Confluence system and method for producing aluminum oxide crude liquid through series connection method

Abstract

The invention discloses a converging system and method for aluminum oxide crude liquid produced through a series connection method. The system comprises an after-dilution tank, an after-dilution pump and a leaf filter crude liquid tank which are connected in sequence. An inlet of the after-dilution tank is connected with crude liquid generated in the sintering process through a pipeline, the leaf filter crude liquid tank is connected with a leaf filter in the Bayer process through a pipeline, and the crude liquid generated in the Bayer process is connected with the leaf filter crude liquid tank through a pipeline; the invention provides a novel crude liquid confluence system aiming at the loss of aluminum oxide caused by the hydrolysis of sintering-process crude liquid due to a crude liquid confluence mode in a traditional tandem-process aluminum oxide production process, so that the loss of hydrolyzed aluminum oxide caused by the fact that the sintering crude liquid enters a Bayer-process sedimentation system is avoided, and the production cost is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of improved alumina production systems, and in particular to a system and method for producing alumina crude liquid confluence by a series process. Background Art

[0002] In recent years, due to the rush of various alumina plants to buy high-quality bauxite, the grade of ore supplied to alumina plants has deteriorated year by year, resulting in increased production material and energy consumption, lower output efficiency, and rising costs. For the treatment of low-grade bauxite, according to different bauxite resources and other conditions, the hybrid process, Bayer process, lime Bayer process or series process with their own characteristics can be adopted.

[0003] Among them, the series production process is simpler than the hybrid process. The existing series production process is as follows: Figure 1 As shown in the figure, the sintering method is partially used to recover alumina and sodium oxide in the red mud after dissolution by the Bayer process. The sintering method accounts for a low proportion, has a high alumina recovery rate, low alkali consumption, and low energy consumption. It is an effective method for treating medium and low-grade bauxite. Therefore, it has great advantages and is widely promoted. At the same time, the series alumina production line mixes the sintered crude liquor with the Bayer diluted slurry and enters the sedimentation tank, which is then sent to the controlled filtration after liquid-solid separation. This crude liquor confluence method makes the sintered crude liquor stay in the Bayer process for a long time, and the hydrolysis tendency is strong, resulting in increased alumina loss, which leads to higher production costs. Summary of the invention

[0004] In view of the problems existing in the prior art, the present invention provides a system and method for merging crude liquor for producing alumina by a series process. In view of the fact that the crude liquor merging mode in the traditional series alumina production process leads to hydrolysis of sintering crude liquor and thus causes loss of alumina, the sintering crude liquor is prevented from entering the Bayer process sedimentation system, avoiding the loss of hydrolyzed alumina, thereby reducing production costs.

[0005] The technical solution of the present invention is as follows:

[0006] In a first aspect of the present invention, a system for producing alumina crude liquid by a series process is provided, comprising a post-dilution tank, a post-dilution pump and a leaf filter crude liquid tank connected in sequence; the inlet of the post-dilution tank is connected to the crude liquid produced in a sintering process via a pipeline, the leaf filter crude liquid tank is connected to the leaf filter in the Bayer process via a pipeline, and the crude liquid produced in the Bayer process is connected to the leaf filter crude liquid tank via a pipeline.

[0007] In some embodiments of the present invention, the post-dilution pump includes a first post-dilution pump, a second post-dilution pump and a third post-dilution pump, the first post-dilution pump and the second post-dilution pump are arranged in parallel, and the inlet of the third post-dilution pump is connected to the post-dilution tank bottom flow pipe.

[0008] In some embodiments of the present invention, the inlet pipes of the first dilution pump, the second dilution pump and the third dilution pump are also connected to the alkali solution pipeline.

[0009] In some embodiments of the present invention, the outlet of the third post-dilution pump is connected to the sedimentation tank via a pipeline, and a valve is further provided on the pipeline between the third post-dilution pump and the sedimentation tank.

[0010] In some embodiments of the present invention, a first switching blind plate, a second switching blind plate, a gate valve and a ball valve are sequentially arranged on the pipeline connected to the outlet of the first dilution pump; the first switching blind plate and the second switching blind plate are connected to the leaf filter coarse liquid tank through a first pipeline; and a third switching blind plate is arranged on the first pipeline.

[0011] In some embodiments of the present invention, the second switching blind plate and the gate valve are connected to the leaf filter coarse liquid tank via a second pipeline, and a fourth switching blind plate is provided on the second pipeline.

[0012] In some embodiments of the present invention, the first pipeline and the second pipeline are also connected to the alkali solution tank through an alkali return pipe, and the outlet of the alkali solution tank is connected to the flocculant room pipeline through a pipeline.

[0013] In some embodiments of the present invention, a fifth switching blind plate and a ball valve are sequentially arranged on the pipeline connected to the outlet of the second dilution pump, and the pipeline connected to the outlet of the first dilution pump and the pipeline connected to the outlet of the second dilution pump are connected through a third pipeline, and the third pipeline is connected before the fifth switching blind plate and after the gate valve.

[0014] In some embodiments of the present invention, the post-dilution tank is also connected to the exhaust steam generated during the sintering process to heat the crude liquid.

[0015] In a second aspect of the present invention, a method for producing alumina crude liquor by a series process is provided, comprising:

[0016] The crude liquid produced in the sintering process is diluted and then pumped to mix with the crude liquid produced in the Bayer process. The mixed crude liquid enters the leaf filter for filtration, thereby reducing the residence time of the crude liquid in the Bayer process and reducing the hydrolysis rate.

[0017] Furthermore, after dilution, alkaline solution is introduced into the inlet pipe of the pump to perform regular alkaline cleaning on the pipe.

[0018] One or more technical solutions of the present invention have the following beneficial effects:

[0019] (1) The present invention combines the crude liquor generated in the sintering process with the crude liquor generated in the Bayer process through a merging system. By taking the residence time of the crude liquor from the sintering process in the Bayer process as a breakthrough, the hydrolysis caused by the excessive residence time of the crude liquor and the decrease in the crude liquor temperature is reduced. The merging mode of the crude liquor from the series process is modified to greatly reduce the residence time of the low-temperature, low-αk sintering crude liquor in the Bayer process, thereby reducing the hydrolysis rate.

[0020] (2) The series method for producing alumina crude liquid confluence system provided by the present invention realizes the confluence of crude liquid by setting a post-dilution tank, a post-dilution pump and a leaf filter crude liquid tank, and is also equipped with an alkali washing pipeline. The alkali washing pipeline is used to clean the pipelines in the entire system, which can effectively remove rust, oxides and metal ions such as calcium and magnesium in the pipeline, thereby protecting the inner wall of the pipeline from damage.

[0021] (3) In the series-connected system for producing alumina crude liquid provided by the present invention, the dilution tank is also connected to the exhaust steam generated during the sintering process to heat the crude liquid, thereby avoiding waste of steam from the dilution tank. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic diagram of the crude liquid confluence mode of the series method in the prior art;

[0023] Figure 2 It is a schematic diagram of the crude liquid confluence mode of the series method of the present invention;

[0024] Figure 3 This is a schematic diagram of the combined flow system for producing alumina crude liquor by the series method of the present invention. DETAILED DESCRIPTION

[0025] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0026] Example 1

[0027] In a typical embodiment of the present invention, a system for producing alumina crude liquid by series process is proposed, such as Figure 2 and Figure 3 As shown, it includes a post-dilution tank, a post-dilution pump and a leaf filter coarse liquid tank which are connected in sequence; the inlet of the post-dilution tank is connected to the coarse liquid produced in the sintering process through a pipeline, the leaf filter coarse liquid tank is connected to the leaf filter in the Bayer process through a pipeline, and the coarse liquid produced in the Bayer process is connected to the leaf filter coarse liquid tank through a pipeline.

[0028] Furthermore, the post-dilution pump includes a first post-dilution pump, a second post-dilution pump and a third post-dilution pump, the first post-dilution pump and the second post-dilution pump are arranged in parallel, the inlet of the third post-dilution pump is connected to the bottom flow pipe of the post-dilution tank, and the diluted slurry of the Bayer process flows in the bottom flow pipe of the post-dilution tank, which is used to use the third post-dilution pump to empty the slurry in the tank when isolating the post-dilution tank.

[0029] Furthermore, the inlet pipes of the first dilution pump, the second dilution pump and the third dilution pump are also connected to the alkali solution pipeline. A valve is provided on the inlet pipe of each dilution pump, and the valve on the inlet pipe can be closed during the alkali washing process to ensure that the alkali solution enters the pipeline for cleaning.

[0030] In this embodiment, the outlet of the third post-dilution pump is connected to the sedimentation tank through a pipeline, and a valve is also provided on the pipeline between the third post-dilution pump and the sedimentation tank. The bottom flow of the rear tank is transported to the sedimentation tank for sedimentation through the third post-dilution pump.

[0031] In this embodiment, a first switching blind plate, a second switching blind plate, a gate valve and a ball valve are sequentially arranged on the pipeline connected to the outlet of the first dilution pump; the first switching blind plate and the second switching blind plate are connected to the leaf filter coarse liquid tank through a first pipeline; and a third switching blind plate is arranged on the first pipeline.

[0032] Furthermore, the second switching blind plate and the gate valve are connected to the leaf filter coarse liquid tank via a second pipeline, and a fourth switching blind plate is provided on the second pipeline.

[0033] Furthermore, the first pipeline and the second pipeline are also connected to the alkali solution tank through the alkali return pipe, and the outlet of the alkali solution tank is connected to the flocculant room pipeline through a pipeline, and the alkali solution after alkali washing is collected by the alkali solution tank and transported to the flocculant pipeline room.

[0034] The first post-dilution pump and the second post-dilution pump are connected to the leaf filter crude liquid tank through the first pipeline and the second pipeline, and the first pipeline and the second pipeline are used in turn and in reserve.

[0035] In this embodiment, a fifth switching blind plate and a ball valve are sequentially arranged on the pipeline connected to the outlet of the second dilution pump, and the pipeline connected to the outlet of the first dilution pump and the pipeline connected to the outlet of the second dilution pump are connected through a third pipeline, and the third pipeline is connected before the fifth switching blind plate and after the gate valve.

[0036] In this embodiment, the dilution tank is also connected to the exhaust steam generated during the sintering process to heat the crude liquid and avoid waste of steam from the dilution tank.

[0037] In this embodiment, maintenance platforms are made at all locations where switching blind plates are installed, and vertical steel ladders are installed to facilitate safe operation when switching blind plates later.

[0038] Most of the sodium aluminate solution in the alumina production process is in a supersaturated state, and the crystallization of aluminum hydroxide from the supersaturated sodium aluminate solution is a spontaneous and irreversible process in thermodynamics. If it is not well controlled during the production process, it will cause alumina loss. The main factors affecting the stability of sodium aluminate solution are solution temperature, NK concentration and solution αk. Under the condition that other conditions remain unchanged, the lower the solution αk, the greater the degree of supersaturation, and the lower the stability of the solution. The NK, alumina content (AO), αk of the dissolving solution, and the temperature of the sintering process crude liquor in the series process are 59, 82, 1.18, and 75, respectively, which are relatively low compared to the Bayer process crude liquor and temperature. Therefore, the residence time of the sintering process crude liquor in the Bayer process production process is used as a breakthrough point to reduce the hydrolysis caused by the long residence time of the crude liquor and the decrease in the crude liquor temperature. The transformation of the series process crude liquor confluence mode greatly reduces the residence time of the low-temperature and low-temperature sintering crude liquor in the Bayer process to reduce the hydrolysis rate.

[0039] The working process of the tandem method for producing alumina crude liquid confluence system provided in this embodiment is as follows:

[0040] The crude liquid produced in the sintering process is diluted and then pumped to mix with the crude liquid produced in the Bayer process. The mixed crude liquid enters the leaf filter for filtration, thereby reducing the residence time of the crude liquid in the Bayer process and reducing the hydrolysis rate.

[0041] Furthermore, after dilution, alkaline solution is introduced into the inlet pipe of the pump to perform regular alkaline cleaning on the pipe.

[0042] Specifically, in the preparation process of alumina, the rough liquid generated during the sintering process enters the dilution tank, a valve is connected to the side wall of the dilution tank, and the rough liquid is transported to the rough liquid tank under the action of the first dilution pump and the second dilution pump. During this process, the fifth switching blind plate and the ball valve on the first pipeline outlet pipe are closed, and the first switching blind plate, the second switching blind plate and the gate valve are opened. At the same time, the third switching blind plate and the fourth switching blind plate are selected to open one, one for backup.

[0043] When it is necessary to pass alkali solution into the pipeline for cleaning, the alkali solution enters the inlet pipes of the first dilution pump, the second dilution pump and the third dilution pump respectively through the alkali cleaning pipe, and each valve and the switching blind plate remain in an open state. Part of the alkali solution enters the alkali solution tank through the alkali return pipe, and part of the alkali solution enters the sedimentation tank through the outlet pipe of the dilution pump to complete the alkali cleaning of the pipeline.

[0044] Example 2

[0045] In a typical embodiment of the present invention, a method for producing alumina crude liquor by a series process is proposed, comprising:

[0046] The crude liquid produced in the sintering process is diluted and then pumped to mix with the crude liquid produced in the Bayer process. The mixed crude liquid enters the leaf filter for filtration, thereby reducing the residence time of the crude liquid in the Bayer process and reducing the hydrolysis rate.

[0047] Furthermore, after dilution, alkaline solution is introduced into the inlet pipe of the pump to perform regular alkaline cleaning on the pipe.

[0048] According to the above method, an industrial test was carried out on the series alumina production line, and the test data are shown in Tables 1 to 4:

[0049] Table 1 Semen Nk, semen αk and sedimentation tank temperature two months before transformation

[0050]

[0051]

[0052]

[0053] Table 2 Semen Nk, semen αk and sedimentation tank temperature after transformation

[0054]

[0055]

[0056] Table 3 Dissolution A / S, efflux A / S and A / S difference two months before transformation

[0057]

[0058]

[0059]

[0060] Table 4 Dissolution A / S, efflux A / S and A / S difference after modification

[0061]

[0062]

[0063]

[0064] Table 1-2 proves that the production conditions before and after the transformation are basically the same. As shown in Table 3-4, from April 1 to May 31 before the transformation, the average dissolution rate A / S was 1.06, the average external discharge A / S was 1.15, and the difference in aluminum-silicon ratio was 0.09; from April 8 to July 31 after the transformation, the average dissolution rate A / S was 1.09, the average external discharge A / S was 1.15, and the difference in aluminum-silicon ratio was 0.06. Calculated by output: After the optimization of the △A / S process, the hydrolysis rate decreased by 0.03 compared with the same period in 2021.

[0065] Transformation investment costs and benefits:

[0066] Renovation costs: Investment costs: RMB 489,800 (Construction costs: RMB 271,500, material costs: RMB 218,300, of which seamless steel pipes reused: RMB 356,700)

[0067] Alkali cleaning cost: Alkali cleaning is done once every three months, liquid alkali is fed into the system, each alkali cleaning consumes 10t of steam, alkali cleaning is done 4 times a year, 4*10*170=6800 yuan / year.

[0068] Cost savings after transformation:

[0069] According to the calculation of ore consumption, for every 0.01 reduction in the external A / S, the ore consumption is reduced by 0.007.

[0070] Compared with the A / S difference of 0.09 in April-May 2022, the ore cost is reduced:

[0071] △Mine consumption*ore price=0.021*400 yuan=8.4 yuan.

[0072] Based on an annual output of 930,000 tons, the sintering method collects 60% of the sludge, and the total annual income is:

[0073] 8.4 yuan*930,000 tons of AO (1-60%) = 3.1248 million yuan.

[0074] Ultimate Benefit:

[0075] 312.48-0.68-48.98=2.6282 million yuan.

[0076] Although the above describes the specific implementation mode of the present invention in conjunction with the accompanying drawings, it is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art on the basis of the technical solution of the present invention without creative work are still within the scope of protection of the present invention.

Claims

1. A system for producing alumina crude liquor by series process, characterized in that: It includes a post-dilution tank, a post-dilution pump and a leaf filter coarse liquid tank which are connected in sequence; the inlet of the post-dilution tank is connected to the coarse liquid produced in the sintering process through a pipeline, the leaf filter coarse liquid tank is connected to the leaf filter in the Bayer process through a pipeline, and the coarse liquid produced in the Bayer process is connected to the leaf filter coarse liquid tank through a pipeline.

2. The system for producing alumina crude liquor by series process as claimed in claim 1, characterized in that: The post-dilution pump comprises a first post-dilution pump, a second post-dilution pump and a third post-dilution pump, the first post-dilution pump and the second post-dilution pump are arranged in parallel, and the inlet of the third post-dilution pump is connected to the post-dilution tank bottom flow pipe.

3. The system for producing alumina crude liquor by series process as claimed in claim 2, characterized in that: The inlet pipes of the first dilution pump, the second dilution pump and the third dilution pump are also connected to the alkali solution pipeline.

4. The system for producing alumina crude liquor by serial process as claimed in claim 2, characterized in that: The outlet of the third post-dilution pump is connected to the sedimentation tank through a pipeline, and a valve is also arranged on the pipeline between the third post-dilution pump and the sedimentation tank.

5. The system for producing alumina crude liquor by serial process as claimed in claim 2, characterized in that: The first switching blind plate, the second switching blind plate, the gate valve and the ball valve are sequentially arranged on the pipeline connected to the outlet of the first dilution pump. The first switching blind plate and the second switching blind plate are connected to the leaf filter coarse liquid tank through the first pipeline, and the third switching blind plate is arranged on the first pipeline.

6. The system for producing alumina crude liquor by serial process as claimed in claim 5, characterized in that: The second switching blind plate and the gate valve are connected to the leaf filter coarse liquid tank via a second pipeline, and a fourth switching blind plate is arranged on the second pipeline.

7. The system for producing alumina crude liquor by serial process as claimed in claim 6, characterized in that: The first pipeline and the second pipeline are also connected to the alkali solution tank through the alkali return pipe, and the outlet of the alkali solution tank is connected to the flocculant room pipeline through a pipeline.

8. The system for producing alumina crude liquor by serial process as claimed in claim 5, characterized in that: A fifth switching blind plate and a ball valve are sequentially arranged on the pipeline connected to the outlet of the second dilution pump. The pipeline connected to the outlet of the first dilution pump and the pipeline connected to the outlet of the second dilution pump are connected through a third pipeline. The third pipeline is connected before the fifth switching blind plate and after the gate valve.

9. The system for producing alumina crude liquor by serial process as claimed in claim 1, characterized in that: The post-dilution tank is also connected to the exhaust steam generated during the sintering process to heat the crude liquid.

10. A method for producing alumina crude liquor by a series process, which is implemented by using the system according to any one of claims 1 to 9, characterized in that: include: The crude liquid produced in the sintering process is diluted and then pumped to mix with the crude liquid produced in the Bayer process. The mixed crude liquid enters the leaf filter for filtration, thereby reducing the residence time of the crude liquid in the Bayer process and reducing the hydrolysis rate. Furthermore, after dilution, alkaline solution is introduced into the inlet pipe of the pump to perform regular alkaline cleaning on the pipe.

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