CZ107692A3 - Production of magnesium carbonate from raw materials leached with ammonium sulfate - Google Patents

Abstract

The method consists in that for decomposing the raw materials magnesium oxide was used at 8-35 ammonium sulfate % by weight at the boiling point of the reaction mixture so as to evaporate 80% of the inlet solution volume. The gases are treated in a distillation column for water with low ammonia concentration and ammonia containing 110-130 g / l of ammonia from which it is produced ammonium carbonate to precipitate magnesium carbonate.

Description

The present invention relates to a process for the preparation of pure anhydrous magnesium carbonate from industrially produced crude magnesium oxides-caustics using ammonium sulfate leaching agents.

BACKGROUND OF THE INVENTION

The industrially produced magnesium oxide - caustic is contaminated with calcium, iron, manganese, aluminum and silicon compounds. The refining is industrially performed by dissolving solid magnesium oxide using hydrochloric acid or ammonium chloride solution. The dissolved admixtures are excised from the solution and separated from the refined solution. The magnesium is separated from the solution in the form of insoluble carbonate or hydroxide with the exception of impurities, which are then used to prepare other magnesium compounds. The solutions are also processed to crystalline or free magnesium chloride. The chloride environment is highly aggressive towards metallic materials, especially at elevated temperatures and high chloride concentrations, causing significant losses of material, point corrosion, brittleness of material and therefore it is necessary to use rubber, enamel, teflon protection or special cuts of alloy steel or copper alloys .

SUMMARY OF THE INVENTION

It is an object of the present invention to use ammonium sulfate solutions to convert magnesium into a solution and to build a process line for the production of anhydrous magnesium carbonate which allows the circulation of leaching and precipitation substances and the reduction of wastewater contamination.

The decomposition of the raw material and the magnesium oxide content is carried out in

9 - 35% magnesium sulphate solution at 120% equivalence to magnesium oxide at boiling point of 102 ° C. . The raw material is decomposed on multi-stage, agitated apparatuses with a sufficiently dimensioned heating surface. The gases of the reaction are treated on a distillation column, which ensures the preparation of sufficiently concentrated ammonia water for the preparation of ammonium carbonate (UH) and water with low ammonia content. This is used to dilute the leaching solution and to wash the solids. The leaching slurry is saturated with gaseous carbon dioxide in a turbine stirrer reactor to reduce the calcium content. The solution is separated from the solid phase and passed to the autoleage together with a solution of ammonium carbonate (or a mixture of carbon dioxide and ammonia) in which anhydrous magnesium carbonate is precipitated at 140-160 ° C. After cooling, the solution is separated from the solid phase and returned to the leaching agent reservoir. The solid-phase was. washed, dried and stored according to Dotreoy. The ammonia water obtained from the leaching is used for the addition of ammonium carbonate. It is prepared by hissing ammonia water with carbon dioxide in the absorption column to a concentration of 300 g / l. Unreacted raw material is washed and deposited or processed to solid state materials with Sorel cements.

Individual apparatuses are made-of materials with rubber protection, possibly smatnímnim, or are made of materials CSN tr 17 347.

Individual operations are governed by the equations:

MgO + NH ^ _4/2 S5 ₄ ====== _MgSO4 + 2NH ₃ + HgO

CaO + / NH ₄ / SO _{4 2} ====== time3 ₄ + 2NH ₃ + H ₂ 0

FeO, MnO, SiOgjAl ^ o ^ + / NH _4/2 SO ₄ ====== insoluble

CaSO ₃ + CO ₂ + MgO ======== CaCO ₃ + MgSO ₄

_MgCl2 + / NH _4/3, 2C3 ======== MgC0 ₃ + / NH _4/2 S3 ₄

2Nfí ₄ 3H ₂ + CO ======== / NH _4/2 C3 ₃ F HJO

The advantages that are associated with the use of ammonium sulfate leach are as follows:

There is no leaching of iron, manganese, aluminum, silicon into the solution.

The solubility of calcium sulfate against chloride is very low and is suppressed by the concentration of sulfates in the carrier solution.

Due to the lower thermal coloration of the reaction, a higher leaching rate than chloride will be achieved

Reduces ae boiling points of solutions, resulting in energy savings for heating Sulfate environment reduces corrosion demands

The sulphate ion can be kept low in water The disadvantage is the reduced solubility of magnesium sulphate Explanation of the attached drawing

In the magazine 1. When the feedstock S is supplied from the container 2, for the ammonium sulphate leacher and the container 1, the components are metered into the heated stirred reactor 3, overflowing to the second stage of the reactor 4. The reacted material is fed to The filtrate is stored in a reservoir 17 from which it is dispensed into a stirred, discharged autoclave. The wash water is stored in a reservoir 16 from which it is used for preparing the solutions in 1. The off-gases from the 3rd and 4th are fed to a distillation column 5. The ammonia distilled off is passed to the absorption 9. The produced ammonium carbonate is stored in a storage tank 10. From there it is metered into the autoclave 11. device 12.a pran37 * 13. The collected solution is returned to the container 2. The wash water is recovered from the container 16. and the spent water is returned to the container 2. The washed precipitate is dried in an oven 14 and filled into containers in line 19. Excess water is drained from the container. Waste from 8. is exported to a landfill or processed into Sorel cement.

DETAILED DESCRIPTION OF THE INVENTION

A suspension of 105 g of caustic, 369 g of ammonium sulfate was prepared to a volume of 4390 ml. The slurry was fed into a two-stage reactor heated to boiling point I stage 97C II. degree 102 ° C. The suspension was dosed at 1,380 ml / h. The reactors are stirred, heated at 4000 and 3000 ml.

The gas is taken from each stage separately. Evaporator controlled by heating input to reach 80% of input volume. The reactors are left in operation to establish equilibrium in the individual parts of the plant. The leachate contained 53.4 g / l Mg, 0.8 g / l Ca, Fe, Mn, SiO 2 Al ₂ O, in feet, NH. 16.8 g / l NIL · 0.3 g / l. Water was added to the reactors at once 300 ml / hr. 87% magnesium blowdown is achieved, into a solution which has an increasing tendency. 492.6 ml of condensate containing 28.2 g / l NIL · and II. degree 492.6 ml 7 g / l NIL ·, part of the ammonia leaked in the apparatus. ^J

The leaching material used was 89.12% MgO, 1.51% CaO 2% SiO ₂ , 0.52% 4.46% Fe 2 O, 1.59% CO 3, 0.032% Na

Calcium carbonate precipitation is performed in a ^J 1000 ml stirred reaktorku blowing carbon dioxide and maintained the solution pH 6 «= 7, achieved with a reduced concentration to a value of 0.3 g / 1 ca.

The ammonium carbonate precipitation solution was prepared by saturating ammonia water with 110 g / l carbon dioxide to a charge of 162.5 g / l CO and 8 g / l NH 3 free base. 820 ml of this solution was mixed with 3000 ml of magnesium sulfate solution, heated to 150 ° C in an autoclave, and left at room temperature for 2 hours. The solution was cooled, filtered, and the precipitate dried at 10 ° C. The precipitate contained 27.3% Mg, 0.5% Ca, the return solution contained 1.3 g / l Mg, 1.5 g / l NH, 1.4 g / l CO2.

Industrial use

Refined white carbonate is used in the printing, paper, rubber and medical industries. The product is used for the preparation of other magnesium chemicals. Annealing yields magnesium oxide, which is also an important raw material for the various industries.

Claims (2)

ΡΙΤΕΝΙΟΥΪ Ν Β Β Ο Υ Process for producing magnesium carbonate characterized in that ammonium sulphate at concentrations of 8-35% by weight, at the boiling point of the solutions, is evaporated with 80% of the inlet volume of the solution to decompose the magnesium oxide-containing raw materials. 2. A process for producing anhydrous magnesium carbonate, characterized in that a continuous line formed from a multiple reactor is used to decompose the feedstock with a solution. ammonium sulphate with heat supply for evaporation of water and ammonia, the off-gases are treated in a distillation column to water with low ammonia concentration and water containing 110-130 g / l of ammonia, which is used for carbon dioxide absorption, the resulting ammonium carbonate is used as a precipitation The precipitation of magnesium carbonate is carried out in a reactor at a temperature of about 150 DEG-60 DEG C. and a pressure of 0.7-1.2 lPa, the resulting precipitation is separated, dried, returned to the decomposition reactors, unreacted. parts of the raw material are washed with distillation water or processed into a solid mass like Sorel cement and are the only waste from the line, the excess water is removed from the distillation »