Device and method for driving red mud to be dealkalized and reconstituted into soil through temperature self-maintaining oxidation

Abstract

The invention discloses a device and a method for driving red mud to dealkalize and reconstruct soil through temperature self-maintaining oxidation. The device comprises a vertical reaction device, a stirrer, an aeration head and a monitoring device. The method comprises the steps of slurry preparation, reaction and soluble salt recovery. Red mud dealkalization is achieved through sulfur / carbon oxidation acid production, reaction temperature self-maintenance is achieved through reaction heat release, and the external energy supply requirement is lowered; the oxygen is beneficial to forming an expanded bed and enhancing the mixing and mass transfer efficiency of the slurry; the oxidation reaction can convert part of harmful components in the red mud and improve the physicochemical properties of the red mud, for example, the alkalinity is reduced, the agglomeration is improved, the organic matter content is increased and the like, so that the treated product can be suitable for ecological soil, and the ecological treatment of the red mud is realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of solid waste treatment, and in particular relates to a device and method for temperature-self-maintained oxidation-driven red mud dealkalization and soil reconstitution. Background Art

[0002] Red mud, a major industrial solid waste emitted during alumina production, is highly alkaline (pH = 10-13), contains high salt content, and contains fine particles. Large-scale storage of red mud not only consumes land resources but also poses a serious threat to the surrounding soil, water bodies, and atmospheric environment. Direct contact with highly alkaline red mud or leaching with rainwater can cause severe salinization and compaction of surrounding soil, destroying soil structure and fertility, significantly inhibiting plant growth, and even causing widespread vegetation death. The surface of dried red mud reservoirs is highly susceptible to dust. The fine alkaline dust is spread by wind, causing atmospheric pollution and affecting air quality. It can also corrode infrastructure and pose a compounding threat to the surrounding ecological environment.

[0003] Existing red mud dealkalization methods, such as acid neutralization, water washing, CO2 mineralization, etc., have limitations in practical applications. Although the acid neutralization method can effectively reduce the pH value, it is usually accompanied by problems such as high acid consumption and high operating costs. It is also easy to introduce secondary pollution, such as producing a large amount of difficult-to-treat acidic wastewater, and may cause the dissolution and loss of valuable metals or harmful heavy metals in the red mud. Although the water washing method is relatively simple to operate, its water consumption is huge, resulting in a large amount of highly alkaline wastewater that needs further treatment, and the treatment cycle is long. The effect of removing bound alkali in red mud is limited, and it is difficult to fundamentally eliminate the long-term environmental risks of red mud. The CO2 mineralization method usually requires higher temperature and pressure conditions due to its slow reaction kinetics, resulting in high equipment investment and operating energy consumption, which limits its large-scale industrial application. In addition, although the biological dealkalization method has the advantage of being environmentally friendly, its reaction rate is usually relatively slow and the treatment cycle is long. It faces efficiency and scale challenges in actual industrial applications.

[0004] Therefore, there is an urgent need to develop an industrial-scale red mud dealkalization device and method to overcome the shortcomings of the existing technology and realize the resource utilization of red mud. Summary of the Invention

[0005] In order to solve the above technical problems, the first purpose of the present invention is to provide a device for temperature-self-maintaining oxidation-driven dealkalization and soil reconstitution of red mud. Through a vertical reaction device, red mud is synergistically treated with sulfur- or carbon-containing materials such as pyrite, coal or coal gangue. The characteristics of these materials producing acid and heat during the oxidation process are utilized, and the reaction heat is used to achieve temperature self-maintenance, thereby achieving effective dealkalization and property improvement of red mud while reducing energy consumption.

[0006] The second purpose of the present invention is to provide a method for using a device for temperature-self-maintained oxidation-driven dealkalization and soil reconstitution of red mud to carry out ecological treatment of red mud, aiming to solve the problems of high environmental risks and difficulty in resource utilization in existing red mud treatment technologies, and to achieve harmless and ecological utilization of red mud.

[0007] The first object of the present invention is achieved as follows: the vertical reactor comprises a vertical reactor, an agitator, an aeration head, and a monitoring device; the vertical reactor is provided with a feed pipe and an air inlet pipe at the top, and the lower end of the air inlet pipe extends into the bottom of the vertical reactor; the lower end of the air inlet pipe is connected to the aeration head; the vertical reactor is provided with a discharge pipe and an exhaust pipe at the top, and the lower end of the discharge pipe extends into the lower part of the vertical reactor; the vertical reactor is provided with an agitator and a monitoring device.

[0008] Preferably, the monitoring device includes a thermometer, a pressure gauge, a pH sensor, a total dissolved solids sensor, and an oxidation-reduction potential sensor; these monitoring devices all use conventional instruments in the field, and the installation methods and precautions of each instrument are common knowledge in the field and will not be repeated here.

[0009] Preferably, there are multiple vertical reaction devices, and the multiple vertical reaction devices are connected in series or in parallel.

[0010] The second object of the present invention is achieved by comprising the following steps: S1. Mixing red mud with sulfur-containing minerals or carbon-containing minerals to obtain slurry, and feeding the slurry into a vertical reactor through a feed pipe; S2. Oxygen is injected into the slurry at the bottom of the vertical reactor through an air inlet pipe. The agitator continuously stirs the slurry to form an expanded bed. The reaction heat maintains the temperature. Sulfur-containing minerals are oxidized to produce acid, carbon-containing minerals are oxidized to produce acid, and organic matter is converted. The produced acid is neutralized with red mud and dealkalized. S3. The reaction product is discharged through a discharge pipe. After the soluble salt of the reaction product is recovered, it is used as a matrix soil.

[0011] The sulfur-containing minerals of the present invention refer to sulfide or sulfate minerals with a sulfur content greater than 1%; the carbon-containing minerals of the present invention refer to carbonaceous minerals with a carbon content greater than 1%.

[0012] Preferably, in step S1, the red mud is mixed with at least one sulfur-containing mineral or carbon-containing mineral, and in step S2, the vertical reaction device is controlled to maintain a slightly oxidizing atmosphere, a reaction temperature of 50°C to 400°C, and a pressure greater than 0.03 MPa.

[0013] Preferably, the carbon-containing mineral is high-sulfur coal, high-sulfur coal gangue, anthracite, bituminous coal, lignite or coal gangue.

[0014] Preferably, the sulfur-containing mineral is sulfur or pyrite.

[0015] Preferably, the pH of the reaction product of step S3 is ≤ 9.0.

[0016] Preferably, the soluble salt in step S3 is one or more of NaOH, Na2CO3, and NaAlO2.

[0017] Preferably, when there are multiple vertical reactors connected in series, each vertical reactor performs processing according to steps S1 to S2 in sequence, with the reaction product from step S2 of the preceding vertical reactor replacing the red mud from step S1 of the following vertical reactor. After the last vertical reactor completes step S2, step S3 is performed. That is, after the first vertical reactor completes steps S1 and S2, the second vertical reactor performs steps S1 and S2, and so on. The reaction product from step S2 of the preceding vertical reactor can be mixed with minerals in a mixer before being fed into the following vertical reactor to perform step S1.

[0018] When there are multiple vertical reaction devices connected in parallel, each vertical reaction device performs processing according to steps S1 to S3 simultaneously.

[0019] The oxidation of sulfur-containing minerals releases a large amount of reaction heat and sulfuric acid. The sulfuric acid produced by the oxidation reaction in the presence of oxygen and water can effectively neutralize the strong alkalinity of red mud and accelerate the dealkalization process.

[0020] During the oxidation process, sulfur-containing minerals release significant amounts of reaction heat and sulfuric acid, which, depending on the oxidizing atmosphere, can be converted into carbon dioxide, small-molecule organic acids, large-molecule humic acids, and humic substances. Under suitable medium- and low-temperature oxidation conditions, the dissolved organic carbon content in carbon-containing minerals can increase by more than 20 times, and the organic carbon ratio by more than 5 times. This organic matter not only further neutralizes the alkalinity of red mud but also significantly improves its physical and chemical properties, such as increasing water retention, enhancing agglomeration, and improving pore structure and nutrient retention capacity, thereby promoting its reconstitution into soil and supporting vegetation growth.

[0021] Compared with the prior art, the present invention has the following technical effects: the present invention uses a vertical reaction device to blow oxygen into a slurry containing red mud and mixed with sulfur-containing minerals or carbon-containing minerals. Oxygen acts as an oxidant to promote oxidation reactions of the minerals in the slurry, and carbon and sulfur are oxidized. The oxidation reaction is an exothermic reaction, and the heat released can increase and maintain the temperature in the reaction device, thereby achieving self-heating and self-insulation in the reaction process and reducing external energy supply requirements. Oxygen helps to form an expanded bed, enhancing the mixing and mass transfer efficiency of the slurry. The oxidation reaction can transform some harmful components in the red mud and improve its physical and chemical properties, such as reducing alkalinity, improving agglomeration, increasing organic matter content, etc., so that the treated product can be suitable for ecological use, thereby realizing the ecological treatment of red mud. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a schematic structural diagram of the device of Example 1; Figure 2 This is a schematic structural diagram of the device of Example 2; Figure 3 This is a schematic structural diagram of the device of Example 3; In the figure: 1-vertical reactor, 2-agitator, 3-aeration head, 4-feed pipe, 5-air inlet pipe, 6-discharge pipe, 7-exhaust pipe, 8-slurry, 9-mixer. DETAILED DESCRIPTION

[0023] The present invention is further described below with reference to the embodiments and drawings, but the present invention is not limited in any way. Any changes or substitutions made based on the teachings of the present invention fall within the scope of protection of the present invention.

[0024] Example 1 As attached Figure 1 As shown, the device for temperature-self-maintained oxidation-driven red mud dealkalization and soil reconstitution in this embodiment includes a vertical reactor 1, an agitator 2, an aeration head 3, and a monitoring device. The vertical reactor 1 has one, a feed pipe 4 and an air inlet pipe 5 are provided at the upper part of the vertical reactor 1, and the lower end of the air inlet pipe 5 extends to the bottom of the vertical reactor 1, and the lower end of the air inlet pipe 5 is connected to the aeration head 3. The upper part of the vertical reactor 1 is provided with a discharge pipe 6 and an exhaust pipe 7, and the lower end of the discharge pipe 6 extends to the lower part of the vertical reactor 1. The vertical reactor 1 is provided with an agitator 2 and a monitoring device. The monitoring device includes a thermometer, a pressure gauge, a pH sensor, a total dissolved solids sensor, and an oxidation-reduction potential sensor.

[0025] Example 2 As attached Figure 2 As shown, the device for temperature-self-maintained oxidation-driven red mud dealkalization and soil reconstitution in this embodiment is based on Example 1, and the difference from Example 1 is that there are two vertical reaction devices 1, and the vertical reaction devices 1 are connected in series.

[0026] Example 3 As attached Figure 3 As shown, the device for temperature-self-maintained oxidation-driven red mud dealkalization and soil reconstitution in this embodiment is based on Example 1, and the difference from Example 1 is that there are three vertical reaction devices 1, and the vertical reaction devices 1 are connected in parallel.

[0027] Example 4 This embodiment is a method for using the device for temperature-self-maintained oxidation-driven red mud dealkalization and soil reconstitution of embodiment 1, comprising the following steps: S1. Mix red mud and high-sulfur coal gangue (sulfur content 6%, carbon content 10%) to obtain a slurry, and feed the slurry into the vertical reactor 1 through the feed pipe 4; S2. Oxygen is injected into the slurry at the bottom of the vertical reactor 1 through the air inlet pipe 5. The stirrer 2 continuously stirs to form an expanded bed. The high-sulfur coal gangue is oxidized to produce acid and organic matter is converted. The produced acid is neutralized with the red mud to dealkalize and the organic matter is elevated. The vertical reactor 1 is controlled to maintain a slightly oxidizing atmosphere, a reaction temperature of 120°C to 180°C, and a pressure greater than 0.03 MPa. The medium temperature environment of the vertical reactor 1 is self-maintained by utilizing the reaction heat of the oxidation reaction. S3. The pH value of the reaction product is ≤9.0. The reaction product is discharged through the discharge pipe 6. The alkalinity of the reaction product is regulated, the organic matter content is increased, and the agglomeration performance is improved. The sodium salt contained in the reaction product is recovered in the form of NaAlO2 and used as a matrix soil.

[0028] Example 5 This embodiment is a method for using the device for temperature-self-maintained oxidation-driven red mud dealkalization and soil reconstitution of Example 2. The method is based on Example 4, and differs from Example 4 in that: in step S1, red mud and pyrite are mixed to obtain a slurry, and the slurry is fed into a first vertical reactor; in step S2, a slightly oxidizing atmosphere is maintained in the reactor, the reaction temperature is 300°C to 400°C, and the pressure is ≥5 MPa, the pyrite is oxidized to produce acid, and the acid is rapidly neutralized and dealkalized with the red mud; When the pH value of the reaction product is ≤9.0, the reaction product of the first vertical reactor is discharged and mixed with high-sulfur coal (sulfur content 3%, carbon content 70%), and then sent to the second vertical reactor for further treatment according to steps S1 to S3, wherein the reaction temperature is 180°C to 240°C, a slightly oxidizing atmosphere is maintained in the reactor, and the pressure is ≥0.1MPa. The sulfur-containing minerals in the high-sulfur coal gangue are oxidized to produce acid, the carbon-containing minerals are oxidized to produce acid, and organic matter is converted. Neutralization and dealkalization with red mud are continued, and organic matter is increased, and the pH value of the reaction product is further reduced; The sodium salt contained in the reaction product is recovered in the form of NaOH and used as matrix soil after recovery.

[0029] Example 6 This embodiment is a method for using the device for temperature-self-maintained oxidation-driven red mud dealkalization and soil reconstitution in Example 3. The method is based on Example 4, and the differences from Example 4 are as follows: The three vertical reaction devices each simultaneously perform the processes of steps S1 to S3; First vertical reactor: In step S1, red mud and anthracite (95% carbon content) are mixed to obtain a slurry, which is then fed into the first vertical reactor. In step S2, the reaction temperature is 250°C to 350°C, and a strong oxidizing atmosphere and pressure of 2-20 MPa are maintained in the reactor. The carbonaceous minerals in the anthracite are oxidized to produce acid and organic matter is converted, which in turn neutralizes and de-alkalis the red mud, and the organic matter is increased. When the pH of the slurry is ≤9.0, the reaction is stopped and the material is discharged. Second vertical reactor: In step S1, red mud and bituminous coal (80% carbon content) are mixed to obtain a slurry, which is fed into the first vertical reactor. In step S2, the reaction temperature is 150°C to 250°C, and the reactor is maintained in an oxidizing atmosphere with a pressure of 0.1-2 MPa. The carbonaceous minerals in the bituminous coal are oxidized to produce acid and organic matter is converted, which in turn neutralizes and de-alkalis the red mud, and the organic matter is increased. When the pH of the slurry is ≤8.5, the reaction is stopped and the material is discharged. The third vertical reactor: In step S1, red mud and lignite (30% carbon content) are mixed to obtain a slurry, which is fed into the first vertical reactor. In step S2, the reaction temperature is 50°C to 150°C, and the reactor is maintained in a slightly oxidizing atmosphere with a pressure of 0.01-1 MPa. The carbonaceous minerals in the lignite are oxidized to produce acid and organic matter is converted, which is then neutralized with the red mud to cause dealkalization and increase the organic matter content. When the pH of the slurry is ≤8.0, the reaction is stopped and the material is discharged. The sodium salt contained in the reaction product is recovered in the form of Na2CO3. After the reaction product is subjected to controlled oxidation treatment at medium and low temperatures, the alkalinity is stably regulated, the organic matter content is increased, and the agglomeration performance is improved, so it can be used as a matrix soil.

Claims

1. A device for temperature-controlled self-maintained oxidation-driven red mud dealkalization and soil reconstitution, comprising a vertical reaction device (1), an agitator (2), an aeration head (3), and a monitoring device, characterized in that The vertical reaction device (1) is provided with a feed pipe (4) and an air inlet pipe (5) at the upper part, and the lower end of the air inlet pipe (5) extends into the bottom of the vertical reaction device (1), and the lower end of the air inlet pipe (5) is connected to an aeration head (3). The vertical reaction device (1) is provided with a discharge pipe (6) and an exhaust pipe (7) at the upper part, and the lower end of the discharge pipe (6) extends into the lower part of the vertical reaction device (1). The vertical reaction device (1) is provided with an agitator (2) and a monitoring device.

2. The device for temperature-self-maintained oxidation-driven red mud dealkalization and soil reconstitution according to claim 1 is characterized in that The monitoring device includes a thermometer, a pressure gauge, a pH sensor, a total dissolved solids sensor, and an oxidation-reduction potential sensor.

3. The device for temperature-self-maintained oxidation-driven red mud dealkalization and soil reconstitution according to claim 1 is characterized in that There are multiple vertical reaction devices (1), and the multiple vertical reaction devices (1) are connected in series or in parallel.

4. A method for using the device for temperature-self-maintained oxidation-driven red mud dealkalization and soil reconstitution according to any one of claims 1 to 3, characterized in that The following steps are involved: S1. Mixing red mud with sulfur-containing minerals or carbon-containing minerals to obtain a slurry, and feeding the slurry into a vertical reaction device (1) through a feed pipe (4); S2, injecting oxygen into the slurry at the bottom of the vertical reaction device (1) through the air inlet pipe (5), and continuously stirring by the stirrer (2) to form an expanded bed. The reaction heat maintains the temperature by itself, and sulfur-containing minerals are oxidized to produce acid, carbon-containing minerals are oxidized to produce acid, and organic matter is converted. The produced acid is neutralized with the red mud to dealkalize; S3. The reaction product is discharged through the discharge pipe (6). The reaction product is recovered as soluble salt and used as matrix soil.

5. The method of use according to claim 4, characterized in that In step S1, red mud is mixed with at least one sulfur-containing mineral or carbon-containing mineral. In step S2, a micro-oxidation atmosphere is maintained in the vertical reaction device (1), the reaction temperature is 50°C to 400°C, and the pressure is greater than 0.03MPa.

6. The method of use according to claim 4, characterized in that The carbon-containing mineral is high-sulfur coal, high-sulfur coal gangue, anthracite, bituminous coal, lignite or coal gangue.

7. The method of use according to claim 4, characterized in that The sulfur-containing mineral is sulfur or pyrite.

8. The method of use according to claim 4, characterized in that The pH of the reaction product of step S3 is ≤9.

0.

9. The method of use according to claim 4, characterized in that The soluble salt in step S3 is one or more of NaOH, Na2CO3, and NaAlO2.

10. The method of use according to claim 4, characterized in that When there are multiple vertical reaction units connected in series, each vertical reaction unit performs treatment in steps S1 to S2 in sequence, and the red mud in step S1 of the next vertical reaction unit is replaced by the reaction product after the treatment in step S2 of the previous vertical reaction unit. After the treatment in step S2 of the last vertical reaction unit, step S3 is performed. When there are multiple vertical reaction devices connected in parallel, each vertical reaction device performs processing according to steps S1 to S3 simultaneously.

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