A device and method for dealkalization of red mud produced in alumina industry

Abstract

The present invention relates to a dealkalization device and method for producing red mud in the alumina industry. The device comprises: at least one mixer; at least one settling tank; wherein the at least one settling tank and the at least one mixer are sequentially connected in series and spaced apart; a dealkalization reaction tank for dealkalizing an underflow, wherein, in the dealkalization reaction tank, lime milk is added to the underflow to obtain a red mud-lime milk mixture, which is then introduced into high-temperature steam for chemical reaction to obtain a red mud residue; the inlet of the dealkalization reaction tank is connected to the outlet of the last settling tank; a filter press for filtering the red mud residue to obtain a filter cake and a filtrate; wherein the inlet of the filter press is connected to the outlet of the dealkalization reaction tank; a red mud storage tank for storing the filter cake; wherein the red mud storage tank is connected to the outlet of the filter press. The device solves the technical problems in the prior art of the traditional lime Bayer process for producing alumina, such as large alumina loss, large alkali loss, and high energy consumption and production cost.

Description

Technical Field

[0001] The present invention relates to the technical field of alumina production, and in particular to a dealkalization device and method for red mud in the production of alumina industry. Background Art

[0002] There are various methods for extracting alumina from ore, including the Bayer process, the soda-lime sintering process, and the Bayer-sintering combined process. The Bayer process has long been the predominant method for producing alumina. Its simple process flow and high product quality have led to its widespread application. According to incomplete statistics, alumina produced using the Bayer process accounts for approximately 95% of the world's total alumina production. The four main steps in the Bayer process are the dissolution of bauxite, the dilution of the sodium aluminate solution, the decomposition of the seed crystals, and the evaporation of the decomposition mother liquor. These four steps are cyclically produced, known as the Bayer cycle. During a Bayer cycle, some alkali is lost due to chemical and mechanical losses. Therefore, the lost alkali must be replenished in the mother liquor to maintain a desired alkali content before the next cycle can begin.

[0003] The traditional lime Bayer process for alumina production primarily involves adding approximately 10% lime during the dissolution process to control the sodium-to-silicon ratio (N / S) of red mud (the sludge obtained after dissolving bauxite) to approximately 0.40, thereby reducing alkali losses during alumina production. While adding lime can reduce alkali losses, it also carries a number of potential hazards, as follows:

[0004] 1. Adding too much lime during the dissolution process will cause a series of complex chemical reactions, including some unnecessary side reactions, such as the generation of hydrated garnet and other residues discharged with the red mud, resulting in increased alumina losses.

[0005] 2. The amount of red mud and the amount of red mud washing water will increase significantly, which will increase the burden of red mud sedimentation and washing, and at the same time increase the energy consumption of the dilution and evaporation processes of various valuable elements in the red mud.

[0006] 3. The calcined lime inevitably contains calcium carbonate, which undergoes decausticization during the bauxite dissolution process, increasing the sodium carbonate concentration in the system, leading to an increase in evaporation and salt discharge, and an increase in the amount of causticization.

[0007] 4. The large amount of lime added and its inability to be recycled increases the cost of alumina production.

[0008] Therefore, in the traditional lime Bayer process of producing alumina, how to reduce the loss of alumina, reduce alkali loss, reduce energy consumption and save production costs is an urgent problem to be solved. Summary of the Invention

[0009] The present invention provides a device and method for dealkalization of red mud in the production of alumina in the alumina industry, so as to solve the technical problems in the prior art of large alumina loss, large alkali loss, high energy consumption and high production cost in the traditional lime Bayer process for producing alumina.

[0010] According to a first aspect of the present invention, there is provided a dealkalization device for red mud produced in the alumina industry, characterized in that it comprises: at least one mixer for mixing red mud to obtain a red mud mixed liquid; at least one settling tank for settling the red mud mixed liquid to obtain an underflow and an overflow, the overflow returning to the mixer to be mixed with the red mud; wherein the at least one settling tank and the at least one mixer are sequentially connected in series and arranged at intervals; a dealkalization reaction tank for dealkalizing the underflow, wherein, in the dealkalization reaction tank, lime milk is added to the underflow to obtain a red mud-lime milk mixed liquid, and then high-temperature steam is introduced to carry out a chemical reaction to obtain a red mud residue; the inlet of the dealkalization reaction tank is connected to the outlet of the last settling tank; a filter press for filtering the red mud residue to obtain a filter cake and a filtrate; wherein the inlet of the filter press is connected to the outlet of the dealkalization reaction tank; a red mud storage tank for storing the filter cake; wherein the red mud storage tank is connected to the outlet of the filter press.

[0011] On the basis of the above technical solution, the present invention can also be improved as follows.

[0012] Furthermore, it also includes: multiple pumps for transporting red mud and mixed liquid; the pumps are respectively arranged between the sedimentation tank and the mixer, between the last sedimentation tank and the dealkalization reaction tank, between the dealkalization reaction tank and the filter press, between the filter press and the mixer, and between the filter press and the red mud storage tank.

[0013] According to another aspect of the present invention, a method for dealkalization of red mud produced in the alumina industry is provided, which is characterized by comprising: subjecting a red mud mixture to at least one sedimentation to obtain an underflow, wherein the underflow is the settled red mud; adding lime milk to the underflow to obtain a red mud-lime milk mixture; passing high-temperature steam into the red mud-lime milk mixture to obtain a red mud residue after reaction; wherein the red mud-lime milk mixture is heated by the high-temperature steam; and filtering the red mud residue to obtain a filter cake and a filtrate.

[0014] On the basis of the above technical solution, the present invention can also be improved as follows.

[0015] Furthermore, adding lime milk to the underflow to obtain the red mud-lime milk mixture includes: adding lime milk to the underflow in a ratio of 1:1 between the content of CaO in the lime milk and the content of SiO2 in the underflow.

[0016] Furthermore, the red mud mixture is subjected to at least one sedimentation to obtain both underflow and overflow, wherein the overflow is a liquid separation after the red mud is settled; and part of the overflow is mixed with the red mud-lime milk mixture.

[0017] Furthermore, the step of sedimentating the red mud mixture at least once to obtain an underflow further comprises: sedimenting the red mud mixture multiple times to obtain a multi-stage underflow; mixing the multi-stage underflow with overflow or water, and continuing sedimentation to finally obtain a settled underflow.

[0018] Furthermore, the red mud mixture is subjected to multiple sedimentation to obtain multi-stage underflow and multi-stage overflow, and the multi-stage overflow is mixed with the multi-stage underflow obtained from the penultimate stage sedimentation before the current sedimentation.

[0019] Furthermore, before the red mud mixed liquor is subjected to the final settling, the method includes: adding water to the bottom flow for mixing with the bottom flow.

[0020] Furthermore, after filtering the red mud residue to obtain filter cake and filtrate, the method further includes: returning the filtrate to be mixed with the underflow.

[0021] Furthermore, after filtering the red mud residue to obtain filter cake and filtrate, the method further includes: transporting the filter cake to a red mud storage tank for storage.

[0022] The present invention provides a dealkalization device and method for red mud in the production of alumina. The method comprises: subjecting a red mud mixture to at least one sedimentation to obtain an underflow, wherein the underflow is the settled red mud; adding lime milk to the underflow to obtain a red mud-lime milk mixture; passing high-temperature steam into the red mud-lime milk mixture to obtain a red mud residue after reaction; wherein the red mud-lime milk mixture is heated by the high-temperature steam; and filtering the red mud residue to obtain a filter cake and a filtrate. The present invention dealkalizes the mud residue (i.e., red mud) obtained after the dissolution of bauxite, and returns the extracted alkali solution to the mother liquor, thereby achieving the purpose of alkali recovery. In addition, the addition of lime milk after the bauxite dissolution process can avoid unnecessary side reactions during the bauxite dissolution process, thereby reducing alumina losses and improving the bauxite dissolution rate. The method solves the technical problems of the conventional lime Bayer process for producing alumina in the prior art, such as large alumina losses, large alkali losses, high energy consumption, and high production costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0024] Figure 1 A process flow chart for dealkalization of red mud in the production of alumina provided by the present invention; and

[0025] Figure 2 A schematic flow chart of a method for dealkalization of red mud in the production of alumina provided by the present invention;

[0026] In the accompanying drawings, the components represented by the reference numerals are as follows:

[0027] First washing sedimentation tank - 101, first mixer - 102, second washing sedimentation tank - 103, second mixer - 104, third washing sedimentation tank - 105, third mixer - 106, fourth washing sedimentation tank - 107, dealkalization reaction tank - 108, filter press - 109, red mud storage tank - 110. DETAILED DESCRIPTION

[0028] In order to make the above and other features and advantages of the present invention more clear, the present invention is further described below with reference to the accompanying drawings. It should be understood that the specific embodiments given herein are for the purpose of explaining to those skilled in the art and are only exemplary and not restrictive.

[0029] In the following description, many specific details are set forth to provide a thorough understanding of the present invention. However, it will be apparent to one of ordinary skill in the art that it is not necessary to adopt the specific details to practice the present invention. In other cases, well-known steps or operations are not described in detail to avoid obscuring the present invention.

[0030] The present invention provides a dealkalization device for producing red mud in the alumina industry, such as Figure 1 As shown, it includes: at least one mixer for mixing red mud to obtain a red mud mixed liquid; at least one sedimentation tank for settling the red mud mixed liquid to obtain an underflow and an overflow, and the overflow is returned to the mixer to be mixed with the red mud; wherein, the at least one sedimentation tank and the at least one mixer are connected in series in sequence and arranged at intervals; a dealkalization reaction tank 108 for dealkalizing the underflow, wherein, in the dealkalization reaction tank 108, lime milk is added to the underflow to obtain a red mud-lime milk mixed liquid, and then high-temperature steam is introduced into the underflow for chemical reaction to obtain a red mud residue; the inlet of the dealkalization reaction tank 108 is connected to the outlet of the last sedimentation tank; a filter press 109 for filtering the red mud residue to obtain a filter cake and a filtrate; wherein, the inlet of the filter press 109 is connected to the outlet of the dealkalization reaction tank 108; a red mud storage tank 110 for storing the filter cake; wherein, the red mud storage tank 110 is connected to the outlet of the filter press 109.

[0031] Specifically, the preferred dealkalization device in this scheme includes: a first wash sedimentation tank 101, a first mixer 102, a second wash sedimentation tank 103, a second mixer 104, a third wash sedimentation tank 105, a third mixer 106, a fourth wash sedimentation tank 107, a dealkalization reaction tank 108, a filter press 109 and a red mud storage tank 110, and the components are connected in series in the order of the above components. The red mud to be settled can be pumped to the first washing sedimentation tank 101 for sedimentation, and the bottom flow after sedimentation flows out from the bottom flow port of the sedimentation tank to obtain the first washing bottom flow; the first washing bottom flow is transported to the first mixer 102, and then mixed with the overflow of the third washing (the liquid mixed liquid flowing out of the overflow port of the third washing sedimentation tank 105), and then enters the second washing sedimentation tank 103 for sedimentation to obtain the second washing bottom flow; the second washing bottom flow is transported to the second mixer 104, and then mixed with the overflow of the fourth washing (the liquid mixed liquid flowing out of the overflow port of the fourth washing sedimentation tank 107), and then enters the third washing Sedimentation occurs in the settling tank 105 to produce a third-wash underflow. The third-wash underflow is then transferred to the third mixer 106, where water is added and mixed. The mixed third-wash underflow enters the fourth-wash settling tank 107 for sedimentation to produce a fourth-wash underflow. The fourth-wash underflow is then transferred to the dealkalization reaction tank 108, where a certain amount of lime milk is added. The lime milk reacts chemically with the fourth-wash underflow in the dealkalization reaction tank 108. During the reaction, a portion of the fourth-wash overflow is transferred to the dealkalization reaction tank 108 to participate in the dealkalization reaction. The post-reaction mixture is then transferred to the filter press 109 for filtration to produce a filtrate containing alkali.

[0032] Compared with the existing technology, this solution changes the traditional addition of lime powder during the bauxite dissolution process to the addition of lime milk after the bauxite dissolves the aluminum iron ore, thus avoiding some unnecessary side reactions caused by the addition of lime powder during the bauxite dissolution process. Because under the dissolution conditions, lime powder will undergo a series of complex chemical reactions with the sodium aluminate mother liquor to produce sodium silicate slag hydrated sodium aluminosilicate and hydrated garnet water and calcium aluminosilicate, which will eventually be discharged with the red mud. In addition, the generation of sodium silicate slag is the main cause of alkali loss during the dissolution process, which not only increases production costs, but also poses a challenge to environmental protection. This solution adopts calcium-free and low-calcium dissolution. The addition of lime milk after dissolution greatly reduces the loss of bauxite due to participation in side reactions, reduces alkali consumption, and reduces waste residue emissions. While reducing production costs, it is also beneficial to environmental protection.

[0033] In a further optional embodiment, it also includes: multiple pumps for transporting red mud and mixed liquid; the pumps are respectively arranged between the sedimentation tank and the mixer, between the last sedimentation tank and the dealkalization reaction tank 108, between the dealkalization reaction tank 108 and the filter press 109, between the filter press 109 and the mixer, and between the filter press 109 and the red mud storage tank 110.

[0034] Specifically, in this scheme, pumps are used to transport underflow, filtrate, etc. Preferably, pumps are provided between the first wash sedimentation tank 101 and the first mixer 102, between the first mixer 102 and the second wash sedimentation tank 103, between the second wash sedimentation tank 103 and the second mixer 104, between the second mixer 104 and the third wash sedimentation tank 105, between the third wash sedimentation tank 105 and the third mixer 106, between the third mixer 106 and the fourth wash sedimentation tank 107, between the fourth wash sedimentation tank 107 and the dealkalization reaction tank 108, between the dealkalization reaction tank 108 and the filter press 109, and between the filter press 109 and the red mud storage tank 110. It should be noted that the pump is also used to transport overflow at each level. Preferably, pumps are also provided between the first mixer 102 and the third wash sedimentation tank 105, between the second mixer 104 and the fourth wash sedimentation tank 107, and between the filter press 109 and the second mixer 104.

[0035] The present invention also provides a method for dealkalization of red mud produced in the alumina industry, such as Figure 2 Shown, including:

[0036] Step S1, sedimenting the red mud mixture at least once to obtain an underflow, wherein the underflow is the settled red mud;

[0037] Specifically, in this solution, the red mud produced during the bauxite dissolution process must undergo at least one settling step before entering the dealkalization process. The purpose of dealkalization is to recover and reuse lost alkali, reducing energy and alkali consumption. In the red mud mixture, the solid component is discharged through the underflow outlet, known as the underflow, while the liquid component is discharged through the overflow outlet, known as the overflow. In a preferred embodiment, the red mud is subjected to four sedimentation steps to obtain an underflow, wherein the red mud is pumped to a first-wash sedimentation tank for sedimentation, and the bottom flow after sedimentation flows out from the bottom flow outlet of the sedimentation tank to obtain a first-wash underflow; the first-wash underflow is conveyed to a first mixer, mixed with the third-wash overflow, and then enters a second-wash sedimentation tank for sedimentation to obtain a second-wash underflow; the second-wash underflow is conveyed to a second mixer, mixed with the fourth-wash overflow, and then enters a third-wash sedimentation tank for sedimentation to obtain a third-wash underflow; the third-wash underflow is conveyed to a third mixer, water is added to the third-wash underflow for mixing, and after the third-wash underflow is mixed with water, enters a fourth-wash sedimentation tank for sedimentation to obtain a fourth-wash underflow.

[0038] Step S3, adding lime milk to the underflow to obtain a red mud-lime milk mixture;

[0039] Specifically, in this solution, a certain amount of lime milk, obtained by lime digestion, is added to the settled red mud (i.e., the fourth wash underflow), and the mixture is fully simmered to obtain a mixture of red mud and lime milk. It should be noted that the lime milk is added to the underflow in a ratio of 1:1, such that the CaO content in the lime milk is equal to the SiO2 content in the underflow.

[0040] Step S5, introducing high-temperature steam into the red mud-lime milk mixture to obtain red mud residue after reaction; wherein the red mud-lime milk mixture is heated by the high-temperature steam;

[0041] Specifically, in this solution, high-temperature steam is continuously introduced into the mixed liquid to heat the mixed liquid, wherein the high-temperature steam can be high-temperature water vapor, and the temperature of the high-temperature steam is maintained at 90-95° C., and the reaction is continued for 2 to 3 hours.

[0042] Step S7: filtering the red mud residue to obtain a filter cake and a filtrate.

[0043] Specifically, in this embodiment, the fully reacted mixed solution is filtered to obtain an alkali-containing filtrate. In a preferred embodiment, the mixed solution is filtered using a filter press to obtain a filtrate and a filter cake, wherein the filter cake is the residue after filtration. The filter cake is finally discharged or used for sintering; the filtrate can be recycled and reused.

[0044] Compared with the existing technology, this solution changes the traditional addition of lime powder during the bauxite dissolution process to the addition of lime milk after the bauxite dissolves the aluminum iron ore, thus avoiding some unnecessary side reactions caused by the addition of lime powder during the bauxite dissolution process. Because under the dissolution conditions, lime powder will undergo a series of complex chemical reactions with the sodium aluminate mother liquor to produce sodium silicate slag hydrated sodium aluminosilicate and hydrated garnet water and calcium aluminosilicate, which will eventually be discharged with the red mud. In addition, the generation of sodium silicate slag is the main cause of alkali loss during the dissolution process, which not only increases production costs, but also poses a challenge to environmental protection. This solution adopts calcium-free and low-calcium dissolution. The addition of lime milk after dissolution greatly reduces the loss of bauxite due to participation in side reactions, reduces alkali consumption, and reduces waste residue emissions. While reducing production costs, it is also beneficial to environmental protection.

[0045] In a further optional embodiment, step S3, adding lime milk to the underflow to obtain the red mud-lime milk mixture includes: adding lime milk to the underflow in a ratio of 1:1 between the content of CaO in the lime milk and the content of SiO2 in the underflow.

[0046] Specifically, in this solution, adding lime milk after the dissolution process effectively avoids the complex side reactions caused by adding lime during the dissolution process, which can lead to significant alumina losses. Furthermore, adding lime milk to the underflow at a ratio of 1:1 between the CaO content in the lime milk and the SiO2 content in the underflow can better control the sodium-silicon ratio (N / S) of the red mud-lime milk mixture. Under the same lime addition conditions as the traditional Bayer process, the sodium-silicon ratio (N / S) is reduced from approximately 0.40 to below 0.25. It should be noted that the sodium-silicon ratio (N / S) can be used to determine the level of alkali consumption in the Bayer process for alumina production: the lower the sodium-silicon ratio (N / S), the lower the alkali consumption.

[0047] Compared with existing technologies, this solution adds lime milk after the dissolution process, effectively avoiding the complex side reactions caused by adding lime during the dissolution process, reducing alumina losses, and effectively controlling the sodium-silicon ratio of the red mud-lime milk mixture, reducing alkali consumption. This not only improves alumina production efficiency but also reduces production costs.

[0048] In a further optional embodiment, in step S1, the red mud mixture is settled at least once to obtain both underflow and overflow, wherein the overflow is a liquid separation after the red mud is settled; and part of the overflow is mixed with the red mud-lime milk mixture.

[0049] Specifically, in this solution, during the sedimentation process, the bulky material is discharged from the sedimentation outlet, referred to as the underflow, while the smaller liquid mixture is discharged from the overflow outlet, referred to as the overflow. Part of the overflow mixes with the mixture of red mud and lime milk, acting as a dilution agent and facilitating further sedimentation.

[0050] In a further optional embodiment, step S1, sedimenting the red mud mixture at least once to obtain an underflow further includes: sedimenting the red mud mixture multiple times to obtain a multi-stage underflow; mixing the multi-stage underflow with overflow or water, and continuing to sediment to finally obtain a settled underflow.

[0051] Specifically, in this solution, the red mud produced during the bauxite dissolution process must undergo at least one sedimentation before entering the dealkalization process. The purpose of dealkalization is to recover and reuse the lost alkali, thereby reducing energy and alkali consumption. In a preferred embodiment, the red mud undergoes four sedimentation steps to obtain an underflow, wherein the red mud is pumped to a first wash sedimentation tank for sedimentation, and the settled underflow flows out of the underflow outlet of the sedimentation tank to obtain a first wash underflow; the first wash underflow is conveyed to a first mixer, mixed with the third wash overflow, and then enters a second wash sedimentation tank for sedimentation to obtain a second wash underflow; the second wash underflow is conveyed to a second mixer, mixed with the fourth wash overflow, and then enters a third wash sedimentation tank for sedimentation to obtain a third wash underflow; the third wash underflow is conveyed to a third mixer, water is added to the third wash underflow for mixing, and after the third wash underflow is mixed with water, it enters a fourth wash sedimentation tank for sedimentation to obtain a fourth wash underflow.

[0052] It should be noted that in another optional embodiment, the red mud can be subjected to two sedimentation steps to obtain an underflow. The red mud is pumped to a first wash sedimentation tank for sedimentation, and the settled underflow flows out of the underflow outlet of the sedimentation tank to obtain a first wash underflow. The first wash underflow is then conveyed to a first mixer for mixing, and then enters a second wash sedimentation tank for sedimentation to obtain a second wash underflow. In other optional embodiments, the red mud can be subjected to three or four or more sedimentation steps.

[0053] In a further optional embodiment, the red mud mixture is subjected to multiple sedimentation to obtain multi-stage underflow and multi-stage overflow, and the multi-stage overflow is mixed with the multi-stage underflow obtained by the penultimate stage sedimentation before the current sedimentation.

[0054] Specifically, in this scheme, in order to further reduce water consumption, the overflow obtained by sedimentation can also be recycled. For example, in multiple (more than three) sedimentation processes, the tertiary overflow can be mixed with the primary underflow, and then transported to the secondary wash sedimentation tank after mixing; the quaternary overflow can be mixed with the secondary wash underflow red mud, and then transported to the tertiary wash sedimentation tank after mixing.

[0055] Compared with the existing technology, this solution fully recycles the overflow obtained from multi-stage sedimentation, returns the overflow to the mixer to mix with the underflow, plays the role of diluting the underflow, and makes the material particles evenly dispersed, which is conducive to further sedimentation. In this process, no additional water is needed to dilute the underflow and disperse the particles, which saves a lot of water resources on the one hand and reduces costs on the other.

[0056] In a further optional embodiment, before subjecting the red mud mixed liquor to the final settling, the method includes: adding water to the bottom flow for mixing with the bottom flow.

[0057] Specifically, in this solution, water can be added to the underflow and mixed evenly before the final sedimentation process of the red mud to avoid the underflow being too dry and affecting further sedimentation. It should be noted that the liquid-to-solid ratio (L / S) after adding water and mixing is about 3.

[0058] In a further optional embodiment, in step S7, after filtering the red mud residue to obtain filter cake and filtrate, the method further includes: returning the filtrate to be mixed with the underflow.

[0059] Specifically, in this scheme, after high-temperature steam is introduced into the mixture of the underflow after red mud sedimentation and lime milk for heating reaction, the mixture after the reaction is filtered to separate the liquid mixture from the solid residue, and the solid residue is discharged or enters the sintering process, and the liquid filtrate is returned to the mixer. It should be noted that the filtrate contains alkali. This scheme re-extracts and recycles the alkali lost during the dissolution process, reducing the amount of alkali supplemented in the Bayer process and thereby reducing the production cost.

[0060] In a further optional embodiment, in step S7, after filtering the red mud residue to obtain a filter cake and a filtrate, the method further includes: transporting the filter cake to a red mud storage tank for storage.

[0061] Specifically, in this solution, high-temperature steam is introduced into the mixture of the underflow from settled red mud and lime milk to initiate a heating reaction. The resulting mixture is then filtered to separate the liquid mixture from the solid residue. The solid residue can then be pumped to a red mud storage tank for storage before being discharged or sent to the sintering process. This solution allows for the recycling of the solid residue, and its orderly discharge is beneficial to the environment.

[0062] The various technical features described above can be combined arbitrarily. Although not all possible combinations of these technical features are described, any combination of these technical features should be considered to be covered by this specification as long as such combination does not conflict.

[0063] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for dealkalization of red mud in the production of alumina industry, characterized in that: include: After the alumina dissolution process, the generated red mud mixed solution is subjected to at least one sedimentation to obtain an underflow, wherein the underflow is the settled red mud; Adding lime milk to the underflow to obtain a red mud-lime milk mixture, comprising: adding the lime milk to the underflow in a ratio of 1:1 between the content of CaO in the lime milk and the content of SiO2 in the underflow; High-temperature steam is introduced into the red mud-lime milk mixture to obtain red mud residue after reaction; wherein the red mud-lime milk mixture is heated by the high-temperature steam; wherein the high-temperature steam is high-temperature water vapor, the temperature of the high-temperature steam is maintained at 90-95° C., and the reaction is continued for 2 to 3 hours; The red mud residue is filtered to obtain a filter cake and a filtrate; the filtrate is returned to the mixer for recycling.

2. The dealkalization method according to claim 1, wherein The red mud mixture is subjected to at least one sedimentation to obtain an underflow and an overflow, wherein the overflow is a liquid separation after the red mud is settled; A portion of the overflow is mixed with the red mud-lime milk mixture.

3. The dealkalization method according to claim 2, wherein The red mud mixture is subjected to at least one sedimentation to obtain an underflow which also includes: The red mud mixture is subjected to multiple sedimentation to obtain a multi-stage underflow; The multi-stage underflow is mixed with overflow or water, and continues to settle to finally obtain the settled underflow.

4. The dealkalization method according to claim 3, wherein The red mud mixture is subjected to multiple sedimentation to obtain multi-stage underflow and multi-stage overflow, and the multi-stage overflow is mixed with the multi-stage underflow obtained by the penultimate stage sedimentation before the current stage sedimentation.

5. The dealkalization method according to claim 1, wherein Before the red mud mixture is subjected to the final settling, the following steps are included: Water is added to the underflow and mixed therewith.

6. The dealkalization method according to claim 1, wherein The red mud residue is filtered to obtain a filter cake and a filtrate, and the method further comprises: The filtrate is returned to mix with the underflow.

7. The dealkalization method according to claim 1, wherein The red mud residue is filtered to obtain a filter cake and a filtrate, and the method further comprises: The filter cake is transported to a red mud storage tank for storage.

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