A method for extracting chromium from chromium-containing materials by liquid-phase oxidation

Abstract

The present invention provides a method for extracting chromium by liquid-phase oxidation of a chromium-containing material, the method comprising the following steps: (1) mixing the chromium-containing material, an alkali, and an additive, and then roasting to obtain a roasted clinker; the additive comprising the following elements: Cr, Fe, Si, and C; and (2) mixing a solvent and the roasted clinker obtained in step (1), heating the mixture, and introducing an oxidizing gas to react to obtain a mixed slurry. By adding specific additives and subjecting the chromium-containing material to a low-temperature roasting treatment, the present invention can significantly accelerate the reaction rate of chromium extraction by liquid-phase oxidation, improve the chromium conversion rate, reduce the reaction temperature of the liquid-phase oxidation, shorten the reaction time of the liquid-phase oxidation, and reduce the chromium content in the tailings. Simultaneously, the resource utilization of ferrochrome alloy and slag is achieved, thereby reducing production costs.

Description

Technical Field

[0001] The invention belongs to the technical field of chromium salt production and waste residue utilization, and relates to a method for extracting chromium through liquid-phase oxidation of chromium-containing materials. Background Art

[0002] Chromium, a key strategic metal resource, is widely used in steel, metallurgy, chemicals, pharmaceuticals, aerospace, and other fields. In recent years, with the continuous development of the economy, the demand for chromium resources has also increased. Chromite, as the most valuable chromium-containing mineral, is the primary raw material for the production of chromium and chromium salts. However, the utilization rate of chromium resources in the production of chromium salts is low, and the hexavalent chromium produced is extremely harmful to humans and the environment. Therefore, fully utilizing the chromium in chromite and addressing the pollution issues in its production process have become urgent issues.

[0003] In recent years, various liquid-phase chromite oxidation processes have been developed based on the characteristics of the raw materials used to utilize chromium-containing minerals such as chromite and produce chromium salts. CN1226512A discloses a clean production method for sodium chromate, which involves oxidative decomposition of chromite using a molten salt medium containing NaOH at a reaction temperature of 500-550°C, with the product leached in a high-alkalinity region. The hexavalent chromium leachate is then cooled and crystallized to produce coarse mixed sodium chromate and sodium aluminate crystals and a crystallization mother liquor. The coarse crystals are then countercurrently washed and purified to obtain purified sodium chromate crystals and a coarse crystal washing liquor. The coarse crystal washing liquor is then subjected to alkalinity adjustment and crystallization to separate the sodium aluminate. However, this method suffers from high reaction temperatures, direct cooling and crystallization using a highly concentrated leachate, resulting in high solution viscosity and difficulty in solid-liquid separation. Furthermore, the high-temperature, high-alkaline environment causes severe equipment corrosion. The mixed crystals require further separation, leading to a lengthy industrial process.

[0004] CN101481144A discloses a clean production method for preparing potassium chromate from chromite. The chromite is oxidized and decomposed in a KOH-KNO3-H2O medium at a certain temperature using an oxidant. At this temperature, the KNO3 does not act as an oxidant but rather as a reaction medium and can be recycled. The oxidant is oxygen, a gas with a certain oxygen partial pressure, or a peroxide. However, this method has a long production process.

[0005] CN109399716A discloses a method for extracting chromium from chromium-containing materials by liquid-phase oxidation. The method comprises the steps of extracting chromium by liquid-phase oxidation using chromium-containing materials and alkali as raw materials. The raw materials also include additives, wherein the additives include transition metal compounds, and the additives are selected from black slag and / or chromium-containing waste catalysts. The black slag is chromium slag with a Cr2O3 content of greater than 15wt% obtained by sorting leached slag from liquid-phase oxidation for chromium extraction. The purpose of introducing the transition metal compound in this method is to improve the conversion rate of chromium in the chromium-containing material, but this will result in a high impurity content in the product and a complex tailings composition.

[0006] In summary, for the method of extracting chromium by liquid-phase oxidation of chromium-containing materials, it is necessary to develop a new additive and a pretreatment method for chromium-containing materials to enhance the liquid-phase oxidation process, improve the conversion rate of chromium during the liquid-phase oxidation of chromium-containing materials, reduce temperature and pressure, and at the same time reduce the content of impurities such as silicon and aluminum in the leachate, reduce waste residue emissions, and thus reduce energy consumption and production costs. Summary of the Invention

[0007] The object of the present invention is to provide a method for extracting chromium from chromium-containing materials by liquid-phase oxidation. By adding specific additives and subjecting the chromium-containing materials to low-temperature calcination, the reaction rate of liquid-phase oxidation for extracting chromium can be significantly accelerated, the conversion rate of chromium can be improved, the reaction temperature of the liquid-phase oxidation can be reduced, the reaction time of the liquid-phase oxidation can be shortened, and the chromium content in the tailings can be reduced. At the same time, the resource utilization of ferrochrome alloy and slag can be achieved, and the production cost can be reduced.

[0008] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0009] The present invention provides a method for extracting chromium by liquid-phase oxidation of a chromium-containing material, the method comprising the following steps:

[0010] (1) mixing a chromium-containing material, an alkali, and an additive and then roasting the mixture to obtain a roasted clinker;

[0011] The additives include the following elements: Cr, Fe, Si, C;

[0012] (2) The solvent and the calcined clinker of step (1) are mixed and heated, and an oxidizing gas is introduced to obtain a mixed slurry after reaction.

[0013] The method for extracting chromium from chromium-containing materials by liquid-phase oxidation provided by the present invention can significantly accelerate the reaction rate of liquid-phase oxidation to extract chromium, improve the conversion rate of chromium, reduce the reaction temperature of liquid-phase oxidation, shorten the reaction time of liquid-phase oxidation, reduce the chromium content in the tailings, and simultaneously realize the resource utilization of chromium in the additive, reduce production costs, and have good economic benefits, by adding specific additives and performing low-temperature roasting pretreatment on the mixed materials.

[0014] It is worth noting that the additive used in the present invention has the following functions: first, it can realize the resource utilization of chromium in the additive and reduce the existing storage volume of waste slag; second, the iron element in the additive is more likely to generate ferrate with higher oxidizability, which helps to destroy the internal structure of the chromium-containing material during the liquid-phase oxidation process and realize low-temperature and low-pressure leaching; third, the carbon in the additive has a higher calorific value, which can achieve a better activation effect on the chromium-containing material at a lower temperature, and at the same time helps to increase the porosity of the material, thereby improving the transportation efficiency of the oxygen-containing gas and realizing efficient extraction of chromium during liquid-phase oxidation chromium extraction; fourth, the silicon in the additive generates sodium aluminosilicate precipitate with aluminum in the chromite under alkaline roasting conditions, thereby reducing the impurity aluminum content in the solution.

[0015] As a preferred technical solution of the present invention, the chromium-containing material in step (1) includes chromite and / or chromium slag.

[0016] In the present invention, the chromite and chromium slag both contain a certain content of Cr2O3.

[0017] Preferably, the average particle size of the chromium-containing material in step (1) is ≤74 μm, for example, it can be 72 μm, 70 μm, 68 μm, 65 μm, 60 μm, 55 μm, 50 μm or 40 μm, etc., but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0018] As a preferred technical solution of the present invention, the base in step (1) includes sodium hydroxide and / or potassium hydroxide, preferably sodium hydroxide.

[0019] Preferably, the amount of alkali added in step (1) is 0.5 to 3 times the mass of the alkali consumed when all chromium in the chromium-containing material and additive is converted into sodium chromate, for example, it can be 0.6 times, 0.8 times, 1 time, 1.2 times, 1.5 times, 1.8 times, 2 times, 2.2 times, 2.5 times or 2.8 times, etc., but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0020] In the present invention, the amount of base added is the theoretical consumption.

[0021] As a preferred technical solution of the present invention, the additive in step (1) includes the following elements in terms of mass content: Cr: 30wt.%~60wt.%, Fe: 10wt.%~30wt.%, Si: 1wt.%~20wt.%, C: 5wt.%~30wt.%, and the remainder is O and unavoidable impurities.

[0022] In the present invention, the additive contains 30 wt.% to 60 wt.% of Cr element, for example, 32 wt.%, 35 wt.%, 38 wt.%, 40 wt.%, 42 wt.%, 45 wt.%, 48 wt.%, 50 wt.%, 52 wt.%, 55 wt.% or 58 wt.%, and the additive contains 10 wt.% to 30 wt.% of Fe element, for example, 12 wt.%, 15 wt.%, 18 wt.%, 20 wt.%, 22 wt.%, 25 wt.% or 28 wt.%, etc. The additive contains 1 wt.% to 20 wt.% of Si element, for example, it can be 2 wt.%, 5 wt.%, 8 wt.%, 10 wt.%, 12 wt.%, 15 wt.% or 18 wt.%, and the additive contains 5 wt.% to 30 wt.% of C element, for example, it can be 8 wt.%, 10 wt.%, 12 wt.%, 15 wt.%, 18 wt.%, 20 wt.%, 22 wt.%, 25 wt.% or 28 wt.%, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0023] Preferably, the additive in step (1) includes the following elements by mass content: Cr: 30wt.% to 55wt.%, Fe: 10wt.% to 30wt.%, Si: 5wt.% to 20wt.%, C: 5wt.% to 24wt.%, and the remainder is O and unavoidable impurities.

[0024] Preferably, the additive in step (1) comprises any one of ferrochrome, ferrochrome acid leaching residue or ferrochrome chlorination decomposition residue, or a combination of at least two of them, wherein the combinations are typically but not limited to: a combination of ferrochrome and ferrochrome acid leaching residue, a combination of ferrochrome acid leaching residue and ferrochrome chlorination decomposition residue, or a combination of ferrochrome, ferrochrome acid leaching residue and ferrochrome chlorination decomposition residue, etc.

[0025] In the present invention, ferrochrome, ferrochrome acid leaching residue or ferrochrome chlorination decomposition residue is selected as an additive, so that chromium in the ferrochrome or its leaching residue is fully extracted, the reaction rate and conversion rate of chromium extraction by liquid phase oxidation are improved, the reaction temperature of liquid phase oxidation is reduced, and the reaction time of liquid phase oxidation is shortened.

[0026] Preferably, the mass ratio of the additive to the chromium-containing material in step (1) is (0.2-3):1, for example, it can be 0.3:1, 0.4:1, 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1, 1:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1, 1.5:1, 1.6:1, 1.7:1, 1.8:1, 2:1, 2.2:1, 2.4:1, 2.5:1, 2.6:1, 2.8:1 or 2.9:1, but is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable, preferably (0.5-2):1.

[0027] Preferably, the average particle size of the additive in step (1) is ≤74 μm, for example, it can be 72 μm, 70 μm, 68 μm, 65 μm, 60 μm, 55 μm, 50 μm or 40 μm, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0028] As a preferred technical solution of the present invention, the calcination temperature in step (1) is 100-500°C, for example, it can be 150°C, 200°C, 250°C, 300°C, 350°C, 400°C, 450°C or 480°C, but is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable, preferably 200-400°C.

[0029] Preferably, the calcination time in step (1) is 10 to 180 min, for example, it can be 20 min, 30 min, 40 min, 50 min, 60 min, 80 min, 100 min, 110 min, 120 min, 140 min, 150 min, 160 min or 180 min, but is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable, preferably 30 to 120 min.

[0030] Preferably, the roasting in step (1) is carried out in air and / or oxygen-rich gas.

[0031] In the present invention, the oxygen-rich gas is an atmosphere in which the volume percentage of oxygen is greater than 20%.

[0032] As a preferred technical solution of the present invention, the solvent in step (2) includes water.

[0033] Preferably, the liquid-solid ratio of the solvent to the roasted clinker in step (2) is (2-15):1 mL / g, for example, it can be 3:1 mL / g, 4:1 mL / g, 5:1 mL / g, 6:1 mL / g, 7:1 mL / g, 8:1 mL / g, 9:1 mL / g, 10:1 mL / g, 12:1 mL / g or 14:1 mL / g, but is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable, preferably (4-10):1 mL / g.

[0034] As a preferred technical solution of the present invention, the heating temperature in step (2) is 100-250°C, for example, it can be 110°C, 120°C, 130°C, 140°C, 150°C, 160°C, 180°C, 200°C, 220°C or 240°C, but is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable, preferably 120-200°C.

[0035] Preferably, the heating time in step (2) is 0.5 to 5 h, for example, 1 h, 1.5 h, 2 h, 2.5 h, 3 h, 3.5 h, 4 h or 4.5 h, but is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable, preferably 1 to 4 h.

[0036] As a preferred technical solution of the present invention, the oxidizing gas in step (2) includes air and / or oxygen, preferably oxygen.

[0037] Preferably, the oxidizing gas in step (2) is introduced continuously.

[0038] Preferably, the oxygen partial pressure during the heating process in step (2) is 0.2 to 6 MPa, for example, 0.5 MPa, 1 MPa, 1.5 MPa, 2 MPa, 2.5 MPa, 3 MPa, 3.5 MPa, 4 MPa or 4.5 MPa, but is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable, preferably 1 to 4 MPa.

[0039] As a preferred technical solution of the present invention, the method further comprises: performing solid-liquid separation on the mixed slurry in step (2) to obtain chromium-containing alkali solution and tailings.

[0040] As a preferred technical solution of the present invention, the method comprises the following steps:

[0041] (1) mixing a chromium-containing material, an alkali, and an additive, and roasting the mixture in air and / or an oxygen-rich gas at a temperature of 100 to 500° C. for 10 to 180 minutes to obtain a roasted clinker;

[0042] The chromium-containing material includes chromite and / or chromium slag; the alkali includes sodium hydroxide and / or potassium hydroxide; the additive includes the following elements by mass: Cr: 30wt.% to 60wt.%, Fe: 10wt.% to 30wt.%, Si: 1wt.% to 20wt.%, C: 5wt.% to 30wt.%, the remainder being O and unavoidable impurities; the additive includes any one or a combination of at least two of ferrochrome, ferrochrome acid leaching residue or ferrochrome chlorination decomposition residue; the amount of the alkali added is 0.5 to 3 times the mass of the alkali consumed when all chromium in the chromium-containing material and the additive is converted into sodium chromate; the mass ratio of the additive to the chromium-containing material is (0.2 to 3):1;

[0043] (2) mixing the solvent and the calcined clinker of step (1) at a liquid-solid ratio of (2-15):1 mL / g, heating at a temperature of 100-250° C. for 0.5-5 h, and continuously introducing an oxidizing gas until the oxygen partial pressure reaches 0.2-6 MPa, obtaining a mixed slurry after the reaction, and then performing solid-liquid separation to obtain a chromium-containing alkali solution and tailings;

[0044] The oxidizing gas includes air and / or oxygen.

[0045] Compared with the prior art, the present invention has the following beneficial effects:

[0046] The method for extracting chromium from chromium-containing materials by liquid-phase oxidation provided by the present invention can significantly accelerate the reaction rate of liquid-phase oxidation to extract chromium, improve the conversion rate of chromium, reduce the reaction temperature of liquid-phase oxidation, shorten the reaction time of liquid-phase oxidation, and reduce the chromium content in tailings by adding specific additives and performing low-temperature roasting pretreatment on the mixed materials. At the same time, the method can realize resource utilization of chromium in the additives, reduce production costs, and have good economic benefits. The chromium conversion rate can reach more than 96%, and the chromium content in the tailings is less than 1.2%. DETAILED DESCRIPTION

[0047] The technical solution of the present invention is further described below by way of specific embodiments. It should be understood by those skilled in the art that the embodiments are merely to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0048] In the following examples and comparative examples, the oxygen-rich gas is a gas having an oxygen volume percentage greater than 20%.

[0049] Example 1

[0050] This embodiment provides a method for extracting chromium from a chromium-containing material by liquid-phase oxidation, the method comprising the following steps:

[0051] (1) mixing chromite, sodium hydroxide and chromium iron acid leaching residue, wherein the average particle size of the mixture is less than 50 μm, and roasting the mixture at 350° C. in an air atmosphere for 60 minutes to obtain roasted clinker;

[0052] The chromite ore has a Cr2O3 content of 43 wt.%. The ferrochrome acid leaching residue comprises the following elements by mass: Cr: 40 wt.%, Fe: 25 wt.%, Si: 9 wt.%, C: 13 wt.%, with the remainder being O and unavoidable impurities. The amount of sodium hydroxide added is twice the mass of the alkali consumed in converting all chromium in the chromite ore and the ferrochrome acid leaching residue into sodium chromate. The mass ratio of the ferrochrome acid leaching residue to the chromite is 0.8:1.

[0053] (2) Deionized water and the calcined clinker of step (1) are stirred and mixed according to a liquid-solid ratio of 8:1 mL / g, heated to a temperature of 150° C., oxygen is continuously introduced until the oxygen partial pressure reaches 3 MPa, and this pressure is maintained for a reaction of 2 h to obtain a mixed slurry, and then the mixed slurry is subjected to solid-liquid separation to obtain chromium-containing alkali solution and tailings.

[0054] Example 2

[0055] This embodiment provides a method for extracting chromium from a chromium-containing material by liquid-phase oxidation, the method comprising the following steps:

[0056] (1) mixing chromium slag, sodium hydroxide and ferrochrome, wherein the average particle size of the mixture is less than 45 μm, and roasting the mixture in an air atmosphere at a temperature of 300° C. for 90 minutes to obtain roasted clinker;

[0057] The chromium slag contains 9 wt.% Cr2O3; the ferrochrome contains the following elements by mass: 53 wt.% Cr, 25 wt.% Fe, 10 wt.% Si, and 6.2 wt.% C, with the remainder being O and unavoidable impurities; the amount of sodium hydroxide added is 1.5 times the mass of the alkali consumed in converting all chromium in the chromium slag and ferrochrome into sodium chromate; the mass ratio of the ferrochrome to the chromium slag is 1:1;

[0058] (2) Deionized water and the calcined clinker of step (1) are stirred and mixed according to a liquid-solid ratio of 10:1 mL / g, heated to a temperature of 180° C., oxygen is continuously introduced until the oxygen partial pressure reaches 3.5 MPa, and this pressure is maintained for a reaction of 3 hours to obtain a mixed slurry, and then the mixed slurry is subjected to solid-liquid separation to obtain chromium-containing alkali liquor and tailings.

[0059] Example 3

[0060] This embodiment provides a method for extracting chromium from a chromium-containing material by liquid-phase oxidation, the method comprising the following steps:

[0061] (1) mixing chromite, sodium hydroxide and ferrochrome acid leaching residue, wherein the average particle size of the mixture is less than 55 μm, and roasting the mixture in an air atmosphere at a temperature of 250° C. for 120 minutes to obtain roasted clinker;

[0062] The chromite ore has a Cr2O3 content of 43 wt.%. The ferrochrome acid leaching residue comprises the following elements by mass: 36 wt.%, 19 wt.%, 17 wt.%, 15 wt.%, and the remainder is O and unavoidable impurities. The amount of sodium hydroxide added is 1.8 times the mass of the alkali consumed in converting all chromium in the chromite ore and the ferrochrome acid leaching residue into sodium chromate. The mass ratio of the ferrochrome acid leaching residue to the chromite is 0.5:1.

[0063] (2) Deionized water and the calcined clinker of step (1) are stirred and mixed according to a liquid-solid ratio of 5:1 mL / g, heated to a temperature of 200° C., oxygen is continuously introduced until the oxygen partial pressure reaches 2.5 MPa, and this pressure is maintained for a reaction of 2 h to obtain a mixed slurry, and then the mixed slurry is subjected to solid-liquid separation to obtain chromium-containing alkali liquor and tailings.

[0064] Example 4

[0065] This embodiment provides a method for extracting chromium from a chromium-containing material by liquid-phase oxidation, the method comprising the following steps:

[0066] (1) mixing chromium slag, sodium hydroxide and ferrochrome acid leaching residue, wherein the average particle size of the mixture is less than 65 μm, and roasting the mixture in an oxygen-rich gas at a temperature of 320° C. for 100 minutes to obtain roasted clinker;

[0067] The chromium slag has a Cr2O3 content of 9 wt.%. The ferrochrome acid leaching residue comprises the following elements by mass: Cr: 45 wt.%, Fe: 29 wt.%, Si: 8 wt.%, C: 9 wt.%, with the remainder being O and unavoidable impurities. The amount of sodium hydroxide added is 2.8 times the mass of alkali consumed in converting all chromium in the chromium slag and the ferrochrome acid leaching residue into sodium chromate. The mass ratio of the ferrochrome acid leaching residue to the chromium slag is 0.9:1.

[0068] (2) Deionized water and the calcined clinker of step (1) are stirred and mixed according to a liquid-solid ratio of 7:1 mL / g, heated to a temperature of 180° C., oxygen is continuously introduced until the oxygen partial pressure reaches 3.6 MPa, and this pressure reaction is maintained for 3.5 hours to obtain a mixed slurry, and then the mixed slurry is subjected to solid-liquid separation to obtain chromium-containing alkali solution and tailings.

[0069] Example 5

[0070] This embodiment provides a method for extracting chromium from a chromium-containing material by liquid-phase oxidation, the method comprising the following steps:

[0071] (1) mixing chromite, sodium hydroxide and chromium chlorination decomposition slag, wherein the average particle size of the mixture is less than 35 μm, and roasting the mixture in an oxygen-rich atmosphere at a temperature of 350° C. for 60 minutes to obtain roasted clinker;

[0072] The chromite ore has a Cr2O3 content of 43 wt.%. The ferrochrome chlorination decomposition slag comprises the following elements by mass: Cr: 38 wt.%, Fe: 17 wt.%, Si: 16 wt.%, C: 21 wt.%, with the remainder being O and unavoidable impurities. The amount of sodium hydroxide added is 1.8 times the mass of the alkali consumed in converting all chromium in the chromite ore and the ferrochrome chlorination decomposition slag into sodium chromate. The mass ratio of the ferrochrome chlorination decomposition slag to the chromite is 1.5:1.

[0073] (2) Deionized water and the calcined clinker of step (1) are stirred and mixed according to a liquid-solid ratio of 4:1 mL / g, heated to a temperature of 120° C., oxygen is continuously introduced until the oxygen partial pressure reaches 4 MPa, and this pressure is maintained for a reaction of 3 hours to obtain a mixed slurry, and then the mixed slurry is subjected to solid-liquid separation to obtain chromium-containing alkali solution and tailings.

[0074] Example 6

[0075] This embodiment provides a method for extracting chromium from a chromium-containing material by liquid-phase oxidation, the method comprising the following steps:

[0076] (1) mixing chromium slag, sodium hydroxide and chromium iron chlorination decomposition slag, wherein the average particle size of the mixture is less than 45 μm, and roasting the mixture at a temperature of 250° C. in an oxygen-rich atmosphere for 120 minutes to obtain roasted clinker;

[0077] The chromium slag has a Cr2O3 content of 9 wt.%. The ferrochrome chlorination decomposition slag comprises the following elements by mass: Cr: 50 wt.%, Fe: 20 wt.%, Si: 10 wt.%, C: 8 wt.%, with the remainder being O and unavoidable impurities. The amount of sodium hydroxide added is 2.6 times the mass of the alkali consumed in converting all chromium in the chromium slag and the ferrochrome chlorination decomposition slag into sodium chromate. The mass ratio of the ferrochrome chlorination decomposition slag to the chromium slag is 0.5:1.

[0078] (2) Deionized water and the calcined clinker of step (1) are stirred and mixed according to a liquid-solid ratio of 9:1 mL / g, heated to a temperature of 150° C., oxygen is continuously introduced until the oxygen partial pressure reaches 3.4 MPa, and this pressure is maintained for a reaction of 3 hours to obtain a mixed slurry, and then the mixed slurry is subjected to solid-liquid separation to obtain chromium-containing alkali solution and tailings.

[0079] Example 7

[0080] This embodiment provides a method for extracting chromium from a chromium-containing material by liquid-phase oxidation, the method comprising the following steps:

[0081] (1) mixing chromite, sodium hydroxide and ferrochrome acid leaching residue, wherein the average particle size of the mixture is less than 38 μm, and roasting the mixture at 400° C. in an air atmosphere for 120 minutes to obtain roasted clinker;

[0082] The chromite ore has a Cr2O3 content of 43 wt.%. The ferrochrome acid leaching residue comprises the following elements by mass: Cr: 31 wt.%, Fe: 12 wt.%, Si: 13 wt.%, C: 11 wt.%, with the remainder being O and unavoidable impurities. The amount of sodium hydroxide added is 2.5 times the mass of alkali consumed in converting all chromium in the chromite ore and the ferrochrome acid leaching residue into sodium chromate. The mass ratio of the ferrochrome acid leaching residue to the chromite is 1.8:1.

[0083] (2) Deionized water and the calcined clinker of step (1) are stirred and mixed according to a liquid-solid ratio of 8:1 mL / g, heated to a temperature of 200° C., oxygen is continuously introduced until the oxygen partial pressure reaches 4 MPa, and this pressure reaction is maintained for 4 hours to obtain a mixed slurry, and then the mixed slurry is subjected to solid-liquid separation to obtain chromium-containing alkali solution and tailings.

[0084] Example 8

[0085] This embodiment provides a method for extracting chromium from a chromium-containing material by liquid-phase oxidation, the method comprising the following steps:

[0086] (1) mixing chromium slag, sodium hydroxide and ferrochrome acid leaching residue, wherein the average particle size of the mixture is less than 74 μm, and roasting the mixture at a temperature of 250° C. in an air atmosphere for 60 minutes to obtain roasted clinker;

[0087] The chromium slag has a Cr2O3 content of 9 wt.%. The ferrochrome acid leaching residue comprises the following elements by mass: 32 wt.%, Cr, 27 wt.%, Fe, 12 wt.%, Si, 10 wt.%, and C, with the remainder being O and unavoidable impurities. The amount of sodium hydroxide added is three times the mass of the alkali consumed in converting all chromium in the chromium slag and the ferrochrome acid leaching residue into sodium chromate. The mass ratio of the ferrochrome acid leaching residue to the chromium slag is 2:1.

[0088] (2) Deionized water and the calcined clinker of step (1) are stirred and mixed according to a liquid-solid ratio of 5:1 mL / g, heated to a temperature of 120° C., oxygen is continuously introduced until the oxygen partial pressure reaches 3 MPa, and this pressure is maintained for a reaction of 4 hours to obtain a mixed slurry, and then the mixed slurry is subjected to solid-liquid separation to obtain chromium-containing alkali solution and tailings.

[0089] Example 9

[0090] This embodiment provides a method for extracting chromium from a chromium-containing material by liquid-phase oxidation, except that the ferrochromium acid leaching residue in step (1) includes the following elements by mass content: Cr: 40 wt.%, Fe: 5 wt.%, Si: 9 wt.%, C: 13 wt.%, and the balance is O and unavoidable impurities; other conditions are the same as those in Example 1.

[0091] Example 10

[0092] This embodiment provides a method for extracting chromium from a chromium-containing material by liquid-phase oxidation, except that the ferrochromium acid leaching residue in step (1) includes the following elements by mass content: Cr: 40 wt.%, Fe: 25 wt.%, Si: 9 wt.%, C: 2 wt.%, and the balance is O and unavoidable impurities; other conditions are the same as those in Example 1.

[0093] Example 11

[0094] This embodiment provides a method for extracting chromium from a chromium-containing material by liquid-phase oxidation, except that the mass ratio of the ferrochromium acid leaching residue to the chromite ore in step (1) is 3.5:1; other conditions are the same as those in Example 1.

[0095] Comparative Example 1

[0096] This comparative example provides a method for extracting chromium by liquid-phase oxidation of a chromium-containing material. Except that no ferrochromium acid leaching residue is added in step (1), other conditions are the same as those in Example 1.

[0097] Comparative Example 2

[0098] This comparative example provides a method for extracting chromium from a chromium-containing material by liquid-phase oxidation. Except that roasting is not performed in step (1), other conditions are the same as those in Example 1.

[0099] The conversion rate of chromium in the chromium-containing alkali solution obtained in step (2) of the above embodiment and comparative example and the chromium content in the tailings were tested respectively, wherein the chromium content (in terms of Cr2O3) was detected by ICP. The results are shown in Table 1.

[0100] Table 1

[0101]

[0102] From Table 1 we can see that:

[0103] (1) The methods for extracting chromium from chromium-containing materials by liquid-phase oxidation provided in Examples 1-8 of the present invention, by adding specific additives and pre-treating the mixture by low-temperature roasting, can significantly accelerate the reaction rate of chromium extraction by liquid-phase oxidation, improve the conversion rate of chromium, reduce the reaction temperature of liquid-phase oxidation, shorten the reaction time of liquid-phase oxidation, and simultaneously reduce the chromium content in the tailings; wherein the chromium conversion rate is greater than 96%, and the chromium content in the tailings is less than 1.2%;

[0104] (2) From the comparison between Example 1 and Examples 9-10, it can be seen that when the Fe content in the additive is low, it is not conducive to the leaching of chromium from the chromium-containing material during the liquid phase oxidation process; when the C content in the additive is low, it is not conducive to improving the porosity of the material, and thus cannot improve the transport efficiency of the oxygen-containing gas, resulting in a slight decrease in the conversion rate of chromium;

[0105] (3) A comparison of Example 1 and Example 11 shows that when the amount of additives used is too much, part of the additives cannot function due to the large amount of additives added, the chromium extraction rate is not further improved, and the chromium content in the slag is increased;

[0106] (4) From the comparison between Example 1 and Comparative Examples 1-2, it can be seen that when no additives are added or the mixed material is not subjected to low-temperature calcination treatment, the reaction rate of liquid-phase oxidation chromium extraction will be prolonged, which is not conducive to the efficient extraction and recovery of chromium from the chromium-containing material, resulting in a decrease in the chromium conversion rate and an increase in the chromium content in the tailings.

[0107] The applicant declares that the present invention is intended to illustrate the detailed structural features of the present invention through the above-described embodiments, but the present invention is not limited to the above-described detailed structural features. This does not mean that the present invention must rely on the above-described detailed structural features in order to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent replacements for selected components, additions of auxiliary components, and selection of specific embodiments, etc., fall within the scope of protection and disclosure of the present invention.

Claims

1. A method for extracting chromium from chromium-containing materials by liquid phase oxidation, characterized in that: The method comprises the following steps: (1) mixing a chromium-containing material, an alkali, and an additive and then roasting the mixture to obtain a roasted clinker; The additive comprises the following elements by mass content: Cr: 30wt.%~60wt.%, Fe: 10wt.%~30wt.%, Si: 1wt.%~20wt.%, C: 5wt.%~30wt.%, and the balance is O and unavoidable impurities; the mass ratio of the additive to the chromium-containing material is (0.2~3):1; The calcination temperature is 100-500°C; (2) The solvent and the clinker calcined in step (1) are mixed and heated, and an oxidizing gas is introduced to obtain a mixed slurry after reaction.

2. The method according to claim 1, characterized in that The chromium-containing material in step (1) includes chromite and / or chromium slag.

3. The method according to claim 1, characterized in that The average particle size of the chromium-containing material in step (1) is ≤74 μm.

4. The method according to claim 1, wherein The alkali in step (1) includes sodium hydroxide and / or potassium hydroxide.

5. The method according to claim 1, wherein The base in step (1) is sodium hydroxide.

6. The method according to claim 1, characterized in that The amount of alkali added in step (1) is 0.5 to 3 times the mass of the alkali consumed when all chromium in the chromium-containing material and additive is converted into sodium chromate.

7. The method according to claim 1, characterized in that The additives in step (1) include the following elements by mass content: Cr: 30wt.%~55wt.%, Fe: 10wt.%~30wt.%, Si: 5wt.%~20wt.%, C: 5wt.%~24wt.%, and the balance is O and unavoidable impurities.

8. The method according to claim 1, characterized in that The additive in step (1) comprises any one of ferrochrome, ferrochrome acid leaching residue or ferrochrome chlorination decomposition residue, or a combination of at least two of them.

9. The method according to claim 1, characterized in that The mass ratio of the additive to the chromium-containing material in step (1) is (0.5~2):

1.

10. The method according to claim 1, characterized in that The average particle size of the additive in step (1) is ≤74 μm.

11. The method according to claim 1, wherein The calcination temperature in step (1) is 200-400°C.

12. The method according to claim 1, characterized in that The calcination time in step (1) is 10 to 180 minutes.

13. The method according to claim 12, characterized in that The calcination time in step (1) is 30 to 120 minutes.

14. The method according to claim 1, wherein The calcination in step (1) is carried out in air and / or oxygen-rich gas.

15. The method according to claim 1, wherein The solvent in step (2) includes water.

16. The method according to claim 1, wherein The liquid-to-solid ratio of the solvent to the roasted clinker in step (2) is (2-15):1 mL / g.

17. The method according to claim 16, characterized in that The liquid-to-solid ratio of the solvent to the roasted clinker in step (2) is (4-10):1 mL / g.

18. The method according to claim 1, wherein The heating temperature in step (2) is 100-250°C.

19. The method according to claim 18, characterized in that The heating temperature in step (2) is 120-200°C.

20. The method according to claim 1, wherein The heating time in step (2) is 0.5 to 5 hours.

21. The method according to claim 20, characterized in that The heating time in step (2) is 1 to 4 hours.

22. The method according to claim 1, wherein The oxidizing gas in step (2) includes air and / or oxygen.

23. The method according to claim 22, characterized in that The oxidizing gas in step (2) is oxygen.

24. The method according to claim 1, wherein The oxidizing gas in step (2) is introduced continuously.

25. The method according to claim 1, wherein The oxygen partial pressure during the heating process of step (2) is 0.2~6MPa.

26. The method according to claim 25, characterized in that The oxygen partial pressure during the heating process of step (2) is 1~4MPa.

27. The method according to claim 1, wherein The method further comprises: performing solid-liquid separation on the mixed slurry in step (2) to obtain chromium-containing alkali solution and tailings.

28. The method according to claim 1, wherein The method comprises the following steps: (1) mixing a chromium-containing material, an alkali and an additive, and roasting the mixture in air and / or an oxygen-rich gas at a temperature of 100 to 500° C. for 10 to 180 minutes to obtain a roasted clinker; The chromium-containing material includes chromite and / or chromium slag; the alkali includes sodium hydroxide and / or potassium hydroxide; the additive includes the following elements by mass content: Cr: 30wt.%~60wt.%, Fe: 10wt.%~30wt.%, Si: 1wt.%~20wt.%, C: 5wt.%~30wt.%, the remainder being O and inevitable impurities; the additive includes any one or a combination of at least two of ferrochrome, ferrochrome acid leaching residue or ferrochrome chlorination decomposition residue; the amount of the alkali added is 0.5~3 times the mass of the alkali consumed when all chromium in the chromium-containing material and the additive is converted into sodium chromate; the mass ratio of the additive to the chromium-containing material is (0.2~3):1; (2) mixing the solvent and the clinker calcined in step (1) at a liquid-solid ratio of (2-15):1 mL / g, heating at a temperature of 100-250° C. for 0.5-5 h, and continuously introducing an oxidizing gas until the oxygen partial pressure reaches 0.2-6 MPa, obtaining a mixed slurry after the reaction, and then performing solid-liquid separation to obtain a chromium-containing alkali solution and tailings; The oxidizing gas includes air and / or oxygen.

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