GB714674A - A basic calcium and magnesium product - Google Patents

Abstract

In a process for the production of a reaction product, consisting mainly of basic calcium and magnesium compounds, from lime-containing and magnesia-containing minerals, preferably for use in water treatment, carbonate minerals such as, for example, dolomite, dolomitic limestone and calcareous magnesite, mixed if desired with calcium oxide, are heated, preferably in a double-drum rotary furnace under such conditions that carbon dioxide is split off completely from the magnesia compounds of the minerals but the calcium carbonate is only partially decomposed; the carbon dioxide is withdrawn from the heating zone at substantially the same rate as it is evolved by the heating minerals: the heated material is passed into a working zone into which some or all of the carbon dioxide withdrawn from the heating zone is also passed, and is there cooled in the presence of the carbon dioxide, whereby the calcium oxide produced by the partial decomposition of calcium carbonate and any calcium oxide admixed with the minerals are recarbonated. The recarbonated product may be hydrated, for which purpose bicarbonate-containing or lime saturated water and free carbon dioxide are preferably used. The product may be used in the treatment of water (see Group I) or as a carrier for metallic salts having an oligodynamic action. The product may undergo hydration and further carbonation by the action of bicarbonate-containing or lime-saturated water and carbon dioxide. Specifications 498,372 and 668,755 are referred to.ALSO:In a process for the production of a reaction product, consisting mainly of base calcium and magnesium compounds, from lime-containing and magnesia-containing minerals, preferably for use in water treatment, carbonate minerals such as, for example, dolomite, dolometic limestone, and calcareous magnesite, mixed if desired with calcium oxide, are heated in a heating zone, preferably in a double-drum rotary furnace, under such conditions that carbon dioxide is split off completely from the magnesia compounds of the minerals but the calcium carbonate is only partially decomposed; the carbon dioxide is withdrawn from the heating zone at substantially the same rate as it is resolved by the heating minerals; the heated material is passed into a cooling zone into which some or all of the carbon dioxide withdrawn from the heating zone is also passed, and is there cooled in the presence of the carbon dioxide, whereby the calcium oxide produced by the partial decomposition of calcium carbonate and any calcium oxide admixed with the minerals are recarbonated. The recarbonated product may be hydrated and further carbonated for which purpose bicarbonate-containing or lime-saturated water and free carbon dioxide are preferably used. The product is preferably used in granulated form as a filtering means for the de-aciditation of water, for the removal therefrom of iron or manganese, or in the form of an aqueous slurry as a precipitating or clarifying agent. The product may undergo hydration and further carbonation by the action of bicarbonate-containing or lime-saturated water and carbon dioxide, in which case a skin of precipitated calcium carbonate forms on the product. This skin is sparingly soluble in water and ensures that the water treated is not made too alkaline. The reaction product may be used as a carrier for metallic salts having an hydrodynamic action or may be used with chlorine compounds, with salts yielding up, or containing with oxygen, or with phosphate compounds, in the latter case for conditioning boiler feed water. Water chlorinated in excess when passed through the product has the excess chlorine removed. Oxygen or chlorine may be removed from aqueous solutions by embedding suitable metals in the reaction product whereby on contact of the product with water electric potential differences are set up to effect the desired removal. Specifications 498,372 and 668,755 are referred to.