阅读说明：本技术 一种抑制钒渣钒铬共提过程的循环液中铬酸钠还原的方法 (Method for inhibiting reduction of sodium chromate in circulating liquid in vanadium slag vanadium-chromium co-extraction process ) 是由 王少娜 杜浩 刘彪 王新东 李兰杰 王海旭 于 2020-06-15 设计创作，主要内容包括：本发明提供一种抑制钒渣钒铬共提过程的循环液中铬酸钠还原的方法,所述方法通过增加预氧化反应步骤,并将预氧化反应的温度控制在120℃以下,能够有效抑制含铬酸钠循环液中铬酸钠向反尖晶石类物相的转变,同时协同保障预反应的压力,可有效抑制含铬酸钠循环液中Cr<Sup>6+</Sup>的还原及不可逆反应的发生,实现高铬酸钠循环介质中钒渣中钒铬的高效共同提取,钒的浸出率达到88wt％以上,铬的浸出率达到80wt％以上。(The invention provides a method for inhibiting reduction of sodium chromate in circulating liquid in a vanadium slag vanadium-chromium co-extraction process, which can effectively inhibit the transformation of sodium chromate in sodium chromate-containing circulating liquid to inverse spinel phase by adding a pre-oxidation reaction step and controlling the temperature of the pre-oxidation reaction to be below 120 ℃, and can effectively inhibit Cr in the sodium chromate-containing circulating liquid by cooperatively ensuring the pressure of the pre-reaction 6+ And the occurrence of irreversible reaction, to effectThe vanadium and the chromium in the vanadium slag in the high sodium chromate circulating medium are efficiently and jointly extracted, the leaching rate of the vanadium reaches over 88 wt%, and the leaching rate of the chromium reaches over 80 wt%.)

1. A method for inhibiting reduction of sodium chromate in circulating liquid in a vanadium slag vanadium-chromium co-extraction process is characterized by comprising the following steps:

(1) mixing the vanadium slag and the sodium chromate-containing circulating liquid to obtain a reaction liquid;

(2) carrying out pre-oxidation reaction on the reaction solution obtained in the step (1) at the temperature of less than or equal to 120 ℃ to obtain pre-oxidation solution;

(3) and (3) heating the pre-oxidation solution obtained in the step (2), carrying out vanadium-chromium co-extraction reaction, and carrying out solid-liquid separation to obtain tailings and a vanadium-chromium-containing leaching solution.

2. The method of claim 1, wherein the sodium chromate containing recycle liquor of step (1) comprises an alkali;

preferably, the alkali concentration of the circulating liquid containing sodium chromate is 30-60 wt%;

preferably, the base is sodium hydroxide.

3. The method of claim 1 or 2, wherein the recycled solution containing sodium chromate in step (1) comprises Na₂CrO₄；

Preferably, Na in the circulating liquid containing sodium chromate₂CrO₄The concentration is 0.01-15 wt%.

4. The method according to any one of claims 1 to 3, wherein the sodium chromate-containing circulating liquid in the step (1) further comprises Na₃VO₄And/or Na₂SiO₃；

Preferably, Na in the circulating liquid containing sodium chromate₃VO₄The concentration is 0-5 wt%;

preferably, Na in the circulating liquid containing sodium chromate₂SiO₃The concentration is 0-3 wt%.

5. The method according to any one of claims 1 to 4, wherein the mass ratio of sodium hydroxide to vanadium slag in the circulating solution containing sodium chromate in the step (1) is 1-20: 1.

6. The method according to any one of claims 1 to 5, wherein the temperature of the pre-oxidation reaction in the step (2) is 20 to 120 ℃;

preferably, the oxygen pressure of the pre-oxidation reaction is more than or equal to 0.5MPa, and preferably 0.5-2 MPa;

preferably, the reaction time of the pre-oxidation reaction is more than or equal to 0.5h, and preferably 0.5-3 h.

7. The method according to any one of claims 1 to 6, wherein the pre-oxidation reaction in step (2) is carried out in an oxidizing gas;

preferably, the oxidizing gas comprises oxygen and/or air.

8. The method according to any one of claims 1 to 7, wherein the vanadium-chromium co-extraction reaction in the step (3) comprises a pressurization reaction or an aeration reaction;

preferably, the temperature of the vanadium-chromium co-extraction reaction is 125-400 ℃.

9. The method according to any one of claims 1 to 8, further comprising, after step (3): crystallizing the vanadium-chromium-containing leaching solution by using sodium vanadate and sodium chromate to respectively obtain sodium vanadate and sodium chromate products;

preferably, the circulating solution containing sodium chromate in the step (1) comprises a crystallization mother solution obtained by crystallizing sodium vanadate and crystallizing sodium chromate in the leaching solution containing vanadium and chromium in the step (3).

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

(1) mixing the vanadium slag and the sodium chromate circulating liquid to obtain a reaction liquid, wherein the alkali concentration in the sodium chromate circulating liquid is 30-60 wt%, and Na is contained in the sodium chromate circulating liquid₂CrO₄0.01 to 15 wt% of Na₃VO₄0 to 5 wt% of Na₂SiO₃The concentration is 0-3 wt%; the mass ratio of sodium hydroxide to vanadium slag in the sodium chromate-containing circulating liquid is 1-20: 1;

(2) carrying out pre-oxidation reaction on the reaction solution in the step (1) in oxidizing gas at the temperature of less than or equal to 120 ℃ and the oxygen pressure of more than or equal to 0.5MPa for more than or equal to 0.5h to obtain pre-oxidation solution;

(3) heating the pre-oxidation solution obtained in the step (2) to 125-400 ℃, carrying out vanadium-chromium co-extraction reaction, and carrying out solid-liquid separation to obtain tailings and a vanadium-chromium-containing leaching solution;

and (2) crystallizing the vanadium-chromium-containing leaching solution and sodium chromate to obtain crystallized mother liquor, wherein the sodium chromate-containing circulating liquor obtained in the step (1) comprises crystallized mother liquor obtained by crystallizing sodium vanadate and crystallizing sodium chromate in the step (3).

Technical Field

The invention relates to the technical field of vanadium chemical metallurgy, relates to a liquid-phase vanadium and chromium oxide co-extraction process of chromium-containing vanadium slag, and particularly relates to a method for inhibiting reduction of sodium chromate in circulating liquid in the vanadium slag vanadium and chromium co-extraction process.

Background

The vanadium titano-magnetite is a main vanadium-containing mineral resource in the world, and vanadium slag produced by blast furnace smelting of the vanadium titano-magnetite is the most important raw material for producing vanadium, and accounts for more than 60 percent of the world vanadium productivity. China is one of the countries in the world with abundant vanadium titano-magnetite resources, and is mainly distributed in Panzhihua region of Sichuan, Chengde region of Hebei and Maanshan region of Anhui. The vanadium titano-magnetite is associated with abundant vanadium and chromium resources, and because the thermodynamic properties of chromium and vanadium are similar, vanadium and chromium are simultaneously oxidized and blown out from a converter in the smelting process of the vanadium titano-magnetite, so that chromium is often associated with the obtained vanadium slag. And the chromium content in the high-chromium vanadium-titanium magnetite with the reserve of up to 36 hundred million tons in the Panxi area of China is even 2 times of the vanadium content, and the vanadium and chromium have great significance together.

In recent years, aiming at the co-extraction of vanadium and chromium in vanadium slag, new processes mainly represented by a sodium roasting improvement method and a liquid-phase oxidation method are continuously developed, and the progress of related technologies is greatly promoted.

CN102127655A discloses a method for decomposing vanadium slag by NaOH solution at normal pressure, the reaction temperature is 180-260 ℃, compared with the roasting process, the temperature in the vanadium extraction process is greatly reduced, the energy consumption is reduced, the vanadium extraction efficiency is obviously improved, but the vanadium and chromium can not be extracted together.

CN102127654A discloses a method for decomposing vanadium-chromium-containing slag by using sodium hydroxide molten salt, wherein the reaction temperature is 500-600 ℃, the process can realize vanadium-chromium co-extraction, but the temperature in the molten salt reaction process is higher.

CN102127656A discloses a method for liquid-phase oxidative decomposition of vanadium slag, wherein the process of oxidative decomposition of vanadium slag is enhanced by using sodium hydroxide and sodium nitrate media, the reaction temperature is lower than that of sodium hydroxide molten salt media, but the sodium nitrate media are introduced, and the steps of the subsequent separation process are increased.

CN101812588A discloses a method for decomposing vanadium slag by potassium hydroxide solution at normal pressure, the reaction is carried out at 180-260 ℃, the temperature is greatly reduced, vanadium and chromium can be extracted together, and the defect is that the cost of potassium hydroxide medium is high.

CN102531056B discloses a method for cleanly producing sodium vanadate and sodium chromate by pressure leaching vanadium slag, which comprises the steps of introducing oxidizing gas into a 20-50 wt% NaOH solution at 100-400 ℃ under the pressure reaction condition to carry out oxidation reaction, and obtaining sodium vanadate and sodium chromate containing NaOH and Na after the reaction₂CrO₄And Na₃VO₄And the mixed slurry is subjected to solid-liquid separation, impurity removal, sodium vanadate crystallization and sodium chromate crystallization to obtain sodium vanadate and sodium chromate products. CN105400967B further discloses a method for extracting vanadium and chromium from vanadium slag at low temperature and normal pressure, the method adopts 40-70 wt% NaOH solution to react with vanadium slag and oxidizing gas at 100-160 ℃, the oxidizing gas is introduced into a reaction kettle through a micropore gas distribution device, and the extraction rate of vanadium and chromium is higher than 85%. However, although the above two patents can realize the co-extraction of vanadium and chromium when the sodium hydroxide solution is used for leaching vanadium slag, the filtrate obtained after fractional crystallization of sodium vanadate and sodium chromate can not achieve a good co-extraction effect when used for leaching vanadium slag as a medium circulating liquid, so that the process circulating liquid can not be reused, and the loss of sodium hydroxide is large. The inventors found that the reason for this is: in addition to NaOH, a certain amount of Na reaching the saturated concentration is also contained in the filtrate₃VO₄And Na₂CrO₄In which Na is₂CrO₄That is, Cr (VI) is a strong oxidizing substance, and will undergo reduction reaction with Fe (II) and V (III) with reducibility in the vanadium slag as shown in formulas (1) to (4) to generate Cr (OH)₃And inverse spinel (Mn)_0.87,Fe_0.13)(Mn_0.13,Fe_0.87,Cr)O₄. Once the inverse spinel phase is generated, the reaction is extremely difficult to be reversed to generate Cr (VI) in the subsequent reaction process of liquid-phase oxidation of the vanadium slag even through high temperature and high oxygen pressure, which causes that not only the chromium in the vanadium slag can not be extracted in the reaction of using the circulating liquid containing sodium chromate, but also the chromium in the circulating liquid generates inverse spinel (Mn)_0.87,Fe_0.13)(Mn_0.13,Fe_0.87,Cr)O₄The chromium content in the obtained tailings is higher than that in the raw material vanadium slagThe amount is still high and the process cannot be carried out smoothly.

Cr(OH)₃(s)+OH^-→[Cr(OH)₄]^-(aq) (3)

[Cr(OH)₄]^-(aq)→CrO₂ ^-+2H₂O(l) (4)

In the practical application process of the process, the filtrate obtained after fractional crystallization of sodium vanadate and sodium chromate is used as medium circulating liquid for leaching vanadium slag, so that the aim of complete circulation and no discharge of the liquid medium in the process is fulfilled.

Therefore, the method solves the problem that the crystallized filtrate can not be repeatedly used as the circulating liquid, further realizes the high-efficiency extraction of vanadium and chromium in the vanadium slag and the repeated utilization of alkali in the circulating liquid, and is the key of smooth process and industrial application.

Disclosure of Invention

In order to solve the technical problems, the invention provides a method for inhibiting reduction of sodium chromate in circulating liquid in a vanadium slag vanadium-chromium co-extraction process, which is characterized in that a pre-oxidation reaction step is added, the temperature of the pre-oxidation reaction is controlled below 120 ℃, and the efficient co-extraction of vanadium and chromium in vanadium slag can be realized while the reduction of sodium chromate in a circulating medium is inhibited.

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

in a first aspect, the invention provides a method for inhibiting reduction of sodium chromate in circulating liquid in a vanadium slag vanadium-chromium co-extraction process, which comprises the following steps:

(1) mixing the vanadium slag and the sodium chromate-containing circulating liquid to obtain a reaction liquid;

(2) carrying out pre-oxidation reaction on the reaction solution obtained in the step (1) at the temperature of less than or equal to 120 ℃ to obtain pre-oxidation solution;

(3) and (3) heating the pre-oxidation solution obtained in the step (2), carrying out vanadium-chromium co-extraction reaction, and carrying out solid-liquid separation to obtain tailings and a vanadium-chromium-containing leaching solution.

In the method for inhibiting reduction of sodium chromate in the circulating liquid in the vanadium slag vanadium-chromium co-extraction process, the vanadium slag is leached by the circulating liquid containing sodium chromate, and Na in the circulating liquid containing sodium chromate₂CrO₄Easy to be reduced into Cr (III) and then generate inverse spinel (Mn) which is difficult to be reversely decomposed_0.87,Fe_0.13)(Mn_0.13,Fe_0.87,Cr)O₄Adding a pre-oxidation step, and adding CrO in the solution at a temperature below 120 DEG C₂ ^-Complete oxidation to CrO₄ ^2-As shown in formula (6), it can consume the substrate CrO for generating inverse spinel in advance₂ ^-So that stable inverse spinel (Mn) can not be generated at the vanadium-chromium co-extraction reaction temperature_0.87,Fe_0.13)(Mn_0.13,Fe_0.87,Cr)O₄Thereby inhibiting the generation of inverse spinel, further ensuring the smooth proceeding of the reactions (7) to (8) and realizing the high-efficiency extraction of vanadium and chromium in the vanadium slag.

Through the steps, the problem of reduction of sodium chromate in the circulating liquid in the high-efficiency vanadium-chromium co-extraction process of the sodium chromate circulating alkali medium liquid-phase oxidized vanadium slag is solved, and the purpose of co-extraction of vanadium and chromium in the vanadium slag by adopting the sodium chromate circulating liquid is realized.

According to the invention, the vanadium slag in the step (1) is vanadium slag formed in the production processes of carrying out blast furnace or direct reduction on vanadium-containing pig iron (water) produced by vanadium-titanium magnetite, and carrying out vanadium extraction by using oxygen or air as an oxidation medium under high temperature conditions through shaking a bag, carrying out vanadium extraction by using a foundry ladle, carrying out vanadium extraction by using a top-blown converter or a top-bottom combined blown converter and the like.

Preferably, the circulating solution containing sodium chromate in the step (1) comprises alkali.

Preferably, the base is sodium hydroxide.

Preferably, the alkali concentration in the circulating solution containing sodium chromate in the step (1) is 30-60 wt%, for example, 30 wt%, 35 wt%, 40 wt%, 45 wt%, 50 wt%, 55 wt% or 60 wt%.

Preferably, the circulating liquid containing sodium chromate in the step (1) comprises Na₂CrO₄。

Preferably, Na in the circulating liquid containing sodium chromate₂CrO₄The concentration is 0.01 to 15 wt%, and may be, for example, 0.01 wt%, 0.1 wt%, 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, 12 wt%, 14 wt%, or 15 wt%.

Preferably, the circulating liquid containing sodium chromate in the step (1) also comprises Na₃VO₄And/or Na₂SiO₃。

Preferably, Na in the circulating liquid containing sodium chromate₃VO₄The concentration is 0 to 5 wt%, and may be, for example, 0 wt%, 0.5 wt%, 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt%, 3.5 wt%, 4 wt%, 4.5 wt%, or 5 wt%.

Preferably, Na in the circulating liquid containing sodium chromate₂SiO₃The concentration is 0 to 3 wt%, and may be, for example, 0 wt%, 0.5 wt%, 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, or 3 wt%.

The sodium chromate-containing circulating liquid in the step (1) at least comprises NaOH and Na₂CrO₄And may also include Na₃VO₄And/or Na₂SiO₃And returning the alkaline solution including the sodium salt from the system for reacting with the vanadium slag to realize vanadium-chromium co-extraction.

Preferably, the mass ratio of sodium hydroxide to vanadium slag in the circulating liquid containing sodium chromate in the step (1) is 1-20: 1, and may be, for example, 1:1, 2:1, 5:1, 8:1, 10:1, 12:1, 14:1, 15:1, 16:1, 18:1 or 20: 1.

Preferably, the temperature of the pre-oxidation reaction in the step (2) is 20 to 120 ℃, and may be, for example, 20 ℃, 30 ℃, 40 ℃, 50 ℃, 60 ℃, 70 ℃, 80 ℃, 90 ℃, 95 ℃, 110 ℃ or 120 ℃.

The temperature of the preoxidation reaction is controlled to be 20-120 ℃, and CrO in the circulating liquid can be better guaranteed₂ ^-Complete oxidation to CrO₄ ^2-Preventing generation of inverse spinel and improving the vanadium-chromium co-extraction effect.

Preferably, the oxygen pressure of the pre-oxidation reaction is not less than 0.5MPa, for example, 0.5MPa, 0.8MPa, 1MPa, 1.2MPa, 1.5MPa, 1.8MPa, 2.0MPa, 2.2MPa, 2.5MPa, 2.8MPa or 3.0MPa, and preferably 0.5 to 2 MPa.

The oxygen pressure in the present invention means the partial pressure of oxygen, and if the oxidizing gas is air, the partial pressure of oxygen needs to be 0.5MPa or more, and if the oxidizing gas is pure oxygen, the system pressure may be 0.5MPa or more.

The system controls the temperature and the oxygen partial pressure, wherein the oxygen partial pressure is 0.5-2 MPa, and CrO is promoted₂ ^-And preventing CrO in the circulating liquid by controlling the process conditions₂ ^-Inverse spinel is generated, and the co-extraction of vanadium and chromium in the vanadium slag is promoted.

Preferably, the reaction time of the pre-oxidation reaction is not less than 0.5h, for example, 0.5h, 0.8h, 1.0h, 1.2h, 1.5h, 2.0h, 2.5h, 3h, 3.5h, 4h, 8h or 10h, and the like, preferably 0.5 to 3 h.

Preferably, the pre-oxidation reaction does not produce inverse spinel (Mn)_0.87,Fe_0.13)(Mn_0.13,Fe_0.87,Cr)O₄。

Preferably, the pre-oxidation reaction in step (2) is carried out in an oxidizing gas.

Preferably, the oxidizing gas comprises oxygen and/or air.

Preferably, the vanadium-chromium co-extraction reaction in the step (3) comprises a pressurization reaction or an aeration reaction.

Preferably, the temperature of the vanadium-chromium co-extraction reaction is 125-400 ℃, and can be, for example, 125 ℃, 130 ℃, 150 ℃, 180 ℃, 200 ℃, 220 ℃, 250 ℃, 280 ℃, 300 ℃, 320 ℃, 350 ℃ or 380 ℃ and the like.

Preferably, after the step (3), the method further comprises the following steps: and crystallizing the vanadium-chromium-containing leaching solution by using sodium vanadate and sodium chromate to respectively obtain sodium vanadate and sodium chromate products.

According to the present invention, after the pre-oxidation reaction in step (3) is completed, the reaction slurry is raised to the vanadium-chromium co-extraction reaction temperature, and the high efficiency co-extraction of vanadium and chromium from vanadium slag can be achieved by using the same pressure reaction conditions as in CN102531056B or the same aeration reaction conditions as in CN 105400967B. And then, the sodium vanadate and sodium chromate products can be obtained through the processes of solid-liquid separation, impurity removal, sodium vanadate crystallization, sodium chromate crystallization and the like.

Preferably, the circulating solution containing sodium chromate in the step (1) comprises a crystallization mother solution obtained by crystallizing sodium vanadate and crystallizing sodium chromate in the leaching solution containing vanadium and chromium in the step (3).

The circulating solution containing sodium chromate of the invention is crystallization mother liquor after sodium vanadate crystallization and sodium chromate crystallization, and the circulating solution containing sodium chromate also contains substances such as added sodium hydroxide solution or sodium hydroxide solid, etc., so as to improve the concentration of sodium hydroxide in the circulating solution.

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

(1) mixing the vanadium slag and the sodium chromate circulating liquid to obtain a reaction liquid, wherein the alkali concentration in the sodium chromate circulating liquid is 30-60 wt%, and Na is contained in the sodium chromate circulating liquid₂CrO₄0.01 to 15 wt% of Na₃VO₄0 to 5 wt% of Na₂SiO₃The concentration is 0-3 wt%; the mass ratio of sodium hydroxide to vanadium slag in the sodium chromate-containing circulating liquid is 1-20: 1;

(2) carrying out pre-oxidation reaction on the reaction solution in the step (1) in oxidizing gas at the temperature of less than or equal to 120 ℃ and the oxygen pressure of more than or equal to 0.5MPa for more than or equal to 0.5h to obtain pre-oxidation solution;

(3) heating the pre-oxidation solution obtained in the step (2) to 125-400 ℃, carrying out vanadium-chromium co-extraction reaction, and carrying out solid-liquid separation to obtain tailings and a vanadium-chromium-containing leaching solution;

and (2) crystallizing the vanadium-chromium-containing leaching solution and sodium chromate to obtain crystallized mother liquor, wherein the sodium chromate-containing circulating liquor obtained in the step (1) comprises crystallized mother liquor obtained by crystallizing sodium vanadate and crystallizing sodium chromate in the step (3).

The solid-liquid separation process is not particularly limited in the present invention, and any means or device for solid-liquid separation known to those skilled in the art may be used, for example, a solid-liquid separation means such as filtration, sedimentation, or centrifugation.

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

(1) the method for inhibiting the reduction of the sodium chromate in the circulating liquid in the vanadium slag vanadium-chromium co-extraction process adopts the circulating liquid to carry out liquid-phase oxidation reaction, can realize the internal circulation of a process liquid-phase medium and the effective utilization of NaOH in the process liquid-phase medium, and is clean and environment-friendly;

(2) the method for inhibiting the reduction of the sodium chromate in the circulating liquid in the vanadium slag vanadium-chromium co-extraction process increases a pre-oxidation step, strictly controls the pre-oxidation temperature to be below 120 ℃, and cooperatively adopts high oxygen pressure reaction, so that the problem of difficult reversion of a reaction product inverse spinel structure phase in the reaction process of a circulating medium and the vanadium slag is solved, the reduction of sodium chromate is inhibited, and the purpose of realizing the co-extraction of the vanadium and the chromium in the vanadium slag by adopting the sodium chromate circulating liquid is realized;

(3) the method for inhibiting the reduction of the sodium chromate in the circulating liquid in the vanadium slag vanadium-chromium co-extraction process has high conversion rate of vanadium and chromium even if the circulating liquid is adopted, wherein the conversion rate of vanadium is up to more than 88 wt%, and the conversion rate of chromium is up to more than 80 wt%.

Detailed Description

For the purpose of facilitating an understanding of the present invention, the present invention will now be described by way of examples. It should be understood by those skilled in the art that the examples are only for the understanding of the present invention and should not be construed as the specific limitations of the present invention.