Method and device for reducing iron content in process for producing alumina clinker from aluminum ash

Abstract

The invention discloses a method and a device for reducing iron content in a process for producing alumina clinker from aluminum ash, and relates to the technical field of aluminum ash resource utilization, and the method comprises the following steps: mixing a sieved aluminum ash sample with coke powder to prepare a mixture; controlling a gas inlet assembly in the vertical kiln to introduce high-temperature gas into the hearth, so that a preheating section is formed at the upper part in the hearth, and a high-temperature reduction section is formed at the lower part in the hearth; the mixture is added into a hearth through a feeding port in the top of a furnace body, moves downwards under the action of gravity, is gradually heated to 500-800 DEG C in a preheating section, then enters a high-temperature reduction section at the temperature of 1150-1350 DEG C for high-temperature reduction, then is cooled and is discharged from a discharging port, and modified clinker is obtained; and crushing the cooled clinker, carrying out magnetic separation by using a magnetic separator, and separating the magnetic substance from the non-magnetic substance alumina clinker. According to the method, the removal rate of iron in the aluminum ash can reach 85.23-93.61%, and the quality of the aluminum oxide clinker prepared from the aluminum ash is guaranteed.

Description

Technical Field

[0001] This invention relates to the field of aluminum ash resource utilization technology, and in particular to a method and apparatus for reducing iron content in the process of producing alumina clinker from aluminum ash. Background Technology

[0002] Currently, 85% of bauxite is processed into alumina clinker using the Bayer process. During Bayer alumina production, if the iron content in the bauxite is too high, due to the complexity of the iron-containing phases and the uncontrollable nature of the reaction, the iron will flocculate into a colloidal form. Furthermore, Fe will undergo isomorphous substitution with Al, making it difficult for alumina to dissolve, thus affecting the process flow and hindering alumina production. Iron impurities mainly exist in the form of iron oxide, severely impacting the quality of alumina clinker prepared from aluminum ash and limiting the application of aluminum ash in high-value-added products. Currently, methods for removing iron from high-alumina clinker include flotation, magnetic separation, acid leaching, and magnetizing roasting. Magnetizing roasting combines the advantages of mineral processing and pyrometallurgy, enabling efficient resource utilization. Many institutions and universities have conducted in-depth research on iron removal processes for alumina clinker. Alumina recovered from industrial waste generally has a high iron content, and using the disclosed iron removal processes, the traditional Bayer process purification method is costly. Therefore, an improved technology is urgently needed to address this problem in existing technologies. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a method and apparatus for reducing the iron content in the process of producing alumina clinker from aluminum ash.

[0004] To solve the above technical problems, the technical solution of the present invention is as follows: A method for reducing iron content in the process of producing alumina clinker from aluminum ash, comprising: The sieved aluminum ash sample was mixed with coke powder to prepare a mixture. The air intake components in the vertical furnace are controlled to introduce high-temperature gas into the furnace chamber, so that a preheating section is formed in the upper part of the furnace chamber and a high-temperature reduction section is formed in the lower part. The mixture is added into the furnace through the feeding port at the top of the vertical kiln. Under the action of gravity, it moves downward and is gradually heated to 500-800℃ in the preheating section. Then it enters the high-temperature reduction section at 1150-1350℃ for high-temperature reduction. After that, it is cooled and discharged from the discharge port at the bottom of the vertical kiln to obtain modified clinker. The cooled clinker is crushed and then separated into magnetic and non-magnetic alumina clinker by magnetic separation.

[0005] In a preferred embodiment of the method for reducing iron content in the process of producing alumina clinker from aluminum ash according to the present invention, the amount of coke powder added is 1.5-6.4% of the amount of aluminum ash added.

[0006] As a preferred embodiment of the method for reducing iron content in the process of producing alumina clinker from aluminum ash according to the present invention, the mixture is a spherical mixture or a block mixture with a size of 10-40 mm, and a material layer with a porosity of 14-28% is formed in the mixture.

[0007] As a preferred embodiment of the method for reducing iron content in the process of producing alumina clinker from aluminum ash according to the present invention, the high-temperature gas introduced into the furnace by the gas inlet assembly is N2, O2, and CO, and the O2 content is controlled within the range of 6.2-11.7%, the CO content is controlled within the range of 13-38%, and the gas pressure is controlled within the range of 4.6-21 KPa.

[0008] As a preferred embodiment of the method for reducing iron content in the process of producing alumina clinker from aluminum ash according to the present invention, the aluminum ash contains 67.87-83.70% alumina, 2.82-14.40% iron oxide, and 1.35-5.23% aluminum nitride.

[0009] This invention also provides an apparatus for reducing the iron content in the process of producing alumina clinker from aluminum ash, comprising a vertical furnace, wherein the vertical furnace includes: The furnace body has a furnace chamber inside. The top of the furnace body has a feeding port that communicates with the furnace chamber, and the bottom of the furnace body has a discharge port that communicates with the furnace chamber. A magnetic separator is fixedly installed in the discharge port. The air intake assembly includes a gas distributor fixedly installed at the bottom of the furnace and an air intake pipe connected to the gas distributor. The air intake end of the air intake pipe extends to the outside of the furnace body and is connected to the gas supply end. The high-temperature gas generated by the gas distributor flows from the bottom of the furnace to the top of the furnace.

[0010] As a preferred embodiment of the device for reducing iron content in the process of producing alumina clinker from aluminum ash according to the present invention, the air intake assembly further includes a wind cap covering the gas distributor.

[0011] As a preferred embodiment of the device for reducing iron content in the process of producing alumina clinker from aluminum ash according to the present invention, wherein: a temperature measuring device for measuring the temperature inside the furnace and a pressure measuring device for measuring the pressure inside the furnace are fixedly installed on the furnace body.

[0012] As a preferred embodiment of the device for reducing iron content in the process of producing alumina clinker from aluminum ash according to the present invention, wherein: the upper part of the furnace body is provided with an exhaust port communicating with the furnace chamber.

[0013] As a preferred embodiment of the device for reducing iron content in the process of producing alumina clinker from aluminum ash according to the present invention, slag passage holes communicating with the furnace chamber are provided on both sides of the middle part of the furnace body.

[0014] The beneficial effects of this invention are: (1) This invention utilizes waste activated carbon to reduce iron oxide, removes iron by magnetic separation, and prepares high-grade alumina with low iron content, so that the iron content in the alumina clinker is <1%. With the addition of carbon, the iron oxide is reduced to FeO or Fe3O4 with greater magnetic properties by the reduction of carbon monoxide in the atmosphere, and then separated by magnetic separation, thereby reducing the iron content in the alumina product to meet the requirements of high-grade alumina (Fe<1%).

[0015] (2) The removal rate of iron in aluminum ash in this invention can reach 85.23-93.61%, which ensures the quality of alumina clinker prepared from aluminum ash. Attached Figure Description

[0016] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of the device for reducing iron content in the process of producing alumina clinker from aluminum ash provided by the present invention. The components include: 1. Furnace body; 2. Furnace chamber; 3. Inlet pipe; 4. Gas distributor; 5. Air cap; 6. Temperature measuring device; 7. Pressure measuring device; 8. Exhaust port; 9. Slag passage hole; 10. Counterweight airlock valve; 11. Material airlock valve; 12. Feeding port; 13. Discharge port; 14. Magnetic separator. Detailed Implementation

[0018] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0019] This application provides a method for reducing the iron content in the process of producing alumina clinker from aluminum ash, which specifically includes the following steps: Step S101: Mix the sieved aluminum ash sample with coke powder to form a mixture.

[0020] Specifically, the sieved aluminum ash sample is mixed with a certain proportion of coke powder, and then pressed into spherical or blocky mixtures with a size of 10-40mm, forming a material layer with a porosity of 14-28% within the mixture.

[0021] The amount of coke powder added is 1.5-6.4% of the amount of aluminum ash added.

[0022] Step S102: Control the air intake components in the vertical furnace to introduce high-temperature gas into the furnace chamber, so that a preheating section is formed in the upper part of the furnace chamber and a high-temperature reduction section is formed in the lower part.

[0023] Specifically, the air intake components in the vertical furnace introduce high-temperature gas into the furnace chamber. The high-temperature gas consists of N2, O2, and CO, with the O2 content controlled within the range of 6.2-11.7%, the CO content controlled within the range of 13-38%, and the gas pressure controlled within the range of 4.6-21 kPa. This creates a preheating section in the upper part of the furnace chamber and a high-temperature reduction section in the lower part of the furnace chamber.

[0024] Step S103: The mixture is added into the furnace through the feeding port at the top of the vertical kiln body. Under the action of gravity, it moves downward and is gradually heated to 500-800℃ in the preheating section. Then it enters the high-temperature reduction section at 1150-1350℃ for high-temperature reduction. After that, it is cooled and discharged from the discharge port at the bottom of the vertical kiln body to obtain modified clinker.

[0025] Specifically, the mixture is added from the feed inlet at the top of the vertical furnace and moves slowly downwards under gravity, exchanging heat countercurrently with the rising hot gas (rich in CO and N2, and carrying residual heat) in the high-temperature reduction section. The mixture is gradually heated to 500-800℃. During this process, the coke begins to react with a small amount of O2 in the gas stream, generating more CO.

[0026] The preheated mixture enters a high-temperature reduction section at 1150-1350℃. At this point, the mixture temperature has reached the optimal reaction temperature. Reducing gas introduced from below reacts with the mixture in this section, rapidly and fully reducing the non-magnetic iron oxide in the aluminum ash to strongly magnetic FeO and Fe3O4, forming modified clinker. The main reactions are: 3Fe2O3 + CO → 2Fe3O4 + CO2, Fe3O4 + CO → 3FeO + CO2.

[0027] Step S104: Crush the cooled clinker and use a magnetic separator to separate the magnetic and non-magnetic alumina clinker.

[0028] Specifically, after the alumina clinker is crushed, it is sieved through a mesh size of 80-200, and then a magnetic separator is used to separate the magnetic and non-magnetic materials from the alumina clinker.

[0029] In the above technical solution, the iron oxide content in aluminum ash can be reduced to 0.28-0.92%, and the iron removal rate can reach 85.23-93.61%.

[0030] The above technical solution will be further explained below through specific embodiments.

[0031] Example 1: This example provides a method for reducing the iron content in the process of producing alumina clinker from aluminum ash. The original aluminum ash contained 5.23% aluminum nitride, 14.40% iron oxide, and 54.20% alumina. 100 kg of aluminum ash was weighed and mixed with 1.5 kg of coke powder, then pressed into balls with a particle size of 10 mm. The pressed balls were then calcined in a vertical kiln at 1100 ℃ for 2 h. During calcination, N2, O2, and CO gases were introduced from the bottom of the vertical kiln. At this time, the O2 content was 6.2%, the CO content was 13%, the gas pressure was 4.6 kPa, and the porosity of the material layer was 14%. After calcination, the material was cooled at the bottom of the kiln and discharged to obtain modified clinker. The cooled clinker was crushed and sieved through an 80-mesh screen. Magnetic separation was then performed to separate the magnetic and non-magnetic alumina clinker. After magnetic separation, the alumina content in the material was 89.33%, the iron oxide content was 0.92%, and the aluminum nitride content was 0.98%. At this point, the iron removal rate was 93.61%.

[0032] Example 2: This example provides a method for reducing the iron content in the process of producing alumina clinker from aluminum ash. The original aluminum ash contained 4.24% aluminum nitride, 3.86% iron oxide, and 67.87% alumina. 100 kg of aluminum ash was weighed and mixed with 2.7 kg of coke powder, then pressed into balls with a particle size of 20 mm. The pressed balls were then calcined in a vertical kiln at 1200 ℃ for 2.5 h. During calcination, N2, O2, and CO gases were introduced from the bottom of the vertical kiln. At this time, the O2 content was 7.1%, the CO content was 17.4%, the gas pressure was 8.14 kPa, and the porosity of the material layer was 17%. After calcination, the material was cooled at the bottom of the kiln and discharged to obtain modified clinker. The cooled clinker was crushed and sieved through a 100-mesh sieve. Magnetic separation was then used to separate the magnetic and non-magnetic alumina clinker. After magnetic separation, the alumina content in the material was 90.26%, the iron oxide content was 0.57%, and the aluminum nitride content was 0.98%. At this point, the iron removal rate was 85.23%.

[0033] Example 3: This example provides a method for reducing the iron content in the process of producing alumina clinker from aluminum ash. The original aluminum ash contained 4.32% AlN, 5.96% Fe, and 72.23% alumina. 100 kg of aluminum ash was weighed and mixed with 4.1 kg of coke powder, then pressed into balls with a particle size of 25 mm. The pressed balls were then calcined in a vertical kiln at 1250 ℃ for 3 h. During calcination, N2, O2, and CO gases were introduced from the bottom of the vertical kiln. At this time, the O2 content was 9.6%, the CO content was 20.86%, the gas pressure was 13.31 kPa, and the porosity of the material layer was 21%. After calcination, the material was cooled at the bottom of the kiln and discharged to obtain modified clinker. The cooled clinker was crushed and sieved through a 100-mesh sieve. Magnetic separation was then performed to separate the magnetic and non-magnetic alumina clinker. After magnetic separation, the alumina content in the material was 91.74%, the iron oxide content was 0.62%, and the aluminum nitride content was 0.98%. At this point, the iron removal rate was 89.60%.

[0034] Example 4: This example provides a method for reducing the iron content in the process of producing alumina clinker from aluminum ash. The original aluminum ash contained 3.87% AlN, 2.99% iron oxide, and 80.23% alumina. 100 kg of aluminum ash was weighed and mixed with 5.5 kg of coke powder, then pressed into balls with a particle size of 30 mm. The pressed balls were then calcined in a vertical kiln at 1300 ℃ for 3.5 h. During calcination, N2, O2, and CO gases were introduced from the bottom of the vertical kiln. At this time, the O2 content was 10.1%, the CO content was 24.81%, the gas pressure was 17.34 kPa, and the porosity of the material layer was 25%. After calcination, the material was cooled at the bottom of the kiln and discharged to obtain modified clinker. The cooled clinker was crushed and sieved through a 200-mesh screen. Magnetic separation was then performed to separate the magnetic and non-magnetic alumina clinker. After magnetic separation, the alumina content in the material was 91.74%, the iron oxide content was 0.28%, and the aluminum nitride content was 1.22%. At this point, the iron removal rate was 90.64%.

[0035] Example 5: This example provides a method for reducing the iron content in the process of producing alumina clinker from aluminum ash. The original aluminum ash contained 1.35% AlN, 2.82% iron oxide, and 83.70% alumina. 100 kg of aluminum ash was weighed and mixed with 6.4 kg of coke powder, then pressed into balls with a particle size of 40 mm. The pressed balls were then calcined in a vertical kiln at 1350 ℃ for 4 h. During calcination, N2, O2, and CO gases were introduced from the bottom of the vertical kiln. At this time, the O2 content was 11.7%, the CO content was 38%, the gas pressure was 21 kPa, and the porosity of the material layer was 28%. After calcination, the material was cooled at the bottom of the kiln and discharged to obtain modified clinker. The cooled clinker was crushed and sieved through a 200-mesh screen. Magnetic separation was then performed to separate the magnetic and non-magnetic alumina clinker. After magnetic separation, the alumina content in the material was 91.77%, the iron oxide content was 0.41%, and the aluminum nitride content was 0.39%. At this point, the iron removal rate was 85.46%.

[0036] Figure 1 This is a schematic diagram of the device for reducing iron content in the process of producing alumina clinker from aluminum ash provided in this application embodiment. The device includes a vertical furnace, which includes a furnace body 1 and an air inlet assembly.

[0037] Specifically, the furnace body 1 is placed vertically on the ground using a mounting bracket. The length-to-diameter ratio of the furnace body 1 is 3.3-4.2. A furnace chamber 2 is provided inside the furnace body 1. A feeding port 12 communicating with the furnace chamber 2 is provided at the top of the furnace body 1, and a discharge port 13 communicating with the furnace chamber 2 is provided at the bottom of the furnace body 1.

[0038] The air intake assembly includes an air intake pipe 3 fixedly installed at the bottom of the furnace body 1. One end of the air intake pipe 3 is located outside the furnace body 1 and connected to the air supply end outside the furnace body 1. The other end of the air intake pipe 3 extends into the furnace chamber 2 and is connected to a gas distributor 4 located at the bottom of the furnace chamber 2. The high-temperature gas generated by the gas distributor 4 flows from the bottom of the furnace chamber 2 to the top of the furnace chamber 2.

[0039] Among them, the gas flowing out of gas distributor 4 is N2, CO, and O2, and the O2 content is controlled within the range of 6.2-11.7%, and the CO content is controlled within the range of 13-38%.

[0040] Preferably, the air intake assembly also includes a hood 5 covering the gas distributor 4. The hood 5 protects the gas distributor 4. A temperature measuring device 6 for measuring the temperature inside the furnace chamber 2 and a pressure measuring device 7 for measuring the pressure inside the furnace chamber 2 are fixedly installed on the furnace body 1. An exhaust port 8 communicating with the furnace chamber 2 is opened at the upper part of the furnace body 1. Slag passage holes 9 communicating with the furnace chamber 2 are opened on both sides of the middle part of the furnace body 1.

[0041] A counterweight airlock valve 10 is installed at the feed inlet of furnace body 1. This valve opens during feeding, facilitating the operator's feeding process. After feeding is complete, the counterweight on the valve falls under gravity, automatically closing the valve. Simultaneously, a material airlock valve 11 is installed at the discharge outlet 13 of furnace body 1, controlling material receiving and unloading, and regulating the discharge amount.

[0042] In addition, a magnetic separator is fixedly installed at the discharge port 13 of the furnace body 1. In this embodiment, the magnetic separator is an iron remover. The iron remover can magnetically separate the clinker discharged from the discharge port to remove some of the iron from the clinker.

[0043] Therefore, the technical solution of this application utilizes waste activated carbon to reduce iron oxide, removes iron through magnetic separation, and prepares high-grade alumina with low iron content, so that the iron content in the alumina clinker is <1%. Under the carbon addition condition, the iron oxide is reduced to FeO or Fe3O4 with greater magnetic properties through the reduction of carbon monoxide in the atmosphere, and then separated by magnetic separation, thereby reducing the iron content in the alumina product to meet the requirements of high-grade alumina (Fe <1%).

[0044] In addition to the above embodiments, the present invention may have other implementation methods; all technical solutions formed by equivalent substitution or equivalent transformation fall within the protection scope claimed by the present invention.

Claims

1. A method for reducing iron content in the process of producing alumina clinker from aluminum ash, characterized in that: include: The sieved aluminum ash sample was mixed with coke powder to prepare a mixture. The air intake components in the vertical furnace are controlled to introduce high-temperature gas into the furnace chamber, so that a preheating section is formed in the upper part of the furnace chamber and a high-temperature reduction section is formed in the lower part. The mixture is added into the furnace through the feeding port at the top of the vertical kiln. Under the action of gravity, it moves downward and is gradually heated to 500-800℃ in the preheating section. Then it enters the high-temperature reduction section at 1150-1350℃ for high-temperature reduction. After that, it is cooled and discharged from the discharge port at the bottom of the vertical kiln to obtain modified clinker. The cooled clinker is crushed and then separated into magnetic and non-magnetic alumina clinker by magnetic separation.

2. The method for reducing iron content in the process of producing alumina clinker from aluminum ash according to claim 1, characterized in that: The amount of coke powder added is 1.5-6.4% of the amount of aluminum ash added.

3. The method for reducing iron content in the process of producing alumina clinker from aluminum ash according to claim 1, characterized in that: The mixture is a spherical or blocky mixture with a size of 10-40 mm, and a material layer with a porosity of 14-28% is formed within the mixture.

4. The method for reducing iron content in the process of producing alumina clinker from aluminum ash according to claim 1, characterized in that: The high-temperature gas introduced into the furnace (2) by the air intake assembly is N2, O2 and CO, and the O2 content is controlled within the range of 6.2-11.7%, the CO content is controlled within the range of 13-38%, and the gas pressure is controlled within the range of 4.6-21 KPa.

5. The method for reducing iron content in the process of producing alumina clinker from aluminum ash according to claim 1, characterized in that: The aluminum ash contains 67.87-83.70% aluminum oxide, 2.82-14.40% iron oxide, and 1.35-5.23% aluminum nitride.

6. An apparatus for reducing iron content in the process of producing alumina clinker from aluminum ash, characterized in that: Including vertical furnaces, the vertical furnaces include: A furnace body (1) is provided inside a furnace chamber (2). A feeding port (12) communicating with the furnace chamber (2) is opened at the top of the furnace body (1). A discharge port (13) communicating with the furnace chamber (2) is opened at the bottom of the furnace body (1). A magnetic separator (14) is fixedly installed inside the discharge port (13). The air intake assembly includes a gas distributor (4) fixedly installed at the bottom of the furnace (2) and an air intake pipe (3) connected to the gas distributor (4). The air intake end of the air intake pipe (3) extends to the outside of the furnace body (1) and is connected to the gas supply end. The high-temperature gas generated by the gas distributor (4) flows from the bottom of the furnace (2) to the top of the furnace (2).

7. The apparatus for reducing iron content in the process of producing alumina clinker from aluminum ash according to claim 6, characterized in that: The air intake assembly also includes a hood (5) covering the gas distributor (4).

8. The apparatus for reducing iron content in the process of producing alumina clinker from aluminum ash according to claim 6, characterized in that: The furnace body (1) is fixedly equipped with a temperature measuring device (6) for measuring the temperature inside the furnace chamber (2) and a pressure measuring device (7) for measuring the pressure inside the furnace chamber (2).

9. The apparatus for reducing iron content in the process of producing alumina clinker from aluminum ash according to claim 6, characterized in that: The upper part of the furnace body (1) is provided with an exhaust port (8) that communicates with the furnace chamber (2).

10. The apparatus for reducing iron content in the process of producing alumina clinker from aluminum ash according to claim 6, characterized in that: The furnace body (1) has slag passage holes (9) on both sides of the middle part, which are connected to the furnace chamber (2).

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