CALCINED DOLOMITE TO FORM A PRECIPITATE OF MAGNESIUM HYDROXIDE AND SEPARATELY REMOVING FROM THE REACTION ZONE AN IMPURITIES-ENRICHED UNDERFLOW AND AS OVERFLOW SAID PRECIPITATED MAGNESIUM HYDROXIDE, THE IMPROVEMENT WHICH COMPRISES ADMIXING WITH SAID SOLUTION AND MAGNESIUM HYDROXIDE SEED DRY CALCINED DOLOMITE OF WHICH AT LEAST ABOUT 90% OF ITS PARTICLES ARE LARGER THAN 0.2 MM. DIAMETER, VIGOROUSLY AGITATING SAID ADMIXTURE IN A PRIMARY REACTION ZONE, SEPARATELY REMOVING FROM SAID PRIMARY REACTION ZONE AN IMPURITIES-ENRICHED UNDERFLOW AND A PRIMARY OVERFLOW CONTAINING PRECIPITATED MAGNESIUM HYDROXIDE AND UNREACTED FEED COMPONENTS, INTRODUCING SAID PRIMARY OVERFLOW INTO A SECONDARY REACTION ZONE, GENTLY AGITATING WHILE AN IMPURITIES-ENRICHED SOLIDS FRACTION SETTLES TO THE BOTTOM OF SAID SECONDARY ZONE, REMOVING SECONDARY OVERFLOW CONTAINING PRECIPITATED MAGNESIUM HYDROXIDE AND SEPARATELY REMOVING A SECOND IMPURITIES-ENRICHED UNDERFLOW AND RECYCLING AT LEAST A PORTION OF SAID SECOND UNDERFLOW TO THE REACTION SYSTEM, SAID MAGNESIUM HYDROXIDE SEED BEING ADDED IN AN AMOUNT TO PROVIDE FROM 0.5 TO 40 TIMES THE AMOUNT OF MAGNESIUM HYDROXIDE BEING PRECIPITATED.