Particle size grading-parallel dissolution method for guinea bauxite ore pulp

Abstract

The invention belongs to the field of ore smelting, and particularly discloses a guinea bauxite ore pulp size grading-parallel dissolution method which comprises the following steps: grinding, mixing and heating guinea bauxite and circulating mother liquor to obtain slurry, and screening the slurry into oversize materials and undersize materials; dissolving out the oversize material and the circulating mother liquor at high pressure and high temperature to obtain iron-rich red mud C, and dissolving out the undersize material and the circulating mother liquor at low pressure and low temperature to obtain red mud D; and finally, the red mud D is subjected to reselection treatment, iron-rich red mud E and tailings are obtained through separation, and the whole flow of guineite ore pulp size grading-parallel dissolution is completed. Extremely high-grade bauxite (oversize materials) can be obtained through simple particle size classification, two kinds of bauxite produced through particle size classification are dissolved out through a two-line parallel dissolution method, the oversize materials with the high aluminum-silicon ratio are dissolved out at high pressure and high temperature, the content of iron oxide in the produced iron-rich red mud is higher than 74%, and the recovery value is high.

Description

Technical Field

[0001] This invention belongs to the field of ore smelting and relates to a method for processing bauxite, specifically a method for particle size classification and parallel leaching of Guinean bauxite slurry. Background Technology

[0002] In 2024, China's total annual alumina production reached 85.522 million tons, a 3.9% increase compared to 2023. With the continued expansion of the alumina industry, domestic high-grade bauxite resources are being consumed at an accelerated pace, leading to a continuous increase in the proportion of high-grade bauxite resources imported from abroad. In 2024, China imported 158.6674 million tons of bauxite, of which Guinea accounted for 69.40% of the total imports. Imported Guinea bauxite is mainly composed of gibbsite, characterized by high iron and low silica content, and is currently mostly processed using the low-temperature (140~145℃) Bayer process.

[0003] While the low-temperature Bayer process boasts the advantage of low energy consumption, it suffers from a low alumina recovery rate (actual leaching rate of 80-85%). First, silicon in the ore reacts with alkali and alumina to form insoluble hydrated sodium aluminosilicate (Na₂O·Al₂O₃·1.7SiO₂·nH₂O), resulting in alumina loss and alkali consumption. Second, insufficient alumina leaching leads to a large yield of red mud with a low iron content.

[0004] Currently, there is a lack of comprehensive utilization methods for low-grade red mud. Most low-grade red mud can only be disposed of through open-air stockpiling. As an alkaline waste residue generated during alumina production, indiscriminate stockpiling of red mud not only occupies a large amount of land resources but also causes serious environmental pollution. Furthermore, red mud contains a large amount of valuable metals and has significant recycling potential. Using the low-temperature Bayer process to leach red mud at low temperatures, the Fe2O3 content is only 53%~60%, which does not meet the downstream utilization requirement of a Fe2O3 content greater than 65%. Existing red mud iron beneficiation technology can only extract 10%~20%, and the tailings after separation have no economic value and can only be stockpiled.

[0005] In other words, although the low-temperature Bayer process has the advantage of low energy consumption, it has a low alumina leaching rate, and there are losses of silicon, aluminum and alkali during the leaching process. It also results in a large amount of red mud, low iron content, difficulty in comprehensive utilization, and environmental pollution. Summary of the Invention

[0006] In view of the defects and deficiencies of the existing technology, the present invention provides a method for particle size classification and parallel leaching of Guinean bauxite slurry.

[0007] A method for particle size classification and parallel leaching of Guinean bauxite slurry includes the following steps: Step 1: Grind and mix Guinean bauxite and circulating mother liquor and heat to obtain slurry. Screen the slurry to obtain oversize and undersize materials. Step 2: Mix the material over the sieve and the circulating mother liquor, and dissolve them under high pressure and high temperature conditions to obtain iron-rich red mud C; mix the material under the sieve and the circulating mother liquor, and dissolve them under low pressure and low temperature conditions to obtain red mud D; Step 3: Reselect red mud D to obtain iron-rich red mud E and tailings.

[0008] Preferably, before step 1, the process further includes: crushing Guinean bauxite, screening to obtain crushed material; and then mixing the crushed material and circulating mother liquor in step 1 for alkaline grinding.

[0009] Preferably, the particle size of the crushed material is less than 3.35 mm.

[0010] Preferably, in step 1, the grinding equipment is any one of a semi-autogenous mill, a high-pressure roller mill, a ball mill, or a rod mill.

[0011] Preferably, in step 1, when a rod mill is selected as the grinding equipment, the grinding speed is 10~25 r / min; the grinding time is 5~30 min; and the heating temperature during grinding is 70~100℃.

[0012] Preferably, in step 1, the concentration of caustic alkali in the circulating mother liquor is 150~250g / L; the caustic ratio of the circulating mother liquor is 2.6~3.4.

[0013] Preferably, in step 1, the solid-liquid ratio of Guinean bauxite and circulating mother liquor is 1~4 g / mL.

[0014] Preferably, in step 1, the mesh size of the sieve used for screening the slurry is 6 to 200 mesh, and the mass ratio of the material on the sieve to the material under the sieve is 1:0.33 to 3.

[0015] Preferably, in step 1, the mass ratio of aluminum to silicon in the oversize material is 20-40:1; and the mass ratio of aluminum to silicon in the undersize material is 5-15:1.

[0016] Preferably, after step 1 and before step 2, a refining process for the oversize and undersize materials is included, so that the refined oversize and undersize materials can pass through a 60-mesh screen.

[0017] Preferably, in step 2, the leaching conditions for the material on the sieve are: leaching temperature of 160~280℃, leaching time of 30~60min, and leaching pressure of 1.5~6MPa.

[0018] Preferably, in step 2, the leaching conditions for the undersize material are: leaching temperature of 110~150℃, leaching time of 30~60min, and leaching pressure of 0.5~1.2Mpa.

[0019] Preferably, in step 2, the concentration of caustic alkali in the circulating mother liquor is 210~250g / L, and the caustic ratio of the circulating mother liquor is 2.6~3.4.

[0020] Preferably, in step 2, the solid-liquid ratio of the material on the sieve and the circulating mother liquor is 0.25~0.5 g / mL; the solid-liquid ratio of the material under the sieve and the circulating mother liquor is 0.25~0.5 g / mL.

[0021] Preferably, during gravity separation, red mud D and water are mixed to obtain a slurry, which is then subjected to gravity separation using a gravity separation device; the liquid-to-solid ratio of the slurry is 3~5:1.

[0022] Further optimization can be achieved by selecting any one of the following: hydrocyclone, spiral chute, or shaking table.

[0023] Further optimization involves selecting a shaking table as the gravity separation device, with a horizontal tilt angle of 0°~10°, a longitudinal tilt angle of 1°~3°, a stroke of 8~16mm, and a stroke rate of 250~350 times / min.

[0024] Compared with the prior art, one or more technical solutions provided by the present invention have at least one of the following beneficial effects: (1) High-grade bauxite can be obtained through simple particle size classification.

[0025] (2) A coarse sieve of 6 mesh to 200 mesh can achieve a good silicon separation effect, which is easy to industrialize and simple to operate.

[0026] (3) The two grades of bauxite produced by particle size classification are leached in parallel on two lines. The oversize material with a high aluminum-silicon ratio is leached under high pressure and high temperature, and the iron oxide content in the produced iron-rich red mud is higher than 74%, which has a high recycling value. In contrast, the undersize material with a lower aluminum-silicon ratio can achieve a good leaching effect under low temperature and low pressure conditions. The leached red mud can also be obtained with a high iron oxide content after gravity separation, which also has a recycling value, can improve economic benefits, and can reduce the amount of red mud produced and piled up. Attached Figure Description

[0027] Figure 1 A process flow diagram for the Guinean bauxite slurry particle size classification and parallel leaching method provided by the present invention. Figure 2 The XRD patterns are of the material on the 100-mesh sieve and the material under the 100-mesh sieve obtained in step 2 of Example 1. Detailed Implementation

[0028] The present invention provides the following specific technical solutions.

[0029] A method for particle size classification and parallel leaching of Guinean bauxite slurry includes the following steps: Step 1: Grind and mix Guinean bauxite and circulating mother liquor and heat to obtain slurry. Screen the slurry to obtain oversize and undersize materials. Step 2: Mix the material over the sieve and the circulating mother liquor, and dissolve them under high pressure and high temperature conditions to obtain iron-rich red mud C; mix the material under the sieve and the circulating mother liquor, and dissolve them under low pressure and low temperature conditions to obtain red mud D; Step 3: Reselect red mud D to obtain concentrate E and tailings.

[0030] Through research, the inventors discovered that silicon in Guinean bauxite selectively enriches with particle size distribution. The method provided in this invention leverages this unique property of Guinean bauxite, using simple particle size distribution as the core link to achieve multiple optimizations in ore processing, leaching efficiency, and resource recovery. First, through circulating mother liquor mixing, grinding, and screening, particle size distribution directly separates the oversize material with a high aluminum-to-silicon ratio from the undersize material with high silicon content. This eliminates the need for complex desiliconization processes, yielding extremely high-grade bauxite and simplifying the process from the source, thus reducing processing costs. For the two materials with significantly different properties after classification, a parallel leaching route of high pressure and high temperature, and low pressure and low temperature is employed. High-grade oversize ore undergoes high-pressure leaching to fully release alumina, simultaneously producing iron-rich red mud C that meets iron grade standards and can be directly utilized, solving the problem of low iron grade and difficult utilization of red mud in traditional processes. The high-silicon undersize material undergoes low-pressure leaching, and iron-rich red mud E can still be recovered through gravity separation, significantly improving iron resource recovery rate and reducing the stockpiling of worthless tailings. The entire process is based on the inherent characteristics of the ore, with the grading, differentiated leaching, and gravity separation stages closely linked. This not only reduces the interference of silicon on the leaching process and improves the alumina recovery rate and alkali utilization rate, but also realizes the resource-based grading and utilization of red mud, taking into account the efficiency, economy, and environmental protection of the process.

[0031] Preferably, before step 1, the process further includes: crushing Guinean bauxite to obtain crushed material; then mixing the crushed material with circulating mother liquor for alkaline grinding.

[0032] The inventors discovered through research that directly grinding and mixing Guinean bauxite ore with circulating mother liquor presents significant process defects. First, Guinean bauxite ore is mostly large and uneven in size; direct grinding and mixing with circulating mother liquor significantly increases equipment load. The large hardness and volume of the ore make it difficult for the grinding media to work effectively, increasing energy consumption, shortening equipment lifespan, and easily causing slurry agglomeration and blockage, affecting the uniformity of slurry mixing, resulting in insufficient grinding, significantly reducing grinding efficiency, and failing to consistently produce qualified slurry with uniform particle size. Second, due to geological conditions, the distribution of aluminum, iron, silicon, and other components in different parts of the same Guinean bauxite block is uneven. Direct grinding without pretreatment leads to large fluctuations in slurry composition, which in turn affects subsequent leaching and classification. High-pressure leaching may increase alkali consumption and red mud impurity content, while low-pressure leaching results in unstable leaching rates, increasing the difficulty of screening and gravity separation, disrupting overall process stability, and ultimately affecting the yield and purity of alumina products.

[0033] Equipment suitable for crushing processes includes: gyratory crushers, cone crushers, impact crushers, hammer crushers, and toothed roll crushers.

[0034] Preferably, the particle size of the crushed material is less than 3.35 mm.

[0035] Different equipment is used for crushing, and the crushing parameters are adjusted according to the actual situation. After crushing, a 6-mesh screen is used for sieving. The particle size of the crushed material is less than 3.35mm. This size can ensure the silicon separation effect after alkali grinding and sieving. The operation is simple and easy to industrialize.

[0036] Preferably, in step 1, the grinding equipment is any one of a semi-autogenous mill, a high-pressure roller mill, a ball mill, or a rod mill.

[0037] Preferably, in step 1, when a rod mill is selected as the grinding equipment, the grinding speed is 10~25 r / min; the grinding time is 5~30 min; and the heating temperature during grinding is 70~100℃.

[0038] Depending on the grinding equipment used, the grinding parameters can be adjusted according to the actual needs.

[0039] Preferably, in steps 1 and 2, the total alkali concentration in the circulating mother liquor is 210~300g / L, of which the concentration of caustic alkali is 150~250g / L, the concentration of carbon alkali is 5~30g / L, and the remainder is sulfuric acid alkali and other alkalis; the caustic ratio of the circulating mother liquor is 2.6~3.4.

[0040] Through research, the inventors discovered that optimized parameters for the circulating mother liquor are well-suited to the graded parallel leaching process of Guinean bauxite, offering significant advantages: a caustic alkali concentration of 210~250 g / L ensures efficient alumina leaching, balancing leaching energy consumption with subsequent processes; a caustic alkali ratio of 2.6~3.4 improves the stability of the sodium aluminate solution, preventing premature alumina precipitation. These two factors synergistically reduce ineffective alkali consumption and equipment corrosion, optimize red mud settling performance, and balance production efficiency, economy, and process stability.

[0041] In practical applications, the alkali in the circulating mother liquor exists in various forms, mainly three types: one is caustic alkali (denoted as Na2O) existing in the form of sodium aluminate (NaAlO2) and sodium hydroxide (NaOH). k ); the second is alkali carbonate existing in the form of sodium carbonate (Na2CO3) (denoted as Na2O). C Thirdly, sulfuric acid bases exist in the form of sodium sulfate (Na₂SO₄). Total alkali (denoted as Na₂O) T The total concentration is obtained by summing the values ​​of these different forms of alkali after converting them into sodium oxide. This indicator reflects the overall alkali reserve in the mother liquor and is one of the key parameters for controlling alkali consumption, adjusting reaction conditions, and ensuring stable production in the Bayer process.

[0042] Preferably, in step 1, the solid-liquid ratio of Guinean bauxite and circulating mother liquor is 1~4 g / mL.

[0043] The inventors discovered through research that an excessively high solid-liquid ratio causes a sharp increase in slurry viscosity, reduces fluidity, and can even lead to mill blockage. Conversely, an excessively low solid-liquid ratio reduces the effective impact and grinding efficiency between the grinding media and the ore, preventing full utilization of the mill's production capacity and resulting in high energy consumption per unit. Therefore, the aforementioned optimized solid-liquid ratio helps the entire system establish and maintain a stable material and heat balance.

[0044] Preferably, in step 1, the mesh size of the sieve used for screening the slurry is 6 to 200 mesh, and the mass ratio of the material on the sieve to the material under the sieve is 1:0.33 to 3.

[0045] Through research, the inventors discovered that controlling the screen mesh size and the mass ratio of oversize to undersize material after screening can precisely achieve particle size classification of the slurry. This allows coarse particles to enter high-pressure leaching while fine particles are suited for low-pressure leaching, improving silica separation efficiency and the purity of the leaching solution. Simultaneously, it ensures screening efficiency, avoids clogging issues, adapts to continuous industrial production rhythms, and reduces operating and maintenance costs. This range balances classification accuracy and production feasibility, laying a solid foundation for subsequent parallel leaching and red mud gravity separation, and contributing to improved overall process efficiency and product quality.

[0046] Preferably, in step 1, the mass ratio of aluminum to silicon in the oversize material is 20-40:1; and the mass ratio of aluminum to silicon in the undersize material is 5-15:1.

[0047] In practical applications, the aluminum-silicon ratio in the undersize material is affected by the composition of the raw Guinean bauxite. If the silicon content in the raw ore is high, the aluminum-silicon ratio in the undersize material will decrease accordingly; if the silicon content in the raw ore is low, the aluminum-silicon ratio in the undersize material will increase accordingly.

[0048] Preferably, after step 1 and before step 2, a refining process for the oversize and undersize materials is included, so that the refined oversize and undersize materials can pass through a 60-mesh screen.

[0049] In practical applications, the oversize and undersize materials obtained in step 1 are respectively placed in a grinding device for grinding. The grinding time and parameters are adjusted according to the particle size of the oversize and undersize materials obtained in step 1, so that both the ground oversize and undersize materials can pass through a 60-mesh sieve. If a 60-200 mesh sieve is used in step 1 to obtain the undersize material, then the undersize material does not need to be further refined.

[0050] The grinding equipment that can be used in the refining process includes commonly used existing grinding equipment such as vibratory mills, ball mills, and air jet mills.

[0051] Preferably, in step 2, the leaching conditions for the material on the sieve are: leaching temperature of 160~280℃, leaching time of 30~60min, and leaching pressure of 1.5~6MPa.

[0052] In practical applications, the leaching temperature of the material on the sieve can be 240℃, 250℃, 260℃, or 270℃, the leaching time can be 30min, 40min, 50min, or 60min, and the leaching pressure can be 4MPa, 5MPa, or 6MPa.

[0053] Preferably, in step 2, the leaching conditions for the undersize material are: leaching temperature of 110~150℃, leaching time of 30~60min, and leaching pressure of 0.5~1.2MPa.

[0054] In practical applications, the leaching temperature of the material under the sieve can be 110℃, 120℃, 130℃, 140℃, or 150℃, the leaching time can be 30min, 40min, 50min, or 60min, and the leaching pressure can be 0.5MPa, 0.6MPa, 0.7MPa, 0.8MPa, 0.9MPa, 1.0MPa, 1.1MPa, or 1.2MPa.

[0055] Through research, the inventors discovered that a high aluminum-to-silicon ratio in the sieved minerals allows for the dissolution of diaspore and some boehmite, which are difficult to dissolve at low temperatures, thus increasing the aluminum dissolution rate. Simultaneously, the low silicon content in the ore results in less sodium-silicon slag and reduced alkali consumption. These two factors simultaneously increase the iron content in the red mud, producing iron-rich red mud that can be used in the steel industry, reducing the amount of red mud discharged externally.

[0056] The low aluminum-silicon ratio of the undersized minerals allows for lower production costs through low-temperature leaching, and the resulting red mud can be physically sorted to produce some iron concentrate. Excessive temperature or time will increase production costs, while excessive pressure poses safety hazards. Conversely, excessively low temperatures will result in insufficient leaching of aluminum minerals from the ore, leading to low aluminum recovery rates.

[0057] Preferably, in step 2, the solid-liquid ratio of the material on the sieve and the circulating mother liquor is 0.25~0.5 g / mL; the solid-liquid ratio of the material under the sieve and the circulating mother liquor is 0.25~0.5 g / mL.

[0058] Through research, the inventors discovered that the aforementioned optimized solid-liquid ratio achieves dual optimization of alumina leaching and process stability. This ratio ensures that the free alkali concentration in the circulating mother liquor remains within an appropriate range, providing sufficient reaction medium for the full leaching of alumina from bauxite while maintaining the stability of the sodium aluminate solution. This prevents scaling issues in pipelines and equipment during subsequent processes, ensuring continuous and smooth production. Simultaneously, this solid-liquid ratio allows for reasonable control of alkali consumption, reduces production costs, and minimizes the leaching and degradation of organic matter in bauxite, preventing organic matter from inhibiting subsequent decomposition processes and ensuring the decomposition rate and particle size distribution quality of aluminum hydroxide.

[0059] Preferably, during gravity separation, red mud D and water are mixed to obtain a slurry, which is then subjected to gravity separation using a gravity separation device.

[0060] Further optimization can be achieved by selecting any one of the following: hydrocyclone, spiral chute, or shaking table.

[0061] Further optimization involves selecting a shaking table as the gravity separation device, with a horizontal tilt angle of 0°~10°, a longitudinal tilt angle of 1°~3°, a stroke of 8~16mm, and a stroke rate of 250~350 times / min.

[0062] To make the technical problems, technical solutions and technical advantages of the present invention clearer, a detailed description will be given below with reference to specific examples. However, the scope of protection of the present invention is not limited to the following specific embodiments.

[0063] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0064] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0065] Figure 1 A process flow diagram for the Guinean bauxite slurry particle size classification and parallel leaching method provided by the present invention.

[0066] The composition of the Guinean bauxite used in Examples 1-3 and Comparative Examples 1-2 was: 41.32wt% Al2O3, 2.57wt% SiO2, 24.86wt% Fe2O3, and 1.93wt% TiO2, with an aluminum-to-silicon ratio (mass ratio) of 16.08.

[0067] Example 1: A method for particle size classification and parallel leaching of Guinean bauxite slurry includes the following steps: Step 1: Jaw crushing of Guinean bauxite. Take 15 kg of Guinean bauxite obtained after jaw crushing and 7.5 L of circulating mother liquor and perform alkali milling in a rod mill at 15 r / min. The heating temperature is 70℃. The total alkali concentration in the circulating mother liquor is 255.23 g / L, the caustic alkali concentration is 230 g / L, the carbon-alkali concentration is 17.27 g / L, and the caustic ratio is 3.04.

[0068] Step 2: The slurry obtained in Step 1 was screened using a 100-mesh high-frequency vibrating screen, yielding 8.92 kg of oversize material and 6.07 kg of undersize material. X-ray fluorescence spectroscopy analysis was performed on the screened material. The main components of the oversize material were: 40.20 wt% Al₂O₃, 1.09 wt% SiO₂, 23.37 wt% Fe₂O₃, and 1.72 wt% TiO₂, with an aluminum-to-silicon ratio of 36.88. The main components of the undersize material were: 39.01 wt% Al₂O₃, 3.85 wt% SiO₂, 25.41 wt% Fe₂O₃, and 2.18 wt% TiO₂, with an aluminum-to-silicon ratio of 10.13.

[0069] Step 3: Grind the material on the sieve using a ball mill to make it pass through a 60-mesh sieve. Then, take 1.78 kg of the sieve material and 5 L of circulating mother liquor and react them in a high-pressure reactor for 60 min at a reaction temperature of 245℃ and a reaction pressure of 5.3 MPa. The amount of iron-rich red mud C produced is 0.6 kg. X-ray fluorescence spectroscopy analysis revealed that the composition of the iron-rich red mud C is: 8.56 wt% Al2O3, 1.78 wt% SiO2, 74.26 wt% Fe2O3, 6.35 wt% TiO2, 1.26 wt% Na2O, with an aluminum-silicon ratio of 4.81.

[0070] 1.94 kg of the obtained undersize material and 5 L of circulating mother liquor were reacted in a low-pressure reactor for 60 min at a reaction temperature of 145℃ and a reaction pressure of 1.2 MPa. The amount of red mud D produced was 0.95 kg. X-ray fluorescence spectroscopy analysis revealed that the composition of red mud D was: 21.02 wt% Al2O3, 6.47 wt% SiO2, 58.06 wt% Fe2O3, 5.15 wt% TiO2, 1.64 wt% Na2O, with an aluminum-silicon ratio of 3.24.

[0071] Step 4: Crush the 1 kg of red mud D obtained in Step 3 to below 2 mm, then grind it into finer particles (0.074 mm, 70 wt%) using a ball mill. Add 5 L of water to prepare a slurry (liquid-to-solid ratio 5:1) and stir evenly. Stable feed the slurry into a shaker that has been started, with a stroke of 10 mm, a stroke rate of 300 times / minute, and a transverse inclination angle of 3°. After gravity separation, 0.24 kg of concentrate D is produced. X-ray fluorescence spectroscopy analysis shows that the concentrate D contains 67.14 wt% Fe2O3, 16.47 wt% Al2O3, and 5.07 wt% SiO2. 2、 4.04wt%TiO2.

[0072] Figure 2 The XRD patterns of the material oversize and undersize on the 100-mesh sieve obtained in step 2 of Example 1 are shown below. Figure 1 It can be seen that the composition of the material on the 100-mesh sieve and the material under the 100-mesh sieve is basically the same.

[0073] Comparative Example 1: A method for leaching Guinean bauxite includes the following steps: Step 1: Jaw crushing of Guinean bauxite. Take 15 kg of Guinean bauxite obtained after jaw crushing and 7.5 L of circulating mother liquor and perform alkali milling in a rod mill at 15 r / min. The heating temperature is 70℃. The total alkali concentration in the circulating mother liquor is 255.23 g / L, the caustic alkali concentration is 230 g / L, the carbon-alkali concentration is 17.27 g / L, and the caustic ratio is 3.04.

[0074] Step 2: The material obtained in Step 1 was refined using a ball mill to pass through a 60-mesh sieve. Then, 1.94 kg of the refined material and 5 L of circulating mother liquor were reacted in a low-pressure reactor for 60 min at a reaction temperature of 145℃ and a reaction pressure of 1.2 MPa. The produced red mud amounted to 0.80 kg. X-ray fluorescence spectroscopy analysis revealed the red mud composition to be: 18.15 wt% Al₂O₃ and 5.29 wt% SiO₂. 2、 61.60wt%Fe2O3, 4.89wt%TiO2, 1.08wt%Na2O, with an aluminum-to-silicon ratio of 3.4.

[0075] Step 3: Crush the 1 kg of red mud obtained in Step 2 to below 2 mm, then grind it into finer particles (0.074 mm, 70 wt%) using a ball mill. Add 5 L of water to prepare a slurry (liquid-to-solid ratio 5:1) and stir evenly. Stable feed the slurry into a shaker that has been started, with a stroke of 10 mm, a stroke rate of 300 times / minute, and a transverse inclination angle of 3°. After gravity separation, 0.25 kg of concentrate D is produced. X-ray fluorescence spectroscopy analysis shows that concentrate D contains 67.86 wt% Fe2O3, 13.43 wt% Al2O3, and 5.13 wt% SiO2. 2、 4.43wt%TiO2.

[0076] Comparative Example 2: A method for leaching Guinean bauxite includes the following steps: Step 1: Jaw crushing of Guinean bauxite. Take 15 kg of Guinean bauxite obtained after jaw crushing and 7.5 L of circulating mother liquor and perform alkali milling in a rod mill at 15 r / min. The heating temperature is 70℃. The total alkali concentration in the circulating mother liquor is 255.23 g / L, the caustic alkali concentration is 230 g / L, the carbon-alkali concentration is 17.27 g / L, and the caustic ratio is 3.04.

[0077] Step 2: The material obtained in Step 1 is refined using a ball mill to pass through a 60-mesh sieve. Then, 1.78 kg of the refined material and 5 L of circulating mother liquor are reacted in a high-pressure reactor for 60 min at 245℃ and 5.3 MPa. The yield of red mud is 0.69 kg, and its composition is: 10.59 wt% Al₂O₃ and 6.56 wt% SiO₂. 2、 It contains 63.74 wt% Fe2O3, 4.97 wt% TiO2, and 2.68% Na2O, with an aluminum-to-silicon ratio of 1.61.

[0078] Step 3: Crush the 1 kg of red mud obtained in Step 2 to below 2 mm, then grind it into finer particles (0.074 mm, 70 wt%) using a ball mill. Add 5 L of water to prepare a slurry (liquid-to-solid ratio 5:1) and stir evenly. Stable feed the slurry into a shaker that has been started, with a stroke of 10 mm, a stroke rate of 300 times / minute, and a transverse inclination angle of 3°. After gravity separation, 0.28 kg of concentrate D is produced. X-ray fluorescence spectroscopy analysis shows that concentrate D contains 68.86 wt% Fe2O3, 9.10 wt% Al2O3, and 5.64 wt% SiO2. 2、 4.27wt% TiO2.

[0079] In step 2 of Comparative Examples 1 and 2, since the aluminum-silicon ratio of the ore is prone to difference in actual process, the inventors controlled the ore blending amount of Comparative Examples 1 and 2 to be consistent with that of Example 1 for the experiment.

[0080] Example 2: A method for particle size classification and parallel leaching of Guinean bauxite slurry includes the following steps: Step 1: Break Guinean bauxite. Take 10 kg of Guinean bauxite obtained from screening and 5 L of circulating mother liquor and perform alkali milling in a rod mill at 18 r / min. The heating temperature is 80℃. The total alkali concentration in the circulating mother liquor is 255.23 g / L, the caustic alkali concentration is 230 g / L, the carbon-alkali concentration is 17.27 g / L, and the caustic ratio is 3.04.

[0081] Step 2: The obtained slurry was screened using a 100-mesh high-frequency vibrating screen, yielding 4.97 kg of oversize material and 5.01 kg of undersize material. X-ray fluorescence spectroscopy analysis was performed on the screened material. The main components of the oversize material were: 41.95 wt% Al₂O₃, 1.16 wt% SiO₂, 23.62 wt% Fe₂O₃, and 1.76 wt% TiO₂, with an aluminum-to-silicon ratio of 36.16. The main components of the undersize material were: 39.00 wt% Al₂O₃, 3.33 wt% SiO₂, 24.79 wt% Fe₂O₃, and 2.10 wt% TiO₂, with an aluminum-to-silicon ratio of 11.71.

[0082] Step 3: The material obtained in Step 1 was refined using a grinding mill to pass through a 60-mesh sieve. Then, 1.78 kg of the refined material and 5 L of circulating mother liquor were reacted in a high-pressure reactor for 60 min at a reaction temperature of 270℃ and a reaction pressure of 6 MPa. The yield of iron-rich red mud C was 0.58 kg. X-ray fluorescence spectroscopy analysis revealed the following composition of the iron-rich red mud C: 7.27 wt% Al₂O₃, 2.69 wt% SiO₂, 75.10 wt% Fe₂O₃, 5.60 wt% TiO₂, 1.22 wt% Na₂O, with an aluminum-silicon ratio of 2.70.

[0083] 1.94 kg of the obtained undersize material and 5 L of circulating mother liquor were reacted in a low-pressure reactor for 60 min at a reaction temperature of 150℃ and a reaction pressure of 1.2 MPa, producing 0.94 kg of red mud D. X-ray fluorescence spectroscopy analysis revealed the following composition of red mud D: 20.86 wt% Al₂O₃, 6.15 wt% SiO₂, 58.12 wt% Fe₂O₃, 5.18 wt% TiO₂, 1.66 wt% Na₂O, with an aluminum-to-silicon ratio of 3.39.

[0084] Step 4: Take 1 kg of red mud D, crush it to below 2 mm, and then grind it into finer particles (0.074 mm, 70 wt%) using a ball mill. Add 5 L of water to prepare a slurry (liquid-to-solid ratio 5:1) and stir evenly. Stable feed the slurry into a shaker that has already been started, with a stroke of 10 mm, a stroke rate of 300 times / minute, and a transverse inclination angle of 3°. After gravity separation, 0.25 kg of concentrate C is produced. The concentrate C has an Fe2O3 content of 68.62 wt%, Al2O3 content of 15.63 wt%, and SiO2 content of 4.61 wt%. 2、 3.88wt%TiO2.

[0085] Example 3: A method for particle size classification and parallel leaching of Guinean bauxite slurry includes the following steps: Step 1: Jaw crushing of Guinean bauxite. Take 20 kg of Guinean bauxite obtained after jaw crushing and 10 L of circulating mother liquor and perform alkali milling in a rod mill at 10 r / min. The heating temperature is 75℃. The total alkali concentration in the circulating mother liquor is 255.23 g / L, the caustic alkali concentration is 230 g / L, the carbon-alkali concentration is 17.27 g / L, and the caustic ratio is 3.04.

[0086] Step 2: The obtained slurry was screened using an 18-mesh high-frequency vibrating screen, yielding 9.04 kg of material over the 18-mesh screen and 10.92 kg of material under the 18-mesh screen. X-ray fluorescence spectroscopy analysis was performed on the screened materials. The analysis showed that the main components of the material over the 18-mesh screen were: 42.68 wt% Al₂O₃, 1.23 wt% SiO₂, 21.21 wt% Fe₂O₃, and 1.78 wt% TiO₂, with an aluminum-to-silicon ratio of 34.70; the main components of the material under the 18-mesh screen were: 40.43 wt% Al₂O₃, 3.24 wt% SiO₂, 24.06 wt% Fe₂O₃, and 2.13 wt% TiO₂, with an aluminum-to-silicon ratio of 12.48.

[0087] Step 3: The material obtained in Step 1 was refined using a ball mill to pass through a 60-mesh sieve. Then, 1.94 kg of the refined material and 5 L of circulating mother liquor were reacted in a low-pressure reactor for 60 min at a reaction temperature of 165℃ and a reaction pressure of 1.5 MPa. The amount of iron-rich red mud C produced was 0.76 kg. After testing, the composition of the iron-rich red mud C was found to be: 15.27 wt% Al2O3, 1.92 wt% SiO2, 67.95 wt% Fe2O3, 5.37 wt% TiO2, 0.81 wt% Na2O, with an aluminum-silicon ratio of 7.95.

[0088] The material obtained in step 1 was refined using a ball mill to pass through a 60-mesh sieve. Then, 1.94 kg of the refined undersize material and 5 L of circulating mother liquor were reacted in a low-pressure reactor for 60 min at a reaction temperature of 130℃ and a reaction pressure of 1.0 MPa, yielding 1.02 kg of red mud D. Analysis revealed the composition of red mud D to be: 24.59 wt% Al₂O₃, 7.41 wt% SiO₂, 55.03 wt% Fe₂O₃, 4.87 wt% TiO₂, and 1.19 wt% Na₂O, with an aluminum-to-silicon ratio of 3.32.

[0089] Step 4: Take 1 kg of red mud D, crush it to below 2 mm, and then grind it into finer particles (0.074 mm, 70 wt%) using a ball mill. Add 5 L of water to prepare a slurry (liquid-to-solid ratio 5:1) and stir evenly. Stable feed the slurry into a shaker that has already been started, with a stroke of 10 mm, a stroke rate of 300 times / minute, and a transverse inclination angle of 3°. After gravity separation, 0.21 kg of concentrate C is produced. The concentrate C has an Fe2O3 content of 67.86 wt%, Al2O3 content of 16.05 wt%, and SiO2 content of 5.76 wt%. 2、 3.82wt%TiO2.

[0090] According to the process route disclosed in Example 1, when processing 1 ton of Guinean bauxite, the Fe2O3 content of the 200.46 kg of red mud obtained by leaching the oversize material is higher than 74%, and the red mud obtained by leaching the undersize material is 198.18 kg. After gravity separation, 47.56 kg of red mud with an Fe2O3 content higher than 67% is obtained. That is, the iron-rich red mud yield of the process route provided by the present invention reaches 62.22%, and only 150.62 kg of stockpiled red mud is produced when processing 1 ton of Guinean bauxite.

[0091] According to the process route disclosed in Comparative Example 1, processing 1 ton of Guinean bauxite yielded 412.37 kg of red mud with an Fe2O3 content of approximately 60 wt%. After gravity separation, 103.09 kg of iron-rich red mud with an Fe2O3 content of 67.86 wt% and 309.28 kg of stockpiled red mud were obtained, with a yield of 25% for the iron-rich red mud.

[0092] According to the process route disclosed in Comparative Example 2, processing 1 ton of Guinean bauxite yielded 387.64 kg of red mud with a Fe2O3 content of 63 wt%. After gravity separation, 108.54 kg of iron-rich red mud with a Fe2O3 content of 68.86 wt% and 279.1 kg of stockpiled red mud were obtained, with a yield of 28% for the iron-rich red mud.

[0093] It should be noted that although the Fe2O3 content of the iron-rich red mud D obtained in Example 1 is 67.14 wt%, the Fe2O3 content of the iron-rich red mud obtained by gravity separation in Comparative Example 1 is 67.86 wt%, and the Fe2O3 content of the iron-rich red mud obtained by gravity separation in Comparative Example 2 is 68.83 wt%, none of them have reached 70 wt%, but they are close to 70 wt%. In actual production, they have certain utilization value, that is, they are classified as iron-rich red mud.

[0094] Comparing the data of the iron-rich red mud produced in Example 1 and Comparative Example 1, firstly, the Fe2O3 content of the red mud produced by the mesothermal process in Example 1 is significantly higher than that of the iron-rich red mud produced by gravity separation in Comparative Example 1, indicating that the iron-rich red mud produced in Example 1 has higher economic benefits. Secondly, the amount of red mud requiring gravity separation produced in Example 1 is only 48.06% of that in Comparative Example 1, meaning that Example 1 requires less red mud for gravity separation, resulting in lower production costs. Finally, when processing 1 ton of Guinean bauxite, Example 1 produces 150.62 kg of stockpiled red mud, while Comparative Example 1 produces 309.28 kg of stockpiled red mud, demonstrating that the red mud emission reduction rate of the Example 1 route is significantly higher than that of the Comparative Example 1 route.

[0095] Comparing the data of iron-rich red mud produced in Example 1 and Comparative Example 2, when processing the same amount of Guinean bauxite, the route in Example 1 results in 40.47% of the ore entering the low-temperature leaching line, leading to lower overall energy consumption. The Fe2O3 content of the red mud produced in Example 1 via the medium-temperature line is significantly higher than that of the iron-rich red mud produced by gravity separation in Comparative Example 2, indicating higher economic benefits. The amount of red mud requiring gravity separation in Example 1 is only 51.12% of that in Comparative Example 2, resulting in less red mud requiring gravity separation and lower production costs. Finally, processing 1 ton of Guinean bauxite, Example 1 produces 150.62 kg of stockpiled red mud, while Comparative Example 2 produces 279.1 kg. The red mud emission reduction rate of the route in Example 1 is significantly higher than that of the route in Comparative Example 2.

[0096] Example 4: A method for particle size classification and parallel leaching of Guinean bauxite slurry, differing from Example 1, involves sieving the slurry obtained in Step 1 using a 6-mesh high-frequency vibrating screen in Step 2, yielding 3.97 kg of oversize material and 11.02 kg of undersize material. X-ray fluorescence spectroscopy analysis of the sieved materials revealed that the main components of the oversize material were: 40.26 wt% Al₂O₃, 1.23 wt% SiO₂, 22.50 wt% Fe₂O₃, and 1.74 wt% TiO₂, with an aluminum-to-silicon ratio of 32.73; the main components of the undersize material were: 40.70 wt% Al₂O₃, 3.01 wt% SiO₂, 24.71 wt% Fe₂O₃, and 2.00 wt% TiO₂, with an aluminum-to-silicon ratio of 13.52.

[0097] All other steps are the same as in Example 1.

[0098] Example 5: A method for particle size classification and parallel leaching of Guinean bauxite slurry, differing from Example 1, involves sieving the slurry obtained in Step 1 using a 6-mesh high-frequency vibrating screen in Step 2, yielding 8.13 kg of oversize material and 6.86 kg of undersize material. X-ray fluorescence spectroscopy analysis of the sieved materials revealed that the main components of the oversize material were: 42.13 wt% Al₂O₃, 1.84 wt% SiO₂, 25.24 wt% Fe₂O₃, and 1.86 wt% TiO₂, with an aluminum-to-silicon ratio of 22.90; the main components of the undersize material were: 39.97 wt% Al₂O₃, 3.46 wt% SiO₂, 24.06 wt% Fe₂O₃, and 2.02 wt% TiO₂, with an aluminum-to-silicon ratio of 11.55.

[0099] All other steps are the same as in Example 1.

[0100] Example 6: A method for particle size classification and parallel leaching of Guinean bauxite slurry, differing from Example 1, involves sieving the slurry obtained in Step 1 using a 6-mesh high-frequency vibrating screen in Step 2, yielding 4.99 kg of oversize material and 9.98 kg of undersize material. X-ray fluorescence spectroscopy analysis of the sieved materials revealed that the main components of the oversize material were: 41.01 wt% Al₂O₃, 1.33 wt% SiO₂, 24.12 wt% Fe₂O₃, and 1.80 wt% TiO₂, with an aluminum-to-silicon ratio of 30.83; the main components of the undersize material were: 40.26 wt% Al₂O₃, 3.73 wt% SiO₂, 23.65 wt% Fe₂O₃, and 2.11 wt% TiO₂, with an aluminum-to-silicon ratio of 10.79.

[0101] All other steps are the same as in Example 1.

[0102] Example 7: A method for particle size classification and parallel leaching of Guinean bauxite slurry, differing from Example 1, involves sieving the slurry obtained in Step 1 using a 40-mesh high-frequency vibrating screen in Step 2, yielding 9.63 kg of oversize material and 5.36 kg of undersize material. X-ray fluorescence spectroscopy analysis of the sieved materials revealed that the main components of the oversize material were: 41.36 wt% Al₂O₃, 1.39 wt% SiO₂, 24.33 wt% Fe₂O₃, and 1.79 wt% TiO₂, with an aluminum-to-silicon ratio of 29.76; the main components of the undersize material were: 39.92 wt% Al₂O₃, 3.76 wt% SiO₂, 24.22 wt% Fe₂O₃, and 2.12 wt% TiO₂, with an aluminum-to-silicon ratio of 10.62.

[0103] All other steps are the same as in Example 1.

[0104] Example 8: A method for particle size classification and parallel leaching of Guinean bauxite slurry, differing from Example 1, involves sieving the slurry obtained in Step 1 using a 200-mesh high-frequency vibrating screen in Step 2, yielding 3.75 kg of oversize material and 11.15 kg of undersize material. X-ray fluorescence spectroscopy analysis of the sieved materials revealed that the main components of the oversize material were: 41.72 wt% Al₂O₃, 1.55 wt% SiO₂, 24.37 wt% Fe₂O₃, and 1.82 wt% TiO₂, with an aluminum-to-silicon ratio of 26.92; the main components of the undersize material were: 38.74 wt% Al₂O₃, 3.81 wt% SiO₂, 24.29 wt% Fe₂O₃, and 2.20 wt% TiO₂, with an aluminum-to-silicon ratio of 10.17.

[0105] All other steps are the same as in Example 1.

[0106] Example 9: A method for particle size classification and parallel leaching of Guinean bauxite slurry, differing from Example 1, involves sieving the slurry obtained in Step 1 using a 100-mesh high-frequency vibrating screen in Step 2, yielding 4.92 kg of oversize material and 9.98 kg of undersize material. X-ray fluorescence spectroscopy analysis of the sieved materials revealed that the main components of the oversize material were: 41.20 wt% Al₂O₃, 1.38 wt% SiO₂, 24.62 wt% Fe₂O₃, and 1.86 wt% TiO₂, with an aluminum-to-silicon ratio of 29.86; the main components of the undersize material were: 38.74 wt% Al₂O₃, 4.00 wt% SiO₂, 24.20 wt% Fe₂O₃, and 2.06 wt% TiO₂, with an aluminum-to-silicon ratio of 9.69.

[0107] All other steps are the same as in Example 1.

[0108] Example 10: A method for particle size classification and parallel leaching of Guinean bauxite slurry, differing from Example 1, involves sieving the slurry obtained in Step 1 using a 100-mesh high-frequency vibrating screen in Step 2, yielding 3.82 kg of oversize material and 11.12 kg of undersize material. X-ray fluorescence spectroscopy analysis of the sieved materials revealed that the main components of the oversize material were: 41.47 wt% Al₂O₃, 1.36 wt% SiO₂, 25.40 wt% Fe₂O₃, and 1.86 wt% TiO₂, with an aluminum-to-silicon ratio of 30.49; the main components of the undersize material were: 39.28 wt% Al₂O₃, 3.42 wt% SiO₂, 24.10 wt% Fe₂O₃, and 2.00 wt% TiO₂, with an aluminum-to-silicon ratio of 11.49.

[0109] All other steps are the same as in Example 1.

[0110] Example 11: A method for particle size classification and parallel leaching of Guinean bauxite slurry, differing from Example 1, involves sieving the slurry obtained in Step 1 using a 200-mesh high-frequency vibrating screen in Step 2, yielding 5.13 kg of oversize material and 9.87 kg of undersize material. X-ray fluorescence spectroscopy analysis of the sieved materials revealed that the main components of the oversize material were: 40.84 wt% Al₂O₃, 1.69 wt% SiO₂, 24.52 wt% Fe₂O₃, and 1.81 wt% TiO₂, with an aluminum-to-silicon ratio of 24.17; the main components of the undersize material were: 38.69 wt% Al₂O₃, 5.05 wt% SiO₂, 24.13 wt% Fe₂O₃, and 2.15 wt% TiO₂, with an aluminum-to-silicon ratio of 7.66.

[0111] All other steps are the same as in Example 1.

[0112] Example 12: A method for particle size classification and parallel leaching of Guinean bauxite slurry, differing from Example 1, involves sieving the slurry obtained in Step 1 using a 200-mesh high-frequency vibrating screen in Step 2, yielding 11.10 kg of oversize material and 3.89 kg of undersize material. X-ray fluorescence spectroscopy analysis of the sieved materials revealed that the main components of the oversize material were: 40.79 wt% Al₂O₃, 1.76 wt% SiO₂, 24.52 wt% Fe₂O₃, and 1.85 wt% TiO₂, with an aluminum-to-silicon ratio of 23.18; the main components of the undersize material were: 39.16 wt% Al₂O₃, 5.20 wt% SiO₂, 23.84 wt% Fe₂O₃, and 2.19 wt% TiO₂, with an aluminum-to-silicon ratio of 7.53.

[0113] All other steps are the same as in Example 1.

[0114] The parameters of the aluminum-silicon ratio and the mass ratio of the oversize and undersize materials obtained after alkaline grinding in Examples 1-12 are shown in Table 1.

[0115] Table 1. Silica-to-alumina ratio and mass ratio of oversize and undersize materials.

[0116] As shown in Table 1, after grinding with circulating mother liquor and sieving with 6-200 mesh in Examples 1-12, the mass ratio of the material on the sieve to the material under the sieve was controlled at 1:0.33-3. Examples 1-12 all showed that the aluminum-silicon ratio of the material on the sieve was significantly higher than that of the material under the sieve. This fully confirms the unique property of selective enrichment of silicon components in Guinean bauxite with particle size classification. The data in Table 1 proves that the present invention can separate the material on the sieve with a high aluminum-silicon ratio and the material under the sieve with a high silicon content through simple sieving, simplifying the process from the source without the need for a complicated silicon removal process.

[0117] The above-described embodiments are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the technical scope of the present invention, based on the technical solution and concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for particle size classification and parallel leaching of Guinean bauxite slurry, characterized in that, Includes the following steps: Step 1: Grind and mix Guinean bauxite and circulating mother liquor and heat to obtain slurry. Screen the slurry to obtain oversize and undersize materials. Step 2: Mix the material over the sieve and the circulating mother liquor, and dissolve it under high pressure and high temperature conditions to obtain iron-rich red mud C; mix the material under the sieve and the circulating mother liquor, and dissolve it under low pressure and low temperature conditions to obtain red mud D; Step 3: Reselect red mud D to obtain concentrate E and tailings.

2. The method for particle size classification and parallel leaching of Guinean bauxite slurry as described in claim 1, characterized in that, In step 1, the sieve used for screening the slurry has a mesh size of 6 to 200, and the mass ratio of the material on the sieve to the material under the sieve is 1:0.33 to 3.

3. The method for particle size classification and parallel leaching of Guinean bauxite slurry as described in claim 1, characterized in that, In step 2, the leaching conditions for the material on the sieve are: leaching temperature of 160~280℃, leaching time of 30~60min, and leaching pressure of 1.5~6MPa.

4. The method for particle size classification and parallel leaching of Guinean bauxite slurry as described in claim 1 or 3, characterized in that, In step 2, the leaching conditions for the undersize material are: leaching temperature of 110~150℃, leaching time of 30~60min, and leaching pressure of 0.5~1.2Mpa.

5. The method for particle size classification and parallel leaching of Guinean bauxite slurry as described in claim 1, characterized in that, The process includes a refining step between step 1 and step 2, which refines the oversize and undersize materials so that the refined oversize and undersize materials can pass through a 60-mesh screen.

6. The method for particle size classification and parallel leaching of Guinean bauxite slurry as described in claim 1, characterized in that, In step 1, the grinding equipment can be any one of a semi-autogenous mill, a high-pressure roller mill, a ball mill, or a rod mill. When a rod mill is selected, the grinding speed is 10~25 r / min; the grinding time is 5~30 min; and the heating temperature during grinding is 70~100℃.

7. The method for particle size classification and parallel leaching of Guinean bauxite slurry as described in claim 1, characterized in that, The concentration of caustic alkali in the circulating mother liquor is 150~250g / L; the caustic ratio of the circulating mother liquor is 2.6~3.

4.

8. The method for particle size classification and parallel leaching of Guinean bauxite slurry as described in claim 1 or 5, characterized in that, In step 1, the solid-liquid ratio of Guinean bauxite and circulating mother liquor is 1~4 g / mL; in step 2, the solid-liquid ratio of the oversize material and circulating mother liquor is 0.25~0.5 g / mL; the solid-liquid ratio of the undersize material and circulating mother liquor is 0.25~0.5 g / mL.

9. The method for particle size classification and parallel leaching of Guinean bauxite slurry as described in claim 1, characterized in that, During gravity separation, red mud D and water are mixed to obtain a slurry, which is then subjected to gravity separation using gravity separation equipment.

10. The method for particle size classification and parallel leaching of Guinean bauxite slurry as described in claim 9, wherein the liquid-to-solid ratio of the slurry is 3-5:1, and the gravity separation equipment can be any one of a hydrocyclone, a spiral chute, or a shaking table; when a shaking table is selected as the gravity separation equipment, the transverse inclination angle of the table surface is 0°-10°, the longitudinal inclination angle is 1°-3°, the stroke is 8-16 mm, and the stroke rate is 250-350 times / min.

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