Preparation method of high-stability sodium aluminate slurry

Abstract

This invention discloses a method for preparing a highly stable sodium aluminate slurry, comprising the following steps: S1: Selecting sodium aluminate slurry for preparation during the Bayer process of alumina production; S2: Filtering the sodium aluminate slurry obtained in S1 to remove suspended solids and precipitates, then placing it in a clean, dry container and cooling it to room temperature as the preparation solution; S3: Subjecting the preparation solution obtained in S2 to caustic alkali N2. K Total alkali N T Analysis and detection of alumina (AO) content, and calculation of R P If R P If the concentration is greater than 0.5, add solid sodium hydroxide and stir continuously until the solid sodium hydroxide is completely dissolved, so that the R of the solution... P The solution is in the range of 0.45-0.5; S4: Add 120-130 g / L of solid tartaric acid to S3, stir thoroughly to dissolve, and let stand to obtain a highly stable sodium aluminate slurry. The sodium aluminate solution prepared by this invention can be stored for more than one year, exhibiting long storage time, high stability, and outstanding technical effects.

Description

Technical Field

[0001] This invention relates to the field of chemical technology, specifically to a method for preparing a highly stable sodium aluminate slurry. Background Technology

[0002] Sodium aluminate slurry is a material with poor stability. Currently, there is no industry-wide recognized quality control sample to guide the analysis of sodium aluminate slurry in the alumina process. Internal quality control samples prepared by conventional methods are not stable enough and have a short shelf life; deviations or errors in the analytical system cannot be detected, making it impossible to accurately guide production. Therefore, preparing highly stable sodium aluminate slurry is of great significance for quality control and production guidance. Summary of the Invention

[0003] This invention overcomes the technical problem of poor stability of sodium aluminate slurry in the prior art and provides a method for preparing highly stable sodium aluminate slurry.

[0004] A method for preparing a highly stable sodium aluminate slurry, comprising the following steps:

[0005] S1: Sodium aluminate slurry is selected for preparation in the Bayer process of alumina production;

[0006] S2: After filtering the sodium aluminate slurry obtained from S1 to remove suspended solids and precipitates, place it in a clean and dry container and cool it to room temperature to use as the preparation solution.

[0007] S3: The solution obtained in S2 is subjected to caustic soda N K Total alkali N T Analysis and detection of alumina (AO) content, and calculation of R P If R P If the concentration is greater than 0.5, add solid sodium hydroxide and stir continuously until the solid sodium hydroxide is completely dissolved, so that the R of the solution... P It falls within the range of 0.45-0.5;

[0008] S4: Add 120-130 g / L of solid tartaric acid to S3, stir thoroughly to dissolve, and let stand to obtain the highly stable sodium aluminate slurry.

[0009] In this invention, the purpose of adding sodium hydroxide to S3 is to increase the OH content in the solution. － The concentration of ions is adjusted to ensure that aluminum ions do not precipitate out of the solution, thereby improving the stability of the solution.

[0010] Furthermore, the purity of the solid sodium hydroxide is analytical grade or higher.

[0011] Furthermore, the purity of the solid pharmaceutical agent tartaric acid is analytical grade or higher.

[0012] Furthermore, in S1, the sodium aluminate slurry is selected from the seed mother liquor in the decomposition process of the Bayer process for alumina production.

[0013] Compared with the prior art, the present invention has the following advantages:

[0014] This invention first adjusts the alkalinity using solid sodium hydroxide and then adds an appropriate amount of solid tartaric acid as a stabilizer. The resulting sodium aluminate solution can be stored for more than a year, exhibiting high stability and long shelf life, which can accurately guide production. The raw materials for the highly stable sodium aluminate slurry prepared by this invention are readily available, and the preparation process is simple, facilitating its promotion and application. Attached image description:

[0015] Figure 1 A process flow diagram for the Bayer process of alumina production; Detailed Implementation

[0016] The present invention will be further described below with reference to embodiments and experiments.

[0017] Example 1

[0018] A method for preparing a highly stable sodium aluminate slurry, comprising the following steps:

[0019] S1: In the Bayer process of alumina production, 8L of sodium aluminate slurry is selected for preparation; specifically, it is selected from the seed mother liquor in the decomposition step of the Bayer process; see the Bayer process flow chart. Figure 1 This is existing technology;

[0020] S2: After filtering the sodium aluminate slurry obtained from S1 with degreased cotton to remove suspended solids and precipitates, place it in a clean and dry container and cool it to room temperature to use as the preparation solution.

[0021] S3: The solution obtained in S2 is subjected to caustic soda N K Total alkali N T Analysis and detection of alumina (AO) content, and calculation of R P If R P If the concentration is greater than 0.5, add analytical grade solid sodium hydroxide and stir continuously until the solid sodium hydroxide is completely dissolved. Then, take another sample to determine the nitrogen content. k N T AO, add analytical grade solid sodium hydroxide and dissolve it, repeat several times, to make the solution R P The concentration is in the range of 0.45-0.5; adding sodium hydroxide can increase the OH content in the solution. － The concentration of ions is adjusted to ensure that aluminum ions do not precipitate out of the solution, thereby improving the stability of the solution.

[0022] S4: Add 130 g / L of analytical grade solid tartaric acid to S3, stir thoroughly to dissolve, and let stand to obtain the highly stable sodium aluminate slurry.

[0023] Example 2

[0024] A method for preparing a highly stable sodium aluminate slurry, comprising the following steps:

[0025] S1: In the Bayer process of alumina production, 8L of sodium aluminate slurry is selected for preparation; specifically, it is selected from the seed mother liquor in the decomposition step of the Bayer process; see the Bayer process flow chart. Figure 1 This is existing technology;

[0026] S2: After filtering the sodium aluminate slurry obtained from S1 with degreased cotton to remove suspended solids and precipitates, place it in a clean and dry container and cool it to room temperature to use as the preparation solution.

[0027] S3: The solution obtained in S2 is subjected to caustic soda N K Total alkali N T Analysis and detection of alumina (AO) content, and calculation of R P If R P If the concentration is greater than 0.5, add analytical grade solid sodium hydroxide and stir continuously until the solid sodium hydroxide is completely dissolved. Then, take another sample to determine the nitrogen content. k N T AO, add analytical grade solid sodium hydroxide and dissolve it, repeat several times, to make the solution R P The concentration is in the range of 0.45-0.5; adding sodium hydroxide can increase the OH content in the solution. － The concentration of ions is adjusted to ensure that aluminum ions do not precipitate out of the solution, thereby improving the stability of the solution.

[0028] S4: Add 120 g / L of analytical grade solid tartaric acid to S3, stir thoroughly to dissolve, and let stand to obtain the highly stable sodium aluminate slurry.

[0029] Example 3

[0030] A method for preparing a highly stable sodium aluminate slurry, comprising the following steps:

[0031] S1: In the Bayer process of alumina production, 8L of sodium aluminate slurry is selected for preparation; specifically, it is selected from the seed mother liquor in the decomposition step of the Bayer process; see the Bayer process flow chart. Figure 1 This is existing technology;

[0032] S2: After filtering the sodium aluminate slurry obtained from S1 with degreased cotton to remove suspended solids and precipitates, place it in a clean and dry container and cool it to room temperature to use as the preparation solution.

[0033] S3: The solution obtained in S2 is subjected to caustic soda N K Total alkali N T Analysis and detection of alumina (AO) content, and calculation of R P If R P If the concentration is greater than 0.5, add analytical grade solid sodium hydroxide and stir continuously until the solid sodium hydroxide is completely dissolved. Then, take another sample to determine the nitrogen content. k N T AO, add analytical grade solid sodium hydroxide and dissolve it, repeat several times, to make the solution R P The concentration is in the range of 0.45-0.5; adding sodium hydroxide can increase the OH content in the solution. － The concentration of ions is adjusted to ensure that aluminum ions do not precipitate out of the solution, thereby improving the stability of the solution.

[0034] S4: Add 125 g / L of analytical grade solid tartaric acid to S3, stir thoroughly to dissolve, and let stand to obtain the highly stable sodium aluminate slurry.

[0035] Control group 1

[0036] A method for preparing sodium aluminate slurry, comprising the following steps:

[0037] S1: In the Bayer process of alumina production, 8L of sodium aluminate slurry is selected for preparation; specifically, it is selected from the seed mother liquor in the decomposition step of the Bayer process; see the Bayer process flow chart. Figure 1 This is existing technology;

[0038] S2: After filtering the sodium aluminate slurry obtained from S1 with degreased cotton to remove suspended solids and precipitates, place it in a clean and dry container and cool it to room temperature to use as the preparation solution.

[0039] S3: The caustic alkali (NK), total alkali (NT), and alumina (AO) content of the prepared solution obtained in S2 were analyzed and detected, and R was calculated. P If R P If the concentration is greater than 0.5, add 5 mol / L sodium hydroxide solution and take another sample to determine N. k N T AO, repeat several times, to make the solution R P It falls within the range of 0.45-0.5;

[0040] S4: Add 25wt% sodium tartrate solution to S3 at a volume ratio of 1:1, stir thoroughly, and let stand to obtain the highly stable sodium aluminate slurry.

[0041] Sodium aluminate slurry before and after preparation of Examples 1-3 and Control Group 1 was subjected to alumina (AO) and caustic soda (N) treatment.K ), total alkali (N T ) and the mass ratio of alumina to caustic alkali (R) P The sodium aluminate slurries prepared in Examples 1-3 and Control Group 1 were tested for various indicators and stored in sealed containers at room temperature away from light. The results are as follows:

[0042] The changes in various indicators before and after preparation in Example 1 are shown in Table 1 below, and the effect of storage time on solution stability is shown in Table 2:

[0043] Table 1

[0044] Sodium aluminate slurry AO(g / l) <![CDATA[N K (g / l)]]> <![CDATA[N T (g / l)]]> <![CDATA[R P ]]> Before preparation 79.4 152.0 174.9 0.52 After preparation 71.4 150.0 165.4 0.48

[0045] Table 2

[0046]

[0047]

[0048] The changes in various indicators before and after preparation in Example 2 are shown in Table 3 below, and the effect of storage time on solution stability is shown in Table 4:

[0049] Table 3

[0050] Sodium aluminate slurry AO(g / l) <![CDATA[N K (g / l)]]> <![CDATA[N T (g / l)]]> <![CDATA[R P ]]> Before preparation 79.4 152.0 174.9 0.52 After preparation 71.4 149.8 165.2 0.48

[0051] Table 4

[0052] Sodium aluminate slurry AO(g / l) <![CDATA[N K (g / l)]]> <![CDATA[N T (g / l)]]> <![CDATA[R P ]]> Leave for 1 day 71.1 149.0 164.6 0.48 Store for 1 month 71.2 149.8 165.9 0.48 Stored for 3 months 71.4 150.0 165.1 0.48 Stored for 6 months 71.5 149.0 165.2 0.48 Stored for 7 months 71.4 149.8 164.8 0.48 Stored for 8 months 71.0 149.6 166.0 0.48 Stored for 10 months 71.2 149.6 166.5 0.48 Stored for 12 months 71.5 150.2 165.8 0.48 Stored for 15 months 71.4 150.0 165.4 0.48 Allowable difference 1.0 2.5 2.0 /

[0053] The changes in various indicators before and after preparation in Example 3 are shown in Table 5 below, and the effect of storage time on solution stability is shown in Table 6.

[0054] Table 5

[0055] Sodium aluminate slurry AO(g / l) <![CDATA[N K (g / l)]]> <![CDATA[N T (g / l)]]> <![CDATA[R P ]]> Before preparation 79.4 152.0 174.9 0.52 After preparation 71.1 149.0 164.6 0.48

[0056] Table 6

[0057]

[0058]

[0059] The changes in various indicators of control group 1 before and after preparation are shown in Table 7 below, and the effect of storage time on solution stability is shown in Table 8.

[0060] Table 7

[0061] Sodium aluminate slurry AO(g / l) <![CDATA[N K (g / l)]]> <![CDATA[N T (g / l)]]> <![CDATA[R P ]]> Before preparation 79.4 152.0 174.9 0.52 After preparation 48.2 102.0 103.0 0.48

[0062] Table 8

[0063] Sodium aluminate slurry AO(g / l) <![CDATA[N K (g / l)]]> <![CDATA[N T (g / l)]]> <![CDATA[R P ]]> Leave for 1 day 48.2 102.0 103.0 0.48 Store for 1 month 48.5 103.8 104.5 0.47 Stored for 3 months 47.8 102.1 102.9 0.47 Stored for 6 months 47.6 105.0 106.2 0.45 Stored for 7 months 49.5 105.1 105.8 0.47 Allowable difference 1.0 2.5 2.0 /

[0064] A comparison of Tables 1, 3, 5, and 7 shows that even if R... P All values ​​were uniformly adjusted to 0.48. However, in control group 1, the addition of aqueous solution to the solution led to a significant decrease in the total alkali, caustic soda, and alumina content of the sodium aluminate slurry, resulting in large variations and significant deviations from the actual slurry content. In contrast, the content of each analytical indicator in Examples 1 to 3 fluctuated less and was closer to the results of routine process analysis samples (i.e., also close to the results of total alkali, caustic soda, and alumina content in sodium aluminate before preparation), indicating that the results were more representative.

[0065] A comparison of Tables 2, 4, 6, and 8 shows that in Table 8 (Control Group 1), after approximately 6 months of storage, crystal precipitation occurs in the sodium aluminate slurry, leading to significant variations in the content of various indicators, exceeding the allowable tolerance range, necessitating re-filtration and re-calibration. In contrast, Tables 2-4 (Examples 1-3) show no crystal precipitation even after prolonged storage, with all indicator contents remaining within the allowable tolerance range, and a stable period exceeding one year. This indicates good stability of the sodium aluminate slurry, demonstrating the outstanding technical effectiveness of the method of this invention.

[0066] The analysis and detection of the total alkali (NT) and alumina (AO) content involved in Examples 1 to 3 and Control Group 1 of this invention were carried out according to the following methods:

[0067] Analysis of total alkali and alumina

[0068] 1 range

[0069] This procedure applies to the volumetric determination of total alkali and alumina in sodium aluminate solution. The determination range is: total alkali 5 g / L to 400 g / L, and alumina 5 g / L to 350 g / L.

[0070] This procedure specifies the method summary, reagents, samples, analytical procedures, calculation of analytical results, precautions, and permissible differences.

[0071] 2. Method Summary

[0072] Alumina was determined by EDTA complexometric back titration, and total alkali was determined by acid-base back titration. Specifically, excess EDTA and hydrochloric acid were added to the sample solution, and the reaction was heated to completion. Then, excess hydrochloric acid was back titrated with sodium hydroxide to determine total alkali. Alumina was determined by back titration with zinc acetate at pH 5.2–5.7.

[0073] However, excess EDTA dissociates into a hydrogen ion when phenolphthalein changes color, consuming an equivalent amount of base. Therefore, this should be corrected when calculating the total base. The reaction is as follows:

[0074] NaAl(OH)4+Na2H2Y+2HCl (pH=5)→NaAlY+2NaCl+4H2O

[0075] NaOH + HCl → NaCl + H₂O

[0076] Na₂CO₃ + 2HCl → 2NaCl + H₂O + CO₂

[0077] The reaction when back-titrated with NaOH:

[0078] HCl + NaOH → NaCl + H₂O

[0079] NaAlY + NaOH → Na2Al(OH)Y

[0080] Na₂H₂Y + NaOH → NaAlY + H₂O

[0081] The reaction when Zn(Ac)2 is back-dropped:

[0082] Zn 2+ +H6XO (yellow) → ZnXO 4- (Purple) + 6H +

[0083] Note: H6XO represents xylenol orange.

[0084] 3 reagents

[0085] 3.1 Sodium hydroxide standard solution: 0.3226 mol / L;

[0086] 3.2 Hydrochloric acid standard solution: 0.3226 mol / L;

[0087] 3.3 EDTA standard solution: 0.098 mol / L;

[0088] 3.4 Zinc acetate standard solution: 0.03226 mol / L;

[0089] 3.5 Green light-phenolphthalein indicator (1+4): Mix 1 part of green light indicator ethanol solution with 4 parts of 1% phenolphthalein ethanol solution;

[0090] Green light indicator: Dissolve 0.5g of dimethyl yellow in 500mL of anhydrous ethanol; separately dissolve 0.5g of methylene blue in 50mL of water, then add 450mL of anhydrous ethanol. Mix the two solutions.

[0091] 3.6 Acetic acid-sodium acetate buffer solution: (pH 5.2–5.7);

[0092] 3.7 Xylenol Orange Indicator: 0.5%.

[0093] 4 samples

[0094] After filtering, take 5.00 mL or 10.00 mL (depending on the alumina concentration) of the sodium aluminate slurry and dilute it to the mark in a 100 mL volumetric flask. Shake well and set aside.

[0095] 5. Analysis Steps

[0096] Add excess EDTA standard solution (2.2.3.3) (depending on Al2O3 content) to a 250mL Erlenmeyer flask beforehand; add 8 drops of green phenolphthalein indicator (2.2.3.5); transfer 10.00mL or 5.00mL of the prepared test solution to the 250mL Erlenmeyer flask containing the EDTA standard solution (2.2.3.3), shake well, add excess hydrochloric acid standard solution (generally about 5mL excess), shake well, heat to boiling for 1-2 minutes, cool slightly, titrate with sodium hydroxide standard solution until a faint purple color appears, record the volume consumed, add 10mL of acetate-sodium acetate buffer solution (2.2.3.6), add 2 drops of xylenol orange indicator (2.2.3.7), titrate with zinc acetate standard solution (2.2.3.4) until the color changes from yellow to purple-red, which is the endpoint, record the volume consumed.

[0097] 2.2.6 Calculation of Analysis Results

[0098]

[0099]

[0100] In the formula:

[0101] V – The number of milliliters of the original sodium aluminate solution that can be transferred from the sample;

[0102] V1 — The number of milliliters of 0.3226 mol / L hydrochloric acid standard solution added;

[0103] V2 — The number of milliliters of 0.3226 mol / L sodium hydroxide standard solution consumed;

[0104] V3 — The number of milliliters of 0.03226 mol / L zinc acetate standard solution consumed;

[0105] V4 — The number of milliliters of 0.098 mol / L EDTA standard solution added;

[0106] 0.01 – The number of grams of sodium oxide equivalent to 1 mL of 0.3226 mol / L hydrochloric acid (sodium hydroxide) standard solution;

[0107] 0.001 — The number of grams of sodium oxide equivalent to 1 mL of 0.03226 mol / L zinc acetate standard solution;

[0108] 0.005 – The number of grams of aluminum oxide equivalent to 1 mL of 0.098 mol / L EDTA standard solution;

[0109] 0.001645 — the number of grams of aluminum oxide equivalent to 1 ml of 0.03226 mol / L zinc acetate standard solution.

[0110] The analysis and detection of caustic alkali NK involved in Examples 1 to 3 and Control Group 1 of this invention were carried out according to the following method:

[0111] Analysis of caustic sodas

[0112] 1 range

[0113] This standard specifies the method, reagents, sample, analytical procedure, analytical results, precautions, and permissible error for determining the caustic alkali content in sodium aluminate solution by hydrochloric acid titration. Measurement range: >10 g / L.

[0114] 2. Method Summary

[0115] Barium chloride was used to neutralize the interfering anions (CO3). 2－ PO4 3－ BO4 － VO4 3－ SO4 2－ (etc.) to form a precipitate, add sodium salicylate to mask aluminum, use green light-phenolphthalein as an indicator, and titrate the caustic alkali in the sodium aluminate solution with standard hydrochloric acid solution.

[0116] Its reaction is as follows:

[0117] Na₂CO₃ + BaCl₂ → BaCO₃↓ + 2NaCl

[0118] Na₂SO₄ + BaCl₂ → BaSO₄↓ + 2NaCl

[0119] NaOH + HCl → NaCl + H₂O

[0120] 3 reagents

[0121] 3.1 Hydrochloric acid standard solution: 0.3226 mol / L;

[0122] 3.2 Barium chloride (50 g / L);

[0123] 3.3 Sodium salicylate (100g / L);

[0124] 3.4 Green light-phenolphthalein indicator (1+1): Mix 1 part of green light indicator ethanol solution with 1 part of 1% phenolphthalein ethanol solution.

[0125] 4 samples

[0126] After filtering, take 5.00 mL or 10.00 mL (depending on the solution concentration) of the sodium aluminate slurry and dilute it to the mark in a 100 mL volumetric flask. Shake well and set aside.

[0127] 5. Analysis Steps

[0128] In a 500 mL Erlenmeyer flask, add 60 mL of barium chloride solution, 10 mL of sodium salicylate solution, 6 drops of green phenolphthalein indicator, and 10.00 mL or 5.00 mL of sample. Shake well and titrate with standard hydrochloric acid solution (0.3226 mol / L) until the solution turns green, which is the endpoint.

[0129] 6. Calculation of Analysis Results

[0130]

[0131] In the formula:

[0132] V1 — The volume of the original liquid transferred is equivalent to the volume of the sample transferred, in milliliters;

[0133] V—The volume of standard hydrochloric acid solution consumed in the titration, in milliliters;

[0134] 0.01 — 1 ml of hydrochloric acid standard solution is equivalent to the weight of sodium oxide, in grams.

[0135] The above description is a detailed description of the preferred embodiments of the present invention. However, the embodiments are not intended to limit the scope of the patent application of the present invention. All equivalent changes or modifications made under the technical spirit of the present invention should fall within the patent scope covered by the present invention.

Claims

1. A method for preparing a highly stable sodium aluminate slurry, characterized in that, It includes the following steps: S1: Sodium aluminate slurry is selected for preparation during the Bayer process of alumina production; the sodium aluminate slurry is selected from the seed mother liquor in the decomposition process of the Bayer process of alumina production. S2: After filtering the sodium aluminate slurry obtained from S1 with degreased cotton to remove suspended solids and precipitates, place it in a clean and dry container and cool it to room temperature to use as the preparation solution. S3: The solution obtained in S2 is subjected to caustic soda N K Total alkali N T Analysis and detection of alumina (AO) content, and calculation of R P ;R P If the concentration is greater than 0.5, add solid sodium hydroxide and stir continuously until the solid sodium hydroxide is completely dissolved. Repeat this process several times until the solution reaches a concentration of R. P The purity is in the range of 0.45-0.5; the purity of the solid sodium hydroxide is analytical grade or higher. S4: Add 120~130g / L of solid tartaric acid to S3, stir thoroughly to dissolve, and let stand to obtain the highly stable sodium aluminate slurry; The purity of the solid pharmaceutical agent tartaric acid is analytical grade or higher.

Images