Method of decomposing monazite

FIELD: chemistry.

SUBSTANCE: invention pertains to the technology of rare and radioactive elements; solves the problem of decomposing monazite. The method of decomposing monazite involves its treatment in molten salts at temperature ranging from 400°C to 900°C and phosphorous removal. The salts used during treatment are nitrates of alkaline metals (MeNO3), and phosphorous removal is done by separation of the clear phase of the smelt and/or lightening the phosphate of alkaline metal (Na or K) in a water solution.

EFFECT: low treatment temperature and provision for separation of phosphorous as a commercial product.

5 cl, 1 tbl, 6 ex

 

The claimed technical solution relates to technology of rare and radioactive elements can be used in the processing of phosphate rock.

In industrial practice are two methods of decomposition of monazite: acid and alkaline [1]. Sulfate way because of the bulkiness of the technological cycle, low purity rare earth products and problems associated with waste disposal, lost ground in favor of the alkaline method. The advantage of the latter is the allocation of phosphorus in the form of trisodium phosphate with high degree of purification from radionuclides [2]. Monazite process with continuous stirring 45%NaOH solution at 140°C for three hours. Use a three-fold excess of NaOH relative to theoretically necessary quantity. Decomposition of monazite reaches of 96.5%. The method is applicable when using crushed to 0.045 mm concentrate and indicators on the degree of decomposition is proportional to a first approximation the degree of development of the mineral surface, along with the duration of the process and is the main disadvantage.

The method for extracting rare earth metals from mineral phosphate [3], which includes sintering the raw material with carbon and additives, processing SPECA water and dissolved in mineral acid, characterized t is m, the sintering is carried out in the mode of self-propagating high temperature synthesis when used as an additive nitrate of an alkali metal. The dissolution of SPECA are in hydrochloric or nitric acid at a temperature of not lower than 70°and With a pressure of up to 15 ATM. Another difference is that the dissolution of SPECA is carried out in the presence of hydrogen peroxide or glucose. In accordance with the description method requires a preliminary grinding of monazite to a particle size of 0,063 mm, and in the process of self-propagating high temperature synthesis temperature in the reaction volume reaches more than 1000°C. From practice it is known that calcined at high temperature oxides of rare-earth metals and thorium difficultly soluble. Therefore, this method involves the use of autoclave processing for their subsequent transfer into the solution.

Also known is a method of processing monazite concentrate [4], including demostrazio concentrate by heating in a reducing environment in the presence of mineral solvent and extraction of the thorium component, characterized in that the extraction of thorium component is carried out by receiving a liquid bath of the melt, its settling and separation of light and heavy phases. To obtain a liquid bath of the melt using mineral solvent in an amount of 25-50% of the t mass of the bath. The separation of light and heavy phases performed in the molten state by flashing light or heavy phase. Possible separation of light and heavy phase after solidification of the melt. In addition, through the melt can be skipped constant electric current.

The latter was adopted as a prototype for the maximum matching essential attributes. The disadvantages of the prototype should be attributed to the high corrosivity of the reaction products resulting from the process of demostratsii melt at temperatures in excess of 1000°C. furthermore, the method does not provide phosphorus in the form of a commercial product.

The claimed technical solution is designed to eliminate the disadvantages of the prototype. This is achieved by the fact that as the reaction medium use structures on the basis of nitrates of alkali metals, and demostrazio carried out by separating the clarified melt and/or leaching of alkaline phosphate (Na or K) of the metal from the melt in a water solution.

The composition in the melt system MeNO3-TRPO4corresponds to a ratio of 1÷4-1 (wt.) in the temperature range of 750-900°C.

The composition in the melt system MeNO3-Meon-TRPO4corresponds to a ratio of 1÷4-0,5÷1,2÷1 (wt.) in the temperature range amounts to 400-650°C.

The composition in the melt system MeNO 3-Me2CO3-TRPO4corresponds to a ratio of 1÷4-0,5÷1,5÷1 (wt.) in the temperature range 650-800°C.

In addition, the suspension of the melt is subjected to intensive mixing, sludge and separating the clarified phase of the melt, and the suspension of the remainder of the melt is subjected to water leaching (TR - accepted designation of the amount of rare-earth metals, thorium and uranium in monazite Me - designation of the alkali metal Na or K).

The essence of the proposed technical solution is that the nitrate of the alkaline metal is used as the reaction medium, and as temperature increases consistently is its decomposition in two stages. The first stage is connected with the emission of oxygen and the formation of nitrite in the temperature range above 400°C. At temperatures near 900°completes the process of decomposition of nitrite with the formation of the oxide of the alkali metal, nitrogen and oxygen. Implemented alkaline variant decomposition of monazite and translation into water-soluble state phosphate compounds. If you enter in molten hydroxides of alkali metals, the process is accelerated and can be implemented in the range of lower temperatures. Carbonates of alkali metals, introduced in the original nitrate extend the temperature range of coexistence of the nitrates and carbonates. Demostrate the mode of contact of the remainder of the suspension of the melt with an aqueous solution simplifies the scheme as a whole and reduces the production cycle. The essence of the proposed method is confirmed by the examples.

Example 1.

For the decomposition of monazite in the molten salt was used in the pilot laboratory installation in the mine laboratory furnace with controlled temperature within 1000°, impeller stirrers for mixing the melt with reguliruemym number of revolutions. The decomposition was carried out in crucibles made of steel 18CR10NITI and cast iron up to 150 ml.

Demostrazio balance suspension melt after settling in "thermal shock" was carried out in a cylindrical tank with a volume of 500 ml, the Intensity of mixing in the tank to ensure acceptable conditions "thermal shock" was selected by changing the number of revolutions of the stirrer.

Sodium nitrate, potassium nitrate and other salts of the components previously dehydrated in a drying Cabinet at a temperature of 150°, melted directly in the reaction crucible at a temperature at temperatures above 400°. Used unground monazite composition: Σ RO - 54%, ThO2- 5.4%, SiO2- 4%, Fe2O33,6%, TiO2is 2.2%, CaO - 1,4%, ZrO2- 3%, Al2O3is 2.8%. The control process of decomposition of monazite was carried out by the mass loss of the solid phase after leaching water. The loss of mass during the decomposition of monazite is due to the formation of soluble phosphates of alkali metals, the oriy and rare earth elements remain predominantly in the solid phase in the form of insoluble oxides.

A portion of monazite covered in molten nitrate. Extract with stirring rasplavnoj suspension was 30 minutes. Granulation was carried out in a cylindrical vessel with stirring, a solution volume of 300 ml. phase Separation was achieved by sedimentation. For washing the solid phase used 100 ml of distilled water. Further drying of the solid phase and weighting. The rise of the temperature of the melt is reproduced in other conditions 100°and, repeating the above operations. The results of typical experiments decomposition of monazite in the melt of the source of nitrate are presented in table 1.

Table 1
Decomposition of the nitrates
№ p/pThe addition of nitrate, G.The addition of monazite, ,Process temperature, °The weight loss during leaching %Note
1NaNO345400not significanthigh viscosity
2KNO355400not significantthe process of sustainable
3NaNO310550 not significantthe process of sustainable
4KNO3155600not significantthe process of sustainable
5NaNO32057002,5the process of sustainable
6KNO32558007.6excess melt
7NaNO320590012,1the process of sustainable
8KNO315595012,05corrosion of the crucible

Example 2.

5 g of monazite were covered in a mixture of sodium nitrate (20 g) with sodium hydroxide and 5 g of extract for 1 hour without stirring of the melt. Temperature 500°C. Granulation in water volume of 300 ml. Selection of the solid phase quality filtering. Rinsing with 100 ml of water. Drying the precipitate. The loss of mass of the solid phase 7% (0.35 g).

Example 3.

5 g of monazite covered in molten potassium nitrate (20 g) with potassium hydroxide. Conditions identical to example 2. Exposure for 0.5 hours in the melt with stirring by a stirrer. The loss of mass of the solid phase of 7.8% (0.39 g).

Example 4.

Conditions are identical when the ERU 2,3. Exposure for 0.5 hours in the melt with stirring by a stirrer. Temperature 600°C. the weight Loss of the solid phase of 10.1% (worn : 0.505 g).

Example 5.

5 g of monazite within 2 minutes evenly covered in a mixture of potassium nitrate (20 g) and potassium carbonate (5 g) under stirring, the temperature of 800°C, holding for 20 minutes.

The loss of mass of the solid phase of 12.2% (0,61 g). The washed dispersion part of the precipitate results of x-ray phase analysis phase mixed cerium-face oxide composition Ce0,5Th0,5O2. Coarse residue traces of monazite, quartz, mixed cerium-thorium oxide composition Ce0,75Thof 0.25O1,89.

Example 6.

Conditions identical to example 5, was used a mixture of sodium nitrate (20 g) and sodium carbonate (6 g). Temperature 900°C. the Crystalline residue is represented mainly by monopati quartz. The loss of mass of the solid phase in aqueous leaching of 12.4%.

In the presented examples, the source monazite had an average grain size of 300-400 microns, pre-grinding is not used. During processing in the melt salts revealed the formation of the dispersed phase mixed oxide with a particle size of 30-50 MK, does not contain phosphates. Silicon in the form of quartz is practically not affected by destructive changes and can be removed from process classification cat is used according to the size of the particles. In General, the claimed technical solution can become the basis for the development of effective and environmentally safe production of rare earth products and thorium compounds.

Sources of information

1. Kaplan G. and other Thorium, its raw materials, chemistry and technology. - Ed. The state Committee of the USSR on the use of nuclear energy, 1960.

2. Smirnov, Y., Efimova THE Nuclear technology abroad. 1961, No. 2. p.20-29.

3. Pat. Of the Russian Federation No. 2092602, the Method of extracting rare earth metals from mineral phosphate, priority from 21.03.96.

4. Application No. 94026007, a Method of processing monazite concentrate, publication from 06.10.96.

1. The method of decomposition of monazite, including the processing in the molten salt and demostrazio, characterized in that the processing in the form of salts use nitrates of alkali metals (MeNO3), and demostrazio carried out by separating the clarified phase of the melt and/or leaching of phosphate of an alkali metal (Na or K) in aqueous solution.

2. The method according to claim 1, characterized in that the processing is carried out at a ratio in the melt MeNO3to the amount of phosphates of rare-earth metals, thorium and uranium (TRPO4) (1-4):1 (wt.) in the temperature range 750-950°C.

3. The method according to claim 1, wherein the treatment is carried out by introducing into the molten salt of alkali metal hydroxide (Meon) at a ratio of MeNO3 :Meon:TRPO4(1-4):(0,5-1,2):1 (wt.) in the temperature range amounts to 400-650°C.

4. The method according to claim 1, wherein the treatment is carried out by introducing into the molten salt of a carbonate of an alkali metal (Me2CO3) at a ratio of MeNO3:IU2CO3:TRPO4(1-4):(0,5-1,5):1 (wt.) in the temperature range 650-800°C.

5. The method according to any one of claims 1 to 4, characterized in that the processing of the melt is subjected to intensive mixing, the resulting slurry defend, separating the clarified phase of the melt, and water leaching is subjected to suspension the rest of the melt.



 

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1 tbl, 1 ex

FIELD: metallurgy; hydrochemical methods of a complex processing of a multicomponent, polymetallic scrap.

SUBSTANCE: the invention is pertaining to the field of metallurgy, in particular, to the hydrochemical methods of a complex processing of a multicomponent, polymetallic scrap used in nonferrous metallurgy with extraction of valuable components and production of various commercial products. The technical result at reprocessing and neutralization of wastes of production of titanium tetrachloride consists in concentration of radioactive metals in the "head" of the process, transfer of the secondary wastes of production in an ecologically secure form suitable for a long-term entombment and-or storing, as well as in production of an additional commercial products - deficient and expensive black thermo- resistant inorganic pigments based on iron oxides, manganese and copper oxides. The method provides for a discharge of the spent melt of titanium chlorates into water; concentrating of a pulp by circulation; the pulp thickening; settling of metals oxyhydrates from the clarified solutions in succession in three stages: on the first stage - conduct a settling at pH = 3.-5.0 with separation of the formed settling of hydroxides of chrome, aluminum and scandium from the solution; on the second stage - conduct settling at presence of an oxidizing agent at pH = 2.5-3.5 within 20-50 hours with separation of the settling; on the third stage - conduct settling at pH = 9.5-11.0. The pulp at its circulation and concentration is added with sodium sulfite in amount of 5 - 15 g/dm3, then after circulation the pulp is treated with a solution of barium chloride in amount of 10-20 g/dm3 for cosettling of ions of thorium and radium, in the formed pulp of the first stage of settling introduce a high-molecular flocculant, and before settling process on the third stage of the process the solution is previously mixed with copper(II)-containing solution formed after lixiviation of a fusion cake of the process of cleanout of the industrial titanium tetrachloride from vanadium oxychloride by copper powder, then the produced settling of iron, manganese and copper oxyhydrates is filtered off, cleansed, dried and calcined at the temperature of 400-700°C.

EFFECT: the invention allows to concentrate radioactive metals in the "head" of the process, to transfer the process secondary wastes in the ecologically secure deficient and expensive black thermo-resistant inorganic pigments.

5 cl, 1 ex

FIELD: non-iron metallurgy, in particular scandium oxide recovery from industrial waste.

SUBSTANCE: method for preparation of scandium oxide from red mud being waste of alumina production includes: multiple subsequent leaching of red mud with mixture of sodium carbonate and hydrocarbonate solutions; washing and precipitate separation; addition into obtained solution zinc oxide, dissolved in sodium hydroxide; solution holding at elevated temperature under agitation; precipitate separation and treatment with sodium hydroxide solution at boiling temperature; separation, washing, and drying of obtained product followed by scandium oxide recovery using known methods. Leaching is carried out by passing through mixture of sodium carbonate and hydrocarbonate solutions gas-air mixture containing 10-17 vol.% of carbon dioxide, and repeated up to scandium oxide concentration not less than 50 g/m3; solid sodium hydroxide is introduced into solution to adjust concentration up to 2-3.5 g/m3 as calculated to Na2O (caustic); and mixture is hold at >=800C followed by flocculating agent addition, holding, and separation of precipitate being a titanium concentrate. Obtained mixture is electrolyzed with solid electrode, cathode current density of 2-4 A/dm3, at 50-750C for 1-2 h to purify from impurities. Zinc oxide solution in sodium hydroxide is added into purified after electrolysis solution up to ratio ZnO/Sc2O3 = (10-25):1, and flocculating agent is introduced. Solution is hold at 100-1020C for 4-8 h. Separated precipitate is treated with 5-12 % sodium hydroxide solution, flocculating agent is introduced again in amount of 2-3 g/m3, mixture is hold, and precipitate is separated. Method of present invention is useful in bauxite reprocessing to obtain alumina.

EFFECT: improved recovery ratio of finished product into concentrate; decreased impurity concentration in concentrate, reduced sodium hydrocarbonate consumption, as well as reduced process time due to decreased time of fine-dispersed precipitate.

2 cl, 2 ex

FIELD: metallurgy; reworking wastes of alumina production process.

SUBSTANCE: proposed method includes preparation of batch of charge containing red mud and carbon reductant, heating the charge in melting unit to solid-phase iron reduction temperature, three-phase reduction of ferric oxides in charge by carbon reductant and saturation of iron with carbon in charge thus prepared, melting the reduced charge for obtaining metal phase in form of cast iron and slag phase in form of primary slag, separation of cast iron from primary slag in melt heated to temperature of 40 C, reduction of silicon and titanium from oxides contained in primary slag by aluminum and removal of cast iron and primary slag from melting unit; during preparation of charge, concentrate of titanomagnetite ore containing titanium oxide in the amount from 1 to 15% is added to red mud; besides that, additional amount of carbon reductant and additives are introduced; after separation of primary slag from cast iron in melting unit, cast iron is heated to 1500-1550 C and product containing ferric oxide is added to it; iron is reduced by carbon of cast iron for converting the cast iron into steel at obtaining secondary slag; main portion of steel is removed from melting unit, secondary slag is added to primary slag and silicon and titanium are converted into steel residue in melting unit by reduction with aluminum, thus obtaining final slag-saturated slag and master alloy containing iron, titanium and silicon; main portion of master alloy is removed from melting unit; after removal of final slag for converting the master alloy residue to steel in melting unit, titanium and silicon are converted into slag phase by oxidation and next portion of charge is fed to slag phase formed after converting the master alloy residue to steel. Proposed method ensures high efficiency due to obtaining iron-titanium silicon master alloy in form of independent product and production of alumina from high-alumina final slag or high-alumina cement and concentrate of rare-earth metals.

EFFECT: enhanced efficiency due to avoidance of intermediate remelting of steel.

10 cl, 2 dwg

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