Method for extracting iron from high-iron bauxite by taking biomass as clean reducing agent

Abstract

The invention belongs to the technical field of metallurgy and biomass utilization, and particularly relates to a method for extracting iron from high-iron bauxite by taking biomass as a clean reducing agent. The method comprises the following steps: (1) uniformly mixing high-iron bauxite and biomass, heating to 600-700 DEG C under an anaerobic condition, and roasting to obtain a roasted material; (2) dissolving out the roasted material obtained in the step (1) by adopting a Bayer process to obtain solid slag and a dissolved-out solution; and (3) the solid slag obtained in the step (2) is subjected to magnetic separation, and iron ore concentrate is obtained. According to the method, the high-iron bauxite and the biomass are uniformly mixed and then are subjected to high-temperature reduction under the inert atmosphere condition, hematite is reduced into magnetite in the process, then the iron ore concentrate and the red mud with extremely low iron and aluminum content are obtained through the dissolution and magnetic separation process, and the iron ore concentrate can be used as an ironmaking raw material. The comprehensive utilization of the high-iron bauxite and the biomass is realized, and the utilization problem of iron resources in the high-iron bauxite is solved.

Description

Technical Field

[0001] The invention belongs to the technical field of metallurgy and biomass utilization, and specifically relates to a method for extracting iron from high-iron bauxite by using biomass as a clean reducing agent. Background Art

[0002] The Bayer process is a widely used industrial method for producing alumina from bauxite. In the traditional Bayer process, alumina is extracted by mixing bauxite with sodium aluminate solution for high-temperature dissolution. At the same time, in order to ensure the dissolution rate of alumina, calcium oxide of 8% of the dry ore mass needs to be added for dissolution, which results in about 1.2 tons of red mud for every ton of alumina produced. Red mud contains a large amount of iron resources, and its iron oxide content is as high as 30% to 40%, but the current utilization rate of red mud is less than 5%, and iron resources cannot be effectively recycled. Damming and stockpiling is the main treatment method for red mud, which leads to a double waste of land resources and mineral resources. Therefore, it is of great practical significance to realize the comprehensive utilization of iron resources in high-iron bauxite, and it can also provide a new way for the development and utilization of strategic metal resources such as iron.

[0003] In recent years, there have been many reports on the comprehensive utilization of iron resources in bauxite. CN110760637A proposes a method for recovering iron from high-iron bauxite. In this method, high-iron bauxite powder is placed in a closed reduction furnace, and flare gas (waste gas generated in the process of the petrochemical industry, with a relatively complex composition, mainly containing carbon atoms, hydrogen and hydrocarbons) is introduced into the furnace for heating and reduction to obtain a reduced material. After the reduced material is ground, it is subjected to magnetic separation to obtain a magnetic concentrate and a magnetic tailing; the magnetic concentrate is an iron concentrate, and the magnetic tailing is an alumina-enriched ore. CN110093514A proposes a method for comprehensive utilization of iron and aluminum separation of high-iron bauxite, which grinds the high-iron bauxite to a certain particle size and then puts it into an acid solution for leaching, wherein the leaching acid concentration is 1 mol / L to 6 mol / L, the leaching solid-liquid ratio is 1:20 to 3:10, the leaching temperature is 50 to 100°C, and the leaching time is 30 min to 360 min. The leached pulp is separated into solid and liquid, and the solid slag is the tailings, which is discharged. The acid leaching solution is a solution containing iron and aluminum, and the iron and aluminum separation is achieved by adjusting the pH of the solution to recover mineral resources.

[0004] The above invention patent recovers iron resources from high-iron bauxite by roasting reduction or acid leaching. The disadvantages are that the reaction process is relatively complicated and the reaction conditions are relatively harsh. The most important thing is that the magnetic separation followed by the dissolution process and the acid leaching process will lead to incomplete separation of iron and aluminum, reducing the utilization rate of resources. Summary of the invention

[0005] In view of the shortcomings and deficiencies of the above prior art, the purpose of the present invention is to provide a method for extracting iron from high-iron bauxite using biomass as a clean reducing agent. The method of the present invention is to uniformly mix high-iron bauxite with biomass and then reduce it at high temperature under inert atmosphere conditions. In this process, hematite is reduced to magnetite, and then iron concentrate and red mud with extremely low iron and aluminum content are obtained through dissolution and magnetic separation. The iron concentrate can be used as a raw material for ironmaking.

[0006] The purpose of the present invention is achieved through the following technical solutions:

[0007] A method for extracting iron from high-iron bauxite using biomass as a clean reducing agent comprises the following steps:

[0008] (1) mixing high-iron bauxite and biomass uniformly, heating to 600-700° C. under oxygen-free conditions, and roasting to obtain a roasted material;

[0009] (2) dissolving the calcined material obtained in step (1) by using the Bayer process to obtain solid slag and dissolving liquid;

[0010] (3) subjecting the solid slag obtained in step (2) to magnetic separation to obtain iron ore concentrate.

[0011] Furthermore, the biomass in step (1) includes bamboo powder, straw, and corn cobs.

[0012] Furthermore, the mass ratio of the high-iron bauxite and the biomass mixed in step (1) is 10 to 40:1.

[0013] Furthermore, the anaerobic condition in step (1) refers to an inert atmosphere such as nitrogen or argon.

[0014] Furthermore, the calcination time in step (1) is 10 to 30 minutes.

[0015] Furthermore, the method for dissolution using the Bayer process in step (2) is as follows:

[0016] The calcined material and calcium oxide are added together into a sodium aluminate solution with a sodium oxide concentration of 200-250 g / L, an aluminum oxide concentration of 100-150 g / L, and an αK (caustic ratio) of 2.5-4 to prepare a slurry; the slurry is then subjected to a two-stage stirring dissolution reaction, wherein the first stage is stirred at 90-110°C for 1-3 hours, and the second stage is stirred at 250-270°C for 1-1.5 hours. After the reaction is completed, the mixture is naturally cooled to room temperature, and the solid-liquid is separated to obtain solid slag and dissolution liquid.

[0017] Preferably, the mass ratio of the calcined material to calcium oxide is 100:4-8; the solid-liquid mass ratio of the calcined material and calcium oxide added together to the sodium aluminate solution is 1:4-5.

[0018] Preferably, the stirring speed of the two-stage stirring dissolution reaction is 300-500 rpm.

[0019] Preferably, the solid-liquid separation is carried out by suction filtration, and the obtained solid residue is further washed with hot water and then dried and crushed.

[0020] Furthermore, the dissolving solution in step (2) is decomposed by seeds to obtain aluminum hydroxide and a circulating mother liquor, and the circulating mother liquor is recycled after being formulated.

[0021] Furthermore, the magnetic separation in step (3) is performed using a magnetic separator with a magnetic field strength of 175 to 275 mT. The magnetically separated tailings are a silicon-rich red mud phase.

[0022] Furthermore, the iron grade of the iron concentrate obtained in step (3) is greater than 55%, and the iron recovery rate (the percentage of the iron content in the obtained iron concentrate to the iron content in the high-iron bauxite) is greater than 80%. The obtained iron concentrate can be directly used as an ironmaking material.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] (1) The process and equipment used in the method of the present invention are simple. The iron and aluminum resources in the high-iron bauxite can be recycled and utilized through simple high-temperature roasting, Bayer process dissolution and magnetic separation. It can be directly connected with the existing Bayer process. The treatment method has a good iron-aluminum separation effect. The iron grade of the obtained iron concentrate is greater than 55%, and the iron recovery rate is greater than 80%. It can be directly used as an ironmaking material and can reduce the amount of red mud by more than 50%.

[0025] The calculation method of red mud reduction is:

[0026] Wherein α is the reduction rate, ω1 is the amount of red mud produced by the traditional Bayer process (directly mixing bauxite with sodium aluminate solution for high-temperature dissolution) (iron resources cannot be effectively separated and recovered), and ω2 is the amount of red mud produced by the method of the present invention (most of the iron resources can be recovered by magnetic separation, and the amount of red mud here is the amount of red mud remaining after magnetic separation).

[0027] (2) The method of the present invention realizes the comprehensive utilization of high-iron bauxite and biomass, and solves the problem of utilizing iron resources in high-iron bauxite.

[0028] (3) The present invention further adopts calcination treatment heated to 600-700°C under oxygen-free conditions and adopts a two-stage stirring dissolution reaction, which can significantly improve the iron grade and iron recovery rate of the obtained iron concentrate and further improve the degree of red mud reduction. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1The present invention is a process flow chart of a method for extracting iron from high-iron bauxite using biomass as a clean reducing agent. DETAILED DESCRIPTION

[0030] The present invention is further described in detail below in conjunction with embodiments and drawings, but the embodiments of the present invention are not limited thereto.

[0031] Example 1

[0032] A method for extracting iron from high-iron bauxite using biomass as a clean reducing agent, the process flow chart of which is as follows Figure 1 The specific steps are as follows:

[0033] (1) The high-iron bauxite raw material (from Pingguo, Guangxi, with a chemical composition of Al2O3 49.084%, Fe2O3 19.93%, SiO2 8.713%, A / S (aluminum-silicon ratio) 5.633) was crushed, finely ground through a 100-mesh sieve, and then mixed evenly with bamboo powder in a mass ratio of 30:1. The mixed sample was placed in a porcelain boat with a lid, and then the porcelain boat was placed in a tubular furnace, argon gas was passed through and heating began. After the temperature in the furnace was heated to 650°C, it was kept warm for 20 minutes, and naturally cooled to room temperature under nitrogen flow, and then taken out to obtain a roasted material.

[0034] (2) The roasted material and calcium oxide (mass ratio of 100:4) were added to a sodium aluminate solution with a sodium oxide concentration of 230 g / L, an aluminum oxide concentration of 126 g / L, and an αK (caustic ratio) of 3, with a solid-liquid ratio of 1:4 to prepare a slurry. The slurry was then added to a 500 mL high-pressure reactor for a two-stage dissolution reaction. The first stage was reacted at 100°C for 2 hours, and the second stage was reacted at 260°C for 1 hour. The stirring speed during the process was constant at 300 rpm. After the reaction was completed, the sample was naturally cooled to room temperature, and then filtered for solid-liquid separation to obtain solid slag and dissolution liquid. During the filtration process, the solid was washed with hot water for 3 times, and the solid was dried at 70°C for 12 hours, then taken out and ground to obtain an iron-rich residue. The dissolution liquid was decomposed by seed fractionation to obtain aluminum hydroxide and circulating mother liquor, which were recycled after being formulated.

[0035] (3) The iron-rich residue was magnetically separated using a magnetic separator with a magnetic field strength of 220 mT to obtain an iron concentrate. The iron grade of the obtained iron concentrate was 61.36%, and the iron recovery rate was 81.32%. The magnetic separation tailings were a silicon-rich red mud phase, and the red mud reduction degree reached 57.68% (compared with the amount of red mud produced in Comparative Example 1).

[0036] Example 2

[0037] A method for extracting iron from high-iron bauxite using biomass as a clean reducing agent, the process flow chart of which is as follows Figure 1The specific steps are as follows:

[0038] (1) The high-iron bauxite raw material (from Pingguo, Guangxi, chemical composition: Al2O3 49.084%, Fe2O3 19.93%, SiO2 8.713%, A / S (aluminum-silicon ratio) 5.633) was crushed, finely ground and passed through a 100-mesh sieve, and then mixed evenly with straw (dried and crushed and passed through a 100-mesh sieve) in a mass ratio of 20:1. The mixed sample was placed in a porcelain boat with a lid, and then the porcelain boat was placed in a tubular furnace, argon was passed through and heating began. After the temperature in the furnace was heated to 700°C, it was kept warm for 10 minutes, and naturally cooled to room temperature under nitrogen flow, and then taken out to obtain a roasted material.

[0039] (2) The calcined material and calcium oxide (mass ratio of 100:8) were added to a sodium aluminate solution with a sodium oxide concentration of 250 g / L, an aluminum oxide concentration of 102 g / L, and an αK (caustic ratio) of 4, with a solid-liquid ratio of 1:4 to prepare a slurry. The slurry was then added to a 500 mL high-pressure reactor for a two-stage dissolution reaction. The first stage was reacted at 100°C for 2 hours, and the second stage was reacted at 260°C for 1 hour. The stirring speed during the process was constant at 400 rpm. After the reaction was completed, the sample was naturally cooled to room temperature, and then filtered for solid-liquid separation to obtain solid slag and dissolution liquid. During the filtration process, the solid was washed with hot water for 3 times, and the solid was dried at 70°C for 12 hours, then taken out and ground to obtain an iron-rich residue. The dissolution liquid was decomposed by seed fractionation to obtain aluminum hydroxide and circulating mother liquor, which were recycled after being formulated.

[0040] (3) The iron-rich residue was magnetically separated using a magnetic separator with a magnetic field strength of 175 mT to obtain an iron concentrate. The iron grade of the obtained iron concentrate was 57.01%, and the iron recovery rate was 84.76%. The magnetically separated tailings were a silicon-rich red mud phase, and the red mud reduction was 54.65% (compared with the amount of red mud produced in Comparative Example 1).

[0041] Example 3

[0042] A method for extracting iron from high-iron bauxite using biomass as a clean reducing agent, the process flow chart of which is as follows Figure 1 The specific steps are as follows:

[0043] (1) The high-iron bauxite raw material (from Pingguo, Guangxi, with a chemical composition of Al2O3 49.084%, Fe2O3 19.93%, SiO2 8.713%, A / S (aluminum-silicon ratio) 5.633) was crushed, finely ground and passed through a 100-mesh sieve, and then mixed with corn cobs (dried, crushed and passed through a 100-mesh sieve) in a mass ratio of 10:1. The mixed sample was placed in a porcelain boat with a lid, and then the porcelain boat was placed in a tubular furnace, argon was passed through and heating began. After the temperature in the furnace was heated to 600°C, it was kept warm for 30 minutes, and naturally cooled to room temperature under nitrogen flow, and then taken out to obtain a roasted material.

[0044] (2) The roasted material and calcium oxide (mass ratio of 100:6) were added to a sodium aluminate solution with a sodium oxide concentration of 230 g / L, an aluminum oxide concentration of 126 g / L, and an αK (caustic ratio) of 3, with a solid-liquid ratio of 1:5 to prepare a slurry. The slurry was then added to a 500 mL high-pressure reactor for a two-stage dissolution reaction. The first stage was reacted at 90°C for 3 hours, and the second stage was reacted at 250°C for 1.5 hours. The stirring speed was constant at 500 rpm during the process. After the reaction, the sample was naturally cooled to room temperature, and then filtered to separate the solid and liquid to obtain solid slag and dissolution liquid. During the filtration process, the solid was washed with hot water for 3 times, and the solid was dried at 70°C for 12 hours, then taken out and ground to obtain an iron-rich residue. The dissolution liquid was decomposed by seed fractionation to obtain aluminum hydroxide and circulating mother liquor, which were recycled after being formulated.

[0045] (3) The iron-rich residue was magnetically separated using a magnetic separator with a magnetic field strength of 275 mT to obtain an iron concentrate. The iron grade of the obtained iron concentrate was 55.82%, and the iron recovery rate was 81.61%. The magnetic separation tailings were a silicon-rich red mud phase, and the red mud reduction was 50.12% (compared with the amount of red mud produced in Comparative Example 1).

[0046] Example 4

[0047] A method for extracting iron from high-iron bauxite using biomass as a clean reducing agent, the process flow chart of which is as follows Figure 1 The specific steps are as follows:

[0048] (1) The high-iron bauxite raw material (from Pingguo, Guangxi, chemical composition: Al2O3 49.084%, Fe2O3 19.93%, SiO2 8.713%, A / S (aluminum-silicon ratio) 5.633) was crushed, finely ground through a 100-mesh sieve, and then mixed evenly with bamboo powder in a mass ratio of 40:1. The mixed sample was placed in a porcelain boat with a lid, and then the porcelain boat was placed in a tubular furnace, argon gas was passed and heating began. After the temperature in the furnace was heated to 680°C, it was kept warm for 15 minutes, and naturally cooled to room temperature under nitrogen flow, and then taken out to obtain a roasted material.

[0049] (2) The roasted material and calcium oxide (mass ratio of 100:8) were added to a sodium aluminate solution with a sodium oxide concentration of 200 g / L, an aluminum oxide concentration of 130 g / L, and an αK (caustic ratio) of 2.5, with a solid-liquid ratio of 1:5 to prepare a slurry. The slurry was then added to a 500 mL high-pressure reactor for a two-stage dissolution reaction. The first stage was reacted at 110°C for 1 hour, and the second stage was reacted at 270°C for 1 hour. The stirring speed during the process was constant at 400 rpm. After the reaction was completed, the sample was naturally cooled to room temperature, and then solid-liquid separation was performed by suction filtration to obtain solid slag and dissolution liquid. During the suction filtration process, the solid was washed with hot water for 3 times, and the solid was dried at 70°C for 12 hours, then taken out and ground to obtain iron-rich residue. The dissolution liquid was decomposed by seed fractionation to obtain aluminum hydroxide and circulating mother liquor, which were recycled after being formulated.

[0050] (3) The iron-rich residue was magnetically separated by a magnetic separator with a magnetic field strength of 250 mT to obtain an iron concentrate. The iron grade of the obtained iron concentrate was 55.31%, and the iron recovery rate was 80.47%. The magnetic separation tailings were a silicon-rich red mud phase, and the red mud reduction was 51.62% (compared with the amount of red mud produced in Comparative Example 1).

[0051] Comparative Example 1

[0052] A method for extracting iron from high-iron bauxite, the specific steps are as follows:

[0053] The high-iron bauxite raw material (from Pingguo, Guangxi, with chemical composition: Al2O349.084%, Fe2O319.93%, SiO28.713%, A / S (aluminum-silicon ratio) of 5.633) was crushed and finely ground through a 100-mesh sieve, and then directly added together with calcium oxide (mass ratio of 100:8) into a sodium aluminate solution with a sodium oxide concentration of 230 g / L, an aluminum oxide concentration of 126 g / L, and an αK (caustic ratio) of 3, with a solid-liquid ratio of 1:4 to prepare a slurry. The slurry was then added to a 500mL high-pressure reactor for a two-stage dissolution reaction. The first stage was reacted at 100°C for 2 hours, and the second stage was reacted at 260°C for 1 hour. During the process, the stirring speed was constant at 300rpm. After the reaction, the sample was naturally cooled to room temperature, and then vacuum filtration was used for solid-liquid separation to obtain solid residue and dissolution liquid. During the vacuum filtration process, the solid was washed three times with hot water, and the solid was dried at 70°C for 12 hours, then taken out and ground to obtain red mud.

[0054] The iron grade of the red mud obtained in this comparative example is 33%, and the iron is not reduced and cannot be separated by magnetic separation to obtain iron concentrate.

[0055] Comparative Example 2

[0056] A method for extracting iron from high-iron bauxite, using a hydrothermal dissolution reaction as in the prior art CN 105238924 A, with the following specific steps:

[0057] (1) The high-iron bauxite raw material (from Pingguo, Guangxi, chemical composition: Al2O3 49.084%, Fe2O3 19.93%, SiO2 8.713%, A / S (aluminum-silicon ratio) 5.633) was crushed, finely ground through a 100-mesh sieve, and then mixed with bamboo powder in a mass ratio of 30:1. The mixed sample was added into a sodium aluminate solution with a sodium oxide concentration of 230 g / L, an aluminum oxide concentration of 126 g / L, and an αK (caustic ratio) of 3, with a solid-liquid ratio of 1:4 to prepare a slurry. The slurry was then added to a 500 mL autoclave for a one-step dissolution reaction, and the reaction was carried out at 260°C for 3 hours. During the process, the stirring speed was kept constant at 300 rpm. After the reaction, the sample was naturally cooled to room temperature, and then filtered to separate the solid and liquid to obtain solid slag and dissolution. During the filtration process, the solid was washed with hot water for 3 times, and the solid was dried at 70°C for 12 hours, then taken out and ground to obtain iron-rich residue. The dissolution was decomposed by seed fractionation to obtain aluminum hydroxide and circulating mother liquor, which was recycled after being formulated.

[0058] (2) The iron-rich residue was magnetically separated using a magnetic separator with a magnetic field strength of 220 mT to obtain an iron concentrate. The iron grade of the obtained iron concentrate was 41.61%, and the iron recovery rate was 50.23%. The magnetically separated tailings were a silicon-rich red mud phase, and the red mud reduction degree was 40.85%.

[0059] It can be seen from the comparison results of this comparative example and Example 1 that the present invention can significantly improve the iron grade and iron recovery rate of the obtained iron concentrate by adopting high-temperature roasting treatment under anaerobic conditions and adopting a two-stage stirring dissolution reaction, and can further improve the degree of red mud reduction.

[0060] Comparative Example 3

[0061] A method for extracting iron from high-iron bauxite, using a one-step dissolution reaction instead of a two-stage dissolution reaction, the specific steps are as follows:

[0062] (1) The high-iron bauxite raw material (from Pingguo, Guangxi, with a chemical composition of Al2O3 49.084%, Fe2O3 19.93%, SiO2 8.713%, A / S (aluminum-silicon ratio) 5.633) was crushed, finely ground through a 100-mesh sieve, and then mixed evenly with bamboo powder in a mass ratio of 30:1. The mixed sample was placed in a porcelain boat with a lid, and then the porcelain boat was placed in a tubular furnace, argon gas was passed through and heating began. After the temperature in the furnace was heated to 650°C, it was kept warm for 20 minutes, and naturally cooled to room temperature under nitrogen flow, and then taken out to obtain a roasted material.

[0063] (2) The roasted material and calcium oxide (mass ratio of 100:4) were added to a sodium aluminate solution with a sodium oxide concentration of 230 g / L, an aluminum oxide concentration of 126 g / L, and an αK (caustic ratio) of 3, with a solid-liquid ratio of 1:4 to prepare a slurry. The slurry was then added to a 500 mL high-pressure reactor for a one-step dissolution reaction, and the reaction was carried out at 260°C for 3 hours. During the process, the stirring speed was kept constant at 300 rpm. After the reaction, the sample was naturally cooled to room temperature, and then solid-liquid separation was performed by suction filtration to obtain solid slag and dissolution liquid. During the suction filtration process, the solid was washed with hot water for 3 times, and the solid was dried at 70°C for 12 hours, then taken out and ground to obtain an iron-rich residue. The dissolution liquid was decomposed by seed fractionation to obtain aluminum hydroxide and a circulating mother liquor, which was recycled after being formulated.

[0064] (3) The iron-rich residue was magnetically separated using a magnetic separator with a magnetic field strength of 220 mT to obtain an iron concentrate. The iron grade of the obtained iron concentrate was 52.18%, and the iron recovery rate was 64.79%. The magnetically separated tailings were a silicon-rich red mud phase, and the red mud reduction degree was 48.72%.

[0065] It can be seen from the comparison results of this comparative example and Example 1 that the present invention adopts a two-stage stirring dissolution reaction, first stirring the reaction at a low temperature (90-110° C.), which can better promote the reaction between calcium oxide and bauxite and strengthen the conversion of iron minerals, thereby improving the iron-aluminum separation efficiency. At the same time, it can reduce energy consumption.

[0066] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principles of the present invention shall be equivalent replacement methods and shall be included in the protection scope of the present invention.

Claims

1. A method for extracting iron from high-iron bauxite using biomass as a clean reducing agent, characterized in that: The steps include: (1) mixing high-iron bauxite and biomass uniformly, heating to 600-700° C. under oxygen-free conditions, and roasting to obtain a roasted material; (2) dissolving the calcined material obtained in step (1) by using the Bayer process to obtain solid slag and dissolving liquid; (3) subjecting the solid slag obtained in step (2) to magnetic separation to obtain iron ore concentrate.

2. The method for extracting iron from high-iron bauxite using biomass as a clean reducing agent according to claim 1, characterized in that: The biomass in step (1) includes bamboo powder, straw, and corn cobs.

3. The method for extracting iron from high-iron bauxite using biomass as a clean reducing agent according to claim 2, characterized in that: The mass ratio of the high-iron bauxite and the biomass mixed in step (1) is 10 to 40:

1.

4. The method for extracting iron from high-iron bauxite using biomass as a clean reducing agent according to claim 1, characterized in that: The oxygen-free condition in step (1) refers to an inert atmosphere of nitrogen or argon; the calcination treatment time is 10 to 30 minutes.

5. The method for extracting iron from high-iron bauxite using biomass as a clean reducing agent according to claim 1, characterized in that: The method for dissolution using the Bayer process described in step (2) is as follows: The calcined material and calcium oxide are added into a sodium aluminate solution with a sodium oxide concentration of 200-250 g / L, an aluminum oxide concentration of 100-150 g / L and an αK of 2.5-4 to prepare a slurry; the slurry is then subjected to a two-stage stirring dissolution reaction, wherein the first stage is stirred at 90-110°C for 1-3 hours, and the second stage is stirred at 250-270°C for 1-1.5 hours. After the reaction is completed, the mixture is naturally cooled to room temperature, and the solid-liquid is separated to obtain solid slag and dissolution liquid.

6. The method for extracting iron from high-iron bauxite using biomass as a clean reducing agent according to claim 5, characterized in that: The mass ratio of the calcined material to calcium oxide is 100:4-8; the solid-liquid mass ratio of the calcined material and calcium oxide added to the sodium aluminate solution is 1:4-5; and the stirring speed of the two-stage stirring dissolution reaction is 300-500rpm.

7. The method for extracting iron from high-iron bauxite using biomass as a clean reducing agent according to claim 5, characterized in that: The solid-liquid separation is carried out by suction filtration, and the obtained solid residue is further washed with hot water, dried and crushed.

8. The method for extracting iron from high-iron bauxite using biomass as a clean reducing agent according to claim 5, characterized in that: The dissolving liquid in step (2) is decomposed into aluminum hydroxide and circulating mother liquor, and the circulating mother liquor is recycled after being prepared.

9. The method for extracting iron from high-iron bauxite using biomass as a clean reducing agent according to claim 1, characterized in that: The magnetic separation in step (3) is carried out using a magnetic separator with a magnetic field strength of 175 to 275 mT.

10. The method for extracting iron from high-iron bauxite using biomass as a clean reducing agent according to claim 1, characterized in that: The iron grade of the iron concentrate obtained in step (3) is greater than 55%, and the iron recovery rate is greater than 80%.

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