THE SEPARATION OF LIME FROM DOLOMITE1

Abstract

Calcination.—Magne ium carbonate in dolomite is decomposed by calcining for one hour at 800°C. Calcium carbonate is not completely decomposed until after calcination at 960°-1040°C for one hour. Treatment with sulphuric acid.—By adding sufficient H2SO4 to milk of dolomite to react with the lime present, a bulky precipitate of Mg(OH)2 is formed which may be partially separated from the finer CaSO4 by screening through a 120 mesh sieve. The residue on the screen contains about 68.3 per cent MgO and represents over 50 per cent of the original CaMgO. Flotation.—The best results by flotation were obtained by removing the fine material from the raw dolomite and then calcining at 920°C. Wood creosote flotation oil number 400 was found best suited for this separation. The concentrates removed by flotation, however, represent only 25 per cent of the dolomite originally treated. Leaching and screening.—By a leaching and screening treatment it is possible to obtain a product containing about 80 per cent MgO. This is superior to Canadian magnesite in MgO content. Elutriation.—By an elutriation treatment it is possible to obtain a residue containing over 85 per cent MgO and representing about 30 per cent of the, original dolomite.