Method for reducing combined treatment of gibbsite-type high-iron high-organic aluminum ore

Abstract

The present application relates to the technical field of comprehensive utilization of metallurgical resources, in particular to a method for reducing combined treatment of gibbsite-type high-iron high-organic bauxite, which comprises the following steps: sending the crushed and refined bauxite into a low-temperature microwave heating device, and performing microwave heating treatment under a reducing atmosphere to simultaneously complete dehydration and activation of gibbsite, removal of organic matter, and selective reduction of iron oxides; obtaining magnetic iron concentrate and high-aluminum non-magnetic product through dry low-intensity magnetic separation of the product; and performing low-temperature Bayer process leaching of the non-magnetic product after pre-desiliconization. The relative leaching rate of alumina is not less than 91.5%, the amount of red mud produced is only 65% of that of the traditional Bayer process, the overall beneficiation and smelting cost is reduced by about 30% compared with the traditional method, and efficient separation and clean recovery of iron and aluminum resources in high-iron high-organic bauxite are realized.

Description

Technical Field

[0001] This invention relates to the field of comprehensive utilization technology of metallurgical resources, specifically a method for the reduction and combined treatment of trihydrate gibbsite-type high-iron and high-organic-content bauxite. Background Technology

[0002] Iron and aluminum are core raw materials supporting my country's national economic development, and both the iron and steel industry and the alumina industry are important pillar industries of the national economy. Due to limitations in domestic resource endowment, my country faces a significant supply gap in iron ore and bauxite, and the industry's dependence on imported raw materials continues to rise. According to official statistics in 2024, my country's annual pig iron production reached 851.737 million tons, and cumulative iron ore imports reached 1.237 billion tons, with a raw material dependence exceeding 80%. In the same year, electrolytic aluminum production reached 43.46 million tons, and cumulative bauxite imports reached 131 million tons, with a raw material dependence approaching 70%. Imported gibbsite-type bauxite is the main type, which typically contains ≥15% Fe2O3 and ≥35% Al2O3, possessing significant comprehensive recovery value. However, it also contains a high proportion of organic carbon (humic acid, lignin, etc.), the presence of which seriously hinders subsequent alumina production.

[0003] Currently, the comprehensive utilization processes for high-iron bauxite can be mainly categorized into three types: "selection before treatment," "aluminum-first, iron-later," and "iron-first, aluminum-later." Among these, the "iron-first, aluminum-later" method has attracted attention due to its higher iron and aluminum recovery rates. For example, Chinese invention patent CN108998610A discloses a method for the comprehensive recovery and utilization of valuable components in high-iron bauxite. This method employs microwave heating and tunnel kiln smelting to reduce iron oxides to sponge iron at 1000-1200℃, followed by magnetic separation to obtain metallic sponge iron and high-alumina tailings. This method has achieved certain results in the treatment of monohydrate gibbsite-type or mixed-type high-iron bauxite. However, when processing gibbsite-type bauxite with high iron and high organic content, the crystal structure of gibbsite differs fundamentally from that of diaspore (AlOOH). Gibbsite begins to dehydrate and transform into active alumina (γ-Al₂O₃ or amorphous form) at 150-300℃ under normal pressure. If heated further to above 800℃, the active alumina irreversibly transforms into inert corundum (α-Al₂O₃). The processing temperature of 1000-1200℃ set in the existing technology (CN108998610A) completely destroys the chemical activity of aluminum minerals in gibbsite-type ore, preventing the aluminum in the high-alumina tailings after magnetic separation from being dissolved by the Bayer process. This results in secondary solidification and waste of aluminum resources. Furthermore, the existing technology does not differentiate between different types of bauxite, and its process window is only applicable to diaspore-type ore.

[0004] In addition, the high-temperature treatment of 1000-1200℃ required by existing technologies not only consumes enormous amounts of energy but also significantly increases equipment investment and maintenance costs. However, such high temperatures are unnecessary for gibbsite-type ores—iron reduction can be achieved at lower temperatures (800-950℃ or even lower) in a reducing atmosphere, while the dehydration and activation of gibbsite only requires 300-600℃. Therefore, differentiated low-temperature process routes need to be developed for gibbsite-type ores. Finally, gibbsite-type bauxite (especially imported ores) generally contains a considerable proportion of organic carbon. These organic compounds cause a series of problems in the traditional Bayer process: increased alkali consumption (organic compounds react with caustic alkali to produce sodium oxalate, etc.), reduced aluminum dissolution rate, deterioration of red mud settling performance, and impact on the quality of the alumina product. Existing technologies do not provide any means to remove or treat organic compounds. Applying existing technology directly to gibbsite-type ores with high organic content will cause the organic matter to undergo complex cracking reactions at high temperatures. Some of the organic matter will generate non-volatile carbon deposits that remain in the tailings. When these deposits are subsequently introduced into the Bayer process system, they will cause a surge in alkali consumption and difficulties in production and operation.

[0005] In summary, existing high-iron bauxite processing technologies are mainly designed for monohydrate gibbsite-type ore, and have not been specifically developed for the phase characteristics, high organic matter content, and low-temperature activation potential of trihydrate gibbsite-type, high-iron, and high-organic-content bauxite. Therefore, we propose a reduction-combined treatment method for trihydrate gibbsite-type high-iron, high-organic-content bauxite to solve the above problems. Summary of the Invention

[0006] The purpose of this invention is to provide a method for the combined reduction and treatment of trihydrate gibbsite-type high-iron, high-organic-content bauxite, in order to solve the problem mentioned in the background art that the existing high-iron bauxite processing technology is mainly designed around monohydrate gibbsite-type ore and has not been specifically developed for the phase characteristics, high organic matter content and low-temperature activation potential of trihydrate gibbsite-type, high-iron, high-organic-content bauxite.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a method for the reduction and combined treatment of trihydrate gibbsite-type high-iron and high-organic-content bauxite, comprising the following steps:

[0008] S1: Add trihydrate gibbsite-type high-iron, high-organic-content bauxite to a mill for crushing and refining to obtain mineral powder;

[0009] S2: The mineral powder obtained in step S1 is fed into a low-temperature microwave heating device, and a reducing gas is introduced into the heating device at the same time. Microwave heating treatment is carried out under a reducing atmosphere to obtain an activation-reduction product.

[0010] S3: The activation-reduction product obtained in step S2 is sent to a dry weak magnetic separator for magnetic separation to obtain magnetic and non-magnetic products.

[0011] S4: After pre-desiliconization treatment, the non-magnetic product obtained in step S3 is sent to the low-temperature Bayer process system for alumina leaching.

[0012] S5: In step S4, the amount of red mud produced by the low-temperature Bayer process is 65% lower than that of the traditional Bayer process, and the Al2O3 residue in the red mud is less than 5% to 15%. The red mud is used as a building material raw material or for the recovery of valuable components.

[0013] S6: The magnetic product obtained in step S3 is used as a raw material for ironmaking in steel plants.

[0014] Preferably, in step S1, the trihydrate gibbsite-type high-iron, high-organic bauxite contains ≥15% Fe2O3, ≥35% Al2O3, and ≥0.1% organic carbon.

[0015] Preferably, in step S1, the particle size range of the crushed and refined mineral powder is 0.5 to 3 mm.

[0016] Preferably, in step S2, the reducing gas is selected from at least one of H2 and CO.

[0017] Preferably, in step S2, the reducing gas and the inert gas are mixed and introduced, and the volume fraction of the reducing gas is 10% to 30%; the inert gas includes at least one of nitrogen and argon.

[0018] Preferably, in step S2, the low-temperature microwave heating device is provided with an exhaust port for discharging water vapor and gaseous products generated during the heating process.

[0019] Preferably, in step S2, the low-temperature microwave heating device is provided with an exhaust port for discharging water vapor and gaseous products generated during the heating process.

[0020] Preferably, in step S2, the gibbsite is dehydrated of its water of crystallization and natural water and converted into active alumina by the low-temperature microwave heating. Organic matter in the ore is carbonized or gasified and removed, and iron oxides in the ore are selectively reduced to weakly magnetic Fe3O4.

[0021] Preferably, in step S3, the magnetic induction intensity of the dry weak magnetic separator is set to 0.3 to 0.8 T.

[0022] Preferably, in step S3, the magnetic product is an iron concentrate containing Fe3O4 with an iron grade of 55% to 60%; the non-magnetic product has an Al2O3 recovery rate of ≥90% and an organic carbon residue of ≤0.1%.

[0023] Preferably, in step S4, the conditions for the low-temperature Bayer leaching process are: leaching temperature 130–150°C, leaching time 30–60 minutes, and caustic alkali concentration 140–180 g / L.

[0024] Compared with the prior art, the beneficial effects of the present invention are:

[0025] This invention provides a low-temperature microwave integrated recycling method for gibbsite-type bauxite with high iron and high organic content. The process has low temperature, low energy consumption, thorough removal of organic matter, high alumina grade, and is compatible with the low-temperature Bayer process, achieving efficient, clean, and economical recycling of this type of difficult-to-process resource. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. 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.

[0027] Figure 1 This is a schematic flowchart of a method for the reduction and combined treatment of trihydrate gibbsite-type high-iron and high-organic bauxite, provided in an embodiment of this application. Detailed Implementation

[0028] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] Please see Figure 1 The present application will be further illustrated below with reference to specific embodiments. Experimental methods in the following embodiments that do not specify specific conditions are generally determined according to national / industry standards; if there is no corresponding national / industry standard, they are performed according to general international standards, conventional conditions, or conditions recommended by the manufacturer.

[0030] Example 1: The present invention provides a method for the reduction and combined treatment of gibbsite-type high-iron and high-organic-content bauxite, comprising the following steps:

[0031] S1 Raw material crushing and mixing: The trihydrate gibbsite-type high-iron and high-organic bauxite is added to the mill for crushing and refining to obtain mineral powder;

[0032] S2 Low-temperature microwave heating: The mineral powder obtained in step S1 is fed into a low-temperature microwave heating device, and a reducing gas is introduced into the heating device at the same time. Microwave heating treatment is carried out under a reducing atmosphere to obtain an activated-reduced product.

[0033] S3 Dry weak magnetic separation: The activation-reduction product obtained in step S2 is fed into a dry weak magnetic separator for magnetic separation to obtain magnetic and non-magnetic products.

[0034] S4 High-alumina tailings treatment: After pre-desiliconization treatment of the non-magnetic product obtained in step S3, it is sent to the low-temperature Bayer process system for alumina leaching.

[0035] S5 Red Mud Recovery: In step S4, the amount of red mud produced by the low-temperature Bayer process is 65% lower than that of the traditional Bayer process, and the Al2O3 residue in the red mud is less than 5% to 15%. The red mud can be used as a building material raw material or for the recovery of valuable components.

[0036] S6 Iron Ore Recovery: The magnetic product obtained in step S3 is used as a raw material for ironmaking in steel plants;

[0037] Furthermore, in step S1, the Fe2O3 content in the trihydrate gibbsite-type high-iron, high-organic bauxite is ≥15%, the Al2O3 content is ≥35%, and the organic carbon content is ≥0.1%.

[0038] Furthermore, in step S1, the particle size range of the crushed and refined mineral powder is 0.5–3 mm.

[0039] Furthermore, in step S2, the reducing gas is selected from at least one of H2 and CO.

[0040] Furthermore, in step S2, a reducing gas and an inert gas are mixed and introduced, with the volume fraction of the reducing gas being 10% to 30%; the inert gas includes at least one of nitrogen and argon.

[0041] Furthermore, in step S2, the microwave heating and heat preservation temperature range is 300-600℃, and the heat preservation time ranges from 0.1 to 3 hours.

[0042] Furthermore, in step S2, the low-temperature microwave heating device is equipped with an exhaust port for discharging water vapor and gaseous products generated during the heating process.

[0043] Furthermore, in step S2, by low-temperature microwave heating, gibbsite loses its water of crystallization and natural water and is converted into active alumina. Organic matter in the ore is carbonized or gasified and removed, and iron oxides in the ore are selectively reduced to weakly magnetic Fe3O4.

[0044] Furthermore, in step S3, the magnetic induction intensity of the dry weak magnetic separator is set to 0.3 to 0.8 T.

[0045] Furthermore, in step S3, the magnetic product is an iron concentrate containing Fe3O4 with an iron grade of 55%–60%; the non-magnetic product has an Al2O3 recovery rate of ≥90% and an organic carbon residue of ≤0.1%.

[0046] Furthermore, in step S4, the conditions for low-temperature Bayer leaching are: leaching temperature 130–150°C, leaching time 30–60 minutes, and caustic alkali concentration 140–180 g / L.

[0047] The chemical composition of the imported trihydrate gibbsite-type high-iron, high-organic bauxite used is shown in Table 1.

[0048] Table 1 Chemical composition of a certain imported trihydrate-type high-iron, high-organic bauxite

[0049] Element <![CDATA[Na2O]]> <![CDATA[Al2O3]]> <![CDATA[SiO2]]> <![CDATA[TiO2]]> CaO <![CDATA[Fe2O3]]> content(%) 0.029 41.19 3.3 2.95 - 31.33

[0050] Working principle:

[0051] (1) The bauxite was added to a mill for crushing and refining. The particle size of the refined mineral powder ranged from 0.5 to 3 mm.

[0052] (2) The refined powder from step (1) is fed into a low-temperature microwave heating device, and a reducing gas is introduced into the heating device at the same time. The reducing gas is a mixture of H2 and N2, with H2 volume fraction of 20%. After heating to 500℃, it is kept at that temperature for 0.5 hours. During the heating process, the free water and bound water in the product are vaporized, and the overall weight loss of the raw ore is 10%. The heating device is kept under a slight positive pressure and the atmosphere is uniform.

[0053] (3) The product after low-temperature microwave heating in step (2) is directly fed into a dry weak magnetic separator. The magnetic induction intensity of the separator is set to 0.5T. Two products are obtained after magnetic separation: magnetic product: mainly weakly magnetic Fe3O4 with an iron content of about 55% to 60%, which can be used as raw material for ironmaking in steel plants or for further enrichment; non-magnetic product (high-alumina tailings): Al2O3 content of about 50% to 65%, and organic carbon residue reduced to 0.03%;

[0054] (4) The non-magnetic tailings obtained in step (3) are pre-desiliconized to remove some of the active SiO2, thereby increasing the aluminum-silicon ratio (A / S) to more than 12.

[0055] (5) The tailings obtained in step (4) after pre-desiliconization were fed into a low-temperature Bayer process system for alumina leaching. The leaching temperature was 180°C, the leaching time was 1.5 hours, and the caustic alkali concentration was 150 g / L. Under these conditions, the relative leaching rate of alumina reached 91.5%.

[0056] (6) The amount of red mud produced by the low-temperature Bayer process in step (5) is less than 65% of that produced by the conventional Bayer process, and the residual Al2O3 in the red mud is 12.6%. This small amount of red mud can be used as a corrective raw material for cement production, or the residual valuable components such as scandium and titanium can be further recovered.

[0057] (7) The weak magnetic iron oxide (Fe3O4) product obtained by dry weak magnetic separation in step (3) has an iron grade of 58.6% and a sulfur content of less than 0.1%. It can be directly used as raw material for steel plant ore blending or pellet production, realizing efficient recovery of iron resources.

[0058] (8) In comparison, the overall beneficiation cost of this process can be reduced by about 30% compared with the traditional wet process route for each ton of raw ore processed. The economic advantage comes from the high-value recovery of by-product magnetite and the energy consumption and red mud reduction of the low-temperature Bayer process system. The cost savings in transportation are more of a partial offset to the energy consumption of the microwave dehydration process. The overall benefits will be more prominent in the low-cost energy scenario. The above is the complete working principle of this invention.

[0059] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

Claims

1. A method for the reduction and combined treatment of trihydrate gibbsite-type high-iron, high-organic-content bauxite, characterized in that: Includes the following steps: S1: Add trihydrate gibbsite-type high-iron, high-organic-content bauxite to a mill for crushing and refining to obtain mineral powder; S2: The mineral powder obtained in step S1 is fed into a low-temperature microwave heating device, and a reducing gas is introduced into the heating device at the same time. Microwave heating treatment is carried out under a reducing atmosphere to obtain an activation-reduction product. S3: The activation-reduction product obtained in step S2 is sent to a dry weak magnetic separator for magnetic separation to obtain magnetic and non-magnetic products. S4: After pre-desiliconization treatment, the non-magnetic product obtained in step S3 is sent to the low-temperature Bayer process system for alumina leaching. S5: In step S4, the amount of red mud produced by the low-temperature Bayer process is 65% lower than that of the traditional Bayer process, and the Al2O3 residue in the red mud is less than 5% to 15%. The red mud is used as a building material raw material or for the recovery of valuable components. S6: The magnetic product obtained in step S3 is used as a raw material for ironmaking in steel plants.

2. The method for combined reduction and treatment of trihydrate gibbsite-type high-iron, high-organic-content bauxite according to claim 1, characterized in that: In step S1, the trihydrate gibbsite-type high-iron, high-organic bauxite contains ≥15% Fe2O3, ≥35% Al2O3, and ≥0.1% organic carbon.

3. The method for combined reduction and treatment of trihydrate gibbsite-type high-iron, high-organic-content bauxite according to claim 1, characterized in that: In step S1, the particle size range of the crushed and refined mineral powder is 0.5 to 3 mm.

4. The method for combined reduction and treatment of trihydrate gibbsite-type high-iron, high-organic-content bauxite according to claim 1, characterized in that: In step S2, the reducing gas is selected from at least one of H2 and CO.

5. The method for combined reduction and treatment of trihydrate gibbsite-type high-iron, high-organic-content bauxite according to claim 1, characterized in that: In step S2, the reducing gas and the inert gas are mixed and introduced, with the volume fraction of the reducing gas being 10% to 30%; the inert gas includes at least one of nitrogen and argon.

6. The method for combined reduction and treatment of trihydrate gibbsite-type high-iron, high-organic-content bauxite according to claim 1, characterized in that: In step S2, the microwave heating and heat preservation temperature range is 300-600℃, and the heat preservation time ranges from 0.1 to 3 hours.

7. The method for combined reduction and treatment of trihydrate gibbsite-type high-iron, high-organic-content bauxite according to claim 1, characterized in that: In step S2, the low-temperature microwave heating device is provided with an exhaust port for discharging water vapor and gaseous products generated during the heating process.

8. The method for combined reduction and treatment of trihydrate gibbsite-type high-iron, high-organic-content bauxite according to claim 1, characterized in that: In step S2, the gibbsite is dehydrated of its water of crystallization and natural water and converted into active alumina by the low-temperature microwave heating. Organic matter in the ore is carbonized or gasified and removed. Iron oxides in the ore are selectively reduced to Fe3O4 with weak magnetic properties.

9. The method for combined reduction and treatment of trihydrate gibbsite-type high-iron, high-organic-content bauxite according to claim 1, characterized in that: In step S3, the magnetic induction intensity of the dry weak magnetic separator is set to 0.3 to 0.8 T.

10. The method for combined reduction and treatment of trihydrate gibbsite-type high-iron, high-organic-content bauxite according to claim 1, characterized in that: In step S3, the magnetic product is an iron concentrate containing Fe3O4 with an iron grade of 55% to 60%; the non-magnetic product has an Al2O3 recovery rate of ≥90% and an organic carbon residue of ≤0.1%.

11. The method for combined reduction and treatment of trihydrate gibbsite-type high-iron, high-organic-content bauxite according to claim 1, characterized in that: In step S4, the conditions for the low-temperature Bayer process dissolution are: dissolution temperature 130-150℃, dissolution time 30-60 minutes, and caustic alkali concentration 140-180 g / L.

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