Device for removing sodium oxalate in Bayer process aluminum oxide production process

Abstract

The utility model provides a device for removing sodium oxalate in a Bayer process aluminum oxide production process, and relates to the technical field of aluminum oxide production. The device comprises a reaction system, a seed crystal preparation system and a filtering system which are respectively connected with the reaction system, and an aluminum oxide stock solution system and an ingredient sintering system which are respectively connected with the filtering system, and the seed crystal preparation system comprises a vertical filter press. The method can realize the removal of sodium oxalate in the Bayer process alumina production process, thereby improving the influence of oxalate precipitation in the Bayer process alumina system decomposition process, and enhancing the product quality and production efficiency of Bayer process alumina production.

Description

Technical Field

[0001] The utility model relates to the technical field of alumina production, and more specifically, to a device for removing sodium oxalate in the Bayer process for alumina production. Background Technique

[0002] In the alumina production industry, with the depletion of bauxite resources, the grade of the ore used in the alumina system has gradually decreased, and the types used have increased continuously. Different types of raw ores such as high-sulfur ore, high-carbon ore, and high-titanium ore directly enter the alumina production system. Ores with high organic carbon content entering the alumina production system cause the precipitation of oxalate during the decomposition process, resulting in severely refined particle size of aluminum hydroxide, reduced strength, and increased lattice alkali content; the severely refined product particle size clogs the filter cloth holes of the vertical disk and horizontal disk filters, and the filtering effect rapidly decreases, with high alkali content in the product; a large amount of foam is formed in the decomposition tank, leading to a significant reduction in the production capacity of the intermediate cooling equipment, vertical disk filter, and horizontal disk filter, making it difficult for the system liquid volume to pass through. Content of the Utility Model

[0003] The purpose of the utility model is to provide a device for removing sodium oxalate in the Bayer process for alumina production, which can achieve the removal of sodium oxalate in the Bayer process for alumina production, thereby improving the influence of oxalate precipitation during the decomposition process of the Bayer alumina system and enhancing the product quality and production efficiency of Bayer alumina production.

[0004] The embodiments of the utility model are achieved through the following technical solutions:

[0005] A device for removing sodium oxalate in the Bayer process for alumina production includes a reaction system, a seed preparation system and a filtration system respectively connected to the reaction system, and an alumina stock solution system and a batching and sintering system respectively connected to the filtration system. The seed preparation system includes a vertical filter press.

[0006] Furthermore, the device also includes a caustic soda preparation and addition system, which includes a causticization tank and a salt settling tank connected in sequence, and the salt settling tank is connected to the reaction system.

[0007] Furthermore, the reaction system includes a strong alkali tank, a causticization settling tank and a causticization underflow tank connected in sequence, and the causticization underflow tank is connected to the vertical filter press.

[0008] Furthermore, the device also includes a concentration system, which includes a first-stage evaporator and a second-stage evaporator connected in sequence, and the second-stage evaporator is connected to the reaction system.

[0009] Further, the device further includes a heat exchange system, which includes a mother liquor plate heat exchanger and a water plate heat exchanger connected in sequence; the reaction system includes a strong base tank, and the water plate heat exchanger is connected to the strong base tank.

[0010] Further, the device further includes an aluminum ash active dissolution slag tank, the water plate heat exchanger is also connected to a first decomposition tank, the aluminum ash active dissolution slag tank is connected to the vertical filter press, the vertical filter press is connected to the first decomposition tank, and the first decomposition tank is connected to the strong base tank.

[0011] Further, the filtration system includes a dissolution filter press, and a filtrate tank and a filter cake tank connected to the dissolution filter press. The filtrate tank is connected to the alumina stock solution system, and the filter cake tank is connected to the batching and sintering system.

[0012] The technical solution of the embodiment of the present utility model has at least the following advantages and beneficial effects:

[0013] In the present utility model, the solution in the reaction system forms sodium oxalate after adding flake caustic soda or cooling, and crystal seeds will be formed after a period of time. Part of the crystal seeds are filtered by the crystal seed preparation system to form filter cake crystal seeds. The filter cake crystal seeds include sodium oxalate, alumina and sodium carbonate, and the content of sodium oxalate is about 60%. The other part of the sediment enters the filtration system. At the same time, the filter cake crystal seeds prepared by the crystal seed preparation system can be re-added to the reaction system, and the sodium oxalate in the solution is adsorbed on its surface by using the filter cake crystal seeds to achieve the preliminary removal of sodium oxalate. The reaction system and the crystal seed preparation system cooperate, without adding crystal seeds externally, crystal seeds can be formed during the reaction process, realizing the recycling of crystal seeds, reducing raw material loss and lowering the processing cost. After the reaction, the secondary removal of sodium oxalate is realized through the filtration system. The filter residue after filtration enters the batching and sintering system for sintering, so that the carbon in the filter residue is converted into carbon dioxide and removed. The remaining sodium aluminate after sintering is dissolved in water to form a sodium aluminate solution for recycling. The filtrate enters the alumina stock solution system for utilization. Description of the Drawings

[0014] In order to more clearly illustrate the technical solutions of the embodiments of the present utility model, the following will briefly introduce the drawings required for the embodiments. It should be understood that the following drawings only show some embodiments of the present utility model, and therefore should not be regarded as limiting the scope. For those of ordinary skill in the art, other related drawings can be obtained based on these drawings without creative efforts.

[0015] Figure 1 It is a structural schematic diagram of the device for removing sodium oxalate from the flat plate washing solution provided in Embodiment 1 of the present utility model;

[0016] Figure 2Another schematic structural diagram of the device for removing sodium oxalate from the flat - plate washing liquid provided in Embodiment 2 of the present utility model;

[0017] Figure 3 Schematic structural diagram of the device for removing sodium oxalate from the evaporation mother liquor provided in Embodiment 3 of the present utility model.

[0018] Icon: 1 - Caustic soda preparation and addition system, 2 - Reaction system, 3 - Vertical filter press, 4 - Filtration system, 5 - Alumina stock solution system, 6 - Batching and sintering system, 7 - Concentration system, 8 - Heat - exchange system, 9 - Aluminum ash active dissolution slag tank, 11 - Causticization tank, 12 - Salt sedimentation tank, 21 - Strong alkali tank, 22 - Causticization sedimentation tank, 23 - Causticization underflow tank, 24 - First decomposition tank, 41 - Dissolution filter press, 42 - Filtrate tank, 43 - Filter cake tank, 71 - First - stage evaporator, 72 - Second - stage evaporator, 81 - Mother - liquor plate heat exchanger, 82 - Water plate heat exchanger. Detailed implementation manners

[0019] To make the objectives, technical solutions and advantages of the embodiments of the present utility model clearer, the technical solutions in the embodiments of the present utility model will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present utility model. Obviously, the described embodiments are some but not all of the embodiments of the present utility model. Usually, the components of the embodiments of the present utility model described and illustrated in the accompanying drawings here can be arranged and designed in various different configurations.

[0020] Therefore, the following detailed description of the embodiments of the present utility model provided in the accompanying drawings is not intended to limit the scope of the claimed present utility model, but merely represents the selected embodiments of the present utility model. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present utility model without making creative efforts belong to the scope of protection of the present utility model.

[0021] It should be noted that: Similar reference numerals and letters denote similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0022] In the description of the present utility model, it should be noted that if terms such as "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. are used to indicate the orientation or positional relationship, it is based on the orientation or positional relationship shown in the accompanying drawings or the orientation or positional relationship in which the product of this application is usually placed during use. It is only for the convenience of describing the present utility model and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present utility model.

[0023] In the description of the present utility model, it should also be noted that unless otherwise clearly specified and defined, if the terms "set", "installed", "connected", "coupled" are used, they should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present utility model can be understood according to specific circumstances.

[0024] Embodiment 1

[0025] As Figure 1 shown, this embodiment provides a device for removing sodium oxalate in the Bayer process alumina production process, including a reaction system 2, a seed preparation system and a filtration system 4 respectively connected to the reaction system 2, and an alumina stock solution system 5 and a batching and sintering system 6 respectively connected to the filtration system 4. The seed preparation system includes a vertical filter press 3. Taking the flat plate wash liquor as an example for illustration, the device further includes a caustic soda preparation and addition system 1, and the caustic soda preparation and addition system 1 includes a causticization tank 11 and a salt settling tank 12 connected in sequence, and the salt settling tank 12 is connected to the reaction system 2.

[0026] The caustic soda and the solution are prepared through the caustic soda preparation and addition system 1, and the concentration of the caustic soda is controlled to remove the sodium oxalate in the solution. After the caustic soda reacts with the solution in the reaction system, sodium oxalate is formed. After a period of time, seeds are formed. Part of the seeds are filtered by the seed preparation system to form filter cake seeds. The filter cake seeds include sodium oxalate, alumina and sodium carbonate, and the content of sodium oxalate is about 60%. Another part of the sediment enters the filtration system 4. At the same time, the filter cake seeds prepared by the seed preparation system can be re-added to the reaction system, and the sodium oxalate in the solution is adsorbed on its surface by the filter cake seeds to achieve the preliminary removal of sodium oxalate. The reaction system 2 and the seed preparation system cooperate, without adding seeds externally, and seeds can be formed during the reaction process, realizing the recycling of seeds, reducing raw material loss and lowering the processing cost. After the reaction, the secondary removal of sodium oxalate is achieved through the filtration system 4. The filtered filter residue enters the batching and sintering system 6 for sintering, so that the carbon in the filter residue is converted into carbon dioxide and removed. The remaining sodium aluminate after sintering is dissolved in water to form a sodium aluminate solution for recycling. The filtrate enters the alumina stock solution system 5 for utilization. In other embodiments, the solution can also be flat plate mother liquor or digestion mother liquor.

[0027] Add part of the flat pan washing liquid and caustic soda into the causticization tank 11 for causticization reaction to increase the concentration of caustic soda, and then enter the salt settling tank 12. Control the liquid flow rate through the salt settling tank 12, and let this liquid (with a higher caustic soda concentration) be compounded with another part of the flat pan washing liquid (with a lower caustic soda concentration) in the reaction system 2 at a certain ratio to control the caustic soda concentration, so that the caustic soda concentration in the reaction system 2 is more conducive to the precipitation of sodium oxalate in the flat pan washing liquid, and improve the removal effect of sodium oxalate.

[0028] In this embodiment, the reaction system 2 includes a strong alkali tank 21, a causticization settling tank 22 and a causticization underflow tank 23 connected in sequence, and the causticization underflow tank 23 is connected to the vertical filter press 3. Among them, the salt settling tank 12 is connected to the strong alkali tank 21. Compound part of the flat pan washing liquid and the causticized flat pan washing liquid in the strong alkali tank 21 at a certain ratio to control the caustic soda concentration in the strong alkali tank 21, thereby controlling the removal effect of sodium oxalate. After the reaction in the strong alkali tank 21, it enters the causticization settling tank 22 for sedimentation to form crystal seeds, and then through the causticization underflow tank 22, the underflow is circulated to increase the solid content. Part of the crystal seeds generated after sedimentation are filtered by the vertical filter press 3 to form filter cake crystal seeds, and the filter cake crystal seeds are added to the strong alkali tank 21 to decompose and remove sodium oxalate by crystal seeds, so that the crystal seeds are self-produced and self-used during the reaction process, realizing the recycling of crystal seeds and reducing the processing cost. Another part of the crystal seeds enters the filtration system 4 for filtration.

[0029] In this embodiment, the filtration system 4 includes a digestion filter press 41, a filtrate tank 42 and a filter cake tank 43 connected to the digestion filter press 41. The filtrate tank 42 is connected to the alumina stock solution system 5, and the filter cake tank 43 is connected to the batching sintering system 6. The digestion filter press 41 is used to separate the filter residue and the filtrate to remove sodium oxalate in the filtrate. The filter residue (filter cake) enters the batching sintering system 6 for sintering, so that the carbon in the filter residue is converted into carbon dioxide and removed. The remaining alumina and sodium oxide after sintering are dissolved in water to form sodium aluminate solution for recycling. The filtrate enters the alumina stock solution system 5 for utilization.

[0030] In this embodiment, the flat pan washing liquid is 20 - 40m 3 / h, the concentration of oxalate ions in the flat pan washing liquid is 3 - 5g / l, the concentration of oxalate ions in the filtrate of the digestion filter press 41 is 0.8 - 1.5g / l, and the filter cake amount is 1 - 4t / d; the discharge rate of oxalate ions reaches more than 50%.

[0031] Example 2

[0032] As Figure 2 shown, the difference between this embodiment and Embodiment 1 is that the device further includes a concentration system 7. The concentration system 7 includes a primary evaporator 71 and a secondary evaporator 72 connected in sequence, and the secondary evaporator 72 is connected to the reaction system 2. Among them, the secondary evaporator 72 is connected to the strong alkali tank 21.

[0033] By concentrating the flat plate washing liquid, the caustic soda concentration in the flat plate washing liquid can be increased, thereby reducing the amount of flake caustic soda added in the process and lowering the raw material cost. In addition, the oxalate ion concentration in the flat plate washing liquid can be increased, the treatment amount of oxalate ions per unit time can be increased, and the removal rate of sodium oxalate can be accelerated. The cooperation of the primary evaporator 71 and the secondary evaporator 72 can accelerate the concentration speed.

[0034] In this embodiment, the flat plate washing liquid is 20 - 70 m 3 / h, the oxalate ion concentration of the flat plate washing liquid is 3 - 5 g / l, the oxalate concentration of the filtrate of the dissolution filter press 41 is 0.8 - 1.5 g / l, and the filter cake amount is 2 - 6 t / d; the discharge rate of oxalate ions reaches more than 50%.

[0035] Example 3

[0036] As Figure 3 shown, taking the evaporation mother liquor as an example for illustration, the device of this embodiment includes a reaction system 2, a seed preparation system and a filtration system 4 respectively connected to the reaction system 2, and an alumina stock solution system 5 and a batching and sintering system 6 respectively connected to the filtration system 4. The seed preparation system includes a vertical filter press 3. The device further includes a heat exchange system 8, and the heat exchange system 8 includes a mother liquor plate heat exchanger 81 and a water plate heat exchanger 82 connected in sequence; the reaction system 2 includes a strong alkali tank 21, and the water plate heat exchanger 82 is connected to the strong alkali tank 21. The evaporation mother liquor is initially cooled by the mother liquor plate heat exchanger 81, and is secondarily cooled by the water plate heat exchanger 82. Moreover, the evaporated water of the water plate heat exchanger 82 can be recycled, so that the temperature of the evaporation mother liquor is reduced to about 50°C, and the removal effect of sodium oxalate is controlled by controlling the reaction temperature.

[0037] In this embodiment, the device further includes an aluminum ash active dissolution slag tank 9. The water plate heat exchanger 82 is further connected to a decomposition first tank 24. The aluminum ash active dissolution slag tank 9 is connected to the vertical filter press 3, the vertical filter press 3 is connected to the decomposition first tank 24, and the decomposition first tank 24 is connected to the strong alkali tank 21. Since the sodium oxalate formed simply has poor filtration effect, while the aluminum ash active dissolution slag is a slag formed at high temperature with smaller pore size. When added to the solution, a filter cake layer will be quickly formed during pressure filtration, enhancing the filtration effect of sodium oxalate and increasing the pressure filtration output. In addition, through the compounding of aluminum ash active dissolution slag and seeds, an aluminum ash active dissolution slag - sodium oxalate composite seed is formed by the vertical filter press 3. The composite seed is added to the decomposition first tank 24 for seed decomposition, so that sodium oxalate is adsorbed on the surface of the composite seed, realizing the removal of sodium oxalate. Subsequently, pressure filtration is carried out by the dissolution filter press 41 to realize the removal of the remaining sodium oxalate and improve the sodium oxalate removal effect.

[0038] In this embodiment, the removal of sodium oxalate is achieved by regulating the temperature of the evaporation mother liquor and adding seeds, without the need to add additional raw materials, thereby reducing the processing cost. The filtrate of the vertical filter press 3 can be returned to the mother liquor plate heat exchanger 81 to exchange heat with the evaporation mother liquor, thereby cooling the evaporation mother liquor.

[0039] In this embodiment, the evaporation mother liquor is 330 m 3 / h, the concentration of oxalate ions in the evaporation mother liquor is 1.4 - 1.8 g / l, the concentration of oxalate ions in the filtrate of the dissolution filter press 41 is 0.8 - 1.2 g / l, the filter cake amount is 2.8 t / d, and the discharge rate of oxalate ions reaches over 25%.

[0040] The working principle of a device for removing sodium oxalate in the Bayer process for alumina production is as follows: The amount of caustic soda is controlled by the caustic soda dispensing and adding system 1, and caustic soda and solution are added to the reaction system 2 in a certain proportion. After reacting for a period of time, seeds are formed. Part of the seeds are made into filter cake seeds through the seed preparation system, and the filter cake seeds are re-added to the reaction system 2 for seed decomposition to adsorb sodium oxalate; another part of the seeds are filtered through the filtration system 4, the filter residue after filtration enters the batching and sintering system 6 for sintering to remove carbon, and the filtrate enters the alumina stock solution system 5 for utilization.

[0041] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. An apparatus for removing sodium oxalate in the Bayer process for alumina production, characterized in that: It includes a reaction system, a seed preparation system and a filtration system respectively connected to the reaction system, and an alumina stock solution system and a batching and sintering system respectively connected to the filtration system. The seed preparation system includes a vertical filter press; The reaction system includes a strong alkali tank, a causticization settling tank and a causticization underflow tank connected in sequence. The causticization underflow tank is connected to the vertical filter press; It further includes a caustic soda dispensing and adding system. The caustic soda dispensing and adding system includes a causticization tank and a salt settling tank connected in sequence. The salt settling tank is connected to the strong alkali tank.

2. The device for removing sodium oxalate in the Bayer process alumina production process according to claim 1, characterized in that, The device further includes a concentration system. The concentration system includes a first-stage evaporator and a second-stage evaporator connected in sequence. The second-stage evaporator is connected to the reaction system.

3. The device for removing sodium oxalate in the Bayer process alumina production process according to claim 1, characterized in that, The device further includes a heat exchange system. The heat exchange system includes a mother liquor plate heat exchanger and a water plate heat exchanger connected in sequence; The reaction system includes a strong alkali tank. The water plate heat exchanger is connected to the strong alkali tank.

4. The device for removing sodium oxalate in the Bayer process alumina production process according to claim 3, characterized in that, The device further includes an aluminum ash active leaching slag tank. The water plate heat exchanger is also connected to a first decomposition tank. The aluminum ash active leaching slag tank is connected to the vertical filter press. The vertical filter press is connected to the first decomposition tank. The first decomposition tank is connected to the strong alkali tank.

5. The device for removing sodium oxalate in the Bayer process alumina production process according to claim 1, characterized in that, The filtration system includes a digestion filter press, and a filtrate tank and a filter cake tank connected to the digestion filter press. The filtrate tank is connected to the alumina stock solution system. The filter cake tank is connected to the batching and sintering system.

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