WO2021120280A1 - Dynamic and static-combined stirring system and process for preparing chromium salt by chromite liquid phase oxidation - Google Patents

Abstract

A dynamic and static-combined stirring system, comprising a stirrer (1), and further comprising a plurality of static stirring paddles (12) arranged parallel to a stirring shaft (2) of the stirrer (1), wherein the plurality of static stirring paddles (12) are arranged around the stirring shaft (2), and a stirring blade (4) is installed at the bottom part of the stirring shaft (2). The dynamic and static-combined stirring system is used to carry out a process for preparing a chromium salt by chromite liquid phase oxidation, and the chromite liquid phase oxidation method is used to prepare the chromium salt, which solves the key process problems of solid-liquid separation during a chromite leaching process, the separation of chromium salts in high-alkali media, and the conversion of intermediate products into a series of chromium salts, and has great industrial application prospects.

Description

Dynamic and static combined stirring system and process for preparing chromium salt by liquid phase oxidation of chromite Technical field

The invention belongs to the technical field of hydrometallurgy and multiphase stirring reaction, and specifically relates to a dynamic and static combined stirring system and a process for preparing chromium salt by liquid-phase oxidation of chromite.

Background technique

Chromium salt is an important inorganic chemical product. my country is the largest country in the production of chromium salt, with an annual output of 400,000 tons. Traditional chromium salt production technology, especially calcium roasting technology, has been completely eliminated due to low resource utilization and a large amount of toxic chromium slag containing Cr(VI). At present, the calcium-free roasting process is commonly used in the chromium salt industry. Although the amount of chromium slag produced is greatly reduced, it still fails to completely solve the pollution problem of chromium slag. For this reason, the research and development of chromium salt cleaner production technology has attracted great attention from all walks of life. Among them, chromite liquid phase oxidation method, also known as chromite alkaline leaching method, is considered to be a clean process with great industrial application prospects.

CN201010146648 proposes a method for producing sodium chromate by alkaline leaching of chromite, which is a relatively complete clean production process of chromite at present, but the disadvantage of this process is that the reaction temperature in the alkaline leaching process is relatively high (180℃～320 ℃); After leaching, it is diluted with a large amount of water and then solid-liquid separation, which greatly dilutes the concentration of unreacted alkali, and seriously affects the recycling of alkali in leaching; the use of calcium oxide to remove aluminum causes calcium-containing waste residue Accumulation, serious environmental pollution problems; the crude sodium chromate product separated from chromium/alkali is not easy to obtain pure product by evaporation crystallization process, and it consumes energy and time.

technical problem

In the actual production and application of chromium salt, there are still the following main technical problems: (1) The reaction system formed by high-concentration alkali and stable chromite ore is complicated, which leads to low chromium conversion efficiency in the process, and requires the transfer of the reaction system. The quality process is strengthened; (2) In order to achieve high efficiency chromium conversion rate, the amount of alkali is extremely large, the later recovery is difficult and the process is complicated; (3) The alkali concentration of the alkaline leaching solution is large, and the particle size of the reaction residue is small, which makes solid-liquid separation difficult; (4) It is difficult to separate the chromium salt and alkali in the leachate, and the obtained chromium salt contains a large amount of alkali, and the later purification process is complicated.

The solution to the problem

Technical solutions

The technical problem to be solved by the present invention is to provide a dynamic and static combined mixing system in view of the above-mentioned shortcomings of the prior art. The system is simple in structure and reasonable in design. Under the stirring action of the stirrer, the reaction fluid in the stirring tank rotates and flows and mixes, and a rotating body centered on the stirring shaft is formed during stable operation. The formation of the rotating body is not conducive to the mixing of the components in the fluid. The present invention By installing multiple static stirring paddles, the original stable fluid rotating body is hindered and the symmetry of the original stable flow field is destroyed, so that the fluid rotates and splits, causing the fluid interface to be unstable, thereby realizing the fluid mixing in the flow field. The adjustment of the process achieves the purpose of enhancing the mass transfer of fluid mixing.

In order to solve the above technical problems, the technical solution adopted by the present invention is: a dynamic and static mixing system, including a stirrer, characterized in that it also includes a plurality of static stirring paddles arranged in parallel with the stirring shaft of the agitator, and a plurality of The static stirring blade is arranged around the stirring shaft, and a stirring blade is installed at the bottom of the stirring shaft.

The above-mentioned combined dynamic and static stirring system is characterized in that the distances between the plurality of static stirring paddles and the stirring shaft are all unequal.

The above-mentioned combined dynamic and static stirring system is characterized in that the static stirring paddle is a slat-shaped stirring paddle, a cylindrical stirring paddle or a prismatic stirring paddle.

The above-mentioned combined dynamic and static stirring system is characterized in that, with the stirring shaft of the stirrer as the center, the ratio of the installation radius of the static stirring paddle to the radius of the container used for stirring is 1:7.5 to 1:16.

In addition, the present invention also provides a process for preparing chromium salt by liquid-phase oxidation of chromite by using the above-mentioned dynamic and static mixing system, which is characterized in that it includes:

Add chromite, sodium hydroxide and water into the autoclave equipped with a dynamic and static mixing system. Under agitation, oxygen is introduced into the autoclave for liquid phase oxidation. After the reaction, the pressure is released and cooled, and then the The materials in the high-pressure reactor are transferred to the thermostat for heat preservation and sedimentation, and solid-liquid separation of the materials after heat preservation and sedimentation is carried out to obtain the supernatant liquid and the reaction residue;

Separating the reaction slag after countercurrent washing to obtain washing slag liquid and iron slag;

Adding barium hydroxide to the supernatant to perform a precipitation reaction, after the reaction is completed, barium chromate precipitate A and aluminum-containing lye B are obtained separately;

Adding barium hydroxide to the washing slag solution for precipitation reaction, after the reaction is finished, barium chromate precipitation C and aluminum-containing lye D are obtained separately;

The barium chromate precipitate A and the barium chromate precipitate C are dissolved in hydrochloric acid, and then a reducing agent is added to reduce the reaction to obtain a mixed solution of chromium chloride and barium chloride. The pH value of the mixed solution is adjusted so that the chromium is replaced with hydrogen. The form of chromium oxide is completely precipitated, and solid-liquid separation is used to obtain chromium hydroxide product.

The above method is characterized in that the reaction temperature of the liquid phase oxidation reaction is 180° C. to 270° C., the oxygen partial pressure is 1.2 MPa to 2.6 MPa, the stirring speed is 500 rpm to 900 rpm, and the reaction time is 1 h to 5 h.

The above method is characterized in that the mass ratio of sodium hydroxide and chromite is (2-5):1, and the mass of sodium hydroxide is 30% to 60% of the total mass of sodium hydroxide and water.

The above method is characterized in that the temperature of the heat preservation and sedimentation is 70°C to 150°C, and the time is 120min to 210min.

The above method is characterized in that when barium hydroxide is added to the supernatant liquid for precipitation reaction, the molar ratio of barium hydroxide to sodium chromate in the supernatant liquid is (1～1.2):1, and the reaction time is 1h～2h, reaction temperature 60～80℃;

When barium hydroxide is added to the washing residue for precipitation reaction, the molar ratio of barium hydroxide to sodium chromate in the washing residue is (1～1.2):1, the reaction time is 1h～2h, and the reaction temperature is 60～ 80°C.

The above method is characterized in that it further comprises adding sodium silicate slurry to the aluminum-containing lye D to perform a precipitation reaction, and after the reaction is completed, a low-aluminum lye and sodium aluminosilicate precipitation are obtained separately.

The above method is characterized in that the molar ratio of the sodium silicate to the sodium aluminate in the aluminum-containing lye D is (1 to 1.2):1.

The above-mentioned method is characterized in that it further comprises the step of returning the separated low-aluminum lye to the high-pressure reactor for recycling after supplementing alkali.

The above method is characterized in that it also includes returning the aluminum-containing lye B to the autoclave for recycling.

The above method is characterized in that the ratio of the sum of the amount of the barium chromate precipitate A and the amount of the barium chromate precipitate C to the amount of HCl in the hydrochloric acid is 1: (2-5), and the volume of the hydrochloric acid is The mass of barium chromate precipitate A and barium chromate precipitate C is 4 to 8 times the mass, where the unit of volume is mL and the unit of mass is g. The reducing agent is a small molecular alcohol organic substance, and the molar amount of the reducing agent is The theoretical reaction with barium chromate is 1 to 5 times the molar amount.

The above method is characterized in that the stirring speed of the reduction reaction is 200 rpm to 400 rpm, the reaction temperature is 50°C to 80°C, and the reaction time is 1 h to 2 h.

The above method is characterized in that barium hydroxide is used to adjust the pH value of the mixed solution to 8-9 after the reduction reaction.

The above method is characterized in that it also includes adding sulfuric acid to the liquid phase obtained by solid-liquid separation after the chromium is completely precipitated in the form of chromium hydroxide until the barium precipitation is complete, to obtain a barium sulfate product.

The beneficial effects of the invention

Beneficial effect

Compared with the prior art, the present invention has the following advantages:

1. The mixing system of the present invention has a simple structure and a reasonable design. Under the stirring action of the stirrer, the reaction fluid in the stirring tank rotates and flows and mixes, and a rotating body centered on the stirring shaft is formed during stable operation. The formation of the rotating body is not conducive to the mixing of the components in the fluid. The present invention By installing multiple static stirring paddles, the original stable fluid rotating body is hindered and the symmetry of the original stable flow field is destroyed, so that the fluid rotates and splits, causing the fluid interface to be unstable, thereby realizing the fluid mixing in the flow field. The adjustment of the process achieves the purpose of enhancing the mass transfer of fluid mixing.

2. Adopting the dynamic and static mixing system of the present invention can significantly increase the chromium conversion rate in the liquid phase oxidation of chromite, greatly reduce the reaction time, and realize a fast and efficient chromium salt clean production method.

3. The present invention proposes a new process route for preparing chromium salt by liquid phase oxidation of chromite, which innovatively solves the solid-liquid separation of chromite leaching process, the separation of chromium salt in high alkali medium, and the conversion of intermediate products. It is a key process problem of the series of chromium salts and has great industrial application prospects.

4. In the liquid phase oxidation leaching process of chromite ore, the present invention proposes to adopt a high-pressure reactor equipped with a dynamic and static mixing paddle, so that the air phase in the upper part of the reactor is changed from the original single-region entrained mixing mode to multi-regional, The multiple mixing mode of multi-site entrainment greatly strengthens the gas-liquid-solid three-phase mass transfer process in the reaction system and improves the efficiency of the leaching reaction process.

5. The present invention innovatively proposes the insulation and sedimentation separation process of the oxidation leaching system of chromite in a high-alkali medium, which solves the problem of solid-liquid separation. Compared with traditional methods such as dilution filtration and centrifugation, it significantly reduces the solid-liquid separation time and equipment investment cost, and can always keep the aluminum content in the supernatant liquid low, the alkali content is high, the aluminum content in the slag washing liquid is high, and the alkali content is low. It is conducive to the subsequent circulation and aluminum removal process, while retaining the original lye concentration to the greatest extent, greatly improving the efficiency of the direct recycling of the medium.

6. The present invention proposes a new process for separating chromium salt directly from the chromite leaching solution by using the barium salt method, and a new process for converting barium chromate into chromium salt. Innovatively realize the separation of chromium-alkali. A dissolution-reduction method of barium chromate with hydrochloric acid-organic matter as the system was proposed, which achieved the goal of preparing a series of chromium salts from barium chromate. At the same time, the recycling of hydrochloric acid medium is realized, and pure barium sulfate products can be obtained. The reaction conditions of the process are mild, green and efficient.

7. The present invention innovatively proposes a new process for removing aluminum from the chromite leaching solution in the lye after chromium-alkali separation. That is, sodium silicate is used as a precipitant and added to the lye to directly convert the sodium aluminate precipitation into sodium aluminosilicate. Further processing can obtain the by-product of sodium aluminosilicate molecular sieve with higher economic value, and the lye can be directly recycled In the leaching reaction step, it can improve economy and reduce energy consumption.

Brief description of the drawings

Description of the drawings

Figure 1 is a schematic diagram of the structure of the dynamic and static combined stirring system of the present invention.

Figure 2 is a schematic diagram of the flow field when a single dynamic stirring blade is working (Y=0 front view).

Fig. 3 is a schematic diagram of the flow field when a single dynamic stirring blade is working (Z=0 top view).

Fig. 4 is a schematic diagram of the working time field of the dynamic and static mixing system of the present invention (Y=0 front view).

Fig. 5 is a schematic diagram of the working time field of the dynamic and static mixing system of the present invention (Z=0 top view).

Fig. 6 is a diagram showing the relationship between the chromium leaching rate and the leaching time of chromite liquid phase oxidation method for preparing chromium salt using a single dynamic stirring blade and the combined dynamic and static stirring system of the present invention.

Fig. 7 is a schematic diagram of the structure of a high pressure reactor equipped with a dynamic and static mixing system according to the present invention.

Fig. 8 is a schematic diagram of the process flow of the present invention.

The best embodiment for implementing the invention

The best mode of the present invention

As shown in Figure 1, the dynamic and static mixing system of the present invention includes a stirrer 1, and also includes a plurality of static stirring paddles 12 arranged in parallel with the stirring shaft 2 of the stirrer 1, and the plurality of static stirring paddles 12 surround The stirring shaft 2 is provided, and a stirring blade 4 is installed at the bottom of the stirring shaft 2.

In this embodiment, the distances between the plurality of static stirring paddles 12 and the stirring shaft 2 are all unequal. The number of the static stirring blades 12 can be 2, 3, 4, 5, 6, and so on.

In this embodiment, the static stirring paddle 12 is a slat-shaped stirring paddle, a cylindrical stirring paddle or a prismatic stirring paddle.

In this embodiment, with the stirring shaft 2 of the stirrer 1 as the center of the circle, the ratio of the installation radius of the static stirring paddle 12 to the radius of the container used for stirring is 1:7.5 to 1:16.

The specific working principle of the dynamic and static combined stirring system of the present invention is: the reaction system (such as solid-liquid, gas-liquid, liquid-liquid, gas-liquid-solid, etc.) under the stirring action of a stirrer, the reaction fluid rotates and mixes, During stable operation, a rotating body with the stirring shaft as the center is formed (as shown in Figures 2 and 3). The formation of the rotating body is not conducive to the mixing of the components in the fluid, but due to the static stirring paddle located in the flow field The existence of, the original stable fluid rotating body is hindered, destroying the symmetry of the original stable flow field, so that the fluid revolves and splits (as shown in Figure 4 and Figure 5), causing the fluid interface to be unstable, thus achieving The control of the fluid mixing process in the flow field achieves the purpose of enhancing the mass transfer of fluid mixing.

The dynamic and static combined stirring system of the present invention is applied to a gas-liquid-solid three-phase mixed mass transfer reaction system. Under the action of the dynamic and static combined stirring system, the gas above the stirring tank enters the solid-liquid two-phase in the container through the entrainment effect of stirring. Participate in the reaction in the system, and the gas phase has changed from the original mixing mode of entrainment in the flow field around the single dynamic agitator to the multiple mixing mode of the flow field around the dynamic agitator and the small flow field area near the multiple static stirring paddles, greatly increasing The gas-liquid-solid three-phase mass transfer area of the reaction system enhances the mass transfer between the phases. The acceleration of gas-liquid-solid three-phase mass transfer helps reduce the reaction time of the system. Aiming at the liquid-phase oxidation process of chromite, it is more helpful to reduce the concentration of reaction alkali and other process conditions, which improves the conversion rate of chromium and reduces energy consumption. Therefore, the combined dynamic and static stirring system helps to strengthen the mixing of the fluid in the stirred tank, enhance the entrainment of the gas phase in the gas-liquid-solid three-phase reaction, and increase the mass transfer rate between the phases in the reaction system. It can be used for various based The fluid mixing system of the stirred tank is especially suitable for the multiphase reaction system involving the solid structure that is stable and difficult to decompose. In addition, the system also has the characteristics of simple structure, low energy and high rate, low cost, and easy repair.

As shown in Figure 7, the high-pressure reaction vessel equipped with a dynamic and static mixing system used in the present invention includes a high-pressure reaction vessel 8 with an opening at the top, and a sealing cover 3 arranged at the opening of the high-pressure reaction vessel 8. A stirrer 1 is installed, the stirring shaft 2 of the stirrer 1 is located in the high-pressure reactor 8, the bottom of the stirring shaft 2 is equipped with a stirring blade 4, and the sealing cover 3 is fixedly installed with a plurality of static stirring blades 12, The static stirring blade 12 is arranged around the stirring shaft 2, and one end of the plurality of static stirring blades 12 away from the sealing cover 3 penetrates into the high pressure reactor 8.

In this embodiment, the distances between the plurality of static stirring paddles 12 and the stirring shaft 2 are all unequal. The number of the static stirring blades 12 can be 2, 3, 4, 5, 6, and so on.

In this embodiment, the static stirring paddle 12 is a slat-shaped stirring paddle, a cylindrical stirring paddle, or a prismatic stirring paddle.

In this embodiment, a thermocouple 7 is installed on the sealing cover 3.

In this embodiment, the lower end of the static stirring blade 12 is located above the stirring blade 4.

In this embodiment, the blades of the stirring blade 4 are ellipsoidal.

In this embodiment, the sealing cover 3 is provided with an air inlet and an air outlet, and an air inlet pipe 9 is installed on the air inlet. The air inlet pipe 9 penetrates into the high pressure reactor 8 and the bottom of the air inlet pipe 9 is close to the high pressure reactor 8 An air inlet valve 5 is installed on the top of the air inlet pipe; an air outlet pipe is installed on the air outlet, and an air outlet valve 11 is installed on the top of the air outlet pipe.

In this embodiment, a pressure gauge 10 for detecting the pressure in the high-pressure reactor 8 is installed on the sealing cover 3.

In this embodiment, a heating jacket 6 is provided on the outside of the high-pressure reactor 8, and a groove for placing the high-pressure reactor 8 is opened in the middle of the heating jacket 6.

In this embodiment, a base 13 is provided at the bottom of the heating jacket 6.

The high-pressure reactor equipped with a single dynamic stirring blade and the high-pressure reactor equipped with the dynamic and static combined stirring system of the present invention are used to prepare chromite by the liquid phase oxidation method of chromite ore respectively. The South African chromite powder is taken and ground to 300 mesh ( _{48μm), the content of Cr 2} O ₃ is about 42.92% as measured by X-ray fluorescence spectrometer (XRF). Take 125g of chromite powder (300 mesh), 500g of sodium hydroxide and 333mL of deionized water respectively, and mix them into the autoclave at a temperature of 250℃, an oxygen partial pressure of 2.4MPa (total pressure of about 3.2MPa), and a reaction time setting Under the conditions of 60min, 120min, 180min, 240min, 300min, the experiment was carried out with a high-pressure reactor equipped with a single dynamic stirring blade and a high-pressure reactor equipped with the dynamic and static combined stirring system of the present invention to determine the leachate after the liquid phase oxidation reaction. Medium chromium content. The chromium leaching rate of the two high-pressure reactors varies with the reaction time as shown in Figure 7. After the reaction in the high-pressure reactor using only a single dynamic stirring blade, the maximum chromium leaching rate in the leaching solution is only 90%, and it takes 300 minutes. It takes a long time; and after the reaction in the high-pressure reactor of the dynamic and static combined stirring system, the chromium leaching rate has reached 99% in only 240 minutes. And in a short time of 60min～120min, the chromium leaching rate in the dynamic and static combined stirring system is about 2 times higher than the former. The dynamic and static combined stirring system of the present invention realizes the high-efficiency leaching of the chromite liquid phase oxidation method in a short time, and at the same time greatly improves the chromium leaching rate, avoids secondary recovery and resource waste, and the strengthening method of dynamic and static combination effectively improves the transmission in the system. It is suitable for all kinds of multi-phase reaction systems, and belongs to a new type of device that enhances multi-phase mass transfer with high efficiency.

The process for preparing chromium salt by liquid-phase oxidation of chromite using the high-pressure reactor equipped with a dynamic and static mixing system includes:

125g of chromite (300 mesh), 250g of sodium hydroxide and 583g of water were added to the high pressure reactor equipped with a dynamic and static mixing system; under stirring conditions, oxygen was introduced into the high pressure reactor for liquid phase oxidation reaction. The reaction temperature of the oxidation reaction is 180℃, the oxygen partial pressure is 1.2MPa (total pressure is about 2.4MPa), the stirring speed is 500rpm, and the reaction time is 1h; after the reaction, the pressure is released and cooled, and then the materials in the autoclave are transferred to a constant temperature The temperature of the heat preservation and sedimentation in the box is 70℃, and the time is 120min; the solid-liquid separation of the materials after the heat preservation and sedimentation is carried out to obtain the supernatant liquid and the reaction slag;

The reaction slag is washed countercurrently with water and then separated to obtain washing slag liquid and iron slag;

Industrial sodium chromate (HG/T 4312-2012) was used to determine the content of sodium chromate in the supernatant liquid and the washing residue liquid; the supernatant liquid contained 11.43g sodium chromate and 1.45g sodium metaaluminate. ; Measured that the washing residue liquid contains 22.87g of sodium chromate and 8.68g of sodium metaaluminate;

According to the molar ratio of barium hydroxide to sodium chromate in the supernatant liquid of 1:1, 12.1 g of barium hydroxide was added to the supernatant liquid for precipitation reaction, the reaction time was 1 h, the reaction temperature was 60°C; after the reaction was completed Separate the barium chromate precipitate A and the aluminum-containing lye B; return the aluminum-containing lye B to the high-pressure reactor for recycling;

According to the molar ratio of barium hydroxide to sodium chromate in the washing residue solution of 1:1, 24.2g of barium hydroxide was added to the washing residue solution for precipitation reaction, the reaction time was 1h, and the reaction temperature was 60°C; after the reaction was completed Separation of barium chromate precipitate C and aluminum-containing lye D;

Use "GB/T 5750.6-2006 Standard Test Method for Drinking Water, Metal Index Chromazurol S Spectrophotometric Method" to determine the aluminum content in aluminum-containing lye D, according to the aluminum content in sodium silicate and aluminum-containing lye D The molar ratio of sodium is 1:1, 21.54g of sodium silicate water slurry with a mass concentration of 60% is added to the aluminum-containing lye D for precipitation reaction, the reaction time is 1h, the reaction temperature is 70°C; the reaction is complete After the separation, low-aluminum lye and sodium aluminosilicate precipitation are obtained, and the aluminum removal rate reaches 90%, which meets the recycling standard; the separated low-aluminum lye is returned to the high-pressure reactor for recycling;

Combine the barium chromate precipitate A and barium chromate precipitate C, and the chromium conversion rate is determined to be 90%; the combined barium chromate is dissolved in a hydrochloric acid solution, and the liquid-to-solid ratio is 8:1 (mL:g). The molar ratio of barium chromate to HCl in the hydrochloric acid solution is 1:2. After dissolution, the measured chromium dissolution rate is 92%. Then a reducing agent is added to carry out the reduction reaction. The stirring speed of the reduction reaction is 200 rpm, and the reaction temperature is 50°C. The time is 1h, the reducing agent is a small molecule alcoholic organic substance ethanol, and the molar amount of the reducing agent is 1 times the theoretical reaction molar amount with barium chromate to obtain a mixed solution of chromium chloride and barium chloride. The reduction rate of chromium is 72%; barium hydroxide is used to adjust the pH value of the mixed solution of chromium chloride and barium chloride to 8, so that chromium is completely precipitated in the form of chromium hydroxide, and the solid-liquid separation obtains the chromium hydroxide product. After centrifugal separation Dilute sulfuric acid is added to the liquid phase until the barium precipitation is complete, and a pure barium sulfate product is obtained.

Invention embodiment

Embodiments of the present invention

Example 1

As shown in Figure 1, the dynamic and static mixing system of the present invention includes a stirrer 1, and also includes a plurality of static stirring paddles 12 arranged in parallel with the stirring shaft 2 of the stirrer 1, and the plurality of static stirring paddles 12 surround The stirring shaft 2 is provided, and a stirring blade 4 is installed at the bottom of the stirring shaft 2.

In this embodiment, the distances between the plurality of static stirring paddles 12 and the stirring shaft 2 are all unequal. The number of the static stirring blades 12 can be 2, 3, 4, 5, 6, and so on.

In this embodiment, the static stirring paddle 12 is a slat-shaped stirring paddle, a cylindrical stirring paddle or a prismatic stirring paddle.

In this embodiment, with the stirring shaft 2 of the stirrer 1 as the center of the circle, the ratio of the installation radius of the static stirring paddle 12 to the radius of the container used for stirring is 1:7.5 to 1:16.

The specific working principle of the dynamic and static combined stirring system of the present invention is: the reaction system (such as solid-liquid, gas-liquid, liquid-liquid, gas-liquid-solid, etc.) under the stirring action of a stirrer, the reaction fluid rotates and mixes, During stable operation, a rotating body with the stirring shaft as the center is formed (as shown in Figures 2 and 3). The formation of the rotating body is not conducive to the mixing of the components in the fluid, but due to the static stirring paddle located in the flow field The existence of, the original stable fluid rotating body is hindered, destroying the symmetry of the original stable flow field, so that the fluid revolves and splits (as shown in Figure 4 and Figure 5), causing the fluid interface to be unstable, thus achieving The control of the fluid mixing process in the flow field achieves the purpose of enhancing the mass transfer of fluid mixing.

The dynamic and static combined stirring system of the present invention is applied to a gas-liquid-solid three-phase mixed mass transfer reaction system. Under the action of the dynamic and static combined stirring system, the gas above the stirring tank enters the solid-liquid two-phase in the container through the entrainment effect of stirring. Participate in the reaction in the system, and the gas phase has changed from the original mixing mode of entrainment in the flow field around the single dynamic agitator to the multiple mixing mode of the flow field around the dynamic agitator and the small flow field area near the multiple static stirring paddles, greatly increasing The gas-liquid-solid three-phase mass transfer area of the reaction system enhances the mass transfer between the phases. The acceleration of gas-liquid-solid three-phase mass transfer helps reduce the reaction time of the system. Aiming at the liquid-phase oxidation process of chromite, it is more helpful to reduce the concentration of reaction alkali and other process conditions, which improves the conversion rate of chromium and reduces energy consumption. Therefore, the combined dynamic and static stirring system helps to strengthen the mixing of the fluid in the stirred tank, enhance the entrainment of the gas phase in the gas-liquid-solid three-phase reaction, and increase the mass transfer rate between the phases in the reaction system. It can be used for various based The fluid mixing system of the stirred tank is especially suitable for the multiphase reaction system involving the solid structure that is stable and difficult to decompose. In addition, the system also has the characteristics of simple structure, low energy and high rate, low cost, and easy repair.

Example 2

As shown in Figure 7, the high-pressure reaction vessel equipped with a dynamic and static mixing system used in the present invention includes a high-pressure reaction vessel 8 with an opening at the top, and a sealing cover 3 arranged at the opening of the high-pressure reaction vessel 8. A stirrer 1 is installed, the stirring shaft 2 of the stirrer 1 is located in the high-pressure reactor 8, the bottom of the stirring shaft 2 is equipped with a stirring blade 4, and the sealing cover 3 is fixedly installed with a plurality of static stirring blades 12, The static stirring blade 12 is arranged around the stirring shaft 2, and one end of the plurality of static stirring blades 12 away from the sealing cover 3 penetrates into the high pressure reactor 8.

In this embodiment, the distances between the plurality of static stirring paddles 12 and the stirring shaft 2 are all unequal. The number of the static stirring paddles 12 can be 2, 3, 4, 5, 6, and so on.

In this embodiment, the static stirring paddle 12 is a slat-shaped stirring paddle, a cylindrical stirring paddle, or a prismatic stirring paddle.

In this embodiment, a thermocouple 7 is installed on the sealing cover 3.

In this embodiment, the lower end of the static stirring blade 12 is located above the stirring blade 4.

In this embodiment, the blades of the stirring blade 4 are ellipsoidal.

In this embodiment, the sealing cover 3 is provided with an air inlet and an air outlet, and an air inlet pipe 9 is installed on the air inlet. The air inlet pipe 9 penetrates into the high pressure reactor 8 and the bottom of the air inlet pipe 9 is close to the high pressure reactor 8 An air inlet valve 5 is installed on the top of the air inlet pipe; an air outlet pipe is installed on the air outlet, and an air outlet valve 11 is installed on the top of the air outlet pipe.

In this embodiment, a pressure gauge 10 for detecting the pressure in the high-pressure reactor 8 is installed on the sealing cover 3.

In this embodiment, a heating jacket 6 is provided on the outside of the high-pressure reactor 8, and a groove for placing the high-pressure reactor 8 is opened in the middle of the heating jacket 6.

In this embodiment, a base 13 is provided at the bottom of the heating jacket 6.

The high-pressure reactor equipped with a single dynamic stirring blade and the high-pressure reactor equipped with the dynamic and static combined stirring system of the present invention are used to prepare chromite by the liquid phase oxidation method of chromite ore respectively. The South African chromite powder is taken and ground to 300 mesh ( _{48μm), the content of Cr 2} O ₃ is about 42.92% as measured by X-ray fluorescence spectrometer (XRF). Take 125g of chromite powder (300 mesh), 500g of sodium hydroxide and 333mL of deionized water respectively, and mix them into the autoclave at a temperature of 250℃, an oxygen partial pressure of 2.4MPa (total pressure of about 3.2MPa), and a reaction time setting Under the conditions of 60min, 120min, 180min, 240min, 300min, the experiment was carried out with a high-pressure reactor equipped with a single dynamic stirring blade and a high-pressure reactor equipped with the dynamic and static combined stirring system of the present invention to determine the leachate after the liquid phase oxidation reaction. Medium chromium content. The chromium leaching rate of the two high-pressure reactors varies with the reaction time as shown in Figure 7. After the reaction in the high-pressure reactor using only a single dynamic stirring blade, the maximum chromium leaching rate in the leaching solution is only 90%, and it takes 300 minutes. It takes a long time; and after the reaction in the high-pressure reactor of the dynamic and static combined stirring system, the chromium leaching rate has reached 99% in only 240 minutes. And in a short time of 60min～120min, the chromium leaching rate in the dynamic and static combined stirring system is about 2 times higher than the former. The dynamic and static combined stirring system of the present invention realizes the high-efficiency leaching of the chromite liquid phase oxidation method in a short time, and at the same time greatly improves the chromium leaching rate, avoids secondary recovery and resource waste, and the strengthening method of dynamic and static combination effectively improves the transmission in the system. It is suitable for all kinds of multi-phase reaction systems, and belongs to a new type of device that enhances multi-phase mass transfer with high efficiency.

Example 3

The process for preparing chromium salt by liquid-phase oxidation of chromite using the high-pressure reactor equipped with a dynamic and static mixing system described in Example 2 includes:

125g of chromite (300 mesh), 250g of sodium hydroxide and 583g of water were added to the high pressure reactor equipped with a dynamic and static mixing system; under stirring conditions, oxygen was introduced into the high pressure reactor for liquid phase oxidation reaction. The reaction temperature of the oxidation reaction is 180℃, the oxygen partial pressure is 1.2MPa (total pressure is about 2.4MPa), the stirring speed is 500rpm, and the reaction time is 1h; after the reaction, the pressure is released and cooled, and then the materials in the autoclave are transferred to a constant temperature Heat preservation and sedimentation in the box, the temperature of heat preservation and sedimentation is 70℃, and the time is 120min; the solid-liquid separation of the materials after the heat preservation and sedimentation is carried out to obtain the supernatant liquid and the reaction slag;

The reaction slag is washed countercurrently with water and then separated to obtain washing slag liquid and iron slag;

Industrial sodium chromate (HG/T 4312-2012) was used to determine the content of sodium chromate in the supernatant liquid and the washing residue liquid; the supernatant liquid contained 11.43g sodium chromate and 1.45g sodium metaaluminate. ; Measured that the washing residue liquid contains 22.87g of sodium chromate and 8.68g of sodium metaaluminate;

According to the molar ratio of barium hydroxide to sodium chromate in the supernatant liquid of 1:1, 12.1 g of barium hydroxide was added to the supernatant liquid for precipitation reaction, the reaction time was 1 h, the reaction temperature was 60°C; after the reaction was completed Separate the barium chromate precipitate A and the aluminum-containing lye B; return the aluminum-containing lye B to the high-pressure reactor for recycling;

According to the molar ratio of barium hydroxide to sodium chromate in the washing residue solution of 1:1, 24.2g of barium hydroxide was added to the washing residue solution for precipitation reaction, the reaction time was 1h, and the reaction temperature was 60°C; after the reaction was completed Separation of barium chromate precipitate C and aluminum-containing lye D;

Use "GB/T 5750.6-2006 Standard Test Method for Drinking Water, Metal Index Chromazurol S Spectrophotometric Method" to determine the aluminum content in aluminum-containing lye D, according to the aluminum content in sodium silicate and aluminum-containing lye D The molar ratio of sodium is 1:1, 21.54g of sodium silicate water slurry with a mass concentration of 60% is added to the aluminum-containing lye D for precipitation reaction, the reaction time is 1h, the reaction temperature is 70°C; the reaction is complete After separation, low-aluminum lye and sodium aluminosilicate precipitation are obtained, and the aluminum removal rate reaches 90%, which meets the recycling standard; the separated low-aluminum lye is returned to the high-pressure reactor for recycling;

Combine the barium chromate precipitate A and barium chromate precipitate C, and the chromium conversion rate is determined to be 90%; the combined barium chromate is dissolved in a hydrochloric acid solution, and the liquid-to-solid ratio is 8:1 (mL:g). The molar ratio of barium chromate to HCl in the hydrochloric acid solution is 1:2. After dissolution, the measured chromium dissolution rate is 92%. Then a reducing agent is added to carry out the reduction reaction. The stirring speed of the reduction reaction is 200 rpm, and the reaction temperature is 50°C. The time is 1h, the reducing agent is a small molecule alcoholic organic substance ethanol, and the molar amount of the reducing agent is 1 times the theoretical reaction molar amount with barium chromate to obtain a mixed solution of chromium chloride and barium chloride. The reduction rate of chromium is 72%; barium hydroxide is used to adjust the pH value of the mixed solution of chromium chloride and barium chloride to 8, so that chromium is completely precipitated in the form of chromium hydroxide, and the solid-liquid separation obtains the chromium hydroxide product. After centrifugal separation Dilute sulfuric acid is added to the liquid phase until the barium precipitation is complete, and a pure barium sulfate product is obtained.

Example 4

The process for preparing chromium salt by liquid-phase oxidation of chromite using the high-pressure reactor equipped with a dynamic and static mixing system described in Example 2 includes:

Add 125g of chromite (300 mesh), 500g of sodium hydroxide and 500g of water into the autoclave equipped with a dynamic and static mixing system; under agitation, oxygen is introduced into the autoclave for liquid phase oxidation. The reaction temperature of the oxidation reaction is 240℃, the oxygen partial pressure is 2.4MPa (total pressure is about 3.2MPa), the stirring speed is 800rpm, and the reaction time is 4h; after the reaction, the pressure is released and cooled, and then the materials in the autoclave are transferred to a constant temperature Heat preservation and sedimentation in the box, the temperature of heat preservation and sedimentation is 90℃, and the time is 180min; the solid-liquid separation of the materials after the heat preservation and sedimentation is carried out to obtain the supernatant liquid and the reaction residue;

The reaction slag is washed countercurrently with water and then separated to obtain washing slag liquid and iron slag;

Industrial sodium chromate (HG/T 4312-2012) was used to determine the content of sodium chromate in the supernatant liquid and the washing residue liquid; it was determined that the supernatant liquid contained 21.95g sodium chromate and 2.02g sodium metaaluminate ; Measured that the washing residue liquid contains 87.83g of sodium chromate and 25.17g of sodium metaaluminate;

According to the molar ratio of barium hydroxide to sodium chromate in the supernatant liquid of 1.1:1, 23.2g of barium hydroxide was added to the supernatant liquid for precipitation reaction, the reaction time was 1.5h, the reaction temperature was 70°C; the reaction was completed After separation, barium chromate precipitate A and aluminum-containing lye B are obtained; the aluminum-containing lye B is returned to the high-pressure reactor for recycling;

According to the molar ratio of barium hydroxide to sodium chromate in the washing residue solution of 1.1:1, 92.9g of barium hydroxide was added to the washing residue solution for precipitation reaction, the reaction time was 1.5h, the reaction temperature was 70°C; the reaction was completed After separation, barium chromate precipitate C and aluminum-containing lye D are obtained;

Use "GB/T 5750.6-2006 Standard Test Method for Drinking Water, Metal Index Chromazurol S Spectrophotometric Method" to determine the aluminum content in aluminum-containing lye D, according to the aluminum content in sodium silicate and aluminum-containing lye D The sodium molar ratio is 1.1:1, 46.85g of sodium silicate aqueous slurry with a mass concentration of 80% is added to the aluminum-containing lye D for precipitation reaction, the reaction time is 2h, the reaction temperature is 80°C; the reaction is completed After separation, low-aluminum lye and sodium aluminosilicate precipitation are obtained, and the aluminum removal rate reaches 92%, which meets the recycling standard; the separated low-aluminum lye is returned to the high-pressure reactor for recycling;

Combine barium chromate precipitation A and barium chromate precipitation C, and the chromium conversion rate is determined to be 94%; the combined barium chromate is dissolved in hydrochloric acid solution, and the liquid-to-solid ratio is 6:1 (mL:g). The molar ratio of barium chromate to HCl in the hydrochloric acid solution is 1:4. After dissolution, the chromium dissolution rate is measured to be 96%. Then, a reducing agent is added to perform the reduction reaction. The stirring speed of the reduction reaction is 300 rpm, and the reaction temperature is 80°C. The time is 1.5h, the reducing agent is a small-molecule alcoholic organic substance ethanol, and the molar amount of the reducing agent is 1 times the theoretical reaction molar amount with barium chromate to obtain a mixed solution of chromium chloride and barium chloride. The reduction rate of chromium is It is 96%; the pH value of the mixed solution of chromium chloride and barium chloride is adjusted to 8.5 with barium hydroxide, so that chromium is completely precipitated in the form of chromium hydroxide, and the solid-liquid separation obtains the chromium hydroxide product, which is separated by centrifugation Dilute sulfuric acid is added to the latter liquid phase until the barium precipitation is complete, and a pure barium sulfate product is obtained.

Example 5

The process for preparing chromium salt by liquid-phase oxidation of chromite using the high-pressure reactor equipped with a dynamic and static mixing system described in Example 2 includes:

Add 125g of chromite (300 mesh), 625g of sodium hydroxide and 416g of water into the autoclave equipped with a dynamic and static mixing system; under agitation, oxygen is introduced into the autoclave for liquid phase oxidation. The reaction temperature of the oxidation reaction is 270℃, the oxygen partial pressure is 2.6MPa (total pressure is about 3.5MPa), the stirring speed is 900rpm, and the reaction time is 5h; after the reaction, the pressure is released and cooled, and then the materials in the autoclave are transferred to a constant temperature The temperature of the heat preservation and sedimentation in the box is 150℃, and the time is 210min; the solid-liquid separation of the materials after the heat preservation and sedimentation is carried out to obtain the supernatant liquid and the reaction slag;

The reaction slag is washed countercurrently with water and then separated to obtain washing slag liquid and iron slag;

Industrial sodium chromate (HG/T 4312-2012) was used to determine the content of sodium chromate in the supernatant liquid and the washing residue liquid; the supernatant liquid was measured to contain 22.64g sodium chromate and 1.73g sodium metaaluminate ; Measured that the washing residue liquid contains 90.57g of sodium chromate and 26.04g of sodium metaaluminate;

According to the molar ratio of barium hydroxide to sodium chromate in the supernatant liquid of 1.2:1, 28.7g of barium hydroxide was added to the supernatant liquid for precipitation reaction, the reaction time was 2h, and the reaction temperature was 80°C; after the reaction was completed Separate the barium chromate precipitate A and the aluminum-containing lye B; return the aluminum-containing lye B to the high-pressure reactor for recycling;

According to the molar ratio of barium hydroxide to sodium chromate in the washing residue liquid of 1.2:1, 115.0g of barium hydroxide was added to the washing residue liquid for precipitation reaction, the reaction time was 2h, and the reaction temperature was 80°C; after the reaction was completed Separation of barium chromate precipitate C and aluminum-containing lye D;

Use "GB/T 5750.6-2006 Standard Test Method for Drinking Water, Metal Index Chromazurol S Spectrophotometric Method" to determine the aluminum content in aluminum-containing lye D, according to the aluminum content in sodium silicate and aluminum-containing lye D The sodium molar ratio is 1.2:1, 43.08g of sodium silicate water slurry with a mass concentration of 90% is added to the aluminum-containing lye D for precipitation reaction, the reaction time is 3h, the reaction temperature is 90°C; the reaction is completed After separation, low-aluminum lye and sodium aluminosilicate precipitation are obtained, and the aluminum removal rate is 95%, which meets the recycling standard; the separated low-aluminum lye is returned to the high-pressure reactor for recycling;

Combine barium chromate precipitation A and barium chromate precipitation C, and the chromium conversion rate is determined to be 97%; the combined barium chromate is dissolved in hydrochloric acid solution, and the liquid-to-solid ratio is 4:1 (mL:g). The molar ratio of barium chromate to HCl in the hydrochloric acid solution is 1:5. After dissolution, the chromium dissolution rate is measured to be 99%. Then, a reducing agent is added to carry out the reduction reaction. The stirring speed of the reduction reaction is 400rpm, and the reaction temperature is 80℃. The time is 2h, the reducing agent is a small molecular alcohol organic substance methanol, and the molar amount of the reducing agent is 5 times the theoretical reaction molar amount with barium chromate to obtain a mixed solution of chromium chloride and barium chloride. The reduction rate of chromium is 99%; Barium hydroxide is used to adjust the pH value of the mixed solution of chromium chloride and barium chloride to 9, so that chromium is completely precipitated in the form of chromium hydroxide, and the solid-liquid separation obtains the chromium hydroxide product. After centrifugal separation Dilute sulfuric acid is added to the liquid phase until the barium precipitation is complete, and a pure barium sulfate product is obtained.

Example 6

According to the process of Example 5, the liquid phase oxidation reaction and the insulation sedimentation were carried out. After the solid-liquid separation, the chromium conversion rate was measured to be 99%. According to the molar ratio of barium hydroxide to sodium chromate in the supernatant liquid, the molar ratio of sodium chromate was 1.2:1. Barium hydroxide was added to the solution, and the reaction was stirred for 2 hours at a temperature of 80°C. After the reaction, barium chromate precipitate A and aluminum-containing lye B were separated. The measured chromium conversion rate was 97%; Liquid B is returned to the high-pressure reactor for recycling, supplemented with a small amount of sodium hydroxide and water, and carried out the liquid phase oxidation reaction under the same conditions. After the reaction, the pressure is released and cooled, and then the materials in the high-pressure reactor are transferred to the thermostat for heat preservation and sedimentation. The sedimentation temperature was 150°C, the time was 210 minutes, and after solid-liquid separation, the measured chromium conversion rate was 99%, indicating that the recycling of aluminum-containing lye B has no effect on the chromium leaching.

Comparative example 1

According to the process of Example 5, the liquid phase oxidation reaction and insulation sedimentation were carried out. After the solid-liquid separation, the chromium conversion rate was measured to be 99%. The supernatant after the solid-liquid separation was directly recycled to the autoclave and supplemented with sodium hydroxide. With water, carry out the liquid phase oxidation reaction under the same conditions. After the reaction, the pressure is released and cooled, and then the materials in the autoclave are transferred to the thermostat for heat preservation and sedimentation. The temperature for heat preservation and sedimentation is 150°C and the time is 210min. After solid-liquid separation The measured conversion rate of chromium was 82%, indicating that excessive sodium chromate content in the supernatant would inhibit the leaching of chromium from chromite.

Example 7

According to the process of Example 5, the liquid phase oxidation reaction and insulation sedimentation were carried out. After solid-liquid separation, the supernatant liquid and the reaction residue were obtained. The chromium conversion rate was measured to be 99%; the reaction residue was separated by countercurrent washing with water to obtain Slag washing liquid and iron slag; according to the molar ratio of barium hydroxide to sodium chromate in the washing slag solution of 1.2:1, barium hydroxide is added to the washing slag solution for precipitation reaction, the reaction time is 2h, and the reaction temperature is 80 ℃; after the reaction, the barium chromate precipitate C and the aluminum-containing lye D are separated and the chromium conversion rate is 97%; according to the sodium silicate and aluminum-containing lye D, the molar ratio of sodium aluminate in the lye D is 1.2: 1. Add a sodium silicate water slurry with a mass concentration of 90% to the aluminum-containing lye D for precipitation reaction, the reaction time is 3h, the reaction temperature is 90°C; after the reaction, the low-aluminum lye and silicon are separated Sodium aluminate is precipitated, and the aluminum removal rate reaches 95%, which meets the circulation standard; the separated low-aluminum lye is returned to the high-pressure reactor for re-use; the liquid phase oxidation reaction is carried out under the same conditions, and the pressure is released and cooled after the reaction is completed. Then transfer the materials in the autoclave to a thermostat for heat preservation and sedimentation. The heat preservation and sedimentation temperature is 150°C and the time is 210min. After solid-liquid separation, the measured chromium conversion rate is 99%, indicating that the aluminum-containing lye D undergoes The low-aluminum lye obtained after sodium silicate treatment has no effect on the leaching of chromium.

Comparative example 2

According to the process of Example 5, the liquid phase oxidation reaction and insulation sedimentation were carried out. After solid-liquid separation, the supernatant liquid and the reaction residue were obtained. The chromium conversion rate was measured to be 99%; the reaction residue was separated by countercurrent washing with water to obtain Slag washing liquid and iron slag; according to the molar ratio of barium hydroxide to sodium chromate in the washing slag solution of 1.2:1, barium hydroxide is added to the washing slag solution for precipitation reaction, the reaction time is 2h, and the reaction temperature is 80 ℃; After the reaction, the barium chromate precipitate C and the aluminum-containing lye D are separated and the chromium conversion rate is 97%; the aluminum-containing lye D is returned to the high-pressure reactor for recycling after making up the alkali; according to the same conditions The liquid phase oxidation reaction is carried out. After the reaction is completed, the pressure is released and cooled, and then the materials in the autoclave are transferred to the thermostat for heat preservation and sedimentation. The temperature of heat preservation and sedimentation is 150℃ and the time is 210min. After solid-liquid separation, the conversion of chromium is measured. The rate is 88%, indicating that the untreated aluminum-containing lye D can inhibit the leaching of chromium.

The above are only preferred embodiments of the present invention and do not impose any limitation on the present invention. Any simple modifications, changes, and equivalent structural changes made to the above embodiments based on the technical essence of the invention still belong to the technical solutions of the present invention. Within the scope of protection.

Industrial applicability

The present invention proposes a new process route for preparing chromium salt by liquid phase oxidation of chromite, which innovatively solves the solid-liquid separation of chromite leaching process, the separation of chromium salt in high alkali medium, and the conversion of intermediate products into series The key process problem of chromium salt has great prospects for industrial application. In the chromite liquid-phase oxidation leaching process, it is proposed to use a high-pressure reactor equipped with a dynamic and static mixing paddle, so that the air phase in the upper part of the reactor is changed from the original single-region entrainment to the multi-region, multi-site volume. The multi-element mixing method of suction greatly strengthens the gas-liquid-solid three-phase mass transfer process in the reaction system and improves the efficiency of the leaching reaction process. The insulation sedimentation separation process of the oxidation leaching system of chromite in a high-alkali medium is proposed, which solves the problem of solid-liquid separation. Compared with traditional methods such as dilution filtration and centrifugation, it significantly reduces the solid-liquid separation time and equipment investment cost, and can always keep the aluminum content in the supernatant liquid low, the alkali content is high, the aluminum content in the slag washing liquid is high, and the alkali content is low. It is conducive to the subsequent circulation and aluminum removal process, while retaining the original lye concentration to the greatest extent, greatly improving the efficiency of the direct recycling of the medium.

Claims (17)

1. A combined dynamic and static stirring system, comprising a stirrer (1), characterized in that it also comprises a plurality of static stirring paddles (12) arranged in parallel with the stirring shaft (2) of the stirrer (1), and a plurality of said The static stirring blade (12) is arranged around the stirring shaft (2), and a stirring blade (4) is installed at the bottom of the stirring shaft (2).
2. A combined dynamic and static stirring system according to claim 1, characterized in that the distances between the plurality of static stirring paddles (12) and the stirring shaft (2) are all unequal.
3. A combined dynamic and static stirring system according to claim 1 or 2, characterized in that the static stirring paddle (12) is a slat-shaped stirring paddle, a cylindrical stirring paddle or a prismatic stirring paddle.
4. The dynamic and static combined stirring system according to claim 2, characterized in that, with the stirring shaft (2) of the stirrer (1) as the center, the installation radius of the static stirring paddle (12) is the same as the radius of the container used for stirring. The ratio is 1:7.5 to 1:16.
5. A process for preparing chromium salt by liquid-phase oxidation of chromite by using the dynamic and static combined stirring system of claim 1, 2 or 4, which is characterized in that it comprises:

   Add chromite, sodium hydroxide and water into the autoclave equipped with a dynamic and static mixing system. Under agitation, oxygen is introduced into the autoclave for liquid phase oxidation. After the reaction, the pressure is released and cooled, and then the The materials in the high-pressure reactor are transferred to the thermostat for heat preservation and sedimentation, and solid-liquid separation of the materials after heat preservation and sedimentation is carried out to obtain the supernatant liquid and the reaction residue;

   Separating the reaction slag after countercurrent washing to obtain washing slag liquid and iron slag;

   Adding barium hydroxide to the supernatant to perform a precipitation reaction, after the reaction is completed, barium chromate precipitate A and aluminum-containing lye B are obtained separately;

   Adding barium hydroxide to the washing slag liquid to perform a precipitation reaction, after the reaction is completed, barium chromate precipitation C and aluminum-containing lye D are obtained separately;

   The barium chromate precipitate A and the barium chromate precipitate C are dissolved in hydrochloric acid, and then a reducing agent is added to reduce the reaction to obtain a mixed solution of chromium chloride and barium chloride. The pH value of the mixed solution is adjusted so that the chromium is replaced with hydrogen. The form of chromium oxide is completely precipitated, and solid-liquid separation is used to obtain chromium hydroxide product.
6. The method according to claim 5, wherein the reaction temperature of the liquid phase oxidation reaction is 180° C. to 270° C., the oxygen partial pressure is 1.2 MPa to 2.6 MPa, the stirring speed is 500 rpm to 900 rpm, and the reaction time is 1 h ~5h.
7. The method according to claim 5, wherein the mass ratio of sodium hydroxide and chromite is (2-5):1, and the mass of sodium hydroxide is 30% to 30% of the total mass of sodium hydroxide and water. 60%.
8. The method according to claim 5, wherein the temperature of the heat preservation and sedimentation is 70°C to 150°C, and the time is 120min to 210min.
9. The method according to claim 5, wherein when barium hydroxide is added to the supernatant for precipitation reaction, the molar ratio of barium hydroxide to sodium chromate in the supernatant is (1 to 1.2): 1. The reaction time is 1h～2h, and the reaction temperature is 60～80℃;

   When barium hydroxide is added to the washing residue for precipitation reaction, the molar ratio of barium hydroxide to sodium chromate in the washing residue is (1～1.2):1, the reaction time is 1h～2h, and the reaction temperature is 60～ 80°C.
10. The method according to claim 5, further comprising adding sodium silicate slurry to the aluminum-containing lye D to perform a precipitation reaction, and after the reaction is completed, low-aluminum lye and sodium aluminosilicate precipitation are obtained separately .
11. The method according to claim 10, wherein the molar ratio of the sodium silicate to the sodium aluminate in the aluminum-containing lye D is (1 to 1.2):1.
12. The method according to claim 10, characterized in that it further comprises the step of returning the separated low-aluminum lye to the high-pressure reactor for recycling.
13. The method according to claim 5, characterized in that it further comprises returning the alkali solution B containing aluminum to the autoclave for recycling.
14. The method according to claim 5, wherein the ratio of the sum of the amount of the barium chromate precipitate A and the amount of the barium chromate precipitate C to the amount of HCl in the hydrochloric acid is 1: (2-5) , The volume of hydrochloric acid is 4-8 times the sum of the masses of barium chromate precipitation A and barium chromate precipitation C, where the unit of volume is mL and the unit of mass is g. The reducing agent is a small molecular alcohol organic substance, which reduces The molar amount of the agent is 1 to 5 times the theoretical reaction molar amount with barium chromate.
15. The method according to claim 5, wherein the stirring speed of the reduction reaction is 200 rpm to 400 rpm, the reaction temperature is 50° C. to 80° C., and the reaction time is 1 h to 2 h.
16. The method according to claim 5, characterized in that barium hydroxide is used to adjust the pH value of the mixed solution to 8-9 after the reduction reaction.
17. The method according to claim 5, characterized in that it further comprises adding sulfuric acid to the liquid phase obtained by the solid-liquid separation after the chromium is completely precipitated in the form of chromium hydroxide until the barium precipitation is complete, to obtain a barium sulfate product.

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