A kind of easily soluble aluminum oxide and preparation method thereof

Abstract

The invention discloses a soluble aluminum oxide and a preparation method thereof, and relates to the technical field of aluminum oxide production. In the invention, aluminum hydroxide and a low-concentration sodium aluminate solution are used as raw materials, and a high-temperature and high-pressure chemical reaction is carried out. After the reaction product is separated and washed, the aluminum oxide hydrate is obtained, and the obtained aluminum oxide hydrate is subjected to low-temperature roasting to obtain a soluble aluminum oxide product. The preparation method provided by the invention is simple and easy to implement, and can not only optimize the particle size and crystal structure of the aluminum oxide product, but also improve the surface activity, dispersibility, flowability and solubility of the aluminum oxide.

Description

Technical Field

[0001] The present application relates to the technical field of alumina production, and in particular to a readily soluble alumina and a preparation method thereof. Background Art

[0002] Alumina and electrolytic aluminum are two key production processes in the aluminum smelting industry. Alumina with poor solubility will dissolve slowly and easily precipitate after being added to the electrolyte melt, which will make the aluminum electrolytic cell unstable or cause anode effect, thereby reducing current efficiency, increasing power consumption, material consumption, and increasing PFCs greenhouse gas emissions, which not only affects the production of aluminum electrolysis but also pollutes the environment.

[0003] The dissolution rate of alumina is an important evaluation index of dissolution performance, which is mainly related to the particle size of alumina, α-Al 2 O 3 The physical properties of aluminum oxide are related to the content, microstructure and other physical properties, as well as the wetting of aluminum oxide during aluminum electrolysis. In the electrolytic cell, aluminum oxide first spreads on the surface of the electrolyte and is in a floating state in the early stage. When aluminum oxide with better physical properties comes into contact with the molten electrolyte, a solidified thin shell appears on the bottom, while the upper part is in a dry state. The aluminum oxide stays on the surface of the electrolyte melt and is wetted by the electrolyte extending from bottom to top, which is beneficial to increase the dissolution rate. Alumina with poor physical properties sinks directly to the bottom of the tank and mixes with the aluminum water, resulting in a significant reduction in its dissolution rate, causing problems such as instability of the electrolytic cell and reduced current efficiency. There is currently no report in the prior art explaining how to prepare aluminum oxide with better physical properties. Summary of the invention

[0004] The present application provides a readily soluble alumina and a preparation method thereof, in order to solve the technical problems that the existing alumina products have a low dissolution rate during the electrolysis process, resulting in instability of the electrolytic cell, reduced current efficiency, and the like.

[0005] In a first aspect, the present application provides a method for preparing readily soluble alumina, comprising the following steps:

[0006] mixing aluminum hydroxide and sodium aluminate solution to form aluminum hydroxide slurry;

[0007] subjecting the aluminum hydroxide slurry to a high temperature reaction to obtain aluminum oxide hydrate;

[0008] The alumina hydrate is calcined at low temperature to obtain easily soluble alumina.

[0009] Optionally, the caustic soda concentration of the sodium aluminate solution is Na 2 O K is 5 g / L to 10 g / L, and the molecular ratio of sodium oxide to aluminum oxide in the sodium aluminate solution is α KIt is 1.35~1.60.

[0010] Optionally, relative to 1 L of the aluminum hydroxide slurry, the solid content of the aluminum hydroxide slurry is 100 g to 600 g.

[0011] Optionally, the high temperature reaction includes the following reaction parameters: the reaction temperature is 190°C to 240°C.

[0012] Optionally, the high temperature reaction also includes the following reaction parameters: the reaction time is 10 min to 60 min.

[0013] Optionally, subjecting the aluminum hydroxide slurry to a high temperature reaction to obtain aluminum oxide hydrate specifically comprises:

[0014] subjecting the aluminum hydroxide slurry to a high temperature reaction to obtain a reaction product;

[0015] The reaction product is separated and washed to obtain aluminum oxide hydrate.

[0016] Optionally, the temperature of the low-temperature calcination is 550°C to 750°C.

[0017] In a second aspect, the present invention provides a readily soluble alumina prepared by the preparation method described in the first aspect.

[0018] Optionally, the microstructure of the easily soluble alumina is a spherical structure whose surface is covered with a large number of flakes.

[0019] Optionally, the easily soluble alumina includes at least one of the following properties: a repose angle of 25 to 28 degrees, no α-Al 2 O 3 , specific surface area is 60~100m 2 / g, bulk density is 0.5~0.8g / cm 3 .

[0020] The above technical solution provided by the present invention has the following advantages compared with the prior art:

[0021] The present invention provides a readily soluble alumina and a preparation method thereof. In the present invention, aluminum hydroxide and sodium aluminate are used as raw materials to prepare aluminum hydroxide slurry. After high-temperature reaction, aluminum hydroxide is dissolved and transformed in water, and new crystal nuclei are formed. At this time, the structure of aluminum hydroxide begins to change; at the same time, aluminate ions in the sodium aluminate solution undergo a decomposition reaction, and the generated alumina hydrate is induced to precipitate on the newly generated crystal nuclei, promoting the agglomeration and growth of the new crystal nuclei, making the particle size coarsened, and obtaining an alumina hydrate with a special structure; the alumina hydrate is calcined at a low temperature to obtain readily soluble alumina. The preparation method provided in the present invention is simple and easy to implement, and can not only optimize the particle size and crystal structure of the alumina product, but also improve the surface activity, dispersibility, flowability and solubility of the alumina. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0023] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0024] Figure 1 A flow chart of a method for preparing soluble alumina provided in this application;

[0025] Figure 2 A flow chart of a method for preparing a readily soluble alumina provided in Example 1 of the present application;

[0026] Figure 3 This is an electron microscope scanning image of the easily soluble alumina provided in Example 1 of the present application. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0028] Various embodiments of the present application may be presented in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity, and should not be understood as a rigid limitation on the scope of the present application; therefore, the range description should be considered to have specifically disclosed all possible sub-ranges and single numerical values ​​within the range. For example, the range description from 1 to 6 should be considered to have specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the range, such as 1, 2, 3, 4, 5 and 6, which apply regardless of the range. In addition, whenever a numerical range is indicated herein, it is meant to include any cited number (fractional or integer) within the indicated range.

[0029] In the present application, in the absence of any contrary description, the terms including "including" and the like mean "including but not limited to". In this article, relational terms such as "first" and "second" and the like are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is any such actual relationship or order between these entities or operations. In this article, "at least one" means one or more, and "multiple" means two or more. "At least one", "the following at least one" or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can all represent: a, b, c, ab (i.e., a and b), ac, bc, or abc, wherein a, b, c can be single or multiple, respectively.

[0030] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0031] In the first aspect, the present application provides a method for preparing soluble alumina, such as Figure 1 As shown, the following steps are included:

[0032] mixing aluminum hydroxide and sodium aluminate solution to form aluminum hydroxide slurry;

[0033] subjecting the aluminum hydroxide slurry to a high temperature reaction to obtain aluminum oxide hydrate;

[0034] The alumina hydrate is calcined at low temperature to obtain easily soluble alumina.

[0035] In the above embodiment, aluminum hydroxide and sodium aluminate solution are used as raw materials, and the easily soluble aluminum oxide obtained after a simple high-temperature reaction and low-temperature calcination has a faster dissolution rate due to the change in its structure.

[0036] As an optional embodiment, the aluminum hydroxide source is aluminum hydroxide obtained by industrial decomposition, and the aluminum hydroxide product is obtained after separation and washing with a flat disc filter.

[0037] As an optional embodiment, the mixing of aluminum hydroxide and sodium aluminate solution to form aluminum hydroxide slurry specifically includes: the aluminum hydroxide product obtained after separation and washing by a flat disc filter is mixed with the sodium aluminate solution in a mixing tank to form aluminum hydroxide slurry, and is transported to the reactor by a slurry pump.

[0038] As an optional embodiment, the caustic soda concentration Na of the sodium aluminate solution is 2 O K is 5g / L to 10g / L, and the molecular ratio of sodium oxide to aluminum oxide in the sodium aluminate solution is α K It is 1.35~1.60.

[0039] In the above embodiment, the sodium aluminate solution is limited to a low-concentration sodium aluminate solution by limiting the concentration of caustic soda and the molecular ratio of sodium oxide to aluminum oxide in the sodium aluminate solution.

[0040] Since the main component of sodium aluminate solution is Na 2 O-Al 2 O 3 -H 2 O. The purpose of using a low-concentration sodium aluminate solution is that during the high-temperature chemical reaction, aluminum hydroxide is first dissolved and transformed in water, and new crystal nuclei are formed, and the structure of aluminum hydroxide changes; at the same time, the aluminate ions in the sodium aluminate solution undergo a decomposition reaction, and the generated aluminum hydroxide induces precipitation on the newly generated crystal nuclei, promoting the agglomeration and growth of the new crystal nuclei, and making its particle size coarsened; since the caustic soda in the sodium aluminate will enter the aluminum hydroxide lattice during the entire lattice transformation process, the low-concentration sodium aluminate solution can ensure that the content of sodium oxide impurities in the product does not increase. If the concentration of the sodium aluminate solution is too high, the content of sodium oxide impurities in the product will exceed the standard, but if the low-concentration sodium aluminate solution is not used and the aluminum hydroxide slurry is directly prepared with water, the above reaction process will not occur, so that the dissolution performance and other indicators of the final alumina product will not be optimized.

[0041] In the above embodiment, the low concentration sodium aluminate solution can also be obtained by diluting the sodium aluminate semen, and specifically, the sodium aluminate semen can be diluted 15 to 30 times with hot water.

[0042] As an optional embodiment, the solid content of the aluminum hydroxide slurry is 100 g / L to 600 g / L, that is, relative to 1 L of the aluminum hydroxide slurry, the solid content of the aluminum hydroxide slurry is 100 g to 600 g.

[0043] In the above embodiment, limiting the solid content in the aluminum hydroxide slurry helps determine the amount of aluminum hydroxide in the slurry and ensure the product content in the later reaction and roasting process. At the same time, limiting the solid amount of aluminum hydroxide also ensures the product structure after the reaction and ensures the solubility of the product.

[0044] In the above embodiment, the solid content in the aluminum hydroxide slurry is not specifically limited. For example, the solid content in the aluminum hydroxide slurry may be 100 g / L, 200 g / L, 300 g / L, 400 g / L, 500 g / L or 600 g / L.

[0045] As an optional embodiment, during the high temperature reaction process, the reaction temperature is 190°C to 240°C.

[0046] In the above embodiment, the reason for limiting the reaction temperature is that, at this reaction temperature, the sodium aluminate ions in the solution have a higher reaction kinetic energy, and they are more likely to break through the solvation membrane after collision, releasing lattice energy, and then, within a certain period of time, the surface and internal structure of aluminum hydroxide can be changed to form aluminum oxide hydrate with good crystallization properties.

[0047] As an optional implementation manner, during the high temperature reaction process, the reaction time is 10 to 60 minutes.

[0048] In the above embodiment, the length of the reaction time is related to the temperature and also has a certain relationship with the amount of reactants. The usual reaction time is 10 to 60 minutes, and the reaction time can be adjusted to 10 minutes, 20 minutes, 30 minutes, 40 minutes, 50 minutes, or 60 minutes according to the actual reaction process.

[0049] In the above embodiment, the reason for limiting the reaction time is that if the reaction time is too short, the structure of aluminum hydroxide is not completely converted and the product performance is not improved; if the reaction time is too long, the dissolution and conversion process of aluminum hydroxide is too intense and the amount of newly generated crystal nuclei is too large, which will lead to the refinement of the particle size of aluminum oxide hydrate, thereby affecting the solubility performance of aluminum oxide.

[0050] As an optional embodiment, the step of subjecting the aluminum hydroxide slurry to a high temperature reaction to obtain aluminum oxide hydrate specifically includes:

[0051] subjecting the aluminum hydroxide slurry to a high temperature reaction to obtain a reaction product;

[0052] The reaction product is separated and washed to obtain aluminum oxide hydrate.

[0053] In the above embodiment, after the product after the reaction enters the flat disc filter, hot water is used to separate and clean the product to remove excess impurities and reaction solution to obtain alumina hydrate.

[0054] As an optional implementation, the temperature of the low-temperature calcination is 550°C to 750°C.

[0055] In the above embodiment, the alumina hydrate is calcined at a low temperature. At this calcination temperature, the alumina hydrate can be decomposed into alumina. At the same time, the alumina obtained by calcination has a special structure, which can improve its solubility.

[0056] In addition, low-temperature roasting can also save roasting energy consumption, reducing roasting energy consumption by more than 30%.

[0057] In a second aspect, based on a general inventive concept, the present invention provides a readily soluble alumina prepared by the preparation method described in the first aspect.

[0058] The easily soluble alumina is realized based on the preparation method of the easily soluble alumina mentioned above. The specific steps of the preparation method can refer to the above embodiment. Since the easily soluble alumina adopts part or all of the technical solutions of the above embodiment, it has at least all the beneficial effects brought by the technical solutions of the above embodiment, which will not be described one by one here.

[0059] As an optional embodiment, the microstructure of the easily soluble alumina is a spherical structure whose surface is covered by a large number of flakes.

[0060] As an optional embodiment, the aluminum oxide comprises at least one of the following properties: a repose angle of 25 to 28 degrees, no α-Al 2 O 3 , specific surface area is 60~100m 2 / g, bulk density is 0.5g / cm 3 ~0.8g / cm 3 .

[0061] As an optional embodiment, compared with ordinary alumina, the alumina particles below 20 μm are completely converted and can be reduced to 0, and the content of alumina particles below 45 μm is greatly reduced, which can be reduced by 40-80% compared with ordinary metallurgical grade alumina.

[0062] In the above embodiment, the structure of the obtained aluminum oxide increases its dissolution rate by more than 40% compared with ordinary aluminum oxide.

[0063] The present application will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are intended only to illustrate the present application and are not intended to limit the scope of the present application. The experimental methods for which specific conditions are not specified in the following examples are usually measured according to industry standards. If there is no corresponding industry standard, then the conditions recommended by the manufacturer are followed.

[0064] Example 1

[0065] This embodiment provides a method for preparing soluble aluminum oxide. Figure 2 As shown, the following steps are included:

[0066] Prepare a low-concentration sodium aluminate solution, separate and wash the aluminum hydroxide product and the low-concentration sodium aluminate solution from the alumina plant through the No. 2 flat disc filter to form aluminum hydroxide slurry;

[0067] The aluminum hydroxide slurry is transported to the autoclave reactor by a slurry pump for high-temperature reaction at a temperature of 240° C. for 10 minutes;

[0068] The product after the reaction is separated and washed by a No. 1 flat disc filter to obtain alumina hydrate;

[0069] The alumina hydrate is calcined at 750° C. in a muffle furnace to obtain alumina.

[0070] In this embodiment, sodium aluminate semen and hot water are used to prepare a low-concentration sodium aluminate solution, wherein the caustic concentration of the sodium aluminate semen is 150 g / L, the molecular ratio is 1.45, and hot water is added to dilute it 30 times to obtain a sodium aluminate solution with a caustic concentration of 5 g / L.

[0071] The solid content of the aluminum hydroxide slurry in this embodiment is 600 g / L.

[0072] The structure and particle size of the prepared alumina were characterized, wherein the percentage of alumina particles with a particle size of -20 μm was 0, the percentage of alumina particles with a particle size of -45 μm was 5%, the angle of repose was 26 degrees, and the α-Al 2 O 3 0, specific surface area is 90m 2 / g, bulk density is 0.65g / cm 3 , Na 2 The O content is 0.30%, and the alumina crystal form is a spherical structure covered with a large number of flakes, such as Figure 3 shown.

[0073] The solubility was tested: 0.2 g of aluminum oxide was added to 40 g of an electrolyte system at a constant temperature of 950° C., and the dissolution time was measured to be 45 seconds.

[0074] Example 2

[0075] This embodiment provides a method for preparing soluble aluminum oxide. Figure 2 As shown, the following steps are included:

[0076] Prepare a low-concentration sodium aluminate solution, separate and wash the aluminum hydroxide product and the low-concentration sodium aluminate solution from the alumina plant through the No. 2 flat disc filter to form aluminum hydroxide slurry;

[0077] The aluminum hydroxide slurry is transported to the autoclave reactor by a slurry pump for high-temperature reaction at a temperature of 190° C. for 10 minutes;

[0078] The product after the reaction is separated and washed by a No. 1 flat disc filter to obtain alumina hydrate;

[0079] The alumina hydrate is calcined at 750° C. in a muffle furnace to obtain alumina.

[0080] In this embodiment, sodium aluminate semen and hot water are used to prepare a low-concentration sodium aluminate solution, wherein the caustic concentration of the sodium aluminate semen is 150 g / L, the molecular ratio is 1.45, and hot water is added to dilute it 30 times to obtain a sodium aluminate solution with a caustic concentration of 5 g / L.

[0081] The solid content of the aluminum hydroxide slurry in this embodiment is 600 g / L.

[0082] The structure and particle size of the prepared aluminum oxide were characterized, wherein the percentage of the aluminum oxide particles with a particle size of -20 μm was 0, the percentage of the particle size of -45 μm was 6%, the angle of repose was 27 degrees, and the α-Al 2 O 3 0, specific surface area is 88m 2 / g, bulk density is 0.68g / cm 3 , Na 2 The O content is 0.31%, and the alumina crystal is a spherical structure covered with a large number of flakes.

[0083] The solubility was tested: 0.2 g of aluminum oxide was added to 40 g of an electrolyte system at a constant temperature of 950° C., and the dissolution time was measured to be 50 seconds.

[0084] Example 3

[0085] This embodiment provides a method for preparing soluble aluminum oxide. Figure 2 As shown, the following steps are included:

[0086] Prepare a low-concentration sodium aluminate solution, separate and wash the aluminum hydroxide product and the low-concentration sodium aluminate solution from the alumina plant through the No. 2 flat disc filter to form aluminum hydroxide slurry;

[0087] The aluminum hydroxide slurry is transported to the autoclave reactor by a slurry pump for high-temperature reaction at a temperature of 240° C. for 10 minutes;

[0088] The product after the reaction is separated and washed by a No. 1 flat disc filter to obtain alumina hydrate;

[0089] The alumina hydrate is calcined at 750° C. in a muffle furnace to obtain alumina.

[0090] In this embodiment, sodium aluminate semen and hot water are used to prepare a low-concentration sodium aluminate solution, wherein the caustic concentration of the sodium aluminate semen is 150 g / L, the molecular ratio is 1.43, and hot water is added to dilute it 15 times to obtain a sodium aluminate solution with a caustic concentration of 10 g / L.

[0091] The solid content of the aluminum hydroxide slurry in this embodiment is 600 g / L.

[0092] The structure and particle size of the prepared aluminum oxide were characterized, wherein the percentage of the aluminum oxide particles with a particle size of -20 μm was 0, the percentage of the particle size of -45 μm was 4%, the angle of repose was 27 degrees, and the α-Al 2 O 3 0, specific surface area is 92m 2 / g, bulk density is 0.66g / cm 3 , Na 2 The O content is 0.36%, and the alumina crystal is a spherical structure covered with a large number of flakes.

[0093] The solubility was tested: 0.2 g of aluminum oxide was added to 40 g of an electrolyte system at a constant temperature of 950° C., and the dissolution time was measured to be 40 seconds.

[0094] Example 4

[0095] This embodiment provides a method for preparing soluble aluminum oxide. Figure 2 As shown, the following steps are included:

[0096] Prepare a low-concentration sodium aluminate solution, separate and wash the aluminum hydroxide product and the low-concentration sodium aluminate solution from the alumina plant through the No. 2 flat disc filter to form aluminum hydroxide slurry;

[0097] The aluminum hydroxide slurry is transported to the autoclave reactor by a slurry pump for high-temperature reaction at a temperature of 240° C. for 10 minutes;

[0098] The product after the reaction is separated and washed by a No. 1 flat disc filter to obtain alumina hydrate;

[0099] The alumina hydrate is calcined at 650° C. in a muffle furnace to obtain alumina.

[0100] In this embodiment, sodium aluminate semen and hot water are used to prepare a low-concentration sodium aluminate solution, wherein the caustic concentration of the sodium aluminate semen is 150 g / L, the molecular ratio is 1.41, and hot water is added to dilute it 30 times to obtain a sodium aluminate solution with a caustic concentration of 5 g / L.

[0101] The solid content of the aluminum hydroxide slurry in this embodiment is 600 g / L.

[0102] The structure and particle size of the prepared aluminum oxide were characterized, wherein the percentage of the aluminum oxide particles with a particle size of -20 μm was 0, the percentage of the particle size of -45 μm was 5%, the angle of repose was 28 degrees, and the α-Al 2 O 3 0, specific surface area is 88m 2 / g, bulk density is 0.68g / cm 3 , Na 2 The O content is 0.30%, and the alumina crystal is a spherical structure covered with a large number of flakes.

[0103] The solubility was tested: 0.2 g of aluminum oxide was added to 40 g of an electrolyte system at a constant temperature of 950° C., and the dissolution time was measured to be 46 seconds.

[0104] Example 5

[0105] This embodiment provides a method for preparing soluble aluminum oxide. Figure 2 As shown, the following steps are included:

[0106] Prepare a low-concentration sodium aluminate solution, separate and wash the aluminum hydroxide product and the low-concentration sodium aluminate solution from the alumina plant through the No. 2 flat disc filter to form aluminum hydroxide slurry;

[0107] The aluminum hydroxide slurry is transported to the autoclave reactor by a slurry pump for high-temperature reaction at a temperature of 240° C. for 10 minutes;

[0108] The product after the reaction is separated and washed by a No. 1 flat disc filter to obtain alumina hydrate;

[0109] The alumina hydrate is calcined at 750° C. in a muffle furnace to obtain alumina.

[0110] In this embodiment, sodium aluminate semen and hot water are used to prepare a low-concentration sodium aluminate solution, wherein the caustic concentration of the sodium aluminate semen is 150 g / L, the molecular ratio is 1.45, and hot water is added to dilute it 30 times to obtain a sodium aluminate solution with a caustic concentration of 5 g / L.

[0111] The solid content of the aluminum hydroxide slurry in this embodiment is 100 g / L.

[0112] The structure and particle size of the prepared aluminum oxide were characterized, wherein the percentage of the aluminum oxide particles with a particle size of -20 μm was 0, the percentage of the particle size of -45 μm was 7%, the angle of repose was 27 degrees, and the α-Al 2 O 3 0, specific surface area is 84m 2 / g, bulk density is 0.68g / cm 3 , Na 2 The O content is 0.31%, and the alumina crystal is a spherical structure covered with a large number of flakes.

[0113] The solubility was tested: 0.2 g of aluminum oxide was added to 40 g of an electrolyte system at a constant temperature of 950° C., and the dissolution time was measured to be 50 seconds.

[0114] Example 6

[0115] This embodiment provides a method for preparing soluble aluminum oxide. Figure 2 As shown, the following steps are included:

[0116] Prepare a low-concentration sodium aluminate solution, separate and wash the aluminum hydroxide product and the low-concentration sodium aluminate solution from the alumina plant through the No. 2 flat disc filter to form aluminum hydroxide slurry;

[0117] The aluminum hydroxide slurry is transported to the autoclave reactor by a slurry pump for high temperature reaction at a temperature of 240° C. for 60 minutes;

[0118] The product after the reaction is separated and washed by a No. 1 flat disc filter to obtain alumina hydrate;

[0119] The alumina hydrate is calcined at 750° C. in a muffle furnace to obtain alumina.

[0120] In this embodiment, sodium aluminate semen and hot water are used to prepare a low-concentration sodium aluminate solution, wherein the caustic concentration of the sodium aluminate semen is 150 g / L, the molecular ratio is 1.45, and hot water is added to dilute it 30 times to obtain a sodium aluminate solution with a caustic concentration of 5 g / L.

[0121] The solid content of the aluminum hydroxide slurry in this embodiment is 600 g / L.

[0122] The structure and particle size of the prepared aluminum oxide were characterized, wherein the percentage of the aluminum oxide particles with a particle size of -20 μm was 0, the percentage of the particle size of -45 μm was 8%, the angle of repose was 27 degrees, and the α-Al 2 O 3 0, specific surface area is 91m 2 / g, bulk density is 0.66g / cm 3 , Na 2The O content is 0.30%, and the alumina crystal is a spherical structure covered with a large number of flakes.

[0123] The solubility was tested: 0.2 g of aluminum oxide was added to 40 g of an electrolyte system at a constant temperature of 950° C., and the dissolution time was measured to be 58 seconds.

[0124] Comparative Example

[0125] This comparative example provides a method for preparing aluminum oxide, comprising the following steps:

[0126] The aluminum hydroxide product is directly calcined at 1000°C in a muffle furnace to obtain ordinary alumina.

[0127] Ordinary alumina was characterized, where the percentage of particle size -20μm was 5%, the percentage of particle size -45μm was 15%, the angle of repose was 33 degrees, and α-Al 2 O 3 3%, specific surface area 75m 2 / g, bulk density is 0.99g / cm 3 , Na 2 The O content is 0.30%, and the alumina crystal form is an irregular mosaic structure with a smooth surface.

[0128] The solubility was tested: a certain mass of aluminum oxide was added to a certain amount of electrolyte system at a constant temperature, and the dissolution time was measured to be 108 seconds.

[0129] The experimental parameters in the preparation process provided in Examples 1 to 6 and the comparative example and the performance parameters of the finally obtained alumina products are sorted out, and the results are shown in Tables 1 and 2 below respectively:

[0130] Table 1 Experimental parameters in the preparation process of Examples 1 to 6 and Comparative Examples

[0131] Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Comparative Example Caustic soda concentration in sodium aluminate solution / (g / L) 5 5 10 5 5 5 \ Molecular ratio 1.45 1.45 1.43 1.41 1.45 1.45 \ Solid content in aluminum hydroxide slurry / (g / L) 600 600 600 600 100 600 \ Reaction temperature / ℃ 240 190 240 240 240 240 \ Reaction time / min 10 10 10 10 10 60 \ Calcination temperature / ℃ 750 750 750 650 750 750 1000

[0132] Table 2 Performance parameters of alumina products obtained in Examples 1 to 6 and Comparative Examples

[0133]

[0134]

[0135] Combining the data in Table 1 and Table 2, it can be seen that the easily soluble alumina prepared by the preparation method of the easily soluble alumina provided in Examples 1 to 6 does not contain alumina with a particle size less than 20 μm, the content of alumina with a particle size less than 45 μm is less than 10%, the angle of repose is 25 to 28 degrees, and does not contain α-Al 2 O 3, specific surface area is 60~100m 2 / g, bulk density is 0.5~0.8g / cm 3 After the solubility test, the dissolution time is 45-60s. However, the alumina structure prepared by the alumina preparation method provided in the comparative example does not meet the above requirements. After the solubility test, the dissolution time is 108s, which shows that its solubility is much lower than the alumina products in Examples 1-6.

[0136] It can be seen from the above examples that in the preparation process of soluble alumina, the method provided by the embodiment of the present invention can effectively reduce the calcination temperature, optimize the particle size and crystal structure of alumina, improve the surface activity (specific surface area), dispersion performance (loose density) and flowability (angle of repose) of alumina, and reduce the α-Al in alumina. 2 O 3 content, and make the Na in alumina 2 The O content is maintained within a reasonable range. By repeatedly comparing the data of the comparative examples and the examples, it can be found that when a certain parameter is not within the range provided in the examples of the present application, the process index is poor, and when each parameter is within the range provided in the examples of the present application, the physical and chemical indexes of alumina are optimal and the dissolution rate is the fastest.

[0137] The above description is only a specific implementation of the present application, so that those skilled in the art can understand or implement the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest range consistent with the principles and novel features applied for herein.

Claims

1. A method for preparing soluble alumina, characterized in that: The following steps are involved: mixing aluminum hydroxide and sodium aluminate solution to form aluminum hydroxide slurry; subjecting the aluminum hydroxide slurry to a high temperature reaction to obtain aluminum oxide hydrate; calcining the alumina hydrate at low temperature to obtain easily soluble alumina; The caustic soda concentration of the sodium aluminate solution is Na2O K The molecular ratio of sodium oxide to aluminum oxide in the sodium aluminate solution is α K 1.35~1.60; Relative to 1L of the aluminum hydroxide slurry, the solid content of the aluminum hydroxide slurry is 100g to 600g; The high temperature reaction is carried out in an autoclave, the reaction temperature is 190°C to 240°C, and the reaction time is 10min to 60min; The temperature of the low-temperature calcination is 550°C to 750°C.

2. The method for preparing the readily soluble alumina according to claim 1, characterized in that: The step of subjecting the aluminum hydroxide slurry to a high temperature reaction to obtain aluminum oxide hydrate specifically comprises: subjecting the aluminum hydroxide slurry to a high temperature reaction to obtain a reaction product; The reaction product is separated and washed to obtain aluminum oxide hydrate.

3. A readily soluble alumina, characterized in that: The method for preparing the easily soluble alumina according to any one of claims 1 to 2 is used, wherein the microstructure of the easily soluble alumina is a spherical structure with a surface covered by a large number of flakes, and the alumina comprises at least one of the following properties: a repose angle of 25 to 28 degrees, no α-Al2O3, a specific surface area of ​​60 to 100 m 2 / g, bulk density is 0.5~0.8g / cm 3 .

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