Continuous preparation device and method of high-purity potassium ferrate

Abstract

The invention discloses a continuous preparation device and method of high-purity potassium ferrate. The device comprises a reaction kettle, a stirring device is arranged on the reaction kettle, the interior of the reaction kettle is divided into an upper reaction area and a lower discharging area by an inclined baffle, a drain valve is arranged at the bottom of the lower end of the baffle, and an observation window is arranged on the side wall of the reaction kettle. The liquid discharging condition of the liquid discharging valve is observed; a discharge hole is formed in the side wall of the reaction area close to the lower end of the baffle; the stirring device comprises a motor fixedly arranged at the top of the reaction kettle, an output shaft of the motor is fixedly connected with a stirring shaft, the stirring shaft vertically penetrates through the interior of the reaction kettle, an anchor type stirring paddle is arranged on the stirring shaft, and the anchor type stirring paddle is located in the reaction area. According to the method, the high-purity potassium ferrate is directly separated from the reaction liquid, re-crystallization and organic solvent washing are not needed, and the obtaining cost of the high-purity potassium ferrate is effectively reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of solid potassium ferrate preparation, in particular to a continuous preparation device and method of high-purity potassium ferrate. Background Art

[0002] A great deal of research has been conducted on the application of potassium ferrate in water treatment, and numerous studies have confirmed its high efficiency and excellent performance in water treatment. There are three main methods for preparing potassium ferrate: melting, electrolysis, and chemical oxidation, with chemical oxidation being the most popular.

[0003] High-purity potassium ferrate is prepared using a chemical oxidation method, and the process is as follows: potassium hydroxide is added to a potassium hypochlorite solution to adjust the alkalinity, and ferric hydroxide is added to generate a reaction solution containing potassium ferrate under certain conditions, and then potassium ferrate is separated by solid-liquid filtration. This study found that under such process conditions, the separated filter cake also includes a large amount of salt and alkali as well as a small amount of other impurities in addition to potassium ferrate. Therefore, if potassium ferrate and other substances can be separated, high-purity potassium ferrate can be obtained. The traditional method is to use the difference in solubility of salt and alkali and potassium ferrate in potassium hydroxide for recrystallization, and then use the characteristic that potassium ferrate is insoluble in organic solvents to wash and purify again to obtain high-purity potassium ferrate.

[0004] The current process for producing high-purity potassium ferrate using a chemical oxidation method involves the following steps: 1. Preparation of crude potassium ferrate; 2. Recrystallization of the potassium ferrate; and 3. Purification of the recrystallized potassium ferrate by washing with an organic solvent. In step 2, the crude potassium ferrate is purified by recrystallization using a dilute and saturated potassium hydroxide solution. The crude potassium ferrate is then filtered, leaving the desired filter cake and a filtrate containing a large amount of potassium hydroxide as waste. In step 3, the recrystallized filter cake is washed with a large amount of toxic organic solvents such as acetone, ethanol, and benzene (particularly benzene, a strong carcinogen). The resulting organic solvent waste cannot be reused and must be disposed of as waste. The waste generated by these steps poses significant environmental, health, and economic risks, contradicting the concept of "green chemistry" and making it unsuitable for large-scale production.

[0005] Nowadays, there is a particular need for a method to prepare high-purity potassium ferrate in an environmentally friendly and economical manner to meet the increasing market demand. Summary of the Invention

[0006] In view of the above technical problems existing in the prior art, the object of the present invention is to provide a continuous preparation device and method for high-purity potassium ferrate.

[0007] The technical solution adopted in the present invention is as follows: A continuous preparation device for high-purity potassium ferrate includes a reactor equipped with a stirring device. An inclined baffle is installed inside the reactor, which divides the internal space of the reactor into an upper reaction zone and a lower discharge zone. A feed port is provided in the reaction zone, and a discharge port is provided at the bottom of the discharge zone. A drain valve is provided at the bottom of the lower end of the baffle, and an observation window is provided on the side wall of the reactor near the drain valve for observing the discharge of liquid from the drain valve. A discharge port is provided on the side wall of the reaction zone close to the lower end of the baffle; The stirring device includes a motor fixedly arranged on the top of the reactor, the output shaft of the motor is fixedly connected to the stirring shaft, the stirring shaft vertically passes through the interior of the reactor, and an anchor stirring paddle is arranged on the stirring shaft, and the anchor stirring paddle is located in the reaction zone.

[0008] Furthermore, the reactor is of cylindrical structure, with a heat exchange jacket provided on the outside thereof, a heat exchange fluid inlet provided at the lower portion of the heat exchange jacket, and a heat exchange fluid outlet provided at the upper portion thereof.

[0009] Furthermore, the baffle has an inclination angle of 3-5° compared to the horizontal plane.

[0010] Furthermore, the observation window is made of transparent glass and is arranged on the upper side wall of the discharge area close to the drain valve.

[0011] Furthermore, the drain valve adopts a solenoid valve, and the signal line of the solenoid valve passes through the side wall of the reactor and is connected to the PLC control system; a camera with a high-definition camera is provided on the outside of the observation window, and the camera circuit is connected to the image processing system. The image processing system is connected to the solenoid valve signal through the PLC control system. The camera captures the fluid image flowing out of the drain valve through the observation window, and the captured fluid image is transmitted to the image processing system for analysis and processing, and the analysis result is transmitted to the PLC control system. After the black reaction liquid is observed through the observation window, the drain valve is closed through feedback control of the PLC control system.

[0012] Furthermore, the stirring device also includes a propulsion stirring paddle, and the lower end of the stirring shaft penetrates into the discharge area and is connected to the propulsion stirring paddle.

[0013] Furthermore, the gap between the anchor-type stirring blade and the inner wall of the reactor is 10-25 mm.

[0014] A method for continuously preparing high-purity potassium ferrate comprises the following steps: 1) Add potassium hypochlorite solution, potassium hydroxide, and ferric hydroxide into the reaction zone of the reactor, start the motor, and drive the anchor-type stirring blade to stir at a speed of 70-100 r / min; pass warm water into the heat exchange jacket outside the reactor to control the reaction temperature of the reaction liquid in the reaction zone to 30-40°C; 2) After the reaction is completed, coolant is introduced into the heat exchange jacket outside the reactor to reduce the temperature of the reaction solution in the reaction zone to 0-5°C. Stirring is continued. A large amount of potassium ferrate generated by the reaction is precipitated and concentrated in the middle and upper part of the center of the reaction solution, and the reaction solution is separated into layers; 3) Open the drain valve to drain the reaction liquid in the reaction zone into the discharge zone. Observe the discharge through the observation window until the discharged reaction liquid turns black, then close the drain valve; open the discharge port to discharge the remaining potassium ferrate mixture and perform solid-liquid separation. After drying the obtained solid, high-purity potassium ferrate is obtained; 4) The reaction liquid in the discharge zone is discharged and mixed with the filtrate obtained in step 3), and the mixed liquid is subjected to solid-liquid separation. The resulting solid is dried to obtain crude potassium ferrate; at the same time, the reaction zone of the reactor can be further charged with materials for the next batch of reaction.

[0015] Furthermore, the effective chlorine concentration of the potassium hypochlorite solution is 10-20%, the mass of potassium hydroxide is 60-70% of the mass of the potassium hypochlorite solution, and the mass of ferric hydroxide is 35-45% of the mass of the potassium hypochlorite solution.

[0016] Furthermore, the reaction time of step 1) is 40-80 min.

[0017] Compared with the prior art, the present invention has the following beneficial effects: 1. To reduce, to a certain extent, the pollution and waste caused by the steps of re-crystallization and organic solvent washing during the purification of potassium ferrate, the present invention separates high-purity potassium ferrate directly from the reaction solution. The specific principle is as follows: a unique double-layer reactor structure, with an anchor-type stirring paddle in the upper layer and a propeller-type stirring paddle in the lower layer. The blades of the anchor-type stirring paddle are close to the inner wall of the reactor, mainly generating circumferential flow (tangential flow) and radial flow. Due to the small gap between the blades and the wall, the fluid is strongly sheared between the blades and the wall, forming a local high-shear zone. However, the overall circulation capacity is weak, and most of the potassium ferrate precipitated by the reaction slowly accumulates in the middle part with low shear force (the entire reaction system is gray-brown, and the high-purity potassium ferrate is black). At the same time, due to the different densities of different substances, which is particularly obvious in high-alkalinity systems, the high-purity potassium ferrate has a lower density. Therefore, it is concentrated on the upper middle surface of the reaction solution (visible black substance). After the reaction is completed and cooled, a large amount of black high-purity potassium ferrate accumulates in the upper part of the reaction solution. At this time, open the drain valve on the baffle to discharge the material until black reaction liquid is observed through the observation window, then close the drain valve, and then open the discharge port of the reaction zone. The discharged material is passed into a centrifuge or other solid-liquid separation device for solid-liquid separation. After the filter cake is dried, the potassium ferrate content can reach more than 90% after being determined by the classical chromite method. This part of the potassium ferrate product does not need to be re-crystallized or washed with an organic solvent.

[0018] The filtrate (saturated potassium ferrate solution) after solid-liquid separation is then poured back into the lower reactor. The lower reactor utilizes a propeller-type agitator, similar to a propeller, with axial flow predominant, pushing the fluid in an upward and downward circulation pattern (e.g., a figure-eight flow pattern). This flow pattern achieves extensive fluid mixing and promotes rapid overall mixing. Under propeller agitation, the solution is rapidly mixed and homogenized. The solution is then discharged through a solid-liquid separator for solid-liquid separation and drying, yielding the crude potassium ferrate product.

[0019] 2. Able to meet the needs of different fields: the high-purity potassium ferrate prepared in the upper layer can meet the needs of the medical field, etc., and the crude potassium ferrate prepared in the lower layer can meet the needs of pond bottom improvement, fish and shrimp farming and other fields.

[0020] 3. Continuous reaction can be achieved. After the upper reaction liquid is discharged, the drain valve at the bottom of the inclined baffle and the discharge port on the upper reaction zone wall of the reactor are closed, and the next round of feeding can be carried out again, so as to proceed continuously. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The diagram is a structural diagram of a continuous preparation device for high-purity potassium ferrate according to the present invention. DETAILED DESCRIPTION

[0022] The present invention will be further described below with reference to specific embodiments, but the protection scope of the present invention is not limited thereto.

[0023] A continuous preparation device for high-purity potassium ferrate includes a reactor 2 equipped with a stirring device. An inclined baffle 12 is installed inside the reactor 2. The baffle 12 is inclined at an angle of 3-5 degrees relative to the horizontal plane. The baffle 12 divides the internal space of the reactor 2 into an upper reaction zone and a lower discharge zone. A feed port 10 is provided in the reaction zone, and a discharge port 13 is provided at the bottom of the discharge zone. A drain valve 5 is provided at the bottom of the lower end of the baffle 12. An observation window 4 is provided on the side wall of the reactor 2 near the drain valve 5 for observing the discharge of the drain valve 5. Figure 1 The observation window 4 is made of transparent glass and is arranged on the upper side wall of the discharge area close to the drain valve 5.

[0024] A discharge port 3 is provided on the side wall of the reaction zone near the lower end of the baffle 12 . For better discharge, the bottom of the discharge port 3 is at the same horizontal elevation as the surface of the lower end of the baffle 12 .

[0025] The stirring device includes a motor 11 fixedly mounted on the top of the reactor 2. The output shaft of the motor 11 is fixedly connected to a stirring shaft, which vertically extends through the interior of the reactor 2. An anchor stirring paddle 8 is provided in the middle of the stirring shaft. The anchor stirring paddle 8 is located in the reaction zone, and the gap between the anchor stirring paddle 8 and the inner wall of the reactor 2 is 10-25 mm. The lower end of the stirring shaft penetrates into the discharge zone and is connected to a propeller stirring paddle 9.

[0026] comparison Figure 1 The reactor 2 is a cylindrical structure, with a heat exchange jacket 1 provided on its outer side. A heat exchange fluid inlet 6 is provided at the lower portion of the heat exchange jacket 1, and a heat exchange fluid outlet 7 is provided at the upper portion.

[0027] The drain valve 5 is a solenoid valve, and the signal line of the solenoid valve passes through the side wall of the reactor 2 and is connected to the PLC control system; thus, the opening or closing of the drain valve 5 can be controlled by the PLC control system.

[0028] In addition, in actual industrial production, in order to better automatically control the opening or closing of the drain valve 5, the following structural design can be carried out: a camera with a high-definition camera is set on the outside of the observation window 4, and the camera circuit is connected to the image processing system. The image processing system is connected to the drain valve 5 signal through the PLC control system. The camera shoots the fluid image flowing out of the drain valve 5 through the observation window 4, and the shot fluid image is transmitted to the image processing system for analysis and processing, and the analysis result is transmitted to the PLC control system. After the black reaction liquid is observed through the observation window 4, the drain valve 5 is closed through feedback control of the PLC control system.

[0029] A method for continuously preparing high-purity potassium ferrate comprises the following steps: 1) Add potassium hypochlorite solution, potassium hydroxide, and ferric hydroxide into the reaction zone of reactor 2, start the motor, and drive the anchor-type stirring blade 8 to stir at a speed of 70-100 r / min; pass warm water into the heat exchange jacket 1 outside reactor 2, control the reaction temperature of the reaction liquid in the reaction zone to 30-40°C, and the reaction time to 40-80 minutes; 2) After the reaction is completed, coolant is introduced into the heat exchange jacket 1 outside the reactor 2 to reduce the temperature of the reaction solution in the reaction zone to 0-5°C. Stirring is continued. A large amount of potassium ferrate generated by the reaction is precipitated and concentrated in the middle and upper part of the center of the reaction solution, and the reaction solution is separated into layers; 3) Open the drain valve 5 to discharge the reaction liquid in the reaction zone into the discharge zone. Observe the discharge through the observation window 4 until the discharged reaction liquid turns black, then close the drain valve 5. Open the discharge port 3 of the reaction zone to discharge the remaining potassium ferrate mixture and perform solid-liquid separation to obtain a solid product and a saturated mother liquor filtrate. The obtained solid is dried to obtain high-purity potassium ferrate. 4) The reaction liquid in the discharge zone is discharged and mixed with the saturated mother liquor filtrate obtained in step 3), and the mixed liquid is subjected to solid-liquid separation. The resulting solid is dried to obtain crude potassium ferrate; at the same time, the reaction zone of reactor 2 can be further charged with materials for the next batch of reaction.

[0030] Furthermore, the saturated mother liquor filtrate separated in step 3) can be returned to the reaction zone of reactor 2 to wash away the residual solid material on the inner wall, and then the solid-liquid separation is repeated. The obtained solid products are combined and dried to obtain high-purity potassium ferrate.

[0031] In step 3), the reaction liquid in the reaction zone is discharged into the discharge zone. A small amount of high-concentration potassium ferrate carried over from the upper layer may be mixed with the reaction liquid and enter the discharge zone. If filtered directly without stirring, the resulting filter cake will have an uneven distribution of potassium ferrate. Furthermore, stirring the discharge zone can also prevent this high-concentration potassium ferrate carried over from the upper layer from concentrating in the upper portion of the reaction liquid. Example

[0032] 20 kg of potassium hypochlorite with a 20% effective chlorine concentration, 7 kg of potassium hydroxide (90% purity, the same below), and 8 kg of ferric hydroxide were added to a reactor. A motor-driven anchor-type agitator was used to stir the contents at 80 rpm. After uniform mixing, the remaining 8 kg of potassium hydroxide was added to maintain the reaction temperature at 35°C. After 60 minutes of reaction, chilled liquid was introduced into the heat exchange jacket outside the reactor to cool the temperature to 0-5°C. The lower layer of reaction liquid was then discharged. When the discharged material turned black, the discharge was closed and the discharged lower layer of reaction liquid was collected. A high-concentration potassium ferrate mixture remained in the reactor. This remaining potassium ferrate mixture was discharged and subjected to solid-liquid separation to obtain a solid product and a saturated mother liquor filtrate. The separated saturated mother liquor filtrate was returned to the reactor to rinse away any residual solid material on the inner walls. Solid-liquid separation was repeated. The resulting solid products were combined and dried to obtain the upper layer of high-purity potassium ferrate.

[0033] The saturated mother liquor filtrate separated above is mixed with the lower layer reaction liquid released previously, stirred and mixed for 5-10 minutes, and after mixing evenly, passed into a separation device at 0-5°C for solid-liquid separation, the solid is dried, and determined to obtain the crude potassium ferrate in the lower layer.

[0034] The total yield of potassium ferrate produced is 92% (i.e., mass of product produced × purity / theoretical mass of potassium ferrate produced). The upper layer of high-purity potassium ferrate has a purity of over 90% and a 100% yield of 35%. The lower layer of crude potassium ferrate has a purity of 28.98% and a 100% yield of 57%. The remainder decomposes or remains unreacted in the final filtrate and during the synthesis operation.

[0035] Comparative Example 1: 20 kg of potassium hypochlorite with an effective chlorine concentration of 20%, 7 kg of potassium hydroxide (90% purity, the same below), and 8 kg of ferric hydroxide were added to a reactor. The materials in the reactor were stirred at 80 r / min using a motor-driven propeller stirring paddle. After stirring evenly, the remaining 8 kg of potassium hydroxide was added to control the reaction temperature to 35°C. After the reaction was completed for 60 minutes, a chilled liquid was passed into the heat exchange jacket outside the reactor. After cooling to 0-5°C, the reaction liquid was discharged and passed into a separation device at 0-5°C for solid-liquid separation. The solid was dried and measured to obtain crude potassium ferrate.

[0036] The total yield of potassium ferrate produced above was 91.87% (calculated using the same method as in Example 1).

[0037] The purity of the crude potassium ferrate finally obtained was 35.7%.

[0038] The method of the present invention can produce high-purity potassium ferrate in a green, continuous and large-scale manner, and to a certain extent avoids the pollution and waste caused by the re-crystallization and organic solvent washing steps in the preparation of high-purity potassium ferrate.

[0039] The contents described in this specification are merely an enumeration of the implementation forms of the inventive concept, and the protection scope of the present invention should not be considered as being limited to the specific forms described in the embodiments.

Claims

1. A continuous preparation device for high-purity potassium ferrate, characterized in that The invention comprises a reactor (2), wherein the reactor (2) is provided with a stirring device, and an inclined baffle (12) is installed inside the reactor (2), wherein the baffle (12) divides the internal space of the reactor (2) into an upper reaction zone and a lower discharge zone, wherein a feed port (10) is provided on the reaction zone, and a discharge port (13) is provided at the bottom of the discharge zone; a drain valve (5) is provided at the bottom of the lower end of the baffle (12), and an observation window (4) is provided on the side wall of the reactor (2) near the position of the drain valve (5) for observing the discharge condition of the drain valve (5); A discharge port (3) is provided on the side wall of the reaction zone close to the lower end of the baffle (12); The stirring device comprises a motor (11) fixedly arranged on the top of the reactor (2), the output shaft of the motor (11) being fixedly connected to a stirring shaft, the stirring shaft vertically passing through the interior of the reactor (2), an anchor stirring paddle (8) being arranged on the stirring shaft, and the anchor stirring paddle (8) being located in the reaction zone.

2. The continuous preparation device for high-purity potassium ferrate according to claim 1, characterized in that The reactor (2) is cylindrical in structure, with a heat exchange jacket (1) provided on its outer side. A heat exchange fluid inlet (6) is provided at the lower portion of the heat exchange jacket (1), and a heat exchange fluid outlet (7) is provided at the upper portion.

3. The continuous preparation device for high-purity potassium ferrate according to claim 1, characterized in that The baffle (12) has an inclination angle of 3-5° compared to the horizontal plane.

4. The continuous preparation device for high-purity potassium ferrate according to claim 1, characterized in that The observation window (4) is made of transparent glass and is arranged on the upper side wall of the discharge area near the drain valve (5).

5. The continuous preparation device for high-purity potassium ferrate according to claim 1, characterized in that The drain valve (5) adopts a solenoid valve, and the signal line of the solenoid valve passes through the side wall of the reactor (2) and is connected to the PLC control system; a camera with a high-definition camera is provided on the outside of the observation window (4), and the camera circuit is connected to the image processing system. The image processing system is connected to the solenoid valve signal through the PLC control system. The camera shoots the image of the fluid flowing out of the drain valve (5) through the observation window (4), and the shot fluid image is transmitted to the image processing system for analysis and processing, and the analysis result is transmitted to the PLC control system. After the black reaction liquid is observed through the observation window (4), the drain valve (5) is closed through the feedback control of the PLC control system.

6. The continuous preparation device for high-purity potassium ferrate according to claim 1, characterized in that The stirring device further comprises a propulsion stirring paddle (9), and the lower end of the stirring shaft penetrates into the discharge area and is connected to the propulsion stirring paddle (9).

7. The continuous preparation device for high-purity potassium ferrate according to claim 1, characterized in that The gap between the anchor-type stirring blade (8) and the inner wall of the reactor (2) is 10-25 mm.

8. A method for the continuous preparation of high-purity potassium ferrate, characterized in that The following steps are involved: Step 1: Add potassium hypochlorite solution, potassium hydroxide and ferric hydroxide into the reaction zone of the reactor (2), start the motor, and drive the anchor stirring blade (8) to stir at a speed of 70-100 r / min; pass warm water into the heat exchange jacket (1) outside the reactor (2), and control the reaction temperature of the reaction liquid in the reaction zone to be 30-40°C; Step 2: After the reaction is completed, coolant is introduced into the heat exchange jacket (1) outside the reactor (2) to reduce the temperature of the reaction liquid in the reaction zone to 0-5°C. Stirring is continued, and a large amount of potassium ferrate generated by the reaction is precipitated and concentrated in the middle and upper part of the center of the reaction liquid, and the reaction liquid is separated into layers; Step 3: Open the drain valve (5), and discharge the reaction liquid in the reaction zone into the discharge zone. Observe the discharge condition through the observation window (4) until the discharged reaction liquid turns black, then close the drain valve (5); open the discharge port (3), discharge the remaining potassium ferrate mixture, and perform solid-liquid separation. After drying the obtained solid, high-purity potassium ferrate is obtained; Step 4: The reaction liquid in the discharge zone is discharged and mixed with the filtrate obtained in step 3. The mixed liquid is subjected to solid-liquid separation. The obtained solid is dried to obtain crude potassium ferrate. At the same time, the reaction zone of the reactor (2) can be further charged with materials for the next batch of reaction.

9. The method according to claim 8, wherein The effective chlorine concentration of the potassium hypochlorite solution is 10-20%, the mass of potassium hydroxide is 60-70% of the mass of the potassium hypochlorite solution, and the mass of ferric hydroxide is 35-45% of the mass of the potassium hypochlorite solution.

10. The method according to claim 8, wherein The reaction time of step 1 is 40-80 min.

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