Method for comprehensively utilizing bauxite tailings

Abstract

The invention discloses a method for comprehensively utilizing bauxite tailings, which comprises the following steps: mixing bauxite tailings, standard sand, cement and water, and carrying out compression molding and natural curing to obtain a baking-free brick. And reasonable and large-scale utilization of tailing resources is realized. The compressive strength of the baking-free brick prepared by the invention meets the requirements of Non-Sintered Rubbish Tailing Brick (JC / T422-2007) MU15 grade, a proper thought is provided for effective utilization of bauxite tailings, energy loss and greenhouse effect are reduced, and good social benefits, economic benefits and environmental benefits can be generated.

Description

Technical Field

[0001] This invention belongs to the field of chemical technology, specifically relating to a method for the comprehensive utilization of bauxite tailings. Background Technology

[0002] Most bauxite ore in my country is of low grade, and the mining and beneficiation processes generate a large amount of tailings. These tailings have small particle sizes and large quantities. If they are directly stored in tailings ponds, in addition to posing safety hazards, it will also result in a waste of mineral resources. Therefore, researching technically and economically feasible technologies for the comprehensive utilization of tailings is an urgent problem to be solved.

[0003] Non-fired bricks possess advantages such as high material strength, good durability, standard dimensions, complete shape, precise dimensions, and convenient construction. They align with the national strategy of energy conservation and environmental protection for sustainable development, making them a mainstream product in contemporary building materials with broad market prospects. With the rapid development of urban construction, the demand for large quantities of building materials has led to the extensive mining of river sand, impacting the river's ecological environment. Tailings, containing a large amount of quartz, can replace river sand in building materials. Furthermore, how to utilize bauxite tailings to produce non-fired bricks that meet national quality requirements remains a challenging research area. Summary of the Invention

[0004] This invention aims to at least partially solve one of the technical problems in related technologies. This invention proposes a method for the comprehensive utilization of bauxite tailings, characterized in that the method includes: (1) The bauxite tailings, standard sand and cement are mixed for the first time to obtain the first material; (2) The first material and water are stirred a second time to obtain the second material; (3) The second material is subjected to pressure molding in a mold to obtain a specimen; (4) The specimens are naturally cured to obtain non-fired bricks.

[0005] In some embodiments, in step (1), the bauxite tailings comprise 35-45 wt% alumina and 25-35 wt% silica.

[0006] In some embodiments, in step (1), the content of particles with a particle size of less than 0.038 mm in the bauxite tailings is more than 80 wt%.

[0007] In some embodiments, in step (1), the particle size of the standard sand is 0.08~4.75 mm.

[0008] In some embodiments, in step (1), the cement comprises silicate cement.

[0009] In some embodiments, in step (1), the first stirring speed is 130~140 rpm and the time is 2~3 min.

[0010] In some embodiments, in step (1), based on 3 kg of the bauxite tailings, the amount of standard sand added is 0.5~1.5 kg, the amount of cement added is 0.5~1.5 kg, and the amount of water added is 5~15 kg.

[0011] In some embodiments, in step (2), the second stirring speed is 130~140 rpm and the time is 2~3 min.

[0012] In some embodiments, in step (3), the pressure of the compression molding is 10~25MPa and the time is 20~30min.

[0013] In some embodiments, in step (4), the temperature of the natural curing conditions is 15~25°C and the relative humidity is not less than 80%.

[0014] In some embodiments, the unconfined compressive strength of the unfired brick is greater than 15 MPa.

[0015] The present invention has the following beneficial effects: This invention recycles bauxite tailings to produce non-fired bricks of varying strengths, achieving the rational and large-scale utilization of tailings resources. The compressive strength of the non-fired bricks prepared by this invention meets the MU15 grade requirements of "Non-sintered Waste Tailings Bricks" (JC / T422-2007), providing a suitable approach for the effective utilization of bauxite tailings, reducing energy consumption and the greenhouse effect, and generating significant social, economic, and environmental benefits.

[0016] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Detailed Implementation

[0017] The present invention will now be described with reference to specific embodiments. It should be noted that these embodiments are merely descriptive and do not limit the invention in any way. Unless otherwise specified, the raw materials used in the following embodiments and comparative examples are all commercially available products directly in the art or prepared according to conventional methods existing in the art. Unless otherwise specified, the mixing or reaction temperature is room temperature.

[0018] In the following examples, the particle size distribution and unconfined compressive strength were measured by using a universal testing machine (CMT-5305) under experimental conditions of axial pressure only, and by conducting an unconfined compression test on the specimen (refer to ISO 17892-7:2018 Geotechnical Laboratory Tests - Unconfined Compression Tests).

[0019] The bauxite tailings used in this embodiment of the invention are tailings products obtained after beneficiation and desilication of raw bauxite ore. The main mineral component of these bauxite tailings is kaolinite, followed by gibbsite, chlorite, anatase, illite, quartz, etc. Samples were taken after drying and tested for analysis. The elemental contents are shown in Table 1.

[0020] Table 1 Chemical composition of bauxite tailings

[0021] Note: *Unit is 10 -6 .

[0022] Particle size analysis of bauxite tailings in raw materials was performed using the sieving method (CT0115-93). The dried material was weighed and placed on the top layer of a standard sieve. The weight of each particle size was obtained by physical vibration. The particle size percentage of the material was then calculated. The particle size analysis results of bauxite tailings are shown in Table 2.

[0023] Table 2. Particle size analysis results of bauxite tailings

[0024] The standard sand was Pingtan standard sand, with a particle size range of 0.08~4.75mm, purchased from China Standard Sand Plant. It was graded as follows: 30wt% for particles with a particle size range of 2.0~4.75mm, 50wt% for particles with a particle size range of 0.5~2.0mm, and 20wt% for particles with a particle size range of 0.08~0.5mm.

[0025] The cement is ordinary Portland cement grade 42.5, with a particle size of 0.005~0.1mm, and was purchased from Hubei Zhongxia Cement (Group) Co., Ltd.

[0026] Example A1 (1) Mix 50kg of bauxite tailings, 30kg of standard sand, and 20kg of cement at 137 rpm for 3 minutes to obtain the first material; (2) Stir the first material and 12.36 kg of water at 137 rpm for 3 min to obtain the second material; (3) Add the second material into a mold of φ50mm x 130mm, hold it under the pressure of 10MPa jack for 2min, and form a specimen of φ50mm x 50mm; (4) The specimens were cured at 25℃ and 85% relative humidity for 7 days to obtain non-fired bricks.

[0027] Example A2 Change the pressure applied by the jack to 15 MPa, and keep other conditions the same as in Example A1.

[0028] Example A3 Change the pressure applied by the jack to 20 MPa, and keep other conditions the same as in Example A1.

[0029] Example A4 Change the pressure applied by the jack to 25 MPa, and keep other conditions the same as in Example A1.

[0030] The unconfined compressive strength of the unfired bricks in Examples A1-A4 is shown in Table 1.

[0031] Table 1

[0032] According to the test results in Table 1, when the molding pressure is not less than 20 MPa, the unconfined compressive strength of the unfired bricks reaches the MU15 level (greater than 15.0 MPa). However, excessive pressure will lead to high energy consumption and wear on the equipment. Therefore, the molding pressure is preferably 20~25 MPa, and more preferably 20 MPa.

[0033] Example B1 The amount of water added in step (2) was changed to 9.89 kg, and the rest was the same as in Example A3.

[0034] Example B2 The amount of water added in step (2) was changed to 11.11 kg, and the rest was the same as in Example A3.

[0035] Example B3 The amount of water added in step (2) was changed to 13.64 kg, and the rest was the same as in Example A3.

[0036] The unconfined compressive strength of the unfired bricks in Examples A3 and B1-B3 is shown in Table 2.

[0037] Table 2

[0038] As shown in Table 2, the strength decreases when the water content is too high or too low. Insufficient water makes it difficult for the specimens to bond together, resulting in loose, unbonded specimens prone to deformation. This may be because too little water hinders the cement's hydration and hardening, leading to insufficient bonding with tailings and increased likelihood of cracks and delamination after molding. Conversely, excessive water occupies space, increasing molding resistance during pressure molding and ultimately affecting the final specimen shape. After evaporation, voids remain, reducing specimen strength. Furthermore, excessive water can cause slurry overflow during molding, adhering to the mold and making demolding difficult.

[0039] Example C1 The amount of cement added in step (1) is changed to 10 kg, the amount of bauxite tailings added is 60 kg, and the rest is the same as in Example A3.

[0040] Example C2 The amount of cement added in step (1) is changed to 15 kg, the amount of bauxite tailings added is 55 kg, and the rest is the same as in Example A3.

[0041] Example C3 The amount of cement added in step (1) is changed to 25 kg, and the amount of bauxite tailings added is 45 kg. The rest is the same as in Example A3.

[0042] The unconfined compressive strength of the unfired bricks in Examples A3, C1-C3 is shown in Table 3.

[0043] Table 3

[0044] According to the test results in Table 3, the unconfined compressive strength of the unfired bricks increases with the increase of cement content. This may be because the cement reacts with the carbonate and silicate minerals in the tailings during the hydration process and binds them tightly together, thereby improving the strength of the specimen.

[0045] Example D1 The amount of standard sand added in step (1) is changed to 5 kg, and the amount of bauxite tailings added is 75 kg. The rest is the same as in Example A3.

[0046] Example D2 The amount of standard sand added in step (1) is changed to 10 kg, and the amount of bauxite tailings added is 70 kg. The rest is the same as in Example A3.

[0047] Example D3 The amount of standard sand added in step (1) is changed to 15 kg, the amount of bauxite tailings added is 65 kg, and the rest is the same as in Example A3.

[0048] The unconfined compressive strength of the unfired bricks in Examples A3 and D1-D3 is shown in Table 4.

[0049] Table 4

[0050] According to the test results in Table 4, the added standard sand can increase the content of coarse particles in the material, thus acting as a support structure during the production of dry-pressed, non-fired bricks. However, excessive use of standard sand will reduce the amount of tailings incorporated, thereby failing to achieve the goal of utilizing tailings in large quantities.

[0051] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications may still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions may be made to some of the technical features. Such modifications or substitutions 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 the comprehensive utilization of bauxite tailings, characterized in that, The method includes: (1) The bauxite tailings, standard sand and cement are mixed for the first time to obtain the first material; (2) The first material and water are stirred a second time to obtain the second material; (3) The second material is pressed and molded in a mold to obtain a specimen; (4) The specimens are naturally cured to obtain non-fired bricks.

2. The method according to claim 1, characterized in that, In step (1), the bauxite tailings comprise 35-45 wt% alumina and 25-35 wt% silica; and / or, The bauxite tailings have a particle size of less than 0.038 mm, reaching more than 80 wt%.

3. The method according to claim 1, characterized in that, In step (1), the particle size of the standard sand is 0.08~4.75mm.

4. The method according to claim 1, characterized in that, In step (1), the cement includes silicate cement.

5. The method according to any one of claims 1 to 4, characterized in that, In step (1), the first stirring speed is 130~140 rpm and the time is 2~3 min.

6. The method according to claim 1, characterized in that, Based on 3 kg of the bauxite tailings, the amount of standard sand added is 0.5~1.5 kg, the amount of cement added is 0.5~1.5 kg, and the amount of water added is 5~15 kg.

7. The method according to claim 1, characterized in that, In step (2), the second stirring speed is 130~140 rpm and the time is 2~3 min.

8. The method according to claim 1, characterized in that, In step (3), the pressure of the compression molding is 10~25MPa and the time is 20-30min.

9. The method according to claim 1, characterized in that, In step (4), the temperature of the natural curing conditions is 15~25℃ and the relative humidity is not less than 80%.

10. The method according to claim 1, characterized in that, The unconfined compressive strength of the unfired brick is greater than 15 MPa.

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