A process and system for producing mixed salt from aluminum oxide

Abstract

The invention discloses a process and system for mixed desalting in alumina production. The process comprises the following steps: sodium carbonate slurry for strong desalting is introduced into a sedimentation tank for sedimentation separation alone, and the overflow clear liquid after sedimentation flows to a strong alkali liquid tank by gravity, and the bottom flow sodium carbonate slurry after sedimentation is mixed with sodium carbonate slurry for alkali desalting and introduced into a mixer, and the sodium carbonate liquid mixed in the mixer enters a desalting filter device for filtration and separation, and the solid sodium carbonate filtered by the desalting filter device is dissolved in water and enters a causticizing system, and the filtrate after the desalting is filtered flows by gravity into the strong alkali liquid tank. The invention solves the technical problem that the sodium carbonate particles for alkali desalting are fine and difficult to be sedimented and separated, resulting in a large amount of sodium carbonate fine particles being entrained in the overflow of the salt sedimentation tank, causing low desalting efficiency, and can ensure that the desalting filter system does not operate under overload, thereby achieving the purpose of increasing the desalting amount of the system.

Description

Technical Field

[0001] The invention relates to a process for mixed salt removal in aluminum oxide production and a system thereof, belonging to the technical field of aluminum oxide production. Background Art

[0002] In the existing alumina production process, in order to ensure the salt removal effect of the salt removal system, the applicant linked the alkali salt removal system and the forced effect salt removal system to remove salt, and finally the sodium carbonate solution obtained by the alkali salt removal and the forced effect salt removal was precipitated together, filtered and causticized.

[0003] During this process, the applicant discovered that although the existing linked salt removal can improve the salt removal effect, during sedimentation separation, some sodium carbonate is difficult to settle, and the filtration separation effect is poor, resulting in the overflow of the salt sedimentation tank carrying a large amount of sodium carbonate particles, causing a large amount of sodium carbonate to return to the production process, reducing the system's salt removal efficiency, making it difficult to balance the system's sodium carbonate concentration, and even affecting the stable operation of the entire alumina production system. More importantly, the existing technology has failed to truly explore the true effect of the alkali-enhanced linked salt removal.

[0004] That is, a process and system for mixed desalination of alumina production is needed, which can solve the problem that the fine particles of sodium carbonate in the desalination of alkali are difficult to settle and separate and return to the system process, affecting the operation of the system. Summary of the invention

[0005] In view of this, the purpose of the present invention is to provide a process and system for mixed salt removal in alumina production, which can make full use of mixed salt removal and solve the problem that fine particles of sodium carbonate in alkali salt removal are difficult to settle and separate and return to the system process, affecting the operation of the system; and overcome the shortcomings of the prior art.

[0006] The objective of the present invention is achieved through the following technical solutions:

[0007] The invention discloses a process and system for mixed desalting of alumina production. In the process, sodium carbonate slurry for strong desalting is separately passed into a sedimentation tank for sedimentation separation, and the overflow clear liquid after sedimentation is directly transported to a strong alkali liquid tank, and the highly concentrated sodium carbonate slurry after sedimentation is passed into a mixer together with the sodium carbonate slurry for alkali desalting through the underflow, the sodium carbonate slurry mixed by the mixer enters a desalting filter device for filtration separation, the sodium carbonate solid matter filtered by the desalting filter device is dissolved in water and then enters a causticizing system, and the filtrate filtered by the desalting filter device flows by gravity into the strong alkali liquid tank.

[0008] The mixed salt removal system for alumina production comprises a mixed salt removal alkali removal device and a forced alkali removal device, wherein both the alkali removal device and the forced alkali removal device are provided with a feed pipe, a sodium carbonate slurry discharge pipe of the forced alkali removal device is connected to a sedimentation tank, an overflow pipe and an underflow pipe are respectively provided on the sedimentation tank, the overflow pipe is connected to a strong alkali liquid tank, the underflow pipe and the sodium carbonate slurry discharge pipe of the alkali removal device are both connected to a mixer, a discharge pipe is provided on the mixer, the discharge pipe is connected to a salt removal filter, a filtrate discharge pipe of the salt removal filter is connected to a strong alkali liquid tank, and a sodium carbonate discharge pipe of the salt removal filter is connected to a causticizing system.

[0009] As mentioned above, both the underflow pipe and the discharge pipe are provided with a delivery pump.

[0010] As mentioned above, the overflow pipe and the filtrate discharge pipe after salt filtration are connected to the strong alkali liquid tank, and the overflow liquid and the filtrate both flow into the strong alkali liquid tank by gravity.

[0011] As mentioned above, flow meters are provided on the alkali-discharging salt feed pipe, the forced salt discharge feed pipe, the underflow pipe and the discharge pipe.

[0012] Compared with the prior art, the beneficial effects of the present invention are:

[0013] The applicant of the present invention has found that the sodium carbonate particles of alkali-removing salt are fine and difficult to settle and separate, and a large amount of sodium carbonate fine particles are entrained in the overflow liquid after its sedimentation, while the sodium carbonate particles of strong-effect salt removal are relatively coarse and easy to settle and separate, and there are almost no sodium carbonate particles in the overflow liquid after its sedimentation. Utilize this feature, by passing the sodium carbonate slurry of strong-effect salt removal into the sedimentation tank alone for sedimentation separation, and the supernatant after sedimentation is directly overflowed to the strong alkali liquid tank, and the underflow sodium carbonate slurry after sedimentation is highly concentrated and the sodium carbonate slurry of alkali-removing salt is passed into the mixer, and after mixing in the mixer, it enters the salt removal filter device for filtering and separation. In this way, the mixer only adopts the underflow mode, which solves the problem that the overflow carries a large amount of sodium carbonate particles, causing a large amount of sodium carbonate to return. At the same time, the characteristics of strong-effect easy sedimentation and separation can be used to make the sedimentation tank overflow in large quantities, which can reduce the operating load of the salt removal filter device, and at the same time, under the condition that the total overfeed of the salt removal filter is guaranteed to be unchanged, the alkali-removing salt amount can be increased, thereby increasing the system salt removal amount, and achieving a better salt removal effect. Such a process can improve the processing level of the salt removal filtration device and increase the system's salt removal capacity. More importantly, this process has a positive impact on the capacity of the entire system and can process bauxite ores with lower grade and higher carbon content, which is conducive to solving the problem of low-grade, high-carbon content ores that are difficult to process and have low capacity in existing technologies.

[0014] Other advantages, objectives and features of the present invention will be described in the following description to some extent, and to some extent, will be obvious to those skilled in the art based on the following examination and study, or can be taught from the practice of the present invention. The objectives and other advantages of the present invention can be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be further described in detail below with reference to the accompanying drawings, in which:

[0016] Figure 1 It is a schematic diagram of the connection structure of the present invention.

[0017] Among them, there are alkali-removing and salt-removing device 1; strong effect salt-removing device 2; sedimentation tank 3; overflow pipe 4; underflow pipe 5; strong alkali liquid tank 6; mixer 7; discharge pipe 8; salt-removing and filtering device 9; and causticizing system 10. DETAILED DESCRIPTION

[0018] The preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the preferred embodiments are only for illustrating the present invention, rather than for limiting the protection scope of the present invention.

[0019] like Figure 1 As shown, the present invention discloses a process for mixed desalting of alumina production, in which the sodium carbonate slurry for strong desalting is separately introduced into a sedimentation tank 3 for sedimentation separation, and the overflow clear liquid after sedimentation is gravity-flown to a strong alkali liquid tank 6, and the bottom flow sodium carbonate slurry after sedimentation and high concentration and the sodium carbonate slurry for alkali desalting are introduced into a mixer 7, mixed through the mixer 7 and enter a desalting filter device 9 for filtration separation, and the filtrate and sodium carbonate of the desalting filter device 9 are respectively sent to the strong alkali liquid tank 6 and the causticizing system 10.

[0020] The mixed salt removal system for alumina production comprises a mixed salt removal device 1 and a forced salt removal device 2, wherein the mixed salt removal device 1 and the forced salt removal device 2 are provided with a feed pipe, a sodium carbonate slurry discharge pipe of the forced salt removal device 2 is connected to a sedimentation tank 3, an overflow pipe 4 and an underflow pipe 5 are respectively provided on the sedimentation tank 3, the overflow pipe 4 is connected to a strong alkali liquid tank 6, the underflow pipe 5 and the sodium carbonate slurry discharge pipe of the mixed salt removal device 1 are both connected to a mixer 7, a discharge pipe 8 is provided on the mixer 7, the discharge pipe 8 is connected to a salt removal filter 9, a filtrate discharge pipe of the salt removal filter 9 is connected to the strong alkali liquid tank 6, a sodium carbonate discharge pipe of the salt removal filter 9 is connected to a causticizing system 10, a conveying pump is provided on the underflow pipe 5 and the discharge pipe 8, and a flow meter is provided on the feed pipe, the underflow pipe 5 and the discharge pipe 8 of the mixed salt removal device 1 and the forced salt removal.

[0021] After being treated by the mixed salt removal process, the strong alkaline solution is clear and transparent when observed with the naked eye, without the presence of obvious sodium carbonate fine particles suspended, which effectively solves the technical problem of sodium carbonate return.

[0022] The above description is only a preferred embodiment of the present invention and does not constitute any form of confidentiality restriction on the present invention. Any simple modification, equivalent change and modification made to the above embodiment based on the technical essence of the present invention without departing from the technical solution of the present invention still falls within the scope of the technical solution of the present invention.

Claims

1. A process for producing mixed salt from alumina, characterized in that: In the process, the sodium carbonate slurry for strong effective salt removal is separately introduced into a sedimentation tank (3) for sedimentation separation. The overflow clear liquid after sedimentation flows by gravity to a strong alkali solution tank (6). The highly concentrated sodium carbonate slurry after sedimentation is introduced into a mixer (7) together with the sodium carbonate slurry for alkali salt removal through the underflow. The sodium carbonate slurry mixed in the mixer (7) enters a salt removal filter device (9) for filtration separation. The sodium carbonate solid matter filtered by the salt removal filter device (9) is dissolved in water and then enters a causticizing system (10). The filtrate filtered by the salt removal filter device (9) is merged into the strong alkali solution tank (6).

2. A system for mixed desalination of alumina production, comprising a mixed desalination alkali removal device (1) and a forced desalination device (2), wherein both the mixed desalination alkali removal device (1) and the forced desalination device (2) are provided with a feed pipe, characterized in that: The sodium carbonate slurry discharge pipe of the strong alkali removal device (2) is connected to the sedimentation tank (3), and an overflow pipe (4) and an underflow pipe (5) are respectively provided on the sedimentation tank (3), the overflow pipe (4) is connected to the strong alkali liquid tank (6), the underflow pipe (5) and the sodium carbonate slurry discharge pipe of the alkali removal device (1) are both connected to the mixer (7), the mixer (7) is provided with a discharge pipe (8), the discharge pipe (8) is connected to the salt removal filter device (9), the filtrate discharge pipe of the salt removal filter device (9) is connected to the strong alkali liquid tank (6), and the sodium carbonate discharge pipe of the salt removal filter device (9) is connected to the causticizing system (10); Both the underflow pipe (5) and the discharge pipe (8) are provided with a delivery pump; Flow meters are provided on the alkali-discharging salt feed pipe, the forced salt discharge feed pipe, the underflow pipe (5) and the discharge pipe (8).

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