Method for recycling iron, aluminum and sodium in high-iron and high-silicon red mud through gradient sintering

Abstract

A method for recycling iron, aluminum and sodium in high-iron and high-silicon red mud through gradient sintering belongs to the technical field of metallurgy and comprises the following steps: respectively crushing and levigating the high-iron and high-silicon red mud and lime, uniformly mixing with industrial sodium carbonate and a fluxing agent to prepare raw material pellets, and preheating and drying through kiln tail gas; the dried pellets are transferred to an oxidation sintering furnace to be sintered at the temperature of 700-900 DEG C, the obtained oxidized pellets enter a reduction sintering furnace to be sintered at the temperature of 800-1000 DEG C, and water quenching cooling is carried out till the temperature is 80 DEG C or below; the cooled sintered pellet mixed alkali liquor is subjected to wet grinding and leaching, and leaching slurry is subjected to liquid-solid separation to obtain a sodium aluminate solution and leaching residues; aluminum and sodium are recycled from the sodium aluminate solution, and iron is recycled after leaching residues are subjected to magnetic separation. According to the method, the industrial sodium carbonate, the lime and the fluxing agent are added, oxidation-reduction gradient sintering is utilized to complete sufficient dissociation of the iron and aluminum minerals in the red mud, high-quality fine iron powder is obtained while aluminum and sodium are sufficiently recycled, and resource utilization and value-added utilization of the red mud are achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of metallurgy, and in particular relates to a method for recovering sodium iron, aluminum and other substances from high-iron and high-silicon red mud by cascade sintering. Background Art

[0002] Red mud is a highly alkaline industrial waste discharged from the Bayer process of extracting alumina from bauxite. It generally has a high content of Fe2O3 and Al2O3 (Fe2O3 content 30% to 50%, Al2O3 content 15% to 25%) and is considered to be a potential secondary resource for iron-aluminum symbiotic metallurgy. The iron in red mud mainly exists in the form of hematite, goethite and aluminum goethite. These iron oxide monomers have a low degree of dissociation and are associated and embedded with other minerals. The particle size of red mud is extremely fine, and it is usually difficult to obtain iron and aluminum concentrates that can be directly used for production through simple physical sorting.

[0003] Patent CN102732715A proposes a method for treating refractory iron resources by modifying them with sodium salts to promote the aggregation, growth, and enrichment of metallic iron grains. This method suppresses the formation of complex iron oxides such as ferroaluminum spinel and fayalite by adding a small amount of sodium salt. However, it does not address the recovery of aluminum resources from red mud. The sodium salts typically accumulate in the iron ore tailings, making their utilization difficult.

[0004] Patent CN120099279A proposes a comprehensive utilization method of alkali magnetization sintering for high-iron, low-silicon red mud. This method adds a reducing agent and sodium hydroxide solution to the high-iron, low-silicon red mud, and synergistically sintering and regulates the iron-aluminum ore phase to magnetite and sodium aluminate to recover metal resources, wherein quartz phase silica does not participate in the reaction. However, the applicability of this method is narrow. It can only process high-iron, low-silicon red mud and is difficult to apply to high-silicon, high-calcium red mud. Since the aluminum and sodium in the hydrated calcium aluminosilicate and hydrated sodium aluminosilicate parts are difficult to recover, the aluminum oxide and sodium oxide recovery rates of this method are low, and a considerable part of the alkali still remains in the iron-selection tailings, which does not solve the pain points faced by red mud treatment. In addition, the manufacturing cost and difficulty of the reduction sintering reactor required for this method are high, which limits the large-scale application of this technology.

[0005] Patent CN113604663A proposes a method for separating iron-aluminum co-existing resources based on low-calcium reduction sintering. The invention achieves directional reconstruction of the iron-aluminum ore phase in the iron-aluminum co-existing resources by adding sodium salts and calcium salts. Alumina is converted into soluble sodium aluminate; silicon dioxide is converted into sodium calcium silicate with strong alkali stability, and the iron and aluminum resources in the red mud are recovered by leaching and magnetic separation distribution. However, this method does not uniformly regulate the iron ore phase in the red mud, and the reduction rates of different iron oxides vary greatly. The separation efficiency of iron and aluminum minerals is affected to a certain extent, resulting in a decrease in the quality of the iron concentrate; the carbon alkali added in this method is easy to generate metallic sodium and volatilize under a strong reducing atmosphere, resulting in an increase in the amount of alkali, thereby affecting the recovery efficiency and economic benefits of valuable elements. In addition, although the method of generating sodium calcium silicate can reduce the reaction temperature, it requires dealkalization of the tailings, which prolongs and complicates the treatment process. Summary of the Invention

[0006] In response to the shortcomings of the existing technology, the present invention proposes a method for recovering iron, aluminum and sodium from high-iron and high-silicon red mud by cascade sintering. The initial dissociation of high-iron and high-silicon red mud minerals is achieved through oxidative sintering, and complex iron oxides such as aluminum goethite and goethite are directionally converted into hematite, and low-melting-point ternary compounds are simultaneously generated, which promotes the efficiency of solid-phase reaction and reduces the alkali consumption of reduction sintering.

[0007] A method for recovering sodium iron, aluminum and iron from high-iron and high-silicon red mud by step sintering, specifically comprising the following steps:

[0008] (1) High iron and high silicon red mud and lime are crushed and ground separately, and then fully mixed with industrial sodium carbonate and flux according to the mass ratio;

[0009] (2) adding water to the mixture to form pellets, and controlling the moisture content of the pellets during the preparation process;

[0010] (3) Preheating and drying the water-containing pellets outside the kiln to remove the adsorbed water, part of the crystallized water and other volatile components in the pellets;

[0011] (4) The preheated pellets are transferred to an oxidation sintering reactor for oxidation sintering, and the temperature gradient and oxygen partial pressure in the reactor are controlled to ensure that the sintering process is in a stable oxidizing environment;

[0012] (5) The pellets obtained by oxidation sintering are sent to a reduction sintering reactor for deep reduction sintering under a reducing atmosphere. After sintering, the pellets are water quenched;

[0013] (6) wet-grinding the reduced sintered product obtained in step (5) in a ball mill to co-leach aluminum oxide and sodium oxide, and obtaining a sodium aluminate solution and a leached residue through rapid separation, and recovering aluminum and sodium from the obtained sodium aluminate solution;

[0014] (7) The leached residue is subjected to wet magnetic separation to obtain high-quality iron concentrate and waste residue, and the iron in the high-iron and high-silicon red mud is recovered.

[0015] in:

[0016] In the step (1), the high-iron and high-silicon red mud is a by-product of alumina extraction by the Bayer process, and contains, by mass percentage, 20% to 50% of Fe2O3, 10% to 30% of Al2O3, 6% to 20% of SiO2, 2% to 8% of TiO2, 1% to 20% of CaO, and 1% to 10% of Na2O.

[0017] In the step (1), the portion of the ground mixed powder with a particle size of ≤0.074 mm accounts for ≥85% of the total mass.

[0018] In the step (1), the amount of industrial sodium carbonate added to the mixture is 10wt.% to 30wt.% of the mass of the high-iron and high-silicon red mud, and the amount of lime added is 10wt.% to 20wt.% of the mass of the high-iron and high-silicon red mud.

[0019] In the step (1), the flux is one or more of sodium borate, calcium borate, sodium fluoride, calcium fluoride, industrial fluorite and magnesia borax.

[0020] In the step (1), the amount of flux added does not exceed 2 wt.% of the mass of the high-iron and high-silicon red mud.

[0021] In the step (2), the pellets are prepared by a pellet press, and the moisture content is 15% to 25%.

[0022] In the step (3), the pellets are preheated at a temperature of 200°C to 400°C.

[0023] In the step (4), the oxidation sintering reactor is a rotary kiln, the oxidation sintering temperature is 700° C. to 900° C., and the time is 0.5 h to 1.5 h; the tail gas generated during the oxidation sintering process is returned to step (3) to provide a heat source for the preheating process.

[0024] In step (4), the main chemical reaction formula in the oxidation sintering stage is:

[0025] FeOOH→Fe2O3+H2O;

[0026] [Al x Fe (1-x) ]OOH+Na2CO3+SiO2→Fe2O3+Na2O·Al2O3·xSiO2+CO2;

[0027] Al2O3+SiO2+Na2CO3→Na2O·Al2O3·xSiO2+CO2;

[0028] Al2O3+Na2CO3→Na2O·Al2O3+CO2;

[0029] Al2O3+Fe2O3+Na2CO3→Na2O·Fe2O3·Al2O3+CO2;

[0030] Fe2O3+SiO2+CaCO3→CaO·Fe2O3·xSiO2+CO2.

[0031] In the step (5), the reduction sintering reactor is a chain grate, a tunnel kiln or a rotary kiln, and the reducing atmosphere is natural gas cracking gas or CO and H2 provided by coal powder pyrolysis, and the amount thereof is 1.0 to 1.2 times the theoretical amount used to reduce hematite to metallic iron.

[0032] In the step (5), the temperature of the deep reduction sintering is 800°C to 1000°C, and the time is 0.5h to 1.5h. After the sintering is completed, the pellets are cooled to below 80°C by water quenching; the tail gas generated during the deep reduction sintering process is returned to step (4) to provide a heat source for the oxidation sintering.

[0033] In step (5), the main chemical reaction formula in the deep reduction sintering stage is:

[0034] Fe2O3+CO→Fe+CO2;

[0035] Fe2O3+H2→Fe+H2O;

[0036] Na2O·Al2O3·xSiO2+CaCO3→Na2O·Al2O3+2CaO·SiO2;

[0037] TiO2+CaCO3→CaO·TiO2+CO2;

[0038] SiO2+CaCO3→2CaO·SiO2+CO2;

[0039] Na2O·Fe2O3·Al2O3+CO→Fe+Na2O·Al2O3+CO2;

[0040] Na2O·Fe2O3·Al2O3+H2→Fe+Na2O·Al2O3+H2O;

[0041] CaO·Fe2O3·xSiO2+CO→Fe+2CaO·SiO2+CO2;

[0042] CaO·Fe2O3·xSiO2+H2→Fe+2CaO·SiO2+H2O.

[0043] In the step (6), wet fine grinding is performed in a ball mill using a dilute alkali solution, wherein the dilute alkali solution is a mixture of a sodium hydroxide solution and a sodium carbonate solution, wherein the concentration of the sodium hydroxide solution is 10 g / L to 50 g / L, the concentration of the sodium carbonate solution is 3 g / L to 10 g / L, and the liquid-solid ratio of the dilute alkali solution to the sintered product is 300 g / L to 500 g / L.

[0044] In the step (6), the ball mill is a grid-type abrasive crusher with a graded liner, which is filled with steel ball grinding media. The rotation speed of the abrasive crusher is 15 rpm to 30 rpm, and the size of the steel ball is Φ20 mm to Φ50 mm. The leaching temperature is 60° C. to 85° C., and the leaching time is 5 min to 30 min.

[0045] In the step (6), a plate and frame filter press is used for rapid separation, and the working pressure is 1.0 MPa to 1.5 MPa.

[0046] In the step (6), the recovery rate of aluminum oxide in the sintered product is ≥90%, and the recovery rate of sodium oxide is ≥96%.

[0047] In the step (7), the magnetic field strength of the magnetic separation is 1000Oe to 3000Oe, the iron grade in the high-quality iron ore concentrate is ≥70%, and the iron recovery rate is ≥90%.

[0048] Compared with the prior art, the present invention has the following beneficial effects:

[0049] (1) In the present invention, by adding lime, industrial sodium carbonate and flux to high-iron and high-silicon red mud and performing step-by-step sintering, the directional regulation of the multi-component complex aluminum-silicon ore phase in the high-iron and high-silicon red mud toward sodium aluminate and dicalcium silicate is achieved, and aluminum and sodium metal resources can be efficiently recovered, wherein the recovery rate of aluminum oxide is ≥90%, and the recovery rate of sodium oxide is ≥96%.

[0050] (2) In the present invention, the complex iron oxides such as aluminum goethite and goethite in high-iron and high-silicon red mud are uniformly converted into hematite through step-by-step sintering, which dissociates the iron-aluminum lattice substitution and multi-element complex embedded structure of the high-iron and high-silicon red mud, effectively improving the reduction efficiency of the iron oxides. The iron grade in the obtained high-quality iron concentrate is ≥70%, and the iron recovery rate is ≥90%.

[0051] (3) In the present invention, the metal oxides in the preheated pellets form low-melting-point ternary compounds under the synergistic effect of oxidative sintering and flux, which promotes the solid-phase reaction between the materials and lowers the required generation temperature, thereby effectively reducing the sintering energy consumption.

[0052] (4) In the present invention, industrial sodium carbonate in the pellets preferentially generates ternary sodium salts such as sodium aluminosilicate under the action of oxidative sintering, which effectively suppresses the high alkali loss problem of reduction sintering.

[0053] (5) In the present invention, the pellets obtained in the oxidation sintering process are directly fed into the reduction furnace, and the waste heat of the tail gas generated is returned to the preheating process for drying the pellets. The waste heat of the tail gas generated by the deep reduction sintering is returned to the oxidation sintering process to provide a heat source, which is beneficial to improving the comprehensive utilization efficiency of energy and realizing the optimization of system energy consumption.

[0054] (6) In the present invention, the reduced sintered product is finely ground by wet method and synergistically leached, and then rapidly separated to inhibit the secondary reaction of the leached slurry and reduce the secondary loss of aluminum and sodium.

[0055] (7) The method of the present invention is used to recycle sodium oxide, aluminum oxide and high-quality iron ore concentrate, realizing the full-scale and value-added utilization of high-iron and high-silicon red mud. The main component of the waste slag is dicalcium silicate, which has good gelling activity and is a low-carbon and environmentally friendly building material raw material. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] Figure 1 A process flow chart of the present invention for recovering sodium iron, aluminum and iron from high-iron and high-silicon red mud by step sintering. DETAILED DESCRIPTION

[0057] The present invention will be further described below by way of specific examples. It should be understood that these examples are only intended to illustrate the present invention and are not intended to limit the scope of application of the present invention.

[0058] The high-iron and high-silicon red mud in the embodiment of the present invention is a by-product of alumina extraction by the Bayer process.

[0059] In the embodiment of the present invention, the concentration of caustic soda (N K ) is the mass volume concentration of NaOH (calculated as Na2O), carbon alkali concentration (N C ) is the mass volume concentration of Na2CO3 (calculated as Na2O).

[0060] In the embodiment of the present invention, a mixer is used for mixing raw materials, a ball press is used for making balls, and a dryer is used for preheating and drying.

[0061] In the embodiment of the present invention, a rotary kiln is used for sintering and a cooler is used for cooling.

[0062] In the embodiment of the present invention, the wet grinding leaching adopts a grid-type abrasive crusher with a graded liner, which is filled with steel ball grinding media. The rotation speed of the abrasive crusher is 15r / min~30r / min, and the size of the steel ball is Φ20mm~Φ50mm.

[0063] In the embodiment of the present invention, a plate and frame filter press is used for rapid separation, and the working pressure of the plate and frame filter press is 1.0 MPa to 1.5 MPa.

[0064] Example 1

[0065] The high-iron and high-silicon red mud used in this embodiment is a by-product of alumina extraction by the Bayer process, and contains, by mass percentage, 37.34% Fe2O3, 22.73% Al2O3, 8.72% SiO2, 5.03% TiO2, 8.74% CaO, and 4.65% Na2O, with an aluminum-silicon ratio of 2.61.

[0066] A method for recovering iron, aluminum and sodium from high-iron and high-silicon red mud by step sintering, the process flow chart is as follows: Figure 1 As shown, the specific steps include:

[0067] (1) The high iron and high silicon red mud and lime are crushed and ground respectively until the particle size ≤ 0.074 mm accounts for ≥ 85% of the total mass, and then 15.67 wt.% of industrial sodium carbonate, 11.06 wt.% of lime and 1 wt.% of sodium fluoride are added to the high iron and high silicon red mud to obtain a mixed material for use.

[0068] (2) Water is added to the mixed material to form pellets. During the preparation process, the moisture content of the pellets is controlled to be 18.20%.

[0069] (3) The water-containing pellets are preheated and dried outside the kiln at a preheating temperature of 280°C to remove the adsorbed water, part of the crystallized water and other volatile components in the pellets.

[0070] (4) The preheated pellets are transferred to a rotary kiln and subjected to oxidation sintering at 800°C for 1 hour. The temperature gradient and oxygen partial pressure in the reactor are controlled to ensure that the sintering process is in a stable oxidizing environment. The tail gas generated during the oxidation sintering process is returned to step (3) to provide a heat source for the preheating process.

[0071] (5) The pellets obtained by oxidation sintering are fed into a rotary kiln and heated to 1000°C in a reducing atmosphere for deep reduction sintering. The reducing atmosphere is CO and H2 provided by natural gas cracking gas or coal powder pyrolysis. The amount of reducing gas used is 1.1 times the theoretical amount used to reduce hematite to metallic iron. The sintering time is 1 hour. After sintering, the pellets are cooled to below 80°C by water quenching. The tail gas generated during the deep reduction sintering process is returned to step (4) to provide a heat source for oxidation sintering.

[0072] (6) The pellets of the reduced sintered product obtained in step (5) are mixed with a dilute alkali solution and then fed into a grid-type abrasive mill with a graded liner for coordinated fine grinding and leaching. The dilute alkali solution is a mixture of sodium hydroxide solution and sodium carbonate solution, wherein the concentration of the sodium hydroxide solution is N K The concentration of sodium carbonate solution is 15g / L. cThe concentration of leached slurry was 5 g / L, the liquid-solid ratio of the dilute alkali solution to the reduced sintered product pellets was 300 g / L, the leaching temperature was 85 ° C, the leaching time was 15 min, and the obtained leaching slurry was quickly separated by a plate and frame filter press to obtain sodium aluminate solution and leaching residue.

[0073] (7) The leached residue is subjected to wet magnetic separation to obtain high-quality iron concentrate and waste residue. The magnetic field intensity of the wet magnetic separation is 1250 Oe, and the iron in the high-iron and high-silicon red mud is recovered.

[0074] The recovery rate of aluminum oxide obtained in this embodiment is 91.85%, and the recovery rate of sodium oxide is 98.34%. The iron grade in the iron concentrate is 72.57%, the Al2O3 content is 1.70%, and the iron recovery rate is 91.25%.

[0075] Example 2

[0076] The high-iron and high-silicon red mud used in this embodiment is a by-product of alumina extraction by the Bayer process, and contains, by mass percentage, 37.34% Fe2O3, 22.73% Al2O3, 8.72% SiO2, 5.03% TiO2, 8.74% CaO, and 4.65% Na2O, with an aluminum-silicon ratio of 2.61.

[0077] A method for recovering sodium iron, aluminum and iron from high-iron and high-silicon red mud by step sintering, specifically comprising the following steps:

[0078] (1) The high iron and high silicon red mud and lime are crushed and ground respectively until the particle size of the portion ≤ 0.074 mm accounts for ≥ 85% of the total mass, and then 18.03 wt.% of industrial sodium carbonate, 13.04 wt.% of lime and 1.5 wt.% of calcium fluoride are added to the high iron and high silicon red mud to obtain a mixed material for use.

[0079] (2) Water is added to the mixed material to form pellets. During the preparation process, the moisture content of the pellets is controlled to be 22.75%.

[0080] (3) The water-containing pellets are preheated and dried outside the kiln at a preheating temperature of 350°C to remove the adsorbed water, part of the crystallized water and other volatile components in the pellets.

[0081] (4) The preheated pellets are transferred to a rotary kiln and subjected to oxidation sintering at 830°C for 1.2 h. The temperature gradient and oxygen partial pressure in the reactor are controlled to ensure that the sintering process is in a stable oxidizing environment. The tail gas generated during the oxidation sintering process is returned to step (3) to provide a heat source for the preheating process.

[0082] (5) The pellets obtained by oxidation sintering are fed into a rotary kiln and heated to 980°C in a reducing atmosphere for deep reduction sintering. The reducing atmosphere is CO and H2 provided by natural gas cracking gas or coal powder pyrolysis. The amount of reducing gas used is 1.1 times the theoretical amount used to reduce hematite to metallic iron. The sintering time is 1.2 h. After sintering, the pellets are cooled to below 80°C by water quenching. The tail gas generated during the deep reduction sintering process is returned to step (4) to provide a heat source for oxidation sintering.

[0083] (6) The pellets of the reduced sintered product obtained in step (5) are mixed with a dilute alkali solution and then fed into a grid-type abrasive mill with a graded liner for coordinated fine grinding and leaching. The dilute alkali solution is a mixture of sodium hydroxide solution and sodium carbonate solution, wherein the concentration of the sodium hydroxide solution is N K The concentration of sodium carbonate solution is 20g / L. c The sodium aluminate solution and the leaching residue were obtained by rapid separation of the leached slurry using a plate and frame filter press.

[0084] (7) The leached residue is subjected to wet magnetic separation to obtain high-quality iron concentrate and waste residue. The magnetic field intensity of the wet magnetic separation is 1300 Oe, and the iron in the high-iron and high-silicon red mud is recovered.

[0085] The recovery rate of aluminum oxide obtained in this embodiment is 92.00%, and the recovery rate of sodium oxide is 98.45%. The iron grade in the iron concentrate is 72.65%, the Al2O3 content is 1.60%, and the iron recovery rate is 91.55%.

[0086] Example 3

[0087] The high-iron and high-silicon red mud used in this embodiment is a by-product of alumina extraction by the Bayer process, and contains, by mass percentage, 28.41% Fe2O3, 25.10% Al2O3, 12.75% SiO2, 3.05% TiO2, 14.08% CaO, and 4.82% Na2O, with an aluminum-silicon ratio of 1.96.

[0088] A method for recovering sodium iron, aluminum and iron from high-iron and high-silicon red mud by step sintering, specifically comprising the following steps:

[0089] (1) The high iron and high silicon red mud and lime are crushed and ground respectively until the particle size ≤ 0.074 mm accounts for ≥ 85% of the total mass, and then 16.54 wt.% of industrial sodium carbonate, 10.56 wt.% of lime and 1 wt.% of sodium fluoride are added to the high iron and high silicon red mud to obtain a mixed material for use.

[0090] (2) Water is added to the mixed material to prepare pellets. During the preparation process, the moisture content of the pellets is controlled to be 18.50%.

[0091] (3) The water-containing pellets are preheated and dried outside the kiln at a preheating temperature of 300°C to remove the adsorbed water, part of the crystallized water and other volatile components in the pellets.

[0092] (4) The preheated pellets are transferred to a rotary kiln and subjected to oxidation sintering at 800°C for 1 hour. The temperature gradient and oxygen partial pressure in the reactor are controlled to ensure that the sintering process is in a stable oxidizing environment. The tail gas generated during the oxidation sintering process is returned to step (3) to provide a heat source for the preheating process.

[0093] (5) The pellets obtained by oxidation sintering are fed into a rotary kiln and heated to 1000°C in a reducing atmosphere for deep reduction sintering. The reducing atmosphere is CO and H2 provided by natural gas cracking gas or coal powder pyrolysis. The amount of reducing gas used is 1.1 times the theoretical amount used to reduce hematite to metallic iron. The sintering time is 1 hour. After sintering, the pellets are cooled to below 80°C by water quenching. The tail gas generated during the deep reduction sintering process is returned to step (4) to provide a heat source for oxidation sintering.

[0094] (6) The pellets of the reduced sintered product obtained in step (5) are mixed with a dilute alkali solution and then fed into a grid-type abrasive mill with a graded liner for coordinated fine grinding and leaching. The dilute alkali solution is a mixture of sodium hydroxide solution and sodium carbonate solution, wherein the concentration of the sodium hydroxide solution is N K The concentration of sodium carbonate solution is 15g / L. c The concentration of leached slurry was 5 g / L, the liquid-solid ratio of the dilute alkali solution to the reduced sintered product pellets was 300 g / L, the leaching temperature was 85 ° C, the leaching time was 15 min, and the obtained leaching slurry was quickly separated by a plate and frame filter press to obtain sodium aluminate solution and leaching residue.

[0095] (7) The leached residue is subjected to wet magnetic separation to obtain high-quality iron concentrate and waste residue. The magnetic field intensity of the wet magnetic separation is 1450 Oe, and the iron in the high-iron and high-silicon red mud is recovered.

[0096] The recovery rate of aluminum oxide obtained in this embodiment is 92.72%, and the recovery rate of sodium oxide is 98.91%. The iron grade in the iron concentrate is 73.65%, the Al2O3 content is 1.73%, and the iron recovery rate is 90.27%.

[0097] Example 4

[0098] The high-iron and high-silicon red mud used in this embodiment is a by-product of alumina extraction by the Bayer process, and contains, by mass percentage, 28.41% Fe2O3, 25.10% Al2O3, 12.75% SiO2, 3.05% TiO2, 14.08% CaO, and 4.82% Na2O, with an aluminum-silicon ratio of 1.96.

[0099] A method for recovering sodium iron, aluminum and iron from high-iron and high-silicon red mud by step sintering, specifically comprising the following steps:

[0100] (1) The high iron and high silicon red mud and lime are crushed and ground respectively until the particle size of the portion ≤ 0.074 mm accounts for ≥ 85% of the total mass, and then 17.84 wt.% of industrial sodium carbonate, 11.86 wt.% of lime and 1.5 wt.% of calcium fluoride are added to the high iron and high silicon red mud to obtain a mixed material for use.

[0101] (2) Water is added to the mixed material to form pellets. During the preparation process, the moisture content of the pellets is controlled to be 20.75%.

[0102] (3) The water-containing pellets are preheated and dried outside the kiln at a preheating temperature of 325°C to remove the adsorbed water, part of the crystallized water and other volatile components in the pellets.

[0103] (4) The preheated pellets are transferred to a rotary kiln and subjected to oxidation sintering at 830°C for 1.2 h. The temperature gradient and oxygen partial pressure in the reactor are controlled to ensure that the sintering process is in a stable oxidizing environment. The tail gas generated during the oxidation sintering process is returned to step (3) to provide a heat source for the preheating process.

[0104] (5) The pellets obtained by oxidation sintering are fed into a rotary kiln and heated to 980°C in a reducing atmosphere for deep reduction sintering. The reducing atmosphere is CO and H2 provided by natural gas cracking gas or coal powder pyrolysis. The amount of reducing gas used is 1.1 times the theoretical amount used to reduce hematite to metallic iron. The sintering time is 1.2 h. After sintering, the pellets are cooled to below 80°C by water quenching. The tail gas generated during the deep reduction sintering process is returned to step (4) to provide a heat source for oxidation sintering.

[0105] (6) The pellets of the reduced sintered product obtained in step (5) are mixed with a dilute alkali solution and then fed into a grid-type abrasive mill with a graded liner for coordinated fine grinding and leaching. The dilute alkali solution is a mixture of sodium hydroxide solution and sodium carbonate solution, wherein the concentration of the sodium hydroxide solution is N K The concentration of sodium carbonate solution is 20g / L. c The sodium aluminate solution and the leaching residue were obtained by rapid separation of the leached slurry using a plate and frame filter press.

[0106] (7) The leached residue is subjected to wet magnetic separation to obtain high-quality iron concentrate and waste residue. The magnetic field intensity of the wet magnetic separation is 1350 Oe, and the iron in the high-iron and high-silicon red mud is recovered.

[0107] The recovery rate of aluminum oxide obtained in this embodiment is 92.05%, and the recovery rate of sodium oxide is 98.22%. The iron grade in the iron concentrate is 71.89%, the Al2O3 content is 1.74%, and the iron recovery rate is 90.59%.

[0108] Example 5

[0109] The high-iron and high-silicon red mud used in this embodiment is a by-product of alumina extraction by the Bayer process, and contains, by mass percentage, 28.41% Fe2O3, 25.10% Al2O3, 12.75% SiO2, 3.05% TiO2, 14.08% CaO, and 4.82% Na2O, with an aluminum-silicon ratio of 1.96.

[0110] A method for recovering sodium iron, aluminum and iron from high-iron and high-silicon red mud by step sintering, specifically comprising the following steps:

[0111] (1) The high iron and high silicon red mud and lime are crushed and ground respectively until the particle size ≤ 0.074 mm accounts for ≥ 85% of the total mass, and then 20.45 wt.% of industrial sodium carbonate, 14.45 wt.% of lime and 1.2 wt.% of fluorite are added to the high iron and high silicon red mud to obtain a mixed material for use.

[0112] (2) Water is added to the mixed material to form pellets. During the preparation process, the moisture content of the pellets is controlled to be 22.55%.

[0113] (3) The water-containing pellets are preheated and dried outside the kiln at a preheating temperature of 375°C to remove the adsorbed water, part of the crystallized water and other volatile components in the pellets.

[0114] (4) The preheated pellets are transferred to a rotary kiln and subjected to oxidation sintering at 850°C for 1.3 h. The temperature gradient and oxygen partial pressure in the reactor are controlled to ensure that the sintering process is in a stable oxidizing environment. The tail gas generated during the oxidation sintering process is returned to step (3) to provide a heat source for the preheating process.

[0115] (5) The pellets obtained by oxidation sintering are fed into a rotary kiln and heated to 960°C in a reducing atmosphere for deep reduction sintering. The reducing atmosphere is CO and H2 provided by natural gas cracking gas or coal powder pyrolysis. The amount of reducing gas used is 1.1 times the theoretical amount used to reduce hematite to metallic iron. The sintering time is 1.3 h. After sintering, the pellets are cooled to below 80°C by water quenching. The tail gas generated during the deep reduction sintering process is returned to step (4) to provide a heat source for oxidation sintering.

[0116] (6) The pellets of the reduced sintered product obtained in step (5) are mixed with a dilute alkali solution and then fed into a grid-type abrasive mill with a graded liner for coordinated fine grinding and leaching. The dilute alkali solution is a mixture of sodium hydroxide solution and sodium carbonate solution, wherein the concentration of the sodium hydroxide solution is NK The concentration of sodium carbonate solution is 15g / L. c The concentration of sodium aluminate in the leached slurry was 5 g / L, the liquid-solid ratio of the dilute alkali solution to the reduced sintered product pellets was 400 g / L, the leaching temperature was 75°C, the leaching time was 30 min, and the obtained leached slurry was quickly separated by a plate and frame filter press to obtain sodium aluminate solution and leaching residue.

[0117] (7) The leached residue is subjected to wet magnetic separation to obtain high-quality iron concentrate and waste residue. The magnetic field intensity of the wet magnetic separation is 1280 Oe, and the iron in the high-iron and high-silicon red mud is recovered.

[0118] The recovery rate of aluminum oxide obtained in this embodiment is 92.80%, and the recovery rate of sodium oxide is 98.75%. The iron grade in the iron concentrate is 71.50%, the Al2O3 content is 1.65%, and the iron recovery rate is 91.22%.

[0119] Example 6

[0120] The high-iron and high-silicon red mud used in this embodiment is a by-product of alumina extraction by the Bayer process, and contains, by mass percentage, 26.58% Fe2O3, 27.54% Al2O3, 14.50% SiO2, 2.45% TiO2, 15.07% CaO, and 4.07% Na2O, with an aluminum-silicon ratio of 1.90.

[0121] A method for recovering sodium iron, aluminum and iron from high-iron and high-silicon red mud by step sintering, specifically comprising the following steps:

[0122] (1) The high iron and high silicon red mud and lime are crushed and ground respectively until the particle size ≤ 0.074 mm accounts for ≥ 85% of the total mass, and then 20.23 wt.% of industrial sodium carbonate, 12.27 wt.% of lime and 1 wt.% of sodium fluoride are added to the high iron and high silicon red mud to obtain a mixed material for use.

[0123] (2) Water is added to the mixed material to form pellets. During the preparation process, the moisture content of the pellets is controlled to be 18.70%.

[0124] (3) The water-containing pellets are preheated and dried outside the kiln at a preheating temperature of 300°C to remove the adsorbed water, part of the crystallized water and other volatile components in the pellets.

[0125] (4) The preheated pellets are transferred to a rotary kiln and subjected to oxidation sintering at 800°C for 1 hour. The temperature gradient and oxygen partial pressure in the reactor are controlled to ensure that the sintering process is in a stable oxidizing environment. The tail gas generated during the oxidation sintering process is returned to step (3) to provide a heat source for the preheating process.

[0126] (5) The pellets obtained by oxidation sintering are fed into a rotary kiln and heated to 1000°C in a reducing atmosphere for deep reduction sintering. The reducing atmosphere is CO and H2 provided by natural gas cracking gas or coal powder pyrolysis. The amount of reducing gas used is 1.1 times the theoretical amount used to reduce hematite to metallic iron. The sintering time is 1 hour. After sintering, the pellets are cooled to below 80°C by water quenching. The tail gas generated during the deep reduction sintering process is returned to step (4) to provide a heat source for oxidation sintering.

[0127] (6) The pellets of the reduced sintered product obtained in step (5) are mixed with a dilute alkali solution and then fed into a grid-type abrasive mill with a graded liner for coordinated fine grinding and leaching. The dilute alkali solution is a mixture of sodium hydroxide solution and sodium carbonate solution, wherein the concentration of the sodium hydroxide solution is N K The concentration of sodium carbonate solution is 15g / L. c The liquid-solid ratio of the dilute alkali solution to the reduced sintered product pellets is 5 g / L, the liquid-solid ratio is 300 g / L, the leaching temperature is 85 ° C, the leaching time is 15 min, and the obtained leaching slurry is quickly separated into solid and liquid to obtain sodium aluminate solution and leaching residue.

[0128] (7) The leached residue is subjected to wet magnetic separation to obtain high-quality iron concentrate and waste residue. The magnetic field intensity of the wet magnetic separation is 1450 Oe, and the iron in the high-iron and high-silicon red mud is recovered.

[0129] The recovery rate of aluminum oxide obtained in this embodiment is 90.85%, and the recovery rate of sodium oxide is 98.10%. The iron grade in the iron concentrate is 70.39%, the Al2O3 content is 1.62%, and the iron recovery rate is 90.57%.

[0130] Example 7

[0131] The high-iron and high-silicon red mud used in this embodiment is a by-product of alumina extraction by the Bayer process, and contains, by mass percentage, 26.58% Fe2O3, 27.54% Al2O3, 14.50% SiO2, 2.45% TiO2, 15.07% CaO, 4.07% Na2O, and an aluminum-silicon ratio of 1.90.

[0132] A method for recovering sodium iron, aluminum and iron from high-iron and high-silicon red mud by step sintering, specifically comprising the following steps:

[0133] (1) The high iron and high silicon red mud and lime are crushed and ground respectively until the particle size ≤ 0.074 mm accounts for ≥ 85% of the total mass, and then 21.66 wt.% of industrial sodium carbonate, 13.71 wt.% of lime and 1.5 wt.% of calcium fluoride are added to the high iron and high silicon red mud to obtain a mixed material for use.

[0134] (2) Water is added to the mixed material to form pellets. During the preparation process, the moisture content of the pellets is controlled to be 20.95%.

[0135] (3) The water-containing pellets are preheated and dried outside the kiln at a preheating temperature of 325°C to remove the adsorbed water, part of the crystallized water and other volatile components in the pellets.

[0136] (4) The preheated pellets are transferred to a rotary kiln and subjected to oxidation sintering at 830°C for 1.2 h. The temperature gradient and oxygen partial pressure in the reactor are controlled to ensure that the sintering process is in a stable oxidizing environment. The tail gas generated during the oxidation sintering process is returned to step (3) to provide a heat source for the preheating process.

[0137] (5) The pellets obtained by oxidation sintering are fed into a rotary kiln and heated to 980°C in a reducing atmosphere for deep reduction sintering. The reducing atmosphere is CO and H2 provided by natural gas cracking gas or coal powder pyrolysis. The amount of reducing gas used is 1.1 times the theoretical amount used to reduce hematite to metallic iron. The sintering time is 1.2 h. After sintering, the pellets are cooled to below 80°C by water quenching. The tail gas generated during the deep reduction sintering process is returned to step (4) to provide a heat source for oxidation sintering.

[0138] (6) The pellets of the reduced sintered product obtained in step (5) are mixed with a dilute alkali solution and then fed into a grid-type abrasive mill with a graded liner for coordinated fine grinding and leaching. The dilute alkali solution is a mixture of sodium hydroxide solution and sodium carbonate solution, wherein the concentration of the sodium hydroxide solution is N K The concentration of sodium carbonate solution is 20g / L. c The sodium aluminate solution and the leaching residue were obtained by rapid separation of the leached slurry using a plate and frame filter press.

[0139] (7) The leached residue is subjected to wet magnetic separation to obtain high-quality iron concentrate and waste residue. The magnetic field intensity of the wet magnetic separation is 1350 Oe, and the iron in the high-iron and high-silicon red mud is recovered.

[0140] The recovery rate of aluminum oxide obtained in this embodiment is 91.88%, and the recovery rate of sodium oxide is 98.45%. The iron grade in the iron concentrate is 71.27%, the Al2O3 content is 1.66%, and the iron recovery rate is 90.20%.

[0141] Example 8

[0142] The high-iron and high-silicon red mud used in this embodiment is a by-product of alumina extraction by the Bayer process, and contains, by mass percentage, 26.58% Fe2O3, 27.54% Al2O3, 14.50% SiO2, 2.45% TiO2, 15.07% CaO, 4.07% Na2O, and an aluminum-silicon ratio of 1.90.

[0143] A method for recovering sodium iron, aluminum and iron from high-iron and high-silicon red mud by step sintering, specifically comprising the following steps:

[0144] (1) The high iron and high silicon red mud and lime are crushed and ground respectively until the particle size ≤ 0.074 mm accounts for ≥ 85% of the total mass, and then 24.52 wt.% of industrial sodium carbonate, 16.59 wt.% of lime and 1.2 wt.% of boron magnesium ore are added to the high iron and high silicon red mud to obtain a mixed material for use.

[0145] (2) Water is added to the mixed material to prepare pellets. During the preparation process, the moisture content of the pellets is controlled to be 22.80%.

[0146] (3) The water-containing pellets are preheated and dried outside the kiln at a preheating temperature of 375°C to remove the adsorbed water, part of the crystallized water and other volatile components in the pellets.

[0147] (4) The preheated pellets are transferred to a rotary kiln and subjected to oxidation sintering at 850°C for 1.3 h. The temperature gradient and oxygen partial pressure in the reactor are controlled to ensure that the sintering process is in a stable oxidizing environment. The tail gas generated during the oxidation sintering process is returned to step (3) to provide a heat source for the preheating process.

[0148] (5) The pellets obtained by oxidation sintering are fed into a rotary kiln and heated to 960°C in a reducing atmosphere for deep reduction sintering. The reducing atmosphere is CO and H2 provided by natural gas cracking gas or coal powder pyrolysis. The amount of reducing gas used is 1.1 times the theoretical amount used to reduce hematite to metallic iron. The sintering time is 1.3 h. After sintering, the pellets are cooled to below 80°C by water quenching. The tail gas generated during the deep reduction sintering process is returned to step (4) to provide a heat source for oxidation sintering.

[0149] (6) The pellets of the reduced sintered product obtained in step (5) are mixed with a dilute alkali solution and then fed into a grid-type abrasive mill with a graded liner for coordinated fine grinding and leaching. The dilute alkali solution is a mixture of sodium hydroxide solution and sodium carbonate solution, wherein the concentration of the sodium hydroxide solution is N K The concentration of sodium carbonate solution is 15g / L. c The concentration of sodium aluminate in the leached slurry was 5 g / L, the liquid-solid ratio of the dilute alkali solution to the reduced sintered product pellets was 400 g / L, the leaching temperature was 75°C, the leaching time was 30 min, and the obtained leached slurry was quickly separated by a plate and frame filter press to obtain sodium aluminate solution and leaching residue.

[0150] (7) The leached residue is subjected to wet magnetic separation to obtain high-quality iron concentrate and waste residue. The magnetic field intensity of the wet magnetic separation is 1280 Oe, and the iron in the high-iron and high-silicon red mud is recovered.

[0151] The recovery rate of aluminum oxide obtained in this embodiment is 92.85%, and the recovery rate of sodium oxide is 98.60%. The iron grade in the iron concentrate is 71.34%, the Al2O3 content is 1.71%, and the iron recovery rate is 91.35%.

Claims

1. A method for recovering sodium iron, aluminum and iron from high-iron and high-silicon red mud by step sintering, characterized in that: The specific steps include: (1) High iron and high silicon red mud and lime are crushed and ground separately, and then fully mixed with industrial sodium carbonate and flux according to the mass ratio; (2) adding water to the mixture to form pellets, and controlling the moisture content of the pellets during the preparation process; (3) Preheating and drying the water-containing pellets outside the kiln to remove the adsorbed water, part of the crystallized water and other volatile components in the pellets; (4) The preheated pellets are transferred to an oxidation sintering reactor for oxidation sintering, and the temperature gradient and oxygen partial pressure in the reactor are controlled to ensure that the sintering process is in a stable oxidizing environment; (5) The pellets obtained by oxidation sintering are sent to a reduction sintering reactor for deep reduction sintering under a reducing atmosphere. After sintering, the pellets are water quenched; (6) wet-grinding the sintered product obtained in step (5) in a ball mill to co-leach aluminum oxide and sodium oxide, and obtaining a sodium aluminate solution and a leached residue through rapid separation, and recovering aluminum and sodium from the obtained sodium aluminate solution; (7) The leached residue is subjected to wet magnetic separation to obtain high-quality iron concentrate and waste residue, and the iron in the high-iron and high-silicon red mud is recovered.

2. The method for recovering sodium iron, aluminum and iron from high-iron and high-silicon red mud by cascade sintering according to claim 1, characterized in that: In the step (1), the high-iron and high-silicon red mud is a by-product of alumina extraction by the Bayer process, and contains, by mass percentage, 20% to 50% of Fe2O3, 10% to 30% of Al2O3, 6% to 20% of SiO2, 2% to 8% of TiO2, 1% to 20% of CaO, and 1% to 10% of Na2O. The part of the ground mixed powder with a particle size of ≤0.074 mm accounts for ≥85% of the total mass. The amount of industrial sodium carbonate added to the mixture is 10 wt.% to 30 wt.% of the mass of the high-iron and high-silicon red mud, and the amount of lime added is 10 wt.% to 20 wt.% of the mass of the high-iron and high-silicon red mud.

3. The method for recovering sodium iron, aluminum and iron from high-iron and high-silicon red mud by step sintering according to claim 1, characterized in that: In the step (1), the flux is one or more of sodium borate, calcium borate, sodium fluoride, calcium fluoride, industrial fluorite and boron magnesium ore, and the added amount does not exceed 2wt.% of the mass of the high-iron and high-silicon red mud.

4. The method for recovering sodium iron, aluminum and iron from high-iron and high-silicon red mud by cascade sintering according to claim 1, characterized in that: In the step (2), the pellets are prepared by a pellet press, and the moisture content is 15% to 25%.

5. The method for recovering sodium iron, aluminum and iron from high-iron and high-silicon red mud by cascade sintering according to claim 1, characterized in that: In the step (3), the pellets are preheated by drying outside the kiln, with the preheating temperature being 200°C to 400°C.

6. The method for recovering sodium iron, aluminum and sodium from high-iron and high-silicon red mud by cascade sintering according to claim 1, characterized in that: In the step (4), the oxidation sintering reactor is a rotary kiln, the oxidation sintering temperature is 700° C. to 900° C., and the time is 0.5 h to 1.5 h; the tail gas generated during the oxidation sintering process is returned to step (3) to provide a heat source for the preheating process.

7. The method for recovering sodium iron, aluminum and iron from high-iron and high-silicon red mud by cascade sintering according to claim 1, characterized in that: In the step (5), the reduction sintering reactor is a chain grate, a tunnel kiln or a rotary kiln, and the reducing atmosphere is CO and H2 provided by natural gas cracking gas or coal powder pyrolysis, and the amount thereof is 1.0 to 1.2 times the theoretical amount required to reduce hematite to metallic iron; the temperature of the deep reduction sintering is 800° C. to 1000° C., and the time is 0.5 h to 1.5 h. After the sintering is completed, the pellets are cooled to below 80° C. by water quenching; the tail gas generated during the deep reduction sintering process is returned to step (4) to provide a heat source for the oxidative sintering.

8. The method for recovering sodium iron, aluminum and sodium from high-iron and high-silicon red mud by cascade sintering according to claim 1, characterized in that: In the step (6), a plate and frame filter press is used for rapid separation, and the working pressure is 1.0 MPa to 1.5 MPa.

9. The method for recovering sodium iron, aluminum and sodium from high-iron and high-silicon red mud by cascade sintering according to claim 1, characterized in that: In the step (6), the recovery rate of aluminum oxide in the sintered product is ≥90%, and the recovery rate of sodium oxide is ≥96%.

10. The method for recovering sodium iron, aluminum and sodium from high-iron and high-silicon red mud by cascade sintering according to claim 1, characterized in that: In the step (7), the magnetic field strength of the magnetic separation is 1000Oe to 3000Oe, the iron grade in the high-quality iron ore concentrate is ≥70%, and the iron recovery rate is ≥90%.

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