Aluminum oxide production method based on Bayer process

Abstract

The invention provides an aluminum oxide production method based on a Bayer process, and relates to the technical field of aluminum oxide production, and the aluminum oxide production method comprises the following steps: desiliconizing bauxite to obtain ore pulp; the ore pulp is dissolved out, and dissolved-out slurry is obtained; carrying out settling separation on the dissolved slurry to obtain red mud and fine liquid; tobermorite is prepared from the red mud; cooling the refined liquid, adding aluminum hydroxide seed crystals, and separating out aluminum hydroxide crystals from the refined liquid; settling and separating to obtain solid aluminum hydroxide and liquid; the liquid is a sodium aluminate solution and contains sodium carbonate, sodium oxalate and sodium vanadate impurities; roasting the solid aluminum hydroxide to prepare aluminum oxide; removing redundant moisture in the liquid to obtain an evaporation mother solution; and removing impurities from the evaporation mother liquor, and then recycling to a dissolution process. According to the method, the bauxite is desiliconized, the A / S can be increased, and the low-grade ore meets the dissolution requirement; the tobermorite is prepared from the red mud, and the red mud is utilized.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of alumina production, in particular to an alumina production method based on the Bayer process. BACKGROUND

[0002] The Bayer process is a commonly used process for alumina production, but the current process has low dissolution efficiency for low-grade ore and high energy consumption, which needs to be improved. SUMMARY

[0003] In view of the above problems, the present application provides an alumina production method based on the Bayer process, which aims to solve the technical problems of low dissolution efficiency for low-grade ore and high energy consumption of the current process.

[0004] To achieve the above-mentioned purposes, the present application provides the following technical solutions:

[0005] The present application provides an alumina production method based on the Bayer process, comprising:

[0006] Step S1, desilication of bauxite to obtain a slurry;

[0007] Step S2, dissolving the slurry to obtain a dissolved slurry;

[0008] Step S3, settling and separating the dissolved slurry to obtain red mud and a liquor; snow calcite is prepared from the red mud;

[0009] Step S4, cooling the liquor and adding aluminum hydroxide seeds, and decomposing and precipitating aluminum hydroxide crystals in the liquor;

[0010] Step S5, settling and separating the liquor in which aluminum hydroxide crystals are precipitated to obtain solid aluminum hydroxide and a liquid; the liquid is a sodium aluminate solution containing sodium carbonate, sodium oxalate and sodium vanadate impurities;

[0011] Step S6, calcining the solid aluminum hydroxide to obtain alumina;

[0012] Step S7, removing excess water from the liquid to obtain an evaporation mother liquor; the evaporation mother liquor is reused after impurity removal in the dissolving process.

[0013] In some embodiments of the present application, step S1 comprises: after crushing and wet grinding, the bauxite is floated and desilicated by a flotation machine to obtain a slurry;

[0014] During the flotation desilication, a collector and a depressant are added.

[0015] In some embodiments of the present application, the collector comprises dodecylamine acetate, and the depressant comprises modified cassava starch.

[0016] In some embodiments of the present application, step S2 comprises:

[0017] Step S21, adding circulating mother liquor into the slurry;

[0018] Step S22, preparing a Pt / TiO2 suspension using the Pt / TiO2 nanosheet, mixing the Pt / TiO2 suspension with the slurry obtained in step S21, and dissolving in an ultrasonic reactor to obtain a dissolved slurry.

[0019] In some embodiments of the present application, the ultrasonic reactor generates ultrasonic waves at a frequency of 20 kHz.

[0020] In some embodiments of the present application, the reaction conditions in the ultrasonic reactor are: temperature 245℃, pressure 4.0MPa, and residence time 30min.

[0021] In some embodiments of the present application, step S3 comprises:

[0022] Step S31, adding anionic polyacrylamide to the dissolved slurry, and performing sedimentation separation to obtain red mud;

[0023] Step S32, washing the red mud;

[0024] Step S33, mixing the red mud, silica ash, and water to form granules, and then feeding the granules into a mineralization reactor, and introducing CO2 flue gas to react for 4h to generate tobermorite;

[0025] Step S34, spraying a suspension containing alkali-resistant bacteria capable of secreting calcium carbonate on the surface of the tobermorite and curing.

[0026] In some embodiments of the present application, in step S33, 15% volume concentration CO2 flue gas is introduced into the mineralization reactor, and tobermorite is generated under the conditions of pressure 3.0MPa and temperature 60℃ for 4h.

[0027] In some embodiments of the present application, step S6 comprises:

[0028] Step S61, drying the solid aluminum hydroxide;

[0029] Step S62, preparing a eutectic catalyst suspension, and then mixing the eutectic catalyst suspension with the solid aluminum hydroxide and feeding into a microwave calcination device;

[0030] Step S63, using the microwave calcination device to calcine at a temperature of 750℃ for 40min;

[0031] The frequency of the microwave source of the microwave calcination device is 2.3-2.6GHz.

[0032] In some embodiments of the present application, the eutectic catalyst comprises FeF3-AlF3 eutectic nanoparticles.

[0033] Further features and advantages of the present application will be set forth in the following description. BRIEF DESCRIPTION OF DRAWINGS

[0034] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the attached drawings needed to be used in the embodiments description will be briefly introduced. Obviously, the attached drawings in the following description are only some embodiments of the present application, and for those skilled in the art, other attached drawings can also be obtained without creative labor on the basis of these drawings.

[0035] Figure 1 A flowchart of a Bayer process for producing alumina. DETAILED DESCRIPTION

[0036] In the following, only some exemplary embodiments are simply described. As those skilled in the art can recognize, the described embodiments can be modified in various different ways without departing from the spirit or scope of the embodiments of the present application.

[0037] The embodiments of the present application will be described in detail below.

[0038] Referring to Figure 1 The present embodiment provides a Bayer process for producing alumina, comprising the following steps:

[0039] Step S1, desilication of bauxite to obtain a slurry.

[0040] Step S2, leaching of the slurry to obtain a leaching slurry.

[0041] Step S3, sedimentation separation of the leaching slurry to obtain red mud and a liquor; and preparation of tobermorite from the red mud.

[0042] Step S4, cooling of the liquor and addition of aluminum hydroxide seeds, and decomposition and precipitation of aluminum hydroxide crystals in the liquor.

[0043] Step S5, sedimentation separation of the liquor with the decomposed and precipitated aluminum hydroxide crystals to obtain solid aluminum hydroxide and a liquid. The liquid is a sodium aluminate solution containing sodium carbonate, sodium oxalate and sodium vanadate impurities.

[0044] Step S6, calcination of the solid aluminum hydroxide to obtain alumina.

[0045] Step S7, heating and evaporation of the liquid in a multi-effect evaporator group to remove excess water, and after concentration by evaporation, an evaporation mother liquor is obtained; and the evaporation mother liquor is reused to the leaching process (step S2) after cooling and crystallization to remove impurities.

[0046] The Bayer process-based alumina production method can remove silicon from bauxite, increase A / S (aluminum-silicon ratio), and make low-grade ore meet the dissolution requirements; and the snow calcite prepared from red mud can utilize the red mud.

[0047] Step S1 includes: after the bauxite is crushed and wet ground, the bauxite is desilicated by a flotation machine to obtain a slurry;

[0048] In the desilication by flotation, a collector (dodecylamine acetate 120 g / t) and an inhibitor (modified cassava starch 350 g / t) are added; the air charge of the flotation machine is 1.2 m³ / min.

[0049] In the above scheme, the modified cassava starch selectively adsorbs the surface of kaolinite (the most typical silicon-containing gangue mineral and silicon-containing impurity in bauxite), the dodecylamine acetate enhances the hydrophobicity of diaspore, and the flotation separation efficiency is improved, while the silicon mineral is inhibited and the loss of aluminum is reduced.

[0050] Step S2 includes:

[0051] Step S21, the circulating mother liquor is added to the slurry, and the solid-liquid ratio is controlled to be 1:1.22; and the slurry is preheated to 175℃ ± 5℃.

[0052] Step S22, Pt / TiO2 nanosheets (Pt is loaded on TiO2 nanosheets, 20 nm, and the addition amount is 0.08wt%) are used to prepare a Pt / TiO2 suspension, the Pt / TiO2 suspension is mixed with the slurry obtained in step S21, and dissolution is carried out in an ultrasonic reactor to obtain a dissolution slurry;

[0053] The ultrasonic frequency generated by the ultrasonic reactor is 20 kHz. The reaction conditions in the ultrasonic reactor are: temperature 245℃, pressure 4.0MPa, and residence time 30min.

[0054] Step S23, the dissolution slurry is cooled to 110℃.

[0055] The bond types of diaspore crystals (AlOOH) include Al-O (in the chain, high difficulty in breaking) and Al-OH (between layers, low difficulty in breaking). In the above scheme, when the 20 kHz ultrasonic wave propagates in the slurry, cavitation bubbles are caused to oscillate violently, local transient high temperature is generated, the Al-OH bond breaking rate is increased by the local transient high temperature, and the dissolution rate is improved. Pt / TiO2 can catalyze the breaking of Al-O bonds, so that the dissolution time is shortened.

[0056] Step S3 includes:

[0057] Step S31, the dissolution slurry is sent into a deep-cone settling tank, anionic polyacrylamide (PAM) 40 g / t is added, and settling separation is carried out to obtain red mud.

[0058] Step S32, washing the red mud.

[0059] Step S33, mixing the red mud, silica ash and water to granulate (particle size 5-10 mm), and then feeding into a mineralization reactor, and introducing 15% volume concentration of CO2 gas (pressure 3.0 MPa, temperature 60℃), and reacting for 4h to generate tobermorite.

[0060] Step S34, spraying a suspension on the surface of the tobermorite, and curing for 7 days, the suspension containing alkali-resistant bacteria capable of secreting calcium carbonate.

[0061] In the above scheme, the red mud is subjected to chemical-biological synergistic mineralization: pressurized CO2 accelerates the generation of tobermorite skeleton, and bacteria secrete calcium carbonate to fill the pores of the skeleton, solving the problem of insufficient traditional red mud cementitious activity.

[0062] Step S6 includes:

[0063] Step S61, drying the solid aluminum hydroxide.

[0064] Step S62, preparing a suspension of FeF3-AlF3 eutectic nanoparticles (eutectic catalyst), and feeding the suspension of FeF3-AlF3 eutectic nanoparticles and the solid aluminum hydroxide into a microwave calcination device after mixing in a fluidized bed reactor.

[0065] Step S63, using the microwave calcination device to calcine at a temperature of 750℃ for 40min.

[0066] The frequency of the microwave source of the microwave calcination device is 2.45GHz.

[0067] In the above scheme, under the action of the eutectic catalyst, a low-melting-point eutectic liquid phase is formed at 750℃, accelerating the Al 3+ phase diffusion and reducing the phase transition activation energy. Based on the non-thermal effect of microwaves, 2.45GHz electromagnetic waves resonate with Al-O bonds (resonance frequency 2.3-2.6GHz), reducing the crystal lattice energy barrier, and the conversion temperature of α-Al2O3 is reduced from 1000℃ to 750℃.

[0068] Finally, it should be noted that the above is only a preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application can have various modifications and changes, and the embodiments of the present application and the features in the embodiments can be arbitrarily combined without conflict. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A method for producing aluminum oxide based on the Bayer process, characterized in that: The steps include: Step S1, desiliconizing bauxite to obtain slurry; Step S2, dissolving the ore pulp to obtain a dissolution slurry; Step S3, subjecting the dissolved slurry to sedimentation separation to obtain red mud and semen; and preparing tobermorite from the red mud; Step S4, cooling the semen and adding aluminum hydroxide seed crystals to separate aluminum hydroxide crystals from the semen; Step S5, subjecting the semen from which aluminum hydroxide crystals are separated to sedimentation separation to obtain solid aluminum hydroxide and liquid; the liquid is a sodium aluminate solution containing sodium carbonate, sodium oxalate, and sodium vanadate as impurities; Step S6, calcining the solid aluminum hydroxide to obtain aluminum oxide; Step S7: removing excess water from the liquid to obtain an evaporated mother liquor; and recycling the evaporated mother liquor to the dissolution process after removing impurities.

2. The method for producing alumina based on the Bayer process according to claim 1, wherein: Step S1 comprises: crushing and wet grinding the bauxite, and then flotating and desiliconizing the bauxite using a flotation machine to obtain a pulp; During flotation desiliconization, collectors and depressants are added.

3. The method for producing alumina based on the Bayer process according to claim 2, characterized in that: The collector includes laurylamine acetate, and the inhibitor includes modified cassava starch.

4. The method for producing alumina based on the Bayer process according to claim 1, wherein: Step S2 includes: Step S21: adding circulating mother liquor to the slurry; Step S22: Prepare a Pt / TiO2 suspension using Pt / TiO2 nanosheets, mix the Pt / TiO2 suspension with the slurry obtained in step S21, and dissolve them in an ultrasonic reactor to obtain a dissolved slurry.

5. The method for producing alumina based on the Bayer process according to claim 4, characterized in that: The ultrasonic wave frequency generated by the ultrasonic reactor is 20 kHz.

6. The method for producing alumina based on the Bayer process according to claim 5, characterized in that: The reaction conditions in the ultrasonic reactor are: temperature 245° C., pressure 4.0 MPa, and residence time 30 min.

7. The method for producing alumina based on the Bayer process according to claim 1, characterized in that: Step S3 includes: Step S31, adding anionic polyacrylamide to the dissolution slurry, performing sedimentation separation to obtain red mud; Step S32, washing red mud; Step S33: After mixing red mud, silica fume and water into granules, the mixture is fed into a mineralization reactor, CO2 flue gas is introduced, and the mixture is reacted for 4 hours to generate tobermorite; Step S34: spraying a suspension containing alkali-resistant bacteria capable of secreting calcium carbonate on the surface of the tobermorite and curing the surface.

8. The method for producing alumina based on the Bayer process according to claim 7, characterized in that: In step S33, CO2 flue gas with a volume concentration of 15% is introduced into the mineralization reactor, and the reaction is carried out for 4 hours at a pressure of 3.0 MPa and a temperature of 60°C to generate tobermorite.

9. The method for producing alumina based on the Bayer process according to claim 1, characterized in that: Step S6 includes: Step S61, drying solid aluminum hydroxide; Step S62: preparing a eutectic catalyst suspension, mixing the eutectic catalyst suspension with solid aluminum hydroxide, and then feeding the mixture into a microwave roasting device; Step S63: using microwave roasting equipment at 750° C. for 40 minutes; The frequency of the microwave source of the microwave roasting equipment is: 2.3~2.6GHz.

10. The method for producing alumina based on the Bayer process according to claim 9, characterized in that: The eutectic catalyst includes FeF3-AlF3 eutectic nanoparticles.

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