DK155431B - Process for converting aluminium silicate-containing raw materials into aluminium oxide, soda products and cement - Google Patents

Description

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The invention relates to a process for processing aluminum silicate-containing raw materials for alumina, soda products and cement.

Alumina is mainly used for the manufacture of aluminum as well as for abrasives, refractory materials and the like.

Soda products are used in the chemical and food industries as well as in the manufacture of building materials, such as glass, and in many other industries.

10 Cement is widely used in building, in metallurgy, in the manufacture of refractory materials, such as refractory concrete, and in many other industries.

The known process for working up aluminum silicate-containing raw materials such as bauxite and neophelines is as follows. First, a charge is made from an aluminum-containing feedstock, soda and calcium carbonate. The resulting charge is sintered at a temperature in the range of 1,100 to 1,350 ° C, and the sinter cake thus produced is omitted. This creates an alumina solution and belit mud that is separated from the aluminate solution and processed into Portland cement. The aluminate solution is subjected to a two-step silicate removal treatment. In the first step, the solution is subjected to hydrothermal treatment in leach containers at a temperature of 130 - 175 ° C, followed by separation of the resulting solid phase as sodium hydroaluminum silicates from the aluminate solution. Partial silicate removal from the aluminate solution occurs in this first step. For a more complete silicate removal, the aluminate solution in the second step is treated with lime milk to produce calcium hydroaluminum silicates of the composition: 3CaO.Al2C> 3 * xSiC> 2 · (6-2x) -20 where x is between , 01 and 0.5. The purified aluminate solution is then separated from the solid phase. The 35 solid phase obtained by the second step of silicate removal is treated with soda for further extraction of alumina, while the resulting solid mixture - mud - is returned to make charge. This mud

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2, however, is very finely divided and therefore complicates the production and correction of the charge, causes dust formation and increases the amount of dust leaving the furnace, which is undesirable. As a result, the composition of the charge 5 becomes uneven in the longitudinal direction of the furnace during sintering, resulting in a diminished recovery rate of valuable components from the charge. The resulting aluminate solution is carbonized by passing carbon dioxide through the solution, and aluminum hydroxide is then separated, which is then calcined at a temperature in the range of 1,200 to 1,500 ° C to produce alumina.

After recovering aluminum hydroxide from the solution, it is repeatedly evaporated. After the second evaporation, soda is obtained, while after the fourth evaporation, potassium carbonate is obtained (cf. Lainer A.I. et al. "Production of Alumina", publisher "Metallurgia", Moscow, 1978).

A disadvantage of this process is that in silicate removal it is not possible to achieve a sufficiently effective removal of silicate from aluminate solutions, which is why high quality alumina cannot be produced due to the presence of SiCl3 and Fe2Og.

The smaller the content of these components, the better quality alumina is obtained. The content of silica and ferric oxide in the alumina produced by the known method ranges from 0.05 to 0.03 and from 0.06 to 0.08 respectively.

Attempts have been made to improve silicate removal by introducing magnesia into the aluminate solutions (cf. DE patent 752,739). Although this process results in extensive purification of an alumina solution for silica, the resulting white mud is a waste product that cannot be used to recover an additional amount of alumina. For this reason, the known method is not sufficiently effective from an economic point of view.

A method of working up alumina raw materials for alumina by sintering is known, in which solutions obtained after leaching of the sintering 3

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third mass, is freed from silicon compounds by the addition of lime (cf. US Patent 2,604,379). The resulting hydroaluminum silicate mud is returned to sintering. This results in a more complicated process for preparing and sintering the batch as the milling of the batch is disturbed, homogenization of the batch in the correction vessels is prevented and entrainment of dust in the exhaust gases from the furnaces is increased.

It is an object of the invention to provide a process for working up aluminum silicate raw materials, thereby providing an improved silicate removal step for aluminate solutions enabling a thorough purification thereof for silica and iron oxides while forming calcium hydroaluminum silicate application, as in the manufacture of a cement for the manufacture of foundry molds and cores, as well as cement with high alumina content.

The object is achieved by a process for processing aluminum silicate raw materials for alumina, soda ash and cement, comprising: 1) preparing a charge from aluminum silicate raw materials, soda and calcium carbonate, 2) sintering the resulting charge at a temperature between 3,100 and 1,350 ° C; 3) leaching of the sinter mass thus formed to form an aluminate solution and belit mud; 4) separating the aluminate solution from belit mud worked up to Portland cement; C, followed by introduction of a lime component into the clarified solution, 6) separation of calcium hydroaluminum silicate from the silica-free solution, 7) carbonization of the purified aluminate solution and recovery of aluminum hydroxide, followed by calcination to produce aluminum dioxide,

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8) extracting soda and potassium carbonate from the carbonate solution, characterized in that the silicate removal from the aluminate solution is effected by treating it with a mass containing the oxides CaO, Al2 O3, SiO2, Fe2 ^ 3f Na2 ° ratio of the oxides corresponding to CaO: (SiO 2 + Fe 2 ° 3) = 1,000-5,000: 1 and Na 2 O: Al 2 O 3 = 0.25-0.6: 1, where CaO is active and Na 2 O is carbonized, which mass is used in a such an amount that an active CaO content of the solution is obtained from 5 to 10 g / l. Thereby, a comprehensive purification of the aluminate solution for silica and iron oxides takes place, which impurities in the resulting calcium hydroaluminum silicate of the formula: 3CaO · (Al, Fe) 203 * xSiO2 (6-2x) H2 O, where x is 0.01 to 0.5 , which is worked up into cement for the production of molds and cores and for a refractory cement with high alumina content.

In the process of the invention, the reprocessing of calcium hydroaluminum silicate for cementing molds and cores is carried out by leaching of alkalis therefrom, followed by a heat treatment at a temperature in the range of 250 to 600 ° C for a time sufficient to form a product. containing (wt.%): CaO - 50-60, Al2 O3 + - 2-35, 25 SiO2 - 0.1-5, H2 O - 3-12, CO2 - 0.5-25, Na2 O - 0.1 - 0.0, K20 - 0.1-0.5, Fe2Q3 - 0.1-1.0, MgO - 0.1-5.

After the heat treatment, the product is subjected to a fine paint. The milling takes place until a fraction having a particle size below 80 µm is formed in an amount of 30 from 85 to 99 wt., And a fraction having a particle size of 80 to 200 µια in an amount from 1 to 15 wt.%.

In the process of the invention, the processing of calcium hydroaluminum silicate into a high alumina cement cement is mixed by mixing it with 35 aluminum hydroxide in a weight ratio of 0.25 - 0.50: 1 as calculated for CaO and Al2 O3, sintering the resulting binder.

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5 at a temperature ranging from 1,350 to 1,450 ° C and finely grind the sinter mass. The milling is carried out to obtain a cement fraction having a particle size less than 80 μια in an amount of from 85 to 99% by weight and a fraction having a particle size of 80 - 200 μιη in an amount of from 1 to 15% by weight.

The invention is further illustrated in the following with reference to the drawing, which shows a principle sketch for working up aluminum silicate-containing raw materials for alumina, soda products and cement.

A rock, e.g. Bauxite, nephelin, from a silo 1 is comminuted in a mill 2. From a silo 3, limestone is fed to the mill 2 while soda is supplied from a silo 4. The components are adjusted so that a molar ratio of the oxides in the charge is assured. follows:

Na90 + K90 ------ = 0.95-1.05, CaO / SiO4 = 1.95 - 2.05.

Alo0, + Feo0, 20 2 3 2 3

The resulting charge is sintered in a rotary kiln 5 at a temperature ranging from 1,100 to 1,350 ° C. The sintered mass is passed to a crushing unit 6 where it is comminuted and then passed to a mill which also receives a recycled alkali-aluminate solution. In mill 7, aluminate and sodium ferrite are vented to obtain an aluminate solution and belit mud.

From the mill 7, the belite mud and aluminate solution are passed to precipitators 8 wherein the aluminate solution is separated from the solid phase. The resulting solid phase - belit mud - is washed with water on filters 9, and the mud from which aluminates and alkalis are washed is used to make Portland cement, while the wash water is returned to the mill 7 for leaching.

The belit mud is comminuted with limestone in a mill 10 and the resulting crude mixture is sintered in a rotary kiln 11 at a temperature between 1,400 and 1,450 ° C. The resulting Portland cement clinker is ground in a mill 12 6 ϋΚ 1 h5 4 6 1 Β together with plaster applied from a silo 13 to produce Portland cement.

The aluminate solution from precipitator 8 is passed to a container 14 where at a temperature of 130 to 175 ° C, the silica solution (step one) is purified, which passes into a solid phase containing insoluble aluminum silicates such as Na 2 O 2 Al 2 O 2 nSiO 2 * mH 2 O where n = 2 -6 and m = 0.1 - 4. As a result of the treatment of the aluminate solution in the container 14, the content of silica is reduced from 2-3 g / l to 0.1-0.3 g / l. while the iron oxide content is reduced from 1-2 g / l to 0.15-0.2 g / l, which is insufficient to obtain the best quality alumina. For this reason, another purification step is performed. From the container 14, the aluminate solution is passed for separation in a thickener 15 and then on a filter 16, where the solid phase is separated from the aluminate solution. The solid product obtained is delivered to prepare the charge in the mill 2, while the aluminate solution is fed to a stirred 20 container 17, where a more extensive purification is performed.

For this purpose, a mass is fed from a vessel 18 to the stirred vessel 17 containing the oxides CaO, Al2O2, SiO2, Fe2 ° 3 'Na2O, the weight ratio of the oxides being equal to: CaO: (SiO2 + Fe2O2) = 1,000-5,000 25: 1 and Na 2 O: Al 2 O 2 = 0.25-0.60: 1 where CaO is active and Na 2 O is carbonized. The pulp is used in an amount which ensures an active CaO content in the solution in the range of 5 to 10 g / l.

The silicate removal from aluminate solutions is effected by the process of the invention, i. using said mass as the lime component, to a greater extent. This is because the oxides in the pulp are present in a chemically combined state such as calcium hydrocarbon aluminate and calcium hydroaluminate. These 35 compounds react more actively with silicon and ferric dioxide to form calcium hydroaluminum silicate of the type: 3CaO * (Al, Fe) 202 * xSiO2 · (6-2x) H2 O, wherein x represents 0.01-0.5. As a result of using the mass with this 7

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composition, the content of calcium hydroaluminum silicate in the solid phase is substantially increased, reaching 95% by weight, while the known methods based on the use of lime milk do not cause the content of calcium hydroaluminum silicate in the solid phase to exceed 30% by weight.

Due to the use of this second-stage silicate removal technique, the content of silicate in the aluminum solution is reduced from 0.1 - 0.3 g / l to 0.02 g / l, while the content of iron oxides is reduced from 0.15 - 0, 20 to 0.01 g / l. This enables the production of high quality alumina.

From the stirred vessel 17, the suspension is passed to a thickener 19 and a filter 20 where the purified 15 aluminate solution is separated from the solid phase consisting of calcium hydroaluminum silicate as well as lime, calcium carbonate and magnesium carbonate.

Then, the pure aluminate solution is subjected to carbonization and thickening in a container 21 under the presence of carbon dioxide.

As a result of the carbonization and thickening of the solution, aluminum hydroxide is precipitated therefrom, which is recovered in hydrocyclones 22. The resulting aluminum hydroxide is washed on filters 23 and then calcined in a rotary kiln 24 at a temperature of 1,200 to 1,250 ° C to obtain the final product. namely alumina.

After extraction of aluminum hydroxide, the carbonate-containing mother liquor is extracted from the hydrocyclone 22 and fed to an apparatus 25 where soda and potassium carbonate 30 are obtained by repeated evaporation.

The solid phase containing calcium hydroaluminum silicate and impurities obtained by the second stage of silicate removal and separated on filter 20 is used to make cement of two types: 35 1) Cement for making molds and cores for making articles by casting, 2) a refractory cement with a high alumina content for making refractory castings and articles 8

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the.

For the manufacture of cement to produce foundry cores and molds, calcium hydroaluminum silicate is subjected to a heat treatment at a temperature of 250 to 600 ° C in a rotary kiln 26, followed by milling in a mill 27. The resulting cement contains as weight%: CaO - 56-60, MgO - 0.1-5, Al2 ° 3 "12" 35 'SiO2 - 0.1-5, H2 O - 3-12, CO2 - 0.5-25, Na2 O - 0.1-1, 0, K20 - 0.1-0.5, Fe2 ° 3 "0.1-1.0 and has a fineness after grinding characterized by a content of the fraction having a particle size below 80 μπι of 85 to 99% by weight, and a fraction having a particle size of 200 to 80 μπι in an amount of from 1 to 15% by weight.

In order to obtain better properties, especially adjustable solidification time for the cement, during the grinding phase it is possible to introduce gypsum, in the form of the dihydrate into the cement in an amount of 1 to 30% by weight, and a surfactant in an amount of 0.5 to 25% by weight.

To produce a high alumina cement, the solid phase from filter 20 is passed to a stirring vessel 28, where it is mixed with aluminum hydroxide from filter 23 in a weight ratio of 0.25-0.50: 1 as calculated for CaOrAl , Followed by sintering in a rotary kiln 29 at a temperature between 1,350 and 1,450 C with subsequent grinding in a mill 30 to a content of the fraction having a particle size less than 80 µm from 85 to 99 weight % and a content of the fraction having a particle size of from 200 to 80 μια, from 1 to 15% by weight

The process of the invention for producing alumina, sodium carbonate and cement from aluminum silicate-containing feedstock is further illustrated in the following, using specific examples and with reference to the drawings.

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Example 1

As a starting material, a nepheline concentrate, limestone and water are used.

5 All the steps of the method are performed in accordance with the drawing. The second step of silicate removal from the aluminate solution is carried out in the stirring vessel 17 with the addition of the lime component in the form of a pulp.

The mass is prepared by mixing lime milk with the aluminate solution in such a ratio that the ratio of CaO (active): (SiO2 + Fe2O3) falls within the range of 1,000 to 5,000 and the ratio of Na2O (carbonized) to Al2O3 falls within the range of 0.25 to 0.60. Such a mass contains oxides of CaO, SiO2, Fe2 O3 and Na2 O which form such compounds as calcium hydrocarboaluminates and hydroaluminates. These compounds, upon reaction with silicate and iron oxides in the aluminate solution, readily form calcium hydroaluminum silicate of the formula 3 CaO (Al, Fe) 203-xSiO 2 * (6-2x) H2 O where x is between 0.01 and 0.5, the content thereof in the solid phase can be as large as 95% by weight. Thus, a thorough purification of the alumina top solution for silicon and iron compounds is ensured. When using lime milk for silicate removal from aluminate solutions according to the known method, the above-mentioned calcium hydroaluminium is formed to a lesser extent (up to 30% by weight), resulting in an insufficient purification of the solution for silicate and iron oxides.

The aluminate solution, which has passed the filter 16, contains 77 g / l alumina, 0.1 g / l silica and 0.15 g / l ferric oxide. The lime mass is added in an amount which ensures an active CaO content of 5-10 g / l in the aluminate solution, ie. 0.1-0.3 m 2 of the prepared 3 mass is added per day. m of the aluminate solution. The resulting suspension is kept in the stirrer 17 for 1-4 hours at a temperature of 70-95 ° C.

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The basic parameters and results of the silicate removal process are shown in Table 1, where similar data is provided for comparison to illustrate the known silicate removal process / based on the use of lime-5 milk (embodiment 4).

Table 1

No. Embodiments of Active Ratios of Oxides in Calcium of Example 1 CaO in Aluminum 10 Night Solution CaO. . Γ Γ gene, g / 1 _ ^ _SiQ2 + Fe2Q3_Μ2 ° 3_ 1 2 3 4 5 2 1 10.0 1,000 0.25 15 3 2 7.5 2.500 0.40 4 3 5.0 5.000 0.60 5 4 10 , 0 28 0.20 20 Silicate removal parameters Content of alumina in the second stage solution after the second silicate removal step, g / l

Temperature, ° C Time, hours S1O2 Fe2 ° 3 25 Λ_Z_5_9 70 1 0.02 0.010 80 2 0.015 0.090 95 4 0.010 0.008 80 2 0.05 0.06 30 _

Example 2

This example illustrates the manufacture of cement for foundry molds and cores.

A solid phase containing mainly calcium hydroaluminum silicate is passed, after filter 20, to the rotary furnace 26, where it is subjected to a heat treatment to a temperature in the range of 400 to 450 ° C for 2 - 2.5 hours.

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hours and then headed to the mill 27, where a fine grind is made to obtain a fraction having a particle size less than 80 μιη in an amount of 85 wt% and a fraction having a particle size of from 200 to 80 5 µm in an amount of 15 weight%. The resulting cement has the following composition, expressed in% by weight: CaO - 51.6, 21.3, S1O2, 5, H2O - 9.7, the remainder being the impurities Na2O, K2O, MgO, Fe2O3, CO2. Salty cement is wetted with an aqueous solution of 10 sulfite-alcohol liquor to obtain a paste of normal thickness, and cube test bodies thereof are prepared for mechanical testing of the strength properties. Samples are stored in air and tested after 1 and 3 days.

15 The basic test results are as follows:

Binding time: begins after 5 minutes ends after 10 minutes Compression strength MPa: 20 After 1 day 13.0 after 3 days 15.0.

Listed below are results of testing the cement thus prepared, which is intended to be used in the manufacture of cast sand mixtures.

For this purpose, the cement is mixed with a refractory filler and a surfactant. From the resulting mixture, samples are prepared using a fall hammer machine. For these tests, the following properties are obtained s 1) Compressive strength, MPa after 1.5 hours 0.4 - 0.6 after 3 hours 0.6 - 1.0 after 24 hours 1.8 2.0 2) The application time is adjusted between 1 and 60 min.

3) Residual strength after calcination, MPa, at tempe rature

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12 600 ° CO - 30 900 ° CO - 0.15 1.100 ° C 0.1 - 0.40 1.250 ° C 1.5 - 4.5 5 4) Fragility after 24 hours curing,%: 0.05 - 0, 20 5) Gas permeability 150 - 180 units 6) Toxic substances developed during the manufacture and filling of the molds: None.

10 The data from the cement test show that the cement can be successfully used for the manufacture of molds and cores in the manufacture of castings from ferrous metals and non-ferrous metals in single use molds.

Example 3

This example illustrates the preparation of a high alumina cement.

A solid phase containing mainly calcium hydroaluminum silicate from filter 20 is fed to the 20 stirred vessel 28, in which it is mixed with aluminum hydroxide, fed from filter 23 at a weight ratio of 0.25 - 0.50: 1 calculated for CaOcA Then, the resulting starting mixture is sintered in a furnace 29 at a temperature of 1,400 ° C. The sintered mass is ground in the mill 30 to obtain a fraction having a particle size below 80 µπι in an amount of 90 wt% and a fraction having a particle size of 200 to 80 µιη in an amount of 10 wt%. These cements are mixed with water to give a paste of the usual consistency which is kept in the air at a temperature of 20 ° C. The results of examination of these samples for compressive strength and heat resistance as well as the compositions of the raw mixture are shown in Table 2.

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Table 2

Composition Binding time, Final pressure Fireproof

5 wt [__% hours minutes strength, MPa ° C

Hydro- Alumini- Begin- Finish- 3 days 7 days Aluminum hy- a1 -creation Umilicate Droxide AL2U3 10 53.8 46.2 0.25 0-30 1- 0 52 63 1,630 45.0 55.0 0 , 37 0-45 1-15 41.5 54.5 1.680 32.3 67.7 0.50 2-00 4-20 31.5 40.5 1.710

The results of the studies on the cement with 15 high alumina content show that it can be used with good results for the preparation of refractory concrete and other refractory coatings.

The results show that it is possible in the process according to the invention to produce high quality aluminum oxide and special purpose cements, thereby enabling a more efficient total work-up of aluminum silicate-containing raw materials for aluminum oxide, sodium products and cement.

Claims (4)

A process for processing aluminum-silicate-containing raw materials for alumina, soda ash and cement, wherein: 1. preparing a charge from an aluminum silicate-containing feedstock, soda and calcium carbonate, 2. sintering the resulting charge at a temperature between 1.100 and 1.350 ° C, 10 3) exclude the thus-sintered mass to obtain an aluminate solution and belit mud, 4. separates the aluminate solution from belit mud worked into Portland cement, 5. removes silicate from the aluminate solution at a temperature of 130 - 175 ° C, followed by introduction of a lime component into the clear solution, 6. separation of calcium hydroaluminum silicate from the solution with reduced silicate content, 7. carbonization of the purified aluminate solution and recovery of aluminum hydroxide followed by calcination to alumina, 8. recovery of soda and potassium carbonate from the carbonate solution, characterized in that the silicate removal from the aluminate solutions in step 5) by treating them with a mass containing oxides CaO, A2O2, SiC2 / Fe2Og, Na2O, wherein the weight ratio of the oxides corresponds to CaO: (SiO2 + Fe2O2) = 1,000-5,000: 1 and Na2O: Al₂O₂ = 0.25 - 0.60: 1 wherein CaO is active, Na₂O is carbonized, the mass of which is used in an amount which ensures content of active CaO in the solution in the range of 5 to 10 g / l . Process according to claim 1, characterized in that the resulting calcium hydroaluminum silicate is worked up into cement intended to produce 35 cores and molds for foundry use by heat treatment thereof to a temperature between 250 and 600 ° C for a period of time sufficient to form a product which, in% by weight, contains: CaO - 50-60, MgO - 0.1-5, A₂O₂ DK DK 155431 B <s 12-35, SiO₂ - 0.1-5, K₂O - 0, 1-0.5, Na 2 O - 0.1 - 1.0, Fe 2 O 3 - 0.1 - 1.0, CO 2 - 0.5 - 25, H 2 O - 3 - 12, followed by fine grinding. 3. A process according to claim 2, characterized in that the cement grinding is carried out with the addition of gypsum as dihydrate or a surfactant. Process according to claim 1, characterized in that the resulting calcium hydrogen aluminum silicate is worked into a cement with a high aluminum content by mixing with aluminum hydroxide in a weight ratio of 0.25 - 0.50: 1, calculated for CaO: Al2 O3, sintering the obtained mixture to a temperature between 1,350 and 1,450 ° C and subsequent fine milling of the resulting sintered mass.