Red mud alkali-free accelerator and preparation method thereof

Abstract

The present application relates to the technical field of alkali-free accelerator, and particularly discloses a kind of red mud alkali-free accelerator and a preparation method thereof.The preparation method comprises the following steps:S1, red mud powder pretreatment: using suspension shock conical surface concentrator to treat red mud powder;S2, raw material addition: after the pretreatment, the red mud powder is modified by refining, and is put into a reaction kettle according to the preset mass fraction ratio;S3, main reaction: industrial sulfuric acid and phosphorus chemical by-products are sequentially added into the reaction kettle, the specific temperature in the kettle is controlled, and the reaction is completed by continuous stirring;S4, post-treatment: after the reaction is completed, the reaction system is sequentially subjected to suspension treatment, complexation treatment and inorganic acid adjustment treatment;S5, product obtaining: after the above post-treatment, the alkali-free accelerator product is obtained.The present application effectively solves the environmental pollution problem caused by the large amount of red mud accumulation, and prepares an alkali-free accelerator with excellent performance, realizes the efficient utilization of red mud as a bulk resource, and has both environmental protection value and application value.

Description

Technical Field

[0001] This invention relates to the field of alkali-free quick-setting agents, and in particular to an alkali-free quick-setting agent for red mud and its preparation method. Background Technology

[0002] Red mud is a highly alkaline solid waste discharged from the alumina industry, with a pH value of 10-13. It is rich in active components such as Fe2O3 and Al2O3, but due to the influence of mineral lattice encapsulation, the active ions are difficult to dissolve, making resource utilization difficult. As of 2023, China's red mud stockpiles exceeded 1.6 billion tons, with an annual increase of 120 million tons, and a comprehensive utilization rate of less than 10%. The large-scale open-air stockpiling of red mud not only occupies land, but its highly alkaline leachate also leads to soil alkalization and groundwater pollution. The environmental risks of red mud ponds in alumina-concentrated areas such as Wenshan, Yunnan Province, are particularly prominent, hindering the green development of the regional aluminum industry.

[0003] In recent years, breakthroughs have been made in red mud pretreatment technology. By employing a suspended cone concentrator and a combined magnetic-gravity separation process, the iron concentrate grade of red mud has been increased to 52% (Fe content), while the red mud particle size has been refined to D. 90 =10-15μm, which increases the specific surface area of ​​minerals and provides a high-quality raw material basis for the activation, modification and functional utilization of red mud.

[0004] Accelerators are core admixtures in shotcrete, widely used in tunnels, mines, and other engineering projects. However, current mainstream products have significant technical defects: alkaline accelerators have an alkali content >5% (Na₂O eq.), easily triggering alkali-aggregate reaction, resulting in a concrete strength loss >30% in the later stages; alkali-free accelerators rely excessively on aluminum sol, with raw material costs >8000 RMB / ton, making them too expensive for large-scale promotion; and solid waste-based accelerators use coarse red mud particles (D...). 90 >50μm), active ion dissolution rate <40%, requires high-temperature calcination activation above 1000℃, high energy consumption, and unstable product performance with narrow application range.

[0005] In summary, existing quick-setting agents cannot simultaneously meet the core requirements of low alkali and environmental protection, low cost, high activity, and low energy consumption. Relying on the refined red mud raw materials from Yunnan, it is necessary to overcome the bottlenecks of low red mud activity and poor dissolution, and develop an alkali-free quick-setting agent that uses red mud as the main raw material, does not require high-temperature calcination, is low in cost, and has stable performance. This will enable the coordinated development of the large-scale resource utilization of red mud and the green upgrading of the quick-setting agent industry, which has become a key technical problem that urgently needs to be solved. Summary of the Invention

[0006] This invention discloses an alkali-free quick-setting agent for red mud and its preparation method, which solves the environmental problems caused by the large-scale accumulation of red mud, and at the same time prepares a high-performance alkali-free quick-setting agent, realizing the large-scale resource utilization of red mud.

[0007] The technical implementation scheme of the present invention is as follows:

[0008] An alkali-free quick-setting agent for red mud, comprising the following components:

[0009] Modified red mud powder: 30-40 parts; industrial sulfuric acid: 25-35 parts; phosphorus chemical byproducts: 10-25 parts; inorganic acid regulator: 5-10 parts; complexing agent: 5-10 parts; suspending thickener: 1-2 parts; wherein, the inorganic acid regulator is a composition of boric acid and citric acid in a mass ratio of 1:1; the phosphorus chemical byproducts are either fluorosilicic acid or phosphogypsum acid hydrolysis solution; the pH value of the quick-setting agent is controlled at 2.5-3.0; the complexing agent is a composition of triethanolamine, diethanolamine and EDTA in a molar ratio of 5:3:2.

[0010] A method for preparing an alkali-free quick-setting agent for red mud includes the following steps:

[0011] S1. Red mud powder pretreatment: Red mud powder is treated using a suspended cone concentrator.

[0012] S2. Raw material addition: Take the pretreated and refined red mud powder and add it to the reactor according to the preset mass ratio;

[0013] S3. Main reaction: Industrial sulfuric acid and phosphorus chemical byproducts are added sequentially to the reactor. The temperature inside the reactor is controlled at a certain level, and the mixture is continuously stirred to carry out the reaction.

[0014] S4. Post-treatment: After the reaction is completed, the reaction system is subjected to suspension treatment, complexation treatment and inorganic acid conditioning treatment in sequence.

[0015] S5. Finished product obtained: After step S4, the alkali-free quick-setting agent is obtained.

[0016] As a further description of the above technical solution, in the S1 pretreatment step, firstly, the raw red mud is placed in a drying device and continuously baked at a temperature of 105°C until the moisture content of the red mud is reduced to 2% or below; secondly, the dried red mud is immediately fed into a suspension cone concentrator for processing. Through the suspension and beneficiation action of the equipment, the red mud is deeply refined and modified, resulting in red mud powder with a specific surface area ≥800m² / kg and a particle size D... 90 ≤10μm.

[0017] As a further description of the above technical solution, in step S3, the reaction temperature is 70℃ - 100℃, the stirring rate is 200-300 r / min, and the stirring time is 90 - 210 min.

[0018] As a further description of the above technical solution, in step S3, the inorganic acid conditioning agent used in the inorganic acid conditioning treatment is a combination of boric acid and citric acid in a mass ratio of 1:1. The amount of inorganic acid conditioning agent added is 5-10 parts by mass of red mud powder, and the pH value of the reaction system after adjustment is 2.5-3.0.

[0019] As a further description of the above technical solution, in step S4, the suspension thickener used in the suspension treatment is xanthan gum, and the amount of xanthan gum added is 1-2 parts by weight of red mud powder. Under the condition of 2000 r / min, the homogenization treatment time is 20-40 min.

[0020] As a further description of the above technical solution, in step S5, the obtained alkali-free quick-setting agent product is tested, and the pH value is 2.5-3.0 and the density is 1.25±0.05 mm.

[0021] The present invention has the following advantages:

[0022] This invention can effectively utilize industrial red mud generated by local enterprises in Yunnan, thereby reducing the land occupation and environmental safety hazards associated with red mud storage and providing significant environmental benefits. At the same time, it can also process red mud waste into high-value-added alkali-free quick-setting agents, achieving efficient utilization of solid waste and significantly reducing the production cost of quick-setting agents, resulting in outstanding economic benefits. The resulting alkali-free quick-setting agent has excellent quick-setting effect and maintains stable strength in the later stages, meeting the requirements of various engineering scenarios for the quick-setting performance of concrete. Attached Figure Description

[0023] Figure 1 This is a process flow diagram of the present invention.

[0024] Figure 2 This is a process flow diagram of the red mud pretreatment of the present invention.

[0025] Figure 3 This is an electron microscope image showing the microstructure of the accelerator of this invention.

[0026] Figure 4 This is a comparative diagram of the phase composition of the red mud before acid hydrolysis according to the present invention.

[0027] Figure 5 This is a comparative diagram of the phase composition of the red mud after acid hydrolysis according to the present invention. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings. It is hereby declared that the directional terms such as up, down, left, right, front, back, inside, and outside used in this text are based solely on the accompanying drawings and are not intended to specifically limit the invention.

[0029] Example 1:

[0030] An alkali-free quick-setting agent for red mud, comprising the following components:

[0031] Modified red mud powder: 35 parts; industrial sulfuric acid: 30 parts; phosphorus chemical byproducts: 20 parts; phosphogypsum acid hydrolysis solution: 20 parts; complexing agent: (triethanolamine: diethanolamine: EDTA = 5:3:2) 8 parts; inorganic acid (boric acid: citric acid = 1:1) 7 parts.

[0032] The preparation process includes the following steps:

[0033] The first step involves pre-treating the red mud powder using a drying device and a suspended cone concentrator to process it into red mud powder with a specific surface area ≥800m² / kg and a particle size D. 90 ≤10μm, and collected for later use; wherein, the drying temperature is 105℃.

[0034] The second step involves adding the raw material (red mud powder) into the reactor, followed by the sequential addition of industrial sulfuric acid, phosphorus chemical byproducts, etc. The reaction temperature is 70℃, the stirring rate is 200r / min, and the stirring time is 120min.

[0035] The third step is to add a complexing agent when the temperature of the reactor drops to 40°C, then add an inorganic acid to adjust the pH to 2.8, and finally add 1.5 parts of xanthan gum to obtain the finished product.

[0036] It should be noted that the α-Fe₂O₃ / Al(OH)₃ dissolution rate in red mud is >85% under fluorosilicic acid catalysis, forming a [Al-Fe-Si-F] complex fast-condensing phase. Furthermore, the modified red mud powder is processed to D... 90 After reaching ≤10μm (specific surface area ≥800m² / kg), the ion dissolution efficiency is increased by 3 times compared with traditional ball milling. During the in-situ alkalinity neutralization process, sulfuric acid and phosphorus chemical by-products synergistically reduce the pH of red mud to neutral, so that the alkalinity content of the product is ≤0.5% (Na2O eq.).

[0037] Example 2:

[0038] An alkali-free quick-setting agent for red mud, comprising the following components:

[0039] Modified red mud powder: 40 parts; industrial sulfuric acid: 25 parts; phosphorus chemical byproducts: 20 parts; fluorosilicic acid: 15 parts; complexing agent: (triethanolamine: diethanolamine: EDTA = 5:3:2) 8 parts; inorganic acid (boric acid: citric acid = 1:1) 7 parts.

[0040] The preparation process includes the following steps:

[0041] The first step involves pre-treating the red mud powder using a drying device and a suspended cone concentrator to process it into red mud powder with a specific surface area ≥800m² / kg and a particle size D. 90 ≤10μm, and collected for later use; wherein, the drying temperature is 105℃.

[0042] The second step involves adding the raw material (red mud powder) into the reactor, followed by the sequential addition of industrial sulfuric acid, phosphorus chemical byproducts, etc. The reaction temperature is 70℃, the stirring rate is 200r / min, and the stirring time is 120min.

[0043] The third step is to add a complexing agent when the temperature of the reactor drops to 40°C, then add an inorganic acid to adjust the pH to 2.8, and finally add 1.5 parts of xanthan gum to obtain the finished product.

[0044] Example 3:

[0045] An alkali-free quick-setting agent for red mud, comprising the following components:

[0046] Modified red mud powder: 30 parts; industrial sulfuric acid: 25 parts; phosphorus chemical byproducts: 20 parts; phosphogypsum acid hydrolysis solution: 10 parts; fluorosilicic acid: 10 parts; complexing agent: (triethanolamine: diethanolamine: EDTA = 5:3:2) 8 parts; inorganic acid (boric acid: citric acid = 1:1) 7 parts.

[0047] The preparation process includes the following steps:

[0048] The first step involves pre-treating the red mud powder using a drying device and a suspended cone concentrator to process it into red mud powder with a specific surface area ≥800m² / kg and a particle size D. 90 ≤10μm, and collected for later use; wherein, the drying temperature is 105℃.

[0049] The second step involves adding the raw material (red mud powder) into the reactor, followed by the sequential addition of industrial sulfuric acid, phosphorus chemical byproducts, etc. The reaction temperature is 70℃, the stirring rate is 200r / min, and the stirring time is 120min.

[0050] The third step is to add a complexing agent when the temperature of the reactor drops to 40°C, then add an inorganic acid to adjust the pH to 2.8, and finally add 1.5 parts of xanthan gum to obtain the finished product.

[0051] The performance of the three embodiments was tested and compared, as shown in the table below:

[0052] index Example 1 Example 2 Example 3 National Standard Requirements Alkali-free market Initial condensation (s) 118 130 125 ≤300 142 Final condensation (s) 228 240 235 ≤600 260 Daily intensity 13.2 12.0 12.5 ≥7.0 11.2 28-day intensity (%) 110 105 108 ≥90% 100 Alkali content 0.258 0.352 0.32 ≤300 0.45 Settlement rate (30 days) 2.8% 3.5% 3.0% ≤5% 4.8%

[0053] After comparing the three examples, Example 1 had the lowest strength, alkali content, and precipitation rate, so Example 1 is the optimal formulation.

[0054] Appendix Figure 3 In the middle section: SEM images show that the product is a uniform nano-network structure, providing sufficient active sites for the rapid solidification reaction; EDS energy dispersive spectroscopy confirms the presence of an [Al-Fe-Si-F] associated phase (binding energy A12p=74.5eV) in the product, which is the core active component for achieving excellent rapid solidification effect; Selected area electron diffraction (SAED) shows amorphous-microcrystalline composite characteristics, which not only ensures the speed of the rapid solidification reaction, but also provides a structural basis for the continuous increase in intensity in the later stage.

[0055] As attached Figure 4 and Figure 5 The results show that the main phases of the red mud before acid hydrolysis were calcium aluminum feldspar (42%), hydrated garnet (28%), SiO2 (18%), and others (12%). After acid hydrolysis and activation, the phases were reconstructed into ettringite-like active phases (65%), CaO·2Al2O3 (25%), and free acid (10%). The inert components in the red mud were fully activated and transformed into highly active aluminum-based and calcium-based components required by the quick-setting agent. This verifies the effectiveness of red mud resource utilization from the perspective of phase composition. At the same time, the experiment shows that the Fe2O3 content after acid hydrolysis is 29.2% lower than that of the original red mud, which further optimizes the quick-setting and strength properties of the product.

[0056] In summary:

[0057] Environmental benefits verification: This invention can realize the large-scale consumption of red mud from the local aluminum industry in Yunnan. A single batch of preparation can consume 40% to 45% of the red mud raw materials, which greatly reduces the land occupation of red mud storage and the risk of heavy metal leakage, resulting in significant environmental benefits.

[0058] Economic benefit verification: Replacing traditional industrial raw materials with red mud reduces production costs by more than 20% compared to commercially available alkali-free quick-setting agents, realizing the high-value utilization of solid waste.

[0059] Characteristics of red mud raw materials:

[0060] Element <![CDATA[Fe2O3]]> <![CDATA[Al2O3]]> <![CDATA[SiO2]]> <![CDATA[Na2O]]> Radioactivity (IRa) content 28.5% 19.2% 15.7% 5.3% 0.8

[0061] Environmental testing: Heavy metal leaching (Pb / Cr) 6 (⁺) The value is lower than the limit of GB5085.3, which meets the safety requirements for building materials.

[0062] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A red mud alkali-free quick-setting agent, characterized in that, This alkali-free quick-setting agent for red mud comprises the following components: Modified red mud powder: 30-40 parts; industrial sulfuric acid: 25-35 parts; phosphorus chemical byproducts: 10-25 parts; inorganic acid regulator: 5-10 parts; complexing agent: 5-10 parts; suspending thickener: 1-2 parts; The inorganic acid regulator is a composition of boric acid and citric acid in a mass ratio of 1:

1. The phosphorus chemical byproduct is either fluorosilicic acid or phosphogypsum acid hydrolysate, and the pH value of the quick-setting agent is controlled at 2.5-3.

0. The complexing agent is a composition of triethanolamine, diethanolamine and EDTA in a molar ratio of 5:3:

2.

2. A method for preparing an alkali-free quick-setting agent as described in claim 1, characterized in that, Includes the following steps: S1. Red mud powder pretreatment: Red mud powder is treated using a suspended cone concentrator. S2. Raw material addition: Take the pretreated and refined red mud powder and add it to the reactor according to the preset mass ratio; S3. Main reaction: Industrial sulfuric acid and phosphoric acid chemical byproducts are added to the reactor in sequence. The temperature inside the reactor is controlled at a certain level and the mixture is continuously stirred to carry out the reaction. S4. Post-treatment: After the reaction is completed, the reaction system is subjected to suspension treatment, complexation treatment and inorganic acid conditioning treatment in sequence. S5. Finished product obtained: After step S4, the alkali-free quick-setting agent is obtained.

3. The method for preparing an alkali-free quick-setting agent for red mud according to claim 2, characterized in that, In the S1 pretreatment step, the raw red mud material is first placed in a drying device and continuously baked at a temperature of 105°C until the moisture content of the red mud is reduced to 2% or less. Secondly, the dried red mud is immediately fed into a vibrating cone concentrator for processing. Through the vibration and beneficiation action of the equipment, the red mud is deeply refined and modified, resulting in red mud powder with a specific surface area ≥800m² / kg and a particle size D. 90 ≤10μm.

4. The method for preparing an alkali-free quick-setting agent for red mud according to claim 3, characterized in that, In step S3, the reaction temperature is 70℃ - 100℃, the stirring rate is 200-300 r / min, and the stirring time is 90 - 210 min.

5. A method for preparing an alkali-free quick-setting agent for red mud according to claim 4, characterized in that, In step S3, the inorganic acid conditioning treatment uses a combination of boric acid and citric acid in a mass ratio of 1:

1. The amount of inorganic acid conditioning agent added is 5-10 parts by mass of red mud powder, and the pH value of the reaction system after adjustment is 2.5-3.

0.

6. The method for preparing an alkali-free quick-setting agent for red mud according to claim 5, characterized in that, In step S4, the suspension thickener used in the suspension treatment is xanthan gum, and the amount of xanthan gum added is 1-2 parts by weight of red mud powder. The homogenization treatment time is 20-40 min at 2000 r / min.

7. The method for preparing an alkali-free quick-setting agent for red mud according to claim 1, characterized in that, In step S5, the obtained alkali-free quick-setting agent product is tested, and the pH value is 2.5-3.0 and the density is 1.25±0.05 mm.

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