Method for preparing hercynite through microwave activation of fly ash

Abstract

The invention discloses a method for preparing hercynite by microwave-activated fly ash, which comprises the following steps: by taking fly ash, ferric oxide and pulverized coal as main raw materials, carrying out mixing, anaerobic microwave activation, ball milling and high-pressure alkaline leaching procedures to realize removal of silicon in the fly ash so as to prepare the hercynite. The method effectively solves the problems that silicon and aluminum in the fly ash are difficult to separate, the treatment process is long, the temperature is high, the time is long and the like, and effectively realizes high-value resource utilization of the fly ash. The method has the characteristics of simple process, low reaction temperature, short reaction time and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of solid waste resource utilization, in particular to a method for preparing ferroaluminum spinel by microwave-activated fly ash. Background Art

[0002] Fly ash is a typical major solid waste in my country, with enormous production and reserves, posing a serious threat to the ecological environment and human health. The main components of fly ash are aluminum oxide and silicon oxide, accounting for over 90%, making the silicon and aluminum substances in it highly promising for resource utilization. To achieve the disposal and high-value resource utilization of fly ash, research paths have been established in various fields, including mine backfill, cement admixture, building materials production, and alkaline / acid aluminum extraction. However, due to the dense silicon and aluminum intercalation in fly ash and the large batch-to-batch variability in quality, a large-scale industry has yet to emerge. Therefore, new paths for high-value resource utilization of fly ash are still needed.

[0003] The “Method for Selecting Coal-Based Solid Waste Functional Filling Materials” published in Chinese patent CN115506843A realizes the functional filling of mines by selecting different coal-based solid wastes such as fly ash based on the geological conditions of the mines. This method can achieve the large-scale disposal of fly ash, but different mine conditions have different requirements for the quality of fly ash, and the applicable scenarios of the invention are limited. The “Microfiltration Ceramic Membrane and Its Preparation Method” published in Chinese patent CN108585883A controls the proportion of fly ash, binder, and pore-forming agent, and produces a microfiltration ceramic membrane with a pore size of 0.01-10μm after medium and high temperature sintering. This method can achieve high-value utilization of fly ash, but the output of fly ash in the ratio is limited, and the market demand for microfiltration ceramic membranes is limited, making it impossible to achieve large-scale utilization of fly ash. Chinese patent CN108892146A discloses a "method for desiliconizing silicon-aluminum materials." This involves adding iron oxide and carbon, followed by a reduction roasting process at 1050-1200°C and an oxidation roasting process at 900-1000°C, followed by a two-stage alkaline leaching process to separate aluminum from silicon. This method effectively separates aluminum from silicon, but the long process flow and high reaction temperature make it difficult to achieve economic efficiency. None of the above systematic solutions can completely solve the problem of fly ash disposal and large-scale utilization. Therefore, consideration can be given to using fly ash as a primary raw material to prepare secondary raw materials, broadening its application scenarios and achieving efficient resource utilization of fly ash. Summary of the Invention

[0004] The present invention aims to provide a method for preparing ferroaluminous spinel from fly ash through microwave activation. After adding ferric oxide and pulverized coal to the fly ash, the ferroaluminous spinel is prepared through ball milling, oxygen-free microwave activation, ball milling, and high-pressure alkaline leaching for desiliconization. Ferroaluminous spinel can be used as a refractory material. Its extremely high aluminum-silicon ratio also offers excellent prospects for the extraction of alumina, making it a high-value fly ash resource with multiple applications.

[0005] In order to achieve the above objectives, this application adopts the following technical solutions: The present invention provides a method for preparing ferroaluminum spinel by microwave-activated fly ash. The method uses fly ash, ferric oxide and coal powder as main raw materials, and removes silicon from the fly ash through mixing, oxygen-free microwave activation, ball milling and high-pressure alkali leaching to prepare the ferroaluminum spinel.

[0006] In the above technical solution, the specific method includes the following steps: Step (1), mixing: placing fly ash, ferric oxide and coal powder in a ball mill and mixing them evenly to obtain a mixture; Step (2), anaerobic microwave activation: placing the mixed material obtained in step (1) in a microwave oven for anaerobic activation to obtain an activated material; Step (3), ball milling: placing the activated material obtained in step (2) in a ball mill for ball milling to obtain a ball-milled material; Step (4), high-pressure alkali leaching: placing the sodium hydroxide solution and the ball mill obtained in step (3) in a high-pressure reactor and reacting them in a homogeneous reactor, filtering and drying the solid to obtain the iron-aluminum spinel.

[0007] In the above technical solution, the alumina content in the fly ash is ≥45%. Fly ash with an alumina content of ≥45% is considered high-alumina fly ash and has a better effect in forming ferroaluminum spinel.

[0008] In the above technical solution, the molar ratio of aluminum oxide to ferric oxide and coal powder in the fly ash is 2:1.1:1.1. The theoretical reaction ratio is 2:1:1, and 2:1.1:1.1 is the optimal ratio in actual production. If the ferric oxide content is increased, not only will tailings increase, but it will also hinder the contact between the fly ash and coal powder, affecting the crystallinity of the ferroaluminum spinel.

[0009] In the above technical solution, step (1) adopts dry grinding, wherein the ball-to-material ratio is (1:1)-(2:1), and the ball milling time is 2-6 hours.

[0010] In the above technical solution, in the oxygen-free microwave activation in step (2), the microwave power is set to 1000.00-3000.00W, nitrogen is introduced, and after the air is exhausted, the temperature is raised from room temperature at a heating rate of 5-10°C / min to 700-900°C, maintained for 10-30 minutes, and nitrogen is continued to be introduced until the furnace cools to 100°C. Subsequently, the nitrogen is disconnected and the furnace is naturally cooled to room temperature.

[0011] In the above technical solution, in the ball milling in step (3), the particle size of the ball mill material is not less than 200 mesh.

[0012] In the above technical solution, in the high-pressure alkaline leaching in step (4), the concentration of sodium hydroxide is 160-400 g / L, the liquid-to-solid ratio is 8-15, the speed of the homogeneous reactor is 20-100 r / min, the reaction temperature is 130-200°C, and the reaction time is 60-180 min.

[0013] The present invention provides a method for preparing ferroaluminum spinel from fly ash activated by microwaves, effectively resolving issues such as the difficulty in separating aluminum and silicon from fly ash, the lengthy processing process, high temperatures, and time required, and effectively realizing high-value resource utilization of fly ash. The method also features a simple process, low reaction temperature, and short reaction time. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 The present invention is a flow chart of a method for preparing ferroaluminum spinel by microwave-activated fly ash. DETAILED DESCRIPTION

[0015] In order to better illustrate the purpose, technical solutions and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments. The present invention can be implemented in many different forms and should not be construed as limited to the embodiments set forth herein. On the contrary, these embodiments are provided so that this disclosure will be thorough and complete and will fully convey the concept of the present invention to those skilled in the art. The present invention will be limited only by the claims.

[0016] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods.

[0017] This invention aims to achieve high-value resource utilization of fly ash. After adding ferric oxide and coal powder, the aluminum oxide and ferrous oxide formed by the reaction are activated by oxygen-free microwaves to produce ferroaluminum spinel, laying the foundation for subsequent aluminum oxide extraction or refractory material preparation. The main technical solutions are as follows: Fly ash, ferric oxide, and pulverized coal are used as the main raw materials, wherein the alumina content in the fly ash is ≥45%, and the molar ratio of alumina to ferric oxide and pulverized coal in the fly ash is 2:1.1:1.1. The ferroalumina spinel is prepared through ball milling, oxygen-free microwave activation, ball milling, high-pressure alkaline leaching and desiliconization. The main steps are: (1) Ball milling: The weighed fly ash, ferric oxide and coal powder are ball milled using a dry grinding method, wherein the ball-to-material ratio is (1:1)-(2:1) and the ball milling time is 2-6 h to obtain a mixture.

[0018] (2) Anaerobic microwave activation: The mixed material obtained in step (1) is placed in an industrial microwave oven for anaerobic activation. The microwave power is set to 1000.00-3000.00 W, nitrogen is introduced, and after exhausting the air, the temperature is increased from room temperature at a heating rate of 5-10 °C / min. After the temperature reaches 700-900 °C, it is maintained for 10-30 min. Nitrogen is continued to be introduced until the furnace cools to 100 °C. Subsequently, the nitrogen is disconnected and the mixture is naturally cooled to room temperature to obtain the activated material.

[0019] (3) Ball milling: The activated material obtained in step (2) is placed in a ball mill for ball milling until the particle size of the activated material is not less than 200 meshes, thereby obtaining a ball milled material.

[0020] (4) High-pressure alkali leaching: Place the sodium hydroxide alkaline solution and the ball mill obtained in step (3) in a high-pressure reactor and react in a homogeneous reactor, wherein the sodium hydroxide concentration is 160-400 g / L, the liquid-to-solid ratio is 8-15, the speed of the homogeneous reactor is 20-100 r / min, the reaction temperature is 130-200°C, and the reaction time is 60-180 min. The solid is filtered and dried to obtain iron-aluminum spinel.

[0021] Example 1 Fly ash, ferric oxide, and pulverized coal are used as the main raw materials, wherein the alumina content in the fly ash is 48.6%, and the molar ratio of alumina to ferric oxide and pulverized coal in the fly ash is 2:1.1:1.1. The ferroalumina spinel is prepared through ball milling, oxygen-free microwave activation, ball milling, high-pressure alkaline leaching and desiliconization. The main steps are: (1) Ball milling: The weighed fly ash, ferric oxide and coal powder were ball milled using a dry grinding method with a ball-to-material ratio of 1:1 and a ball milling time of 3 h to obtain a mixed material.

[0022] (2) Anaerobic microwave activation: The mixed material obtained in step (1) was placed in an industrial microwave oven for anaerobic activation. The microwave power was set to 2000.00 W, nitrogen was introduced, and after exhausting the air, the temperature was raised from room temperature at a heating rate of 5 °C / min. After reaching 900 °C, the temperature was maintained for 30 min. Nitrogen was continued to be introduced until the furnace cooled to 100 °C. Subsequently, the nitrogen was disconnected and the mixture was naturally cooled to room temperature to obtain the activated material.

[0023] (3) Ball milling: The activated material obtained in step (2) is placed in a ball mill for ball milling until the particle size of the activated material can pass through a 200-mesh sieve to obtain a ball-milled material.

[0024] (4) High-pressure alkali leaching: The sodium hydroxide alkaline solution and the ball mill obtained in step (3) were placed in a high-pressure reactor and reacted in a homogeneous reactor. The sodium hydroxide concentration was 320 g / L, the liquid-to-solid ratio was 12, the speed of the homogeneous reactor was 50 r / min, the reaction temperature was 150 °C, and the reaction time was 120 min. The solid was filtered and dried to obtain iron-aluminum spinel.

[0025] The Al2O3 content of the obtained ferroaluminum spinel is 49.3%, the SiO2 content is 3.2%, and the Fe2O3 content is 40.9%.

[0026] Example 2 Fly ash, ferric oxide, and pulverized coal are used as the main raw materials, wherein the alumina content in the fly ash is 45.2%, and the molar ratio of alumina to ferric oxide and pulverized coal in the fly ash is 2:1.1:1.1. The ferroalumina spinel is prepared through ball milling, oxygen-free microwave activation, ball milling, high-pressure alkaline leaching and desiliconization. The main steps are: (1) Ball milling: The weighed fly ash, ferric oxide and coal powder were ball milled using a dry grinding method with a ball-to-material ratio of 1:1 and a ball milling time of 3 h to obtain a mixed material.

[0027] (2) Anaerobic microwave activation: The mixture obtained in step (1) was placed in an industrial microwave oven for anaerobic activation. The microwave power was set to 1500.00 W, nitrogen was introduced, and after exhausting the air, the temperature was raised from room temperature at a heating rate of 5 °C / min. After reaching 850 °C, the temperature was maintained for 20 min. Nitrogen was continued to be introduced until the furnace cooled to 100 °C. Subsequently, the nitrogen was disconnected and the mixture was naturally cooled to room temperature to obtain the activated material.

[0028] (3) Ball milling: The activated material obtained in step (2) is placed in a ball mill for ball milling until the particle size of the activated material can pass through a 200-mesh sieve to obtain a ball-milled material.

[0029] (4) High-pressure alkali leaching: The sodium hydroxide alkaline solution and the ball mill obtained in step (3) were placed in a high-pressure reactor and reacted in a homogeneous reactor, wherein the sodium hydroxide concentration was 400 g / L, the liquid-to-solid ratio was 10, the homogeneous reactor speed was 80 r / min, the reaction temperature was 130 °C, and the reaction time was 180 min. The solid was filtered and dried to obtain iron-aluminum spinel.

[0030] The Al2O3 content of the obtained ferroaluminum spinel is 51.3%, the SiO2 content is 4.8%, and the Fe2O3 content is 38.9%.

[0031] Example 3 Fly ash, ferric oxide, and pulverized coal are used as the main raw materials, wherein the alumina content in the fly ash is 46.9%, and the molar ratio of alumina to ferric oxide and pulverized coal in the fly ash is 2:1.1:1.1. The ferroalumina spinel is prepared through ball milling, oxygen-free microwave activation, ball milling, high-pressure alkaline leaching and desiliconization. The main steps are: (1) Ball milling: The weighed fly ash, ferric oxide and coal powder were ball milled using a dry grinding method with a ball-to-material ratio of 2:1 and a ball milling time of 6 h to obtain a mixed material.

[0032] (2) Anaerobic microwave activation: The mixed material obtained in step (1) was placed in an industrial microwave oven for anaerobic activation. The microwave power was set to 3000.00 W, nitrogen was introduced, and after exhausting the air, the temperature was raised from room temperature at a heating rate of 8 °C / min. After reaching 700 °C, the temperature was maintained for 30 min. Nitrogen was continued to be introduced until the furnace cooled to 100 °C. Subsequently, the nitrogen was disconnected and the mixture was naturally cooled to room temperature to obtain the activated material.

[0033] (3) Ball milling: The activated material obtained in step (2) is placed in a ball mill for ball milling until the particle size of the activated material can pass through a 300-mesh sieve to obtain a ball-milled material.

[0034] (4) High-pressure alkali leaching: The sodium hydroxide alkaline solution and the ball mill obtained in step (3) were placed in a high-pressure reactor and reacted in a homogeneous reactor. The sodium hydroxide concentration was 240 g / L, the liquid-solid ratio was 15, the speed of the homogeneous reactor was 20 r / min, the reaction temperature was 200 °C, and the reaction time was 150 min. The solid was filtered and dried to obtain iron-aluminum spinel.

[0035] The Al2O3 content of the obtained ferroaluminum spinel is 44.3%, the SiO2 content is 3.5%, and the Fe2O3 content is 42.9%.

[0036] Example 4 Fly ash, ferric oxide, and pulverized coal are used as the main raw materials, wherein the alumina content in the fly ash is 50.4%, and the molar ratio of alumina to ferric oxide and pulverized coal in the fly ash is 2:1.1:1.1. The ferroalumina spinel is prepared through ball milling, oxygen-free microwave activation, ball milling, high-pressure alkaline leaching and desiliconization. The main steps are: (1) Ball milling: The weighed fly ash, ferric oxide and coal powder were ball milled using a dry grinding method with a ball-to-material ratio of 1:1 and a ball milling time of 2 h to obtain a mixed material.

[0037] (2) Anaerobic microwave activation: The mixed material obtained in step (1) was placed in an industrial microwave oven for anaerobic activation. The microwave power was set to 1000.00.00 W, nitrogen was introduced, and after exhausting the air, the temperature was raised from room temperature at a heating rate of 5 °C / min. After reaching 900 °C, the temperature was maintained for 10 min. Nitrogen was continued to be introduced until the furnace cooled to 100 °C. Subsequently, the nitrogen was disconnected and the mixture was naturally cooled to room temperature to obtain the activated material.

[0038] (3) Ball milling: The activated material obtained in step (2) is placed in a ball mill for ball milling until the particle size of the activated material can pass through a 200-mesh sieve to obtain a ball-milled material.

[0039] (4) High-pressure alkali leaching: The sodium hydroxide alkaline solution and the ball mill obtained in step (3) were placed in a high-pressure reactor and reacted in a homogeneous reactor. The sodium hydroxide concentration was 160 g / L, the liquid-to-solid ratio was 14, the speed of the homogeneous reactor was 80 r / min, the reaction temperature was 150 °C, and the reaction time was 90 min. The solid was filtered and dried to obtain iron-aluminum spinel.

[0040] The Al2O3 content of the obtained ferroaluminum spinel is 54.3%, the SiO2 content is 2.3%, and the Fe2O3 content is 40.9%.

[0041] Example 5 Fly ash, ferric oxide, and pulverized coal are used as the main raw materials, wherein the alumina content in the fly ash is 47.3%, and the molar ratio of alumina to ferric oxide and pulverized coal in the fly ash is 2:1.1:1.1. The ferroalumina spinel is prepared through ball milling, oxygen-free microwave activation, ball milling, high-pressure alkaline leaching and desiliconization. The main steps are: (1) Ball milling: The weighed fly ash, ferric oxide and coal powder were ball milled using a dry grinding method with a ball-to-material ratio of 2:1 and a ball milling time of 5 h to obtain a mixed material.

[0042] (2) Anaerobic microwave activation: The mixed material obtained in step (1) was placed in an industrial microwave oven for anaerobic activation. The microwave power was set to 2000.00 W, nitrogen was introduced, and after exhausting the air, the temperature was raised from room temperature at a heating rate of 10 °C / min. After reaching 800 °C, the temperature was maintained for 20 min. Nitrogen was continued to be introduced until the furnace cooled to 100 °C. Subsequently, the nitrogen was disconnected and the mixture was naturally cooled to room temperature to obtain the activated material.

[0043] (3) Ball milling: The activated material obtained in step (2) is placed in a ball mill for ball milling until the particle size of the activated material can pass through a 200-mesh sieve to obtain a ball-milled material.

[0044] (4) High-pressure alkali leaching: The sodium hydroxide alkaline solution and the ball mill obtained in step (3) were placed in a high-pressure reactor and reacted in a homogeneous reactor, wherein the sodium hydroxide concentration was 400 g / L, the liquid-to-solid ratio was 8, the homogeneous reactor speed was 50 r / min, the reaction temperature was 150°C, and the reaction time was 60 min. The solid was filtered and dried to obtain iron-aluminum spinel.

[0045] The Al2O3 content of the obtained ferroaluminum spinel is 50.3%, the SiO2 content is 2.9%, and the Fe2O3 content is 43.8%.

[0046] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. Those skilled in the art will readily appreciate that other variations or modifications based on the above descriptions are possible. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. A method for preparing ferroaluminum spinel from fly ash by microwave activation, characterized in that: Using fly ash, ferric oxide and coal powder as the main raw materials, the silicon in the fly ash is removed through mixing, oxygen-free microwave activation, ball milling and high-pressure alkaline leaching to prepare iron-aluminum spinel. The specific method includes the following steps: Step (1), mixing: placing fly ash, ferric oxide and coal powder in a ball mill and mixing them evenly to obtain a mixture; Step (2), anaerobic microwave activation: placing the mixed material obtained in step (1) in a microwave oven for anaerobic activation to obtain an activated material; Step (3), ball milling: placing the activated material obtained in step (2) in a ball mill for ball milling to obtain a ball-milled material; Step (4), high-pressure alkali leaching: placing the sodium hydroxide solution and the ball mill obtained in step (3) in a high-pressure reactor and reacting them in a homogeneous reactor, filtering and drying the solid to obtain the iron-aluminum spinel.

2. The method according to claim 1, wherein: The alumina content in fly ash is ≥45%.

3. The method according to claim 2, wherein: The molar ratio of alumina to ferric oxide and coal powder in fly ash is 2:1.1:1.

1.

4. The method according to claim 1, wherein: Step (1) adopts dry grinding method, wherein the ball-to-material ratio is (1:1)-(2:1), and the ball milling time is 2-6 h.

5. The method according to claim 1, wherein: In step (2), the microwave power is set to 1000.00-3000.00W, nitrogen is introduced, and after the air is exhausted, the temperature is increased from room temperature to 700-900°C at a heating rate of 5-10°C / min, and the temperature is maintained for 10-30 min. Nitrogen is continued to be introduced until the furnace cools to 100°C, and then the nitrogen is disconnected and the mixture is naturally cooled to room temperature.

6. The method according to claim 1, wherein: In the ball milling in step (3), the particle size of the ball mill material is not less than 200 mesh.

7. The method according to claim 1, characterized in that: In the high-pressure alkaline leaching in step (4), the concentration of sodium hydroxide is 160-400 g / L, the liquid-to-solid ratio is 8-15, the speed of the homogeneous reactor is 20-100 r / min, the reaction temperature is 130-200 °C, and the reaction time is 60-180 min.

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