A method for leaching and iron recovery of high-iron diaspore type bauxite

Abstract

The application belongs to the technical field of nonferrous metallurgy, and discloses a method for dissolving high-iron diaspore type bauxite and recovering iron. The method comprises the following steps: (1) preparing a mixed ore slurry by mixing high-iron diaspore type bauxite, sodium aluminate circulating mother liquor and an additive; the additive is a mixture of one or more of organic alkali, carboxylic acid and amino acid; (2) heating the mixed ore slurry obtained in step (1) to 190-280 DEG C to perform a dissolving reaction, obtaining a dissolving slurry and a dissolving residue, and recovering iron concentrate by performing magnetic separation on the dissolving residue. The method solves the problem of difficult separation of iron minerals caused by silicon minerals in the dissolving process of high-iron diaspore type bauxite. The method has simple process, low production cost, low equipment requirement and good industrialization prospect.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of non-ferrous metallurgy, and particularly relates to a dissolution and iron recovery method of high-iron diaspore type bauxite. BACKGROUND

[0002] When traditional bauxite dissolution methods are used to produce alumina, only single aluminum resources are collected, and high-proportion iron minerals are generally discharged as red mud waste components, which causes serious environmental problems and also results in great waste of iron resources. Another problem in the utilization of iron resources in high-iron diaspore type bauxite is the close combination of iron minerals and silicon minerals. When iron minerals are used as raw materials for the steel industry, the silicon mineral impurities will cause the blast furnace slag to become thick, increase the amount of slag and energy consumption, and the iron ore with too high silicon content has no utilization value.

[0003] Therefore, if the iron minerals and silicon minerals in the high-iron diaspore type bauxite can be dissociated and separated during the bauxite dissolution production process, the iron components can be recovered, which not only can greatly reduce the amount of red mud waste discharged in the alumina production process, but also can obtain high-grade iron minerals for utilization, and the environmental and economic benefits are taken into account. Therefore, it is necessary to improve the existing dissolution method to realize the efficient utilization of iron components in high-iron diaspore type bauxite.

[0004] CN107201441A discloses a high-iron bauxite comprehensive utilization method and an additive for high-iron bauxite treatment. The method first mixes fine ground high-iron bauxite with the additive, makes blocks, dries, and reduces and roasts with coal as a reducing agent. The roasted blocks are crushed, ground, and then the iron components are separated by magnetic separation. The method needs to add an additional high-temperature roasting process, and the subsequent utilization of aluminum resources needs to be realized by two-step wet process of acid dissolution and alkali neutralization, which has many steps, high production cost and brings a large amount of low-value by-products.

[0005] CN102976374B discloses a method for converting iron minerals in the production of alumina, which adds one or more of iron or divalent iron compounds as additives in the bauxite digestion system to convert the iron minerals in the bauxite into magnetite for separation and recovery, but it does not mention the content of silicon impurities in the recovered iron, and the divalent iron compounds (siderite, pyrite, ferrous chloride, ferrous sulfate, etc.) contain impurity anions, which may affect the purity of alumina products when introduced into the bauxite digestion process. Similarly, CN102976375B discloses a high-pressure digestion method for diaspore-type bauxite, which uses at least one of iron powder and ether cellulose as an additive to physically and chemically interact with the surface of titanium minerals, thereby reducing the concentration of titanate ions in the solution and eliminating the blocking effect of titanium minerals on alumina digestion. This patent is mainly for promoting alumina digestion and does not involve promoting the separation of iron minerals and silicon minerals. CN102976377B discloses a digestion method for diaspore-type bauxite, which introduces a mixture of one or more of alcohols, sugars, aldehydes, alkanes, activated carbon, graphite, coal, coal tar, and wheat bran as additives instead of traditional additives such as lime to solve the problem of titanium minerals hindering bauxite digestion, and to magnetically transform iron minerals. This method also does not take into account the effect of silicon mineral impurities on iron component recovery, and the mass percentage of total iron (TFe) in the obtained iron concentrate (56.30% to 62.12%) and the recovery rate of iron in the bauxite (37.82% to 50.26%) are not high, and the new additives contain a variety of long-chain carbon organic matter (sugars, alkanes, coal, coal tar, wheat bran, etc.), which can easily increase the content of organic matter in the bauxite digestion cycle and affect the quality of alumina products.

[0006] In summary, there is an urgent need to develop a digestion method for high-iron diaspore-type bauxite that can solve the problem of the combination of iron minerals and silicon minerals in high-iron bauxite, and more efficiently and cost-effectively solve the problem of iron resource utilization in high-iron bauxite. SUMMARY

[0007] In view of the shortcomings and deficiencies of the prior art, the purpose of the present application is to provide a digestion and iron recovery method for high-iron diaspore-type bauxite. The method is simple, low in production cost, low in equipment demand, and has good industrialization prospects.

[0008] The purpose of the present application is achieved by the following technical solutions:

[0009] A digestion and iron recovery method for high-iron diaspore-type bauxite, comprising the following steps:

[0010] (1) preparing a mixed ore slurry by mixing high-iron diaspore bauxite, sodium aluminate circulating mother liquor and an additive; the additive is a mixture of one or more of organic bases, carboxylic acids and amino acids;

[0011] (2) heating the mixed ore slurry obtained in step (1) to 190-280℃ to perform a leaching reaction, obtaining a leaching slurry and a leaching residue, and recovering iron concentrate by magnetic separation of the leaching residue.

[0012] Further, the high-iron diaspore bauxite in step (1) refers to bauxite with a main component of diaspore and an iron mineral content of >15% (mass percentage of Fe2O3).

[0013] Further, the Na2O concentration of the sodium aluminate circulating mother liquor in step (1) is 160-280 g / L, and the Al2O3 concentration is 75-140 g / L. k The concentration of Na2O is 160-280 g / L, and the concentration of Al2O3 is 75-140 g / L.

[0014] Further, the mass / volume ratio of the high-iron diaspore bauxite to the sodium aluminate circulating mother liquor in step (1) is 130-360 g / L.

[0015] Further, the mass / volume ratio of the additive to the circulating mother liquor in step (1) is 0.5-50 g / L.

[0016] Further, the organic base in step (1) is preferably at least one of choline, triethanolamine, ethylenediamine and diethylenetriamine; the carboxylic acid is preferably acetic acid; and the amino acid is preferably glycine.

[0017] Further preferably, the additive in step (1) is choline, triethanolamine, ethylenediamine or diethylenetriamine; more preferably choline. It has been verified by the present application that when the additive is selected from choline, triethanolamine, ethylenediamine or diethylenetriamine, it has good interface adjustment function and reducing property at the same time, can significantly promote the reduction reaction of iron minerals in the ore to generate magnetite or iron with magnetism, and promote the dispersion and dissociation of iron minerals and silicon mineral impurities in high-iron diaspore bauxite, thereby improving the iron recovery rate of bauxite and reducing the silicon impurity content in the iron concentrate obtained by magnetic separation of the leaching residue of bauxite.

[0018] Further, the time of the leaching reaction in step (2) is 30-90 min.

[0019] Further preferably, the leaching reaction in step (2) refers to first heating to 90-120℃ for pre-reaction for 90-210 min, and then heating to 190-280℃ for reaction for 30-90 min.

[0020] Further, the dilution of the leaching slurry in step (2) is subjected to a precision filtration treatment, the obtained filtrate is added with seed crystals to promote the decomposition of sodium aluminate in the solution to generate aluminum hydroxide, and after the solid-liquid separation again, the aluminum hydroxide solid is obtained, and the aluminum oxide product is obtained by further calcination, and the liquid is returned to the leaching process for continuous use.

[0021] The principle of the present application is that: by adding a reducing additive with the function of adjusting the surface and interface properties, the iron minerals in the bauxite ore are subjected to a reduction reaction to generate magnetite or iron single substance with magnetism, and the surface properties of the iron minerals are adjusted to make the closely connected silicon mineral impurities dispersed and dissociated, so that the iron minerals can be separated and enriched by simple magnetic separation.

[0022] Compared with the prior art, the present application has the following beneficial effects:

[0023] (1) Compared with the traditional leaching method by adding lime, the additive amount of the present application is low, and the amount of red mud discharged is greatly reduced, which has a significant environmental protection advantage.

[0024] (2) The present application method only uses a small amount of additive, which can complete the enrichment and removal of silicon impurities of iron minerals in the bauxite leaching process, and convert into easily separated magnetic iron minerals, greatly improving the iron resource recovery efficiency.

[0025] (3) The present application method does not need to add other large equipment in the existing leaching production process, and has low cost and is simple and easy to implement. DETAILED DESCRIPTION

[0026] The present application will be further described in detail below in combination with examples, but the implementation of the present application is not limited thereto.

[0027] Example 1

[0028] A high-iron diaspore type bauxite ore (mineral composition: Al2O3 60.60%, Fe2O3 25.61%, SiO2 10.76%) is prepared into a mixed ore slurry with 200 mL of circulating mother liquor and an additive triethanolamine. Among them, in the circulating mother liquor: Na2O 2.50%, Al2O3 0.50%, Fe2O3 0.50%, SiO2 0.50%, and the additive triethanolamine is 0.50% of the total weight of the ore slurry. kThe bauxite was added in a mass / volume ratio of 250 g / L to the circulating mother liquor, and the Al2O3 concentration was 125 g / L. The bauxite was added in a mass / volume ratio of 224 g / L to the circulating mother liquor, and the additive was added in a mass / volume ratio of 5 g / L to the circulating mother liquor. The mixed ore slurry was pre-reacted at 95 ℃ for 180 min and then heated to 260 ℃ for leaching for 60 min to obtain a leaching slurry and a leaching residue. The leaching residue obtained under the above conditions was subjected to magnetic separation at a magnetic field strength of 160 kA / m, and the total iron (calculated as Fe2O3) mass percentage of the obtained iron concentrate was 81.68% (total iron mass percentage = iron mass (calculated as Fe2O3) in the iron concentrate / iron concentrate mass × 100%), the silicon impurity (calculated as SiO2) mass percentage was 3.13%, and the iron recovery rate of the bauxite was 69.5% (iron recovery rate = iron mass (calculated as Fe2O3) in the iron concentrate / iron mass in the bauxite × 100%). The relative leaching rate of alumina was 97.14% (relative leaching rate of alumina = (iron-silicon ratio of the bauxite-iron-silicon ratio of the leaching residue) / (iron-silicon ratio of the bauxite-1) × 100%). The leaching slurry was diluted and subjected to precision filtration treatment, the obtained filtrate was added with seed crystals to promote the decomposition of sodium aluminate in the solution to form aluminum hydroxide, and after the second solid-liquid separation, aluminum hydroxide solids were obtained, which were further calcined to obtain alumina products, and the liquid was returned to the leaching process for continuous use. The obtained alumina products meet the GB / T 24487-2022 standard.

[0029] Example 2

[0030] A high-iron diaspore type bauxite (mineral composition same as that in Example 1), 200 mL of circulating mother liquor and an additive choline were prepared into a mixed ore slurry. In the circulating mother liquor: Na2O k The bauxite was added in a mass / volume ratio of 230 g / L to the circulating mother liquor, and the Al2O3 concentration was 110 g / L. The bauxite was added in a mass / volume ratio of 250 g / L to the circulating mother liquor, and the additive was added in a mass / volume ratio of 6 g / L to the circulating mother liquor. The mixed ore slurry was pre-reacted at 100 ℃ for 120 min and then heated to 260 ℃ for leaching for 90 min to obtain a leaching slurry and a leaching residue. The leaching residue obtained under the above conditions was subjected to magnetic separation at a magnetic field strength of 160 kA / m, and the total iron (calculated as Fe2O3) mass percentage of the obtained iron concentrate was 88.12%, the silicon impurity (calculated as SiO2) mass percentage was 2.28%, and the iron recovery rate of the bauxite was 76.44%. The relative leaching rate of alumina was 98.92%. The leaching slurry was diluted and subjected to precision filtration treatment, the obtained filtrate was added with seed crystals to promote the decomposition of sodium aluminate in the solution to form aluminum hydroxide, and after the second solid-liquid separation, aluminum hydroxide solids were obtained, which were further calcined to obtain alumina products, and the liquid was returned to the leaching process for continuous use. The obtained alumina products meet the GB / T 24487-2022 standard.

[0031] Example 3

[0032] A high-iron diaspore type bauxite (mineral composition same as Example 1), 200 mL of circulating mother liquor and an additive ethylenediamine were prepared into a mixed ore slurry, wherein the Na2O k The concentration of the mixed ore slurry was 280 g / L, the concentration of Al2O3 was 140 g / L, the mass ratio of bauxite to circulating mother liquor was 180 g / L, and the mass ratio of additive to circulating mother liquor was 3 g / L. After pre-reaction of the mixed ore slurry at 95 ℃ for 180 min, the temperature was raised to 270 ℃ for leaching reaction for 75 min, and a leaching slurry and a leaching residue were obtained. The leaching residue obtained under this condition was subjected to magnetic separation under a magnetic field intensity of 160 kA / m, and the mass percentage of total iron (calculated as Fe2O3) in the obtained iron concentrate was 78.22%, the mass percentage of silicon impurities (calculated as SiO2) was 4.17%, and the recovery rate of iron in the bauxite was 71.41%. The relative leaching rate of alumina was 98.22%. After dilution of the leaching slurry, the obtained filtrate was added with seed crystals to promote the decomposition of sodium aluminate in the solution to form aluminum hydroxide, and after solid-liquid separation again, aluminum hydroxide solid was obtained, which was further calcined to obtain alumina product, and the liquid was returned to the leaching process for continuous use. The obtained alumina product meets the GB / T 24487-2022 standard.

[0033] Comparative Example 1

[0034] This comparative example is compared with Example 2, and the additive choline is replaced with an equal amount of glucose, and the rest is the same.

[0035] The leaching residue obtained under the conditions of this comparative example was subjected to magnetic separation under a magnetic field intensity of 160 kA / m, and the mass percentage of total iron (calculated as Fe2O3) in the obtained iron concentrate was 62.12%, the mass percentage of silicon impurities (calculated as SiO2) was 12.15%, and the recovery rate of iron in the bauxite was 58.22%. The leaching rate of alumina was 96.18%. After dilution of the leaching slurry, the obtained filtrate was added with seed crystals to promote the decomposition of sodium aluminate in the solution to form aluminum hydroxide, and after solid-liquid separation again, aluminum hydroxide solid was obtained, which was further calcined to obtain alumina product, and the liquid was returned to the leaching process for continuous use. The obtained alumina product does not meet the requirements of the GB / T 24487-2022 standard.

[0036] Comparative Example 2

[0037] This comparative example is compared with Example 2, and the additive choline is replaced with an equal amount of kerosene, and the rest is the same.

[0038] The leaching residue obtained under the conditions of the present comparative example was subjected to magnetic separation at a magnetic field strength of 160 kA / m, and the total iron (calculated as Fe2O3) mass percentage of the iron concentrate obtained was 66.98%, the silicon impurity (calculated as SiO2) mass percentage was 10.28%, and the iron recovery rate in the bauxite was 62.33%. The leaching rate of aluminum oxide was 97.11%. After dilution of the leaching slurry, the obtained filtrate was added with seed crystals to promote the decomposition of sodium aluminate in the solution to form aluminum hydroxide, and after the second solid-liquid separation, aluminum hydroxide solids were obtained, which were further calcined to obtain aluminum oxide products, and the liquid was returned to the leaching process for continuous use. The obtained aluminum oxide products did not meet the requirements of GB / T24487-2022 standard.

[0039] From the results of Examples 1-3 and Comparative Examples 1-2 above, it can be seen that, compared with long-chain carbon organic matters such as glucose and kerosene, the use of choline, triethanolamine or ethylenediamine as a leaching additive for bauxite can significantly promote the reduction of iron minerals in the ore and the dispersion and dissociation of silicon mineral impurities, improve the iron recovery rate of bauxite, and reduce the silicon impurity content in the obtained iron concentrate. Among them, the leaching effect of choline as an additive is further significantly improved. And the quality of the obtained aluminum oxide products is higher, which can meet the requirements of GB / T 24487-2022 standard.

[0040] Example 4

[0041] A high-iron diaspore-type bauxite (mineral composition: Al2O357.20%, Fe2O324.33%, SiO212.34%) was prepared into a mixed ore slurry with 200 mL of circulating mother liquor and an additive diethylenetriamine, wherein the Na2O k concentration was 260 g / L, the Al2O3 concentration was 126 g / L, the mass ratio of bauxite to circulating mother liquor was 360 g / L, and the mass ratio of additive to circulating mother liquor was 10 g / L; the mixed ore slurry was subjected to leaching reaction at 280°C for 90 min to obtain a leaching slurry and a leaching residue. The leaching residue obtained under the above conditions was subjected to magnetic separation at a magnetic field strength of 160 kA / m, and the total iron (calculated as Fe2O3) mass percentage of the iron concentrate obtained was 78.12%, the silicon impurity (calculated as SiO2) mass percentage was 3.68%, and the iron recovery rate in the bauxite was 69.88%. The relative leaching rate of aluminum oxide was 97.57%. After dilution of the leaching slurry, the obtained filtrate was added with seed crystals to promote the decomposition of sodium aluminate in the solution to form aluminum hydroxide, and after the second solid-liquid separation, aluminum hydroxide solids were obtained, which were further calcined to obtain aluminum oxide products, and the liquid was returned to the leaching process for continuous use. The obtained aluminum oxide products met the GB / T24487-2022 standard.

[0042] Comparative Example 3

[0043] The comparative example is compared with example 4, glycerol is used to replace the same amount of additive diethylene triamine, and the rest is the same.

[0044] The leaching residue obtained under the conditions of the comparative example is subjected to magnetic separation under a magnetic field strength of 160 kA / m, the mass percentage of total iron (calculated as Fe2O3) of the obtained iron concentrate is 75.12%, the mass percentage of silicon impurities (calculated as SiO2) is 8.21%, and the iron recovery rate in bauxite is 69.22%. The relative leaching rate of aluminum oxide is 95.82%. After dilution of the leaching slurry, fine filtration treatment is performed, the obtained filtrate is added with seed crystals to promote the decomposition of sodium aluminate in the solution to generate aluminum hydroxide, after solid-liquid separation again, aluminum hydroxide solid is obtained, further calcination obtains aluminum oxide product, and the liquid is returned to the leaching process for continuous use. The obtained aluminum oxide product meets the standard of GB / T24487-2022.

[0045] Comparative example 4

[0046] The comparative example is compared with example 4, glycerol is used to replace the same amount of additive diethylene triamine, and the rest is the same.

[0047] The leaching residue obtained under the conditions of the comparative example is subjected to magnetic separation under a magnetic field strength of 160 kA / m, the mass percentage of total iron (calculated as Fe2O3) of the obtained iron concentrate is 75.12%, the mass percentage of silicon impurities (calculated as SiO2) is 8.21%, and the iron recovery rate in bauxite is 69.22%. The relative leaching rate of aluminum oxide is 95.82%. After dilution of the leaching slurry, fine filtration treatment is performed, the obtained filtrate is added with seed crystals to promote the decomposition of sodium aluminate in the solution to generate aluminum hydroxide, after solid-liquid separation again, aluminum hydroxide solid is obtained, further calcination obtains aluminum oxide product, and the liquid is returned to the leaching process for continuous use. The obtained aluminum oxide product meets the standard of GB / T24487-2022.

[0048] From the results of examples 1-4 and comparative examples 3-4 above, it can be seen that, compared with glycerol, methanol and other small molecule alcohol organic matters, the bauxite leaching additive choline, triethanolamine, ethylenediamine or diethylene triamine can significantly promote the reduction of iron minerals in the ore and the dispersion and dissociation of silicon mineral impurities, improve the iron recovery rate of bauxite, and reduce the silicon impurity content in the obtained iron concentrate.

[0049] Example 5

[0050] High-iron diaspore type bauxite (mineral composition: Al2O3 63.22%, Fe2O3 20.31%, SiO2 11.13%), 200 mL of circulating mother liquor and additive acetic acid are prepared into a mixed ore slurry, wherein in the circulating mother liquor: Na2O kThe bauxite is added in a mass ratio of 220 g / L to the volume of the circulating mother liquor, and the additive is added in a mass ratio of 30 g / L to the volume of the circulating mother liquor; the mixed ore slurry is heated to 260 °C for leaching reaction for 90 min to obtain a leaching slurry and a leaching residue. The leaching residue obtained under the above conditions is subjected to magnetic separation under a magnetic field strength of 160 kA / m, and the total iron (calculated as Fe2O3) mass percentage of the obtained iron concentrate is 73.12%, the silicon impurity (calculated as SiO2) mass percentage is 5.01%, and the iron recovery rate in the bauxite is 67.64%. The leaching rate of aluminum oxide is 95.88%. The leaching slurry is diluted and subjected to precision filtration treatment, the obtained filtrate is added with a seed crystal to promote the decomposition of sodium aluminate in the solution to generate aluminum hydroxide, and after the second solid-liquid separation, aluminum hydroxide solid is obtained, which is further calcined to obtain an aluminum oxide product, and the liquid is returned to the leaching process for continuous use. The obtained aluminum oxide product meets the GB / T 24487-2022 standard.

[0051] Example 6

[0052] A high-iron diaspore type bauxite (with the same mineral composition as in Example 5), 200 mL of a circulating mother liquor, and the additive glycine are prepared into a mixed ore slurry, wherein the Na2O k The bauxite is added in a mass ratio of 300 g / L to the volume of the circulating mother liquor, and the additive is added in a mass ratio of 3 g / L to the volume of the circulating mother liquor; the mixed ore slurry is heated to 270 °C for leaching reaction for 80 min to obtain a leaching slurry and a leaching residue. The leaching residue obtained under the above conditions is subjected to magnetic separation under a magnetic field strength of 160 kA / m, and the total iron (calculated as Fe2O3) mass percentage of the obtained iron concentrate is 77.16%, the silicon impurity (calculated as SiO2) mass percentage is 4.22%, and the iron recovery rate in the bauxite is 69.01%. The leaching rate of aluminum oxide is 98.95%. The leaching slurry is diluted and subjected to precision filtration treatment, the obtained filtrate is added with a seed crystal to promote the decomposition of sodium aluminate in the solution to generate aluminum hydroxide, and after the second solid-liquid separation, aluminum hydroxide solid is obtained, which is further calcined to obtain an aluminum oxide product, and the liquid is returned to the leaching process for continuous use. The obtained aluminum oxide product meets the GB / T 24487-2022 standard.

[0053] The above examples are preferred embodiments of the present application, but the embodiments of the present application are not limited to the above examples, and any changes, modifications, substitutions, combinations, simplifications made without departing from the spirit and principles of the present application shall be equivalent replacement modes and shall be included in the protection scope of the present application.

Claims

1. A method for leaching and iron recovery of high-iron diaspore type bauxite, characterized by, The method comprises the following steps: (1) preparing a mixed ore slurry by mixing high-iron diaspore bauxite, sodium aluminate circulating mother liquor and an additive; the additive is one of choline, diethylene triamine and glycine; (2) heating the mixed ore slurry obtained in step (1) to 190-280 DEG C to perform a leaching reaction, obtaining a leaching slurry and a leaching residue, and recovering iron concentrate by magnetic separation of the leaching residue; The high-iron diaspore bauxite in step (1) refers to a bauxite with a mass percentage of iron mineral content of >15% in the form of Fe2O3, including diaspore hard bauxite and diaspore soft bauxite; Na2O of the sodium aluminate circulating mother liquor k concentration of 160-280 g / L, Al2O3 concentration of 75-140 g / L; The mass ratio of the high-iron diaspore bauxite to the sodium aluminate circulating mother liquor is 130-360 g / L; The mass ratio of the additive to the circulating mother liquor is 0.5-50 g / L.

2. The method of claim 1, wherein the method is characterized by, The leaching reaction in step (2) refers to pre-reaction at 90-120 DEG C for 90-210 min, and then reaction at 190-280 DEG C for 30-90 min.

3. The method of claim 1, wherein the method is characterized by, The leaching slurry in step (2) is diluted and then subjected to precision filtration treatment, the obtained filtrate is added with seed crystals to promote the decomposition of sodium aluminate in the solution to generate aluminum hydroxide, and then aluminum hydroxide solid is obtained by solid-liquid separation again, further calcination of the aluminum hydroxide solid obtains an aluminum oxide product, and the liquid is returned to the leaching process for continuous use.