Bismuth hydroxide crystal powder production method and production line

Abstract

The invention provides a bismuth hydroxide crystal powder production method and a production line. The production method of the bismuth hydroxide crystal powder comprises the steps that purified water is injected into a synthesis kettle according to the volume ratio of nitric acid with the concentration being 68% to the purified water being 1: 1, then nitric acid with the concentration being 20%-68% is injected, stirring is conducted, bismuth oxide is added, the molar ratio of Bi to nitric acid is 1: (3.1-4.0), the adding speed of the bismuth oxide is 300-400 kg / h, the temperature is 50-60 DEG C, and stirring is conducted for constant volume; s2, stirring: adding ammonia water with the mass fraction of 25-28%, adjusting the pH value to 1-1.3, keeping the temperature at 50-60 DEG C, keeping the temperature for 2-3 hours, stopping stirring, standing for 30-40 minutes, and pumping out supernate; s3, adding purified water of which the volume corresponds to that of the extracted supernatant, stirring, adding nitric acid to adjust the pH value to 1-1.3, stirring for 30-40 minutes at the temperature of 50-60 DEG C, stopping stirring, standing for 30-40 minutes, extracting the supernatant, and repeating once; adding purified water with the volume corresponding to that of the extracted supernatant, stirring, heating to 50-60 DEG C, adding ammonia water with the mass fraction of 25-28% at the speed of 200-600L / h, adjusting the pH value to 7-7.5, and keeping the temperature for 2-3h to obtain a solid-liquid mixture; and filtering, washing and drying the solid-liquid mixture to obtain bismuth hydroxide crystal powder.

Description

Technical Field

[0001] The present disclosure relates to the field of coatings, and more specifically to a method and production line for producing bismuth hydroxide crystal powder. Background Art

[0002] Bismuth hydroxide is a new type of inorganic bismuth catalyst, which is suitable for cathode electrophoretic paint system, replacing toxic organic tin catalysts to prepare environmentally friendly coatings.

[0003] For the preparation of bismuth hydroxide crystals, it is necessary to improve many aspects of the bismuth hydroxide crystal powder, such as bismuth hydroxide content (ie, purity), impurity content, particle size, water-soluble conductivity, production capacity, cost, etc. Summary of the invention

[0004] In view of the problems existing in the background technology, an object of the present disclosure is to provide a method and production line for producing bismuth hydroxide crystal powder, which can at least improve the purity of bismuth hydroxide in the final bismuth hydroxide powder.

[0005] Thus, a method for producing bismuth hydroxide crystal powder includes the steps of: S1, preparing a bismuth nitrate solution: first, injecting purified water into a synthesis kettle at a volume ratio of 1:1 between industrial-grade nitric acid with a concentration of 68% and purified water, then injecting industrial-grade nitric acid with a concentration of 20-68%, starting stirring, adding bismuth oxide, the amount of bismuth oxide added is calculated based on a molar ratio of Bi to nitric acid of 1:(3.1-4.0), the addition rate of bismuth oxide is 300-400kg / h, the dissolution temperature is controlled by the addition rate of bismuth oxide, the temperature is controlled at 50-60°C, and stirring is continued. After stirring until the solution is completely dissolved and the volume is fixed, a bismuth nitrate solution is synthesized; S2, a bismuth nitrate solution is reacted with ammonia water for precipitation: the synthesis reactor is stirred, and ammonia water with a mass fraction of 25-28% is injected into the synthesis reactor to adjust the pH of the system to 1-1.3 until the pH of the system is stable. During the reaction process, the solution temperature is controlled at 50-60°C, and the reaction is continued for 2-3 hours in this temperature range. If the pH drops during the insulation process, 25-28% ammonia water is added to stabilize the pH, and then the stirring is turned off, and the mixture is allowed to stand for 30-40 minutes until the precipitate is completely settled, and the supernatant is removed; S3 , sedimentation and impurity removal: after the supernatant is removed, a volume of purified water corresponding to the removed supernatant is added to the synthesis kettle, stirring is started, and then industrial-grade nitric acid with a concentration of 20-68% is added to adjust the pH of the system to 1-1.3 for stability, stirring for 30-40 minutes, the temperature is 50-60°C, and then the stirring is turned off, and the precipitation is allowed to stand for 30-40 minutes until all the precipitates are settled and the supernatant is removed, and the above operation is repeated once, and the next step is performed; S4, conversion and shaping to obtain a solid-liquid mixture containing bismuth hydroxide crystals: a volume of nitric acid corresponding to the removed supernatant is added to the synthesis kettle. Purify water, start stirring, stir until the system is uniform, start heating until the system temperature is 50-60°C, then add 25-28% ammonia water by mass into the synthesis reactor at a rate of 200-600L / h, adjust the pH of the system to 7-7.5, and continue to keep warm for 2-3h after the pH stabilizes. If the pH drops during the insulation process, add ammonia water to stabilize the pH. After the insulation reaction, the bismuth hydroxide crystals are transformed and fixed to obtain a solid-liquid mixture containing bismuth hydroxide crystals; S5, filter, wash and dry the solid-liquid mixture to obtain bismuth hydroxide crystal powder.

[0006] A bismuth hydroxide crystal powder production line is at least applicable to the above-mentioned bismuth hydroxide crystal powder production method, and the bismuth hydroxide crystal powder production line comprises a synthesis kettle, a filtering, washing and drying three-in-one device, and a first receiving bin; the synthesis kettle is used to prepare a bismuth nitrate solution, the bismuth nitrate solution and ammonia water precipitation reaction, sedimentation and impurity removal, and conversion and shaping to obtain a solid-liquid mixture containing bismuth hydroxide crystals; the filtering, washing and drying three-in-one device is connected to the synthesis kettle, the filtering, washing and drying three-in-one device is used to receive the solid-liquid mixture containing bismuth hydroxide crystals from the synthesis kettle, filter the solid-liquid mixture, wash and filter the filtered bismuth hydroxide crystals, vacuum dry the washed and filtered bismuth hydroxide crystals to obtain dried bismuth hydroxide crystal powder, and use the rotating descent of a stirring paddle to scrape the dried crystal powder from the surface downward, and use the inclined surface of the stirring paddle to push the scraped crystal powder out of the filtering, washing and drying three-in-one device; the first receiving bin is connected to the filtering, washing and drying three-in-one device, and the first receiving bin is used to receive the dried bismuth hydroxide crystal powder discharged from the filtering, washing and drying three-in-one device.

[0007] The beneficial effects of the present disclosure are as follows: in the method for producing bismuth hydroxide crystal powder according to the present disclosure and at least applicable to the aforementioned method for producing bismuth hydroxide crystal powder, through steps S1 to S5, the average particle size of the bismuth hydroxide powder of the final product is between 5-12 μm, the bismuth hydroxide content in the bismuth hydroxide powder of the final product is between 86-93%, and the water-soluble conductivity of the bismuth hydroxide of the final product is 250-270 μs / cm. That is to say, at least the bismuth hydroxide content in the bismuth hydroxide powder of the final product can be increased, that is, at least the purity of the bismuth hydroxide in the bismuth hydroxide powder of the final product can be increased. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 is a layout diagram of a bismuth hydroxide crystal powder production line according to the present disclosure.

[0009] Figure 2 yes Figure 1 An enlarged view of the filtering, washing and drying three-in-one equipment of the bismuth hydroxide crystal powder production line.

[0010] Figure 3 yes Figure 2 Top view of the .

[0011] The reference numerals are described as follows:

[0012] 1000 Bismuth Hydroxide Crystal Powder Production Line 3 First Receiving Bin

[0013] 1 synthesis reactor 4 crushing module

[0014] 11 kettle body 41 first vacuum feeder

[0015] 12 first stirring paddle 42 buffer chamber

[0016] 13 first jacket 43 weighing module

[0017] 14 first discharge valve 44 third discharge valve

[0018] 2 Filter, Wash and Dry 3-in-1 Equipment 45 Crusher

[0019] 21 tank body 46 second receiving bin

[0020] 211 feeding port 5 homogenization packaging module

[0021] 212 air inlet 51 second vacuum feeder

[0022] 213 exhaust valve 52 homogenizer

[0023] 214 cleaning port 53 fourth discharge valve

[0024] 215 filtrate outlet 54 automatic filling and packaging machine

[0025] 216 bottom 55 barrel

[0026] 22 filter cloth 56 weighing

[0027] 23 second stirring paddle 57 conveyor belt

[0028] 24 second jacket 58 mechanical arm

[0029] 25 Second discharge valve 6 Steel frame platform

[0030] 26 Discharging mechanism DETAILED DESCRIPTION

[0031] It will be understood that the disclosed embodiments are merely examples of the present disclosure, which may be implemented in various forms, and therefore, the specific details disclosed herein should not be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one of ordinary skill in the art to implement the present disclosure in various ways.

[0032] [Bismuth Hydroxide Crystal Powder Production Method]

[0033] Reference Figures 1 to 3 According to the present disclosure, the method for producing bismuth hydroxide crystal powder comprises the steps of:

[0034] S1, preparing a bismuth nitrate solution: first, injecting purified water into a synthesis reactor 1 at a volume ratio of 1:1 of industrial-grade nitric acid with a concentration of 68% to purified water (i.e., if the concentration of nitric acid is not 68%, the volume ratio of nitric acid to purified water is calculated as 68% to non-68%), then injecting industrial-grade nitric acid with a concentration of 20-68%, starting stirring, adding bismuth oxide, the amount of bismuth oxide added is calculated based on a molar ratio of Bi to nitric acid of 1:(3.1-4.0), the addition rate of bismuth oxide is 300-400 kg / h, the dissolution temperature is controlled by the addition rate of bismuth oxide, the temperature is controlled at 50-60° C., and stirring is continued until the solution is completely dissolved and the volume is fixed, thereby synthesizing a bismuth nitrate solution;

[0035] S2, precipitation reaction of bismuth nitrate solution and ammonia water: start stirring in synthesis reactor 1, inject 25-28% ammonia water by mass into synthesis reactor 1 to adjust the pH of the system to 1-1.3 until the pH of the system is stable, control the solution temperature at 50-60°C during the reaction process, and keep it warm in this temperature range for 2-3 hours. If the pH drops during the insulation process, add 25-28% ammonia water by mass to stabilize the pH, then turn off stirring, let it stand for 30-40 minutes until the precipitate is completely settled, and remove the supernatant;

[0036] S3, sedimentation and impurity removal: after the supernatant is removed, a volume of purified water corresponding to the removed supernatant is added to the synthesis reactor 1, stirring is started, and then industrial-grade nitric acid with a concentration of 20-68% is added to adjust the pH of the system to 1-1.3 for stability, stirring for 30-40 minutes, the temperature is 50-60°C, and then the stirring is turned off, and the mixture is allowed to stand for 30-40 minutes until all the precipitates are settled, and then the supernatant is removed, and the above operation is repeated once (i.e., step S3 is performed twice), and the next operation is performed;

[0037] S4, converting and finalizing to obtain a solid-liquid mixture containing bismuth hydroxide crystals: adding purified water of a volume corresponding to the supernatant removed into the synthesis reactor 1, starting stirring, stirring until the system is uniform, starting heating to a system temperature of 50-60° C., then adding ammonia water of 25-28% by mass into the synthesis reactor 1 at a rate of 200-600 L / h, adjusting the system pH to 7-7.5, and continuing to keep warm for 2-3 hours after the pH stabilizes. If the pH drops during the insulation process, add ammonia water of 25-28% by mass to stabilize the pH. After the insulation reaction, the bismuth hydroxide crystals are converted and finalized to obtain a solid-liquid mixture containing bismuth hydroxide crystals;

[0038] S5, filtering, washing and drying the solid-liquid mixture to obtain bismuth hydroxide crystal powder.

[0039] In the method for producing bismuth hydroxide crystal powder according to the present disclosure, through steps S1 to S5, the average particle size of the final bismuth hydroxide powder is between 5-12 μm, the bismuth hydroxide content in the final bismuth hydroxide powder is between 86-93%, and the water-soluble conductivity of the final bismuth hydroxide is 250-270 μs / cm. That is, at least the bismuth hydroxide content in the final bismuth hydroxide powder can be increased, that is, at least the purity of the bismuth hydroxide in the final bismuth hydroxide powder can be increased.

[0040] In one example, in step S2, the synthesis reactor 1 is stirred, and ammonia water with a mass fraction of 25-28% which is 70-80% of the volume of the bismuth nitrate solution in step S1 is injected into the synthesis reactor 1 at a rate of 500-700 L / h, and then the rate of addition of ammonia water is immediately reduced to 100-200 L / h, and the pH is immediately detected to adjust the pH of the system to 1-1.3. When the pH is close to the range of 1-1.3, the rate of addition of ammonia water is further reduced to 50-100 L / h until the pH of the system is stable.

[0041] In one example, in step S2, step S3 and step S4, pH stability is based on a pH change amplitude of less than 0.05 / min.

[0042] In one example, the purity of bismuth oxide is 2N or higher.

[0043] Reference Figures 1 to 3 In one example, step S5 includes sub-steps:

[0044] S51, feeding, the solid-liquid mixture containing bismuth hydroxide crystals after conversion and finalization in step S4 is discharged into the filtering, washing and drying three-in-one device 2 through the first discharge valve 14 of the synthesis reactor 1;

[0045] S52, after feeding, close the first discharge valve 14 of the synthesis reactor 1, and introduce compressed air into the filtering, washing and drying three-in-one device 2 to increase the pressure, and control the pressure at 0.2-0.3MPa. The solution in the solid-liquid mixture is discharged through the 700-1000 mesh filter cloth 22 at the bottom 216 of the filtering, washing and drying three-in-one device 2, and the bismuth hydroxide crystals in the solid-liquid mixture remain in the filtering, washing and drying three-in-one device.

[0046] Reserve 2;

[0047] S53, washing and filtering, after the solution in the solid-liquid mixture is discharged, purified water is introduced, the second stirring paddle 23 in the filtering, washing and drying three-in-one device 2 is turned on to stir and wash for 1-2 hours, and then compressed air is introduced for pressurization, and the pressure is controlled at 0.2-0.3MPa, and the washed purified water is discharged through the filter cloth 22. Step S53 is performed 3-4 times in total, and clean crystals are obtained after the washing and filtering process.

[0048] S54, vacuum drying, start vacuuming to make negative pressure in the filtering, washing and drying three-in-one device 2, the negative pressure is higher than 0.095MPa but less than atmospheric pressure, and introduce heating steam into the second jacket 24 to raise the temperature in the filtering, washing and drying three-in-one device 2, start stirring to break up crystal agglomerations, raise the temperature in the filtering, washing and drying three-in-one device 2 to 80-95°C, and perform vacuum drying for 5-7h,

[0049] S55, unloading, after vacuum drying is completed, open the exhaust valve 213 on the filtering, washing and drying three-in-one equipment 2, balance the air pressure in the filtering, washing and drying three-in-one equipment 2, open the second unloading valve 25 of the filtering, washing and drying three-in-one equipment 2, and use the rotation and descent of the second stirring paddle 23 of the filtering, washing and drying three-in-one equipment 2 to scrape the dried crystal powder from the surface downward, and the scraped crystal powder is pushed out to the first receiving bin 3 below the filtering, washing and drying three-in-one equipment 2 through the second unloading valve 25 using the inclined surface of the second stirring paddle 23.

[0050] In step S5, by using the filtering, washing and drying three-in-one equipment 2, compared with the use of decentralized and independently operated scraper-type bottom discharge centrifuge and double-cone vacuum dryer, the total time for filtering, washing and drying can be greatly reduced, thereby improving production capacity. There is no need to transfer materials between the decentralized and independently operated scraper-type bottom discharge centrifuge and double-cone vacuum dryer, thereby avoiding the risk of impurities being introduced.

[0051] Reference Figure 1 In one example, the method for producing bismuth hydroxide crystal powder also includes the step: S6, crushing, using the first vacuum feeder 41 to draw the crystal powder in the first receiving bin 3 to the buffer bin 42, weighing it through the weighing module 43, and then unloading it to the crusher 45 through the third discharge valve 44 below the buffer bin 42, and the crusher 45 crushes the crystal powder to the particle size required by the process, and finally discharges the crushed crystal powder into the second receiving bin 46. For example, in step S6, the crusher 45 is a hammer crusher, and the particle size range of the crushed crystal powder is 5-12μm. Continuous crushing, continuous unloading and continuous extraction are completed for 2h to crush and extract 1 ton of crystal powder. Compared with the conventional 30BV crusher, the hammer crusher can reduce the crushing time. In addition, the hammer crusher has a simple structure and control.

[0052] Reference Figure 1In one example, the method for producing bismuth hydroxide crystal powder further includes the step of: S7, homogenization and packaging, wherein the crushed crystal powder is pumped from the second receiving bin 46 to the homogenizer 52 through the second vacuum feeder 51 for homogenization, and the homogenized crystal powder is discharged into the automatic filling and packaging machine 54 through the fourth discharge valve 53 for quantitative filling and packaging of the barrel 55, and the barrel 55 after filling is transferred by the conveyor belt 57 and the mechanical arm 58 after passing through the re-weighing 56 to complete the production. Through the setting of step S6, the continuous production of homogenization, quantitative filling and packaging, re-weighing and transfer is realized, thereby improving the production capacity and reducing the labor cost.

[0053] In one example, the average particle size of the final bismuth hydroxide powder is between 5-12 μm, the bismuth hydroxide content in the final bismuth hydroxide powder is between 86-93%, and the water-soluble conductivity of the final bismuth hydroxide is between 250-270 μs / cm.

[0054] In the bismuth hydroxide crystal powder production method disclosed herein, the conductivity of purified water is less than 2 μs / cm.

[0055] [Bismuth Hydroxide Crystal Powder Production Line]

[0056] Reference Figures 1 to 3 The bismuth hydroxide crystal powder production line 1000 according to the present disclosure is at least applicable to the aforementioned bismuth hydroxide crystal powder production method.

[0057] The bismuth hydroxide crystal powder production line 1000 includes a synthesis kettle 1, a three-in-one filtering, washing and drying device 2, and a first receiving bin 3.

[0058] The synthesis reactor 1 is used for preparing bismuth nitrate solution, bismuth nitrate solution and ammonia precipitation reaction, sedimentation and impurity removal, and conversion and shaping to obtain a solid-liquid mixture containing bismuth hydroxide crystals. The filtering, washing and drying three-in-one device 2 is connected to the synthesis reactor 1, and the filtering, washing and drying three-in-one device 2 is used to receive the solid-liquid mixture containing bismuth hydroxide crystals from the synthesis reactor 1, filter the solid-liquid mixture, wash and filter the filtered bismuth hydroxide crystals, vacuum dry the washed and filtered bismuth hydroxide crystals to obtain dried bismuth hydroxide crystal powder, and use the second stirring paddle 23 of the filtering, washing and drying three-in-one device 2 to rotate and descend to scrape the dried crystal powder from the surface layer downward, and the scraped crystal powder is pushed out of the filtering, washing and drying three-in-one device 2 by the inclined surface of the second stirring paddle 23. The first receiving bin 3 is connected to the filtering, washing and drying three-in-one device 2, and the first receiving bin 3 is used to receive the dried bismuth hydroxide crystal powder discharged from the filtering, washing and drying three-in-one device 2.

[0059] When the bismuth hydroxide crystal powder production line 1000 according to the present disclosure executes the aforementioned bismuth hydroxide crystal powder production method, the process steps, operations, effects, etc. involved in the aforementioned bismuth hydroxide crystal powder production method will not be repeatedly described here.

[0060] In one example, refer to Figures 1 to 3 The synthesis reactor 1 comprises a reactor body 11, a first stirring paddle 12, a first jacket 13, and a first discharge valve 14. The first stirring paddle 12 is located in the reactor body 11 and is used for stirring. The first jacket 13 is arranged on the periphery of the reactor body 11 and is used for heating (for example, heating by passing steam). The first discharge valve 14 is connected to the bottom of the reactor body 11 and is used for discharging the solid-liquid mixture. The filtering, washing and drying three-in-one device 2 comprises a tank body 21, a filter cloth 22, a second stirring paddle 23, a second jacket 24, a second discharge valve 25, and a discharge mechanism 26. The tank body 21 is provided with a feed port 211, an air inlet 212, an exhaust valve 213, a cleaning port 214, and a filtrate outlet 215. The feed port 211 is connected to the first discharge valve 14 (as shown in the figure, the two are connected via an inclined pipe) to supply the solid-liquid mixture discharged from the first discharge valve 14 into the tank body 21. The air inlet 212 is used to introduce compressed air into the tank body 21 for pressurization. The exhaust valve 213 is used to connect to an external vacuum pumping mechanism (not shown) for vacuuming the tank body 21. The cleaning port 214 is used to supply purified water into the tank body 21. The filtrate outlet 215 is located at the bottom 216 of the tank body 21 and is used for the filtrate to be discharged from the tank body 21. The filter cloth 22 is located at the bottom 216 of the tank body 21 and is used for filtering. The second stirring paddle 23 is located in the tank body 21 and is used for stirring. The second jacket 24 is located at the periphery of the tank body 21 and is used for heating. The second discharge valve 25 is located on the side of the outer periphery of the bottom 216 of the tank body 21 away from the synthesis reactor 1. The discharge mechanism 26 is connected to the second discharge valve 25. The first receiving bin 3 is located below the discharge mechanism 26. For example, the mesh number of the filter cloth 22 is 700-1000 mesh. For example, the discharge mechanism 26 is in the form of a spiral conveying rod.

[0061] like Figure 3 As shown, in one example, the feed port 211 is located at the top of the tank body 21 ; the air inlet 212 is located at the top of the tank body 21 ; the exhaust valve 213 is located at the top of the tank body 21 ; and the cleaning port 214 is located at the top of the tank body 21 .

[0062] In order to improve the heating and heat preservation effect, in one example, a heating flow channel (for example, circulating steam) is provided inside the second stirring paddle 23; the bottom 216 of the tank body 21 is a bottom that can be heated (for example, a jacket is provided to pass steam) and can be disassembled (to facilitate the replacement of the filter cloth 22).

[0063] Further, refer to Figure 1The bismuth hydroxide crystal powder production line 1000 further includes a crushing module 4. The crushing module 4 is connected to the first receiving bin 3, and is used to receive the bismuth hydroxide crystal powder from the first receiving bin 3 and crush the received bismuth hydroxide crystal powder to a particle size required by the process.

[0064] Specifically, refer to Figure 1 The crushing module 4 includes a first vacuum loader 41 , a buffer bin 42 , a weighing module 43 , a third discharge valve 44 , a crusher 45 , and a second receiving bin 46 .

[0065] The first vacuum feeder 41 connects the first receiving bin 3 and the buffer bin 42, and the first vacuum feeder 41 is used to draw the crystal powder in the first receiving bin 3 to the buffer bin 42. The weighing module 43 is used to weigh the buffer bin 42 to determine the weight of the crystal powder drawn into the buffer bin 42. The third discharge valve 44 is arranged below the buffer bin 42 and connected between the buffer bin 42 and the crusher 45, and the third discharge valve 44 is used to discharge the crystal powder in the buffer bin 42 into the crusher 45. The crusher 45 is used to crush the crystal powder to the particle size required by the process. The second receiving bin 46 is connected below the crusher 45, and the second receiving bin 46 is used to receive the crystal powder crushed and discharged by the crusher 45. For example, the crusher 45 is a hammer crusher.

[0066] Reference Figure 1 In one example, the bismuth hydroxide crystal powder production line 1000 further includes a homogenizing and packaging module 5. The homogenizing and packaging module 5 is connected to the crushing module 4, and is used to receive the crushed bismuth hydroxide crystal powder from the crushing module 4, homogenize the crushed bismuth hydroxide crystal powder, and package the homogenized bismuth hydroxide crystal powder.

[0067] Specifically, the homogenizing and packaging module 5 includes a second vacuum feeder 51, a homogenizer 52, a fourth discharge valve 53, an automatic filling and packaging machine 54, a barrel 55, a re-weigher 56, a conveyor belt 57, and a robotic arm 58. The second vacuum feeder 51 connects the second receiving bin 46 and the homogenizer 52, and the second vacuum feeder 51 is used to draw the crushed crystal powder in the second receiving bin 46 into the homogenizer 52. The homogenizer 52 is used to mix the crushed crystal powder drawn into it by the second vacuum feeder 51 to achieve homogenization. The fourth discharge valve 53 is arranged below the homogenizer 52 and connected between the homogenizer 52 and the automatic filling and packaging machine 54, and the fourth discharge valve 53 is used to discharge the crystal powder homogenized by the homogenizer 52 into the automatic filling and packaging machine 54. The automatic filling and packaging machine 54 is used to quantitatively fill and package the barrel 55. The re-weigher 56 is used to re-weigh the barrel 55 after the automatic filling and packaging machine 54 has finished filling. The conveyor belt 57 and the mechanical arm 58 are used to transfer the barrel 55 after the re-weighing 56. For example, the homogenizer 52 is a twin-screw conical mixer.

[0068] Reference Figure 1 In one example, the bismuth hydroxide crystal powder production line 1000 also includes a steel frame platform 6, and a synthesis kettle 1, a three-in-one filtering, washing and drying equipment 2, a first receiving bin 3, a crushing module 4, and a homogenizing and packaging module 5 are arranged on the steel frame platform 6.

[0069] [test]

[0070] Example 1

[0071] Example 1 adopts the following steps:

[0072] S1, preparing a bismuth nitrate solution: first, inject 2000L of purified water into the kettle body 11 of the synthesis kettle 1 arranged on the steel frame platform 6 according to the volume ratio of industrial-grade nitric acid with a concentration of 68% and purified water of 1:1, and the conductivity of the purified water is 1μs / cm, then inject industrial-grade nitric acid with a concentration of 68%, start the first stirring paddle 12 for stirring, add bismuth oxide with a purity of 2N, the amount of bismuth oxide added is calculated based on the molar ratio of Bi to nitric acid of 1:3.5, the addition rate of bismuth oxide is 350kg / h, the dissolution temperature is controlled by the addition rate of bismuth oxide, steam is introduced through the first jacket 13 arranged on the outer periphery of the kettle body 11 to heat the temperature and control it at 55°C, continue stirring until the solution is completely dissolved and the volume is constant, and synthesize the bismuth nitrate solution;

[0073] S2, precipitation reaction of bismuth nitrate solution and ammonia water: the first stirring paddle 12 of the synthesis reactor 1 is turned on for stirring, and ammonia water with a mass fraction of 25% and a volume of 75% of the volume of the bismuth nitrate solution in step S1 is injected into the kettle body 11 of the synthesis reactor 1 at a rate of 600 L / h, and then the rate of adding ammonia water is immediately reduced to 150 L / h, and the pH is immediately detected to adjust the pH of the system to 1.2. When the pH is close to 1.2, the rate of adding ammonia water is further reduced to 75 L / h until the pH of the system is stable. During the reaction process, steam is introduced into the first jacket 13 provided on the outer periphery of the kettle body 11 to heat the solution and control the temperature of the solution at 55°C, and the reaction is continued for 3 hours in this temperature range. If the pH drops during the insulation process, ammonia water with a mass fraction of 25% is added to stabilize the pH. The pH stability is based on a change amplitude of less than 0.05 / min. Then, the first stirring paddle 12 is turned off for stirring, and the solution is allowed to stand for 30 minutes until the precipitate is completely settled, and the supernatant is removed;

[0074] S3, sedimentation and impurity removal: after the supernatant is removed, a volume of purified water corresponding to (i.e., the same as) the volume of the removed supernatant is added to the body 11 of the synthesis reactor 1, wherein the conductivity of the purified water is 1 μs / cm, the first stirring paddle 12 is turned on for stirring, and then industrial-grade 68% nitric acid is added to adjust the pH of the system to 1.2 for stability, wherein the pH stability is based on a change amplitude of less than 0.05 / min as a standard, and the system is stirred for 30 minutes, and steam is introduced through the first jacket 13 provided on the outer periphery of the body 11 for heating at a temperature of 55° C., and then the first stirring paddle 12 is turned off for stirring, and the system is allowed to stand for 30 minutes until the precipitate is completely settled, and then the supernatant is removed, and the above operation is repeated once (i.e., step S3 is performed twice), and the next operation is performed;

[0075] S4, conversion and finalization to obtain a solid-liquid mixture containing bismuth hydroxide crystals: add a volume of purified water corresponding to (i.e., the same as) the volume of the supernatant removed into the body 11 of the synthesis reactor 1, wherein the conductivity of the purified water is 1 μs / cm, start stirring, and after stirring until the system is uniform, steam is introduced through the first jacket 13 provided on the outer periphery of the body 11 and the system temperature is turned on and heated to 55° C., and then 25% by mass of ammonia water is added to the body 11 of the synthesis reactor 1 at a rate of 400 L / h to adjust the pH of the system to 7.3. After the pH is stable, the pH stability is based on a change amplitude of less than 0.05 / min as a standard, and the heat preservation reaction is continued for 2 hours. If the pH drops during the heat preservation process, 25% by mass of ammonia water is added to stabilize the pH. After the heat preservation reaction, the conversion and finalization of the bismuth hydroxide crystals are completed to obtain a solid-liquid mixture containing bismuth hydroxide crystals;

[0076] S5, filtering, washing and drying the solid-liquid mixture to obtain bismuth hydroxide crystal powder, step S5 comprises the following sub-steps:

[0077] S51, feeding, the solid-liquid mixture containing bismuth hydroxide crystals after the conversion and finalization in step S4 is discharged into the filtering, washing and drying three-stage filter 21 disposed on the steel frame platform 6 through the first discharge valve 14 of the synthesis reactor 1 and the feeding port 211 connected to the first discharge valve 14 and located at the top of the tank body 21.

[0078] In the tank 21 of the integrated device 2;

[0079] S52, after feeding, the first discharge valve 14 of the synthesis reactor 1 is closed, and compressed air is introduced into the tank body 21 of the filtering, washing and drying three-in-one device 2 through the air inlet 212 located at the top of the tank body 21 to increase the pressure, and the pressure is controlled at 0.3 MPa, and the solution in the solid-liquid mixture is discharged through the 800-mesh filter cloth 22 at the bottom 216 of the filtering, washing and drying three-in-one device 2, and the bismuth hydroxide crystals in the solid-liquid mixture remain in the tank body 21 of the filtering, washing and drying three-in-one device 2;

[0080] S53, washing and filtering, after the solution in the solid-liquid mixture is discharged, purified water is introduced through the cleaning port 214 located at the top of the tank body 21, and the conductivity of the purified water is 1μs / cm. The second stirring paddle 23 in the filtering, washing and drying three-in-one device 2 is turned on to stir and wash for 2 hours, and then compressed air is introduced through the air inlet 212 for pressurization, and the pressure is controlled at 0.3MPa. The washed purified water is discharged through the filter cloth 22, and the filtrate is discharged from the tank body 21 through the filtrate outlet 215 located at the bottom 216 of the tank body 21. Step S53 is performed 4 times in total, and clean crystals are obtained after the washing process;

[0081] S54, vacuum drying, the exhaust valve 213 is opened and the external vacuum pumping mechanism connected to the exhaust valve 213 is evacuated to make the tank body 21 of the three-in-one filtering, washing and drying device 2 have a negative pressure, and the negative pressure is 0.095MPa. Heating steam is introduced into the second jacket 24 located on the outer periphery of the tank body 21, and steam is introduced into the bottom 216 of the tank body 21 through the jacket provided thereon to increase the temperature in the tank body 21 of the three-in-one filtering, washing and drying device 2. Steam is introduced into the heated flow channel inside the second stirring paddle 23 to heat the second stirring paddle 23, and the second stirring paddle 23 is opened to stir and break up the crystal agglomerates, so that the filtering, washing and drying device 2 is dried and dried.

[0082] The temperature in the tank 21 of the drying three-in-one device 2 is raised to 95° C. and vacuum drying is performed for 7 hours;

[0083] S55, unloading, after vacuum drying is completed, open the exhaust valve 213 on the filtering, washing and drying three-in-one device 2, and after the air pressure in the tank body 21 of the filtering, washing and drying three-in-one device 2 is balanced, open the second unloading valve 25 of the filtering, washing and drying three-in-one device 2, and use the second stirring paddle 23 of the filtering, washing and drying three-in-one device 2 to rotate and descend to scrape the dried crystal powder from the surface layer downward, and the scraped crystal powder is pushed out by the inclined surface of the second stirring paddle 23 through the second unloading valve 25 on the outer periphery of the bottom 216 of the tank body 21 away from the synthesis reactor 1 to the unloading mechanism 26 of the filtering, washing and drying three-in-one device 2 in the form of a spiral conveying rod, and the unloading mechanism 26 conveys the crystal powder to the first receiving bin 3 arranged on the steel frame platform 6 below;

[0084] S6, using the crushing module 4 set on the steel frame platform 6 to crush, using the first vacuum feeder 41 of the ZKS-6 model purchased from Jiangsu Guibao Group Co., Ltd. to draw the crystal powder in the first receiving bin 3 to the buffer bin 42, weighing it through the weighing module 43, and then unloading it to the crusher 45 through the third discharge valve 44 under the buffer bin 42, the crusher 45 crushes the crystal powder to the particle size required by the process, and finally discharges the crushed crystal powder into the second receiving bin 46, wherein the crusher 45 is a hammer crusher of the HM-500 model purchased from Jiangsu Guibao Group Co., Ltd. The particle size range of the crushed crystal powder of the hammer crusher is 5-12μm, and continuous crushing, continuous unloading and continuous extraction are completed for 2h to crush and extract 1 ton of crystal powder;

[0085] S7, utilize the homogenizing and packaging module 5 set on the steel frame platform 6 for homogenizing and packaging, and use the second vacuum loader 51 of model ZKS-6 purchased from Jiangsu Guibao Group Co., Ltd. to draw the crushed crystal powder from the second receiving bin 46 to the homogenizer 52 in the form of a twin-screw conical mixer for homogenization, and the homogenized crystal powder is discharged into the automatic filling and packaging machine 54 through the fourth unloading valve 53 for quantitative filling and packaging of the barrel 55, and the barrel 55 after filling is transferred by the conveyor belt 57 and the robot arm 58 after the re-weighing 56 to complete the production.

[0086] Comparative Example 1

[0087] Except that step S3 is not executed, the rest is the same as embodiment 1.

[0088] Comparative Example 2

[0089] Except for step S5, the rest is the same as embodiment 1.

[0090] Step S5 is as follows using the following sub-steps:

[0091] S5a, the solid-liquid mixture containing bismuth hydroxide crystals after the conversion and finalization in step S4 is discharged into a scraper-type bottom discharge centrifuge through the first discharge valve 14 of the synthesis reactor 1 for centrifugal washing and filtration for 6 hours. The scraper-type bottom discharge centrifuge is purchased from Jiangsu Tusheng Centrifuge Manufacturing Co., Ltd.

[0092] LGZ1250 flat plate vertical scraper automatic bottom discharge centrifuge manufactured;

[0093] S5b, the bismuth hydroxide crystals obtained from the scraper-type bottom-discharging centrifuge are discharged and manually transferred to a double-cone vacuum dryer, which is purchased from Changzhou Pinzheng Drying Equipment Co., Ltd.

[0094] The company manufactures the SZG-1500 double cone rotary vacuum dryer;

[0095] S5c, dried in a double cone vacuum dryer for 24 h.

[0096] Comparative Example 3

[0097] The same as in Example 1 except that the crusher in step S6 adopts the S30BV crusher purchased from Jiangsu Guibao Group Co., Ltd., the particle size range of the crystal powder crushed by the S30BV crusher is 5-12μm, and continuous crushing, continuous unloading and continuous extraction take 4 hours to complete the crushing and extraction of 1 ton of crystal powder.

[0098] In Example 1, the average particle size of the bismuth hydroxide powder of the final product is between 5-12 μm, the bismuth hydroxide content in the bismuth hydroxide powder of the final product is 90% (detected by ICP), the water-soluble conductivity of the bismuth hydroxide of the final product is 260 μs / cm (detected by conductivity tester), and the impurity content (detected by ICP) is shown in Table 1.

[0099] Table 1 Impurity content of Example 1

[0100] Al / ppm Ca / ppm Fe / ppm Mg / ppm Na / ppm Si / ppm ＜0.5 ＜2.5 ＜3 ＜0.5 ＜0.5 ＜1.5

[0101] In Comparative Example 1, the average particle size of the bismuth hydroxide powder of the final product is between 5-12 μm, the bismuth hydroxide content in the bismuth hydroxide powder of the final product is 81%, the water-soluble conductivity of the bismuth hydroxide of the final product is 295 μs / cm, and the impurity content is shown in Table 2.

[0102] Table 2 Impurity content of comparative example 1

[0103] Al / ppm Ca / ppm Fe / ppm Mg / ppm Na / ppm Si / ppm ＜0.5 ＜2.5 ＜3 ＜0.5 ＜0.5 ＜1.5

[0104] From the comparison between Example 1 and Comparative Example 1, it can be seen that step S3 significantly improves the bismuth hydroxide content in the final bismuth hydroxide powder, that is, significantly improves the purity of the bismuth hydroxide in the final bismuth hydroxide powder.

[0105] In Comparative Example 2, the average particle size of the bismuth hydroxide powder of the final product is between 5-12 μm, the bismuth hydroxide content in the bismuth hydroxide powder of the final product is 88%, the water-soluble conductivity of the bismuth hydroxide of the final product is 270 μs / cm, and the impurity content is shown in Table 3.

[0106] Table 3 Impurity content of comparative example 2

[0107] Al / ppm Ca / ppm Fe / ppm Mg / ppm Na / ppm Si / ppm ＜0.5 ＜2.5 ＜3 ＜0.5 ＜0.5 ＜1.5

[0108] In Comparative Example 3, the average particle size of the bismuth hydroxide powder of the final product is between 5-12 μm, the bismuth hydroxide content in the bismuth hydroxide powder of the final product is 89%, the water-soluble conductivity of the bismuth hydroxide of the final product is 265 μs / cm, and the impurity content is shown in Table 3.

[0109] Table 4 Impurity content of comparative example 3

[0110] Al / ppm Ca / ppm Fe / ppm Mg / ppm Na / ppm Si / ppm ＜0.5 ＜2.5 ＜3 ＜0.5 ＜0.5 ＜1.5

[0111] From the comparison between Comparative Example 2 and Example 1, it can be seen that while achieving almost the same quality of the final product, the time taken for step S5a and step S5c of Comparative Example 2 (excluding manual transfer time) is 30 hours, and the time taken for step S53 (2h×4=8h) and step S54 (7h) of Example 1 is 15 hours. Under the same production capacity, compared with Comparative Example 2 (excluding manual transfer time), the time for washing, filtering and drying is saved by 50%.

[0112] From the comparison between Comparative Example 3 and Example 1, it can be seen that the hammer crusher can reduce the crushing time by 50% compared with the 30BV crusher while achieving almost the same final product quality.

[0113] The above detailed description is used to describe multiple exemplary embodiments, but this document is not intended to be limited to the explicitly disclosed combinations. Therefore, unless otherwise stated, the various features disclosed herein can be combined together to form multiple additional combinations that are not shown for the sake of simplicity.

Claims

1. A method for producing bismuth hydroxide crystal powder, It is characterized in that Includes steps: S1, preparing a bismuth nitrate solution: first, injecting purified water into a synthesis reactor (1) at a volume ratio of 68% industrial grade nitric acid to purified water of 1:1, then injecting 20-68% industrial grade nitric acid, starting stirring, adding bismuth oxide, wherein the amount of bismuth oxide added is calculated based on a molar ratio of Bi to nitric acid of 1:(3.1-4.0), and the addition rate of bismuth oxide is 300-400 kg / h. The dissolution temperature is controlled by the addition rate of bismuth oxide, and the temperature is controlled at 50-60° C., and stirring is continued until the bismuth oxide is completely dissolved and the volume is constant, thereby synthesizing a bismuth nitrate solution; S2, precipitation reaction of bismuth nitrate solution and ammonia water: start stirring of the synthesis reactor (1), inject 25-28% by mass of ammonia water into the synthesis reactor (1), adjust the pH value of the system to 1-1.3, until the pH value of the system is stable, control the solution temperature at 50-60°C during the reaction process, and keep the temperature within this range to continue the reaction for 2-3 hours. If the pH value drops during the insulation process, add 25-28% by mass of ammonia water to stabilize the pH value, then turn off stirring, let it stand for 30-40 minutes until the precipitate is completely settled, and remove the supernatant; S3, sedimentation and impurity removal: after the supernatant is removed, a volume of purified water corresponding to the removed supernatant is added to the synthesis reactor (1), stirring is started, and then industrial-grade nitric acid with a concentration of 20-68% is added to adjust the pH of the system to 1-1.3 and stabilize, stirring for 30-40 minutes at a temperature of 50-60° C., then stirring is turned off, and the mixture is allowed to stand for 30-40 minutes until all the precipitate is settled, and then the supernatant is removed. The above operation is repeated once, and the next step is performed; S4, converting and finalizing to obtain a solid-liquid mixture containing bismuth hydroxide crystals: adding purified water of a volume corresponding to the removed supernatant into the synthesis reactor (1), starting stirring, stirring until the system is uniform, starting heating to a system temperature of 50-60° C., then adding ammonia water of 25-28% by mass into the synthesis reactor (1) at a rate of 200-600 L / h, adjusting the system pH to 7-7.5, and continuing to keep the temperature for reaction for 2-3 hours after the pH stabilizes. If the pH drops during the heat preservation process, adding ammonia water to stabilize the pH. After the heat preservation reaction, the conversion and finalization of the bismuth hydroxide crystals is completed to obtain a solid-liquid mixture containing bismuth hydroxide crystals; S5, filtering, washing and drying the solid-liquid mixture to obtain bismuth hydroxide crystal powder.

2. The method for producing bismuth hydroxide crystal powder according to claim 1, It is characterized in that In step S2, step S3 and step S4, pH stability is based on a pH change amplitude of less than 0.05 / min.

3. The method for producing bismuth hydroxide crystal powder according to claim 1, It is characterized in that In step S2, the synthesis reactor (1) is stirred, and ammonia water with a mass fraction of 25-28% and a volume of 70-80% of the volume of the bismuth nitrate solution in step S1 is added into the synthesis reactor 1 at a rate of 500-700 L / h, and then the rate of adding ammonia water is immediately reduced to 100-200 L / h, and the pH is immediately detected to adjust the pH of the system to 1-1.

3. When the pH is close to the range of 1-1.3, the rate of adding ammonia water is further reduced to 50-100 L / h until the pH of the system is stable.

4. The method for producing bismuth hydroxide crystal powder according to claim 1, It is characterized in that Step S5 includes sub-steps: S51, feeding, discharging the solid-liquid mixture containing bismuth hydroxide crystals after the conversion and finalization in step S4 into the filtering, washing and drying three-in-one device (2) through the first discharge valve (14) of the synthesis reactor (1); S52, after feeding, close the first discharge valve (14) of the synthesis reactor (1), and introduce compressed air into the filtering, washing and drying three-in-one device (2) to increase the pressure, and control the pressure at 0.2-0.3 MPa. The solution in the solid-liquid mixture is discharged through a 700-1000 mesh filter cloth (22) at the bottom (216) of the filtering, washing and drying three-in-one device (2), and the bismuth hydroxide crystals in the solid-liquid mixture remain in the filtering, washing and drying three-in-one device (2); S53, washing and filtering, after the solution in the solid-liquid mixture is discharged, purified water is introduced, the second stirring paddle (23) in the filtering, washing and drying three-in-one device (2) is turned on to stir and wash for 1-2 hours, and then compressed air is introduced to pressurize, and the pressure is controlled at 0.2-0.3MPa, and the washed purified water is discharged through the filter cloth (22), and step S53 is performed 3-4 times in total, and clean crystals are obtained after the washing and filtering process; S54, vacuum drying, start vacuuming to make the three-in-one filtering, washing and drying device (2) have a negative pressure, the negative pressure is higher than 0.095 MPa but lower than atmospheric pressure, introduce heating steam into the second jacket (24) to raise the temperature inside the three-in-one filtering, washing and drying device (2), start stirring to break up crystal agglomerates, raise the temperature inside the three-in-one filtering, washing and drying device (2) to 80-95° C., and perform vacuum drying for 5-7 hours; S55, unloading, after vacuum drying is completed, open the exhaust valve (213) on the filtering, washing and drying three-in-one device (2) to balance the air pressure in the filtering, washing and drying three-in-one device (2), The second discharge valve (25) of the three-in-one filtering, washing and drying device (2) is opened, and the dried crystal powder is scraped downward from the surface layer by the rotation and descent of the second stirring paddle (23) of the three-in-one filtering, washing and drying device (2), and the scraped crystal powder is pushed out through the second discharge valve (25) to the first receiving bin (3) below the three-in-one filtering, washing and drying device (2) by the inclined surface of the second stirring paddle (23).

5. The method for producing bismuth hydroxide crystal powder according to claim 1, It is characterized in that The method for producing bismuth hydroxide crystal powder also includes the steps of: S6, crushing, using the first vacuum loader (41) to draw the crystal powder in the first receiving bin (3) into the buffer bin (42), weighing it through the weighing module (43), and then unloading it into the crusher (45) through the third unloading valve (44) below the buffer bin (42). The crusher (45) crushes the crystal powder to the particle size required by the process, and finally discharges the crushed crystal powder into the second receiving bin (46).

6. The method for producing bismuth hydroxide crystal powder according to claim 5, It is characterized in that In step S6, the pulverizer (45) is a hammer crusher, and the particle size range of the crushed crystal powder is 5-12 μm. Continuous crushing, continuous unloading, and continuous extraction are performed for 2 hours to complete the crushing and extraction of 1 ton of crystal powder.

7. The method for producing bismuth hydroxide crystal powder according to claim 5, It is characterized in that The method for producing bismuth hydroxide crystal powder also includes the steps of: S7, homogenization and packaging, the crushed crystal powder is pumped from the second receiving bin (46) to the homogenizer (52) through the second vacuum loader (51) for homogenization, and the crystal powder after homogenization is discharged into the automatic filling and packaging machine (54) through the fourth discharge valve (53) for quantitative filling and packaging of the barrel (55). After the filling, the barrel (55) is transferred by the conveyor belt (57) and the robot arm (58) after the re-weighing (56), and the production is completed.

8. A bismuth hydroxide crystal powder production line, It is characterized in that At least applicable to the method for producing bismuth hydroxide crystal powder according to any one of claims 1 to 4, The bismuth hydroxide crystal powder production line (1000) comprises a synthesis kettle (1), a three-in-one filtering, washing and drying device (2), and a first material receiving bin (3); The synthesis reactor (1) is used for preparing a bismuth nitrate solution, performing a precipitation reaction between the bismuth nitrate solution and ammonia water, performing sedimentation and impurity removal, and performing conversion and shaping to obtain a solid-liquid mixture containing bismuth hydroxide crystals; The three-in-one filtering, washing and drying device (2) is connected to the synthesis reactor (1), and is used for receiving a solid-liquid mixture containing bismuth hydroxide crystals from the synthesis reactor (1), filtering the solid-liquid mixture, washing and filtering the filtered bismuth hydroxide crystals, vacuum drying the washed and filtered bismuth hydroxide crystals to obtain dried bismuth hydroxide crystal powder, and scraping the dried crystal powder from the surface layer downward by rotating and descending the stirring paddle, and pushing the scraped crystal powder out of the three-in-one filtering, washing and drying device (2) by using the inclined surface of the stirring paddle; The first receiving bin (3) is connected to the three-in-one filtering, washing and drying device (2), and the first receiving bin (3) is used to receive the dried bismuth hydroxide crystal powder discharged from the three-in-one filtering, washing and drying device (2).

9. The bismuth hydroxide crystal powder production line according to claim 8, It is characterized in that The synthesis reactor (1) comprises a reactor body (11), a first stirring paddle (12), a first jacket (13), and a first discharge valve (14); the first stirring paddle (12) is located in the reactor body (11) and is used for stirring; the first jacket (13) is located on the outer periphery of the reactor body (11) and is used for heating; and the first discharge valve (14) is connected to the bottom of the reactor body (11) and is used for discharging a solid-liquid mixture; The three-in-one filtering, washing and drying device (2) comprises a tank body (21), a filter cloth (22), a second stirring paddle (23), a second jacket (24), a second discharge valve (25), and a discharge mechanism (26); The tank body (21) is provided with a feeding port (211), an air inlet (212), an exhaust valve (213), a cleaning port (214), and a filtrate outlet (215); the feeding port (211) is connected to the first discharge valve (14) to supply the solid-liquid mixture discharged from the first discharge valve (14) into the tank body (21); the air inlet (212) is used to introduce compressed air into the tank body (21) for pressurization; the exhaust valve (213) is used to connect to an external vacuum pumping mechanism for vacuuming the tank body (21); the cleaning port (214) is used to supply purified water into the tank body (21); and the filtrate outlet (215) is located at the bottom (216) of the tank body (21) and is used to discharge the filtrate out of the tank body (21); The filter cloth (22) is located at the bottom (216) of the tank (21) and is used for filtering; The second stirring paddle (23) is located in the tank body (21) and is used for stirring; The second jacket (24) is located on the outer periphery of the tank body (21) and is used for heating; The second discharge valve (25) is located on the outer periphery of the bottom (216) of the tank body (21) on the side away from the synthesis reactor (1); The discharge mechanism (26) is connected to the second discharge valve (25); The first material receiving bin (3) is located below the material discharging mechanism (26).

10. The bismuth hydroxide crystal powder production line according to claim 9, It is characterized in that A heated flow channel is provided inside the second stirring paddle (23); The bottom (216) of the tank body (21) is heatable and detachable.

11. The bismuth hydroxide crystal powder production line according to claim 8, It is characterized in that The bismuth hydroxide crystal powder production line (1000) further comprises a crushing module (4), The crushing module (4) is connected to the first receiving bin (3), and is used to receive bismuth hydroxide crystal powder from the first receiving bin (3) and crush the received bismuth hydroxide crystal powder to a particle size required by the process.

12. The bismuth hydroxide crystal powder production line according to claim 11, It is characterized in that The crushing module (4) comprises a first vacuum feeder (41), a buffer bin (42), a weighing module (43), a third discharge valve (44), a crusher (45), and a second receiving bin (46). The first vacuum feeder (41) connects the first receiving bin (3) and the buffer bin (42), and the first vacuum feeder (41) is used to pump the crystal powder in the first receiving bin (3) into the buffer bin (42); The weighing module (43) is used to weigh the buffer bin (42) to determine the weight of the crystal powder drawn into the buffer bin (42); The third discharge valve (44) is arranged below the buffer bin (42) and connected between the buffer bin (42) and the pulverizer (45), and the third discharge valve (44) is used to discharge the crystal powder in the buffer bin (42) into the pulverizer (45); The pulverizer (45) is used to pulverize the crystal powder to a particle size required by the process; The second material receiving bin (46) is connected to the lower part of the pulverizer (45), and the second material receiving bin (46) is used to receive the crystal powder discharged from the pulverizer (45).

13. The bismuth hydroxide crystal powder production line according to claim 12, It is characterized in that The pulverizer (45) is a hammer crusher.

14. The bismuth hydroxide crystal powder production line according to claim 11, It is characterized in that The bismuth hydroxide crystal powder production line (1000) further comprises a homogenizing and packaging module (5), The homogenizing and packaging module (5) is connected to the pulverizing module (4), and is used for receiving the pulverized bismuth hydroxide crystal powder from the pulverizing module (4), homogenizing the pulverized bismuth hydroxide crystal powder, and packaging the homogenized bismuth hydroxide crystal powder.

15. The bismuth hydroxide crystal powder production line according to claim 14, It is characterized in that The homogenizing and packaging module (5) comprises a second vacuum loading machine (51), a homogenizer (52), a fourth discharge valve (53), an automatic filling and packaging machine (54), a material barrel (55), a re-weighing machine (56), a conveyor belt (57), and a mechanical arm (58); The second vacuum feeder (51) connects the second material receiving bin (46) and the homogenizer (52), and the second vacuum feeder (51) is used to pump the crushed crystal powder in the second material receiving bin (46) into the homogenizer (52); The homogenizer (52) is used to mix the crushed crystal powder sucked into it by the second vacuum feeder (51) to achieve homogeneity; The fourth discharge valve (53) is arranged below the homogenizer (52) and connected between the homogenizer (52) and the automatic filling and packaging machine (54). The fourth discharge valve (53) is used to discharge the crystal powder homogenized by the homogenizer (52) into the automatic filling and packaging machine (54); The automatic filling and packaging machine (54) is used for quantitative filling and packaging of the barrel (55); The re-weigher (56) is used to re-weigh (56) the material barrel (55) after the automatic filling and packaging machine (54) has finished filling; The conveyor belt (57) and the mechanical arm (58) are used to transfer the material barrel (55) after the re-weighing (56).

16. The bismuth hydroxide crystal powder production line according to claim 15, It is characterized in that The homogenizer (52) is a twin-screw conical mixer.

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