阅读说明：本技术 一种含铬物料液相氧化提铬的方法 (Method for extracting chromium from chromium-containing material by liquid-phase oxidation ) 是由 刘宏辉 蔡再华 李双 程西川 张红玲 叶文进 高增礼 陈小红 王明华 段静 徐红 于 2021-09-23 设计创作，主要内容包括：本发明提供了一种含铬物料液相氧化提铬的方法,所述方法包括以下步骤：将含铬物料、苛性碱溶液和含钙化合物混合后加热,并通入氧化性气体,反应后得到混合浆料；将混合浆料进行固液分离,得到含铬碱液和反应尾渣。本发明所述方法在含铬物料提铬过程中添加含钙化合物,可与硅、铝等杂质的阴离子生成相应的沉淀,从源头将硅、铝杂质固定于尾渣中,降低浸出液中硅、铝杂质的含量,减轻除杂工序的负荷；含钙化合物可促进铬铁尖晶石的分解,保证铬具有较高的浸出率；含钙化合物可改善置换浸出渣中碱的反应动力学条件,降低浸出渣中的碱含量,并减少碱的耗量；所述方法操作简单,效果显著,可有效降低成本,具有较好的经济效益。(The invention provides a method for extracting chromium from a chromium-containing material by liquid-phase oxidation, which comprises the following steps: mixing a chromium-containing material, a caustic alkali solution and a calcium-containing compound, heating, introducing an oxidizing gas, and reacting to obtain a mixed slurry; and carrying out solid-liquid separation on the mixed slurry to obtain chromium-containing alkali liquor and reaction tailings. According to the method, the calcium-containing compound is added in the chromium extraction process of the chromium-containing material, and can generate corresponding precipitates with anions of impurities such as silicon, aluminum and the like, so that the impurities of silicon and aluminum are fixed in the tailings from the source, the content of the impurities of silicon and aluminum in the leachate is reduced, and the load of an impurity removal process is reduced; the calcium-containing compound can promote the decomposition of the ferrochrome spinel and ensure that the chromium has higher leaching rate; the calcium-containing compound can improve the reaction kinetic condition for replacing alkali in the leaching residue, reduce the alkali content in the leaching residue and reduce the consumption of the alkali; the method is simple to operate, has obvious effect, can effectively reduce the cost and has better economic benefit.)

1. A method for extracting chromium from chromium-containing materials through liquid-phase oxidation is characterized by comprising the following steps:

(1) mixing a chromium-containing material, a caustic alkali solution and a calcium-containing compound, heating, introducing an oxidizing gas, and reacting to obtain a mixed slurry;

(2) and (2) carrying out solid-liquid separation on the mixed slurry obtained in the step (1) to obtain chromium-containing alkali liquor and reaction tailings.

2. The method of claim 1, wherein the chromium-containing material of step (1) comprises any one of chromite, chromium slag, chromium mud, chromium-containing dust, or tannery ash, or a combination of at least two thereof;

preferably, 90% of the particles in the chromium containing feed of step (1) have a particle size of less than 0.15mm, preferably less than 0.075 mm;

preferably, the caustic solution of step (1) comprises a NaOH solution and/or a KOH solution, preferably a NaOH solution;

preferably, the concentration of the caustic alkali solution in the step (1) is 15 to 80 wt%, preferably 30 to 70 wt%, and more preferably 40 to 60 wt%.

3. The method of claim 1 or 2, wherein the calcium-containing compound of step (1) comprises Ca (OH)₂、CaO、Ca(NO₃)₂、CaSO₄Or CaCl₂Preferably CaO and/or Ca (OH)₂；

Preferably, the calcium-containing compound of step (1) is added in the form of a solid, an aqueous solution, a mixed slurry or a mixed slag containing the calcium-containing compound.

4. The method according to any one of claims 1 to 3, wherein the mass ratio of caustic to chromium-containing material in the caustic solution of step (1) is (0.5-10): 1, preferably (2-8): 1;

preferably, the addition amount of the calcium-containing compound in the step (1) accounts for 0.1-20.0 wt% of the mass of the chromium-containing material, and preferably 0.5-15.0 wt%.

5. The process according to any one of claims 1 to 4, wherein the oxidizing gas of step (1) comprises air and/or oxygen, preferably oxygen;

preferably, the oxidizing gas is continuously introduced in the step (1);

preferably, the mixed material in the step (1) is added into a reaction device, and the reaction device is sealed and then is filled with oxidizing gas.

6. The process according to any one of claims 1 to 5, wherein the heating of step (1) is carried out to a reaction temperature of 150 to 300 ℃, preferably 180 to 280 ℃;

preferably, the reaction time in the step (1) is 0.5-8 h, preferably 2-6 h;

preferably, the oxygen partial pressure of the reaction in the step (1) is 0.2-10.0 MPa, preferably 2.0-6.0 MPa.

7. The method according to any one of claims 1 to 6, wherein after the reaction in the step (1), the mixed slurry is cooled to 80-100 ℃ for solid-liquid separation;

preferably, the solid-liquid separation of step (2) comprises filtration separation or centrifugation separation.

8. The method according to any one of claims 1 to 7, wherein the composition of the chromium-containing lye of step (2) comprises chromate and caustic, the cations of the chromate and the caustic being the cations of the caustic of step (1);

preferably, the chromium-containing lye is returned to step (1) for liquid phase oxidation of the chromium-containing material.

9. The method according to any one of claims 1 to 8, wherein the reaction tailings of the step (2) comprise chromate crystals and leaching residues;

preferably, the reaction tailings are subjected to slurry washing and filtering to obtain a slag washing solution and leaching residues;

preferably, the composition of the leaching slag comprises Fe₂O₃、MgO、SiO₂、Al₂O₃And CaO.

10. Method according to any of claims 1-9, characterized in that the method comprises the steps of:

(1) mixing and heating a chromium-containing material, a caustic alkali solution and a calcium-containing compound, wherein the chromium-containing material comprises one or a combination of at least two of chromite, chromium slag, chromium mud, chromium-containing dust or leather ash, the particle size of 90% of particles is less than 0.15mm, the concentration of the caustic alkali solution is 15-80 wt%, and the calcium-containing compound comprises Ca (OH)₂、CaO、Ca(NO₃)₂、CaSO₄、CaCl₂The mass ratio of caustic alkali to the chromium-containing material in the caustic alkali solution is (0.5-10): 1, the addition amount of the calcium-containing compound accounts for 0.1-20.0 wt% of the mass of the chromium-containing material, oxidizing gas is continuously introduced, the oxidizing gas comprises air and/or oxygen, the heating is carried out to the reaction temperature, mixed slurry is obtained after the reaction, the reaction temperature is 150-300 ℃, the reaction time is 0.5-8 h, and the oxygen partial pressure is 0.2-10.0 MPa;

(2) cooling the mixed slurry obtained in the step (1) to 80-100 ℃ for solid-liquid separation to obtain chromium-containing alkali liquor and reaction tailings, wherein the chromium-containing alkali liquor comprises chromate and caustic alkali, the reaction tailings comprise chromate crystals and leaching residues, the reaction tailings are subjected to slurry washing and filtering to obtain slag washing liquor and leaching residues, and the leaching residues comprise Fe₂O₃、MgO、SiO₂、Al₂O₃And CaO.

Technical Field

The invention belongs to the technical field of mineral utilization and chromium salt production, and relates to a method for extracting chromium from a chromium-containing material through liquid-phase oxidation.

Background

Chromium is used as an important strategic metal resource and is widely applied to the fields of steel, metallurgy, chemical industry, medicine, aerospace and the like. In recent years, with the development of economy, the demand for chromium resources has been increasing. Chromite is used as a chromium-containing mineral with the highest application value as a main raw material for producing chromium and chromium salt, the utilization rate of chromium resources is low in the production process of chromium salt, and the generated hexavalent chromium has great harm to human bodies and the environment. Therefore, the full utilization of chromium in chromite and the solution of pollution problem in the production process become the current problems to be solved.

The traditional chromium salt production method is mainly a roasting method and comprises calcium roasting and calcium-free roasting, wherein a calcium-containing filler is required to be added during roasting of the chromium salt, so that the process has large slag discharge amount, and the slag contains a large amount of insoluble calcium chromate and is difficult to detoxify; the latter needs to add a large amount of return slag during roasting, which results in lower grade of the roasted raw material chromium. Meanwhile, the traditional roasting process has the problems of high roasting temperature, high energy consumption, low chromium extraction rate and the like, and the generated chromium slag contains hexavalent chromium and is easy to pollute the environment, so that a new utilization mode of chromium-containing materials needs to be researched.

In recent years, various processes for oxidizing chromite by liquid phase have been developed based on the characteristics of raw materials for the utilization of chromium-containing minerals such as chromite and the production of chromium salts. CN 1226512A discloses a clean production method of sodium chromate, which comprises the steps of oxidizing and decomposing chromite by NaOH molten salt medium, wherein the reaction temperature is 500-550 ℃, and a product is leached in a high-alkalinity area; and synchronously cooling and crystallizing the hexavalent chromium leachate to obtain sodium chromate and sodium aluminate mixed type coarse crystals and a crystallization mother liquor, carrying out countercurrent washing and purification on the coarse crystals to obtain a purified sodium chromate crystallization product and a coarse crystal washing solution, and carrying out alkali adjustment crystallization on the coarse crystal washing solution to separate out sodium aluminate. The method has the defects that the reaction temperature is high, the high-concentration leaching solution is directly cooled and crystallized, the solution viscosity is high, the solid-liquid separation is difficult, and the equipment is seriously corroded in a high-temperature and high-alkali environment; the mixed crystals need to be further separated, and the industrial process is long.

CN 101659444A discloses a clean production method for preparing sodium chromate from chromite, which comprises the steps of dissolving chromite in NaOH-NaNO₃-H₂And (3) reacting the O medium with oxidizing gas, wherein sodium nitrate is only used as a catalytic medium and is not consumed in the reaction, a mixed reaction product of alkali liquor, sodium chromate and iron slag is obtained after the reaction, the sodium chromate is separated from the leaching slurry in a coarse crystal form, and the sodium chromate product is obtained by evaporation crystallization after dissolution. The method has the problems of large circulation amount of caustic alkali and nitrate media, low extraction rate of chromium, difficult product separation and more separation steps.

CN 109399716A discloses a method for extracting chromium from chromium-containing materials by liquid phase oxidation, which comprises the steps of taking the chromium-containing materials and alkali as raw materialsPerforming liquid-phase oxidation chromium extraction, wherein the raw materials also comprise an additive, the additive comprises a transition metal compound, the additive is selected from black slag and/or a chromium-containing waste catalyst, and the black slag is Cr obtained by sorting leached slag of liquid-phase oxidation chromium extraction₂O₃Chromium slag with a content higher than 15 wt%; the method introduces transition metal compounds to improve the conversion rate of chromium in chromium-containing materials, but causes high impurity content of products and complex tailing components, and simultaneously, the method has large alkali consumption and higher cost.

In conclusion, for the method for extracting chromium from chromium-containing materials by liquid-phase oxidation, a proper process is required to be selected according to the composition and characteristics of raw materials so as to reduce the content of impurities such as silicon, aluminum and the like in the leachate and simultaneously reduce the consumption of alkali in the liquid-phase oxidation process, thereby reducing the energy consumption and the production cost.

Disclosure of Invention

Aiming at the problems in the prior art, the invention aims to provide a method for extracting chromium from a chromium-containing material through liquid-phase oxidation, wherein a calcium-containing compound is added during the liquid-phase oxidation of the chromium-containing material, so that impurities such as silicon, aluminum and the like in the chromium-containing material can form solid-phase precipitates, the impurities are prevented from entering a leaching solution to influence the purity of a chromate product, and meanwhile, the calcium-containing compound can also reduce the consumption of alkali during the leaching of the chromium-containing material, reduce the subsequent impurity removal operation and reduce the cost.

In order to achieve the purpose, the invention adopts the following technical scheme:

the invention provides a method for extracting chromium from a chromium-containing material by liquid-phase oxidation, which comprises the following steps:

(1) mixing a chromium-containing material, a caustic alkali solution and a calcium-containing compound, heating, introducing an oxidizing gas, and reacting to obtain a mixed slurry;

(2) and (2) carrying out solid-liquid separation on the mixed slurry obtained in the step (1) to obtain chromium-containing alkali liquor and reaction tailings.

In the invention, for the extraction of chromium element in chromium-containing material, caustic alkali solution and oxidizing gas are used for liquid-phase oxidation under heating condition, so that the crystal phase in the chromium-containing material is decomposed and converted, for example, ferrochrome spinel in chromite is oxidized to form chromate, but the chromium-containing material often contains other elements, although iron, magnesium and the like can be converted into oxides to be left in tailings, impurity elements such as silicon, aluminum and the like can be converted into silicate and aluminate under reaction conditions to enter into the solution, and the purity of the chromate solution is influenced, therefore, in the invention, a calcium-containing compound is added in the chromium-containing material chromium extraction process, and the method has the following functions:

firstly, the calcium-containing compound has higher chemical activity in the hydrothermal system, can promote the decomposition of ferrochrome spinel in chromite, and reduces the temperature of leaching reaction on the premise of ensuring higher chromium leaching rate; secondly, calcium compounds can generate calcium silicate, calcium aluminate and calcium aluminosilicate precipitates with anions of elements such as silicon, aluminum and the like, and the reaction is easier to occur under the hydrothermal condition, so that the content of impurities such as aluminum, silicon and the like in the leachate is reduced, and the subsequent impurity removal operation is reduced; finally, the addition of the calcium-containing compound in the liquid-phase oxidation chromium extraction process can improve the reaction kinetic condition for replacing alkali in the leaching slag, and greatly reduce the alkali content in the leaching slag; the calcium-containing compound can also partially replace the action of caustic alkali, so that the consumption of alkali is reduced; based on the effect of the calcium-containing compound, the method disclosed by the invention is simple to operate, has an obvious effect, can effectively reduce the cost and has better economic benefit.

The following technical solutions are preferred technical solutions of the present invention, but not limited to the technical solutions provided by the present invention, and technical objects and advantageous effects of the present invention can be better achieved and achieved by the following technical solutions.

As a preferred technical scheme of the invention, the chromium-containing material in the step (1) comprises one or a combination of at least two of chromite, chromium slag, chromium mud, chromium-containing dust or leather ash, and typical but non-limiting examples of the combination are as follows: a combination of chromite and chromium slag, a combination of chromium mud and chromium-containing dust, a combination of chromite, chromium mud and leather ash, a combination of chromite, chromium slag and chromium-containing dust, and the like.

Preferably, 90% of the particles in the chromium-containing material of step (1) have a particle size of less than 0.15mm, for example 0.15mm, 0.14mm, 0.12mm, 0.10mm, 0.09mm, 0.075mm, 0.06mm, 0.05mm or 0.04mm, but not limited to the values recited, and other values in this range are equally suitable, preferably less than 0.075 mm.

In the present invention, one of the parameters characterizing the particles of the material is D (90), and the numerical value of D (90) indicates that 90% of the particles have a particle diameter below this particle diameter.

Preferably, the caustic solution of step (1) comprises a NaOH solution and/or a KOH solution, preferably a NaOH solution.

Preferably, the caustic solution in step (1) has a concentration of 15 to 80 wt%, for example, 15 wt%, 30 wt%, 40 wt%, 50 wt%, 60 wt%, 70 wt%, or 80 wt%, but not limited to the recited values, and other values in the range are also applicable, preferably 30 to 70 wt%, and more preferably 40 to 60 wt%.

As a preferred embodiment of the present invention, the calcium-containing compound of step (1) comprises Ca (OH)₂、CaO、Ca(NO₃)₂、CaSO₄Or CaCl₂Any one or a combination of at least two of the following, typical but non-limiting examples being: ca (OH)₂And CaO, CaO and Ca (NO)₃)₂A combination of (3), Ca (OH)₂、Ca(NO₃)₂And CaCl₂A combination of (3), Ca (OH)₂、CaO、Ca(NO₃)₂And CaSO₄Combinations of (A), (B) and (C), preferably CaO and/or Ca (OH)₂。

Preferably, the calcium-containing compound of step (1) is added in the form of a solid, an aqueous solution, a mixed slurry or a mixed slag containing the calcium-containing compound.

In the invention, the calcium-containing compound is mixed with caustic alkali, and after the calcium-containing compound is dissolved, the insoluble precipitate is generated according to the type and the characteristics of anions in the solution after reaction by mainly utilizing the characteristics of calcium ions in the alkaline solution, so that impurities such as silicon, aluminum and the like can enter leaching residues.

In a preferred embodiment of the present invention, the mass ratio of the caustic alkali to the chromium-containing material in the caustic alkali solution in the step (1) is (0.5 to 10):1, for example, 0.5:1, 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 8:1, or 10:1, but the present invention is not limited to the above-mentioned values, and other values not shown in the above-mentioned value range are also applicable, and preferably (2 to 8):1, and more preferably (3 to 5): 1.

Preferably, the calcium-containing compound in step (1) is added in an amount of 0.1-20.0 wt%, such as 0.1 wt%, 0.5 wt%, 1.0 wt%, 2.5 wt%, 5.0 wt%, 7.5 wt%, 10.0 wt%, 12.5 wt%, 15.0 wt% or 20.0 wt%, based on the mass of the chromium-containing material, but not limited to the recited values, and other values in the range are also applicable, preferably 0.5-15.0 wt%, more preferably 2.5-12.5 wt%.

In the invention, the addition amount of the calcium-containing compound is related to the type of the chromium-containing material and the content of aluminum-silicon impurities in the chromium-containing material, and if the addition amount of the calcium-containing compound is too small, aluminum-silicon and silicon-containing impurity ions entering the solution cannot be fully precipitated, so that the impurity ion content in the leaching solution is still high; if the amount of the calcium-containing compound is too large, the chromium content in the leaching residue may be too high, and the recovery rate of chromium may be reduced.

As a preferable technical scheme of the invention, the oxidizing gas in the step (1) comprises air and/or oxygen, wherein when the air and the oxygen are used together, the air can be called oxygen-enriched air, different proportions of the oxygen and the air can be selected, and the oxygen is preferred.

Preferably, the oxidizing gas is continuously introduced in the step (1).

Preferably, the mixed material in the step (1) is added into a reaction device, and the reaction device is sealed and then is filled with oxidizing gas.

In a preferred embodiment of the present invention, the heating in step (1) is carried out at a reaction temperature of 150 to 300 ℃, for example, 150 ℃, 160 ℃, 180 ℃, 200 ℃, 220 ℃, 250 ℃, 280 ℃ or 300 ℃, but not limited to the above-mentioned values, and other values not shown in the above-mentioned range are also applicable, preferably 180 to 280 ℃.

Preferably, the reaction time in step (1) is 0.5 to 8 hours, such as 0.5 hour, 2 hours, 3 hours, 4 hours, 0.5 hour, 5 hours, 6 hours or 8 hours, but not limited to the recited values, and other values not recited in the range of the values are also applicable, preferably 2 to 6 hours.

Preferably, the reaction in step (1) has an oxygen partial pressure of 0.2 to 10.0MPa, for example, 0.2MPa, 1.0MPa, 2.0MPa, 3.0MPa, 4.0MPa, 5.0MPa, 6.0MPa, 8.0MPa or 10.0MPa, but not limited to the values listed, and other values not listed in the numerical range are also applicable, preferably 2.0 to 6.0 MPa.

In a preferred embodiment of the present invention, after the reaction in step (1), the mixed slurry is cooled to 80 to 100 ℃ and subjected to solid-liquid separation, for example, 80 ℃, 85 ℃, 90 ℃, 95 ℃ or 100 ℃, but the present invention is not limited to the above-mentioned values, and other values not shown in the above-mentioned range of values are also applicable.

Preferably, the solid-liquid separation of step (2) comprises filtration separation or centrifugation separation.

As a preferable technical scheme of the invention, the composition of the chromium-containing alkali liquor in the step (2) comprises chromate and caustic alkali, and the positive ions of the chromate and the caustic alkali are positive ions of the caustic alkali in the step (1).

Preferably, the chromium-containing lye is returned to step (1) for liquid phase oxidation of the chromium-containing material.

As a preferable technical scheme of the invention, the reaction tailings in the step (2) comprise chromate crystals and leaching residues.

Preferably, the reaction tailings are subjected to slurry washing and filtering to obtain a slag washing solution and leaching residues.

Preferably, the composition of the leaching slag is measured in terms of oxides of the elements, including Fe₂O₃、MgO、SiO₂、Al₂O₃And CaO.

As a preferred technical scheme of the invention, the method comprises the following steps:

(1) mixing and heating a chromium-containing material, a caustic alkali solution and a calcium-containing compound, wherein the chromium-containing material comprises one or a combination of at least two of chromite, chromium slag, chromium mud, chromium-containing dust or leather ash, the particle size of 90% of particles is less than 0.15mm, the concentration of the caustic alkali solution is 15-80 wt%, and the calcium-containing compound comprisesIncluding Ca (OH)₂、CaO、Ca(NO₃)₂、CaSO₄、CaCl₂The mass ratio of caustic alkali to the chromium-containing material in the caustic alkali solution is (0.5-10): 1, the addition amount of the calcium-containing compound accounts for 0.1-20.0 wt% of the mass of the chromium-containing material, oxidizing gas is continuously introduced, the oxidizing gas comprises air and/or oxygen, the heating is carried out to the reaction temperature, mixed slurry is obtained after the reaction, the reaction temperature is 150-300 ℃, the reaction time is 0.5-8 h, and the oxygen partial pressure is 0.2-10.0 MPa;

(2) cooling the mixed slurry obtained in the step (1) to 80-100 ℃ for solid-liquid separation to obtain chromium-containing alkali liquor and reaction tailings, wherein the chromium-containing alkali liquor comprises chromate and caustic alkali, the reaction tailings comprise chromate crystals and leaching residues, the reaction tailings are subjected to slurry washing and filtering to obtain slag washing liquor and leaching residues, and the leaching residues comprise Fe₂O₃、MgO、SiO₂、Al₂O₃And CaO.

Compared with the prior art, the invention has the following beneficial effects:

(1) according to the method, the calcium-containing compound is added in the liquid-phase oxidation chromium extraction process of the chromium-containing material, and can generate corresponding calcium silicate and calcium aluminate precipitates or composite calcium aluminosilicate precipitates with anions of impurities such as silicon and aluminum in the chromium-containing material, and the impurities such as silicon and aluminum are fixed in tailings from a reaction source, so that the content of the impurities such as silicon and aluminum in the leachate is reduced, and the operation load of a subsequent impurity removal process is reduced;

(2) in the method, the calcium-containing compound has higher chemical activity in a hydrothermal system, can promote the decomposition of ferrochrome spinel in chromite, ensures that the chromium has higher leaching rate which can reach more than 95.1 percent, and reduces the temperature of leaching reaction;

(3) according to the method, the reaction kinetic condition of replacing alkali in the leaching slag can be improved by adding the calcium-containing compound in the liquid-phase oxidation chromium extraction process, the reaction rate is improved, the alkali content in the leaching slag is greatly reduced, and the alkali consumption in the leaching process is reduced;

(4) the method disclosed by the invention is simple to operate, has an obvious effect, can effectively reduce the cost and has better economic benefits.

Detailed Description

In order to better illustrate the present invention and facilitate the understanding of the technical solutions of the present invention, the present invention is further described in detail below. However, the following examples are only simple examples of the present invention and do not represent or limit the scope of the present invention, which is defined by the claims.

The invention provides a method for extracting chromium from chromium-containing materials through liquid-phase oxidation, which comprises the following steps:

(1) mixing a chromium-containing material, a caustic alkali solution and a calcium-containing compound, heating, introducing an oxidizing gas, and reacting to obtain a mixed slurry;

(2) and (2) carrying out solid-liquid separation on the mixed slurry obtained in the step (1) to obtain chromium-containing alkali liquor and reaction tailings.

The following are typical but non-limiting examples of the invention:

example 1:

the embodiment provides a method for extracting chromium from a chromium-containing material by liquid-phase oxidation, which comprises the following steps:

(1) mixing and heating a chromium-containing material, NaOH solution and CaO solid, wherein the chromium-containing material is chromite, the D (90) value of the chromium-containing material is 0.06mm, the concentration of the NaOH solution is 60 wt%, the mass ratio of NaOH to chromite in the NaOH solution is 6:1, the addition amount of CaO accounts for 5 wt% of the mass of the chromite, continuously introducing oxygen, heating to the reaction temperature, reacting to obtain mixed slurry, wherein the reaction temperature is 230 ℃, the reaction time is 4 hours, and the oxygen partial pressure is 3.2 MPa;

(2) and (2) cooling the mixed slurry obtained in the step (1) to 90 ℃, filtering and separating to obtain chromium-containing alkali liquor and reaction tailings, wherein the chromium-containing alkali liquor comprises sodium chromate and caustic soda, the chromium-containing alkali liquor is returned to the step (1) for liquid phase oxidation of chromite, the reaction tailings comprise sodium chromate crystals and leaching residues, and the reaction tailings are subjected to slurry washing and filtering by using water to obtain a slag washing solution and the leaching residues.

Example 2:

the embodiment provides a method for extracting chromium from a chromium-containing material by liquid-phase oxidation, which comprises the following steps:

(1) mixing chromium-containing material, KOH solution and Ca (OH)₂Mixing and heating the solution, wherein the chromium-containing material is chromite, the D (90) value of the chromium-containing material is 0.075mm, the concentration of the KOH solution is 50 wt%, the mass ratio of KOH to chromite in the KOH solution is 8:1, and the Ca (OH)₂The adding amount of the chromium iron is 8 wt% of the mass of the chromite, oxygen is continuously introduced, the mixture is heated to the reaction temperature, mixed slurry is obtained after the reaction, the reaction temperature is 180 ℃, the reaction time is 6 hours, and the oxygen partial pressure is 5 MPa;

(2) and (2) cooling the mixed slurry obtained in the step (1) to 80 ℃, filtering and separating to obtain chromium-containing alkali liquor and reaction tailings, wherein the chromium-containing alkali liquor comprises potassium chromate and caustic potash, the chromium-containing alkali liquor returns to the step (1) and is used for liquid phase oxidation of chromite, the reaction tailings comprise potassium chromate crystals and leaching residues, and the reaction tailings are subjected to slurry washing and filtering by using water to obtain a slag washing solution and the leaching residues.

Example 3:

the embodiment provides a method for extracting chromium from a chromium-containing material by liquid-phase oxidation, which comprises the following steps:

(1) mixing chromium-containing material, NaOH solution and Ca (NO)₃)₂Mixing and heating the solids, wherein the chromium-containing material is chromite, the D (90) value of the chromium-containing material is 0.1mm, the concentration of the NaOH solution is 30 wt%, the mass ratio of NaOH to chromite in the NaOH solution is 2:1, and the Ca (NO) is added₃)₂The adding amount of the slurry is 15 wt% of the mass of the chromite, oxygen-enriched air is continuously introduced, wherein the volume fraction of oxygen is 50%, the slurry is heated to the reaction temperature, mixed slurry is obtained after the reaction, the reaction temperature is 280 ℃, the reaction time is 1 hour, and the oxygen partial pressure is 2 MPa;

(2) and (2) cooling the mixed slurry obtained in the step (1) to 100 ℃, and performing centrifugal separation to obtain chromium-containing alkali liquor and reaction tailings, wherein the chromium-containing alkali liquor comprises sodium chromate and caustic soda, the chromium-containing alkali liquor is returned to the step (1) for liquid phase oxidation of chromite, the reaction tailings comprise sodium chromate crystals and leaching residues, and the reaction tailings are subjected to slurry washing and filtering by using water to obtain a slag washing solution and the leaching residues.

Example 4:

the embodiment provides a method for extracting chromium from a chromium-containing material by liquid-phase oxidation, which comprises the following steps:

(1) mixing chromium-containing material, NaOH solution and CaSO₄Mixing and heating the solids, wherein the chromium-containing material is chromium slag, the D (90) value of the chromium-containing material is 0.15mm, the concentration of the NaOH solution is 80 wt%, the mass ratio of NaOH to the chromium slag in the NaOH solution is 4:1, and the CaSO₄The addition amount of the (B) is 1 wt% of the mass of the chromium slag, oxygen-enriched air is continuously introduced, wherein the volume fraction of oxygen is 80%, the mixture is heated to the reaction temperature, mixed slurry is obtained after the reaction, the reaction temperature is 300 ℃, the reaction time is 0.5h, and the oxygen partial pressure is 7.5 MPa;

(2) and (2) cooling the mixed slurry obtained in the step (1) to 85 ℃, and performing centrifugal separation to obtain chromium-containing alkali liquor and reaction tailings, wherein the chromium-containing alkali liquor comprises sodium chromate and caustic soda, the chromium-containing alkali liquor is returned to the step (1) for liquid phase oxidation of the chromium slag, the reaction tailings comprise sodium chromate crystals and leaching residues, and the reaction tailings are subjected to slurry washing and filtering by using water to obtain a slag washing solution and the leaching residues.

Example 5:

the embodiment provides a method for extracting chromium from a chromium-containing material by liquid-phase oxidation, which comprises the following steps:

(1) mixing and heating a chromium-containing material, a KOH solution and a CaO solid, wherein the chromium-containing material is leather ash, the D (90) value of the chromium-containing material is 0.12mm, the concentration of the KOH solution is 15 wt%, the mass ratio of KOH to the chromium-containing material in the KOH solution is 10:1, the addition amount of CaO accounts for 0.5 wt% of the mass of the chromium-containing material, continuously introducing oxygen, heating to the reaction temperature, and reacting to obtain a mixed slurry, wherein the reaction temperature is 150 ℃, the reaction time is 8 hours, and the oxygen partial pressure is 10 MPa;

(2) and (2) cooling the mixed slurry obtained in the step (1) to 88 ℃, filtering and separating to obtain chromium-containing alkali liquor and reaction tailings, wherein the chromium-containing alkali liquor comprises potassium chromate and caustic potash, the chromium-containing alkali liquor is returned to the step (1) and is used for liquid phase oxidation of chromium-containing materials, the reaction tailings comprise potassium chromate crystals and leaching residues, and the reaction tailings are subjected to slurry washing and filtering by using water to obtain a slag washing solution and the leaching residues.

Example 6:

the embodiment provides a method for extracting chromium from a chromium-containing material by liquid-phase oxidation, which comprises the following steps:

(1) mixing chromium-containing material, NaOH solution, CaO and Ca (OH)₂Mixing and heating the solids, wherein the chromium-containing material is chromite, the D (90) value of the chromite is 0.05mm, the concentration of the NaOH solution is 40 wt%, the mass ratio of NaOH to chromite in the NaOH solution is 5:1, and the CaO and Ca (OH)₂The adding amount of solids accounts for 3 wt% of the mass of the chromite, oxygen-enriched air is continuously introduced, wherein the volume fraction of oxygen is 40%, the heating is carried out to the reaction temperature, mixed slurry is obtained after the reaction, the reaction temperature is 200 ℃, the reaction time is 5 hours, and the oxygen partial pressure is 1 MPa;

(2) and (2) cooling the mixed slurry obtained in the step (1) to 95 ℃ for centrifugal separation to obtain chromium-containing alkali liquor and reaction tailings, wherein the chromium-containing alkali liquor comprises sodium chromate and caustic soda, the chromium-containing alkali liquor is returned to the step (1) for liquid phase oxidation of chromite, the reaction tailings comprise sodium chromate crystals and leaching residues, and the reaction tailings are subjected to slurry washing and filtering by using water to obtain a slag washing solution and the leaching residues.

Example 7:

the embodiment provides a method for extracting chromium from a chromium-containing material by liquid-phase oxidation, which comprises the following steps:

(1) mixing chromium-containing material, KOH solution and Ca (OH)₂Mixing and heating the slurry, wherein the chromium-containing material is chromium-containing dust, the D (90) value of the chromium-containing dust is 0.08mm, the concentration of the KOH solution is 20 wt%, the mass ratio of KOH in the KOH solution to the chromium-containing material is 3:1, and the Ca (OH)₂The adding amount of the mixed slurry accounts for 20 wt% of the mass of the chromium-containing material, air is continuously introduced, the mixed slurry is heated to the reaction temperature, the mixed slurry is obtained after the reaction, the reaction temperature is 250 ℃, the reaction time is 3 hours, and the oxygen partial pressure is 6 MPa;

(2) and (2) cooling the mixed slurry obtained in the step (1) to 83 ℃, filtering and separating to obtain chromium-containing alkali liquor and reaction tailings, wherein the chromium-containing alkali liquor comprises potassium chromate and caustic potash, the chromium-containing alkali liquor is returned to the step (1) and is used for liquid phase oxidation of chromium-containing materials, the reaction tailings comprise potassium chromate crystals and leaching residues, and the reaction tailings are subjected to slurry washing and filtering by using water to obtain a slag washing solution and the leaching residues.

Example 8:

the embodiment provides a method for extracting chromium from a chromium-containing material by liquid-phase oxidation, which comprises the following steps:

(1) chromium-containing material, NaOH solution, CaO and CaCl₂Mixing and heating the solids, wherein the chromium-containing material is chromite, the D (90) value of the chromium-containing material is 0.04mm, the concentration of the NaOH solution is 70 wt%, the mass ratio of NaOH to chromite in the NaOH solution is 7:1, and CaO and CaCl are added₂The adding amount of the solids accounts for 4.5 wt% of the mass of the chromite, oxygen-enriched air is continuously introduced, wherein the volume fraction of oxygen is 60%, the heating is carried out to the reaction temperature, mixed slurry is obtained after the reaction, the reaction temperature is 270 ℃, the reaction time is 1.5h, and the oxygen partial pressure is 8 MPa;

(2) and (2) cooling the mixed slurry obtained in the step (1) to 92 ℃ for centrifugal separation to obtain chromium-containing alkali liquor and reaction tailings, wherein the chromium-containing alkali liquor comprises sodium chromate and caustic soda, the chromium-containing alkali liquor is returned to the step (1) for liquid phase oxidation of chromite, the reaction tailings comprise sodium chromate crystals and leaching residues, and the reaction tailings are subjected to slurry washing and filtering by using water to obtain a slag washing solution and the leaching residues.

Example 9:

this example provides a process for the liquid phase oxidative extraction of chromium from a chromium-containing feed, which process is referred to the process of example 3 with the only difference that: ca (NO) in step (1)₃)₂The amount of the added calcium-containing compound is 22 wt% of the mass of the chromite, namely, the amount of the added calcium-containing compound is a little bit more.

Comparative example 1:

this comparative example provides a process for the liquid phase oxidative extraction of chromium from a chromium-containing feed, which process is referred to the process of example 1 with the only difference that: no CaO solid is added in the step (1).

The concentrations of aluminum and silicon in the chromium-containing alkaline solution and the slag washing solution obtained in examples 1 to 9 and comparative example 1 were measured by an inductively coupled plasma emission spectrometer (ICP-OES), and the recovery rate of chromium from chromite was calculated based on the contents of chromium in the chromium-containing alkaline solution, the slag washing solution and the leached slag, and the results are shown in table 1, and the contents of aluminum, silicon and alkali metals in the leached slag (in terms of corresponding oxides) were measured in the same manner, and the results are shown in table 2.

TABLE 1 measurement of Al and Si concentrations and Cr recovery in chromium-containing lye and slag washings as described in examples 1 to 9 and comparative example 1

TABLE 2 measurement results of contents of aluminum, silicon and alkali metals in leached residues described in examples 1 to 9 and comparative example 1

As can be seen from the above tables 1 and 2, in examples 1-8, calcium-containing compounds are used in the process of extracting chromium from chromium-containing materials by liquid-phase oxidation, and proper addition amount is selected, so that aluminum-silicon impurities can be fixed in leaching slag according to precipitation reaction of the compounds and ions containing aluminum and silicon impurities, and the aluminum-silicon impurities are prevented from entering into chromium-containing alkali liquor; the chromium-containing alkali liquor is recycled, the recovery rate of chromium is comprehensively calculated according to the concentration of chromate ions in the slag washing liquid, and the recovery rate can reach more than 95.1% in the examples 1-8; meanwhile, the contents of aluminum and silicon in the leaching residues of the examples 1 to 8 are obviously higher than the corresponding contents in the comparative example 1, the calcium compound also has the functions of replacing alkali metals in the leaching residues and reducing the alkali content in the leaching residues, and the alkali metal content in the leaching residues of the examples 1 to 8 is far lower than the result in the comparative example 1;

in example 9, since the amount of the calcium-containing compound added was too high, the content of calcium ions in the solution was still high after the calcium ions had precipitated with aluminate and silicate, and at this time, the calcium ions were combined with chromate ions in the solution to form a precipitate of calcium chromate, resulting in a high chromium content in the leaching residue, and a decrease in the recovery rate of chromium.

It can be seen from the above examples and comparative examples that the method of the present invention adds a calcium-containing compound during the liquid phase oxidation extraction of chromium from a chromium-containing material, which can generate corresponding calcium silicate and calcium aluminate precipitates or composite calcium aluminosilicate precipitates with the anions of impurities such as silicon and aluminum in the chromium-containing material, and fixes the impurities such as silicon and aluminum in the tailings from the reaction source, thereby reducing the content of impurities such as silicon and aluminum in the leachate and reducing the operation load of the subsequent impurity removal process; in the method, the calcium-containing compound has higher chemical activity in a hydrothermal system, can promote the decomposition of ferrochrome spinel in chromite, ensures that chromium has higher leaching rate, and reduces the temperature of leaching reaction; according to the method, the reaction kinetic condition of alkali in the leaching residue can be improved by adding the calcium-containing compound in the liquid-phase oxidation chromium extraction process, the reaction rate is increased, the alkali content in the leaching residue is greatly reduced, and the alkali consumption in the leaching process is reduced; the method is simple to operate, has obvious effect, can effectively reduce the cost and has better economic benefit.

The applicant states that the present invention is illustrated in detail by the above examples, but the present invention is not limited to the above detailed methods, i.e. it is not meant that the present invention must rely on the above detailed methods for its implementation. It will be apparent to those skilled in the art that any modifications to the present invention, equivalents of the method of the present invention and additions of ancillary steps, selection of specific means, etc., are within the scope and disclosure of the present invention.