Process for the conversion of dolomite to magnesium hydroxide

Claim 1

A PROCESS OF MAKING MAGNESIUM HYDROXIDE WHICH IS EASILY FILTERABLE AND OF HIGH PURITY BY REACTION BETWEEN A BRINE CONTAINING MGCL2 AND SLAKED DOLOMITE IN GRAINS OBTAINED BY HYDRATING ANHYDROUS CALCINED DOLOMITE MAINTAINED IN THE STATE OF A FLUID BED BY A CURRENT OF HYDRATING GAS WHOSE PRESSURE OF WATER VAPOR AND TEMPERATURE ENABLE THE GRANULOMETRY OF THE OBTAINED HYDRATED DOLOMITE TO BE MAINTAINED SUBSTANTIALLY IDENTICAL TO THAT OF THE ORIGINAL ANHYDROUS CALCINED DOLOMITE, WHICH COMPRISES SOAKING SAID GRANULATED SLAKED DOLOMITE INE A PART OF THE BRINE, HAVING A MGCL2 CONCENTRATION OF 0.I TO 0.4 MOL PER LITER, THEN INTRODUCING THE MIXTURE INTO A SERIES OF REACTORS IN WHICH THE DOLOMITE STAYS FOR INCREASING TIMES, THE LAST REACTOR BEING FED WITH ANOTHER PART OF THE BRINE WHICH CIRCULATES IN THE REACTORS IN THE OPPOSITE DIRECTION TO THAT OF THE DOLOMITE, IN ORDER TO CONVERT SUBSTANTIALLY ALL THE CALCIUM CONTAINED IN THE DOLOMITE TO CALCIUM CHLORIDE AND ALL OF THE MAGNESIUM OF THE BRINE TO MAGNESIA HYDRATE, ELIMINATING THE EXHAUSTED BRINE FROM THE FIRST REACTOR WHEN THIS LATTER STILL CONTAINS ABOUT AT LEAST 0.01 BUT NOT MORE THAN ABOUT 0.05 MOL PER LITER OF MGCL2, THEN MIXING THE MAGNESIUM HYDROXIDE COMING OUT OF THE LAST REACTOR WITH COUNTER-FLOWING COLD WATER, AND MAINTAINING CONSTANTLY IN THE WASH WATER AT LEAST 0.005 MOL PER LITER OF MGCL2.