Method for preparing sodium metaaluminate powder

Abstract

The application discloses a preparation method of sodium metaaluminate powder, and the method comprises the following steps: mixing sodium metaaluminate clinker and a dissolving medium according to a mass ratio of 1:3-8, stirring and heating the mixture to dissolve soluble materials in the sodium metaaluminate clinker, and performing pressure filtration to obtain sodium metaaluminate crude liquid and a first solid residue; adding a calcium solid silicon additive into the sodium metaaluminate crude liquid to remove silicon and heavy metals, and performing filtration to obtain sodium metaaluminate fine liquid and a second solid residue; mixing the first solid residue and the second solid residue, washing and drying the mixed solid residue to obtain a mixture of a silicon compound, a calcium compound and magnesium aluminum spinel; controlling the temperature of the sodium metaaluminate fine liquid to perform evaporation concentration, cooling crystallization, solid-liquid separation, controlling the temperature of the obtained sodium metaaluminate crystals to perform drying and crushing to obtain sodium metaaluminate powder. The preparation method of the sodium metaaluminate powder has the advantages of environmental friendliness, resource recycling and high product quality, and has an industrial application prospect.

Description

Technical Field

[0001] This invention relates to the field of inorganic chemical technology, and more specifically, to a method for preparing sodium aluminate powder. Background Technology

[0002] Sodium aluminate (chemical formula NaAlO2) is a white, powdery inorganic compound, readily soluble in water, and its aqueous solution is strongly alkaline. It is an important industrial raw material with a wide range of applications. Sodium aluminate is mainly used in water treatment, building materials, papermaking, and petrochemicals. In water treatment, it is used as a water purification agent to accelerate clarification and sedimentation. In building materials, it is used as a cement accelerator to improve early strength and impermeability. In papermaking, it is used as a filler to increase whiteness and basis weight. In petrochemicals, it is used in oil refining, aromatic hydrocarbon purification, and as a catalyst carrier.

[0003] Currently, the main industrial method for preparing sodium aluminate is sintering. The basic process includes: raw material sintering, where bauxite, soda ash, and limestone are mixed, ground, and sintered at high temperature in a rotary kiln to produce soluble sodium aluminate clinker; clinker leaching, where the clinker is crushed and leached with dilute alkaline solution or hot water to allow sodium aluminate to enter the solution; crude liquor purification, removing impurities such as silicon and iron from the solution to obtain a refined sodium aluminate solution; and evaporation and drying, where the refined solution is evaporated and dried to obtain the finished sodium aluminate product.

[0004] The existing sintering processes generally suffer from the following problems: direct discharge of saline wastewater; untreated washing wastewater is discharged, resulting in high environmental costs; low utilization rate of calcium waste residue, which is used for landfill or road paving; continuous accumulation of salt in the mother liquor, leading to the forced discharge of high-salt wastewater. The refining process is lengthy and energy-intensive, with lengthy multi-stage impurity removal processes, high consumption of additives and energy, making it difficult to consistently produce high-quality products.

[0005] To address the aforementioned issues, the traditional preparation process for sodium aluminate in the existing technology urgently needs improvement. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a method for preparing sodium aluminate powder, comprising the following steps: S10, sodium aluminate clinker and leaching medium are mixed at a mass ratio of 1:3-8 to form a mixture. The mixture is stirred and heated under controlled temperature to dissolve the soluble materials in the sodium aluminate clinker and form a solid-liquid mixture. S20, the solid-liquid mixture is subjected to pressure filtration to obtain sodium aluminate crude liquid and first solid residue; S30, add calcium-based silicon-fixing agent to the crude sodium aluminate solution to remove silicon and heavy metals, and filter to obtain refined sodium aluminate solution and second solid residue. S40, the first solid slag and the second solid slag are mixed to form a mixed solid slag, and the mixed solid slag is washed and dried to obtain a mixture of compounds mainly composed of silicon, calcium and magnesium aluminum spinel. S50 is used to concentrate sodium aluminate concentrate by temperature control, cool and crystallize, and separate solid and liquid to obtain sodium aluminate crystals. S60 is used to dry and pulverize sodium aluminate crystals under controlled temperature to obtain sodium aluminate powder.

[0007] Preferably, cooling water and mother liquor are also obtained in S50; after S50, the process further includes: Reserve the cooling water for washing purposes; Detect the target salt content in the mother liquor; Determine whether the target salt content has reached the preset salt content value; if the target salt content has not reached the preset salt content value, the mother liquor is retained as the dissolution medium; if the target salt content has reached the preset salt content value, the mother liquor is sequentially subjected to evaporation and concentration, cooling and crystallization, and solid-liquid separation to obtain the target salt.

[0008] Preferably, the preset salt content is 8% to 10%.

[0009] Preferably, in step S30, the amount of calcium-based silica-fixing agent added is 0.3-3% of the crude sodium aluminate solution by mass percentage.

[0010] Preferably, in S30, the calcium-based silicon-fixing agent comprises the following components by mass percentage: 80-85% quicklime, 10-15% tricalcium aluminate hydrate, and 0-5% calcium sulfide.

[0011] Preferably, in step S30, after adding the calcium-based silica-fixing agent to the crude sodium aluminate solution, the method further includes adding a flocculant to the crude sodium aluminate solution.

[0012] Preferably, in S40, a three-stage countercurrent water washing process is used to wash the mixed solid slag, with the washing water flowing in the opposite direction to the mixed solid slag.

[0013] Preferably, in S50, the sodium aluminate concentrate is concentrated by temperature-controlled evaporation under negative pressure heating conditions.

[0014] Preferably, in S50, a segmented gradient cooling crystallization method is used to cool and crystallize the sodium aluminate concentrate obtained after evaporation and concentration of sodium aluminate concentrate according to a preset cooling curve, so that the sodium aluminate concentrate is slowly cooled to the target temperature and sodium aluminate crystals are precipitated.

[0015] Preferably, in step S60, the sodium aluminate crystals are dried under vacuum heating conditions to prevent decomposition and / or side reactions during the drying process, and to control the water content of the sodium aluminate crystals to 5-10%.

[0016] The beneficial effects of this invention are as follows: The method for preparing sodium aluminate powder provided by this invention involves dissolving sodium aluminate clinker in a leaching medium, then pressurizing and filtering to obtain a crude sodium aluminate solution. A calcium-based silicon-fixing agent is added to remove silicon and heavy metals, yielding a refined sodium aluminate solution. The first and second solid slags generated during the preparation process are washed, dried, and, after passing impurity testing, retained as industrial raw materials. The washing water is retained as a leaching medium for later use. The refined sodium aluminate solution is then subjected to temperature-controlled evaporation and concentration, cooling crystallization, and solid-liquid separation. The sodium aluminate crystals obtained from the solid-liquid separation are then dried and pulverized under controlled temperature to obtain sodium aluminate powder. Throughout the entire sodium aluminate powder preparation process, industrial water is recycled in a closed loop, achieving zero discharge of industrial wastewater, thus reducing environmental protection costs and conserving industrial water resources. Simultaneously, the solid slag generated during the preparation process is effectively separated and recycled, retained as industrial raw materials for reuse, realizing the resource utilization of by-products and preventing secondary pollution. Furthermore, the method for preparing sodium aluminate powder provided by this invention has a short process flow and is easy to operate, reducing equipment investment and operating energy consumption, and is easy to promote industrially. The final sodium aluminate powder has high purity and good chemical stability, and all performance indicators meet the requirements of national standard grade I products, making it highly competitive in the market.

[0017] In summary, the method for preparing sodium aluminate powder provided by this invention has the advantages of being environmentally friendly, resource-recycling, and producing high-quality products, and has promising prospects for industrial application. Attached Figure Description

[0018] The accompanying drawings, which are provided to further illustrate the invention and constitute a part of this invention, are illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention.

[0019] Figure 1 This is a schematic flowchart of the method for preparing sodium aluminate powder according to the present invention.

[0020] Figure 2 This is another schematic diagram of the preparation method of sodium aluminate powder according to the present invention. Detailed Implementation

[0021] The following drawings disclose several embodiments of the present invention. For clarity, many practical details will be described in the following description. However, it should be understood that these practical details are not intended to limit the invention. That is, in some embodiments of the invention, these practical details are not essential. Furthermore, for the sake of simplicity, some conventional structures and components will be shown in the drawings in a simple schematic manner.

[0022] It should be noted that all directional indications in the embodiments of the present invention, such as up, down, left, right, front, back, etc., are only used to explain the relative positional relationship and movement of the components in a specific posture as shown in the attached figure. If the specific posture changes, the directional indication will also change accordingly.

[0023] Furthermore, in this invention, the use of terms such as "first," "second," etc., is for descriptive purposes only and does not specifically refer to any order or sequence, nor is it intended to limit the invention. They are merely used to distinguish items or operations described using the same technical terms and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the technical solutions of the various embodiments can be combined with each other, but only if they are feasible for those skilled in the art. If a combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0024] To further understand the invention's content, features, and effects, the following embodiments are provided, and detailed descriptions are given below in conjunction with the accompanying drawings: Reference Figure 1 , Figure 1 This is a schematic flowchart of the method for preparing sodium aluminate powder according to the present invention. The method for preparing sodium aluminate powder provided by the present invention includes the following steps: S10, sodium aluminate clinker and leaching medium are mixed at a mass ratio of (1:3-8) to form a mixture. The mixture is stirred and heated under controlled temperature to dissolve the soluble materials in the sodium aluminate clinker, forming a solid-liquid mixture.

[0025] In step S10, sodium aluminate clinker and leaching medium are added to the reactor at a mass ratio of 1:3-8 to form a mixture. Then, the stirring and heating temperature control functions of the reactor are turned on to heat the mixture, controlling the temperature of the mixture within the range of 80℃-90℃, and stirring is continued for 40min to 80min to completely dissolve the soluble materials in the sodium aluminate clinker. The stirring speed is 150 r / min-300 r / min.

[0026] The purpose of controlling the temperature of the mixture in step S10 within the range of 80℃ to 90℃ is twofold: firstly, to utilize the high solubility of sodium aluminate within this temperature range to achieve complete dissolution and improve dissolution efficiency; and secondly, to avoid excessively high temperatures that could lead to hydrolysis of sodium aluminate or side reactions, thus ensuring the purity of the final product and the stability of the process.

[0027] S20, the solid-liquid mixture is subjected to pressure filtration to obtain crude sodium aluminate solution and first solid residue.

[0028] In step S20, the solid-liquid mixture is pressurized and filtered at a pressure of 0.3-0.6 MPa to obtain crude sodium aluminate solution and the first solid slag.

[0029] In step S20, the first solid slag is a solid impurity that is insoluble in the leaching medium after sodium aluminate clinker is added to the leaching medium and heated and stirred. Its main components include: silicon compounds, calcium compounds and magnesium aluminum spinel.

[0030] S30, calcium-based silicon-fixing agent is added to the crude sodium aluminate solution to remove silicon and heavy metals, and the solution is filtered to obtain refined sodium aluminate solution and a second solid residue.

[0031] In this step S30, the amount of calcium silicate additive added is 0.3-3% of the crude sodium aluminate solution by mass percentage.

[0032] In step S30, the calcium-based silicon-fixing agent comprises the following components by mass percentage: 80-85% quicklime, 10-15% tricalcium aluminate hydrate, and 0-5% calcium sulfide.

[0033] In step S30, after adding the calcium-based silica-fixing agent to the crude sodium aluminate solution, the method further includes adding a flocculant. Adding a flocculant enables the small solid particles generated after the sodium aluminate solution is treated with the calcium-based silica-fixing agent to agglomerate and settle. The flocculant used in this invention is PAM (polyacrylamide).

[0034] Whether the calcium-based silicon-fixing agent in step S30 includes calcium sulfide needs to be determined based on the comparison between the free heavy metal content in the crude sodium aluminate solution and the standard content. If the free heavy metal content in the crude sodium aluminate solution is less than or equal to the standard content, calcium sulfide does not need to be added; if it is greater than the standard content, calcium sulfide needs to be added. The specific content of calcium sulfide needs to be determined based on the content of each free heavy metal in the crude sodium aluminate solution. Heavy metals include, but are not limited to: iron (Fe), zinc (Zn), lead (Pb), copper (Cu), and cadmium (Cd). Preferably, when the free heavy metal content in the crude sodium aluminate solution is greater than the standard content, the added calcium-based silicon-fixing agent consists of 80% active quicklime, 15% active tricalcium aluminate hydrate, and 5% calcium sulfide. The calcium-based silicon-fixing agent is used to chemically react with the free silicon and free heavy metals such as iron, zinc, lead, copper, and cadmium in the crude sodium aluminate solution, converting them into water-insoluble solid particles. Then, by using flocculants, these tiny particles are made to clump together and settle, thus separating them from the liquid.

[0035] In addition, a small amount of sludge in the sodium aluminate crude solution is filtered, and the sludge and aggregated solid particles in the sodium aluminate crude solution form a second solid residue.

[0036] S40, the first solid slag and the second solid slag are mixed to form a mixed solid slag, and the mixed solid slag is washed and dried to obtain a mixture of compounds mainly composed of silicon, calcium and magnesium aluminum spinel.

[0037] The mixture described in this invention is retained as industrial raw material after passing impurity testing, and the washing water after washing the mixed solid slag is retained as a leaching medium for later use.

[0038] In step S40, a three-stage countercurrent water washing process is used to wash the mixed solid slag. The washing water flows in the opposite direction to the mixed solid slag to thoroughly wash away any residual leaching liquid in the mixed solid slag.

[0039] In step S40, a baking temperature of 100℃ to 110℃, preferably 105℃, is used to dry the mixed solid slag until the moisture content of the mixed solid slag meets the standard, which is 5% to 25%. After drying, the mixed solid slag needs to be tested for impurities. If the impurities meet the standard, it is retained as industrial raw material; if not, it undergoes impurity removal treatment to meet the standard before being retained as industrial raw material. Specifically, the impurity content testing is conducted according to general industrial raw material impurity content standards.

[0040] S50 is used to concentrate sodium aluminate concentrate by temperature control, followed by cooling crystallization and solid-liquid separation to obtain sodium aluminate crystals.

[0041] In step S50, sodium aluminate concentrate is concentrated by temperature control under negative pressure heating conditions to prevent sodium aluminate from decomposing and / or undergoing side reactions during the evaporation and concentration process.

[0042] In this step S50, sodium aluminate concentrate is concentrated by negative pressure and temperature control within a negative pressure range of -0.08 MPa to -0.085 MPa and a temperature range of 82°C to 86°C. Preferably, the sodium aluminate concentrate is concentrated by evaporation at -0.082 MPa and 84°C.

[0043] In step S50, a segmented gradient cooling crystallization method is used. The sodium aluminate concentrate obtained after evaporation and concentration of sodium aluminate concentrate is cooled and crystallized according to a preset cooling curve, allowing the sodium aluminate concentrate to cool slowly to the target temperature, causing sodium aluminate crystals to precipitate. Specifically, during the cooling and crystallization process of the sodium aluminate concentrate, the concentration is controlled to cool at a rate of 1-5℃ / hour until the target temperature (35℃ to 40℃) is reached, and then held at that temperature for 2-6 hours.

[0044] In step S50, after the sodium aluminate in the sodium aluminate concentrate is cooled and crystallized, the solid-liquid mixture is separated by centrifugation at a speed of 800 r / min-1500 r / min to obtain sodium aluminate crystals and centrifugation mother liquor. The centrifugation mother liquor is reserved as a dissolution medium for later use.

[0045] S60 is used to dry and pulverize sodium aluminate crystals under controlled temperature to obtain sodium aluminate powder.

[0046] In step S60, sodium aluminate crystals are dried under vacuum heating conditions with controlled temperature to prevent decomposition and / or side reactions during the drying process, and to control the water content of the sodium aluminate crystals to 5-10%. Specifically, the sodium aluminate crystals are dried within a vacuum range of -0.055MPa to 0.065MPa and a temperature range of 85℃ to 90℃.

[0047] In step S60, the dried sodium aluminate crystals are pulverized according to actual needs to obtain sodium aluminate powder with the target particle size.

[0048] Furthermore, in the method for preparing sodium aluminate powder provided by the present invention, cooling water and mother liquor are also obtained in step S50. The cooling water is reserved for washing water, specifically for washing the mixed solid slag in step S50, and can also be reserved as a dissolution medium.

[0049] See Figure 2 , Figure 2 This is another schematic diagram of the preparation method of sodium aluminate powder according to the present invention. The method further includes the following step after S50: S01, detect the target salt content in the mother liquor; S02, determine whether the target salt content has reached the preset salt content value. If the target salt content has not reached the preset salt content value, the mother liquor is retained as the dissolution medium. If the target salt content has reached the preset salt content value, the mother liquor is sequentially evaporated and concentrated, cooled and crystallized, and then separated into solid and liquid components to obtain the target salt.

[0050] In step S50, after the sodium aluminate concentrate in the solution is cooled and crystallized, the mother liquor obtained by solid-liquid separation of the solid-liquid mixture still contains other soluble salts. These soluble salts can be used as industrial salts. When the soluble salt content in the mother liquor reaches a certain value, it can be collected and extracted. The preset salt content in step S02 is the criterion for determining whether to collect and extract the soluble salts from the mother liquor. The preset salt content in this invention is 8% to 10%.

[0051] In step S02, if the target salt content does not reach the preset salt content, it indicates that the target salt content is not high enough and does not meet the standard for collection and extraction. At this time, the mother liquor can be reserved as a dissolution medium for later use. After at least one cycle of steps S10 to S50, the corresponding target salt in the mother liquor will be enriched and increased. When the increase reaches or exceeds the preset salt content, the target salt can be collected and extracted.

[0052] In step S02, when the target salt content reaches the preset salt concentration, it indicates that the target salt content is high enough to meet the standard for collection and extraction. The process of collecting and extracting the target salt from the mother liquor involves: sequentially performing conventional evaporation and concentration, conventional cooling and crystallization, and conventional solid-liquid separation to obtain the target salt. The cooling water generated in step S02 is reserved for washing water and / or dissolution medium, and the centrifuged liquid generated is reserved for dissolution medium.

[0053] The method for preparing sodium aluminate powder provided by this invention achieves closed-loop recycling of industrial water and zero discharge of industrial wastewater throughout the entire preparation process, reducing environmental protection costs and conserving industrial water resources. Simultaneously, the solid slag generated during the preparation process is effectively separated and recycled, retained as industrial raw material for reuse, realizing the resource utilization of by-products and preventing secondary pollution. Furthermore, the method for preparing sodium aluminate powder provided by this invention features a simple process flow and easy operation, reducing equipment investment and operating energy consumption, making it easy to promote industrial application. The resulting sodium aluminate powder has high purity and good chemical stability, with all performance indicators meeting the national standard for Grade I products, giving it strong market competitiveness.

[0054] The sodium aluminate clinker used in this invention is prepared by conventional wet sintering process, wherein the Al2O3 content is 40-47% and the Na2O content is 31-34%; the Al2O3 dissolution rate is ≥90% and the Na2O dissolution rate is ≥95%.

[0055] The technical solution of the present invention will be further described in detail below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and do not constitute a limitation on the scope of protection of the present invention. Equivalent adjustments or optimizations made by those skilled in the art based on the core concept of the present invention should still fall within the scope of protection of the present invention.

[0056] Example 1000 grams of sodium aluminate clinker is provided. The sodium aluminate clinker is divided into three portions: the first portion is 334 grams, the second portion is 333 grams, and the third portion is 333 grams. The ratio of the first portion, the second portion, and the third portion to the leaching medium is 1:5 by mass.

[0057] I. The preparation of sodium aluminate powder using the first batch of 334 grams of sodium aluminate clinker as raw material includes the following steps: S10, add the first 334g of sodium aluminate clinker and the leaching medium (ordinary industrial water) into the reactor, turn on the stirring and heating temperature control function of the reactor, heat the mixture, control the temperature of the mixture at 85℃, and stir continuously for 60min at a stirring speed of 200r / min to form a solid-liquid mixture.

[0058] S20, the solid-liquid mixture is pressure filtered at 0.5 MPa to obtain sodium aluminate crude liquid and the first solid slag.

[0059] S30, calcium silicate additive and flocculant PAM are added to the crude sodium aluminate solution to remove silicon and heavy metals, and the solution is filtered to obtain refined sodium aluminate solution and second solid slag.

[0060] Based on the mass percentage of the crude sodium aluminate solution, the amount of calcium silicate additive added is 1.5% of the crude sodium aluminate solution, and the amount of flocculant PAM added is 0.1% of the crude sodium aluminate solution.

[0061] The calcium-based silicon-fixing additive comprises, by mass percentage, 15% tricalcium aluminate hydrate, 80% quicklime, and 5% CaS.

[0062] S40, the first solid slag and the second solid slag are mixed to form a mixed solid slag. The mixed solid slag is washed using a three-stage countercurrent water washing process, with the washing water flowing in the opposite direction to the mixed solid slag, resulting in 435 grams of wet mixed solid slag. The wet mixed solid slag is then dried at a temperature of 105°C to obtain 292 grams of mixed solid slag with a moisture content of 3%. After passing the impurity test, the slag is retained as industrial raw material, and the washing water is retained as a leaching medium for later use.

[0063] S50 was used to evaporate and concentrate sodium aluminate concentrate at -0.082 MPa and 84℃. A segmented gradient cooling crystallization method was employed to cool and crystallize the concentrated sodium aluminate solution, controlling the temperature drop at a rate of 4℃ / hour until reaching 38℃. Cooling was then stopped, and the solution was held at this temperature for 4 hours to obtain a solid-liquid mixture. The mixture was then separated by centrifugation to obtain sodium aluminate crystals and a mother liquor. The target salt content in the mother liquor was found to be below 9%, and the mother liquor was reserved as a dissolution medium.

[0064] S60, sodium aluminate crystals are dried under a vacuum of -0.06 MPa and a temperature of 90°C; the dried sodium aluminate crystals are then pulverized according to the preset target particle size requirements to obtain the first batch of sodium aluminate powder with a target particle size of 223 grams.

[0065] 2. Using the second batch of 333 grams of sodium aluminate clinker as raw material, prepare sodium aluminate powder by performing the same operations as S10 to S50 above, except that the leaching medium used is the centrifuged mother liquor obtained during the preparation of the first batch of sodium aluminate powder and the washing water after washing the mixed solid slag; 432 grams of wet mixed solid slag, 290 grams of dried mixed solid slag, and 220 grams of the second batch of sodium aluminate powder with the target particle size are obtained. The target salt content in the mother liquor is lower than the preset value of 9% and is reserved as the leaching medium for later use.

[0066] III. Using the third batch of 333 grams of sodium aluminate clinker as raw material, sodium aluminate powder is prepared by performing the same operations as S10 to S50 above, except that the leaching medium used is the centrifuged mother liquor obtained during the preparation of the second batch of sodium aluminate powder and the washing water after washing the mixed solid slag; 434 grams of wet mixed solid slag, 291 grams of dried mixed solid slag, and 222 grams of sodium aluminate powder with the target particle size are obtained. The target salt content in the mother liquor is higher than the preset value by 9%. The mother liquor is subjected to conventional evaporation concentration, conventional cooling crystallization, and conventional solid-liquid separation to obtain 32 grams of target salt. The target salt includes sodium chloride and potassium chloride. When the total content of sodium chloride and potassium chloride is higher than the preset value, the mother liquor is subjected to conventional evaporation concentration, conventional cooling crystallization, and conventional solid-liquid separation.

[0067] The cooling water generated during the preparation of the first batch of sodium aluminate powder is reserved as washing water for the preparation of the second batch of sodium aluminate powder. Any unused cooling water is returned for use as cooling water after its temperature drops.

[0068] The cooling water generated during the preparation of the second batch of sodium aluminate powder is reserved as washing water for the preparation of the third batch of sodium aluminate powder. Any unused cooling water is recycled for subsequent cooling processes after its temperature drops.

[0069] The first, second, and third portions of sodium aluminate powder were mixed evenly to obtain the sodium aluminate powder of the present invention. The relevant performance indicators of the sodium aluminate powder were tested. The test methods are shown in Table 1, and the test results are shown in Table 2.

[0070] Table 1:

[0071] Table 2:

[0072] As can be seen from the above, the sodium aluminate powder prepared by the method provided by this invention has high purity and good chemical stability, and all performance indicators meet the requirements of the national standard for first-grade products, making it highly competitive in the market. Throughout the entire preparation process of sodium aluminate powder, industrial water is recycled in a closed loop, achieving zero discharge of industrial wastewater, which reduces environmental protection costs and conserves industrial water resources. Simultaneously, the solid slag generated during the preparation process is effectively separated and recycled, retained as industrial raw materials for reuse, realizing the resource utilization of by-products and preventing secondary pollution. Furthermore, the method for preparing sodium aluminate powder provided by this invention has a simple process flow and is easy to operate, reducing equipment investment and operating energy consumption, making it easy to promote industrial application.

[0073] In summary, the method for preparing sodium aluminate powder provided by this invention has the advantages of being environmentally friendly, resource-recycling, and producing high-quality products, and has promising prospects for industrial application.

[0074] The above description is merely an embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principle of the present invention should be included within the scope of the claims of the present invention.

Claims

1. A method for preparing sodium aluminate powder, characterized in that, Includes the following steps: S10, sodium aluminate clinker and leaching medium are mixed at a mass ratio of (1:3-8) to form a mixture. The mixture is stirred and heated under controlled temperature to dissolve the soluble materials in the sodium aluminate clinker and form a solid-liquid mixture. S20, the solid-liquid mixture is subjected to pressure filtration to obtain sodium aluminate crude liquid and first solid residue; S30, add calcium-based silicon-fixing agent to the crude sodium aluminate solution to remove silicon and heavy metals, and filter to obtain refined sodium aluminate solution and second solid residue. S40, the first solid slag and the second solid slag are mixed to form a mixed solid slag, and the mixed solid slag is washed and dried to obtain a mixture of compounds mainly composed of silicon, calcium and magnesium aluminum spinel. S50 is used to concentrate sodium aluminate concentrate by temperature control, cool and crystallize, and separate solid and liquid to obtain sodium aluminate crystals. S60 is used to dry and pulverize sodium aluminate crystals under controlled temperature to obtain sodium aluminate powder.

2. The method for preparing sodium aluminate powder according to claim 1, characterized in that, In step S50, cooling water and mother liquor are also obtained; step S50 further includes: Detect the target salt content in the mother liquor; Determine whether the target salt content has reached the preset salt content value. If the target salt content has not reached the preset salt content value, the mother liquor is retained as the dissolution medium. If the target salt content has reached the preset salt content value, the mother liquor is sequentially subjected to evaporation and concentration, cooling and crystallization, and solid-liquid separation to obtain the target salt.

3. The method for preparing sodium aluminate powder according to claim 2, characterized in that, The preset salt content is 8% to 10%.

4. The method for preparing sodium aluminate powder according to claim 1, characterized in that, In step S30, the amount of calcium silicate additive added is 0.3-3% of the crude sodium aluminate solution by mass percentage.

5. The method for preparing sodium aluminate powder according to claim 1 or 4, characterized in that, In S30, the calcium-based silicon-fixing agent comprises the following components by mass percentage: 80-85% quicklime, 10-15% tricalcium aluminate hydrate, and 0-5% calcium sulfide.

6. The method for preparing sodium aluminate powder according to claim 5, characterized in that, In step S30, after adding the calcium-based silica-fixing agent to the crude sodium aluminate solution, the method further includes adding a flocculant to the crude sodium aluminate solution.

7. The method for preparing sodium aluminate powder according to claim 1, characterized in that, In S40, a three-stage countercurrent water washing process is used to wash the mixed solid slag, with the washing water flowing in the opposite direction to the mixed solid slag.

8. The method for preparing sodium aluminate powder according to claim 1, characterized in that, In S50, sodium aluminate concentrate is concentrated by temperature-controlled evaporation under negative pressure heating conditions.

9. The method for preparing sodium aluminate powder according to claim 1, characterized in that, In S50, a segmented gradient cooling crystallization method is adopted. The sodium aluminate concentrate obtained after evaporation and concentration of sodium aluminate concentrate is cooled and crystallized according to a preset cooling curve, so that the sodium aluminate concentrate is slowly cooled to the target temperature and sodium aluminate crystals are precipitated.

10. The method for preparing sodium aluminate powder according to claim 1, characterized in that, In step S60, sodium aluminate crystals are dried under vacuum heating conditions to prevent decomposition and / or side reactions during the drying process, and to control the water content of the sodium aluminate crystals to 5-10%.

Images