Bismuth nitrate pentahydrate cooling crystallization device

Abstract

The bismuth nitrate pentahydrate cooling crystallization device comprises an L-shaped framework, a crystallization kettle is fixed to the outer wall of one side of the L-shaped framework, a kettle cover is connected to the top end of the crystallization kettle in a bolted mode, and a feeding structure used for introducing a bismuth nitrate saturated solution is installed on the outer wall of the side, away from the L-shaped framework, of the crystallization kettle; the constant-temperature circulator is mounted on the peripheral surface of the crystallization kettle, a supporting disc is fixed at one end in the crystallization kettle, and a double-layer cage type cooling crystallization assembly for forming bismuth nitrate pentahydrate crystals is mounted at the bottom end of the supporting disc. The introduction time of circulating cooling water in the double-layer cage type cooling crystallization assembly is controlled, the growth process of the crystals is optimized, it is ensured that the bismuth nitrate pentahydrate crystals obtain ideal particle size distribution in the forming process, the purity and stability of products are improved through large and uniform crystal particles, and the production cost is reduced. And the problems of increased surface area, easy deliquescence and the like caused by too small crystals are also reduced.

Description

Technical Field

[0001] The invention relates to the technical field of production of bismuth series chemical products, in particular to a cooling crystallization device for bismuth nitrate pentahydrate. Background Art

[0002] Bismuth nitrate pentahydrate is a colorless and shiny crystal that is easily deliquescent and slightly soluble in water. It decomposes into bismuth subnitrate in water and dissolves in dilute nitric acid. It is mainly used in pharmaceutical manufacturing and bismuth deep processing. The factory produces bismuth nitrate pentahydrate with refined bismuth or bismuth oxide as raw materials, adds nitric acid to dissolve into a saturated solution of bismuth nitrate, and cools and stirs to crystallize to obtain bismuth nitrate pentahydrate. The cooling process needs to be carried out slowly and evenly to allow the bismuth nitrate molecules enough time to arrange in order and crystallize. At the same time, by precisely controlling the crystallization conditions, such as temperature, stirring mode and time, the growth of crystals can be optimized, thereby obtaining larger and more stable bismuth nitrate pentahydrate crystals. However, during the cooling and stirring crystallization process of bismuth nitrate, bismuth nitrate often crystallizes and precipitates in the form of powder, and the finished product has a small particle size, is easy to deliquesce and harden, and is inconvenient for long-term storage and use. For example, the production method of bismuth nitrate pentahydrate disclosed in the application publication number CN114560499A comprises the following steps: step 1, adding nitric acid, purified water and bismuth oxide to a dissolving kettle, heating and dissolving to obtain a saturated bismuth nitrate solution, keeping the temperature and filtering to remove insoluble matter, and transferring the filtered clear solution to a crystallization kettle; step 2, adding bismuth nitrate pentahydrate crystals as seed crystals to the crystallization kettle, and controlling the crystal size by controlling the cooling rate; step 3, reacting in the crystallization kettle The material after the solid-liquid separation is carried out by centrifugation, and the pentahydrate bismuth nitrate product is obtained after centrifugal unloading; the mother liquor is replaced by a low-acidity saturated bismuth nitrate solution in the centrifugation process, and the mother liquor and the solution produced by the replacement can be returned to the dissolution process in step one. The technical scheme is to control the crystal size by adding bismuth nitrate pentahydrate seeds and controlling the cooling rate. This production method has little effect in actual production. The reason is that during the cooling and crystallization process, if stirring is not turned on, the crystal will be hardened, and as long as stirring is turned on, the formed crystal structure will be destroyed, resulting in crystal breakage, and the crystal will still be crystallized and precipitated in the form of powder, and it is difficult to obtain large-particle crystals. The crystals in this powder form not only have a small particle size, but also a large surface area, and are more likely to absorb moisture in the air and deliquesce, thereby affecting the storage stability and use effect of the product. Summary of the invention

[0003] The object of the present invention is to provide a bismuth nitrate pentahydrate cooling crystallization device, wherein a saturated bismuth nitrate solution enters a crystallization kettle through a feeding structure, a first water pump connects an external heating system to a constant temperature circulator of the device, and maintains a system temperature of 60-65°C, a double-layer cage cooling crystallization component is connected to an external circulating cooling system by a second water pump, after circulating cooling water is passed into the double-layer cage cooling crystallization component for 30 minutes, the negative pressure generated by the second water pump and the external circulating cooling system is utilized to make the crystallizer tube body in the double-layer cage cooling crystallization component deflate, and the crystals attached to the crystallizer tube body will naturally fall off and sink to the bottom of the crystallization kettle, and the size of the crystal particles formed by bismuth nitrate pentahydrate on the crystallizer can be effectively controlled by adjusting the time when the circulating cooling water is passed into the double-layer cage cooling crystallization component, and during the cooling crystallization process, a rotary drive unit drives a double-ring agitator to stir the solution, accelerates the crystallization of the solution on the crystallizer tube wall, and prevents the crystals from sinking to the bottom and hardening, so as to solve the problems raised in the above-mentioned background technology.

[0004] To achieve the above object, the present invention provides the following technical solution: a cooling crystallization device for bismuth nitrate pentahydrate, comprising:

[0005] An L-shaped frame, a crystallization kettle is fixed on the outer wall of one side of the L-shaped frame, and a kettle cover is bolted to the top of the crystallization kettle, and a feeding structure for passing a saturated bismuth nitrate solution is installed on the outer wall of the crystallization kettle away from the L-shaped frame;

[0006] A constant temperature circulator, the constant temperature circulator is installed on the outer peripheral surface of the crystallization kettle, a support plate is fixed at one end inside the crystallization kettle, and a double-layer cage cooling crystallization component for forming bismuth nitrate pentahydrate crystals is installed at the bottom end of the support plate, a double-ring agitator for stirring a saturated bismuth nitrate solution and preventing bismuth nitrate pentahydrate crystals from crystallizing on the inner wall of the crystallization kettle is installed at the center position of the bottom end of the support plate, and a rotary drive unit for driving the double-ring agitator is installed at the center position of the top end of the kettle cover;

[0007] A discharge pipe is installed at the center of the bottom end of the crystallization kettle. A PLC control panel is installed on the outer wall of one side of the L-shaped frame. The output end of the PLC control panel is electrically connected to the input end of the rotary drive unit, the feed structure, and the constant temperature circulator.

[0008] Preferably, the feed structure includes a feed transverse pipe installed on the outer wall of one side of the crystallization kettle, a corrugated steel pipe threadedly installed on the top of the feed transverse pipe, and a feed solenoid valve installed on the top of the corrugated steel pipe, and a discharge valve is installed at the bottom end of the discharge pipe.

[0009] Preferably, the constant temperature circulator includes a liquid storage jacket installed on the outer peripheral surface of the crystallization kettle, a liquid discharge pipe head installed on the outer wall of one side of the liquid storage jacket, and a liquid injection pipe head installed on the outer wall of the other side of the liquid storage jacket, and a cavity for retaining cooling liquid is provided between the inner wall of the liquid storage jacket and the outer wall of the crystallization kettle.

[0010] Preferably, the double-layer cage-type cooling crystallization assembly includes a plurality of external crystallization tube bodies connected in series and a plurality of internal crystallization tube bodies connected in series and fixed at the bottom end of the support plate, the structures of the external crystallization tube bodies and the internal crystallization tube bodies are the same, a short U-shaped conducting tube is installed between the discharge port of one of the internal crystallization tube bodies and the liquid inlet of one of the external crystallization tube bodies, a U-shaped conducting tube 2 is installed between the head and tail ends of several of the internal crystallization tube bodies, a U-shaped conducting tube 1 is installed between the head and tail ends of several of the external crystallization tube bodies, and the double-ring agitator is located in the area between the several internal crystallization tube bodies.

[0011] Preferably, one of the liquid inlets of the crystallization kettle is equipped with a liquid inlet pipe, the top of which passes through the outside of the kettle cover, and a liquid inlet solenoid valve is installed on the top of the liquid inlet pipe; and one of the liquid outlets of the external crystallization tube body is equipped with a liquid outlet pipe, one end of which passes through the outside of the kettle cover and is equipped with a liquid outlet solenoid valve.

[0012] Preferably, the external crystallization tube body consists of a tube seat, a hose and a diaphragm, the tube seat is fixed to the bottom end of the support plate, the hose is fixed to the bottom end of the tube seat, the diaphragm is installed inside the hose and divides the hose into two interconnected chambers, the hose is made of polytetrafluoroethylene material, and water inlets and outlets that are interconnected with the chambers are respectively installed on both sides of the top end of the tube seat.

[0013] Preferably, the double-ring agitator includes a vertical shaft rotatably mounted at the center position inside the support plate, a T-arm integrally formed at the bottom end of the vertical shaft, and a support ring fixed on the upper surface of the T-arm, a plurality of scrapers are evenly spacedly mounted on the top of the support ring, one side of the scraper is in contact with the inner wall of the crystallization kettle, and stirring blades are mounted at both ends of the surface of the vertical shaft.

[0014] Preferably, the rotary drive unit includes a conical motor seat fixed to the top of the kettle cover, a shaft tube installed at the center position inside the conical motor seat, and a reduction motor installed at the top of the conical motor seat. The output end of the reduction motor is fixedly connected to the top of the vertical shaft through a coupling, and ball bearings are installed at both ends of the shaft tube.

[0015] Preferably, a sampling structure is provided inside the discharge pipe.

[0016] Preferably, the sampling structure includes a bending tube installed inside the discharge tube, a ring tube installed at the top end of the bending tube, and a sampling valve installed at the bottom end of the bending tube, and a plurality of through holes are provided on the upper surface of the ring tube.

[0017] Compared with the prior art, the invention has the following beneficial effects: the pentahydrate bismuth nitrate cooling crystallization device can optimize the crystal growth process by accurately controlling the introduction time of circulating cooling water in the double-layer cage cooling crystallization component, ensuring that the pentahydrate bismuth nitrate crystals obtain an ideal particle size distribution during the formation process, and the larger and more uniform crystal particles not only improve the purity and stability of the product, but also reduce the problems of increased surface area and easy deliquesce caused by too small crystals, thereby extending the storage life and use effect of the product, while the rotary drive unit and the double-ring agitator accelerate the crystallization speed of the solution on each tube wall of the double-layer cage cooling crystallization component, and the continuous stirring also effectively prevents the deposition and agglomeration of the crystal grains on the bottom or tube wall of the crystallization kettle, avoiding the decrease in production efficiency caused by blockage or uneven crystallization, and making the crystallizer tube body in the double-layer cage cooling crystallization component deflate and naturally fall off the crystal, and this process does not require additional mechanical devices or chemical reagents, reduces energy consumption and waste emissions, and pumps the remaining solution back to the mother liquor kettle for reuse, thereby realizing the recycling of resources and minimization of waste. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the main structure of the present invention;

[0019] Figure 2 It is a schematic diagram of the main cross-sectional structure of the present invention;

[0020] Figure 3 The three-dimensional structure of the present invention is shown in FIG. Figure 1 ;

[0021] Figure 4 The three-dimensional structure of the present invention is shown in FIG. Figure 2 ;

[0022] Figure 5 It is a schematic diagram of a three-dimensional cross-sectional structure of the present invention;

[0023] Figure 6 This is a schematic diagram of the three-dimensional structure of a double-layer cage-type cooling crystallization component according to the second embodiment of the present invention;

[0024] Figure 7 This is a schematic diagram of a three-dimensional cross-sectional structure of an outer crystal tube body according to a second embodiment of the present invention;

[0025] Figure 8 It is a schematic diagram of a three-dimensional cross-sectional structure of a third embodiment of the present invention;

[0026] Fig. 9This is a schematic diagram of the three-dimensional structure of a rotation drive unit according to Embodiment 3 of the present invention;

[0027] Fig.10 It is a schematic diagram of the three-dimensional cross-sectional structure of the double-ring agitator of the third embodiment of the present invention.

[0028] In the figure: 1. L-shaped frame; 101. Feed structure; 102. Feed transverse pipe; 103. Corrugated steel pipe; 104. Feed solenoid valve; 2. Crystallization kettle; 3. Kettle cover; 4. Support plate; 5. Double-layer cage cooling crystallization assembly; 501. External crystallization tube body; 5011. Tube seat; 5012. Hose; 5013. Diaphragm; 5014. Water outlet; 5015. Water inlet; 502. Internal crystallization tube body; 503. U-shaped conducting pipe 1; 504. U-shaped conducting pipe 2; 505. Liquid inlet pipe; 506. Liquid inlet solenoid valve ; 507, liquid outlet pipe; 508, liquid outlet solenoid valve; 509, short U-shaped guide pipe; 6, constant temperature circulator; 601, liquid storage sleeve; 602, cavity; 603, liquid injection pipe head; 604, liquid discharge pipe head; 7, double-ring agitator; 701, vertical shaft; 702, T-arm; 703, support ring; 704, scraper; 705, stirring blade; 8, rotary drive unit; 801, cone-mouth motor seat; 802, reduction motor; 803, shaft tube; 9, discharge pipe; 10, sampling structure; 11, PLC control panel. DETAILED DESCRIPTION

[0029] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings in the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] Embodiment 1, by Figures 1 to 5 The present invention comprises an L-shaped frame 1, a crystallization kettle 2 is fixed on the outer wall of one side of the L-shaped frame 1, and a kettle cover 3 is bolted to the top of the crystallization kettle 2, and a feeding structure 101 for introducing a saturated bismuth nitrate solution is installed on the outer wall of the crystallization kettle 2 away from the L-shaped frame 1;

[0031] A constant temperature circulator 6, which is installed on the outer peripheral surface of the crystallization kettle 2, a support plate 4 is fixed at one end inside the crystallization kettle 2, and a double-layer cage cooling crystallization component 5 for forming bismuth nitrate pentahydrate crystals is installed at the bottom end of the support plate 4, a double-ring agitator 7 for stirring the saturated bismuth nitrate solution and preventing bismuth nitrate pentahydrate crystals from crystallizing on the inner wall of the crystallization kettle 2 is installed at the center position of the bottom end of the support plate 4, and a rotary drive unit 8 for driving the double-ring agitator 7 to work is installed at the center position of the top end of the kettle cover 3;

[0032] A discharge pipe 9 is installed at the center of the bottom end of the crystallization kettle 2. A PLC control panel 11 is installed on the outer wall of one side of the L-shaped frame 1. The output end of the PLC control panel 11 is electrically connected to the input end of the rotation drive unit 8, the feeding structure 101, and the constant temperature circulator 6;

[0033] The feeding structure 101 includes a feeding transverse tube 102 installed on the outer wall of one side of the crystallization kettle 2, a corrugated steel pipe 103 threadedly installed on the top of the feeding transverse tube 102, and a feeding solenoid valve 104 installed on the top of the corrugated steel pipe 103. The bottom end of the discharge pipe 9 is equipped with a discharge valve. The staff passes the saturated bismuth nitrate solution into the feeding solenoid valve 104 and the corrugated steel pipe 103. At this time, the staff turns on the feeding solenoid valve 104 in a normally open state through the PLC control panel 11, so that the saturated bismuth nitrate solution is injected into the crystallization kettle 2 through the feeding solenoid valve 104, the corrugated steel pipe 103, and the feeding transverse tube 102;

[0034] The constant temperature circulator 6 includes a liquid storage sleeve 601 installed on the outer peripheral surface of the crystallization kettle 2, a liquid discharge pipe head 604 installed on the outer wall of one side of the liquid storage sleeve 601, and a liquid injection pipe head 603 installed on the outer wall of the other side of the liquid storage sleeve 601. A cavity 602 for retaining coolant is provided between the inner wall of the liquid storage sleeve 601 and the outer wall of the crystallization kettle 2. The external heating system and the pump liquid pipe of the first water pump are connected to the liquid discharge pipe head 604, so that hot water is injected into the cavity 602, so that the liquid storage sleeve 601, the crystallization kettle 2 and the saturated bismuth nitrate solution inside the crystallization kettle 2 can be heated, and the temperature of the solution inside the crystallization kettle can be controlled. In this process, the hot water after heat exchange is discharged from the outside of the liquid storage sleeve 601 through the liquid injection pipe head 603. At the same time, the double-layer cage cooling crystallization component 5 is connected to the external cooling water system to cool the solution inside the crystallization kettle 2, realizing dual-purpose in one.

[0035] Embodiment 2, based on embodiment 1, Figure 6 and Figure 7The double-layer cage cooling crystallization assembly 5 includes a plurality of mutually connected external crystallization tube bodies 501 and a plurality of mutually connected internal crystallization tube bodies 502 fixed at the bottom end of the support plate 4. The external crystallization tube bodies 501 and the internal crystallization tube bodies 502 have the same structure. A short U-shaped conducting tube 509 is installed between the discharge port of one of the internal crystallization tube bodies 502 and the liquid inlet of one of the external crystallization tube bodies 501. A U-shaped conducting tube 2 504 is installed between the head and tail ends of the plurality of internal crystallization tube bodies 502. A U-shaped conducting pipe 503 is installed between the head and tail ends of the body 501, and the double-ring agitator 7 is located in the area between the plurality of inner crystallization tube bodies 502. A liquid inlet pipe 505 is installed at the liquid inlet of one of the crystallization kettles 2, and the top of the liquid inlet pipe 505 penetrates to the outside of the kettle cover 3, and a liquid inlet solenoid valve 506 is installed at the top of the liquid inlet pipe 505. A liquid outlet pipe 507 is installed at the liquid outlet of one of the outer crystallization tube bodies 501, and one end of the liquid outlet pipe 507 penetrates to the outside of the kettle cover 3 and is installed with a liquid outlet solenoid valve 508.

[0036] The double-layer cage cooling crystallization component 5 is connected to the external circulation cooling system through the liquid inlet solenoid valve 506 and the liquid outlet solenoid valve 508, and the low-temperature cooling liquid enters one of the inner crystallization tube bodies 502 through the liquid inlet solenoid valve 506 and the liquid inlet pipe 505. The U-shaped conducting pipe 2 504 and the U-shaped conducting pipe 1 503 respectively play the role of connecting several inner crystallization tube bodies 502 and several outer crystallization tube bodies 501 in series, and one of the short U-shaped conducting pipes 509 also plays the role of connecting the inner crystallization tube body 502 and the outer crystallization tube body 501. At this time, the flow path of the cooling liquid is the liquid inlet solenoid valve 506, the liquid inlet pipe 505, the inner crystallization tube body 502, the short U-shaped conducting pipe 509, the U-shaped conducting pipe 1 503, the liquid outlet pipe 507 and the liquid outlet solenoid valve 508, so that the temperature of each outer crystallization tube body 501 and the inner crystallization tube body 502 can be reduced;

[0037] By controlling the time of circulating cooling water, the size of the crystal particles formed by bismuth nitrate on the crystallizer can be effectively controlled; the structural design of the double-layer cage cooling crystallization component 5 also makes the cooling structure more compact, reduces the space occupied by the cooling structure inside the crystallization kettle 2, and does not affect the normal operation of the double-ring agitator 7;

[0038] The outer crystal tube body 501 is composed of a tube seat 5011, a hose 5012 and a diaphragm 5013. The tube seat 5011 is fixed to the bottom end of the support plate 4, the hose 5012 is fixed to the bottom end of the tube seat 5011, the diaphragm 5013 is installed inside the hose 5012 and divides the hose 5012 into two chambers interconnected with each other, the hose 5012 is made of polytetrafluoroethylene material, and the two sides of the top of the tube seat 5011 are respectively installed with a water inlet 5015 and a water outlet 5014 interconnected with the chamber. The outer crystal tube body 501 and the inner crystal tube body 502 are both made of polytetrafluoroethylene material. At this time, the coolant enters the hose 5012 through the water inlet 5015. Since the diaphragm 5013 divides the tube seat 5011 into two chambers, the coolant flows from the water inlet 5015 side to the water outlet 5014 side and enters the next outer crystal tube body 501;

[0039] By closing the liquid inlet solenoid valve 506, the external circulating water pump continues to work, so that negative pressure is formed inside the crystallizer tube and it becomes deflated, and the crystals attached to the crystallizer tube will naturally fall off and sink to the bottom of the crystallization kettle.

[0040] Embodiment 3, based on embodiment 2, Figure 8 , Fig. 9 and Fig.10 It is given that the double-ring agitator 7 includes a vertical shaft 701 rotatably mounted at the inner center of the support disk 4, a T-arm 702 integrally formed at the bottom end of the vertical shaft 701, and a support ring 703 fixed on the upper surface of the T-arm 702, a plurality of scrapers 704 are evenly spacedly mounted on the top of the support ring 703, one side of the scraper 704 is in contact with the inner wall of the crystallization kettle 2, stirring blades 705 are mounted on both ends of the surface of the vertical shaft 701, and the rotation drive unit 8 includes a conical motor seat 801 fixed to the top of the kettle cover 3, a shaft tube 803 mounted at the inner center of the conical motor seat 801, and a reduction motor 802 mounted on the top of the conical motor seat 801, the output end of the reduction motor 802 is fixedly connected to the top of the vertical shaft 701 through a coupling, and ball bearings are mounted on both ends of the shaft tube 803;

[0041] The staff turns on the reduction motor 802 through the PLC control panel 11 to work, and the reduction motor 802 drives the vertical shaft 701 and the T-arm 702 to rotate in sequence, and the stirring blade 705 mixes the solution in the vertical central axis area of ​​the crystallization kettle 2 to prevent the crystals from being deposited and hardened at the bottom of the crystallization kettle, and the support ring 703 serves to connect the T-arm 702 and the scraper 704. At this time, the scraper 704 actively scrapes off the crystals on the inner wall of the crystallization kettle 2 to prevent the crystals from adhering to the kettle wall;

[0042] A sampling structure 10 is provided inside the discharge pipe 9, and the sampling structure 10 includes a bent tube installed inside the discharge pipe 9, a ring tube installed at the top of the bent tube, and a sampling valve installed at the bottom of the bent tube. A plurality of through holes are provided on the upper surface of the ring tube. When the staff needs to sample the solution at the bottom of the crystallization kettle 2, the staff can open the sampling valve, and the solution in the bottom area of ​​the crystallization kettle 2 enters into the bent tube through the through holes on the ring tube, and then the solution is discharged through the bent tube and the sampling valve, so that the staff can analyze the crystallization situation inside the crystallization kettle 2 at this time.

[0043] When the embodiment of the present application is used, first, bismuth nitrate, purified water (or deionized water) and an appropriate amount of nitric acid are added to a dissolving kettle in a certain proportion, the mass fraction of nitric acid is generally between 50% and 70%, and the mass ratio of bismuth nitrate, nitric acid and water is adjusted according to the specific process requirements. Under the action of external heating equipment and stirring equipment, these raw materials are dissolved to form a saturated bismuth nitrate solution. The heating temperature is generally controlled between 60 and 80° C. (between 60 and 65° C. in this example) to ensure that the raw materials are fully dissolved and form a uniform solution. The saturated bismuth nitrate solution is filtered to remove insoluble matter therein to obtain a clarified bismuth nitrate solution. The clarified bismuth nitrate solution is transferred to an evaporating kettle and evaporated at normal pressure. and a certain temperature (such as 85 to 125°C) to increase the specific gravity of the solution in preparation for the subsequent crystallization process. The concentrated saturated bismuth nitrate solution enters the crystallization kettle 2 through the feeding structure 101. At this time, the staff connects the constant temperature circulator 6 with the external first water pump and the external heating system to maintain the temperature of the constant temperature circulator 6 and the crystallization kettle 2 between sixty and sixty-five degrees Celsius to ensure that the saturated bismuth nitrate solution is within a suitable crystallization temperature range. At the same time, the double-layer cage cooling crystallization component 5 starts to work, and the second water pump connects the external circulating cooling system to the double-layer cage cooling crystallization component 5, thereby introducing circulating cooling water into each tube body inside the double-layer cage cooling crystallization component 5. Under the action of the double-layer cage cooling crystallization component 5, the temperature of each crystallizer tube body gradually decreases, causing the bismuth nitrate in the solution to begin to crystallize. In order to accelerate the crystallization process and prevent the crystals from sinking to the bottom and hardening, the staff turns on the rotation drive unit 8 through the PLC control panel 11 to drive the double-ring agitator 7 to stir the solution. The function of the double-ring agitator 7 is to evenly distribute the solution on the tube wall of the double-layer cage cooling crystallization component 5, increase the contact area between the solution and the tube wall, thereby promoting the growth of the crystal. At the same time, stirring can also prevent the crystals from depositing and hardening on the bottom or tube wall of the crystallization kettle 2, and maintain the continuity and stability of the crystallization process. After the double-layer cage cooling crystallization component 5 is passed through the circulating cooling water for a certain period of time, the double-layer cage cooling crystallization component 5 is used. The negative pressure generated by the second water pump and the external circulating cooling system causes each crystallizer tube to deflate. This deformation causes the crystals attached to the crystallizer tube to be squeezed and fall off naturally, sinking to the bottom of the crystallization kettle 2. In this process, the growth cycle and particle size of the crystals can be accurately controlled by adjusting the time of introducing circulating cooling water. After the crystallization is completed, the staff opens the discharge pipe at the bottom of the crystallization kettle 2 and introduces the crystal slurry into the subsequent centrifugal filtration system. Under the action of centrifugal force, the bismuth nitrate crystals are efficiently separated from the solution. The separated crystals enter the drying system for drying treatment to remove moisture and residual solvent therein. The dried crystals are packaged to obtain the final bismuth nitrate pentahydrate product.

[0044] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0045] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A cooling crystallization device for bismuth nitrate pentahydrate, characterized in that: include: An L-shaped frame (1), a crystallization kettle (2) is fixed on the outer wall of one side of the L-shaped frame (1), a kettle cover (3) is bolted to the top of the crystallization kettle (2), and a feeding structure (101) for introducing a saturated bismuth nitrate solution is installed on the outer wall of the crystallization kettle (2) away from the L-shaped frame (1); A constant temperature circulator (6), the constant temperature circulator (6) being mounted on the outer peripheral surface of the crystallization kettle (2), a support plate (4) being fixed at one end inside the crystallization kettle (2), and a double-layer cage-type cooling crystallization component (5) for forming bismuth nitrate pentahydrate crystals being mounted at the bottom end of the support plate (4), a double-ring agitator (7) for stirring a saturated bismuth nitrate solution and preventing bismuth nitrate pentahydrate crystals from crystallizing on the inner wall of the crystallization kettle (2) being mounted at the center position of the bottom end of the support plate (4), and a rotary drive unit (8) for driving the double-ring agitator (7) to work being mounted at the center position of the top end of the kettle cover (3); A discharge pipe (9) is installed at the center of the bottom end of the crystallization kettle (2); a PLC control panel (11) is installed on the outer wall of one side of the L-shaped frame (1); the output end of the PLC control panel (11) is electrically connected to the rotation drive unit (8), the feed structure (101), and the input end of the constant temperature circulator (6).

2. A bismuth nitrate pentahydrate cooling crystallization device according to claim 1, characterized in that: The feed structure (101) comprises a feed transverse pipe (102) installed on the outer wall of one side of the crystallization kettle (2), a corrugated steel pipe (103) threadedly installed on the top of the feed transverse pipe (102), and a feed solenoid valve (104) installed on the top of the corrugated steel pipe (103), and a discharge valve is installed at the bottom end of the discharge pipe (9).

3. A bismuth nitrate pentahydrate cooling crystallization device according to claim 1, characterized in that: The constant temperature circulator (6) comprises a liquid storage jacket (601) installed on the outer peripheral surface of the crystallization kettle (2), a liquid discharge pipe head (604) installed on the outer wall of one side of the liquid storage jacket (601), and a liquid injection pipe head (603) installed on the outer wall of the other side of the liquid storage jacket (601), and a cavity (602) for retaining cooling liquid is provided between the inner wall of the liquid storage jacket (601) and the outer wall of the crystallization kettle (2).

4. A bismuth nitrate pentahydrate cooling crystallization device according to claim 1, characterized in that: The double-layer cage-type cooling crystallization assembly (5) comprises a plurality of external crystallization tube bodies (501) connected in series and fixed at the bottom end of the support plate (4) and a plurality of internal crystallization tube bodies (502) connected in series. The external crystallization tube bodies (501) and the internal crystallization tube bodies (502) have the same structure. A short U-shaped conducting tube (509) is installed between the liquid discharge port of one of the internal crystallization tube bodies (502) and the liquid inlet port of one of the external crystallization tube bodies (501). A U-shaped conducting tube 2 (504) is installed between the head and tail ends of the plurality of internal crystallization tube bodies (502). A U-shaped conducting tube 1 (503) is installed between the head and tail ends of the plurality of external crystallization tube bodies (501). The double-ring agitator (7) is located in the area between the plurality of internal crystallization tube bodies (502).

5. A bismuth nitrate pentahydrate cooling crystallization device according to claim 4, characterized in that: A liquid inlet (505) is installed at the liquid inlet of one of the crystallization kettles (2), the top end of the liquid inlet pipe (505) penetrates to the outside of the kettle cover (3), and a liquid inlet solenoid valve (506) is installed at the top end of the liquid inlet pipe (505); a liquid outlet (507) is installed at the liquid outlet of one of the external crystallization tube bodies (501), one end of the liquid outlet pipe (507) penetrates to the outside of the kettle cover (3) and is installed with a liquid outlet solenoid valve (508).

6. A bismuth nitrate pentahydrate cooling crystallization device according to claim 5, characterized in that: The outer crystal tube body (501) is composed of a tube seat (5011), a hose (5012) and a diaphragm (5013); the tube seat (5011) is fixed to the bottom end of the support plate (4); the hose (5012) is fixed to the bottom end of the tube seat (5011); the diaphragm (5013) is installed inside the hose (5012) and divides the hose (5012) into two chambers that are interconnected; the hose (5012) is made of polytetrafluoroethylene material; and a water inlet (5015) and a water outlet (5014) that are interconnected with the chambers are respectively installed on both sides of the top of the tube seat (5011).

7. A bismuth nitrate pentahydrate cooling crystallization device according to claim 6, characterized in that: The double-ring agitator (7) comprises a vertical shaft (701) rotatably mounted at the center position inside the support plate (4), a T-arm (702) integrally formed at the bottom end of the vertical shaft (701), and a support ring (703) fixed on the upper surface of the T-arm (702), a plurality of scrapers (704) are evenly spacedly mounted on the top of the support ring (703), one side of the scrapers (704) is in contact with the inner wall of the crystallization kettle (2), and stirring blades (705) are mounted on both ends of the surface of the vertical shaft (701).

8. A bismuth nitrate pentahydrate cooling crystallization device according to claim 7, characterized in that: The rotary drive unit (8) comprises a conical motor seat (801) fixed to the top of the kettle cover (3), a shaft tube (803) installed at the center position inside the conical motor seat (801), and a reduction motor (802) installed at the top of the conical motor seat (801), wherein the output end of the reduction motor (802) is fixedly connected to the top of the vertical shaft (701) via a coupling, and ball bearings are installed at both ends of the shaft tube (803).

9. A bismuth nitrate pentahydrate cooling crystallization device according to claim 2, characterized in that: A sampling structure (10) is arranged inside the discharge pipe (9).

10. A bismuth nitrate pentahydrate cooling crystallization device according to claim 9, characterized in that: The sampling structure (10) comprises a bent tube installed inside the discharge tube (9), a ring tube installed at the top of the bent tube, and a sampling valve installed at the bottom of the bent tube, and a plurality of through holes are provided on the upper surface of the ring tube.

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