Preparation method of bayer-process red mud-based cementitious material

Abstract

This application relates to a method for preparing a Bayer process red mud-based cementitious material, comprising the following steps: providing red mud generated during the Bayer process for alumina production; dewatering the red mud using a screening machine to obtain a filter cake with a predetermined particle size; drying the filter cake to reach a predetermined moisture content; and mixing the filter cake with an activating composite additive, a stabilizing additive, a curing agent, a reinforcing agent, and a retarder to obtain the Bayer process red mud-based cementitious material. This application directly presses red mud to form a filter cake, then processes the filter cake to a suitable moisture content and particle size, and then mixes it with other ingredients to form the Bayer process red mud-based cementitious material. Simultaneously, it fully utilizes elements such as Si, Al, Fe, and Na in the red mud; the entire process does not require complex treatment of the red mud, resulting in a simple process; the red mud is used as a whole as a raw material, generating no other waste; and the entire process requires no heating, resulting in low energy consumption.

Description

Technical Field

[0001] This application relates to the aluminum industry, and in particular to the treatment of red mud. Background Technology

[0002] Red mud, a waste product generated during the alumina refining process from bauxite, is named for its reddish-brown, slurry-like appearance. With the continuous development of the bauxite industry, my country's annual red mud discharge exceeds 15 million tons, and the total mass of red mud is trending upwards due to new production lines and upgrades to older equipment. Most alumina plants worldwide dump or stockpile red mud into the deep sea. This practice not only occupies vast amounts of land and farmland and incurs significant construction and maintenance costs, but also allows residual alkali in the red mud to seep into the ground, causing groundwater pollution. Furthermore, the dust generated from red mud stockpiles pollutes the environment, causing severe pollution. In today's society, where land resources are increasingly scarce and environmental protection is paramount, the comprehensive management of red mud has become a focal point of public concern.

[0003] Red mud can be classified into three types based on the alumina production method: sintering process, Bayer process, and combined process. Due to differences in bauxite content, the methods used for alumina production both domestically and internationally also differ. The Bayer process uses a strong alkali, NaOH, to dissolve high-alumina, high-iron bauxite, resulting in red mud with high alumina, iron oxide, and alkali content; it processes gibbsite and diaspore-type bauxite. The sintering and combined processes process insoluble high-silica, low-iron, diaspore-type, and kaolinite-type bauxite, producing red mud with high CaO content. The main components of Bayer process red mud are hematite, sodium aluminosilicate hydrate, and nepheline. Bayer process red mud is highly alkaline and has a high alkali content, making it suitable for alkali-activated cement. However, the application of Bayer process red mud in cement production is still under development. Summary of the Invention

[0004] This application provides a method for preparing Bayer process red mud-based cementitious materials to address the untapped technical problem of the application of Bayer process red mud in cement.

[0005] This application provides a method for preparing Bayer process red mud-based cementitious materials, the method comprising the following steps:

[0006] Red mud generated during the Bayer process for alumina production is provided, and the red mud is dehydrated using a screening machine to obtain filter cake with a predetermined particle size;

[0007] Dry the filter cake to reach a predetermined moisture content;

[0008] The filter cake is mixed with an activating composite agent, a stabilizing agent, a curing agent, a reinforcing agent, and a retarder to obtain the Bayer process red mud-based cementitious material.

[0009] In some embodiments of this application, the predetermined moisture content is 0-20%.

[0010] In some embodiments of this application, the predetermined particle size is: d50 < 100 μm.

[0011] In some embodiments of this application, the activating composite agent is at least one of sodium silicate, sodium phosphate, and sodium carbonate.

[0012] In some embodiments of this application, the stabilizing agent includes at least one of fly ash and slag powder.

[0013] In some embodiments of this application, the curing agent includes at least one of lime and carbide slag.

[0014] In some embodiments of this application, the reinforcing agent includes iron powder.

[0015] In some embodiments of this application, the retarder includes tartaric acid.

[0016] In some embodiments of this application, the second powder is mixed with the activating composite additive, stabilizing additive, curing agent, reinforcing agent, and retarder, and the mass ratio of the second powder to the activating composite additive, stabilizing additive, curing agent, reinforcing agent, and retarder is: 1:0.02-0.05:1.5-2.5:0.01-0.1:0.001-0.003:0.001-0.002.

[0017] In some embodiments of this application, the second powder is mixed with an activating composite agent, a stabilizing agent, a curing agent, a reinforcing agent, and a retarder, and the mixing is carried out by a mixer.

[0018] The technical solutions provided in this application have the following advantages compared with the prior art:

[0019] The method for preparing Bayer process red mud-based cementitious materials provided in this application involves directly pressing red mud to form a filter cake, then processing the filter cake to achieve a suitable moisture content and particle size, and finally mixing it with other ingredients to form the Bayer process red mud-based cementitious material. Simultaneously, it fully utilizes elements such as Si, Al, Fe, and Na in the red mud; the entire process requires no complex treatment of the red mud, resulting in a simple process; the red mud is used as a whole as a raw material, generating no other waste; and the entire process requires no heating, resulting in low energy consumption. Attached Figure Description

[0020] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0021] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a schematic flowchart illustrating a method for preparing Bayer process red mud-based cementitious materials, provided as an embodiment of this application. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0024] Unless otherwise specified, the terminology used herein should be understood as having the meaning commonly used in the art. Therefore, unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. In case of any conflict, this specification shall prevail.

[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] The application of Bayer red mud in cement is yet to be fully explored.

[0027] The technical solution provided in this application is to solve the above-mentioned technical problems, and the general idea is as follows:

[0028] This application provides a method for preparing Bayer process red mud-based cementitious materials, the method comprising the following steps:

[0029] S1: Provide red mud generated during the Bayer process for alumina production, and use a screening machine to dewater the red mud to obtain filter cake with a predetermined particle size;

[0030] S2: Dry the filter cake to reach a predetermined moisture content;

[0031] S3: The filter cake is mixed with an activating composite agent, a stabilizing agent, a curing agent, a reinforcing agent, and a retarder to obtain the Bayer process red mud-based cementitious material.

[0032] Those skilled in the art will understand that screening machines are commonly used mineral processing machinery that can perform screening while removing water.

[0033] The Bayer process red mud-based cementitious material obtained in this application belongs to alkali-activated cement.

[0034] This application involves directly pressing red mud to form a filter cake, then processing the filter cake to achieve suitable moisture content and particle size, before mixing it with other ingredients to form the Bayer process red mud-based cementitious material. Simultaneously, it fully utilizes elements such as Si, Al, Fe, and Na in the red mud, and the entire process requires no complex treatment of the red mud, resulting in a simple process; the red mud is used as a whole as a raw material, generating no other waste; and the entire process requires no heating, resulting in low energy consumption.

[0035] In some embodiments of this application, the predetermined moisture content is 0-20%.

[0036] Excessive water content in the filter cake will result in excessive water content in the Bayer process red mud-based cementitious material, making the cementitious material too fluid and unsuitable for use.

[0037] In some embodiments of this application, the predetermined particle size is: d50 < 100 μm.

[0038] The beneficial effect of having a predetermined particle size of d50<100um is to make the red mud more uniformly mixed with the activating composite additive, stabilizing additive, curing agent, reinforcing agent and retarder, and to make the alkaline substances in the Bayer process red mud-based cementitious materials more uniformly distributed.

[0039] In some embodiments of this application, the activating composite agent is at least one of sodium silicate, sodium phosphate, and sodium carbonate.

[0040] The function of activating composite additives is to stimulate the hydration reaction of the silica-alumina glass in slag powder or fly ash. Sodium silicate, sodium phosphate, and sodium carbonate are commonly used activating composite additives.

[0041] In some embodiments of this application, the stabilizing agent includes at least one of fly ash and slag powder.

[0042] In some embodiments of this application, the curing agent includes at least one of lime and carbide slag.

[0043] The role of the curing agent is to provide calcium ions to the silicon-aluminum tetrahedron, thereby curing the cementitious material.

[0044] In some embodiments of this application, the reinforcing agent includes iron powder.

[0045] The role of the reinforcing agent is to increase the mechanical strength of the cementitious material. Iron powder is chosen as the reinforcing agent because iron itself has high mechanical strength, and because when iron is added to the cementitious material and forms concrete, it will oxidize under the action of oxygen to form ionic bonds with the concrete matrix, resulting in a tight bond.

[0046] In some embodiments of this application, the retarder includes tartaric acid.

[0047] The advantage of using tartaric acid as a retarder is that it can regulate the pH of the cementitious material.

[0048] In some embodiments of this application, the second powder is mixed with the activating composite additive, stabilizing additive, curing agent, reinforcing agent, and retarder, and the mass ratio of the second powder to the activating composite additive, stabilizing additive, curing agent, reinforcing agent, and retarder is: 1:0.02-0.05:1.5-2.5:0.01-0.1:0.001-0.003:0.001-0.002.

[0049] In some embodiments of this application, the second powder is mixed with an activating composite agent, a stabilizing agent, a curing agent, a reinforcing agent, and a retarder, and the mixing is carried out using a mixer. Generally, the mixing time is 0.5-4 minutes, and the mixer speed is 50-300 r / min.

[0050] The present application is further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the application. Experimental methods in the following embodiments that do not specify specific conditions are generally determined according to national standards. If there is no corresponding national standard, then general international standards, conventional conditions, or conditions recommended by the manufacturer are followed.

[0051] Example 1

[0052] This embodiment provides a method for preparing Bayer process red mud-based cementitious materials, the method comprising the following steps:

[0053] 100g of red mud produced during the Bayer process for alumina production is provided. The red mud is dehydrated using a screening machine to obtain filter cake with a particle size of d50 = 80um.

[0054] The filter cake is dried to a moisture content of 18%.

[0055] The filter cake was mixed with an activating composite agent, a stabilizing agent, a curing agent, a reinforcing agent, and a retarder in a mass ratio of 1:0.05:2.5:0.01:0.001:0.002 to obtain 356.3g of the Bayer process red mud-based cementitious material.

[0056] After adding aggregate to the Bayer process red mud-based cementitious material, the water content is controlled at 110g. After stirring, the plastic paste binds together to form a hard stone-like substance, thus forming concrete.

[0057] The activation composite additive is composed of sodium silicate and sodium carbonate mixed in a 1:1 mass ratio.

[0058] The stabilizing agent is composed of fly ash and slag powder mixed in a 1:1 mass ratio.

[0059] The curing agent is composed of lime and carbide slag mixed in a 1:1 mass ratio.

[0060] The reinforcing agent is iron powder with a particle size of 10 μm.

[0061] The retarder is tartaric acid.

[0062] Example 2

[0063] This embodiment provides a method for preparing Bayer process red mud-based cementitious materials, the method comprising the following steps:

[0064] 100g of red mud produced during the Bayer process for alumina production is provided. The red mud is dehydrated using a screening machine to obtain filter cake with a particle size of d50 = 40um.

[0065] The filter cake is dried to a moisture content of 13%.

[0066] The filter cake is mixed with an activating composite agent, a stabilizing agent, a curing agent, a reinforcing agent, and a retarder in a mass ratio of 1:0.02:1.5:0.1:0.003:0.001 to obtain the Bayer process red mud-based cementitious material.

[0067] After adding aggregate to the Bayer process red mud-based cementitious material, the water content is controlled at 79g. After stirring, the plastic paste binds together to form a hard, stone-like substance, thus forming concrete. The activating composite additive is composed of sodium silicate and sodium carbonate mixed in a 2:1 mass ratio.

[0068] The stabilizing agent is composed of fly ash and slag powder mixed in a mass ratio of 1:3.

[0069] The curing agent is composed of lime and carbide slag mixed in a mass ratio of 2:1.

[0070] The reinforcing agent is iron powder with a particle size of 50 μm.

[0071] The retarder is tartaric acid.

[0072] Example 3

[0073] This embodiment provides a method for preparing Bayer process red mud-based cementitious materials, the method comprising the following steps:

[0074] 100g of red mud produced during the Bayer process for alumina production is provided. The red mud is dehydrated using a screening machine to obtain filter cake with a particle size of d50 = 60um.

[0075] The filter cake is dried to a moisture content of 9%.

[0076] The filter cake is mixed with an activating composite agent, a stabilizing agent, a curing agent, a reinforcing agent, and a retarder in a mass ratio of 1:0.04:2.0:0.05:0.002:0.0015 to obtain the Bayer process red mud-based cementitious material.

[0077] After adding aggregate to the Bayer process red mud-based cementitious material, the water content is controlled at 94g. After stirring, the plastic paste binds together to form a hard stone-like substance, thus forming concrete.

[0078] The activation composite additive is composed of sodium silicate and sodium carbonate mixed in a mass ratio of 1:3.

[0079] The stabilizing agent is composed of fly ash and slag powder mixed in a mass ratio of 2:1.

[0080] The curing agent is composed of lime and carbide slag mixed in a mass ratio of 1:2.

[0081] The reinforcing agent is iron powder with a particle size of 25 μm.

[0082] The retarder is tartaric acid.

[0083] Relevant experimental and effect data:

[0084] The concrete obtained in Examples 1-3 was subjected to performance tests according to the standard GB / T 2542-2012. The test results are shown in the table below:

[0085]

[0086] Various embodiments of this application may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a hard limitation on the scope of this application; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values ​​within that range. For example, it should be considered that the range description from 1 to 6 has 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., and single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Furthermore, whenever a numerical range is referred to herein, it means including any referenced number (fraction or integer) within the referred range.

[0087] In this application, unless otherwise stated, directional terms such as "upper" and "lower" specifically refer to the drawing directions in the accompanying drawings. Furthermore, in the description of this application, the terms "comprising," "including," etc., mean "including but not limited to." Moreover, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element. In this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. In this document, "and / or" describes the relationship between related objects, indicating that three relationships can exist; for example, A and / or B can represent: A alone, A and B simultaneously, or B alone. For associations involving three or more related objects described using "and / or", it indicates that any one of the three related objects can exist alone, or at least two of them can exist simultaneously. For example, for A, and / or B, and / or C, it can mean that any one of A, B, and C exists alone, or any two of them exist simultaneously, or all three of them exist simultaneously. In this document, "at least one" means one or more, and "more than one" means 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 multiple 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, and c can each be single or multiple.

[0088] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this 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 this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A method for preparing Bayer process red mud-based cementitious materials, characterized in that, The preparation method of the Bayer process red mud-based cementitious material includes the following steps: Red mud generated during the Bayer process for alumina production is provided, and the red mud is dehydrated using a screening machine to obtain filter cake with a predetermined particle size; Dry the filter cake to reach a predetermined moisture content; The filter cake is mixed with an activating composite additive, a stabilizing additive, a curing agent, a reinforcing agent, and a retarder in a mass ratio of 1:0.02-0.05:1.5-2.5:0.01-0.1:0.001-0.003:0.001-0.002 using a mixer to obtain the Bayer process red mud-based cementitious material. The predetermined particle size is 40 μm ≤ d50 < 100 μm. The curing agent includes at least one of lime and carbide slag. The activating composite additive is at least one of sodium silicate, sodium phosphate, and sodium carbonate. The reinforcing agent includes iron powder. The retarder includes tartaric acid. The stabilizing agent includes at least one of fly ash and slag powder; The predetermined moisture content is 0-20%; The mixing time is 0.5-4 min, and the mixing speed of the mixer is 50-300 r / min.

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