Continuous crystallizer for microwave heating assisted crystallization of water-soluble fertilizer

Abstract

The invention discloses a continuous crystallizer for microwave heating assisted crystallization of a water-soluble fertilizer. The continuous crystallizer comprises a steam chamber, a separation chamber, a crystallization chamber and a microwave heater. The microwave heater is adopted to replace an independent traditional heater, the characteristics of uniform microwave heating and high microwave heating speed are fully utilized, mother liquor is uniformly and rapidly heated, and the problem that crystals on a heat exchange wall are easy to deposit due to temperature gradient when a traditional DTB crystallizer works is solved; meanwhile, the problem that few crystals are generated on the inner wall of a traditional heater and then slowly deposit and even corrode the inner wall of the heater is solved. The heat insulation plate is arranged to prevent heat from being quickly diffused and conducted to the steam chamber from the separation chamber, the heat is kept to continuously heat mother liquor in the separation chamber, the evaporation process is accelerated, the supersaturation degree generation speed is increased, and the space between the inner wall and the outer wall of the continuous crystallizer is in a vacuum state so as to prevent the heat in the crystallizer from being diffused and lost to the outside. The crystallization speed is accelerated; and the production efficiency is improved.

Description

Technical Field

[0001] The invention relates to the technical field of crystallizers, in particular to a continuous crystallizer for crystallizing water-soluble fertilizer by microwave heating. Background Art

[0002] Crystallization is an important unit operation in the chemical production process. The crystallization process is not only used in the production process of products, but also widely used in the separation and purification process of products. According to the differences in process routes and functional structures, crystallizers are divided into many types, such as DTB type, OSLO type, forced circulation type, etc. Temperature and stirring speed have a significant impact on the crystallization process of industrial water-soluble fertilizers. There are crystal particles of different sizes and irregular morphologies, which directly affect the filtration performance and product purity, and affect the quality of the product.

[0003] For example, the Chinese invention with announcement number CN110237558B and announcement date September 17, 2024 discloses an integrated crystallization device and crystallization method with a continuous fine crystal elimination cycle, which solves the problems of complex structure, high equipment investment, narrow operating range, circulation flow field offset, and poor fine crystal elimination effect of the existing external circulation type fine crystal elimination crystallization system. The invention realizes the integrated design of the fine crystal elimination circulation system and the crystallizer by setting a fine crystal elimination circulation heat exchange device inside the traditional DTB or Oslo type crystallizer. The circulation flow of the crystallization mother liquor is improved by optimizing the internal structure of the crystallizer, so that the crystals are suspended in the liquid flow to form a fluidized bed with particle size classification. Crystals with larger particle sizes are enriched and continue to grow in the crystal growth zone at the bottom of the crystallizer, and crystals with smaller particle sizes are heated and dissolved with the rising liquid flow through the fine crystal elimination circulation zone, thereby realizing the effective removal of fine grains. The integrated crystallization device disclosed in this application has the advantages of compact and reliable equipment structure, good fine crystal elimination effect, and controllable product particle size distribution.

[0004] When the traditional DTB crystallizer is working, due to the existence of temperature gradient, crystals are preferentially precipitated near the heat exchange wall surface, and the material concentration at the heat exchange wall crystal deposition wall surface and the main material concentration gradient also increase accordingly, and the heat exchange wall crystals are easy to deposit; in addition, an independent heater needs to be set to heat the steam and the reflux mother liquor to facilitate crystallization in the crystallizer. The reflux mother liquor is heated in the heater to produce supersaturation, which will produce a small amount of crystals on the inner wall of the heater and then slowly deposit or even corrode the inner wall of the heater, affecting the normal operation and service life of the heater. For this reason, the present invention proposes a continuous crystallizer for microwave heating assisted crystallization of water-soluble fertilizer to solve the above problems. Summary of the invention

[0005] The purpose of the present invention is to solve the deficiencies of the prior art and to provide a continuous crystallizer for crystallizing water-soluble fertilizer by microwave heating.

[0006] In order to achieve the above object, the present invention provides the following technical solutions: A continuous crystallizer for microwave-heated assisted crystallization of water-soluble fertilizer comprises a steam chamber, a separation chamber and a crystallization chamber which are sequentially arranged from top to bottom, wherein the steam chamber, the separation chamber and the crystallization chamber are hollow inverted funnel-shaped, circular and funnel-shaped cylinders respectively, and the inner and outer walls of the steam chamber, the separation chamber and the crystallization chamber are in a vacuum state to prevent the heat in the crystallizer from diffusing and losing to the outside; a plurality of microwave heaters are symmetrically arranged on the outer wall of the crystallization chamber with the central axis of the crystallizer as the center, and the microwave heaters comprise a microwave tube, a microwave tube power supply and a microwave protective cover, a microwave emitting end of the microwave tube sequentially passes through the outer wall and the inner wall of the crystallization chamber and faces the separation chamber, the microwave tube and the microwave tube power supply are electrically connected, and the microwave protective cover surrounds and covers the microwave tube and the microwave tube power supply to prevent microwave leakage.

[0007] Preferably, a heat insulation board is arranged between the steam chamber and the separation chamber, the edge of the heat insulation board is tightly fitted to the inner wall of the separation chamber, and the heat insulation board is composed of a bottom layer of heat insulation material and an upper layer of reflective film to prevent heat from being conducted from the separation chamber to the steam chamber; a plurality of air holes are arranged on the circumference of the heat insulation board near the edge, and the air holes are symmetrically and evenly distributed with equal adjacent angles and equal spacing around the center of the heat insulation board; a steam outlet passing through the outer wall of the steam chamber is arranged on the inner wall of the steam chamber.

[0008] Preferably, a motor is arranged upward from the top of the steam chamber, and the output end of the motor is connected to a stirring shaft through a coupling, which passes through the steam chamber, the insulation plate and the top of the separation chamber in sequence and is inserted into the bottom of the separation chamber; a plurality of propellers are arranged on the stirring shaft in sequence from bottom to top, and the radial inner end of the propeller is integrally formed into a circular sleeve containing a protrusion, which is engaged with the groove on the stirring shaft.

[0009] Preferably, a fixed plate is provided in the middle and upper part of the inner wall of the separation chamber, and a guide tube is fixedly connected to the fixed plate, the guide tube is arranged with the stirring shaft as the center, the propeller is sleeved in the guide tube and the inner diameter of the guide tube is 10-100 mm larger than the outer diameter of the propeller; a baffle is provided in the middle part of the inner wall of the separation chamber, and the baffle extends from top to bottom at an inclination of 20-40° to the vertical direction, and then extends vertically downward to the bottom of the separation chamber; a clear liquid outlet is provided on the inner wall of the separation chamber below the baffle, which passes through the inner wall and outer wall of the separation chamber in sequence.

[0010] Preferably, a steam inlet and a mother liquor inlet are respectively arranged on both sides of the inner wall of the crystallization chamber below the microwave heater, the steam inlet is connected to the steam outlet through a pipeline to form a steam circulation system, and the mother liquor inlet is connected to the clear liquid outlet through a pipeline to form a reflux mother liquor circulation system.

[0011] Preferably, an elutriation column is arranged at the bottom center of the crystallization chamber, and a crystal liquid outlet with a valve is arranged on the bottom side wall of the elutriation column. The crystal liquid outlet is connected to a centrifuge through a pipeline. The centrifuge is respectively provided with a crystal outlet and a filtrate outlet, and the filtrate outlet is connected to the mother liquor inlet through a pipeline to form a filtrate circulation system.

[0012] Preferably, a temperature measuring device passing through the inner and outer walls of the separation chamber is provided on the bottom edge of the inner wall of the separation chamber, and a control unit is provided on the middle outer wall of the separation chamber. The control unit is electrically connected to and controls the temperature measuring device, motor and microwave tube power supply.

[0013] The beneficial effects of the present invention are: 1. A microwave heater is used instead of a single traditional heater, making full use of the characteristics of microwave uniform heating and fast speed to uniformly and quickly heat the mother liquor, solving the problem of easy deposition of crystals on the heat exchange wall due to temperature gradient in the operation of the traditional DTB crystallizer; at the same time, it solves the problem of a small amount of crystals on the inner wall of the traditional heater, which then slowly deposits and even corrodes the inner wall of the heater.

[0014] 2. Heat insulation plates are installed to prevent heat from rapidly diffusing and conducting from the separation chamber to the steam chamber, retaining heat in the separation chamber to continuously heat the mother liquor, accelerating the evaporation process and the rate of producing supersaturation. The inner and outer walls of the continuous crystallizer are in a vacuum state to avoid heat in the crystallizer from diffusing and losing to the outside world, thereby improving the utilization rate of thermal energy, accelerating the crystallization rate, and improving production efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the implementation methods of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for the implementation methods or the description of the prior art. Obviously, the drawings in the following description are only exemplary, and for ordinary technicians in this field, other implementation drawings can be derived from the provided drawings without creative work.

[0016] The structures, proportions, sizes, etc. illustrated in this specification are only used to match the contents disclosed in the specification so as to facilitate understanding and reading by persons familiar with the technology. They are not used to limit the conditions under which the present invention can be implemented, and therefore have no substantial technical significance. Any structural modification, change in proportion or adjustment of size shall still fall within the scope of the technical contents disclosed in the present invention without affecting the effects and purposes that can be achieved by the present invention.

[0017] Figure 1 It is a structural schematic diagram of the continuous crystallizer of the present invention; Figure 2It is a structural schematic diagram of the microwave heater of the present invention; As shown in the figure: 1. steam chamber; 2. separation chamber; 3. crystallization chamber; 4. microwave heater; 41. microwave tube; 42. microwave tube power supply; 43. microwave protective cover; 5. heat insulation board; 6. air hole; 7. steam outlet; 8. motor; 9. stirring shaft; 10. propeller; 11. fixed plate; 12. guide tube; 13. baffle; 14. clear liquid outlet; 15. steam inlet; 16. mother liquor inlet; 17. elutriation column; 18. crystal liquid outlet; 19. centrifuge; 20. crystal outlet; 21. filtrate outlet; 22. temperature measuring device; 23. control unit. DETAILED DESCRIPTION

[0018] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0019] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected 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.

[0020] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features of the embodiments may be combined with each other.

[0021] It should be noted that similar reference numerals and letters tend to denote similar items in the following drawings, and therefore, once an item is defined in one drawing, it does not require further definition and explanation in subsequent drawings.

[0022] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "front", "back", "vertical", "horizontal", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, or the positions or positional relationships in which the product of the invention is usually placed when in use, or the positions or positional relationships commonly understood by those skilled in the art, which are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second" and the like are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0023] In the description of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0024] Reference Figure 1-2 The present invention discloses a continuous crystallizer for microwave heating-assisted crystallization of water-soluble fertilizer, comprising a steam chamber 1, a separation chamber 2 and a crystallization chamber 3 arranged in sequence from top to bottom, wherein the inner walls and outer walls of the steam chamber 1, the separation chamber 2 and the crystallization chamber 3 are in a vacuum state to prevent the heat in the crystallizer from diffusing to the outside and being lost; a plurality of microwave heaters 4 are arranged on the outer wall of the crystallization chamber 3, and the mother liquor in the separation chamber 2 and the crystallization chamber 3 is uniformly and quickly heated by utilizing the characteristics of uniform and fast microwave heating; the microwave heater 4 comprises a microwave tube 41, a microwave tube power supply 42 and a microwave protective cover 43, and the microwave emitting end of the microwave tube 41 penetrates the inner and outer walls of the crystallization chamber 3 and faces the separation chamber 2, so as to generate microwaves; after the microwave tube 41 and the microwave tube power supply 42 are electrically connected, they are wrapped and protected by the microwave protective cover 43 to prevent microwave leakage.

[0025] An insulation board 5 is arranged between the steam chamber 1 and the separation chamber 2. The insulation board 5 fits tightly against the inner wall of the separation chamber 2 to form a closed space to prevent the heat from quickly diffusing and conducting from the separation chamber 2 to the steam chamber 1. The insulation board 5 is composed of a bottom insulation material and an upper reflective film. The insulation material is used to isolate the conduction of heat, and the reflective film is used to reflect the heat back into the separation chamber 2. A plurality of pores 6 are arranged near the edge of the circumference of the insulation board 5. The pores 6 are symmetrically and evenly distributed with equal adjacent angles and equal spacing around the center of the insulation board 5, so that the enclosed steam can be discharged from the pores 6 after sufficient heat exchange in the separation chamber 2. A steam outlet 7 is arranged on the inner wall of the steam chamber 1 and passes through the outer wall of the steam chamber 1 to discharge the steam from the steam chamber 1.

[0026] A motor 8 is arranged upward from the top of the steam chamber 1, and the output end of the motor 8 is connected to a stirring shaft 9 inserted into the bottom of the separation chamber 2 through a coupling, and the motor 8 is used to provide driving force for the stirring shaft 9; a plurality of propellers 10 are arranged on the stirring shaft 9 in sequence from bottom to top, and the propellers 10 are used to stir and transport the mother liquid upward; a guide tube 12 is sleeved on the outer side of the propeller 10, and the inner diameter of the guide tube 12 is 10-100 larger than the outer diameter of the propeller 10 mm, the guide tube 12 is used to help the mother liquor complete the internal directional circulation flow; the top of the guide tube 12 is connected to the fixed plate 11 set in the middle and upper part of the inner wall of the separation chamber 2, and the fixed plate 11 is used to install and fix the guide tube 12; a baffle 13 is set in the middle of the inner wall of the separation chamber 2, and the baffle 13 extends from top to bottom at an angle of 20-40° to the vertical direction, and then extends vertically downward to the bottom of the separation chamber 2. The baffle 13 plays a role in shielding crystals; a clear liquid outlet 14 is set on the inner wall of the separation chamber 2 below the baffle 13, and clarified mother liquor can flow out from the clear liquid outlet 14 according to process requirements.

[0027] On both sides of the inner wall of the crystallization chamber 3, below the microwave heater 4, a steam inlet 15 and a mother liquid inlet 16 are respectively arranged. The steam inlet 15 is connected to the steam outlet 7 through a pipeline to form a steam circulation system, and the mother liquid inlet 16 is connected to the clear liquid outlet 14 through a pipeline to form a reflux mother liquid circulation system. An elutriation column 17 is arranged at the bottom center of the crystallization chamber 3. The supersaturated mother liquid produces fine crystals and sinks to the elutriation column 17. A crystal liquid outlet 18 with a valve is arranged on the bottom side wall of the elutriation column 17. The crystal liquid containing fine crystals flows out from the crystal liquid outlet 18 through a pipeline to a centrifuge 19. The centrifuge 19 is respectively provided with a crystal outlet 20 and a filtrate outlet 21. After centrifugal separation, the crystals are discharged from the crystal outlet 20, and the filtrate flows out from the filtrate outlet 21 and is connected to the mother liquid inlet 16 through a pipeline to form a filtrate circulation system.

[0028] A temperature measuring device 22 is provided on the bottom edge of the inner wall of the separation chamber 2, and the temperature measuring device 22 passes through the outer wall of the separation chamber 2. A control unit 23 provided on the outer wall of the middle part of the separation chamber 2 is electrically connected to and controls the temperature measuring device 22, the motor 8 and the microwave tube power supply 42. Since the crystallization temperature of a general water-soluble fertilizer is about 50-70°C, the temperature target can be set at 60°C on the control unit 23, and the temperature of the crystallization chamber 3 and the separation chamber 2 is monitored by the temperature measuring device 22 in real time to be about 60°C.

[0029] Example 1 The continuous crystallizer is turned on and the control unit 23 turns on the motor 8, the temperature measuring device 22 and the microwave tube power supply 42 respectively, and the temperature target of the temperature measuring device 22 is set to 60°C. The mother liquor containing water-soluble fertilizer is added from the mother liquor inlet 16 to the middle of the crystallization chamber 3 and then reaches the bottom of the separation chamber 2. Since the motor 8 drives the stirring shaft 9 to rotate and then drives the propeller 10 to rotate, the generated vortex stirs and transports the mother liquor upward to the middle of the separation chamber 2, and transports it upward in the guide tube 12; during this process, the microwave heater 4 starts to work, and the microwave tube 41 generates microwaves to uniformly and quickly heat the mother liquor, and controls the temperature of the mother liquor at about 60°C. When the temperature exceeds 60°C, the control unit 23 turns off the microwave tube power supply 42 to keep the temperature at about 60°C; after the mother liquor is transported to the top of the guide tube 12, it flows downward from the side wall of the guide tube 12. Due to the presence of the baffle 13, the mother liquor flows directly downward to the bottom of the separation chamber 2, and then due to the vortex effect of the propeller 10, the above process is repeated to form an internal cycle; the steam generated by the heated mother liquor and After the heat reaches the insulation board 5, it is blocked and reflected back, and continues to heat the surface of the mother liquor; the reflected steam heats the surface of the mother liquor and then rises, flows into the evaporation chamber 1 from the pores 6 of the insulation board 5, flows out from the steam outlet 7 through the pipeline to the steam inlet 15, and continues to enter the crystallization chamber 3, the separation chamber 2 and the steam chamber 1 in sequence to form a steam cycle; the clarified mother liquor flows out from the clear liquid outlet 14 through the pipeline to the mother liquor inlet 16, and continues to enter the crystallization chamber 3 and the separation chamber 2 in sequence to form a reflux mother liquor cycle, and the supersaturated mother liquor slowly precipitates fine water-soluble fertilizer crystals at the elutriation column 17, and is discharged from the crystal liquid outlet 18 to the centrifuge 19 for centrifugal separation, and the water-soluble fertilizer crystals are discharged from the crystal outlet 20, and the filtrate flowing out from the filtrate outlet 21 flows to the mother liquor inlet 16 through the pipeline to continue to repeat the heating, crystallization and centrifugal separation process to form a filtrate cycle.

[0030] Of course, the embodiments of this specific implementation method are all preferred embodiments of the present invention, and are not intended to limit the protection scope of the present invention. Therefore, all equivalent changes made based on the structure, shape, and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A continuous crystallizer for microwave heating assisted crystallization of water-soluble fertilizer, comprising a steam chamber (1), a separation chamber (2) and a crystallization chamber (3) arranged in sequence from top to bottom, wherein the steam chamber (1), the separation chamber (2) and the crystallization chamber (3) are hollow inverted funnel-shaped, circular, or funnel-shaped cylinders, respectively, and characterized in that: The inner and outer walls of the steam chamber (1), the separation chamber (2) and the crystallization chamber (3) are in a vacuum state to prevent the heat in the crystallizer from diffusing and being lost to the outside. A plurality of microwave heaters (4) are symmetrically arranged on the outer wall of the crystallization chamber (3) with the central axis of the crystallizer as the center. The microwave heater (4) comprises a microwave tube (41), a microwave tube power supply (42) and a microwave protective cover (43). The microwave emitting end of the microwave tube (41) sequentially passes through the outer and inner walls of the crystallization chamber (3) and faces the separation chamber (2). The microwave tube (41) and the microwave tube power supply (42) are electrically connected. The microwave protective cover (43) surrounds and covers the microwave tube (41) and the microwave tube power supply (42) to prevent microwave leakage.

2. A continuous crystallizer for microwave heating assisted crystallization of water-soluble fertilizer according to claim 1, characterized in that: A heat insulation board (5) is arranged between the steam chamber (1) and the separation chamber (2), the edge of the heat insulation board (5) is tightly fitted to the inner wall of the separation chamber (2), and the heat insulation board (5) is composed of a bottom layer of heat insulation material and an upper layer of reflective film to prevent heat from being conducted from the separation chamber (2) to the steam chamber (1); a plurality of air holes (6) are arranged near the edge of the circumference of the heat insulation board (5), and the air holes (6) are symmetrically and evenly distributed with equal adjacent angles and equal spacing around the center of the heat insulation board (5); a steam outlet (7) is arranged on the inner wall of the steam chamber (1) and passes through the outer wall of the steam chamber (1).

3. A continuous crystallizer for microwave-assisted crystallization of water-soluble fertilizer according to claim 1, characterized in that: A motor (8) is arranged upward from the top of the steam chamber (1), and the output end of the motor (8) is connected to a stirring shaft (9) through a coupling, which sequentially passes through the steam chamber (1), the heat insulation plate (5) and the top of the separation chamber (2) and is inserted into the bottom of the separation chamber (2); a plurality of propellers (10) are arranged sequentially from bottom to top on the stirring shaft (9), and the radial inner end of the propeller (10) is integrally formed into a circular sleeve containing a protrusion, which is engaged with a groove on the stirring shaft (9).

4. The continuous crystallizer for microwave-assisted crystallization of water-soluble fertilizer according to claim 1, characterized in that: A fixed plate (11) is arranged at the middle and upper part of the inner wall of the separation chamber (2), and a guide tube (12) is fixedly connected to the fixed plate (11), and the guide tube (12) is arranged with the stirring shaft (9) as the center, and the propeller (10) is sleeved in the guide tube (12), and the inner diameter of the guide tube (12) is 10-100 mm larger than the outer diameter of the propeller (10); a baffle (13) is arranged at the middle part of the inner wall of the separation chamber (2), and the baffle (13) extends from top to bottom at an angle of 20-40 degrees to the vertical direction, and then extends vertically downward to the bottom of the separation chamber (2); a clear liquid outlet (14) is arranged on the inner wall of the separation chamber (2) below the baffle (13), and passes through the inner wall and outer wall of the separation chamber (2) in sequence.

5. A continuous crystallizer for microwave heating assisted crystallization of water-soluble fertilizer according to claim 1, characterized in that: A steam inlet (15) and a mother liquor inlet (16) are respectively arranged on both sides of the inner wall of the crystallization chamber (3) below the microwave heater (4); the steam inlet (15) is connected to the steam outlet (7) through a pipeline to form a steam circulation system; and the mother liquor inlet (16) is connected to the clear liquid outlet (14) through a pipeline to form a reflux mother liquor circulation system.

6. A continuous crystallizer for microwave heating assisted crystallization of water-soluble fertilizer according to claim 1, characterized in that: An elutriation column (17) is arranged at the bottom center of the crystallization chamber (3), and a crystal liquid outlet (18) with a valve is arranged on the bottom side wall of the elutriation column (17). The crystal liquid outlet (18) is connected to a centrifuge (19) through a pipeline. The centrifuge (19) is respectively provided with a crystal outlet (20) and a filtrate outlet (21). The filtrate outlet (21) is connected to the mother liquor inlet (16) through a pipeline to form a filtrate circulation system.

7. A continuous crystallizer for microwave heating assisted crystallization of water-soluble fertilizer according to claim 1, characterized in that: A temperature measuring device (22) is arranged on the bottom edge of the inner wall of the separation chamber (2) and passes through the inner wall and the outer wall of the separation chamber (2). A control unit (23) is arranged on the outer wall in the middle of the separation chamber (2). The control unit (23) is electrically connected to and controls the temperature measuring device (22), the motor (8) and the microwave tube power supply (42).

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