MODERN METHODS OF PROCESSING DOLOMITE INTO MAGNESIUM AND CALCIUM COMPOUNDS WITH MINERAL ACIDS

Аннотация

Optimal conditions for obtaining granular and liquid nitrogen calcium and magnesium fertilizers, as well as Mg(OH)2 and MgO, by decomposing dolomite raw material with nitric acid to form a solution of Ca(NO ) and Mg(NO ) and ammonizing this solution 3 2 3 2 withammoniawere studied. Keywords: “Kaiser Refractories”, “magnetic” fire magnesite with large periclase grains, filter liquor, sea water and brines, carnallite, magnesite, dolomite, serpentinite, magnesium chloride, hydroxideandoxide, sodium sulfate and sodiumchloride. Dolomite flour is a raw material consisting mainly of CaCO ·MgCO , containing 3 3 approximately 20% MgO and 28% CaO. The residue remaining on a 0.25 mm sieve of class A dolomite flour should not exceed 32%, and in class B - not more than 60%. The content of the sum of calcium and magnesium carbonate salts is not less than 65%. Bulk density - 1.5 g/cm3. The fertilizer is used for liming acidic soils at a rate of 1.5-3 t/ha. At the same time, the soil is enriched with magnesium in sufficient quantities to feed plants during one or two rotations. Dolomiteflour istransported in bulkbyall types oftransport [1]. Magnesia with varying degrees of activity is obtained by precipitation of magnesium hydroxide and basic magnesium carbonates from solutions and subsequent heat treatment. By burning magnesite at relatively low temperatures (~ 700 °C) at high temperatures, heavy forms of magnesia are obtained from magnesite and dolomite, which contain all the impurities present in magnesite. Such magnesias, called "caustic magnesite", are used in the production of cement and building materials. When magnesite is burned at high temperatures (1500-1800 °C), an inactive form of magnesium oxide is formed, the general product of magnesium oxide processing is "magnetic" fire magnesite, consisting of large periclase grains, which is used for theproduction ofmetallurgical powder and refractory materials and products. According to statistics from 2010, 53% of magnesium crystals in the United States were used for the production of fire-resistant products, and the remaining 47% were used in agriculture, thechemical industry, construction, and environmental protection [2]. There are various methods for removing silicate compounds from dolomite and obtaining magnesium oxides. Thus, it was proposed to burn dolomite in a mixture of silicate and a small amount of iron oxide, which improves the synthesis of the raw material. After that, the boiled material is treated with water, and the main part of the CaO formed during the 426 INTERNATIONAL JOURNAL OF ARTIFICIAL INTELLIGENCE ISSN:2692-5206,ImpactFactor:12,23 AmericanAcademicpublishers,volume05,issue08,2025 Journal: https://www.academicpublishers.org/journals/index.php/ijai burning, which is not part of the ferrite, is wetted and washed. The latter is purified by separation of magnesium oxide and magnetite, then treated with hydrochloric acid to free it from Ca(OH) residues and thoroughly washed with water [3]. Also, at the Kaiser Refractories 2 plant (USA), crushed dolomite is separated from sand impurities in a separator filled with a crushed mixture of ferrosilicon and magnetite, through which compressed air is blown. The density of the mixture is 2.72-2.76 g/cm³, and the density of dolomite is 2.85 g/cm3; therefore, it sinks to the bottom and is removed, while sand and other lighter impurities remain on the surface of the material filling the separator. Dolomite is cleaned and washed from ferrosilicon and magnetite particles trapped in vibrating chambers. It is then fired in 91-meter-long rotary drum kilns, calcined to 1800 °C with the addition of 5% iron oxide to obtain high-density "burnt dolomite"; it is crushed and treated with petroleum bitumen at 80 °C to prevent hydration. This material is used as a metallurgical flux. Dolomite intended for the production of magnesium oxideisfired at atemperature not exceeding 1100°C. After the products obtained by burning magnesite and dolomite raw materials, it is possible to obtain light forms of magnesia from them by chemical processing of the residues. One of such processing methods uses the stages of transferring low-active magnesium oxide into a solution in the form of magnesium bicarbonate, followed by precipitation of active magnesium from it. The magnesium oxide obtained as a result of burning magnesite is crushed and quenched with water. The resulting suspension - milk of magnesia - is carbonized with carbon dioxide in autoclaves under a pressure of more than 5 atm. This is the process of producing amagnesium bicarbonate solution. Mg(OH) +2СО =Mg(HCO ) 2 2 3 2, After the magnesium bicarbonate solution is separated from the solid impurities, it is hydrolytically decomposed byboiling inthenext step: 2Mg(HCO ) = MgCO +Mg(OH) + 3СО +H O. 3 2 3 2 2 2 The resulting basic magnesium carbonate precipitate is separated and, after drying, is obtained in the form of a very fine powder - alba magnesia. Magnesia is also obtained