FI80437C - FOERFARANDE FOER FRAMSTAELLNING AV ETT ALKALIMETALLHYDROALUMINAT. - Google Patents

Description

1 80437

This invention relates to the preparation of inorganic materials, and more particularly to the preparation of an aluminum-containing raw material into alumina, soda ash and potash; more specifically, it relates to a process for the preparation of an alkali metal dihydroaluminate.

AI is a wide field of application for hydroaluminium alumina, used in the papermaking industry as a substitute for resin mucilage, as a flocculant in wastewater and drinking water treatment, as a soil stabilizer in the civil engineering industry, as a tower material in the sediment industry, in oil drilling as a sludge component and others.

A process for the preparation of sodium hydroaluminate is known in the art, in which a silicate solution having a molar ratio of sodium oxide to alumina of Na 2 O: Al 2 O 3 = 7 and obtained by alkali extraction of an alumina silicate raw material is silicate and then evaporated to 20-40% Na 2 O. N a 2O: 350-575 g / l); To the evaporated solution is added a portion of sodium hydroaluminate (Na 2 O.A 2 • 3.2.5H 2 O) and cooled to 20-60 ° C to crystallize the sodium hydroaluminate from the solution, after which the crystalline product is separated from the mother liquor / cf. U.S. Patent No. 3,998,927 (1) 7 · Although the yield of the product in this process is high (80%), the process is complicated in terms of evaporation equipment (since the material of the equipment must be a corrosion-resistant material) and thickening of solutions to a concentration 575 g / l Na 2 O consume a lot of energy.

It is known below to produce the product by evaporating the silicate-depleted aluminate solution obtained from the extraction of an aluminum-containing raw material in the production of alumina with a molar ratio of alumina to alumina of Me 2 O: Al 2 O 3 of 2.3-3.6. At a temperature of 116-140 ° C, the temperature of the metal oxide was to be 400-550 g / l Me 2 O. Evaporation of an aluminate solution having a composition as defined above corrodes process 1 equipment made of ordinary steel, which is not permissible in the art. In the corrosion process, the deep corrosion index increases from 8.5 mm to 34 mm per year / herb. A.I.Liner: "Manufacture of Alumina", 1961, Moscow, Metallurgiya Publishers, ss. 82, 292, 354-355 (2); "Metallurgist's Handbook on Non-Ferrous Metals", Agranovsky A.A. et al, 1970, Moscow, Metallurgical Publishers, pp. 91 (3) /.

An attempt has been made to improve the process for preparing imetalohydroaluminate from an aluminate solution by evaporating and crystallizing it in order to increase the yield of the product and to separate the mother liquor from the desired product / herb. Proceedings of the All-Union Aluminum-and-Magnesium Institute, No. 70, G.A. Panasko, M.I. Smirnov: "Production of sodium caustic alkali from mixed aluminate solutions", 1970, Moscow, Metallurgiya Publishers, pp. 126-135 (4) and V.S.

Sazhin: "New Hydrochemical Processes for the Production of Alumina", 1979, Naukova Dumka Publishers, pp. 125-126, 130, 135, 208 (517-

In one attempt, it was a method of evaporating a silicate-depleted aluminate solution with a molar ratio of Μβ2θ: Αΐ2θ3 of more than 3.4 to a concentration of 500-510 g / l

Me 2 O, after which the solution is crystallized at a temperature in the range of 30-90 ° C. However, this attempt proved to be a failure. When the solution is crystallized at 30 ° C, an excessively thick and viscous slurry is formed which cannot be separated into a solid residue and an mother liquor, and thus the alkali component cannot be recovered from the mother liquor. This results in additional consumption of the agar reagent used in the raw material extraction step. Although the yield of the final product is high (about 80%), it has a high moisture content, which requires more energy to dry.

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When the aluminate solution having the composition defined above is crystallized at a temperature of about 90 ° C, the yield of the final product is low (about 60 ° C).

In another attempt to improve the yield of the final product and the separation of the mother liquor, the preparation of the imetal 1 skin hydroaluminate from the silicate-depleted alumina solution with a molar ratio of Me 2 O: Al 2 O 3 of about 2.3 was carried out by evaporation to 400-450 g / ml. 1 Me 2 O, after which the crystallization was carried out at 50-70 ° C for 1-2 hours and then the solution was filtered and the mother liquor was separated. Although this method separates the aliohydroaluminate from the mother liquor, the yield of the final product is low (about 60%). Attempts to improve the yield of the desired product by deep evaporation of the aluminate solution to a dipole content of 450-510 g / l Me 2 O, irrigating the evaporated solution at 30 ° C and then filtering the aluminate obtained have proved ineffective. The desired product contains too much mother liquor which cannot be completely separated from the final product, thus deteriorating the quality of the desired product.

It is known to prepare at least imetal 1 skin hydroaluminate from an aluminate solution having a molar ratio of Me 2 O: Al 2 O 3 of 8 by removing the silicate and then evaporating the alkali metal oxide to a concentration of 460-540 g / l Me 2 O / L.P. Nee, L.G. Romanov: "Physico-Chemistry of Hydroalkain Processes of Alumina Production", 1975, Alma-Ata, Nauka Publishers, pp. 237 (6) J. The product obtained is pasty and has poor filtration properties.

Although the yield of the final product is as high as 70%, the moisture content of the product is high because it contains too much mother liquor, as evidenced by the molar ratio of alumina to alumina in the product Me 2 O 2 O 3 = 2.2. This moist product is difficult to handle and transport.

4,80437

A process for the preparation of sodium hydroaluminate from an aluminate solution is known in the art, in which the silicate-depleted aluminate solution has a sodium oxide content of 100 to 350 g / l Na 2 O and a molar ratio of

NagOrAlgOj is 1.6, a drying-granulation treatment is carried out in a 1 e i fluidized bed apparatus in the temperature range of 250-350 ° C for a duration of 3 minutes. Hot air from which carbon dioxide has been purified is used as a heating agent in the drying. The product obtained comprises dry sodium aluminate granules / herb. SU Inventor Certificate No. 345 767 (7) 2 · In this method, the manufacturing costs of the product are high because the crystallization and dewatering of sodium aluminate is carried out in a furnace unit with high consumption of energy, heat and capital goods. The commercial use of the method still involves a large dedusting of the furnace unit (27%).

Thus, there is still a lack in the art of a process for the production of imetal1hydroaluminate which is simpler in performance, has a higher yield and a better quality solid end product while reducing energy consumption.

The object of the present invention is to provide a process for the production of alkali metal hydroaluminate which makes it possible to keep energy costs to a minimum, to simplify the procedure and to improve the yield, and to improve the quality of the final product.

This object is achieved by a process for the preparation of alumina hydroaluminate, which comprises the following steps: - the starting material containing alumina and an alkali metal oxide is extracted to obtain an aluminate solution; - the silicate is removed from the aluminate solution; - the silicate-depleted aluminate solution is evaporated; - the alpha-metal hydroaluminate is crystallized from an evaporated aluminate solution, in which process, according to the invention, the aluminate is evaporated;

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80437 a solution in which the molar ratio of kaiβ2θ to θ2θ3 of a22θ: θ2θ3 is 1.1 to 1.7, and the evaporation is carried out at a temperature in the range from 120 to 150 [deg.] C. to a metal oxide content of 350 to 400 g / l; crystallization of the non-metallic hydroaluminate from the evaporated solution is carried out by feeding this solution at a temperature of 95-150 ° C to a mobile filter surface having a temperature in the range of 10-95 ° C, after which the product is crystallized and separated from the mother liquor; - the obtained mother liquor is recycled back to the starting material extraction step.

The process of the present invention simplifies the formula, minimizes energy consumption in the evaporation and crystallization steps, increases product yield and quality, and reduces reagent consumption.

It is desirable that the evaporation process of the aluminate solution be performed in two steps: in the first step, the evaporation of the solution is performed at a temperature of 120 ° C to an alkali metal oxide content of 225-230 g / l Μβ2θ; in the second step, the evaporation is carried out at a temperature of 150 ° C to an alkali metal oxide content of 360-370 g / l Me 2 O. This two-stage evaporation method is more economical, i.e. it uses less heating medium (steam).

It is desirable to keep the aluminate solution at 95-105 ° C for 2-3 hours after the second evaporation step (in order to bring the initial metal oxide content of the solution to 385-395 g / l Me 2 O). This method gives better conditions for crystallization of the product and better yield.

The crystallization is carried out on a mobile filtration surface 1a with a temperature of 20-50 ° C, where it is most easily maintained under industrial conditions. Al imetal11hydroaluminate crystallizes rapidly and separates from the mother liquor on the filtration surface.

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As the filter surface, any polyamide fiber, woven metal mesh and other suitable filter materials can be used.

These and other advantages of the present invention will become more apparent from the following detailed description of an alloy metal hydroaluminate production method and the best embodiment thereof.

An aluminum-containing raw material, such as nepheline and limestone, is comminuted into particles with a size of 80-95. The charge is prepared by mixing nepheline, limestone and an alkaline solution in such amounts that the molar ratio of oxides in the charge CaOiSiOg = 2.1: 1 and Μβ2θ: (Al 2 ^ 3 ^ 6203) 0.95-1, where Me is Na, K. The sinter obtained crushed and extracted with a solution containing g / l: Al 2® 3: 14-30, Μβ2θ: 35-36.5, S i 0 2: 0.5-0.7 in a molar ratio of Me 2 O: Al 2 O 3 of 1.63- 4.2. From this extraction of the raw material containing alumina and alumina, an aluminate solution is obtained in which the molar ratio of alumina and alumina Me 2 O: Al 2 O 3 is 1.1-1.7. The resulting aluminate solution is filtered to separate the slurry and the silicate is removed to give a residual SiO 2 content of 0.05-0.07 g / l. The white slurry from the silicate removal is separated and recycled back to the batch preparation step.

Most of the silicate-depleted aluminate solution obtained is directed to the production of alumina, potash and soda, while the rest of the solution is used for the production of alkali metal hydroaluminate.

In the aluminate solution fed for the preparation of Al catallic hydroaluminate, the molar ratio of Al 2 O 3 to Al 2 O 3 of Al 2 O should be 1.1-1.7. This molar ratio of alkali metal oxide to alumina is obtained in the raw material extraction step with a solution having the composition defined above, namely: Al 2 O 3: 14-30 g / l, Me 2 O: 35-36.5 g / l, S i 0 2: 0, 5-0.7 g / l, and the molar ratio Me 2 O: Al 2 O 3 = 1.63-4.2.

According to the present invention, a solution of aluminate 1 having a molar ratio Μβ2θ: Αΐ2θ3 = 1.1-1.7 is evaporated at a temperature of 120-150 ° C to a metal oxide content of 350-400 g / l Me 2 O.

The evaporated aluminate solution does not corrode an evaporation apparatus made of ordinary steel, which is one of the advantages of the invention, since an evaporation apparatus made of low-cost steel can be used, thereby reducing the manufacturing cost of the desired product. The fact that the evaporated aluminate solution does not cause corrosion is due to the fact that the alumina metal oxides are in the chemically bound state in the solution as aluminate ions.

The use of an aluminate solution with a molar ratio of Me 2 O: Al 2 O 3 of more than 1.7 is not desirable, since an aluminate solution having such a composition is close to the stability solution of the Me 2 O 2 Al 2 O 3 -H 2 O system at a temperature of 120-150 ° C, making the product very difficult. recover from it by crystallization.

The use of an aluminate solution with a molar ratio of Me 2 O: Al 2 O 3 of less than 1.3 is also not desirable, since the solution having a composition is in the region of the Me 2 O-Al 2 O 3 -H 2 O system which is supersaturated with imetalohydroaluminate at a temperature of 120-150 ° C. . The crystallization of the product from such a solution takes place very quickly, whereby the precipitated product clogs the evaporation equipment.

Therefore, according to the present invention, the aluminate solution is evaporated in which the molar ratio Μβ2θ: Αΐ2θ3 is 1.1-1.7. Evaporation of such a solution under the conditions defined above forms a saturated solution of non-metallic hydroaluminate. This solution, which has a temperature of 95-150 ° C, is crystallized by charging it on a mobile filter surface having a temperature of 10-95 ° C.

As a result of this crystallization method, the aluminate solution separates in a blink of an eye, directly from the filtration surface to a solid component, aliquot imetalohydroaluminate, and mother liquor. Since the aluminate solution is fed to the filter surface at a temperature of 95-150 ° C, this surface is heated. In order to keep the filtration surface at a temperature of 10-95 ° C, it must be cooled. Cooling of the filter surface is accomplished by supplying a coolant, mainly water, to its non-working surface. By feeding cold (+ 5 ° C) water, the temperature of the filtration surface is reduced to 10 ° C.

Heating the filter surface above 95 ° C slows down the crystallization rate, making the crystallization process of the product unprofitable.

When the filter surface is cooled to a temperature below 10 ° C, the viscosity of the aluminate solution increases, causing a "karstic" residue to form on the filter surface, which inhibits the crystallization process. Ignoring the temperature limits of the filter surface thus causes disturbances in the crystallization process and does not achieve the desired result.

As already mentioned above, at the filtration surface having a temperature of 10 to 95 ° C, rapid crystallization occurs as the metal hydroleaminate separates from the mother liquor.

The mother liquor obtained according to the present invention is directed to the raw material extraction step. This procedure makes it possible to regenerate the aliquot component and thus to reduce the amounts of components used in the extraction step.

As the filter surface, polyamide fiber fabric a, metal mesh fabric and other suitable filter materials can be used.

By using a filtration surface to carry out the crystallization process, energy consumption can be significantly reduced by supplying cold water as a coolant to keep the filtration surface in the temperature range of 10-95 ° C.

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The resulting metal hydrohaluminate is a commercial product. It is a uniform white crystalline solid which is the salt of an alkali metal and aluminum acid corresponding to the formula: Μθ2θ.Αΐ2θ3 · 2.5Η2θ, where Me is N a or K. The substance is readily soluble in water, on storage it is carbonised (its a thin solid carbonate or scar is formed on the surface), it clumps, has a pour weight of 1280-1320 kg / m 2, it is hygroscopic. The substance is very pure and its chemical composition remains constant,% by weight: Me 2 O: 25-38, Al 2 O 3: 37.5-44.5, SiO 2: not more than 0.1. Fe 2 O 3: not more than 0.02; moisture content 20-25. The molar ratio of Al metal methoxy di n and alumina Me 2 O 2: Al 2 O 3 is 1.1-1.4 in the product.

Compared to the prior art methods referred to above (4, 5, 6), the advantages of the method according to the invention are as follows: - energy consumption can be reduced by 5.5-8%; - the yield of the desired product is improved by 8.5-26%; process 1 the apparatus is one-fold in the crystallization and evaporation steps; - the aliquot component used in the extraction step is less consumed because it is regenerated from the mother liquor.

Some aluminum-containing raw materials such as Nefeli i ni and kai k-kikivi are ground to a size of 80 yum. A batch is prepared by mixing them with a mixture of CaO and SiO 2 oxides in the batch so that the molar ratio of CaO and SiO 2 oxides in the batch is 2.05 and the molar ratio Μβ2θ: (Al 2 O 3 + Fe 2 O 3) = 0.95. The obtained batch is sintered in a rotary kiln at a temperature of 1200 ° C. The obtained sintered cake is crushed and extracted with a solution having the following composition, g / l: Al 2 O 3: 14-30, Me 2 O: 35-35.5, SiO 2: 0.5-0.7, and the molar ratio Μβ2θ: Αΐ2θ3 = 1.63 -4.2. Extraction of a sinter containing alumina and alumina, this solution gives an aluminate solution in which the molar ratio of oxides Me 2 O: Al 2 O 3 is in the range 1.1-1.7.

The aluminate solution is separated from the resulting slurry and subjected to a silicate removal treatment to purify it of silica and other impurities. The removal of Si 1i is carried out so that the residual SiO2 content of the solution is 0.07 g / l. The white slurry formed in the silica treatment performed on the alumina solution is separated and fed to the batch preparation step. The resulting purified aluminate solution is evaporated. The evaporation process is carried out in two stages: in the first stage it is carried out at a temperature of 120 ° C to a Me 2 O content of 225-230 g / l, and in the second stage the evaporation is carried out at a temperature of 135-150 ° C in a Me 2 concentration of 360-370 g / l. 1. Carrying out the evaporation in two stages has been found to be advantageous, because it makes the evaporation more productive and efficient.

Evaporation gives an aluminate solution saturated with an aliquot of metal hydroaluminate. This impregnated aluminate solution is kept for 2-3 hours at a temperature in the range of 95-105 ° C to give a solution with an initial metal dipole content of 385-395 g. / 1. In this way, the solution is supersaturated with either suction or hydroaluminate, the solution thickens and becomes supernatural in composition, and the molar ratio of suction oxide to alumina is 2.05. The slurry prepared in this way is crystallized, which is carried out on a moving filter surface made of metal mesh fabric at a filter surface temperature of 50 ° C. The product rapidly crystallizes on the filter surface while separating from the mother liquor. This crystallization method shortens the crystallization time of the product and thus makes the recovery and separation of the product from the mother liquor more efficient.

The resulting mother liquor is recycled back to the sinter extraction step. This method reduces the amount of early reagent required in the sinter extraction step.

The advantage of this embodiment of the process for the preparation of Al metal hydroluminate will become more apparent from the following description. In the single-stage evaporation process, it is possible that the product precipitates and deposits on the walls of the evaporation equipment, whereby the thermotechnical properties of the evaporation process deteriorate. In the two-step embodiment of the evaporation process, in the first step, which is carried out at a temperature of 120 ° C, the concentration of the metal oxide in the solution is at least 225-230 g / l. Mego. This solution is still insoluble and the product remains in solution. In the second step, which is carried out at a temperature of 135-150 ° C, the concentration of aimetal oxy increases to 360-370 g / l Μβ2θ. When the evaporation temperature is raised to 135-150 ° C, the viscosity of the solution decreases and thus the solubility of the alkali metal hydroaluminate increases. Therefore, precipitation of the product into a solid phase is unlikely, i.e. the possibility of precipitation on the walls of the equipment is ruled out. In addition, it is preferred that the saturated viscous solution be maintained at 95-105 ° C for 2-3 hours until the concentration of metal oxide in the solution is 385-395 g / l Me 2 O.

Under these conditions, the product is observed to crystallize. This method has a favorable effect on the crystallization carried out on the mobile filter surface 1a in the temperature range of 10 to 95 ° C. This temperature is obtained on the surface by cooling it under running water.

In the above-mentioned embodiment of the method of manufacturing the product, not much heating medium, i.e. steam, is consumed in the evaporation step.

To illustrate the present invention, the following are some examples of various embodiments of a method of making a metal hydroaluminate.

Example 1 278.4 kg of nepheline ore containing the following constituents in the following amounts by weight: Me 2 O: 20.8, Al 2 O 3: 34.2, Fe 2 O 3: 1-3.5,

SiO 2 - 43, the remainder being impurities, and 490 kg of limestone having the following composition in weight: CaO: 54, S i 0 2: 2, the remainder being impurities, are ground to a particle size of 85 μm.

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Finely ground nepheline in an amount of 278.4 kg and crushed limestone in an amount of 490 kg are mixed with 330 kg of water. In the obtained charge, the molar ratios are as follows: CaO: SiO2 = 2.05 and Μβ2θ: (Al2 ^ 3 + ^ 6203) = 1.

The batch thus prepared is sintered in a rotary kiln at a temperature of 1200 ° C. The sintered cake is crushed and extracted with a solution containing g / 1: Me 2 O 3: 41203: 30 with a molar ratio Μβ2θ: Αΐ2θ3 of 1.93. The sludge resulting from the extraction is filtered to give a composition after filtration of g / l: Μβ2θ: 72.5, Al 203: 109, SiO2: 0.6 and a molar ratio Μβ2θ: Αΐ2θ3 = 1.1, the silicate is removed; the white slurry obtained is separated by thickening and filtration and then recycled back to the starting batch preparation step. The resulting aluminate-depleted aluminate solution having an amount of 1 m3 and the following composition, g / l: Μβ2θ: 72.5, Al2O3: 109, SiO2: 0.05, and a molar ratio of Me2O: Al2Ο3 = 1.1, is evaporated 120 At 0 ° C, the Me 2 O was concentrated to 350 g / l in a membrane evaporator.

An evaporated solution with a volume of 0.206 m3 is fed at a temperature of 120 ° C to a moving polyamide fiber filter cloth tensioned above a pour-type filter. The filter cloth is cooled to a temperature of 10 ° C by continuously feeding cold water at a temperature of 5 ° C to the non-working surface of the filter. The mobile filter surface is subjected to flash crystallization of the metal hydrolyaluminate and its separation from the mother liquor. The resulting mother liquor 1a has the following composition, g / l: Me 2 O: 35, Al 2 O 3: 30; molar ratio Me 2 O: Al 2 O 3 = 1.93; this solution with a volume of 1 m3 is recycled back to the sinter extraction stage.

The yield is 63 kg (68.5% of theory). The product has the following chemical composition, g / l: Me 2 O: 25, Al 2 O 3: 37.5, SiO 2: 0.05, Fe 2 O 3: 0.02; the remainder is bound H 2 O; molar ratio Me 2 O: Al 2 O 3 = 1.1; moisture content: 11 13 80437 25. The product is a loose white solid of commercial grade.

Example 2 280.3 kg of nepheline ore containing the following constituents in the following amounts,% by weight: MegO: 20.8, Al 2 O 3: 34.2, Fe 2 O 3: 3.5, S i 0 2: 43, and 521.7 kg of limestone which contains the main ingredients in the following amounts, by weight ί; CaO: 54, SiO 2: 2, ground to a particle size of 80 μm.

280.3 kg of finely ground Nefeliin and 521.7 kg of ground limestone are mixed with 335 kg of water. In the obtained charge, the molar ratios are as follows: CaO: SiO2 = 2.1,

Me 2 O: (Al 2 O 3 + Fe 2 O 3) = 1.1. The batch thus prepared is sintered in a rotary kiln at a temperature of 1250 ° C. The sintered cake is crushed and extracted with a solution containing, g / l: Me 2 O: 35, Al 2 O 3: 14, with a molar ratio of Me 2 O: Al 2 O 3 of 4.1.

The slurry obtained in the extraction is filtered, the filtrate containing, after filtration, g / l: :β2θ: 72.5, Al2O3: 70, SiO2 2: 0.1 and in which the molar ratio Me2O: Al2O3 = 1.7, silicate removal is carried out, the resulting white slurry is separated by thickening and filtration and recycled back to the 1 batch preparation step.

1 m3 of the silicate-free aluminate solution obtained, with a composition of g / l: Μβ2θ: 72.5, Al2O3: 70, S1O2: 0.05 and a molar ratio of Μβ2θ: Αΐ2θ3 = 1.7, is evaporated to 150 ° C. at a temperature of Me 2 O of 400 g / l in a well evaporator type 1 apparatus.

The evaporated solution in an amount of 0.182 m3 is fed from the evaporator to a moving polyamide nonwoven fabric which is tensioned in a pour-type filter. The filter cloth is cooled to a temperature of 95 ° C by continuously supplying cold water at a temperature of 30 ° C to its non-working surface.

The product crystallizes rapidly and separates from the mother liquor on a mobile filtration surface 14 80437. The mother liquor having a composition of g / l: Me 2 O 3: Al 2 O 3: 14 and a molar ratio of Me 2 O: Al 2 O 3 = 1.7 is recycled back to the extraction step. The yield is 56 kg (80%).

The chemical composition of the product obtained is as follows, g / l: Μβ2θ: 36.5, Al 2 ^ 3: 43, SiO 2 * 0.07, F 6203: 0.02, the remainder being water in bound form, molar ratio Μβ2θ: Αΐ2θ3 = 1.4 and moisture content 21. This commercial product is a cellular white solid.

Example 3 280.3 kg of nepheline ore containing the main constituents in the following amounts, weights: Me 2 O: 20.8, Al 2 O 3: 34.2, Fe 2 O 3: 1-3.5, SiO 2 · 43, and 490 kg of limestone containing, by weight: %: CaO: 54,

SiO 2: 2, ground to a particle size of 85 μm.

280.3 kg of finely ground nepheline and 490 kg of ground limestone are mixed with 330 kg of water. In the obtained charge, the molar ratios are as follows: Ca0: SiO2 = 2.05 and

Me 2 O: (Al 2 O 3 + Fe 2 O 3) = 1.05. The resulting batch is sintered in a rotary kiln at a temperature of 1200 ° C. The sintered cake is crushed and extracted with a solution containing, g / l: Me 2 O 3: Al 2 O 3: 21.5, and a molar ratio of Me 2 O: Al 2 O 3 = 1.63. The slurry obtained from the extraction is filtered and the aluminate solution obtained by filtration having the following composition, g / l: Me 2 O: 72.5, Al 2 O 3: 80, SiO 2 2 - 0.5, and a molar ratio of Me 2 O: Al 2 O 3 = 1.5, is subjected to silicate deletion. The white slurry formed in the silicate removal is separated by thickening and filtration and then recycled to the batch preparation step.

The silicate-depleted solution thus prepared in an amount of 1 n) 3f wherein the composition is as follows, g / l: Me £ 0: 72.5, A1 2 0 3: 80, S i 0 2 * 0, 05 and molar ratio

Me 2 O: Al 2 O 3 = 1.5, evaporated at 1 ° C to a Me 2 O content of 375 g / l in an evaporator type apparatus. The filter cloth is cooled to a temperature of 50 ° C by continuously feeding cold water at a temperature of 20 ° C to the non-working part of the filter tl 15 80437. Al sithium hydroaluminate crystallizes rapidly and separates from the mother liquor on a moving surface. The resulting mother liquor has the following composition, g / l: Me 2 O: 35, Al 2 O 3: 21.5, and a molar ratio of Me 2 O: Al 2 O 3 = 1.63; it is recycled back to the new stage. The yield is 58.5 kg (73% of theory). The chemical composition of the product is as follows,%: Me 2 O: 30.5, Al 2 ^ 3: 39, S i 0 2 ^ 0.06. ^ 203: 0.015, the remainder being bound H 2 O, the molar ratio Me 2 O: Al 2 O 3 = 1.3 and the moisture content 22.5. The product is of commercial quality and is a crystalline loose white solid and imetal 1 in hydroaluminate.

Example 4 280.3 kg of nepheline ore a containing the main constituents,% by weight:

Me 2 O: 20.8, Al 2 O 3: 34.2, Fe 2 O 3: 3.5, SiO 2 '43, and 521.7 kg of limestone containing the following constituents in the following amounts,% by weight: CaO: 54, SiO 2: 2 »ground to particle size 80 yum.

280.3 kg of ground nepheline and 521.7 kg of ground limestone are mixed with 335 kg of water. The resulting charge has the following molar ratios: CaO: SiO2 = 2.1 and Me2O: (Al2O3 + Fe2O3) = 1.1. The batch thus prepared is sintered in a rotary kiln at a temperature of 1250 ° C. The sinter is crushed and extracted with a solution containing, g / l: Me 2 O: 36.5, Al 2 O 3: 14.5 and with a molar ratio of Me 2 O: Al 2 O 3 = 4.2. The slurry obtained from the extraction is filtered. From the aluminate solution, which after filtration has the following concentrations, g / l: Me 2 O: 72.5, Al 2 O 3: 70, SiO 2: 0.1, with a molar ratio of Me 2 O: Al 2 O 3 of 1.7, the silicate is removed; the resulting white slurry is separated by thickening and filtration and recycled back to the 1 batch preparation step.

1 m3 of the silicate-free aluminate solution obtained, containing, g / l: Me2 O: 72.5, Al2 O3: 70, SiO2: 0.05, and in which the molar ratio Me2 O: Al2O3 = 1.7, is evaporated in two steps : in the first step at a temperature of 120 ° C to a Me 2 O content of 230 g / l and a SiO 2 content of 0.16 g / l in a film-type 80437 ink-type device. The evaporated solution from the first stage, with a volume of 0.315 m3, is passed to a second evaporation stage, which is carried out in a well-evaporator-type apparatus at a temperature of 135-150 ° C to a Me 2 O concentration of 370 g / l and a S i 0 2 "P concentration of 0.25 g / 1. The evaporated solution from the second stage, with a volume of 0.195 m3, is fed at a temperature of 135-150 ° C from the evaporator to a crystallizer equipped with a stirrer, where the solution is kept at 95-105 ° C for 2-3 hours until the concentration of carbon dioxide in the solution is 385-395 g / l; the solution then cools to 105 ° C by self-evaporation and is thus subsequently evaporated to a Me 2 O content of 390 g / l and a SiO 2 -P concentration of 0.26 g / l, while forming a slurry. The aluminate slurry obtained, with a volume of 0.185 m3 and containing, g / l Me 2 O: 360, Al 2 O 3: 290 and having a molar ratio Μβ2θ, Αΐ2θ3 = 2.05 and a temperature of 105 ° C, is fed to a mobile metal mesh filtration surface which is attached to the drum filter palette. The metal filtration screen is cooled to 95 ° C by feeding cold water to the non-working pallet of the filter. The crystallization of the product, its separation from the mother liquor and the recycling of the mother liquor back to the extraction step are carried out in the same manner as in Examples 1-3 above.

The yield is 60 kg (86%). The product obtained has the following chemical composition,% by weight: Me 2 O · 38, Al 2 O 3: 44.5, SiO 2 ^ 0.06, Fe 2 O 3: 0.01, the rest being bound water, molar ratio Μβ2θ: Αΐ2θ3 = 1.4 and moisture content 20 The product is a white loose solid of commercial quality.

The process according to the invention can be applied in practice to the treatment of aluminum-containing ores, such as nepheline, bauxite, as well as aluminum-containing wastes from the chemical and metallurgical industries and other industries, as alumina, soda ash and potash.

In the production of alumina, a significant proportion of the starting material

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Π The aluminate solution obtained from the extraction step of 80437 (sinter) is used for the preparation of the alumina hydroaluminate. This product continues to be used to an increasing extent in the papermaking industry, oil drilling, mining, weaving industry and hydraulic machine construction technology.

Claims (5)

A process for the preparation of alkali metal hydroaluminate, which process comprises the following steps: - leaching of an alumina and alkali metal oxide-containing starting material, whereby an aluminate solution is obtained; removing the silicate from the aluminate solution; evaporation of the aluminate solution from which the silicate was removed; crystallization of the alkali metal hydroaluminate from the evaporated aluminate solution, characterized by - evaporating an aluminate solution whose molar ratio of alkali metal oxide MeaO to alumina AlaO3 is between 1.1 and 1.7 and the evaporation is carried out at a temperature of 120-150 ° C the alkali metal oxide is 350-400 g / l; the crystallization of the alkali metal hydroaluminate is carried out by adding the evaporated solution at a temperature of 95-150 ° C to a moving filter surface with a temperature of 10-95 ° C, after which the product crystals obtained are separated from the mother solution; - the poured parent solution is fed to the leaching step of the starting material. Process according to claim 1, characterized in that said preparation of the aluminate solution is carried out in two steps: the first step is carried out at a temperature of 120 ° C until the concentration of the alkali metal oxide is 225-230 g / l, the second step is carried out at a temperature of 135-150 ° C until the concentration of said oxide is 360-370 g / l. 20 80437 Process according to Claim 1 or 2, characterized in that after the evaporation the aluminate solution is allowed to stand for 2-3 hours at a temperature of 95-105 ° C until the concentration of the alkali metal oxide in the solution becomes 385-395 g / l. Process according to any one of claims 1-3, characterized in that said crystallization is carried out at a filter surface temperature of between 20 and 50 ° C. 5. A method according to any one of claims 1-4, characterized in that the filter surface is a polyamide fiber fabric or a woven metal mesh. TL