No abstract

The demand for periclase and refractories made from magnesium oxide with a purity of 98-99% is rather high. It is possible to use Volgograd bischofite as a highly effective raw material for the production of magnesia of this purity.The Volgograd deposits of bischofite (MgCI2*6H20) constitute unique sources, both in terms of reserves, and also the quality of the magnesium chloride (95-98%). Moreover, it has a high concentration of bromine, 5-8 kg per m 3 of ore [i]. Note has been made of the need for all-round development of the bischofite with the production, primarily, of bromine and magnesia. The density of the liquhrs of the underground solution of bischofite is 1.29- The organization of large-tonnage production should be preceded by a range of investigational work in order to develop the technology and equipment specifications of the process.In this article we describe the results of obtaining, by the thermohydrolysis method, from Volgograd bischofite that has not been debrominized, magnesium oxide and periclase refractories based on it.The Combine received two cisterns of bischofite liquor (78. Magnesium, calcium, and iron were determine according to GOST 844-79, GOST 25423.4-80, and GOST 844-79, the alkaline elements --with the atomic-absorption method on the flame spectrophotometer "Saturn"; the sulfates were determined according to GOST 844-79, the chlorides using the Folgardt method [2], the silicon dioxide --according to GOST 24523.1-80. the residues insoluble in HCI (inorganic) according to GOST 844-79, and the boron by the volumetric method [3].

The essence of the industrial hydrochloric acid conversion of natural magnesium-containing raw material into high-quality MgO is well known. The original material is treated in HCI, and then the magnesium chloride solution so formed is freed of impurities and hydrolyzed by heating. The so-called hydrolytic MgO obtained in this way is freed from the remaining impurities and the oxide converted to magnesium hydroxide. Next, the magnesium hydroxide is briquetted. The briquettes are sintered or fused and then milled down to obtain a powder of the required grain composition [1][2][3][4][5].One feature of the HCI treatment of magnesite is the possibility of using the main mass of HCI in a closed cycle. Regeneration of the HCI takes place during the thermal hydrolysis of the purified solution of magnesium chloride. In accordance with the plan drawn up by the Eastern Institute of Refractories and the Ukrainian Institute of Chemistry, a pilot plant has been built at the Magnesite Combine; this has been mastered and is used for the hydrochloric acid treatment of magnesite; the annual productivity of the equipment is 400 tons.In [6] some features of the process of dissolution of natural and caustic magnesite in HCI and the sintering of the beneficiated product [7] have been considered. The present article pays particular attention to the apparatus-process character and considers in more detail the hydrolysis of magnesium chloride.The outline of the process of this stage of beneficiation of magnesite on the plant is shown in Fig. i. The chloride solution at a concentration of ~150 g/liter (relative to MgCI2) after being freed from impurity Fe, AI, and Si comes from the preparation and solution-purifying stage to the recuperator for preliminary concentration. The concentrate formed (concentration of MgCI2 = 300-350 g/liter) is sent from the collector tank to the atomizing spray reactor, in which the thermal hydrolysis of the MgCI= takes place in accordance with the reactions Some of the solid product settles in the conical bottom of the reactor, and the rest is removed as a gas product to the cyclone from where it is returned to the atomizing reactor via the overflow. The off-loading of the hydrolytic MgCI2 is done from the bottom. As the heat-carrying reagent we use the combustion products of natural gas. The gaseous reaction products free of solid phase and at a temperature of 250-300~ reach the recuperator where, after giving out some of the heat in the evaporation of the initial MgCI2 solution, are cooled to 90~The gas then goes to the absorption column, where the HCI is absorbed and hydrochloric acid is formed. The scrubber column and the spray collector are used as further means of purifying the gas products of the reaction by removing the HC1. The whole system is operated under low pressure which is created by the vacuum pump. The gas products with the dust and HCI removed are dispersed into the outside atmosphere. The HCI obtained is returned to the preparation stage for the purification of the solution, while the hyd...