A high temperature settling process without flocculants

Abstract

The application discloses a flocculant-free high-temperature sedimentation method, which comprises the following steps: conveying the mixed solution formed by the sodium aluminate solution after causticization reaction and causticization residues to the center feed well in the inside of the sedimentation tank through a feed pipe; and dispersing the energy of the mixed solution through a nozzle before the mixed solution enters the center feed well, so that the speed of the mixed solution entering the center feed well is reduced to not more than 1 m / s, thereby reducing the disturbance to the sedimentation materials in the inside of the sedimentation tank during the feeding process of the mixed solution without adding flocculants. The application can directly and quickly sediment by means of the temperature of the high-temperature mixed solution itself without reducing the temperature and pressure, without adding flocculants and other sedimentation accelerators, thereby reducing the production cost, avoiding the pollution of the production materials caused by the organic flocculants entering the production system, and reducing the energy consumption.

Description

Technical Field

[0001] This invention relates to a flocculant-free high-temperature sedimentation method, belonging to the field of high-temperature sedimentation technology. Background Technology

[0002] Currently, with the continuous decline in alumina ore grade, high-carbon and other impurity-rich ores are entering the alumina production system. These high-carbon ores react with sodium aluminate solution to form carbonates. As carbonates accumulate in the system, they have a significant negative impact on alumina production. Therefore, side-flow causticizing of the washing liquor has become a necessary step to remove sodium carbonate.

[0003] In the washing liquid side-flow causticization system, the washing liquid undergoes pre-causticization. After solid-liquid separation, the solids and washing liquid undergo a second high-temperature causticization reaction. After the second high-temperature causticization reaction, the mixture needs to be separated into qualified sodium aluminate solution and causticization slag in a settling tank, which are then sent to different sections to meet the production liquid balance. Traditional settling separation technology generally uses a combination of large deep cone, flat-bottom settling tank and flocculant for solid-liquid flocculation and settling separation.

[0004] Traditional sedimentation systems typically operate at temperatures below 100℃. To promote sedimentation, flocculants must be added to induce the aggregation of tiny particles into larger flocs, thereby increasing the sedimentation rate and achieving adequate sedimentation capacity and a clear supernatant. This consumes a large amount of flocculant, increasing production costs, and the introduction of organic flocculants into the production system causes organic contamination of the materials. Furthermore, forced cooling also results in energy loss and increased energy consumption. Therefore, flocculant-free high-temperature sedimentation technology is highly valuable while simultaneously meeting production requirements. Summary of the Invention

[0005] The purpose of this invention is to provide a flocculant-free high-temperature sedimentation method, which solves the problem that traditional technologies require a large amount of flocculant, increasing production costs and energy consumption.

[0006] The technical solution of this invention to solve the above-mentioned technical problems is as follows: A flocculant-free high-temperature sedimentation method, using a flocculant-free high-temperature sedimentation device, including a sedimentation tank, the sedimentation tank having a central feed well inside; several nozzles are distributed around the edge of the central feed well, each nozzle being connected to a feed pipe; the outer end of the feed pipe forms a feed inlet extending from the side of the sedimentation tank; a stirring shaft is connected to the center of the sedimentation tank, the stirring shaft extending through the central feed well to the lower part of the sedimentation tank; a rake is connected to the lower end of the stirring shaft; a conical guide is connected to the stirring shaft below the bottom opening of the central feed well;

[0007] The mixture of sodium aluminate solution after causticization reaction and causticization slag is transported through a feed pipe to the central feed well inside the settling tank. Before the mixture enters the central feed well, the energy of the mixture is dispersed through a nozzle, so that the velocity of the mixture entering the central feed well is reduced to no more than 1 m / s.

[0008] As a preferred embodiment of the high-temperature sedimentation method without flocculants, the material settled at the bottom of the sedimentation tank is stirred to change the rheological properties of the settled material, and the liquid-to-solid ratio of the discharged settled material is adjusted to prevent blockage at the bottom of the sedimentation tank.

[0009] As a preferred method for high-temperature sedimentation without flocculants, the velocity of the mixture entering the central feed well is reduced to no more than 0.8 m / s.

[0010] As a preferred method for high-temperature sedimentation without flocculants, the temperature of the mixture formed by the sodium aluminate solution after the causticization reaction and the causticization slag is controlled at 90~200℃.

[0011] As a preferred embodiment of the high-temperature sedimentation method without flocculants, the sedimentation tank includes a sedimentation cylinder, a closed top cover, and a closed bottom cover; the closed top cover is formed at the top of the sedimentation cylinder, and the closed bottom cover is formed at the bottom of the sedimentation cylinder; the sedimentation cylinder is cylindrical, and the closed bottom cover is conical.

[0012] As a preferred embodiment of the high-temperature sedimentation method without flocculants, the top of the closed top cover is connected to a drive motor, and the drive end of the drive motor is connected to the top of the stirring shaft.

[0013] As a preferred embodiment of the high-temperature sedimentation method without flocculants, the top of the closed top cover is connected to a safety port, and the safety port is connected to a safety valve.

[0014] An overflow port is connected to the upper side of the settling cylinder, and an overflow regulating valve is connected to the overflow port.

[0015] As a preferred embodiment of the high-temperature sedimentation method without flocculants, the lower end of the closed bottom cover is connected to a discharge port, and the discharge port is connected to a discharge valve; a circulation port is provided on one side of the closed bottom cover, and the circulation port is connected to a circulation valve.

[0016] The discharge valve is connected to a variable frequency pump via a first conveying pipeline, and the variable frequency pump is connected to a discharge pipeline; the discharge pipeline is connected to the circulation valve via a second conveying pipeline; a circulation control valve is provided on the second conveying pipeline.

[0017] As a preferred embodiment of the high-temperature sedimentation method without flocculants, a central well support frame is connected between the side of the central feed well and the inner wall of the sedimentation tank.

[0018] The diameter of the bottom opening of the central feed well is smaller than the maximum outer diameter of the conical guide.

[0019] As a preferred embodiment of the high-temperature sedimentation method without flocculants, the nozzle is provided with four nozzles, which are evenly distributed around the central feed well; each nozzle is connected to a feed pipe on its outer side.

[0020] The diameter of the nozzle near the feed pipe end is smaller than the diameter of the nozzle near the central feed well end.

[0021] The beneficial effects of this invention are as follows: the mixture formed by the sodium aluminate solution after the causticization reaction and the causticization slag is transported through a feed pipe to the central feed well inside the settling tank; before the mixture enters the central feed well, the energy of the mixture is dispersed through nozzles, reducing the velocity of the mixture entering the central feed well to no more than 1 m / s, thereby reducing the disturbance to the settling materials inside the settling tank during the feeding process without adding flocculants. This invention utilizes the temperature of the high-temperature mixture itself, eliminating the need for cooling and depressurization operations and the addition of flocculants or other settling agents, allowing for direct and rapid settling, reducing production costs, preventing organic flocculants from entering the production system and causing organic pollution of production materials, and reducing energy consumption. Attached Figure Description

[0022] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings in the following description are merely exemplary, and those skilled in the art can derive other embodiments based on the provided drawings without creative effort.

[0023] The structures, proportions, sizes, etc. illustrated in this specification are only for the purpose of assisting those skilled in the art in understanding and reading the content disclosed herein, and are not intended to limit the conditions under which the present invention can be implemented. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in the proportions, or adjustments to the size, without affecting the effects and objectives that the present invention can produce, should still fall within the scope of the technical content disclosed in the present invention.

[0024] Figure 1 This is a schematic diagram illustrating the relationship between settling rate and temperature for the same solution concentration in the high-temperature sedimentation method without flocculant provided in this embodiment of the invention.

[0025] Figure 2 A schematic diagram of the structure of the flocculant-free high-temperature sedimentation equipment used in the flocculant-free high-temperature sedimentation method provided in the embodiments of the present invention;

[0026] Figure 3 A schematic diagram showing the distribution of the feed pipe, nozzle, and central feed well in the high-temperature sedimentation method without flocculant provided in this embodiment of the invention;

[0027] Figure 4 This is a schematic diagram of the feeding process in the high-temperature sedimentation method without flocculants provided in this embodiment of the invention.

[0028] In the diagram, 1. Settling tank; 2. Central feed well; 3. Nozzle; 4. Feed pipe; 5. Feed inlet; 6. Agitator shaft; 7. Rake; 8. Conical guide; 9. Settling cylinder; 10. Sealed top cover; 11. Sealed bottom cover; 12. Drive motor; 13. Safety port; 14. Safety valve; 15. Overflow port; 16. Overflow regulating valve; 17. Discharge port; 18. Discharge valve; 19. Circulation port; 20. Circulation valve; 21. First conveying pipeline; 22. Variable frequency pump; 23. Discharge pipeline; 24. Second conveying pipeline; 25. Circulation control valve; 26. Central well support frame. Detailed Implementation

[0029] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0030] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0031] The flocculant-free high-temperature sedimentation method provided in this embodiment utilizes the high temperature of the mixture itself after the causticization reaction, eliminating the need for cooling and allowing direct sedimentation separation, thus reducing the cost of cooling equipment and energy consumption. Simultaneously, sedimentation at high temperatures significantly increases the solution's viscosity and density, which greatly improves the sedimentation rate. This not only results in faster sedimentation and a reduction in the volume of sedimentation tank 1, but also significantly improves the compressibility of the material discharged from the bottom of sedimentation tank 1 and eliminates the need for flocculants and other sedimentation promoters.

[0032] As is well known, particle settling velocity is mainly affected by the density difference between solid and liquid, temperature, and viscosity. Stokes' formula for free settling of particles in still water is:

[0033] u=gd 2 (ρs-ρ) / 18μ①

[0034] In the formula, u is the particle settling velocity (cm / s); ρs and ρ are the densities of the particles and water, respectively (g / cm³); and g is the acceleration due to gravity (cm / s²). 2 μ is the adhesion coefficient of water (Pa·s); d is the particle diameter (cm).

[0035] By measuring the density of sodium aluminate solution, the formula for calculating the density of sodium aluminate solution was derived:

[0036] ρ 20℃ ={0 .5+(0.25+0.00144N+0.0009A+0.001865Nc)0.5}②

[0037] ρ x℃ ={0.5+(0.25+0.00144N+0.0009A+0.001865Nc)0.5}×(1.011-0.0005*x) ③

[0038] In the formula, N is the mass concentration of caustic alkali (g / L); A is the mass concentration of alumina (g / L); Nc is the mass concentration of carbon-alkali mixture (g / L); ρ 20℃ This is the density of sodium aluminate solution at 20°C.

[0039] The relationship between the viscosity of sodium aluminate solution and temperature, alumina concentration, and solution rpm was obtained through experimental calculations and multiple linear fitting:

[0040] Lnη=-1.554+1.139×1.645 / rp+0.0187×A-0.0503T④

[0041] In the formula, rp is the mass ratio of alumina to caustic alkali in the sodium aluminate solution; A is the mass concentration of alumina (g / L); η is the viscosity of the sodium aluminate solution (MPa·s); and T is the temperature of the sodium aluminate solution.

[0042] See Figure 1 The relationship between settling velocity and temperature at the same solution concentration (with 90℃ as the baseline) is shown. Combining formulas ①, ③, and ④, the settling velocity of causticized slag in sodium aluminate solution is related to the particle size itself, but in actual production, the particle size is relatively stable, and the most significant factor is solution temperature. The settling velocity at 150℃ is 20 times that at 90℃, and the settling velocity at 200℃ is 200 times that at 90℃. Therefore, the flocculant-free high-temperature settling method proposed in this embodiment is theoretically feasible. The following are the specific contents of this embodiment.

[0043] See Figure 2 , Figure 3 and Figure 4This embodiment describes a flocculant-free high-temperature sedimentation method. The flocculant-free high-temperature sedimentation equipment includes a sedimentation tank 1, with a central feed well 2 inside the sedimentation tank 1. Several nozzles 3 are distributed around the edge of the central feed well 2, and each nozzle 3 is connected to a feed pipe 4. The outer end of the feed pipe 4 forms a feed inlet 5 extending from the side of the sedimentation tank 1. A stirring shaft 6 is connected to the center of the sedimentation tank 1, extending through the central feed well 2 to the lower part of the sedimentation tank 1. A rake 7 is connected to the lower end of the stirring shaft 6. The stirring shaft 6 feeds through the central feed well. A conical guide 8 is connected below the bottom opening of well 2. This flocculant-free high-temperature sedimentation method transports the mixture formed by the sodium aluminate solution after causticization reaction and the causticization slag through the feed pipe 4 to the central feed well 2 inside the sedimentation tank 1. Before the mixture enters the central feed well 2, the energy of the mixture is dispersed through the nozzle 3, so that the velocity of the mixture entering the central feed well 2 is reduced to no more than 1m / s, so as to reduce the disturbance of the sedimentation material inside the sedimentation tank 1 during the feeding process of the mixture without adding flocculants.

[0044] In this embodiment, the settling tank 1 includes a settling cylinder 9, a closed top cover 10, and a closed bottom cover 11. The closed top cover 10 is formed at the top of the settling cylinder 9, and the closed bottom cover 11 is formed at the bottom of the settling cylinder 9. The settling cylinder 9 is cylindrical, and the closed bottom cover 11 is conical. A drive motor 12 is connected to the top of the closed top cover 10, and the drive end of the drive motor 12 is connected to the top of the stirring shaft 6. This allows for stirring of the material settled at the bottom of the settling tank 1, altering the rheological properties of the settled material, and adjusting the liquid-to-solid ratio of the discharged settled material to prevent blockage at the bottom of the settling tank 1.

[0045] In this embodiment, four nozzles 3 are provided, evenly distributed around the central feed well 2. Each nozzle 3 is connected to a feed pipe 4 on its outer side. The diameter of the nozzle 3 near the feed pipe 4 is smaller than the diameter of the nozzle 3 near the central feed well 2. By adopting a design of four evenly distributed pressure-reducing nozzles 3, each nozzle 3 is symmetrical along the axis of the central feed well and is equipped with an energy dissipation function. When the high-temperature mixture enters the central feed well 2, the velocity of the slurry is reduced to no more than 1 m / s, preferably less than 0.8 m / s or 0.5 m / s. Thus, the velocity and kinetic energy of the high-temperature mixture minimize the disturbance to the solids settling in the settling tank 1 when it impacts the solids already settling in the central feed well 2. Using nozzles 3 for feeding reduces the disturbance to the materials inside the settling tank 1, eliminating the need for flocculants or other settling agents.

[0046] In this embodiment, the temperature of the mixture formed by the sodium aluminate solution and the causticizing slag after the causticizing reaction is controlled between 90 and 200°C. From the theoretical analysis and experiments above, it can be seen that the settling velocity of the causticizing slag in the sodium aluminate solution is related to its particle size, but in actual production, the particle size is relatively stable, and the most influential factor is the solution temperature. The settling velocity at 150°C is 20 times that at 90°C, and the settling velocity at 200°C is 200 times that at 90°C. Therefore, controlling the temperature of the mixture between 90 and 200°C is optimal. Utilizing the high temperature of the mixture itself, there is no need for cooling or depressurization operations, and flocculants or other settling agents are not required for direct and rapid settling.

[0047] In this embodiment, a safety port 13 is connected to the top of the closed top cover 10, and a safety valve 14 is connected to the safety port 13; the safety port 13, combined with the safety valve 14 and the pressure inside the settling tank 1, can achieve the inherent safety of the equipment.

[0048] In this embodiment, an overflow port 15 is connected to the upper side of the settling cylinder 9, and an overflow regulating valve 16 is connected to the overflow port 15. By automatically adjusting the outlet flow rate of the overflow port 15 using the overflow regulating valve 16, the temperature and pressure inside the settling tank 1 can be effectively controlled, and the settling speed can be more effectively guaranteed.

[0049] In this embodiment, the lower end of the closed bottom cover 11 is connected to a discharge port 17, and the discharge port 17 is connected to a discharge valve 18; a circulation port 19 is provided on one side of the closed bottom cover 11, and a circulation valve 20 is connected to the circulation port 19; the discharge valve 18 is connected to a frequency converter pump 22 via a first conveying pipeline 21, and the frequency converter pump 22 is connected to a discharge pipeline 23; the discharge pipeline 23 is connected to the circulation valve 20 via a second conveying pipeline 24; a circulation control valve 25 is provided on the second conveying pipeline 24.

[0050] Specifically, the material settling in the settling tank 1 is agitated at the bottom by the energy provided by the stirring shaft 6, which changes the rheological properties of the bottom slurry, reduces its viscosity, and improves its flowability to prevent blockage. The material output from the discharge port 17 is discharged through the first conveying pipe 21 and the discharge pipe 23. The liquid-solid ratio of the bottom discharge can be automatically adjusted using the second conveying pipe 24, and the circulation valve 20 further prevents the possibility of blockage at the bottom discharge of the settling tank 1.

[0051] In this embodiment, a central well support frame 26 is connected between the side of the central feed well 2 and the inner wall of the settling tank 1; the diameter of the bottom opening of the central feed well 2 is smaller than the maximum outer diameter of the conical guide 8.

[0052] Specifically, the central well support frame 26 serves to fix the central feed well 2, while the conical guide 8 is installed at the lower outlet of the central feed well 2 to change the flow direction of the slurry discharged from the central feed well 2, so as to prevent the slurry from directly rushing into the already formed settling layer and to prevent interference with the settling.

[0053] In one possible embodiment, the closed bottom cover 11 of the settling tank 1 has inclined sides, and these inclined sides form an angle between 30° and 45° with the horizontal plane. An angle of approximately 30° is preferred to provide a good solids flow from the settling cylinder 9.

[0054] In summary, the flocculant-free high-temperature settling device of this invention includes a settling tank 1, with a central feed well 2 inside the settling tank 1; several nozzles 3 are distributed around the edge of the central feed well 2, each nozzle 3 being connected to a feed pipe 4; the outer end of the feed pipe 4 forms a feed inlet 5 extending from the side of the settling tank 1; a stirring shaft 6 is connected to the center of the settling tank 1, extending through the central feed well 2 to the lower part of the settling tank 1; a rake 7 is connected to the lower end of the stirring shaft 6; the stirring shaft 6 has an opening at the bottom of the central feed well 2. A conical guide 8 is connected below the feed pipe. The method of this invention transports the mixture formed by the causticized sodium aluminate solution and the causticized slag after the causticization reaction to the central feed well 2 inside the settling tank 1 through the feed pipe 4. Before the mixture enters the central feed well 2, the energy of the mixture is dispersed through the nozzle 3, reducing the velocity of the mixture entering the central feed well 2 to no more than 1 m / s. This reduces the disturbance to the settling material inside the settling tank 1 during the feeding process without adding flocculants. This invention utilizes the temperature of the high-temperature mixture itself, eliminating the need for cooling and depressurization operations and the addition of flocculants or other settling agents. It allows for direct and rapid settling, reducing production costs, preventing organic flocculants from entering the production system and causing organic pollution of the production materials, and reducing energy consumption.

[0055] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0056] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A flocculant-free high-temperature sedimentation method, characterized in that: The flocculant-free high-temperature settling equipment includes a settling tank (1), with a central feed well (2) inside the settling tank (1); several nozzles (3) are distributed around the edge of the central feed well (2), and each nozzle (3) is connected to a feed pipe (4); the outer end of the feed pipe (4) forms a feed inlet (5) extending from the side of the settling tank (1); a stirring shaft (6) is connected to the center of the settling tank (1), and the stirring shaft (6) extends through the central feed well (2) to the lower part of the settling tank (1); a rake (7) is connected to the lower end of the stirring shaft (6); a conical guide (8) is connected to the stirring shaft (6) below the bottom opening of the central feed well (2). The mixture of sodium aluminate solution after causticization reaction and causticization slag is transported through a feed pipe to the central feed well inside the settling tank. Before the mixture enters the central feed well, the energy of the mixture is dispersed through a nozzle, so that the velocity of the mixture entering the central feed well is reduced to no more than 1 m / s. The nozzle (3) is provided in four parts, and the four nozzles (3) are evenly distributed around the central feed well (2); each nozzle (3) is connected to a feed pipe (4) on its outer side. The diameter of the nozzle (3) near the feed pipe (4) is smaller than the diameter of the nozzle (3) near the center feed well (2); The temperature of the mixture formed by the sodium aluminate solution and the causticizing slag after the causticizing reaction is controlled at 150~200℃.

2. The high-temperature sedimentation method without flocculant according to claim 1, characterized in that: The settling tank (1) includes a settling cylinder (9), a closed top cover (10), and a closed bottom cover (11); the closed top cover (10) is formed on the top of the settling cylinder (9), and the closed bottom cover (11) is formed on the bottom of the settling cylinder (9); the settling cylinder (9) is cylindrical, and the closed bottom cover (11) is conical.

3. The high-temperature sedimentation method without flocculant according to claim 2, characterized in that: The top of the closed top cover (10) is connected to a drive motor (12), and the drive end of the drive motor (12) is connected to the top of the stirring shaft (6).

4. The high-temperature sedimentation method without flocculant according to claim 3, characterized in that: The top of the closed top cover (10) is connected to a safety port (13), and the safety port (13) is connected to a safety valve (14). The upper side of the settling cylinder (9) is connected to an overflow port (15), and the overflow port (15) is connected to an overflow regulating valve (16).

5. The high-temperature sedimentation method without flocculant according to claim 4, characterized in that: The lower end of the closed bottom cover (11) is connected to a discharge port (17), and the discharge port (17) is connected to a discharge valve (18); a circulation port (19) is provided on one side of the closed bottom cover (11), and the circulation port (19) is connected to a circulation valve (20). The discharge valve (18) is connected to a variable frequency pump (22) via a first conveying pipeline (21), and the variable frequency pump (22) is connected to a discharge pipeline (23); the discharge pipeline (23) is connected to the circulation valve (20) via a second conveying pipeline (24); a circulation control valve (25) is provided on the second conveying pipeline (24).

6. The high-temperature sedimentation method without flocculant according to claim 5, characterized in that: A central well support frame (26) is connected between the side of the central feed well (2) and the inner wall of the settling tank (1); the diameter of the bottom opening of the central feed well (2) is smaller than the maximum outer diameter of the conical guide (8).

7. The high-temperature sedimentation method for flocculant-free sedimentation according to any one of claims 1 to 6, characterized in that: The velocity of the mixture entering the central feed well (2) is reduced to no more than 0.8 m / s.

8. The high-temperature sedimentation method without flocculant according to claim 7, characterized in that: The material settled at the bottom of the settling tank (1) is stirred to change the rheological properties of the settled material, and the liquid-solid ratio of the settled material is adjusted to prevent blockage at the bottom of the settling tank (1).

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