A method of reducing the moisture content of red mud

Abstract

The application relates to the field of solid waste recycling, in particular to a method for reducing the moisture content of red mud; the method comprises the following steps: mixing red mud slurry and a composite additive, and carrying out reaction to obtain reaction slurry; mixing a dispersing additive and the reaction slurry, and carrying out pressure filtration separation to reduce the moisture content of the red mud and obtain low-moisture red mud; the raw material of the composite additive comprises red iron powder and zeolite powder; the dispersing additive comprises sodium tripolyphosphate and / or sodium hexametaphosphate; the crystallization degree of the red mud can be effectively adjusted by adding the composite additive; the addition of the composite additive and the dispersing additive can also reduce the sodium content of the red mud slurry, and sodium oxide products can be recovered, so that the alkali content of the red mud is reduced; therefore, by adding the composite additive and the dispersing additive, the moisture content of the red mud can be reduced, and red mud alkali can be recovered to reduce the production cost of aluminum oxide.

Description

Technical Field

[0001] The present application relates to the field of solid waste recycling, and in particular to a method for reducing the moisture content of red mud. Background Art

[0002] Red mud is a waste product produced in the process of refining alumina from bauxite. It is named for its reddish mud. Red mud is the largest waste product produced in the alumina production process and is also the largest source of pollution in alumina production. With the continuous development of the bauxite industry, the total mass of red mud has an upward trend; because the storage of red mud not only occupies a large amount of land and farmland, consumes a lot of yard construction and maintenance costs, but also the residual alkali liquid in the red mud can penetrate into the ground and cause groundwater pollution, so the best way to deal with it at present is to pile up the red mud or dump it into the deep sea, but the red mud in the yard will form dust, and the dust will fly everywhere, destroying the ecological environment and causing serious pollution. Due to the differences in production methods and bauxite grades, each ton of alumina produced will produce approximately 0.5 to 2.5 tons of red mud, and each ton of red mud is also accompanied by 3m 3 ~4m 3 Alkali-containing wastewater. Depending on the alumina production method, red mud can be divided into three types: sintering process, Bayer process and combined process. However, due to the different abundance of bauxite, the methods adopted for alumina production at home and abroad are also different. Among them, the output of alumina by the Bayer process accounts for more than 90% of the world's total output.

[0003] The Bayer process for producing alumina uses strong alkaline NaOH to dissolve high-aluminum, high-iron bauxite. This results in red mud with high contents of aluminum oxide, iron oxide, and alkali. The bauxite types processed are boehmite and gibbsite. Sintering and combined processes treat insoluble high-silicon, low-iron, diaspore and kaolinite bauxite, producing red mud with high CaO content and low alkali and iron contents. However, the recovery of metallic iron from red mud has not yet been widely applied. Currently, direct reduction ironmaking (DRI) is being tested using Bayer red mud from the Pingguo Aluminum Upper Mine as raw material and coal as a reducing agent. The process involves mixing red mud and coal, forming agglomerates, drying, and then reducing and roasting. Finally, magnetic separation is used to produce sponge iron. Alternatively, high-gradient, high-intensity magnetic separators are used to recover iron from the red mud, but quartz is not obtained, resulting in high investment and operating costs and low recovery rates. This is largely due to the fact that the development of red mud application technologies is largely constrained by issues with red mud alkali and moisture content. Currently, the main research areas for red mud recycling include drying and airing. However, due to the large volume of red mud produced, its composition and properties vary depending on the ore source and production process, and the usable red mud moisture content also varies. Generally, red mud has high moisture content and high viscosity, which makes it thixotropic, making it difficult to dry. Furthermore, processing time is long and utilization is very difficult. Therefore, how to solve the high moisture content of red mud to facilitate its utilization and storage, recover alkali, and reduce alumina costs? Summary of the Invention

[0004] The present application provides a method for reducing the moisture content of red mud to solve the technical problems of high moisture content and high alkali content of red mud in the prior art.

[0005] In a first aspect, the present application provides a method for reducing the moisture content of red mud, the method comprising:

[0006] mixing red mud slurry and composite additives, and reacting them to obtain reaction slurry;

[0007] mixing a dispersing aid and the reaction slurry, and performing filter press separation to reduce the moisture content of the red mud to obtain low-moisture red mud;

[0008] Wherein, the raw materials of the composite auxiliary agent include hematite powder and zeolite powder;

[0009] The dispersing aid includes sodium tripolyphosphate and / or sodium hexametaphosphate.

[0010] Optionally, the mass ratio of the hematite powder to the zeolite powder is 0.5-1:0.5-1.

[0011] Optionally, the mass ratio of the composite additive to the red mud slurry is 1% to 5%.

[0012] Optionally, the mass ratio of the composite additive to the red mud slurry is 2% to 3%.

[0013] Optionally, the medium particle size of the composite additive is 5-30 microns.

[0014] Optionally, the medium particle size of the composite additive is 10-15 microns.

[0015] Optionally, the mass ratio of the dispersing additive to the reaction slurry is 0.1%-1.0%.

[0016] Optionally, the reaction temperature is 70-100 degrees Celsius, and the reaction time is 1-6 hours.

[0017] Optionally, the reaction temperature is 90-100 degrees Celsius.

[0018] Optionally, the filter pressing separation comprises a filter pressing feeding section and a filter pressing pressure section.

[0019] The pressure of the filter pressing feeding section is 0.5-1.5 Mpa, and the pressure of the filter pressing pressure section is 1.0-6.0 Mpa.

[0020] The above technical solution provided by the embodiments of the present application has the following advantages compared with the prior art:

[0021] The method for reducing the moisture content of red mud provided by the embodiments of the present application adds a composite additive and a dispersing additive to the red mud slurry, and limits the composite additive to comprise hematite powder and zeolite powder. The water adsorption of the zeolite powder and the water absorption of the hematite powder can be used to comprehensively improve the water content of the red mud slurry. The main component of the zeolite powder is aluminum silicate, which can form an aluminum hydroxide sol component with the aluminum element of the red mud in the red mud slurry. In combination with the iron element of the hematite powder, the crystallization degree of the red mud can be effectively adjusted. The sodium element in the red mud slurry can also react with the iron element and the aluminum element. Under the action of the dispersing additive, the reaction is sufficient, and sodium oxide products can also be obtained. Therefore, the addition of the composite additive and the dispersing additive can also reduce the sodium content of the red mud slurry and recover the sodium oxide products, thereby reducing the content of red mud alkali. Therefore, by adding the composite additive and the dispersing additive, the moisture content of the red mud can be reduced, and the red mud alkali can be recovered to reduce the production cost of aluminum oxide. BRIEF DESCRIPTION OF DRAWINGS

[0022] 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.

[0023] 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.

[0024] Figure 1 A schematic flow chart of a method for reducing red mud moisture provided in an embodiment of the present application. DETAILED DESCRIPTION

[0025] 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.

[0026] 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.

[0027] like Figure 1 As shown, the embodiment of the present application provides a method for reducing the moisture content of red mud to solve the technical problems of high moisture content and red mud alkali content in the prior art.

[0028] In a first aspect, the present application provides a method for reducing the moisture content of red mud, the method comprising:

[0029] S1. mixing the red mud slurry and the composite additive, and reacting to obtain a reaction slurry;

[0030] S2 mixing a dispersing agent and the reaction slurry, and performing filter press separation to reduce the moisture content of the red mud to obtain low-moisture red mud;

[0031] Wherein, the raw materials of the composite auxiliary agent include hematite powder and zeolite powder;

[0032] The dispersing aid includes sodium tripolyphosphate and / or sodium hexametaphosphate.

[0033] In the embodiments of the present application, the specific raw materials of the composite additive are limited. Since the main component of zeolite powder is aluminum silicate, it can form an aluminum hydroxide sol component with the aluminum element of the red mud in the red mud slurry, which can adjust the crystallization degree of the red mud to a certain extent. Combined with the iron element of the hematite powder, the crystallization degree of the red mud can be further effectively adjusted. In addition, the sodium element in the red mud slurry can also react with the iron element and the aluminum element in the composite additive. Under the action of the sodium phosphate group in the dispersing additive, the reaction is sufficient, and a sodium oxide product can also be obtained.

[0034] It should be noted that the preparation steps of the composite auxiliary agent may be: mixing hematite powder and zeolite powder in required weights in proportion.

[0035] It should be noted that the solid content of the red mud slurry is controlled at 100 g / L to 400 g / L, preferably 150 g / L to 260 g / L.

[0036] The water content of the red mud slurry is generally 45% or above.

[0037] In some optional embodiments, the mass ratio of the hematite powder to the zeolite powder is 0.5-1:0.5-1.

[0038] In the embodiments of the present application, the specific mass ratio of hematite powder and zeolite powder is limited. The degree of crystallization of red mud can be adjusted by combining the aluminum silicate in the zeolite powder with the hematite powder, thereby facilitating the subsequent reaction of sodium, iron and aluminum elements in the red mud slurry to obtain a sodium oxide product, thereby achieving the reduction of moisture in the red mud and the recovery of red mud alkali.

[0039] For example, the mass ratio of the hematite powder to the zeolite powder can be 0.5:0.5, 0.5:0.6, 0.5:0.7, 0.5:0.8, 0.5:0.9, 0.5:1.0, 0.6:0.5, 0.7:0.5, 0.8:0.5, 0.9:0.5, 1.0:0.5, 0.6:0.6, 0.7:0.6, 0.8:0.6, 0.9:0. 6, 1.0:0.6, 0.6:0.7, 0.8:0.7, 0.9:0.7, 1.0:0.7, 0.6:0.8, 0.8:0.8, 0.9:0.8, 1.0:0.8, 0.6:0.9, 0.8:0.9, 0.9:0.9, 1.0:0.9, 0.6:1.0, 0.8:1.0, 0.9:1.0, 1.0:1.0.

[0040] In some optional embodiments, the mass ratio of the composite additive to the red mud slurry is 1% to 5%.

[0041] In some optional embodiments, the mass ratio of the composite additive to the red mud slurry is 2% to 3%.

[0042] In the embodiments of the present application, the specific mass ratio of the composite additive and the red mud slurry is limited, and the degree of crystallization of the red mud can be further adjusted by adding the composite additive, and the subsequent reaction of the sodium element in the red mud slurry with the iron and aluminum elements of the composite additive is facilitated to obtain a sodium oxide product.

[0043] The mass ratio of the composite auxiliary agent to the red mud slurry can be 1%, 2%, 3%, 4% or 5%.

[0044] In some optional embodiments, the median particle size of the composite auxiliary agent is 5 μm to 30 μm.

[0045] In some optional embodiments, the median particle size of the composite auxiliary agent is 10 μm to 15 μm.

[0046] In the embodiments of the present application, by limiting the specific medium particle size of the composite additive, the specific surface area of ​​the composite additive can be clarified. On the one hand, the medium particle size range can allow the composite additive to be fully mixed with the red mud slurry and adjust the degree of crystallization of the red mud. On the other hand, the medium particle size range can allow the sodium element in the red mud slurry to react completely with the iron element and aluminum element of the composite additive, so as to achieve the reduction of moisture in the red mud and the recovery of red mud alkali.

[0047] For example, the median particle size of the composite additive can be 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm,

[0048] 12μm, 13μm, 14μm, 15μm, 16μm, 17μm, 18μm, 19μm, 20μm, 21μm, 22μm, 23μm,

[0049] 24μm, 25μm, 26μm, 27μm, 28μm, 29μm or 30μm.

[0050] In some optional embodiments, the mass ratio of the dispersing aid to the reaction slurry is 0.1% to 1.0%.

[0051] In the embodiments of the present application, the specific mass ratio of the dispersing agent and the reaction slurry is limited. By adding the dispersing agent, under the action of the sodium phosphate group in the dispersing agent, the sodium element in the red mud slurry can fully react with the iron element and the aluminum element in the composite additive, and a sodium oxide product can also be obtained.

[0052] Illustratively, the mass ratio of the dispersing aid to the reaction slurry can be 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9% or 1.0%.

[0053] In some optional embodiments, the reaction temperature is 70° C. to 100° C., and the reaction time is 1 h to 6 h.

[0054] In some optional embodiments, the reaction temperature is 90°C to 100°C.

[0055] In the embodiments of the present application, the specific temperature and specific time of the reaction are limited, so that the reaction between the composite auxiliary agent and the red mud slurry can be complete, the degree of crystallization of the red mud can be adjusted, and the subsequent reaction of the sodium element in the red mud slurry with the iron element and the aluminum element of the composite auxiliary agent to obtain a sodium oxide product can be facilitated to achieve the reduction of moisture in the red mud and the recovery of red mud alkali.

[0056] Illustratively, the temperature of the reaction can be 70°C, 72°C, 74°C, 76°C, 78°C, 80°C, 82°C, 84°C, 86°C, 88°C, 90°C, 92°C, 94°C, 96°C, 98°C or 100°C.

[0057] For example, the reaction time can be 1 h, 2 h, 3 h, 4 h, 5 h or 6 h.

[0058] In some optional embodiments, the filter press separation includes a filter press feed section and a pressing pressure section;

[0059] The pressure of the filter press feed section is 0.5 MPa to 1.5 MPa, and the pressure of the pressing pressure section is 1.0 MPa to 6.0 MPa.

[0060] In the embodiments of the present application, by limiting the specific method of filter press separation, limiting the specific pressure of the filter press feed section, and limiting the specific pressure of the pressing pressure section, the moisture of the red mud can be effectively squeezed out by filter press separation, thereby effectively reducing the moisture of the red mud.

[0061] Illustratively, the pressure of the filter press feed section can be 0.5 MPa, 0.6 MPa, 0.7 MPa, 0.8 MPa, 0.9 MPa, 1.0 MPa, 1.1 MPa, 1.2 MPa, 1.3 MPa, 1.4 MPa or 1.5 MPa.

[0062] Illustratively, the pressure in the pressing pressure section may be 1.0 MPa, 1.5 MPa, 2.0 MPa, 2.5 MPa, 3.0 MPa, 3.5 MPa, 4.0 MPa, 4.5 MPa, 5.0 MPa, 5.5 MPa or 6.0 MPa.

[0063] 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.

[0064] Example 1

[0065] Add 1L of red mud slurry with a solid concentration of 150g / L, 2g of hematite powder and 6g of zeolite powder, control the particle size d50:10μm, control the reaction temperature to 90℃, and react for 2h. After the reaction is completed, add 0.75g of sodium tripolyphosphate and pump it into the filter press. Control the first-stage filter press feed pressure to 1.0Mpa and the second-stage pressing pressure to 2.0Mpa to obtain a red mud moisture content of 24%.

[0066] Example 2

[0067] Add 10 g of zeolite powder and 1 g of hematite powder to 1 L of red mud slurry with a solid concentration of 300 g / L, control the particle size d50:15 μm, control the reaction temperature to 100°C, and react for 6 hours. After the reaction is completed, add 6 g of sodium hexametaphosphate and pump it into a filter press. Control the first-stage filter press feed pressure to 1.2 MPa and the second-stage pressing pressure to 3.0 MPa to obtain a red mud moisture content of 26%.

[0068] Example 3

[0069] Add 1L of red mud slurry with a solid concentration of 200g / L, 5g of zeolite powder and 1.5g of hematite powder, control the particle size d50:13μm, control the reaction temperature to 95°C, and react for 4h. After the reaction is completed, add 3g of sodium hexametaphosphate and pump it into the filter press. Control the first-stage filter press feed pressure to 0.8Mpa and the second-stage pressing pressure to 2.6Mpa to obtain a red mud moisture content of 25%.

[0070] Comparative Example 1

[0071] Add 2 g of hematite powder to 1 L of red mud slurry with a solid concentration of 150 g / L, control the particle size d50: 10 μm, control the reaction temperature to 90°C, and react for 2 h. After the reaction is completed, add 0.75 g of sodium tripolyphosphate and pump it into a filter press. Control the first-stage filter press feed pressure to 1.0 MPa and the second-stage pressing pressure to 2.0 MPa to obtain a red mud moisture content of 27%.

[0072] Comparative Example 2

[0073] Add 10 g of zeolite powder to 1 L of red mud slurry with a solid concentration of 300 g / L, control the particle size d50:15 μm, control the reaction temperature to 100°C, and react for 6 hours. After the reaction is completed, add 6 g of sodium hexametaphosphate and pump it into a filter press. Control the first-stage filter press feed pressure to 1.2 MPa and the second-stage pressing pressure to 3.0 MPa to obtain a red mud moisture content of 28%.

[0074] Comparative Example 3

[0075] Add 1L of red mud slurry with a solid concentration of 200g / L, 5g of zeolite powder and 1.5g of hematite powder, control the particle size d50:13μm, control the reaction temperature to 95℃, and the reaction time to 4h. After the reaction is completed, pump it into the filter press, control the first-stage filter press feed pressure to 0.8Mpa, and the second-stage pressing pressure to 2.6Mpa, and the moisture content of the red mud is 29%.

[0076] Comparative Example 4

[0077] Add 3g of sodium hexametaphosphate to 1L of red mud slurry with a solid concentration of 200g / L, and pump it into the filter press. Control the first-stage filter press feed pressure at 0.8Mpa and the second-stage pressing pressure at 2.6Mpa to obtain a red mud moisture content of 28.5%.

[0078] In summary, the embodiment of the present application provides a method for reducing the moisture content of red mud. Simply by adding a composite additive including hematite powder and zeolite powder, combined with a dispersing additive, the red mud crystallization degree can be improved and the sodium content can be reduced, thereby recovering the sodium oxide product.

[0079] At the same time, this method can reduce the moisture content in red mud by at least 10%, which is beneficial to the storage of red mud.

[0080] At the same time, since this method can treat low-moisture red mud, it is beneficial to the market development of red mud-based products, making the red mud treated by this method highly accepted in the market.

[0081] 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.

[0082] In this application, unless otherwise specified, the directional words used, such as "upper" and "lower", refer specifically to the directions of the drawings in the accompanying drawings. In addition, in the description of the present application specification, the terms "including", "comprising", etc. mean "including but not limited to". In this article, 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 any actual relationship or order between these entities or operations. In this article, "and / or" describes the association relationship of associated objects, indicating that three relationships can exist. For example, A and / or B can mean: 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 article, "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 both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, c can be single or plural, respectively.

[0083] 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 reducing the moisture content of red mud, characterized in that: The method comprises: mixing red mud slurry and composite additives, and reacting them to obtain reaction slurry; mixing a dispersing aid and the reaction slurry, and performing filter press separation to reduce the moisture content of the red mud to obtain low-moisture red mud; Wherein, the raw materials of the composite auxiliary agent include hematite powder and zeolite powder; The dispersing aid includes sodium tripolyphosphate and / or sodium hexametaphosphate.

2. The method according to claim 1, characterized in that The mass ratio of the hematite powder to the zeolite powder is 0.5-1:0.5-1.

3. The method according to claim 1, characterized in that The mass ratio of the composite auxiliary agent to the red mud slurry is 1% to 5%.

4. The method according to claim 3, characterized in that The mass ratio of the composite auxiliary agent to the red mud slurry is 2% to 3%.

5. The method according to claim 1, wherein The median particle size of the composite auxiliary agent is 5 μm to 30 μm.

6. The method according to claim 5, characterized in that The median particle size of the composite auxiliary agent is 10 μm to 15 μm.

7. The method according to claim 1, characterized in that The mass ratio of the dispersing aid to the reaction slurry is 0.1% to 1.0%.

8. The method according to claim 1, characterized in that The reaction temperature is 70° C. to 100° C., and the reaction time is 1 h to 6 h.

9. The method according to claim 8, characterized in that The reaction temperature is 90°C to 100°C.

10. The method according to claim 1, characterized in that The filter press separation includes a filter press feed section and a pressing pressure section; The pressure of the filter press feed section is 0.5 MPa to 1.5 MPa, and the pressure of the pressing pressure section is 1.0 MPa to 6.0 MPa.

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