Removal system for organic matters in aluminum oxide production process

Abstract

The utility model discloses a system for removing organic matters in an aluminum oxide production process, which comprises a seven-effect falling film evaporation unit, a five-stage self-evaporation unit, a circulating mother liquor tank and a filter, a branch of an evaporation stock solution feeding pipe is connected into a V-effect evaporator and sequentially enters a IV-effect evaporator, a III-effect evaporator, a II-effect evaporator and a I-effect evaporator; one branch of a discharge pipe of the VII-effect evaporator is communicated with the circulating mother liquor tank, the other branch of the discharge pipe of the VII-effect evaporator is communicated with the VI-effect evaporator and enters the VII-effect evaporator, the discharge pipe of the I-effect evaporator is communicated with the I-stage flash tank and is connected with the II-stage flash tank, the III-stage flash tank, the IV-stage flash tank and the V-stage flash tank, and the V-stage flash tank is communicated with the circulating mother liquor tank; and a filtrate outlet of the filter is communicated with the circulating mother liquor tank. Through cross-flow evaporation of the V-effect evaporator and the VI-effect evaporator, the sodium aluminate solution is rapidly evaporated at low temperature and low pressure, oxalate is rapidly crystallized and separated out, and the device is simple in process, low in investment, low in operation cost and good in field working environment.

Description

Technical Field

[0001] The utility model relates to the technical field of aluminum oxide production, in particular to a system for removing organic matter in the aluminum oxide production process. Background Art

[0002] At present, the production method of alumina in my country mainly adopts the Bayer process production technology. In the process of alumina production, due to the organic matter brought into the ore, especially when imported bauxite is used, the organic matter accumulates continuously in the process, and the organic matter in the sodium aluminate solution produced by alumina is mainly in the form of oxalate. The impact of oxalate on the production system mainly includes: the surface of the decomposition tank, the circulating mother liquor tank, the desiliconization tank and other tanks have a lot of foam; the scaling of heat exchange equipment such as evaporators and decomposition tank intermediate cooling equipment is accelerated, and the heat exchange efficiency is sharply reduced; the particle size of alumina products is refined, and the wear index of alumina products is poor; the decomposition rate and circulation efficiency are reduced, etc., which have a great impact on the organization of alumina production. Therefore, how to efficiently and cost-effectively eliminate the impact of oxalate in sodium aluminate solution on alumina production is still a key issue to be solved in the alumina industry.

[0003] The existing methods of removing organic matter from alumina mainly include activated carbon adsorption and crystallization. The activated carbon adsorption method is to mix fly ash with sodium aluminate solution, combine organic matter with the pores on the surface of activated carbon, and then filter the mixed solution. The filtrate is returned to the production system for use, and the filter cake (liquid content is 30-35%) is sent to the power plant boiler for incineration to achieve the purpose of removing organic matter. The crystallization method is to cool a certain concentration of sodium aluminate solution (≦45°C) and add crystal seeds to allow the organic matter (oxalate) in the sodium aluminate solution to be supersaturated and crystallized, and then filtered with a filtering device, and the filtrate is returned to the production system for use. The filter cake can be sold to the outside (mainly depending on the content of vanadium pentoxide V2O5 in oxalate) or treated with lime causticization. The above two methods of removing oxalate both require the addition of more equipment, large investment costs, complex processes and poor on-site working environment, and generally have the defects of high operating costs, low oxalate removal efficiency, and poor production and control stability. Utility Model Content

[0004] The main purpose of the utility model is to overcome the defects of the above-mentioned background technology and provide a system for removing organic matter in the process of aluminum oxide production.

[0005] To achieve the above-mentioned purpose, the utility model proposes a system for removing organic matter in the alumina production process, comprising a seven-effect falling film evaporation unit, a five-stage self-evaporation unit, a circulating mother liquor tank and a filter, wherein the seven-effect falling film evaporation unit is provided with I to VII effect evaporators, the five-stage self-evaporation unit is provided with I to V flash tanks, and the evaporation stock liquid feed pipe is divided into two branches, one of which is connected to the V effect evaporator and then sequentially enters the IV effect evaporator, the III effect evaporator, the II effect evaporator and the I effect evaporator for evaporation, and the other branch is connected to the VI effect evaporator and enters the VII effect evaporator. The discharge pipe of the I-effect evaporator is connected with the feed of the I-stage flash tank. The liquid after the five-effect evaporation enters the I-stage flash tank and sequentially passes through the II-stage flash tank, the III-stage flash tank, the IV-stage flash tank and the V-stage flash tank for five-stage flash evaporation. The discharge pipe of the V-stage flash tank is connected with the circulating mother liquor tank. The discharge pipe of the VII-effect evaporator is divided into two branches, one of which is connected with the circulating mother liquor tank, and the other is connected with the filter. The filtrate outlet of the filter is connected with the circulating mother liquor tank. In the process of producing alumina, cross-current feeding is carried out from the V-effect evaporator and the VI-effect evaporator respectively. When the VII-effect evaporator is in production operation, the vacuum degree of the evaporation system is -90kpa, the discharge temperature is 55-63℃, and the concentration is 235-255g / L. The evaporation rate of the sodium aluminate solution at low temperature and low pressure is accelerated, thereby increasing the concentration of oxalate in the sodium aluminate solution, and the oxalate can be quickly crystallized and precipitated. Then, part or all of the discharge from the VII-effect evaporator is led to a filter for filtration to separate oxalate from the sodium aluminate solution, so as to achieve the purpose of quickly discharging oxalate in the sodium aluminate solution.

[0006] The technical solution is further optimized, and further includes a filter feed trough, the outlet of which is connected to the feed port of the filter, and the inlet of which is connected to one of the outlets of the VII-effect evaporator. The feed of the filter is balanced by the filter feed trough to avoid fluctuations in the feed of the filter affecting the filtering effect.

[0007] The technical solution is further optimized, and further includes a filter cake processing device, which is connected to the filter cake outlet of the filter. The filter cake processing device is used for further recycling and processing, thereby reducing production costs.

[0008] Further optimizing the technical solution, the filter cake processing device includes a causticizing tank and a sedimentation washing tank, the inlet of the causticizing tank is connected to the filter cake outlet of the filter, the outlet of the causticizing tank is connected to the sedimentation washing tank, the pipeline connecting the causticizing tank and the filter is connected to a hot water pipe, and the causticizing tank is connected to a lime milk pipe. The purpose of recovering alkali liquor is achieved by causticizing the discharged oxalate with lime, thereby reducing production costs.

[0009] To further optimize the technical solution, a first valve and a second valve are respectively provided on two branches of the evaporation raw liquid feed pipe, the first valve is arranged on the branch connected to the V-effect evaporator, and the second valve is arranged on the branch connected to the VI-effect evaporator.

[0010] To further optimize the technical solution, a third valve and a fourth valve are respectively provided on two branches of the discharge pipe of the VII-effect evaporator, the third valve is arranged on the branch connected to the circulating mother liquor tank, and the fourth valve is arranged on the branch connected to the filter.

[0011] To further optimize the technical solution, the secondary steam outlet of the separation chamber of each effect evaporator in the evaporators from effect I to effect VII is connected to the steam inlet of the heating chamber of the next effect evaporator, the steam inlet of the effect I evaporator is connected to the new steam pipe, and the secondary steam outlet of the effect VII evaporator is connected to the direct contact condenser.

[0012] To further optimize the technical solution, in the flash tanks of stages I to V, the secondary flash steam outlet of the stage I flash tank is connected to the steam inlet of the stage III effect evaporator, the secondary flash steam outlet of the stage II flash tank is connected to the steam inlet of the stage IV effect evaporator, the secondary flash steam outlet of the stage III flash tank is connected to the steam inlet of the stage V effect evaporator, the secondary flash steam outlet of the stage IV flash tank is connected to the steam inlet of the stage VI effect evaporator, and the secondary flash steam outlet of the stage V flash tank is connected to the steam inlet of the stage VII effect evaporator.

[0013] To further optimize the technical solution, the direct contact condenser is connected to a vacuum system.

[0014] To further optimize the technical solution, the direct contact condenser is connected with a water seal groove.

[0015] The beneficial effects of the utility model include: by adopting the removal system to carry out cross-flow feeding evaporation from the V-effect evaporator and the VI-effect evaporator, the vacuum degree of the evaporation system of the VII-effect evaporator during production operation is -90kpa, the discharge temperature of the evaporation mother liquor is 55-63°C, and the concentration is 235-255g / L, the evaporation speed of the sodium aluminate solution under low temperature and low pressure is accelerated, so as to increase the concentration of oxalate in the sodium aluminate solution, and the oxalate can be quickly crystallized and precipitated, and then part or all of the discharge of the VII-effect evaporator is introduced into a filter for filtration, so as to achieve the purpose of efficiently and quickly discharging the oxalate in the sodium aluminate solution, and the process is simple, the investment cost is low, the operation cost is low, and the on-site working environment is good. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a flow chart of a system for removing organic matter in an alumina production process in an embodiment of the utility model.

[0017] Figure 2 It is an overall schematic diagram of a system for removing organic matter in an alumina production process in an embodiment of the utility model.

[0018] Figure 3 It is a schematic diagram of an evaporator in an embodiment of the utility model.

[0019] Figure numerals: 1, I-effect evaporator; 2, II-effect evaporator; 3, III-effect evaporator; 4, IV-effect evaporator; 5, V-effect evaporator; 6, VI-effect evaporator, 7, VII-effect evaporator, 8, I-stage flash tank; 9, II-stage flash tank; 10, III-stage flash tank; 11, IV-stage flash tank; 12, V-stage flash tank; 13, evaporation stock solution feed pipe; 14, circulating mother liquor tank; 15, filter feed tank; 16, filter; 17, causticizing tank; 18, sedimentation washing tank; 19, hot water pipe; 20, lime milk pipe; 21, new steam pipe; 22, direct contact condenser; 23, water seal tank; 24, vacuum system; 25, separation chamber; 26, heating chamber; 27, first valve; 28, second valve; 29, third valve; 30, fourth valve. DETAILED DESCRIPTION

[0020] In order to make the technical problems, technical solutions and beneficial effects to be solved by the embodiments of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0021] It should be noted that when a component is referred to as being "fixed to" or "disposed on" another component, it can be directly on the other component or indirectly on the other component. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or indirectly connected to the other element. In addition, connection can be used for both fixing and circuit connection.

[0022] It should be understood that the terms "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the embodiments of the utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the utility model.

[0023] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the embodiments of the present utility model, the meaning of "multiple" is two or more, unless otherwise clearly and specifically defined.

[0024] See also Figures 1 to 3In one embodiment, a system for removing organic matter in an alumina production process is disclosed, comprising a seven-effect falling film evaporation unit, a five-stage self-evaporation unit, a circulating mother liquor tank 14 and a filter 16, wherein the seven-effect falling film evaporation unit comprises Ⅰ to Ⅶ-effect evaporators, the five-stage self-evaporation unit comprises Ⅰ to Ⅴ-effect flash tanks, and the evaporation stock liquid feed pipe 13 is divided into two branches for feeding, wherein one branch of the evaporation stock liquid feed pipe 13 is connected to the Ⅴ-effect evaporator 5 and then sequentially enters the Ⅳ-effect evaporator 4, the Ⅲ-effect evaporator 3, the Ⅱ-effect evaporator 2 and the Ⅰ-effect evaporator 1 for five-effect evaporation, and the other branch of the evaporation stock liquid feed pipe 13 is connected to the Ⅵ-effect evaporator 5 and then sequentially enters the Ⅳ-effect evaporator 4, the Ⅲ-effect evaporator 3, the Ⅱ-effect evaporator 2 and the Ⅰ-effect evaporator 1 for five-effect evaporation. The liquid enters the fifth-effect evaporator 6 and enters the seventh-effect evaporator 7 for two-effect evaporation. The discharge of the first-effect evaporator 1 is connected with the feed of the first-stage flash tank 8. The liquid after five-effect evaporation enters the first-stage flash tank 8 and sequentially passes through the second-stage flash tank 9, the third-stage flash tank 10, the fourth-stage flash tank 11 and the fifth-stage flash tank 12 for five-stage flash evaporation. The discharge of the fifth-stage flash tank 12 is connected with the circulating mother liquor tank 14. The discharge pipe of the seventh-effect evaporator 7 is divided into two branches, one of which is connected with the circulating mother liquor tank 14, and the other is connected with the filter 16. The filtrate outlet of the filter 16 is connected with the circulating mother liquor tank 14. In this embodiment, during the production of alumina, the feed of the seven-effect falling film evaporator unit is fed from the V-effect evaporator 5 and the VI-effect evaporator 6 in a cross-flow manner. When the VII-effect evaporator 7 is in production operation, the vacuum degree of the evaporation system is -90 kpa, and the outlet temperature of the evaporation mother liquid of the VII-effect evaporator 7 is 55-63°C and the concentration is 235-255 g / L. The evaporation rate of the sodium aluminate solution at low temperature and low pressure is accelerated, thereby increasing the concentration of oxalate in the sodium aluminate solution, and the oxalate is quickly formed. Crystallization, no need to cool down the mother liquor discharged from the VII-effect evaporator 7 and add crystal seeds, no need to stop growing and underflow concentration, part or all of the discharge from the VII-effect evaporator 7 is led to the filter 16 for filtration, oxalate and sodium aluminate solution are separated, so as to achieve the purpose of quickly discharging oxalate in the sodium aluminate solution, and the filtrate obtained after filtration is returned to the circulating mother liquor tank 14 and mixed with the feed liquid after five-effect evaporation and five-stage flash evaporation, so as to avoid the heat loss caused by cooling the sodium aluminate solution discharged from the VII-effect evaporator 7. By adopting this removal system to remove organic matter, not only the removal efficiency is high, but also the discharge concentration of the seven-effect falling film evaporator unit will not be affected. Compared with the crystallization method or activated carbon adsorption method used in traditional alumina plants, its process is simpler, the investment cost is low, the operating cost is low, and the on-site working environment is better.

[0025] In a preferred embodiment, the disclosed system for removing organic matter in the alumina production process further includes a filter feed tank 15, the outlet of the filter feed tank 15 is connected to the feed port of the filter 16, and the inlet of the filter feed tank 15 is connected to the discharge of one branch of the VII effect evaporator 7. The filter feed tank 15 is provided between the filter 16 and the discharge of the VII effect evaporator 7 to balance the feed of the filter 16 and avoid feed fluctuations affecting the filtering effect.

[0026] In a preferred embodiment, the disclosed system for removing organic matter in the alumina production process further includes a filter cake treatment device, which is connected to the filter cake outlet of the filter 16. The filter cake (oxalate) separated by filtration in the filter 16 is further recycled and treated by the filter cake treatment device to avoid direct discharge and pollution of the on-site environment.

[0027] In a specific example, the filter cake processing device includes a causticizing tank 17 and a sedimentation washing tank 18. The inlet of the causticizing tank 17 is connected to the filter cake outlet of the filter 16, and the outlet of the causticizing tank 17 is connected to the sedimentation washing tank 18. A hot water pipe 19 is connected to the pipeline connecting the causticizing tank 17 and the filter 16, and a lime milk pipe 20 is connected to the causticizing tank 17. The purpose of recovering alkali liquor is achieved by causticizing the discharged oxalate with lime, thereby reducing production costs.

[0028] In a preferred embodiment, a first valve 27 and a second valve 28 are respectively provided on two branches of the evaporation stock liquid feed pipe 13. The first valve 27 is arranged on the branch connected to the V-effect evaporator 5, and the second valve 28 is arranged on the branch connected to the VI-effect evaporator 6. The first valve 27 and the second valve 28 are both proportional regulating valves. The first valve 27 and the second valve 28 are arranged to adjust the flow of the evaporation stock liquid on the two branches to enter the V-effect evaporator 5 and the VI-effect evaporator 6 in a cross-flow manner to ensure stable operation of the system.

[0029] In a preferred embodiment, a third valve 29 and a fourth valve 30 are respectively provided on two branches of the discharge pipe of the VII effect evaporator 7. The third valve 29 is arranged on the branch connected to the circulating mother liquor tank 14, and the fourth valve 30 is arranged on the branch connected to the filter 16. The third valve 29 and the fourth valve 30 also adopt proportional regulating valves. By adjusting the valve openings of the third valve 29 and the fourth valve 30, the ratio of the discharge of the VII effect evaporator 7 entering the circulating mother liquor tank 14 and the filter 16 for filtration can be adjusted. When the concentration of oxalate in the sodium aluminate solution discharged from the VII effect evaporator 7 is too high, the amount entering the filter 16 is increased by adjusting the third valve 29 and the fourth valve 30. When the concentration of oxalate is reduced, the filtration amount is reduced to ensure stable operation of the system.

[0030] In a specific example, the secondary steam outlet of the separation chamber 25 of each effect evaporator from the first to seventh effect evaporators is connected to the steam inlet of the heating chamber 26 of the next effect evaporator, the steam inlet of the first effect evaporator 1 is connected to the new steam pipe 21, and the secondary steam outlet of the seventh effect evaporator 7 is connected to the direct contact condenser 22. By making full use of the secondary steam, the evaporation energy consumption is effectively reduced, and the secondary steam generated by the seventh effect evaporator 7 is absorbed by the direct contact condenser 22, so as to accelerate the escape of the secondary steam of the seventh effect evaporator 7 and improve the evaporation efficiency.

[0031] In a specific example, in the flash tanks of stages I to V, the secondary flash steam outlet of the flash tank 8 of stage I is connected to the steam inlet of the third effect evaporator 3, the secondary flash steam outlet of the flash tank 9 of stage II is connected to the steam inlet of the fourth effect evaporator 4, the secondary flash steam outlet of the flash tank 10 of stage III is connected to the steam inlet of the fifth effect evaporator 5, the secondary flash steam outlet of the flash tank 11 of stage IV is connected to the steam inlet of the sixth effect evaporator 6, and the secondary flash steam outlet of the flash tank 12 of stage V is connected to the steam inlet of the seventh effect evaporator 7. By passing the secondary flash steam generated by flash evaporation into the corresponding evaporator 26 as heating steam, the heat of the evaporated raw liquid itself is effectively utilized.

[0032] In a specific example, a vacuum system 24 and a water seal groove 23 are connected to the direct contact condenser 22. The water seal groove 23 serves as a liquid seal for the vacuum system 24. The vacuum system 24 ensures that the vacuum degree of the evaporation system of the VII effect evaporator 7 is maintained at -90 kPa during production operation.

[0033] The above content is a further detailed description of the utility model in combination with specific / preferred embodiments, and it cannot be determined that the specific implementation of the utility model is limited to these descriptions. For ordinary technicians in the technical field to which the utility model belongs, without departing from the concept of the utility model, it can also make several substitutions or modifications to these described embodiments, and these substitutions or modifications should be regarded as belonging to the scope of protection of the utility model. In the description of this specification, the description of the reference terms "an embodiment", "some embodiments", "preferred embodiments", "examples", "specific examples" or "some examples" means that the specific features, structures, materials or characteristics described in combination with the embodiment or example are included in at least one embodiment or example of the utility model. In this specification, the schematic representation of the above terms does not necessarily target the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In the absence of mutual contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples. Although the embodiments of the present invention and their advantages have been described in detail, it should be understood that various changes, substitutions and alterations may be made herein without departing from the scope of protection of the patent application.

Claims

1. A system for removing organic matter in an alumina production process, characterized in that: It includes a seven-effect falling film evaporation unit, a five-stage self-evaporation unit, a circulating mother liquor tank and a filter. The seven-effect falling film evaporation unit is provided with Ⅰ to Ⅶ-effect evaporators, and the five-stage self-evaporation unit is provided with Ⅰ to Ⅴ-effect flash tanks. The evaporation stock liquid feed pipe is divided into two branches, one of which is connected to the Ⅴ-effect evaporator and then enters the Ⅳ-effect evaporator, the Ⅲ-effect evaporator, the Ⅱ-effect evaporator and the Ⅰ-effect evaporator in sequence for evaporation, and the other branch is connected to the Ⅵ-effect evaporator and enters the Ⅶ-effect evaporator for evaporation. The discharge is connected with the feed of the I-stage flash tank. After the five-effect evaporation, the feed liquid enters the I-stage flash tank and sequentially passes through the II-stage flash tank, the III-stage flash tank, the IV-stage flash tank and the V-stage flash tank for five-stage flash evaporation. The discharge of the V-stage flash tank is connected with the circulating mother liquor tank. The discharge pipe of the VII-effect evaporator is divided into two branches, one of which is connected with the circulating mother liquor tank, and the other is connected with the filter. The filtrate outlet of the filter is connected with the circulating mother liquor tank.

2. The system for removing organic matter in the alumina production process according to claim 1, characterized in that: It also includes a filter feed trough, the outlet of which is communicated with the feed port of the filter, and the inlet of which is communicated with one of the outlets of the VII-effect evaporator.

3. The system for removing organic matter in the alumina production process according to claim 2, characterized in that: It also includes a filter cake processing device, which is communicated with the filter cake outlet of the filter.

4. The system for removing organic matter in the alumina production process according to claim 3, characterized in that: The filter cake processing device includes a causticizing tank and a sedimentation washing tank. The inlet of the causticizing tank is connected to the filter cake outlet of the filter, and the outlet of the causticizing tank is connected to the sedimentation washing tank. A hot water pipe is connected to the pipeline connecting the causticizing tank and the filter, and a lime milk pipe is connected to the causticizing tank.

5. The system for removing organic matter in the alumina production process according to claim 1, characterized in that: The two branches of the evaporation raw liquid feed pipe are respectively provided with a first valve and a second valve, wherein the first valve is arranged on the branch connected to the V-effect evaporator, and the second valve is arranged on the branch connected to the VI-effect evaporator.

6. The system for removing organic matter in the alumina production process according to claim 1, characterized in that: A third valve and a fourth valve are respectively disposed on two branches of the discharge pipe of the VII-effect evaporator. The third valve is disposed on the branch connected to the circulating mother liquid tank, and the fourth valve is disposed on the branch connected to the filter.

7. The system for removing organic matter in the alumina production process according to claim 1, characterized in that: The secondary steam outlet of the separation chamber of each effect evaporator in the evaporators from effect I to effect VII is connected to the steam inlet of the heating chamber of the next effect evaporator, the steam inlet of the effect I evaporator is connected to the new steam pipe, and the secondary steam outlet of the effect VII evaporator is connected to the direct contact condenser.

8. The system for removing organic matter in the alumina production process according to claim 7, characterized in that: In the flash tanks of stages I to V, the secondary flash steam outlet of the stage I flash tank is communicated with the steam inlet of the stage III effect evaporator, the secondary flash steam outlet of the stage II flash tank is communicated with the steam inlet of the stage IV effect evaporator, the secondary flash steam outlet of the stage III flash tank is communicated with the steam inlet of the stage V effect evaporator, the secondary flash steam outlet of the stage IV flash tank is communicated with the steam inlet of the stage VI effect evaporator, and the secondary flash steam outlet of the stage V flash tank is communicated with the steam inlet of the stage VII effect evaporator.

9. The system for removing organic matter in the alumina production process according to claim 8, characterized in that The direct contact condenser is connected with a vacuum system.

10. The system for removing organic matter in the alumina production process according to claim 9, characterized in that: The direct contact condenser is connected with a water seal groove.

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