SU1745680A1 - Method of producing magnesium oxide - Google Patents

Abstract

Use: for protective coatings of transformer steel. The method involves the interaction of a solution of magnesium salts with an alkali metal carbonate, the separation of the resulting magnesium trihydrocarbonate, its washing and recrystallization into basic magnesium carbonate. In this case, the recrystallization is carried out from a suspension with a magnesium oxide content of 2.5–3.8 wt.%, Into which phosphoric acid in the amount of 14–16 kg per ton of magnesium oxide is introduced. To obtain the desired product, the basic carbonate is filtered off, washed, dried and calcined at 950 ° C.

Description

The invention relates to methods for producing magnesium oxide used for heat-resistant protective coatings of transformer steel,

The closest to the proposed method is the production of magnesium oxide, which includes the precipitation of magnesium trihydrocarbonate by reacting solutions of magnesium salts with an alkali metal carbonate for 30 minutes, separating the formed magnesium trihydrocarbonate (TGCM), washing it, recrystallizing in O KM their suspension containing MDO 6%, filtration and washing About KM, drying, classification and calcination of the fraction with a particle size of less than 45 microns at a temperature of 900 - 1000 ° C. Magnesium precipitation is 78%. The resulting magnesium oxide has a mass fraction of MDO 96.7 - 98.1%, the degree of hydration is 10.5 - 23%. Bulk weight (0.19 - 0.24.103 kg / m3. Adhesion is good. Coating is smooth. Content of CaO / MgO is 100% in product 2.0%. Mass

the amount of residue when sifting on sieve No. 0045 is 0.25-0.3%.

The disadvantage of this method is the high content of CaO impurities in the product, as well as a high bulk density and degree of hydration, which does not provide high-quality steel coating.

The purpose of the invention is to improve the quality of the coating by reducing the bulk density and the degree of hydration of magnesium oxide, as well as reducing the mass fraction of calcium oxide in it.

The method is carried out as follows.

Sivash brine with a mass concentration of 14.5 15.46 kg / m3 and soda solution with a mass concentration of N32C03 - 129.3 kg / m are continuously introduced into the reactor with a mechanical frame-type agitator. The temperature in the reactor is maintained equal to 26 - 28 ° C due to external heat supply. The residence time of the suspension in the reactor is 15-23 minutes. The amount of soda solution given relative to the magnesium in the brine is l &

2

(I

Och

00

about

em 50 - 80%. The reaction mixture — the slurry of the TGCM — is withdrawn from the reactor continuously for filtration in a submersible funnel and washing them with water to remove them, sulphate ions and alkali metals. The resulting paste TGKM mixed with water at the rate of obtaining a suspension with a mass fraction of MDO 2.5 - 5.73%, add 10% solution of phosphoric acid (7.6 -17 kg per 1 ton MDO), stirred for 60 minutes at 80 ° C with the aim of recrystallization TGKM in OKM. The suspension of the CMM is filtered off, washed with distilled water in a funnel and dried at 100-120 ° C. Dry magnesium carbonate is calcined at 950 ° C in a muffle furnace for 2 hours.

Using the proposed method for producing magnesium oxide with improved quality characteristics of CaO content, bulk density, degree of hydration allows to obtain a suspension of magnesium hydroxide to coat transformer steel, which prevents chemical interaction of impurities with steel.

Claims (1)

The proposed method allows to obtain magnesium oxide with a mass fraction of CaO of 0.29 - 0.35% (versus 2% by the known method), bulk density 78-149 kg / m (versus 190 - 240 kg / m, the degree of hydration is 0.1 - 3.0% (v. 10.5 - 23.0%). Claims of the method of producing magnesium oxide used for protective coatings of transformer steel, including the interaction of a solution of magnesium salts with an alkali metal carbonate, the separation of the resulting magnesium trihydrocarbonate, its washing and recrystallization at basic magnesium carbonate followed by filtration, washing, drying and calcining, characterized in that, in order to improve the quality of the coating by reducing the bulk density and degree hydration of the target product, recrystallization of the trihydrocarbonate magnesium is carried out from suspension with a mass fraction of magnesium oxide 2.5 - 3.8%. in which phosphoric acid is preliminarily introduced in an amount of 14-16 kg per ton of magnesium oxide.