A method for improving the silicon content index of sodium aluminate solution in sintering process

Abstract

This application relates to the field of alumina production technology, and in particular to a method for improving the silicon content index of sodium aluminate solution in the sintering process; the method includes: dispersing the agglomerated seed crystals of the desilication reaction to activate the seed crystals and obtain highly active seed crystals; using the highly active seed crystals to perform a desilication reaction on the sodium aluminate solution of the sintering process under a preset temperature condition to improve the silicon content index of the desilication reaction; the activated seed crystals are sodium silicon slag seed crystals; by first dispersing the agglomerated seed crystals of the desilication reaction, the sodium silicon slag seed crystals in the desilication reaction are fully dispersed from large particle size to fine particle size, increasing their specific surface area, thereby obtaining highly active sodium silicon slag seed crystals, which, as homonuclear seed crystals for the desilication reaction, can improve the rate of the desilication reaction and the agglomeration speed of silica, thus improving the silicon content index in the desilication reaction stage and reducing the cost of the desilication reaction.

Description

Technical Field

[0001] This application relates to the field of alumina production technology, and more particularly to a method for increasing the silicon content index of sodium aluminate solution in the sintering process. Background Technology

[0002] In the sintering alumina production process, clinker needs to be dissolved. During this dissolution, β-2CaO·SiO2 is decomposed by the alkaline solution, causing SiO2 to exist in a metastable state in the solution. This results in an A / S ratio of only 30-50 in the crude sintering solution. Subsequently, during the carbonization process in sodium aluminate solution, the SiO2 in the solution precipitates out along with aluminum hydroxide, leading to an increase in the impurity content of the alumina. Therefore, the crude sintering solution must undergo desilication refining to meet the production requirements of fine alumina products. Currently, the most advanced desilication refining method uses a desilication machine for pressure desilication. Essentially, this involves converting SiO2 into hydrated sodium aluminosilicate with very low solubility under high temperature and pressure, thereby allowing Si to precipitate out. The specific reaction is as follows:

[0003] 2Na2SiO3+2NaAl(OH)4+aq=Na2O.Al2O3·1.7SiO2·nH2O↓+4NaOH+aq.

[0004] The product after pressure boiling desilication is sodium silicate slag (Na₂O·Al₂O₃·1.7SiO₂·nH₂O). The aluminate / saturation ratio (A / S) of the sodium aluminate solution after pressure boiling desilication can reach 300–350. However, the production of high-quality fine alumina requires increasing the A / S of the sodium aluminate solution to over 500, and some high-end products even require an A / S of over 1000. Therefore, in addition to pressure boiling desilication, lime desilication is also necessary. Lime desilication uses lime slurry for deep desilication, and the reaction is as follows:

[0005] 3Ca(OH)2+2NaAl(OH)+aq=3CaO·Al2O3·6H2O↓+2NaOH+aq;

[0006] 3CaO·Al2O3·6H2O+0.1Na2SiO3+aq=3CaO·Al2O3·0.1SiO2·5.8H2O↓+0.2NaOH+aq;

[0007] As can be seen from the molecular formulas in the above reaction process, the products after the two desilication stages are different, resulting in significantly different AO losses. Generally, lime desilication causes much greater AO losses compared to pressure boiling desilication, thus pressure boiling desilication has less AO loss and is more cost-effective. However, according to crystallography principles, crystal grains with the same or similar crystal form and seed crystals are most likely to act as nuclei, most easily promoting crystal precipitation and crystal growth. Therefore, during pressure boiling desilication, as the seed crystals continuously agglomerate and grow, their activity continuously decreases, leading to a decrease in the silicon content index of the desilication reaction in pressure boiling desilication. This necessitates the subsequent addition of a large number of seed crystals, thereby increasing the cost of pressure boiling desilication. Summary of the Invention

[0008] This application provides a method for improving the silicon content index of sodium aluminate solution in the sintering process, in order to solve the technical problem of the decrease in silicon content index during the desilication reaction in the pressure boiling desilication process in the prior art.

[0009] In a first aspect, this application provides a method for increasing the silicon content index of sodium aluminate solution in a sintering process, the method comprising:

[0010] The desilication reaction seed crystals are agglomerated and dispersed to activate the desilication reaction seed crystals, thus obtaining activated seed crystals;

[0011] Under preset temperature conditions, the activated seed crystals are used to carry out a desilication reaction on the sodium aluminate solution in the sintering process, so as to improve the silicon content index of the desilication reaction.

[0012] The activated seed crystal is a sodium silicon slag seed crystal.

[0013] Optionally, the particle size of the sodium silicate slag seed crystals satisfies a D50 of 5μm to 10μm.

[0014] Optionally, the raw materials for the desilication reaction seed crystals include a mixture of sodium silicon slag and calcium silicon slag.

[0015] Optionally, the particle size of the sodium silicate slag satisfies a D50 of 14 μm to 16 μm.

[0016] Optionally, the agglomeration and dispersing includes agglomeration and dispersing in an emulsifying and homogenizing manner.

[0017] Optionally, the desilication reaction is a pressure cooking desilication reaction.

[0018] Optionally, the sintering sodium aluminate solution comprises a mixed solution of sodium aluminate seed mother liquor and sintering sodium aluminate crude liquor, wherein the αk of the sintering sodium aluminate solution is 1.45 to 1.50.

[0019] Optionally, the alumina content of the sodium aluminate solution in the sintering process is 95 g / L to 100 g / L.

[0020] Optionally, the desilication reaction time is ≥2h.

[0021] Optionally, the preset temperature is 120℃~130℃.

[0022] The technical solutions provided in this application have the following advantages compared with the prior art:

[0023] This application provides a method for improving the silicon content index of sodium aluminate solution in a sintering process. By first agglomerating and dispersing the desilication reaction seed crystals, the sodium silicon slag seed crystals in the desilication reaction seed crystals are fully dispersed from large particles to fine particles, thereby obtaining highly active sodium silicon slag seed crystals. Without changing the original process or increasing the process operating load, the highly active sodium silicon slag seed crystals have excellent activation and core properties. As homonuclear seed crystals for the desilication reaction, they can improve the desilication reaction rate and the agglomeration speed of silicon dioxide. Therefore, the silicon content index can be improved in the desilication reaction stage, thereby reducing the cost of the desilication reaction. Attached Figure Description

[0024] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0025] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is a schematic flowchart illustrating a method for increasing the silicon content index of sodium aluminate solution in a sintering process, as provided in an embodiment of this application. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0028] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0029] The creative thinking behind this application is:

[0030] Compared to pressure boiling desilication, lime desilication generally results in significant AO (anaerobic digestion) loss. Therefore, pressure boiling desilication has less AO loss and is more cost-effective, as shown in Table 1.

[0031] Table 1. Products of the two-stage desilication reaction

[0032]

[0033] Therefore, it is evident that pressure boiling desilication results in a loss of 1 kg AO for every 1 kg SiO2 removed, while lime desilication results in a loss of 17 kg AO for every 1 kg SiO2 removed. Lime desilication causes a significant AO loss, while pressure boiling desilication results in less AO loss and is more cost-effective. However, according to crystallography principles, grains with the same or similar crystal forms and seed crystals are most likely to act as nuclei, most easily promoting crystal precipitation and grain attachment and growth. Therefore, during pressure boiling desilication, as the seed crystals continuously agglomerate and grow, their activity continuously decreases, leading to a decrease in the silicon content index of the desilication reaction in pressure boiling desilication. This necessitates the subsequent addition of a large amount of seed crystals, thereby increasing the cost of pressure boiling desilication.

[0034] like Figure 1 As shown in the embodiments of this application, a method for improving the silicon content index of sodium aluminate solution in a sintering process is provided, the method comprising:

[0035] S1. The desilication reaction seed crystals are agglomerated and dispersed to activate the desilication reaction seed crystals and obtain activated seed crystals;

[0036] S2. Under preset temperature conditions, the activated seed crystals are used to carry out a desilication reaction on the sodium aluminate solution of the sintering method, so as to improve the silicon content index of the desilication reaction;

[0037] The activated seed crystal is a sodium silicon slag seed crystal.

[0038] In this embodiment, the preset temperature is a constant temperature during the desilication reaction of sodium aluminate solution in the sintering method. This constant temperature is generally set in the range of 120°C to 130°C, so that the sodium aluminate solution in the sintering method has sufficient desilication driving force and ensures the aggregation rate of silica in the sodium aluminate solution, so as to realize the normal progress of the desilication reaction of sodium aluminate solution in the sintering method.

[0039] In some optional embodiments, the particle size of the sodium silicate slag seed crystals satisfies a D50 of 5 μm to 10 μm.

[0040] In this embodiment of the application, controlling the specific particle size of the sodium silicon slag seed crystals can make the sodium silicon slag seed crystals be in a highly active state. By utilizing the characteristics of homonuclear seed crystals, the rate of desilication reaction and the agglomeration speed of silicon dioxide can be increased by using sodium silicon slag within this particle size range, thereby increasing the silicon content index in the desilication reaction.

[0041] The D50 can be 5μm, 6μm, 7μm, 8μm, 9μm, or 10μm.

[0042] In some alternative embodiments, the raw materials for the desilication reaction seed crystals include a mixture of sodium silicon slag and calcium silicon slag.

[0043] In this embodiment of the application, the specific principle composition of the desilication reaction seed crystal is refined. By introducing calcium silicon slag, the use of sodium silicon slag can be reduced on the one hand, and on the other hand, calcium silicon slag can react with sodium elements in sodium silicon slag, thereby consuming a large amount of sodium element impurities in sodium silicon slag, which facilitates the subsequent obtaining of purified sodium silicon slag seed crystals.

[0044] In some optional embodiments, the particle size of the sodium silicate slag satisfies a D50 of 14 μm to 16 μm.

[0045] In this embodiment, by refining the specific particle size of the sodium silicon slag, most of the sodium silicon slag can be covered, and it is convenient to obtain the expected particle size of D50 of 5μm to 10μm after subsequent agglomeration and dispersion, thereby obtaining activated seed crystals.

[0046] In some alternative implementations, the agglomeration and dispersing includes agglomeration and dispersing in an emulsifying and homogenizing manner.

[0047] In the embodiments of this application, the specific method of controlling agglomeration and dispersion is to use emulsification and homogenization to ensure that sodium silicon slag and calcium silicon slag are fully mixed and that the calcium silicon slag is transformed into sodium silicon slag, thereby obtaining purified sodium silicon slag seed crystals. At the same time, the emulsification and homogenization method can also make the particle size of the obtained sodium silicon slag seed crystals reach the range of D50 of 5μm to 10μm, thereby obtaining active seed crystals.

[0048] In some alternative embodiments, the desilication reaction is a pressure cooking desilication reaction.

[0049] In this embodiment of the application, by limiting the specific type of desilication reaction, the pressure boiling desilication method has certain advantages over other desilication methods because the AO loss is small and the cost performance is higher. At the same time, the pressure boiling desilication method is also conducive to the complete reaction between the active seed crystals and sodium aluminate, thereby effectively improving the silicon content index of the desilication reaction.

[0050] In some optional embodiments, the sintering sodium aluminate solution comprises a mixed solution of sodium aluminate seed mother liquor and sintering sodium aluminate crude liquor, wherein the αk of the sintering sodium aluminate solution is 1.45 to 1.50.

[0051] In some optional embodiments, the alumina content of the sodium aluminate solution in the sintering process is 95 g / L to 100 g / L.

[0052] In this embodiment, by controlling the specific composition of the sodium aluminate solution in the sintering process, as well as the specific αk and specific alumina content, the proportion of aluminum element in the sodium aluminate solution in the sintering process and the solution characteristics of the solution can be clearly defined, which facilitates the complete reaction between the sodium silicon slag activating the seed crystals and sodium aluminate, thereby improving the silicon content index of the desilication reaction.

[0053] In some alternative implementations, the desilication reaction takes ≥2 hours.

[0054] In this embodiment of the application, by refining the specific time of the desilication reaction, the reaction between the activated seed crystal and the sodium aluminate solution of the sintering method can be made complete, thereby completing the desilication of the sodium aluminate solution of the sintering method and thus improving the silicon content index in the desilication reaction.

[0055] In some optional implementations, the preset temperature is 120°C to 130°C.

[0056] In this embodiment of the application, the specific temperature of the preset temperature is defined, which can clarify the normal temperature required for desilication by pressure cooking, and can make the desilication reaction proceed normally. Therefore, without increasing the process load, the silicon content index of the desilication reaction can be effectively improved by adding activated seed crystals.

[0057] The present application is further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the application. Experimental methods in the following embodiments that do not specify specific conditions are generally determined according to national standards. If there is no corresponding national standard, then general international standards, conventional conditions, or conditions recommended by the manufacturer are followed.

[0058] Example 1

[0059] After the raw materials for the desilication reaction seed crystals were dispersed using an emulsifying homogenizer, the sodium silicon slag D50 of the activated seed crystals was measured to be 9.171 μm. The desilication stock solution was prepared by mixing the seed mother liquor and the crude liquor from the sintering method, with an αk of 1.45–1.5 and an AO of 95 g / L–100 g / L. Under constant temperature conditions of 125 °C, the D50 of the activated seed crystals was measured to be 9.171 μm, and the solid content of the silicon stock solution was 40 g / L. After the desilication reaction was carried out for 2 hours, the silicon content index of the desilication solution was measured.

[0060] Example 2

[0061] After the raw material of sodium silicon slag seed crystals was dispersed using an emulsifying homogenizer, the D50 of sodium silicon slag in the activated seed crystals was measured to be 8.448 μm. A desilication stock solution was prepared using seed mother liquor and sintering crude liquor, with an αk of 1.45-1.5 and an AO of 95 g / L-100 g / L. Under constant temperature conditions of 125℃, the D50 of the activated seed crystals was measured to be 8.448 μm and the solid content of the silicon stock solution was 40 g / L. After the desilication reaction was carried out for 2 hours, the silicon content index of the desilication solution was measured.

[0062] Example 3

[0063] After the raw material of sodium silicon slag seed crystals was dispersed using an emulsifying homogenizer, the D50 of sodium silicon slag in the activated seed crystals was measured to be 5.697 μm. A desilication stock solution was prepared using seed mother liquor and sintering crude liquor, with an αk of 1.45-1.5 and an AO of 95 g / L-100 g / L. Under constant temperature conditions of 125℃, the D50 of the activated seed crystals was measured to be 5.697 μm, and the solid content of the silicon stock solution was 40 g / L. After the desilication reaction was carried out for 2 hours, the silicon content index of the desilication solution was measured.

[0064] Comparative Example 1

[0065] The desilication stock solution was prepared by mixing seed mother liquor and sintering crude liquor, with αk of 1.45-1.5 and AO of 95g / L-100g / L. Under constant temperature of 125℃, the D50 of the activated seed crystal was measured to be 17.697μm and the solid content of the silicon stock solution was 40g / L. After the desilication reaction was carried out for 2 hours, the silicon content index of the desilication solution was measured.

[0066] Comparative Example 2

[0067] The desilication stock solution was prepared by mixing seed mother liquor and sintering crude liquor, with αk of 1.45-1.5 and AO of 95g / L-100g / L. Under constant temperature of 125℃, the D50 of the activated seed crystal was measured to be 13.514μm and the solid content of the silicon stock solution was 40g / L. After the desilication reaction was carried out for 2 hours, the silicon content index of the desilication solution was measured.

[0068] Relevant experimental and effect data:

[0069] The desilication stock solution and silicon content index in Examples 1-3 and Comparative Examples 1-2 were statistically analyzed, and the results are shown in Table 1.

[0070] Table 1. Information on desilication stock solution and silicon content index.

[0071]

[0072] As shown in Table 1, the method for improving the silicon content index of sodium aluminate solution in the sintering process provided in this application embodiment involves first agglomerating and dispersing the desilication reaction seed crystals. This allows the sodium silicon slag seed crystals in the desilication reaction seed crystals to be fully dispersed from large particle size into fine particle size, thereby obtaining highly active sodium silicon slag seed crystals. As homonuclear seed crystals for the desilication reaction, this can improve the desilication reaction rate and the agglomeration speed of silicon dioxide. Therefore, the silicon content index can be improved in the desilication reaction stage, thereby reducing the cost of the desilication reaction.

[0073] In summary, the method for improving the silicon content index of sodium aluminate solution in the sintering process provided in this application embodiment has the advantages of being simple and easy to implement, having a high silicon content index, low system AO loss, and high production efficiency, without changing the original process or increasing the process operating load.

[0074] Various embodiments of this application may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a hard limitation on the scope of this application; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values ​​within that range. For example, it should be considered that the range description from 1 to 6 has 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., and single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Furthermore, whenever a numerical range is referred to herein, it means including any referenced number (fraction or integer) within the referred range.

[0075] In this application, unless otherwise stated, directional terms such as "upper" and "lower" specifically refer to the drawing directions in the accompanying drawings. Furthermore, in the description of this application, terms such as "comprising" and "including" mean "including but not limited to." In this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. In this document, "and / or" describes the relationship between related objects, indicating that three relationships can exist; for example, A and / or B can represent: A alone, A and B simultaneously, or B alone. A and B can be singular or plural. In this document, "at least one" means one or more, and "more than one" means two or more. "At least one," "at least one of the following," 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 both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be a single or multiple.

[0076] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A method for increasing the silicon content index of sodium aluminate solution in a sintering process, characterized in that, The method includes: The seed crystals that have cyclically agglomerated during the desilication reaction are dispersed to activate the seed crystals and obtain highly active seed crystals. Under preset temperature conditions, the highly active seed crystals are used to carry out a desilication reaction on the sodium aluminate solution in the sintering process, so as to improve the silicon content index of the desilication reaction. The highly active seed crystal is a sodium silicate slag seed crystal, and the particle size of the sodium silicate slag seed crystal meets the requirement that the D50 is 6μm to 10μm; The raw material for the desilication reaction seed crystals includes a mixture of sodium silicon slag and calcium silicon slag; the particle size of the sodium silicon slag satisfies D50 of 14μm to 20μm; The dispersing includes dispersing agglomerates in an emulsifying and homogenizing manner; The desilication reaction is a pressure cooking desilication reaction, with a preset temperature of 120℃~130℃.

2. The method according to claim 1, characterized in that, The sintering sodium aluminate solution comprises a mixed solution of sodium aluminate seed mother liquor and sintering sodium aluminate crude liquor, wherein the αk of the sintering sodium aluminate solution is 1.45 to 1.

50.

3. The method according to claim 1, characterized in that, The alumina content of the sodium aluminate solution obtained by the sintering method is 95 g / L to 100 g / L.

4. The method according to claim 1, characterized in that, The desilication reaction takes ≥2 hours.

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