A method for purifying sodium aluminate solution in a bayer process for producing alumina

Abstract

The application relates to a purification method of sodium aluminate solution in a Bayer process for producing alumina, and the method comprises the following steps: obtaining sodium aluminate evaporation mother liquor; and performing staged purification on the sodium aluminate evaporation mother liquor under different temperature conditions. The evaporation mother liquor of the sodium aluminate solution is purified in stages under different temperature conditions to respectively precipitate fluorine salt, oxalate and vanadate, so that a good purification effect of the sodium aluminate solution is achieved, and meanwhile, the fluorine salt and the vanadate with higher purity can be obtained, which is more beneficial to the further recycling of the two elements. After the sodium fluoride is precipitated, the content of the mother liquor F is reduced to 0.5g / l-1g / l, and the purity of the obtained NaF is greater than 95%; after the sodium oxalate is precipitated, the content of the mother liquor C2O4 is reduced to 0.6g / l-1g / l; and after the sodium vanadate is precipitated, the content of the mother liquor V is reduced to 50ppm-100ppm, and the content of the obtained vanadium salt V2O5 reaches 25%-30%.

Description

Technical Field

[0001] This application relates to the field of Bayer process alumina production technology, and more particularly to a method for purifying sodium aluminate solution during the Bayer process alumina production. Background Technology

[0002] During the Bayer process, impurities such as fluorine, oxalate, and vanadium enter the process when bauxite is leached, which can harm production. For example, fluorine can cause scaling on the evaporator; oxalate can cause the product to become finer, affecting product quality and even causing the Bayer process to malfunction; vanadium can affect process efficiency and can also enter the product, affecting product quality.

[0003] After the Bayer process mother liquor is cooled, impurities such as fluoride, oxalate, and vanadate will precipitate under certain controlled conditions. Currently, cooling the mother liquor is used to remove oxalate or remove and recover vanadium, but the co-precipitation of fluoride, oxalate, and vanadate is unavoidable, which brings difficulties to the further processing and purification of the precipitated salts. Summary of the Invention

[0004] This application provides a method for purifying sodium aluminate solution in the Bayer process for alumina production, in order to solve the technical problem of poor purification effect of sodium aluminate solution in the existing Bayer process for alumina production.

[0005] In a first aspect, this application provides a method for purifying sodium aluminate solution during the Bayer process for alumina production, the method comprising:

[0006] Sodium aluminate evaporation mother liquor was obtained;

[0007] The sodium aluminate evaporation mother liquor was purified in stages under different temperature conditions.

[0008] Optionally, the step of purifying the sodium aluminate evaporation mother liquor in stages under different temperature conditions includes:

[0009] Under a first preset temperature, sodium fluoride seeds are added to the sodium aluminate evaporation mother liquor to precipitate sodium fluoride and obtain the first mother liquor.

[0010] Under a second preset temperature, oxalate seeds are added to the first mother liquor to precipitate sodium oxalate and obtain a second mother liquor.

[0011] Under the condition of a third preset temperature, sodium vanadate is precipitated from the second mother liquor to obtain a third mother liquor.

[0012] Optionally, the first preset temperature is 70℃~80℃.

[0013] Optionally, the sodium fluoride precipitation time is 3h to 6h.

[0014] Optionally, the amount of sodium fluoride seeds added is 10 g / L to 50 g / L.

[0015] Optionally, the second preset temperature is 45℃~60℃.

[0016] Optionally, the sodium oxalate precipitation time is 2h to 5h.

[0017] Optionally, the amount of oxalate seeds added is 40 g / L to 100 g / L.

[0018] Optionally, the third preset temperature is 20℃~35℃.

[0019] Optionally, the sodium vanadate precipitation time is 2h to 5h.

[0020] The technical solutions provided in this application have the following advantages compared with the prior art:

[0021] The purification method for sodium aluminate solution in the Bayer process for alumina production provided in this application embodiment involves purifying the evaporation mother liquor of the sodium aluminate solution in stages under different temperature conditions to precipitate fluoride, oxalate, and vanadate separately, achieving a good purification effect on the sodium aluminate solution. This allows for the simultaneous purification of the solution and the acquisition of fluoride and vanadate with higher purity, which is more conducive to the further recovery and utilization of these two elements. Using this purification method, after sodium fluoride precipitation, the F content in the mother liquor decreases to 0.5 g / L to 1 g / L, and the purity of the obtained NaF is greater than 95%; after sodium oxalate precipitation, the C2O4 content in the mother liquor decreases to 0.6 g / L to 1 g / L; after sodium vanadate precipitation, the V content in the mother liquor decreases to 50 ppm to 100 ppm, and the V2O5 content of the obtained vanadate reaches 25% to 30%. Attached Figure Description

[0022] 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.

[0023] 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.

[0024] Figure 1 This application provides a method for purifying sodium aluminate solution during the Bayer process for alumina production. Detailed Implementation

[0025] 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.

[0026] 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.

[0027] 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.

[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] Firstly, this application provides a method for purifying sodium aluminate solution during the Bayer process for alumina production. Please refer to [link to relevant documentation]. Figure 1 The method includes:

[0030] S1. Obtain the mother liquor from the evaporation of sodium aluminate;

[0031] In this embodiment, the chemical composition of the sodium aluminate evaporation mother liquor includes: N k The content of (caustic alkali concentration) is 180g / l to 250g / l, the content of F is 1.5g / l to 2.5g / l, the content of C2O4 is 1.4g / l to 2.8g / l, and the content of V is 150ppm to 650ppm.

[0032] S2. The sodium aluminate evaporation mother liquor is purified in stages under different temperature conditions.

[0033] In some embodiments, the staged purification of the sodium aluminate evaporation mother liquor under different temperature conditions includes:

[0034] S2a. Under the condition of the first preset temperature, sodium fluoride seeds are added to the sodium aluminate evaporation mother liquor to precipitate sodium fluoride and obtain the first mother liquor.

[0035] In some embodiments, the first preset temperature is 70°C to 80°C.

[0036] In this embodiment, the "first preset temperature" represents the precipitation temperature of sodium fluoride. Controlling the precipitation temperature of sodium fluoride within the aforementioned temperature range results in the best precipitation effect, with a large and concentrated precipitation of sodium fluoride salt. If the precipitation temperature of sodium fluoride is too high or too low, it will, to some extent, lead to a poorer precipitation effect, thus failing to achieve a good purification effect. Too low a temperature may result in the precipitation of mixed salts, reducing the purity of the salt. Specifically, the precipitation temperature of sodium fluoride can be 70℃, 72℃, 74℃, 76℃, 78℃, 80℃, etc.

[0037] In some embodiments, the sodium fluoride is precipitated over a period of 3 to 6 hours.

[0038] In this embodiment, the precipitation time of sodium fluoride is controlled to achieve the best precipitation effect, resulting in a large and concentrated precipitation of sodium fluoride salt. If the precipitation time is too short, the precipitation effect will be poor to some extent, resulting in a low precipitation rate and thus failing to achieve a good purification effect; if the precipitation time is too long, the precipitation effect of sodium fluoride will have reached saturation to some extent. Specifically, the precipitation time of sodium fluoride can be 3h, 4h, 5h, 6h, etc.

[0039] In some embodiments, the amount of sodium fluoride seeds added is 10 g / L to 50 g / L.

[0040] In this embodiment, the amount of sodium fluoride seed added is controlled to achieve the best precipitation effect, resulting in a large and concentrated precipitation of sodium fluoride salt. If the amount of sodium fluoride seed added is too small, the precipitation effect will be poor to some extent, resulting in a low precipitation rate and thus failing to achieve a good purification effect; if the amount of sodium fluoride seed added is too large, the precipitation effect of sodium fluoride will reach saturation to some extent. Specifically, the amount of sodium fluoride seed added can be 10 g / L, 15 g / L, 20 g / L, 25 g / L, 30 g / L, 35 g / L, 40 g / L, 45 g / L, 50 g / L, etc.

[0041] After the precipitation of sodium fluoride S2a, the F content in the mother liquor decreased to 0.5 g / l to 1 g / l, and the purity of the obtained NaF was greater than 95%.

[0042] S2b. Under the condition of the second preset temperature, oxalate seeds are added to the first mother liquor to precipitate sodium oxalate and obtain the second mother liquor.

[0043] In some embodiments, the second preset temperature is 45°C to 60°C.

[0044] In this embodiment, the "second preset temperature" represents the temperature at which sodium oxalate precipitates. The precipitation effect of sodium oxalate is optimal within the aforementioned temperature range, resulting in a large and concentrated precipitation of sodium oxalate salt. If the precipitation temperature is too high or too low, the precipitation effect will be reduced to some extent, thus failing to achieve a good purification effect. If the temperature is too low, mixed salts may precipitate, reducing the purity of the salt. Specifically, the precipitation temperature of sodium oxalate can be 45℃, 50℃, 55℃, 60℃, etc.

[0045] In some embodiments, the sodium oxalate precipitates over a period of 2 to 5 hours.

[0046] In this embodiment, the precipitation time of sodium oxalate is controlled to achieve the best precipitation effect, resulting in a large and concentrated precipitation of sodium oxalate salt. If the precipitation time is too short, the precipitation effect will be poor to some extent, resulting in a low precipitation rate and thus failing to achieve a good purification effect; if the precipitation time is too long, the precipitation effect of sodium oxalate will have reached saturation to some extent. Specifically, the precipitation time of sodium oxalate can be 2 hours, 3 hours, 4 hours, 5 hours, etc.

[0047] In some embodiments, the amount of oxalate seeds added is 40 g / L to 100 g / L.

[0048] In this embodiment, the amount of oxalate seeds added is controlled to maximize the precipitation effect of sodium oxalate, resulting in a large and concentrated precipitation of sodium oxalate salt. If the amount of oxalate seeds added is too small, the precipitation effect of sodium oxalate will be poor to some extent, resulting in a low precipitation rate and thus failing to achieve a good purification effect; conversely, if the amount of oxalate seeds added is too small, the precipitation effect of sodium oxalate may have reached saturation to some extent. Specifically, the amount of oxalate seeds added can be 40 g / L, 45 g / L, 50 g / L, 55 g / L, 60 g / L, 65 g / L, 70 g / L, 75 g / L, 80 g / L, 85 g / L, 90 g / L, 95 g / L, 100 g / L, etc.

[0049] After the precipitation of sodium oxalate from S2b, the C2O4 content in the mother liquor decreased to 0.6 g / L to 1 g / L.

[0050] S2c. Under the condition of a third preset temperature, sodium vanadate is precipitated from the second mother liquor to obtain a third mother liquor.

[0051] In some embodiments, the third preset temperature is 20°C to 35°C.

[0052] In this embodiment, the "third preset temperature" represents the temperature at which sodium vanadate precipitates. Controlling the precipitation temperature within the aforementioned temperature range results in the best precipitation effect, with a large and concentrated precipitation of sodium vanadate salt. If the precipitation temperature is too high or too low, the precipitation effect will be reduced to some extent, thus failing to achieve a good purification effect. Specifically, the precipitation temperature of sodium vanadate can be 20℃, 25℃, 30℃, 35℃, etc.

[0053] In some embodiments, the sodium vanadate precipitates over a period of 2 to 5 hours.

[0054] In this embodiment, the precipitation time of sodium vanadate is controlled to achieve the best precipitation effect, resulting in a large and concentrated precipitation of sodium vanadate salt. If the precipitation time is too short, the precipitation effect will be poor to some extent, resulting in a low precipitation rate and thus failing to achieve a good purification effect; if the precipitation time is too long, the precipitation effect of sodium vanadate will have reached saturation to some extent. Specifically, the precipitation time of sodium vanadate can be 2 hours, 3 hours, 4 hours, 5 hours, etc.

[0055] After sodium vanadate precipitates in the S2c step above, the V content of the mother liquor decreases to 50ppm to 100ppm, and the vanadium salt V2O5 content obtained reaches 25% to 30%.

[0056] 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.

[0057] This application provides a method for purifying sodium aluminate solution during the Bayer process for alumina production, the method comprising:

[0058] S11. Obtain the mother liquor from the evaporation of sodium aluminate;

[0059] S21. The sodium aluminate evaporation mother liquor is purified in stages under different temperature conditions. For specific process steps, please refer to Examples 1-3 below.

[0060] Example 1

[0061] Bauxite is leached using the Bayer process to obtain a refined sodium aluminate solution (refined solution). The chemical composition of this solution includes: N... k The content of nitrogen was 145 g / L, the content of phosphorus was 1.52 g / L, the content of carbon dioxide (C₂O₄) was 1.45 g / L, and the content of sulfur dioxide (V) was 360 ppm. Semen was decomposed by adding seed crystals, and the mother liquor was evaporated. The chemical composition of the evaporated mother liquor included: N... k The content of is 196 g / l, the content of F is 2.05 g / l, the content of C2O4 is 1.96 g / l, and the content of V is 486 ppm;

[0062] The mother liquor was cooled to 75°C, and 30 g / L of circulating NaF seeds was added. The mixture was kept warm and stirred for 4 hours, then filtered. The filtrate contained 0.83 g / L of F, yielding NaF with a purity of 96.4%.

[0063] The filtrate was cooled to 50℃, 60g / l of oxalate seeds was added, and the mixture was kept warm for 5 hours. After filtration, the C2O4 content of the filtrate was 0.79g / l.

[0064] The filtrate was further cooled to 25°C, kept warm and stirred for 3 hours, and then filtered. The V content of the filtrate was 62 ppm, and the vanadium salt obtained had a V2O5 content of 27.6%.

[0065] Example 2

[0066] Bauxite is leached using the Bayer process to obtain a refined sodium aluminate solution (refined solution). The chemical composition of this solution includes: N... k The content of nitrogen was 145 g / L, the content of phosphorus was 1.52 g / L, the content of carbon dioxide (C₂O₄) was 1.45 g / L, and the content of sulfur dioxide (V) was 360 ppm. Semen was decomposed by adding seed crystals, and the mother liquor was evaporated. The chemical composition of the evaporated mother liquor included: N... kThe content of is 196 g / l, the content of F is 2.05 g / l, the content of C2O4 is 1.96 g / l, and the content of V is 486 ppm;

[0067] The mother liquor was cooled to 70°C, and 10 g / L of circulating NaF seeds was added. The mixture was kept warm and stirred for 3 hours, then filtered. The filtrate contained 0.78 g / L of F, yielding NaF with a purity of 96.8%.

[0068] The filtrate was cooled to 45℃, 40g / l of oxalate seeds was added, the mixture was kept warm for 4 hours, and then filtered. The C2O4 content of the filtrate was 0.75g / l.

[0069] The filtrate was further cooled to 20°C, kept warm and stirred for 2 hours, and then filtered. The V content of the filtrate was 55 ppm, and the vanadium salt obtained had a V2O5 content of 28.1%.

[0070] Example 3

[0071] Bauxite is leached using the Bayer process to obtain a refined sodium aluminate solution (refined solution). The chemical composition of this solution includes: N... k The content of nitrogen was 145 g / L, the content of phosphorus was 1.52 g / L, the content of carbon dioxide (C₂O₄) was 1.45 g / L, and the content of sulfur dioxide (V) was 360 ppm. Semen was decomposed by adding seed crystals, and the mother liquor was evaporated. The chemical composition of the evaporated mother liquor included: N... k The content of is 196 g / l, the content of F is 2.05 g / l, the content of C2O4 is 1.96 g / l, and the content of V is 486 ppm;

[0072] The mother liquor was evaporated and cooled to 80℃. 50 g / L of circulating NaF seeds was added, and the mixture was kept warm and stirred for 6 hours. After filtration, the F content of the filtrate was 0.75 g / L, and the NaF purity was 97.1%.

[0073] The filtrate was cooled to 60℃, 100g / l of oxalate seeds was added, and the mixture was kept warm for 6 hours. After filtration, the C2O4 content of the filtrate was 0.87g / l.

[0074] The filtrate was further cooled to 35°C, kept warm and stirred for 5 hours, and then filtered. The V content of the filtrate was 65 ppm, and the vanadium salt obtained had a V2O5 content of 27.8%.

[0075] Comparative Example 1

[0076] Bauxite is leached using the Bayer process to obtain a refined sodium aluminate solution (refined solution). The chemical composition of this solution includes: N... k The content of nitrogen was 145 g / L, the content of phosphorus was 1.52 g / L, the content of carbon dioxide (C₂O₄) was 1.45 g / L, and the content of sulfur dioxide (V) was 360 ppm. Semen was decomposed by adding seed crystals, and the mother liquor was evaporated. The chemical composition of the evaporated mother liquor included: N... kThe content of is 196 g / l, the content of F is 2.05 g / l, the content of C2O4 is 1.96 g / l, and the content of V is 486 ppm.

[0077] The mother liquor was cooled to 30°C, and 50 g / L of a mixed seed containing sodium fluoride and sodium oxalate was added. The mixture was kept warm and stirred for 5 hours, then filtered. The solution was purified, with the filtrate containing 0.85 g / L of F, 0.81 g / L of C2O4, and 65 ppm of V. However, the purity of the mixed salt was very low, with a NaF content of 5.2% and a V2O5 content of 1.9%, making it difficult to recycle.

[0078] In summary, the purification method for sodium aluminate solution in the Bayer process for alumina production provided in this application purifies the evaporation mother liquor of sodium aluminate solution in stages under different temperature conditions to precipitate fluoride, oxalate, and vanadate respectively, achieving a good purification effect on the sodium aluminate solution. This allows for the simultaneous purification of the solution and the acquisition of fluoride and vanadate with higher purity, which is more conducive to the further recovery and utilization of these two elements. Specifically, after sodium fluoride precipitation, the F content in the mother liquor decreases to 0.5 g / L to 1 g / L, and the purity of the obtained NaF is greater than 95%; after sodium oxalate precipitation, the C2O4 content in the mother liquor decreases to 0.6 g / L to 1 g / L; after sodium vanadate precipitation, the V content in the mother liquor decreases to 50 ppm to 100 ppm, and the V2O5 content of the obtained vanadate reaches 25% to 30%. In contrast, Comparative Example 1 did not employ the staged purification under different temperature conditions described in this application, resulting in poor purification effect and low salt purity.

[0079] 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 purifying a sodium aluminate solution in a Bayer process for producing alumina, characterized by, The method comprises: The sodium aluminate evaporation mother liquor is obtained, and the chemical composition of the sodium aluminate evaporation mother liquor comprises: N k The content of F is 1.5 g / l~2.5 g / l, the content of C2O4 is 1.4 g / l~2.8 g / l, and the content of V is 150 ppm~650 ppm. At 70-80 DEG C, 10-50 g / l of sodium fluoride seed is added into the sodium aluminate evaporation mother liquor to precipitate sodium fluoride from the sodium aluminate evaporation mother liquor, so that a first mother liquor is obtained, the purity of NaF is greater than 95%, and the precipitation time of sodium fluoride is 3-6 h; At 45-60 DEG C, 40-100 g / l of oxalate seed is added into the first mother liquor to precipitate sodium oxalate from the first mother liquor, so that a second mother liquor is obtained, the C2O4 content in the second mother liquor is 0.6-1 g / l, and the precipitation time of sodium oxalate is 2-5 h; At 20-35 DEG C, sodium vanadate is precipitated from the second mother liquor, so that a third mother liquor is obtained, the V content in the third mother liquor is 50-100 ppm, and the precipitation time of sodium vanadate is 2-5 h.

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