A method for improving the decomposition rate of semen in the production of alumina by the Bayer process

Abstract

The present application relates to the field of alumina, and in particular to a method for improving the decomposition rate of semen in alumina produced by the Bayer process; the method comprises: using a material obtained from a decomposition system in the Bayer process as a raw material, performing multiple continuous grindings until the aluminum hydroxide in the material reaches a preset particle size to obtain active seed crystals; adding the active seed crystals to the mother liquor in the decomposition system for decomposition to improve the decomposition rate of semen; wherein the preset particle size comprises a first preset particle size condition and a second preset particle size condition; the grinding comprises grinding by sand milling; by taking the slurry of the decomposition system itself for re-grinding and then returning it to the decomposition system, while controlling the amount of slurry added after grinding and the seed crystal particle size in the slurry, the decomposition rate of semen can be achieved to be above 52%.

Description

Technical Field

[0001] The present application relates to the field of alumina, and in particular to a method for improving the decomposition rate of semen in alumina produced by the Bayer process. Background Art

[0002] In the Bayer process of producing alumina, the decomposition rate of a large amount of semen in the decomposition system is between 50% and 52%. At the same time, there is an obvious particle size cycle in the current seed separation process. During the particle size coarsening cycle, the production of fine seeds through conventional means such as cooling will have the risk of explosive refinement of the process, and this type of bed cabinet method often has the defect of high crystalline alkali content.

[0003] At present, most alumina plants use the method of mother liquor slurrying and then add seeds from outside the system to refine the seeds. However, this method not only consumes a lot of workers' energy, but also the dry weight of the seeds only accounts for 0.14% of the added seed amount. Therefore, this method has little effect on improving the decomposition rate of semen. Therefore, how to effectively improve the decomposition rate of semen while avoiding explosive refinement of the process is a technical problem that needs to be solved urgently. Summary of the Invention

[0004] The present application provides a method for improving the decomposition rate of semen in the Bayer process for producing alumina, so as to solve the problem in the prior art that the decomposition rate of semen is difficult to be effectively improved while avoiding the risk of explosive refinement of the process.

[0005] In a first aspect, the present application provides a method for improving the decomposition rate of semen in the production of alumina by the Bayer process, the method comprising:

[0006] Using the material obtained from the decomposition system in the Bayer process as raw material, the material is continuously ground multiple times until the aluminum hydroxide in the material reaches a preset particle size to obtain active seed crystals;

[0007] adding the active seed crystals to the mother liquor in the decomposition system for decomposition to increase the decomposition rate of semen;

[0008] Wherein, the preset particle size includes a first preset particle size condition and a second preset particle size condition;

[0009] The grinding includes grinding by sand grinding.

[0010] Optionally, the first preset particle size condition includes that the proportion of aluminum hydroxide particles with a particle size below 45 μm is 10% to 18%.

[0011] Optionally, the second preset particle size condition includes the particle size D50 of aluminum hydroxide being 70 μm to 75 μm.

[0012] Optionally, the addition flow rate of the active seed crystal is 0.5m 3 / h~2m 3 / h.

[0013] Optionally, the grinding is performed ≥2 times.

[0014] Optionally, the sander seeds used for the sanding process have a particle size of 20% to 45% below 45 μm.

[0015] Optionally, the sander seed used for the sanding satisfies D50 of 50 μm to 75 μm.

[0016] Optionally, the feed flow rate of the sand mill seed is 1.8m 3 / h~2.2m 3 / h.

[0017] Optionally, the decomposition time is ≥44h.

[0018] Optionally, the decomposition rate is ≥52.5%.

[0019] The above technical solution provided by the embodiment of the present application has the following advantages compared with the prior art:

[0020] The embodiment of the present application provides a method for improving the decomposition rate of semen in the Bayer process for producing alumina, which uses the material in the decomposition system as raw material and is continuously ground by sand milling. The raw material is subjected to viscosity resistance near the surface of the sand mill blade and moves with the blade, and is thrown to the wall of the sand mill barrel by centrifugal force, forming a double-annular rolling turbulence. The grinding medium density in this area is the largest, thereby enhancing the crushing effect. The crystals collide and squeeze with each other to generate a large number of small active crystal seeds covered with surface active points. When the active crystal seeds are added to the decomposition tank for decomposition, these active crystal seeds can be used to optimize the aluminum hydroxide particle size distribution of the material in the decomposition system while improving the decomposition efficiency of the decomposition system. Under the premise of a stable number of aluminum hydroxide crystal seeds, it can help reduce the crystallization alkali content of the process so that its decomposition rate is above 52%, thereby achieving an effective improvement in the decomposition rate of semen while avoiding the risk of explosive refinement of the process. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0022] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0023] Figure 1A schematic flow chart of a method for increasing the decomposition rate of semen in the Bayer process for producing alumina provided in an embodiment of the present application. DETAILED DESCRIPTION

[0024] To make the purpose, technical solutions, and advantages of the embodiments of this application more clear, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the drawings in the embodiments of this application. Obviously, the described embodiments are part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0025] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0026] like Figure 1 As shown, the embodiment of the present application provides a method for improving the decomposition rate of semen in the production of alumina by the Bayer process, the method comprising:

[0027] S1. The material obtained from the decomposition system of the Bayer process is used as raw material, and the aluminum hydroxide in the material is continuously ground multiple times until the predetermined particle size is reached to obtain active seed crystals;

[0028] S2. Adding the active seed crystals to the mother liquor in the decomposition system to decompose the decomposition to increase the decomposition rate of semen;

[0029] Wherein, the preset particle size includes a first preset particle size condition and a second preset particle size condition;

[0030] The grinding includes grinding by sand grinding.

[0031] In some optional embodiments, the first preset particle size condition includes that the proportion of aluminum hydroxide particles with a particle size below 45 μm is 10% to 18%.

[0032] In the embodiment of the present application, the positive effect of limiting the particle size of aluminum hydroxide below 45 μm to 10% to 18% is that under this particle size condition, the particle size of the aluminum hydroxide seed can be ensured to be small and covered with surface active points, thereby effectively improving the decomposition rate of semen in the subsequent decomposition stage.

[0033] In some optional embodiments, the second preset particle size condition includes the particle size D50 of aluminum hydroxide being 70 μm to 75 μm.

[0034] In the embodiment of the present application, the positive effect of limiting the particle size D50 of aluminum hydroxide to 70μm to 75μm is that under this particle size condition, the particle size of the aluminum hydroxide seed can be ensured to be small and covered with surface active points, thereby effectively improving the decomposition rate of semen in the subsequent decomposition stage.

[0035] In some optional embodiments, the addition flow rate of the active seed crystal is 0.5m 3 / h~2m 3 / h.

[0036] In the embodiment of the present application, the addition flow rate of active seed crystals is limited to 0.5m 3 / h~2m 3 The positive effect of / h is that within this flow rate range, it can cooperate with the process of the decomposition system and use active crystal seeds with small particle size and full of surface active points to ensure that the decomposition rate of the final decomposition system is above 52%.

[0037] In some optional embodiments, the grinding is performed ≥2 times.

[0038] In the embodiment of the present application, the positive effect of limiting the specific number of grinding times is that within the range of the number of times, active seed crystals meeting the expected preset particle size can be ensured to be ground.

[0039] In some optional embodiments, the sander seeds used for the sanding process have a particle size of 20% to 45% below 45 μm.

[0040] In the embodiment of the present application, the positive effect of limiting the sander seeds to meet the particle size of 20% to 45% below 45 μm is that within this particle size range, combined with the sanding method of the sand mill, it can ensure that the aluminum hydroxide crystal seeds obtained by grinding the raw materials meet the preset particle size requirements.

[0041] In some optional embodiments, the sander seed used for the sanding satisfies D50 of 50 μm to 75 μm.

[0042] In the embodiment of the present application, the positive effect of limiting the sander seed to meet the D50 of 50μm to 75μm is that within this particle size range, combined with the sanding method of the sand mill, it can ensure that the aluminum hydroxide crystal seeds obtained by grinding the raw materials meet the preset particle size requirements.

[0043] In some optional embodiments, the addition flow rate of the sand mill seed is 1.8m 3 / h~2.2m 3 / h.

[0044] In the embodiment of the present application, the flow rate of adding the seeds to the sand mill is limited to 1.8m 3 / h~2.2m 3The positive effect of / h is that within the range of this flow rate, the sand mill seeds and the aluminum hydroxide in the raw materials can be completely mixed, thereby ensuring that active crystal seeds with small particle size and full of surface active points are obtained later.

[0045] In some optional embodiments, the decomposition time is ≥44h.

[0046] In the embodiment of the present application, the positive effect of limiting the decomposition time to ≥44h is that it can ensure that semen is fully decomposed and that the decomposition rate of semen is above 52%.

[0047] In some optional embodiments, the decomposition rate is ≥52.5%.

[0048] In the embodiment of the present application, by using the material of the decomposition system as raw material and continuously grinding it, active crystal seeds with fine particle size and covered with surface active points can be obtained, and then added to the decomposition system and mixed with the mother liquor, so as to ensure that the decomposition rate of semen is above 52%.

[0049] The present application will be further described below in conjunction with specific examples. It should be understood that these examples are intended to illustrate the present application only and are not intended to limit the scope of the present application. The experimental methods in the following examples where specific conditions are not specified are usually measured in accordance with national standards. If there are no corresponding national standards, then the methods are carried out in accordance with general international standards, conventional conditions, or according to the conditions recommended by the manufacturer.

[0050] Example 1

[0051] The first decomposition slurry flowing out of the decomposition system is taken as 1# decomposition slurry. This slurry has not been ground. The 1# decomposition slurry is used as raw material and enters the sand mill process for cyclic grinding. When the particle size of aluminum hydroxide in the slurry is below 45μm, accounting for 45%, and D50 is 50.34μm, it enters the decomposition system. The decomposition process conditions are the same as those of the Bayer process. The time is 44h, and the addition flow rate is 0.5m as shown in Experiment 2#, Experiment 3# and Experiment 4#. 3 / h、1m 3 / h、2m 3 / h, and verified the decomposition rate of semen and the change in particle size of decomposition products after adding active seed crystals. The decomposition rate of the obtained semen is shown in Table 1.

[0052] Table 1 Decomposition rate of semen

[0053] Serial number <![CDATA[Addition amount (m 3 / h)]]> <![CDATA[ηAl2O3]]> semen / / Experiment 1# 0 52.55％ Experiment 2# 0.5 52.95％ Experiment 3# 1 53.21％ Experiment 4# 2 53.46％

[0054] The particle size of aluminum hydroxide in the material obtained after decomposition by adding active seed crystals was tested, and the results are shown in Table 2.

[0055] Table 2 Test results of aluminum hydroxide particle size

[0056]

[0057]

[0058] Among them, sand mill seeds are added in the sand mill process (the particle size is below 45μm, accounting for 45%, and D50 is

[0059] 50.34μm), and the addition flow rate is limited to 2m 3 / h, and the final decomposition rate of semen reached more than 53%, and there was no sign of aluminum hydroxide particle size becoming finer during one cycle.

[0060] Example 2

[0061] Comparing Example 2 with Example 1, the difference between Example 2 and Example 1 is:

[0062] The decomposition slurry flowing out of the decomposition system after one cycle in Example 1 is taken as 2# decomposition slurry, which is composed of the decomposition product aluminum hydroxide and the decomposition mother liquor slurry, and the 2# decomposition slurry is used as a raw material to enter the sand mill process. When the particle size of aluminum hydroxide in the slurry is below 45 μm, the proportion is 20.9%, and the D50 is 74.89 μm entering the decomposition system, the decomposition process time is 44h, and the addition amount is 0.5m as shown in Experiment 2#, Experiment 3#, and Experiment 4#, respectively. 3 / h、1m 3 / h、2m 3 / h, and the decomposition rate of the obtained semen is shown in Table 3.

[0063] Table 3 Decomposition rate of semen

[0064] Serial number <![CDATA[Addition amount (m 3 / h)]]> <![CDATA[ηAl2O3]]> semen / / Experiment 1# 0 50.48％ Experiment 2# 0.5 50.83％ Experiment 3# 1 51.01％ Experiment 4# 2 51.32％

[0065] The particle size of aluminum hydroxide in the material obtained after decomposition of the active seed crystals prepared in Example 2 was tested, and the results are shown in Table 4.

[0066] Table 4 Test results of aluminum hydroxide particle size

[0067] category D50(μm) <45μm(%) Flat aluminum hydroxide 81.542 11.34 Experiment 1# 85.787 8.63 Experiment 2# 84.160 9.68 Experiment 3# 84.514 9.73 Experiment 4# 81.542 11.34

[0068] Among them, sand mill seeds (the particle size below 45μm accounts for 20.9%, and D50 is 74.89μm) are added into the sand mill process, and the addition flow rate is limited to 2m 3 / h, the final decomposition rate of semen reached more than 51%, and no particle size refinement was found.

[0069] One or more technical solutions in the embodiments of the present application may have at least the following technical effects or advantages:

[0070] (1) The embodiment of the present application provides a method for improving the decomposition rate of semen in the Bayer process for producing alumina. By taking the slurry of the decomposition system itself and grinding it again, and then returning it to the decomposition system, while controlling the amount of slurry added after grinding and the seed crystal particle size in the slurry, the decomposition rate of semen can be achieved to reach more than 52%.

[0071] (2) The embodiment of the present application provides a method for improving the decomposition rate of semen in the Bayer process for producing alumina, which can not only change the particle size distribution of the seed separation tank, but also provide a continuous, stable and efficient way to add active seed crystals.

[0072] (3) The method for improving the decomposition rate of semen in the Bayer process alumina production provided in the embodiment of the present application is helpful to improve the decomposition rate of the Bayer process system, and the hydrogen aluminum particle size is reasonably distributed, which greatly improves the product quality.

[0073] Various embodiments of the present application may be presented in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity and should not be understood as a hard limitation on the scope of the present application; therefore, the range description should be considered to have specifically disclosed all possible sub-ranges and single numbers within the range. For example, the description of a range from 1 to 6 should be considered to have specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the range, such as 1, 2, 3, 4, 5 and 6, which applies regardless of the range. In addition, whenever a numerical range is indicated herein, it is meant to include any cited number (fractional or integer) within the indicated range.

[0074] In this application, unless otherwise indicated, directional words such as "upper" and "lower" refer specifically to the directions of the drawings in the accompanying drawings. In addition, in the description of this application specification, the terms "including" and "comprising" mean "including but not limited to".

[0075] In this document, relational terms such as "first" and "second" are merely used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply the existence of any such actual relationship or order between these entities or operations. In this document, "and / or" describes the association relationship of associated objects, indicating that three relationships can exist. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. Wherein A and B can be singular or plural. In this document, "at least one" refers to one or more, and "plurality" refers to two or more. "At least one", "at least one of the following" or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, "at least one of a, b, or c", or "at least one of a, b, and c" can all represent: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple.

[0076] The foregoing is merely a list of specific embodiments of the present application, intended to enable those skilled in the art to understand or implement the present application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application is not limited to the embodiments shown herein, but is intended to conform to the broadest scope consistent with the principles and novel features of the present application.

Claims

1. A method for improving the decomposition rate of semen in the production of alumina by the Bayer process, characterized in that: The method comprises: Using the decomposition slurry discharged from the decomposition system of the Bayer process for the first time as raw material, continuously grinding the decomposition slurry several times until the aluminum hydroxide in the decomposition slurry reaches a preset particle size to obtain active seed crystals; adding the active seed crystals to the mother liquor in the decomposition system for decomposition to increase the decomposition rate of semen; Wherein, the preset particle size includes a first preset particle size condition and a second preset particle size condition; The grinding is performed by sand grinding, and sand mill seeds are added during the sand grinding process; The first preset particle size condition includes that the proportion of aluminum hydroxide particles with a particle size below 45 μm is 10% to 18%; The second preset particle size condition includes a particle size D50 of aluminum hydroxide of 70 μm to 75 μm; The addition flow rate of the active seed crystals is 0.5m 3 / h~2m 3 / h; The addition flow rate of the sand mill seeds is 1.8m 3 / h~2.2m 3 / h; The sand mill seeds used in the sand milling process have a particle size of 20% to 45% below 45 μm; The sand mill seed used in the sand grinding satisfies the D50 range of 50 μm to 75 μm; The decomposition rate is ≥52.5%.

2. The method according to claim 1, characterized in that The grinding times are ≥2 times.

3. The method according to claim 1, characterized in that The decomposition time is ≥44h.

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