Method for preparing Bayer stone based on high-alphak sodium aluminate solution

Abstract

The invention provides a method for preparing Bayer stone based on a high-alpha-k sodium aluminate solution, and belongs to the field of aluminum oxide preparation. The method comprises the following steps: adding a morphology regulating agent into a sodium aluminate solution with set alpha k to obtain a mixed solution; introducing a mixed gas with a set CO2 volume concentration into the mixed solution to perform a carbonation reaction under a set condition, and obtaining Bayer stone slurry when a reaction system of the carbonation reaction reaches a set NK concentration; and carrying out solid-liquid separation on the Bayer stone slurry to obtain the Bayer stone. The method comprises the following steps: firstly, adding a morphological regulating agent into a sodium aluminate solution to regulate the growth process and morphological characteristics of crystals so as to reduce crystal defects and impurity content; secondly, the carbonation reaction rate and the product composition are controlled by controlling the carbonation reaction conditions; and finally, by accurately controlling the end-point caustic alkali concentration, the mixing of impurities in the forming process of the Bayer stone can be reduced, so that a high-purity Bayer stone product is obtained.

Description

Technical Field

[0001] The present application relates to the technical field of alumina preparation, and in particular to a method for preparing Bayerite based on a high αk sodium aluminate solution. Background Art

[0002] Bayerite is a kind of gibbsite, belonging to the monoclinic system, with a special structure. It is often used as a catalyst or catalyst carrier, a precursor of transitional alumina and activated alumina, an adsorbent for metal ions and phosphates, etc. It is a high-quality inorganic raw material. After calcination, the specific surface area is 80-100g / m 2 Increased to 360g / m 2 As mentioned above, compared with γ-Al2O3 produced by pseudo-boehmite, the activated alumina calcined by Bayerite has better acid-base properties and thermal stability in catalytic reactions related to heavy oil and macromolecular diffusion, and becomes the main catalyst raw material to replace pseudo-boehmite.

[0003] At present, the known preparation methods mainly focus on the low-temperature natural decomposition of sodium aluminate solution, the neutralization method, and the sodium aluminate CO2 decomposition method. The low-temperature natural decomposition method requires a high amount of cold, and the decomposition speed is slow, the output rate is low, and the industrial operation is relatively difficult. The neutralization method is mainly an acid-base precipitation reaction, with a fast reaction rate, a fine product particle size, and difficulty in comprehensive utilization of waste liquid, which is not conducive to application and promotion. In addition, when the acid-base precipitation method is used to prepare aluminum hydroxide, its crystal form is greatly affected by pH, wherein Bayerite is mainly used in the process of 9 to 12, and α-phase aluminum hydroxide is mainly used above 12. It is found in the actual production process that the product purity prepared by this method is relatively low, and it contains α-phase aluminum hydroxide, which is not conducive to industrial promotion. The sodium aluminate CO2 decomposition method is currently the main industrial production method. The sodium aluminate solution is mainly derived from the sodium aluminate concentrate or its seed liquor prepared by the soda lime-sintering process and the modified Bayer process. The former solution has an αk of 1.4-2.0, and the preparation process requires cooling treatment, and some crystal seeds need to be added for decomposition, so the production cost is relatively high. The latter solution has an αk of 2.5-4.5, and carbon decomposition is directly carried out under high alkaline conditions, which significantly reduces the cost. However, it is controlled by the relationship between the product crystal form and pH, and the product purity is relatively low, basically below 98%. In addition, the product particle size fluctuates greatly. Although adjustments can be made, precise control is required, and it is easy to cause problems such as catalyst non-formation during the use of downstream catalysts, which limits its application in catalysts. Summary of the invention

[0004] The present application provides a method for preparing Bayerite based on a high αk sodium aluminate solution to solve the following technical problems:

[0005] How to improve the purity of Bayerite.

[0006] The present application provides a method for preparing Bayerite based on a high αk sodium aluminate solution, the method comprising:

[0007] adding a morphology control agent to a sodium aluminate solution having a set αk to obtain a mixed solution;

[0008] A mixed gas having a set CO2 volume concentration is introduced into the mixed liquid to perform a carbonation reaction under set conditions, and the N K Reaching the setting N K concentration to obtain a Bayerite slurry; and

[0009] The Bayerite slurry is subjected to solid-liquid separation to obtain Bayerite.

[0010] Optionally, the setting αk is 2.0 to 4.5.

[0011] Optionally, the N in the sodium aluminate solution k The concentration is 50g / L~130g / L.

[0012] Optionally, the sodium aluminate solution is one or more of a sintering process mother liquor and a seed mother liquor.

[0013] Optionally, the mass of the morphology control agent is 1‰ to 1% of the total volume of the sodium aluminate solution.

[0014] Optionally, the morphology regulator is an organic crystallization aid, which includes the following chemical components in parts by mass: sodium unsaturated fatty acid: 20 to 30 parts, polyethylene glycol dioleate: 15 to 25 parts, sodium secondary alkyl sulfonate: 10 to 15 parts, Span 80: 5 to 10 parts, triethanolamine: 10 to 20 parts, and polyether defoamer: 1 to 3 parts.

[0015] Optionally, the flow rate of the mixed gas is 0.3m 3 / h~600m 3 / min, and the set CO2 volume concentration is 35% to 100%.

[0016] Optionally, the temperature of the carbonation reaction is 30° C. to 60° C., and the time of the carbonation reaction is 15 min to 45 min.

[0017] Optionally, the setting N K The concentration is 8g / L~15g / L.

[0018] Optionally, the Bayerite satisfies at least one of the following properties: particle size D50 is 15 μm to 25 μm, and purity is ≥97.5%.

[0019] The above technical solution provided by the embodiment of the present application has the following advantages compared with the prior art:

[0020] The present application provides a method for preparing Bayerite based on a high αk sodium aluminate solution, comprising: adding a morphology control agent to a sodium aluminate solution with a set αk to obtain a mixed solution; introducing a mixed gas with a set CO2 volume concentration into the mixed solution to perform a carbonation reaction under set conditions, and waiting for the N in the carbonation reaction system to K Reaching the setting N K concentration to obtain Bayerite slurry; and the Bayerite slurry is subjected to solid-liquid separation to obtain Bayerite. Firstly, a morphology regulator is added to the sodium aluminate solution to regulate the growth process and morphology characteristics of the crystal, thereby reducing crystal defects and impurity content, which helps to improve the purity of the product; secondly, the carbonation reaction conditions are controlled to control the rate of the carbonation reaction and the composition of the product; finally, the endpoint caustic soda concentration is accurately controlled to ensure that the Bayerite is less mixed with impurities during the formation process, thereby obtaining a high-purity Bayerite product. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] 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.

[0022] In order to more clearly illustrate the embodiments of the present application or the technical solutions in 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.

[0023] Figure 1 A schematic flow chart of a method for preparing Bayerite based on a high αk sodium aluminate solution provided in an embodiment of the present application;

[0024] Figure 2 The XRD pattern of Bayerite provided in Example 1 of the present application;

[0025] Figure 3 The XRD pattern of Bayerite provided in Example 2 of the present application;

[0026] Figure 4 The XRD pattern of Bayerite provided in Example 3 of the present application;

[0027] Figure 5 The XRD pattern of Bayerite provided in Example 4 of the present application;

[0028] Figure 6 The XRD pattern of Bayerite provided in Example 5 of the present application;

[0029] Figure 7 The XRD pattern of Bayerite provided in Example 6 of the present application;

[0030] Figure 8 A scanning electron microscope image of Bayerite provided for Comparative Example 1 of the present application;

[0031] Fig. 9 The XRD pattern of Bayerite provided for Comparative Example 2 of the present application;

[0032] Fig.10 This is a scanning electron microscope image of Bayerite sample 1 obtained from the industrial scale-up experiment of Example 3 of the present application;

[0033] Fig.11 The XRD pattern of Bayerite sample 1 obtained from the industrial scale-up experiment of Example 3 of the present application;

[0034] Fig.12 This is a scanning electron microscope image of Bayerite sample 2 obtained from the industrial scale-up experiment of Example 3 of the present application;

[0035] Fig.13 The XRD pattern of Bayerite sample 2 obtained from the industrial scale-up experiment of Example 3 of the present application;

[0036] Fig.14 This is a scanning electron microscope image of Bayerite sample 3 obtained from the industrial scale-up experiment of Example 3 of the present application;

[0037] Fig.15 This is the XRD diagram of Bayerite sample 3 obtained in the industrial scale-up experiment of Example 3 of the present application. DETAILED DESCRIPTION

[0038] 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.

[0039] 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.

[0040] In addition, in the description of the specification of the present application, the terms "including", "comprising", etc. mean "including but not limited to". In this article, relational terms such as "first" and "second", etc. are only used 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 article, "and / or" describes the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. Wherein A and B can be singular or plural. In this article, "at least one" means one or more, and "plurality" means two or more. "At least one", "the following at least one item (items)" or similar expressions refer to any combination of these items, including any combination of single items (items) or plural items (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, where a, b, and c can be single or multiple. In this article, "parts" such as parts by weight, parts by mass, etc., represent the proportional relationship between the components. "The xxx ratio of A to B" means the ratio of A as the numerator and B as the denominator.

[0041] 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.

[0042] Figure 1 A schematic flow chart of a method for preparing Bayerite based on a high αk sodium aluminate solution provided in an embodiment of the present application.

[0043] See also Figure 1 The present application provides a method for preparing Bayerite based on a high αk sodium aluminate solution, the method comprising:

[0044] S1, adding a morphology control agent to a sodium aluminate solution having a set αk to obtain a mixed solution;

[0045] In some embodiments, the setting αk is 2.0-4.5.

[0046] In some embodiments, the N in the sodium aluminate solution is k The concentration is 50g / L~130g / L.

[0047] It should be noted that αk and N mentioned in the present invention are k It is the definition of the index in sodium aluminate solution in the alumina industry. Specifically, it refers to the Na2O content of the sodium aluminate solution, including the Na2O that reacts with alumina to form sodium aluminate and the free Na2O in the form of NaOH, recorded as N T The free Na2O in the form of NaOH is denoted as Nk, and its content refers to the concentration of NaOH in the form of Na2O in the sodium aluminate solution. The molar ratio of caustic soda Na2O to Al2O3 in the sodium aluminate solution is denoted as αk.

[0048] In some embodiments, the sodium aluminate solution is: one of the sintering process mother liquor, seed mother liquor, or a mixed solution.

[0049] In some embodiments, the sodium aluminate solution needs to be filtered before the reaction, and the filtering device is a conventional device.

[0050] The present invention directly utilizes sodium aluminate solution with αk of 2.0 to 4.5 to produce chemical alumina with high added value (such as regular Bayer stone), which is an important way to improve the economic benefits of sintering alumina production. For example, αk can be set to 2.0, 2.5, 3, 3.5, 4, 4.5, etc., and N in the sodium aluminate solution k The concentration can be 50g / L, 60g / L, 70g / L, 80g / L, 90g / L, 100g / L, 110g / L, 120g / L, 130g / L, etc.

[0051] In some embodiments, the mass of the morphology control agent is 1‰ to 1% of the total volume of the sodium aluminate solution.

[0052] The addition of morphology control agent can control the morphology and crystal structure of Bayerite, thereby affecting its performance and application field. The morphology control agent used in the present invention mainly plays a role in the initial stage of the reaction. At this stage, the aluminum ions in the sodium aluminate solution begin to combine with hydroxide ions to form crystal nuclei, and the addition of morphology control agent can quickly act on these crystal nuclei to control their size and shape. At the same time, the morphology control agent can accelerate the formation of crystal nuclei, which helps to form more uniform and regular Bayerite crystals in the subsequent reaction process. The morphology control agent can not only control the size of the crystal nucleus, but also improve the morphology of the crystal through its specific chemical action, including the size, shape, surface roughness and other characteristics of the crystal, which will directly affect the physical and chemical properties of Bayerite. In addition, by regulating the growth process and morphological characteristics of the crystal, the crystal defects and impurity content are reduced, which helps to improve the purity of the product. Exemplarily, the mass of the morphology control agent is 1‰, 0.1%, 0.2%, 0.4%, 0.6%, 0.8%, 1%, etc. of the total volume of the sodium aluminate solution.

[0053] In some embodiments, the morphology control agent is a crystallization aid, which includes the following chemical components by mass fraction: sodium unsaturated fatty acid: 20 to 30 parts, polyethylene glycol dioleate: 15 to 25 parts, sodium secondary alkyl sulfonate: 10 to 15 parts, Span 80: 5 to 10 parts, triethanolamine: 10 to 20 parts, and polyether defoamer: 1 to 3 parts.

[0054] As a surfactant in the system, sodium unsaturated fatty acids can reduce the surface tension of the solution and promote the formation and dispersion of crystal nuclei. Its unsaturated structure may help introduce defects during crystal growth, thereby regulating the morphology of the crystal. Polyethylene glycol dioleate is a long-chain ester compound with good lubricity and dispersibility. It can act as a lubricant during crystal growth, reduce friction and agglomeration between crystals, and help form a more uniform crystal structure. Sodium secondary alkyl sulfonate is an anionic surfactant with excellent washing, penetration and dispersing properties. In this system, it may affect the growth rate and direction of the crystal by adsorbing on the crystal surface, thereby regulating the morphology and size of the crystal. Span 80 is a non-ionic surfactant commonly used as an emulsifier and stabilizer. In the process of preparing Bayerite, it can promote uniform mixing between the components, prevent phase separation, and help form a stable emulsion or suspension system. Triethanolamine is alkaline and can form a complex with aluminum ions in sodium aluminate solution, thereby changing the existence state of aluminum ions and affecting their precipitation behavior and crystal structure. At the same time, it may also act as a buffer to adjust the pH value of the reaction system and stabilize the reaction conditions. During the preparation process, foam may be generated due to stirring, ventilation and other operations. Polyether defoamers can quickly destroy the stability of the foam, causing the foam to burst quickly and keep the reaction system stable.

[0055] The chemical components of organic crystallization aids can produce synergistic and synergistic effects after compounding, making the entire organic crystallization aid system show excellent performance in regulating the morphology and crystal structure of Bayerite. This synergistic effect comes from the chemical interaction between the components, surface adsorption and steric hindrance effects. Exemplarily, the mass fraction of sodium unsaturated fatty acid can be 20 parts, 21 parts, 22 parts, 23 parts, 24 parts, 25 parts, 26 parts, 27 parts, 28 parts, 29 parts, 30 parts, etc., the mass fraction of polyethylene glycol dioleate can be 15 parts, 17 parts, 17 parts, 19 parts, 21 parts, 23 parts, 25 parts, etc., the mass fraction of sodium secondary alkyl sulfonate can be 10 parts, 11 parts, 12 parts, 13 parts, 14 parts, 15 parts, etc., the mass fraction of Span 80 can be 5 parts, 6 parts, 7 parts, 8 parts, 9 parts, 10 parts, etc., the mass fraction of triethanolamine can be 10 parts, 12 parts, 14 parts, 16 parts, 18 parts, 20 parts, etc., and the mass fraction of polyether defoamer can be 1 part, 2 parts, 3 parts, etc.

[0056] The organic crystallization aid used in the present invention has the following preparation process: unsaturated fatty acid sodium, polyethylene glycol dioleate, secondary alkyl sulfonate sodium, Span 80 emulsifier, triethanolamine, polyether defoamer and water are uniformly stirred in a proportion within the range of 40°C to 60°C.

[0057] S2, introducing a mixed gas having a set CO2 volume concentration into the mixed liquid to perform a carbonation reaction under set conditions, and wait for the N K Reaching the setting N K concentration to obtain a Bayerite slurry; and

[0058] The present invention adopts the carbonation method to prepare Bayerite, and the reaction equation of its preparation process is as follows:

[0059] 2NaOH+ CO2 ==== Na2CO3+ H2O (1)

[0060] 2NaAlO2+ CO2+ 3H2O === 2Al(OH)3+Na2CO3 (2)

[0061] NaAlO2+ 2H2O ==== Al(OH)3+ NaOH (3)

[0062] Na2CO3+ CO2+ H2O === 2NaHCO3 (4)

[0063] NaHCO3+ Al(OH)3=== 3NaAl(OH)2CO3+ H2O (5)

[0064] Reaction (2) is recorded as a neutralization reaction, and the generated water and alumina can be converted into pseudo-boehmite after aging under appropriate conditions. Reaction (3) is recorded as a decomposition reaction, and the generated water and alumina are β1-Al2O3·3H2O (or α-Al2O3·3H2O). Reactions (2) and (3) are parallel reactions. Therefore, whether the hydrated alumina generated during the carbonation process is pseudo-boehmite (after aging), a mixture of pseudo-boehmite and gibbsite, or gibbsite depends mainly on the speed and reaction degree of the two reactions (2) and (3). The speed of these two reactions mainly depends on the concentration of the sodium aluminate solution, the reaction temperature, the flow rate and concentration of the CO2 mixed gas, the stirring speed, etc., and therefore adjustments are made based on various factors.

[0065] In some embodiments, the flow rate of the mixed gas is 0.3m 3 / h~600m 3 / min, and the set CO2 volume concentration is 35% to 100%.

[0066] The volume concentration of CO2 directly affects the reaction speed and efficiency. When it is lower than 35%, the neutralization reaction speed is relatively slow, which affects the efficiency of industrial implementation. For example, the flow rate of the mixed gas can be 0.3m 3 / h、1m 3 / h、10m 3 / h、100m 3 / h、200m 3 / h、300m 3 / h、400m 3 / h、500m 3 / h、600m 3 / min, etc., and the CO2 volume concentration can be set to 35%, 40%, 50%, 60%, 70%, 80%, 90%, 100%, etc.

[0067] In some embodiments, the temperature of the carbonation reaction is 30° C. to 60° C., and the time of the carbonation reaction is 15 min to 45 min.

[0068] The sodium aluminate solution raw material selected by the present invention has high α K , which promotes the carbonation reaction, and the reaction speed is faster than that of low caustic ratio conditions. The method has a short reaction time, an average residence time of 15min to 45min, high product purity, low cost, and industrial scale-up products have been well applied in the catalyst industry. Exemplarily, the temperature of the carbonation reaction can be 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, etc., and the time of the carbonation reaction can be 15min, 20min, 25min, 30min, 35min, 40min, 45min, etc.

[0069] In some embodiments, the setting N K The concentration is 8g / L~15g / L.

[0070] In order to ensure the purity of the product, the present invention adjusts the end point caustic soda concentration by controlling the end point caustic soda concentration, and the end point caustic soda concentration is controlled to be 8 to 15 g / l. By accurately controlling the reaction conditions and the end point caustic soda concentration, it can be ensured that the Bayerite is less mixed with impurities during the formation process, thereby obtaining a high-purity product. For example, setting N K The concentration can be 8g / L, 9g / L, 10g / L, 11g / L, 12g / L, 13g / L, 14g / L, 15g / L, etc.

[0071] S3, separating the bayerite slurry into solid and liquid to obtain bayerite.

[0072] In some embodiments, the filtrate obtained after solid-liquid separation is mainly composed of sodium carbonate, which can be directly used as a sintering ingredient for bauxite after evaporation and concentration.

[0073] In some embodiments, the bayerite satisfies at least one of the following properties: a particle size D50 of 15 μm to 25 μm, and a purity of ≥97.5%.

[0074] It can be understood that the particle size D50 is also called the median diameter or median particle size, which is the particle size corresponding to when the cumulative particle size distribution percentage of a sample reaches 50%. The present invention controls the reaction activity, stabilizes the reaction temperature, regulates the product morphology, controls the reaction end point N K Etc. to ensure the feasibility of the process, high product purity, and uniform particle size distribution.

[0075] 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.

[0076] The morphology regulator in the embodiment is a crystallization aid, which consists of 20wt.% sodium linoleate, 17wt.% polyethylene glycol dioleate, 12wt.% sodium secondary alkyl sulfonate, 5wt.% Span 80 emulsifier, 17wt.% triethanolamine, 3wt.% polyether defoamer, and 30wt.% water.

[0077] Example 1

[0078] Take the alumina sintering method seed solution, αk 4.5, N k82g / l, after filtering, cool to 30℃, take an appropriate amount and pour it into a beaker with a carbon separation device, start stirring at a speed of 800r / min, add 0.7% crystallization aid, stir for 5min, and then pass 100% CO2 (0.4m 3 / h) ) Carry out carbon decomposition, end point N K Controlled at 15g / L, Bayerite slurry is obtained, filtered to obtain filter cake, and washed and dried to obtain Bayerite. Its main properties are shown in Figure 1 and Figure 2 .

[0079] Example 2

[0080] Take the alumina sintering method seed liquor, αk 3.5, N k 95g / l, after filtering, cool to 30℃, take an appropriate amount and pour it into a beaker with a carbon separation device, start stirring at a speed of 600r / min, add 0.5% crystallization aid, stir for 5min, and then pass 75% CO2 (0.4m 3 / h) to decompose carbon, and the end point N K The concentration of Bayerite is controlled at 12g / L to obtain Bayerite slurry, which is filtered to obtain filter cake, which is then washed and dried to obtain Bayerite. Its main properties are shown in Table 1 and Figure 3 .

[0081] Example 3

[0082] Take the mother liquor of alumina sintering process, αk 2.8, N k 99g / l, after filtering, cool to 40℃, take an appropriate amount and pour it into a beaker with a carbon separation device, start stirring at a speed of 600r / min, add 0.5% crystallization aid, stir for 5min, and then pass 45% CO2 (0.4m 3 / h) to decompose carbon, and the end point N K Controlled at 12g / L, Bayerite slurry is obtained, filtered to obtain filter cake, and washed and dried to obtain Bayerite. Its main properties are shown in Figure 1 and Figure 4 .

[0083] Example 4

[0084] Take the mother liquor of alumina sintering process, αk2.4, N k 115g / l, after filtering, cool to 40℃, take an appropriate amount and pour it into a beaker with a carbon separation device, start stirring at a speed of 600r / min, add 0.3% crystallization aid, stir for 5min, and then pass 42% CO2 (0.4m 3 / h) to decompose carbon, and the end point N KControlled at 10g / L, Bayerite slurry is obtained, filtered to obtain filter cake, and washed and dried to obtain Bayerite. Its main properties are shown in Figure 1 and Figure 5 .

[0085] Example 5

[0086] Take the mother liquor and seed liquor of the alumina sintering process, mix and prepare, αk2.0, N k 93g / l, after filtering, cool to 40℃, take an appropriate amount and pour it into a beaker with a carbon separation device, start stirring at a speed of 600r / min, add 0.1% crystallization aid, stir for 5min, and then pass 37% CO2 (0.4m 3 / h) to decompose carbon, and the end point N K Controlled at 10g / L, Bayerite slurry is obtained, filtered to obtain filter cake, and washed and dried to obtain Bayerite. Its main properties are shown in Figure 1 and Figure 6 .

[0087] Example 6

[0088] Take the mother liquor and seed liquor of the alumina sintering process, mix and prepare, αk 2.0, N k 93g / l, after filtering, cool to 60℃, take an appropriate amount and pour it into a beaker with a carbon separation device, start stirring at a speed of 600r / min, add 0.3% crystallization aid, stir for 5min, and then pass 42% CO2 (0.4m 3 / h) to decompose carbon, and the end point N K Controlled at 10g / L, Bayerite slurry is obtained, filtered to obtain filter cake, and washed and dried to obtain Bayerite. Its main properties are shown in Figure 1 and Figure 7 .

[0089] Comparative Example 1

[0090] Take the mother liquor and seed liquor of the alumina sintering process, mix and prepare, αk2.0, N k 93g / l, after filtering, cool to 40℃, take an appropriate amount and pour it into a beaker with a carbon separation device, start stirring at a speed of 600r / min, and then introduce 37% CO2 (0.4m 3 / h) to decompose carbon, and the end point N K Controlled at 10g / L, Bayerite slurry is obtained, filtered to obtain filter cake, and washed and dried to obtain Bayerite. Its main properties are shown in Figure 1 and Figure 8 .

[0091] The difference between Comparative Example 1 and Example 5 is that: in Comparative Example 1, no crystallization aid is added, and the prepared product is pure phase Bayerite. The difference from Example 5 is the particle size and morphology of the product. Its particle size is uncontrollable and coarse, and its morphology is a dense structure, which cannot be used in the catalyst industry.

[0092] Comparative Example 2

[0093] Take the mother liquor and seed liquor of the alumina sintering process, mix and prepare, αk 2.0, N k 93g / l, after filtering, cool to 75℃, take an appropriate amount and pour it into a beaker with a carbon separation device, start stirring at a speed of 600r / min, add 0.1% crystallization aid, stir for 5min, and then pass 37% CO2 (0.4m 3 / h) to decompose carbon, and the end point N K Controlled at 10g / L, Bayerite slurry is obtained, filtered to obtain filter cake, and washed and dried to obtain Bayerite. Its main properties are shown in Figure 1 and Fig. 9 .

[0094] The difference between Comparative Example 2 and Example 5 is that the reaction temperature is increased in Comparative Example 2, and α-phase aluminum hydroxide appears in the prepared product, which cannot be used in the catalyst industry.

[0095] Table 1 Bayerite index results obtained in the examples and comparative examples

[0096]

[0097] The above experimental results show that Bayerite can be prepared under different conditions. Considering the actual situation and operability on site, the laboratory selected the process conditions of Example 3 to carry out industrial expansion experiments, and took 3 samples from different batches for verification. The experimental results are shown in Tables 2 and Figure 10 to Figure 15 .

[0098] Table 2 Index results of Bayerite samples obtained from the industrial scale-up experiment of Example 3

[0099]

[0100] In addition, one or more technical solutions in the embodiments of the present invention have at least the following technical effects or advantages:

[0101] In the embodiment of the present invention, by controlling the reaction activity, stabilizing the reaction temperature, regulating the product morphology, and controlling the reaction endpoint N K Etc. to ensure the feasibility of the process, high product purity, and uniform particle size distribution.

[0102] In the embodiment of the present invention, the by-product sodium carbonate is used as a raw material for the sintering process for production, which is green, environmentally friendly, pollution-free, and meets the requirements of national environmental protection policies.

[0103] In the embodiment of the present invention, the high α K The difficulty of preparing Bayerite with sodium aluminate solution is that the impurity content is high. The prepared product has low cost, high economic added value, and is high α K The comprehensive utilization of sodium aluminate solution provides a new approach.

[0104] 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 Bayerite based on high αk sodium aluminate solution, characterized in that: The method comprises: adding a morphology control agent to a sodium aluminate solution having a set αk to obtain a mixed solution; A mixed gas having a set CO2 volume concentration is introduced into the mixed liquid to perform a carbonation reaction under set conditions, and the N K Reaching the setting N K concentration to obtain a Bayerite slurry; and The Bayerite slurry is subjected to solid-liquid separation to obtain Bayerite.

2. The method according to claim 1, characterized in that The setting αk is 2.0-4.

5.

3. The method according to claim 1, characterized in that The N in the sodium aluminate solution k The concentration is 50g / L~130g / L.

4. The method according to claim 3, characterized in that The sodium aluminate solution is one or both of the mother liquor of the sintering process and the seed mother liquor.

5. The method according to claim 1, characterized in that The mass of the morphology control agent is 1‰ to 1% of the total volume of the sodium aluminate solution.

6. The method according to claim 5, characterized in that The morphology control agent is an organic crystallization aid, which includes the following chemical components by weight: 20 to 30 parts of sodium unsaturated fatty acid, 15 to 25 parts of polyethylene glycol dioleate, 10 to 15 parts of sodium secondary alkyl sulfonate, 5 to 10 parts of Span 80, 10 to 20 parts of triethanolamine, and 1 to 3 parts of polyether defoaming agent.

7. The method according to claim 1, characterized in that The flow rate of the mixed gas is 0.3m 3 / h~600m 3 / min, and the set CO2 volume concentration is 35% to 100%.

8. The method according to claim 1, characterized in that The temperature of the carbonation reaction is 30° C. to 60° C., and the time of the carbonation reaction is 15 min to 45 min.

9. The method according to claim 1, characterized in that: The setting N K The concentration is 8g / L~15g / L.

10. The method according to claim 1, characterized in that The Bayerite satisfies at least one of the following properties: a particle size D50 of 15 μm to 25 μm, and a purity of ≥97.5%.

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