Phosphate continuous crystallization system and phosphate production method

Abstract

The application relates to the technical field of chemical equipment, and provides a phosphate continuous crystallization system and a phosphate manufacturing method.The phosphate continuous crystallization system comprises an ammonium phosphate production system, an integrated continuous crystallizer, a crystallization circulating pump, a crystallization heater, a crystallization vacuum condensation system, a crystallization material pump, a thickener and a centrifugal machine; a raw material input end of the integrated continuous crystallizer is used for being connected with second-concentration raw materials of phosphoric acid and ammonia gas or being connected with a phosphoric acid ammonium slurry output end of the ammonium phosphate production system; a circulating material output end of the integrated continuous crystallizer is sequentially connected with a circulating material input end through the crystallization circulating pump and the crystallization heater; a crystallization material output end is sequentially connected with an input end of the centrifugal machine through the crystallization material pump and the thickener; and the centrifugal machine outputs phosphate to be dried. Process equipment such as reaction, concentration, crystallization and tail gas washing is no longer needed, the required equipment quantity and floor area are greatly reduced, and thus the initial investment cost and long-term operation cost are reduced.

Description

Technical Field

[0001] This invention relates to the field of chemical equipment technology, specifically to a continuous crystallization system for phosphates and a method for manufacturing phosphates. Background Technology

[0002] Existing phosphate chemical enterprises typically produce industrial-grade / food-grade monoammonium phosphate by reacting concentrated phosphoric acid (such as 75% or 85% H3PO4 industrial-grade / food-grade phosphoric acid) with ammonia and then crystallizing it intermittently. This method results in unstable product quality and requires processes such as neutralization reaction, crystallization, and tail gas scrubbing. It also requires major process equipment such as neutralization reactors, crystallizers, and tail gas scrubbers, leading to high investment costs, high operating costs, and large land area requirements.

[0003] However, if a medium-concentration raw material, phosphoric acid (40-58% H3PO4), is used, the process requires neutralization reaction, double-effect concentration, crystallization, and tail gas scrubbing, as well as numerous process equipment and supporting systems such as neutralization reactors, first-effect concentration systems, second-effect concentration systems, crystallizers, and tail gas scrubbers. This also results in high investment costs, high operating costs, and a large footprint.

[0004] Therefore, there is a need for a phosphate production system that can produce highly stable products with low investment costs and a small footprint. Summary of the Invention

[0005] In view of this, the embodiments of this application provide a phosphate continuous crystallization system and a phosphate manufacturing method, which provides stable product quality and eliminates the need for reaction, concentration, crystallization, and tail gas washing process equipment, thus significantly reducing the number of required equipment and floor space, thereby reducing initial investment costs and long-term operating expenses.

[0006] The first aspect of this application provides a continuous phosphate crystallization system, including a monoammonium phosphate generating system, an integrated continuous crystallizer, a crystallization circulation pump, a crystallization heater, a crystallization vacuum condensation system, a crystallization material pump, a thickener, and a centrifuge;

[0007] The monoammonium phosphate generation system is used to obtain monoammonium phosphate slurry based on a first concentration of raw phosphoric acid.

[0008] The integrated continuous crystallizer includes an upper washing section for washing the crystallization tail gas and a lower reaction crystallization section. The top of the washing section is connected to the crystallization vacuum condensation system. The raw material input end of the integrated continuous crystallizer is connected to the second concentration raw materials phosphoric acid and ammonia, or to the monoammonium phosphate slurry output end of the monoammonium phosphate generation system. The circulating material output end of the integrated continuous crystallizer is connected to the circulating material input end of the integrated continuous crystallizer in sequence through a crystallization circulating pump and a crystallization heater. The crystallization material output end of the integrated continuous crystallizer is connected to the input end of the centrifuge in sequence through the crystallization material pump and the thickener. The centrifuge outputs phosphate to be dried, which is used to obtain phosphate after drying.

[0009] The concentration of the first concentration raw material phosphoric acid is lower than that of the second concentration raw material phosphoric acid.

[0010] This application embodiment achieves fully automated control of the entire process from raw materials to finished products by integrating a monoammonium phosphate (MAP) generation system, an integrated continuous crystallizer, and related circulation and processing equipment. This not only improves production efficiency and product quality consistency but also eliminates the need for separate reaction, concentration, crystallization, and tail gas scrubbing equipment by simultaneously completing multiple steps in the integrated continuous crystallizer. This significantly reduces the required equipment quantity and floor space, thereby lowering initial investment costs and long-term operating expenses. The integrated continuous crystallizer's input can be connected to the output of the MAP generation system or directly to phosphoric acid and ammonia of a second concentration. Different production processes can be adopted for different concentrations of phosphoric acid, offering greater flexibility and applicability. Furthermore, by reheating the circulating material in the crystallization heater, the crystallizer combines the functions of a concentration system with crystallization. Simultaneously, small crystal particles can be extracted and re-dissolved from the crystallizer, resulting in a larger particle size distribution and more concentrated particle size distribution in the product. The system utilizes phosphoric acid and ammonia as raw materials, is environmentally friendly, has high energy utilization, low production and operating costs, and good energy-saving effects.

[0011] In one embodiment, the monoammonium phosphate generating system includes a pre-neutralization reactor, a mist separator, a pre-neutralization circulation pump, a pre-neutralization heater, an ammoniation reactor, and a feed pump;

[0012] The steam outlet of the pre-neutralization reactor is connected to the input of the mist separator. The gas phase output of the mist separator is connected to the crystallization heater. The liquid phase output of the mist separator is connected to the material output of the pre-neutralization reactor. The material output of the pre-neutralization reactor is connected to the input of the pre-neutralization circulation pump and the feed pump, respectively. The output of the feed pump is the output of the monoammonium phosphate slurry of the monoammonium phosphate generation system. The output of the pre-neutralization circulation pump is connected to the input of the pre-neutralization heater. The input of the ammoniation reactor is connected to ammonia and the output of the pre-neutralization heater. The output of the ammoniation reactor is connected to the circulating material input of the pre-neutralization reactor. The material input of the pre-neutralization reactor is used to input the first concentration of raw material phosphoric acid.

[0013] In this embodiment, the flash vapor from the pre-neutralization reactor is separated into mist and water droplets by a mist separator, increasing the dry gas ratio of the flash vapor. This improves the heat exchange efficiency of the crystallizer heater and effectively prevents scaling of the flash vapor within the heater. Furthermore, using the flash vapor from the pre-neutralization reactor as a heat source for the crystallizer heater effectively utilizes its heat, improving the system's heat utilization rate while eliminating the need for a separate material concentration system, thus reducing investment and operating costs.

[0014] In one embodiment, the material ratio range from the material output terminal of the pre-neutralization reactor to the pre-neutralization circulation pump and the feed pump is 20:1 to 50:1.

[0015] This application embodiment ensures a gentle temperature rise (1-6 degrees Celsius) of the material in the pre-neutralization heater by rationally allocating the material flow to the pre-neutralization circulation pump and the feed pump (ratio of 20:1 to 50:1), effectively mitigating internal scaling and clogging problems, extending the equipment's operating cycle, and ensuring sufficient reaction between ammonia and phosphoric acid, thereby enhancing the quality of the monoammonium phosphate slurry.

[0016] In one embodiment, the second concentration of phosphoric acid is fed into the washing section of the integrated continuous crystallizer, and the ammonia is fed into the reaction crystallization section of the integrated continuous crystallizer.

[0017] In this embodiment, by inputting phosphoric acid of a second concentration into the washing section and ammonia into the reaction crystallization section, the washing effect of the tail wash is ensured, while the reaction time with ammonia is increased, thereby achieving a full reaction between ammonia and phosphoric acid.

[0018] In one embodiment, the system further includes a mother liquor collection tank and a crystallization washing circulation pump. The upper liquid output end of the thickener and the mother liquor output end of the centrifuge are connected to the mother liquor collection tank. The input end of the crystallization washing circulation pump is connected to the mother liquor collection tank, and the output end of the crystallization washing circulation pump is connected to the recycled material input end of the integrated continuous crystallizer.

[0019] This application embodiment constructs a closed-loop material circulation mechanism by introducing a mother liquor collection tank and a crystallization washing circulation pump. This allows the liquid in the thickener and the mother liquor generated by the centrifuge to be reintroduced into the integrated continuous crystallizer to participate in a new round of reaction. This not only helps reduce waste emissions and lower the risk of environmental pollution, but also promotes the effective reuse of resources, further saves production costs, and enhances the sustainability of production.

[0020] In one embodiment, the phosphoric acid concentration of the first concentration raw material is in the range of 40% to 58%, and the phosphoric acid concentration of the second concentration raw material is in the range of 75% to 85%.

[0021] In one embodiment, the system further includes a washing circulation pump. The washing section of the integrated continuous crystallizer is provided with a demister cleaning nozzle, a gas washing nozzle, and a gas distributor in sequence from top to bottom. The input end of the washing circulation pump is connected to the top of the gas distributor, and the output end of the washing circulation pump is connected to the demister cleaning nozzle.

[0022] The washing section located at the top of the integrated continuous crystallizer in this embodiment includes a demister cleaning nozzle, a gas washing nozzle, a gas distributor, and a corresponding washing circulation pump, achieving effective washing of the crystallization tail gas. This design reduces the need for additional tail gas washing equipment, improves ammonia recovery rate, ensures that tail gas emissions meet standards, reduces environmental impact, and demonstrates environmental benefits.

[0023] A second aspect of this application provides a method for manufacturing phosphate using a continuous phosphate crystallization system, comprising:

[0024] Phosphoric acid of a first concentration with a phosphoric acid concentration range of 40-58% is fed into the monoammonium phosphate generation system to obtain flash vapor and monoammonium phosphate slurry. The monoammonium phosphate slurry is then fed into an integrated continuous crystallizer to obtain crystalline material.

[0025] Alternatively, phosphoric acid with a phosphoric acid concentration ranging from 75% to 85% and ammonia gas are fed into an integrated continuous crystallizer to obtain crystalline material.

[0026] The crystalline material was sequentially concentrated, centrifuged, and dried to obtain phosphate.

[0027] This application provides a flexible selection scheme for raw phosphoric acid of different concentrations: lower concentration (40-58%) first-concentration raw phosphoric acid is first processed into monoammonium phosphate slurry via a monoammonium phosphate generation system; higher concentration (75%-85%) second-concentration raw phosphoric acid is directly added to the washing section of the integrated continuous crystallizer, while ammonia gas is fed into the reaction crystallization section. This adapts to the needs of raw materials of different qualities, ensures that the system can operate under optimal conditions, maximizes the utilization of reaction heat energy, ensures product stability and high yield, while simplifying the process flow and reducing energy consumption.

[0028] In one embodiment, it also includes:

[0029] Phosphoric acid of a first concentration with a phosphoric acid concentration range of 40-58% is fed into the pre-neutralization reactor, and the materials of the monoammonium phosphate generation system are fed into the pre-neutralization heater and the feed pump at a ratio of 20:1 to 50:1 respectively.

[0030] The pre-neutralization heater is used to generate monoammonium phosphate slurry and input it into the circulating material input end of the pre-neutralization reactor, and the feed pump is used to output monoammonium phosphate slurry.

[0031] In one embodiment, it also includes:

[0032] The flash vapor is fed into the crystallization heater, and the integrated continuous crystallizer outputs the material to the crystallization heater, and then returns it to the integrated continuous crystallizer after being heated by the flash vapor in the crystallization heater.

[0033] The phosphate continuous crystallization system provided in the first aspect of this application integrates a monoammonium phosphate generation system, an integrated continuous crystallizer, and related circulation and processing equipment, achieving fully automated control from raw materials to finished products. This not only improves production efficiency and product quality consistency but also eliminates the need for separate reaction, concentration, crystallization, and tail gas scrubbing equipment by simultaneously completing multiple steps in the integrated continuous crystallizer. This significantly reduces the required equipment quantity and floor space, thereby lowering initial investment costs and long-term operating expenses. Compared to traditional methods that control crystallization particle size solely by controlling crystallization temperature and residence time, resulting in a wide particle size distribution and poor product stability, this system's integrated continuous crystallizer provides more precise control over the slurry crystallization process. Fine crystals are extracted by a crystallization circulation pump, dissolved by a crystallization heater, and returned to the integrated continuous crystallizer, resulting in uniformly sized large-particle crystals with more concentrated particle size distribution and high product stability.

[0034] It is understandable that the beneficial effects of the second aspect mentioned above can be found in the relevant descriptions in the first aspect mentioned above, and will not be repeated here. Attached Figure Description

[0035] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0036] Figure 1 This is a schematic diagram of a phosphate continuous crystallization system provided in one embodiment of this application;

[0037] In the diagram, 100-monoammonium phosphate production system, 1-pre-neutralizer, 2-pre-neutralization circulation pump, 3-pre-neutralization heater, 4-high-efficiency ammoniation reactor, 5-feed pump, 6-mist separator, 7-integrated continuous crystallizer, 8-integrated continuous crystallizer agitator, 9-crystallization circulation pump, 10-crystallization heater, 11-crystallization vacuum condensation system, 12-crystallization material pump, 13-thickener, 14-thickening rake, 15-centrifuge, 16-mother liquor collection tank, 17-mother liquor collection tank agitator, 18-crystallization washing circulation pump, 19-washing circulation pump, 20-demister cleaning nozzle, 21-gas washing nozzle, 22-gas distributor. Detailed Implementation

[0038] In the following description, specific details such as particular system architectures and techniques are set forth for illustrative purposes and not for limitation, in order to provide a thorough understanding of the embodiments of this application. However, those skilled in the art will understand that this application may also be implemented in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, apparatuses, circuits, and methods have been omitted so as not to obscure the description of this application with unnecessary detail.

[0039] It should also be understood that the term “and / or” as used in this application specification and the appended claims means any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0040] Furthermore, in the description of this application and the appended claims, the terms "first," "second," "third," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0041] References to "one embodiment" or "some embodiments" as described in this specification mean that one or more embodiments of this application include a specific feature, structure, or characteristic described in connection with that embodiment. Therefore, the phrases "in one embodiment," "in some embodiments," "in other embodiments," "in still other embodiments," etc., appearing in different parts of this specification do not necessarily refer to the same embodiment, but rather mean "one or more, but not all, embodiments," unless otherwise specifically emphasized. The terms "comprising," "including," "having," and variations thereof mean "including but not limited to," unless otherwise specifically emphasized.

[0042] like Figure 1 As shown in the embodiments of this application, a continuous phosphate crystallization system is characterized by comprising a monoammonium phosphate generating system 100, an integrated continuous crystallizer 7, a crystallization circulation pump 9, a crystallization heater 10, a crystallization vacuum condensation system 11, a crystallization material pump 12, a thickener 13, and a centrifuge 15.

[0043] Monoammonium phosphate generation system 100 is used to obtain monoammonium phosphate slurry based on phosphoric acid of a first concentration.

[0044] The integrated continuous crystallizer 7 includes a washing section located at the top for washing the crystallization tail gas and a reaction crystallization section located at the bottom. The top of the washing section is connected to the crystallization vacuum condensation system 11. The raw material input end of the integrated continuous crystallizer 7 is connected to the second concentration raw materials phosphoric acid and ammonia, or to the monoammonium phosphate slurry output end of the monoammonium phosphate generation system 100. The circulating material output end of the integrated continuous crystallizer 7 is connected to the circulating material input end of the integrated continuous crystallizer 7 in sequence through the crystallization circulating pump 9 and the crystallization heater 10. The crystallization material output end of the integrated continuous crystallizer 7 is connected to the input end of the centrifuge 15 in sequence through the crystallization material pump 12 and the thickener 13. The centrifuge 15 outputs phosphate to be dried, which is used to obtain phosphate after drying.

[0045] The concentration of the first-concentration raw material phosphoric acid is lower than that of the second-concentration raw material phosphoric acid.

[0046] In the application, the monoammonium phosphate (MAP) generation system 100 processes a first-concentration raw material phosphoric acid (its concentration is lower than that of a second-concentration raw material phosphoric acid) to generate a MAP slurry through a chemical reaction. This slurry, or the second-concentration raw material phosphoric acid, is fed into an integrated continuous crystallizer 7 along with ammonia gas. In the integrated continuous crystallizer 7, the material undergoes washing, reaction, and crystallization processes. Material circulation within the integrated continuous crystallizer 7 is maintained by a crystallization circulation pump 9 and a crystallization heater 10. The resulting crystalline material is then transported to a centrifuge 15 via a crystallization material pump 12 and a thickener 13 for solid-liquid separation to obtain phosphate to be dried. These solids are then dried to become the finished phosphate product. An integrated continuous crystallizer agitator 8 is installed at the bottom of the integrated continuous crystallizer 7. The agitator 8 is a propeller type with a rotation speed of 6000-12000 rpm. A crystallization vacuum condensation system 11 is connected to the top of the integrated continuous crystallizer 7 to maintain a vacuum and condense the evaporated moisture. When using monoammonium phosphate slurry as raw material, the integrated continuous crystallizer 7 does not require an external fresh steam source for heating; its heating source comes from the flash vapor in the pre-neutralization reactor 1 of the monoammonium phosphate generation system 100. When using phosphoric acid of a second concentration (such as 75% or 85% H3PO4 industrial / food grade phosphoric acid) as raw material, it also does not require an external fresh steam source for heating; its heating source is the heat of reaction between phosphoric acid and ammonia.

[0047] In one embodiment, the monoammonium phosphate generating system 100 includes a pre-neutralization reactor 1, a mist separator 6, a pre-neutralization circulation pump 2, a pre-neutralization heater 3, an ammoniation reactor 4, and a feed pump 5.

[0048] The steam outlet of the pre-neutralization reactor 1 is connected to the input of the mist separator 6. The gas phase output of the mist separator 6 is connected to the crystallization heater 10. The liquid phase output of the mist separator 6 is connected to the material output of the pre-neutralization reactor 1. The material output of the pre-neutralization reactor 1 is connected to the input of the pre-neutralization circulation pump 2 and the feed pump 5, respectively. The output of the feed pump 5 is the output of the monoammonium phosphate slurry of the monoammonium phosphate generation system 100. The output of the pre-neutralization circulation pump 2 is connected to the input of the pre-neutralization heater 3. The input of the ammoniation reactor 4 is connected to ammonia and the output of the pre-neutralization heater 3. The output of the ammoniation reactor 4 is connected to the circulating material input of the pre-neutralization reactor 1. The material input of the pre-neutralization reactor 1 is used to input the first concentration of raw material phosphoric acid.

[0049] In application, pre-neutralization reactor 1 receives phosphoric acid of a first concentration and undergoes a preliminary neutralization reaction. The reaction temperature in the pre-neutralization reactor is 100-115℃. Pre-neutralization reactor 1 is equipped with a material heater to evaporate more moisture from the material within the reactor, thus achieving neutralization and material concentration functions. The steam generated during the reaction is output from the steam outlet of pre-neutralization reactor 1 to mist separator 6, where the gaseous components are separated and connected to crystallization heater 10 as a heat source via the gas phase output. The liquid components return to pre-neutralization reactor 1 via the liquid phase output of mist separator 6. The material output of pre-neutralization reactor 1 is divided into two paths: one connects to pre-neutralization circulation pump 2 to continue participating in the reaction, and the other outputs monoammonium phosphate slurry via feed pump 5 for subsequent use. Pre-neutralization heater 3 is responsible for heating the material to promote the reaction, while ammoniation reactor 4 is used to introduce ammonia to complete the final ammoniation reaction. The generated material (monoammonium phosphate) is then returned to pre-neutralization reactor 1, forming a closed loop. A small amount of fresh water vapor at 158 ​​degrees Celsius and 0.5 MPa is introduced into the pre-neutralization heater 3 to provide heat.

[0050] In one embodiment, the material ratio range from the material output end of the pre-neutralization reactor 1 to the pre-neutralization circulation pump 2 and the feed pump 5 is 20:1 to 50:1.

[0051] In application, the ratio of material output from the pre-neutralization reactor 1 to the pre-neutralization circulation pump 2 and the feed pump 5 is set to 20:1 to 50:1. This ratio design ensures that most of the material can be continuously heated in the pre-neutralization heater 3, while allowing a suitable amount of monoammonium phosphate slurry to be removed from the system in a timely manner for use in the next stage of processing. By adjusting this ratio, the temperature rise of the material in the pre-neutralization heater 3 can be effectively controlled, mitigating scaling and clogging problems and extending the equipment's operating cycle.

[0052] In one embodiment, phosphoric acid of a second concentration is fed into the washing section of the integrated continuous crystallizer 7, and ammonia is fed into the reaction crystallization section of the integrated continuous crystallizer 7.

[0053] In application, for the integrated continuous crystallizer 7, the second-concentration feedstock phosphoric acid is introduced into its washing section, while ammonia is added to the reaction crystallization section. This arrangement allows the feedstock to be added at the most suitable location to optimize reaction conditions and improve reaction efficiency. Specifically, the direct introduction of the second-concentration feedstock phosphoric acid into the washing section helps improve the tail gas washing effect, while the addition of ammonia to the reaction crystallization section ensures the effective reaction between ammonia and phosphoric acid, promoting the formation of phosphate crystals.

[0054] In one embodiment, the system further includes a mother liquor collection tank 16 and a crystallization washing circulation pump 18. The upper liquid output end of the thickener 13 and the mother liquor output end of the centrifuge 15 are connected to the mother liquor collection tank 16. The input end of the crystallization washing circulation pump 18 is connected to the mother liquor collection tank 16, and the output end of the crystallization washing circulation pump 18 is connected to the recovery material input end of the integrated continuous crystallizer 7.

[0055] In this application, the mother liquor collection tank 16 and the crystallization washing circulation pump 18 together form a closed-loop mother liquor recovery mechanism. The thickener 13 is equipped with a thickening rake 14, and the mother liquor collection tank 16 is equipped with a mother liquor collection tank agitator 17. Liquid from the upper layer of the thickener 13 and mother liquor from the centrifuge 15 are collected in the mother liquor collection tank 16, and then reintroduced into the integrated continuous crystallizer 7 via the crystallization washing circulation pump 18. This not only reduces wastewater discharge and lowers the risk of environmental pollution, but also achieves effective resource reuse and reduces production costs.

[0056] In application, in order to balance the pH value of the mother liquor collection tank 16, phosphoric acid is also introduced into it.

[0057] In one embodiment, the phosphoric acid concentration of the first concentration raw material is in the range of 40% to 58%, and the phosphoric acid concentration of the second concentration raw material is in the range of 75% to 85%.

[0058] In application, the first concentration of raw phosphoric acid has a phosphoric acid concentration of 40-58%, which is a medium concentration. It is suitable for preliminary treatment in the monoammonium phosphate production system 100. The second concentration of raw phosphoric acid has a phosphoric acid concentration of 75%-85%, specifically 75% or 85%, which is a high concentration. It is suitable for direct entry into the integrated continuous crystallizer 7 to participate in the reaction. The selection of the two concentration ranges is based on the optimal process conditions.

[0059] In one embodiment, a washing circulation pump is also included. The washing section of the integrated continuous crystallizer 7 is provided with a demister cleaning nozzle 20, a gas washing nozzle 21 and a gas distributor 22 in sequence from top to bottom. The input end of the washing circulation pump is connected to the top of the gas distributor 22, and the output end of the washing circulation pump is connected to the demister cleaning nozzle 20.

[0060] In this application, the washing section of the integrated continuous crystallizer 7 is equipped with a demister cleaning nozzle 20, a gas washing nozzle 21, and a gas distributor 22, and a washing circulation pump 19 is installed to circulate the washing liquid. This ensures that the exhaust gas can fully contact the washing liquid, effectively removing impurities and harmful substances while avoiding the risk of internal blockage. The design of the washing section improves the reliability and safety of the system, reduces the need for additional exhaust gas washing equipment, and increases the ammonia recovery rate.

[0061] This application provides a method for manufacturing phosphate using a continuous phosphate crystallization system, comprising:

[0062] Phosphoric acid of a first concentration with a phosphoric acid concentration range of 40-58% is fed into the monoammonium phosphate generation system 100 to obtain flash vapor and monoammonium phosphate slurry. The monoammonium phosphate slurry is then fed into the integrated continuous crystallizer 7 to obtain crystalline material.

[0063] Alternatively, phosphoric acid with a phosphoric acid concentration ranging from 75% to 85% and ammonia are fed into the integrated continuous crystallizer 7 to obtain crystalline material.

[0064] The crystalline material was successively concentrated, centrifuged, and dried to obtain phosphate.

[0065] This application targets medium-concentration phosphoric acid (40-58% H3PO4) and combines traditional neutralization reaction with single-effect concentration in a double-effect concentration process. It also integrates the double-effect concentration system with an integrated continuous crystallizer. The reaction solution is then passed through the integrated continuous crystallizer, and the crystallized material is centrifuged and dried to obtain industrial-grade / food-grade phosphate products. This process not only improves the quality stability of industrial-grade / food-grade phosphate products and is suitable for concentrated phosphoric acid such as industrial-grade / food-grade phosphoric acid raw materials as well as medium-concentration phosphoric acid raw materials, but also improves system energy utilization, streamlines the process, reduces equipment, lowers investment, and saves operating costs.

[0066] In one embodiment, it also includes:

[0067] Phosphoric acid of a first concentration with a phosphoric acid concentration range of 40-58% is fed into the pre-neutralization reactor 1, and the materials of the monoammonium phosphate generation system 100 are fed into the pre-neutralization heater 3 and the feed pump 5 respectively in a ratio of 20:1 to 50:1.

[0068] The pre-neutralization heater 3 is used to generate monoammonium phosphate slurry and input it into the circulating material input end of the pre-neutralization reactor 1, and the feed pump 5 is used to output monoammonium phosphate slurry.

[0069] In one embodiment, it also includes:

[0070] Flash steam is fed into crystallizer 10, and integrated continuous crystallizer 7 outputs material to crystallizer 10. After being heated by flash steam in crystallizer 10, the material is returned to integrated continuous crystallizer 7.

[0071] Using phosphoric acid of a first concentration range of 40-58% as raw material, the method for producing phosphates using this system is as follows:

[0072] When using phosphoric acid of the first concentration, it is first fed into the pre-neutralization reactor 1 of the monoammonium phosphate (MAP) generation system 100, where it undergoes a preliminary neutralization reaction with ammonia. After the first concentration of phosphoric acid received in the pre-neutralization reactor 1 is thoroughly mixed with ammonia, the reaction begins, generating MAP slurry and flash vapor. The generated vapor is separated by a mist separator 6; the gaseous component is connected as a heat source to the crystallization heater 10 for subsequent material heating, while the liquid component is returned to the pre-neutralization reactor 1 to continue participating in the reaction.

[0073] The material output of the pre-neutralization reactor 1 is divided into two streams at a ratio of 20:1 to 50:1: one stream enters the pre-neutralization heater 3 for further heating via the pre-neutralization circulation pump 2. In the pre-neutralization heater 3, the material temperature rises by only 1-6 degrees Celsius to mitigate scaling and clogging issues and ensure uniform heating; the other stream outputs monoammonium phosphate slurry via the feed pump 5 for further processing. The output of the feed pump 5 is the monoammonium phosphate slurry output of the monoammonium phosphate production system 100, which is then fed into the reaction crystallization section of the integrated continuous crystallizer 7.

[0074] Within the integrated continuous crystallizer 7, monoammonium phosphate slurry undergoes a series of steps including washing, reaction, concentration, and crystallization. The washing section is located at the top and is connected to the crystallization vacuum condensation system 11, which creates a vacuum inside the integrated continuous crystallizer 7 to achieve crystallization. The washing section is used to wash the crystallization tail gas and recover ammonia and other volatile substances. The reaction and crystallization section is located at the bottom and is the main site of reaction and crystallization. The circulating material output of the integrated continuous crystallizer 7 is connected to the circulating material input of the integrated continuous crystallizer 7 via a crystallization circulating pump 9 and a crystallization heater 10, forming a closed material circulation path to ensure sufficient reaction and crystallization. The resulting crystalline material is discharged from the side port of the integrated continuous crystallizer 7 and enters the thickener 13 via the crystallization material pump 12 for further thickening before entering the centrifuge 15 for solid-liquid separation. The obtained solid phosphate is dried to become the final product. The mother liquor after centrifugation is collected in the mother liquor collection tank 16 through the upper liquid output end of the thickener 13 and the mother liquor output end of the centrifuge 15, and then reintroduced into the recovery material input end of the integrated continuous crystallizer 7 by the crystallization washing circulation pump 18, forming a closed-loop system.

[0075] Using phosphoric acid of a second concentration (75%–85%) as raw material, the following method is employed to manufacture phosphates using this system:

[0076] For the second concentration of phosphoric acid, it is directly added to the washing section of the integrated continuous crystallizer 7, while ammonia is input to the reaction crystallization section. The high-concentration phosphoric acid first enters the washing section of the integrated continuous crystallizer 7. The demister cleaning nozzle 20, gas washing nozzle 21, and gas distributor 22 work together to effectively remove impurities from the exhaust gas, ensuring environmentally friendly production. Simultaneously, ammonia is added from the input end of the reaction crystallization section, rapidly rising to react with the phosphoric acid. At the same time, some moisture evaporates from the material under vacuum, achieving concentration and reaching a supersaturated state to crystallize ammonium phosphate crystals.

[0077] The integrated continuous crystallizer 7 is connected to a crystallization vacuum condensation system 11 at the top to maintain the vacuum state of the system and condense the evaporated water, ensuring that the crystallization process takes place under ideal conditions. The crystallizing material is discharged from the side port of the integrated continuous crystallizer 7 and enters the thickener 13 via the crystallization material pump 12. After further thickening, it enters the centrifuge 15 for solid-liquid separation. The obtained solid phosphate is dried to become the final product. The mother liquor after centrifugation is collected in the mother liquor collection tank 16 through the upper liquid output end of the thickener 13 and the mother liquor output end of the centrifuge 15. It is then reintroduced into the recovery material input end of the integrated continuous crystallizer 7 by the crystallization washing circulation pump 18, forming a closed-loop system.

[0078] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. A method for manufacturing phosphates using a continuous phosphate crystallization system, characterized in that, The system includes a monoammonium phosphate generating system (100), an integrated continuous crystallizer (7), a crystallization circulation pump (9), a crystallization heater (10), a crystallization vacuum condensation system (11), a crystallization material pump (12), a thickener (13), and a centrifuge (15). The monoammonium phosphate generating system (100) is used to obtain a monoammonium phosphate slurry based on a first concentration of raw phosphoric acid; The integrated continuous crystallizer (7) includes a washing section located at the top for washing the crystallization tail gas and a reaction crystallization section located at the bottom. The top of the washing section is connected to the crystallization vacuum condensation system (11). The raw material input end of the integrated continuous crystallizer (7) is connected to the second concentration raw material phosphoric acid and ammonia, or to the monoammonium phosphate slurry output end of the monoammonium phosphate generation system (100). The circulating material output end of the integrated continuous crystallizer (7) is connected to the circulating material input end of the integrated continuous crystallizer (7) in sequence through the crystallization circulating pump (9) and the crystallization heater (10). The crystallization material output end of the integrated continuous crystallizer (7) is connected to the input end of the centrifuge (15) in sequence through the crystallization material pump (12) and the thickener (13). The centrifuge (15) outputs phosphate to be dried. The phosphate to be dried is used to obtain phosphate after drying. Wherein, the concentration of the first concentration raw material phosphoric acid is lower than that of the second concentration raw material phosphoric acid; The second concentration of raw material phosphoric acid is fed into the washing section of the integrated continuous crystallizer (7), and the ammonia gas is fed into the reaction crystallization section of the integrated continuous crystallizer (7); The method includes: Phosphoric acid of a first concentration with a phosphoric acid concentration range of 40-58% is fed into the monoammonium phosphate generation system (100) to obtain flash vapor and monoammonium phosphate slurry. The monoammonium phosphate slurry is then fed into an integrated continuous crystallizer (7) to obtain crystalline material. Alternatively, phosphoric acid with a phosphoric acid concentration range of 75% to 85% and ammonia are fed into an integrated continuous crystallizer (7) to obtain crystalline material; The crystalline material was sequentially concentrated, centrifuged, and dried to obtain phosphate.

2. The phosphate manufacturing method of the phosphate continuous crystallization system as described in claim 1, characterized in that, The monoammonium phosphate production system (100) includes a pre-neutralization reactor (1), a pre-neutralization heater (3), and a feed pump (5), and the method further includes: Phosphoric acid of a first concentration with a phosphoric acid concentration range of 40 to 58% is fed into the pre-neutralization reactor (1), and the materials of the monoammonium phosphate generation system (100) are fed into the pre-neutralization heater (3) and the feed pump (5) in a ratio of 20:1 to 50:1 respectively. The pre-neutralization heater (3) is used to generate monoammonium phosphate slurry and input it into the circulating material input end of the pre-neutralization reactor (1), and the feed pump (5) is used to output monoammonium phosphate slurry.

3. The method for producing phosphate using the continuous crystallization system of phosphate as described in claim 1, characterized in that, Also includes: The flash steam is fed into the crystallization heater (10), and the integrated continuous crystallizer (7) outputs the material to the crystallization heater (10) and returns it to the integrated continuous crystallizer (7) after being heated by the flash steam in the crystallization heater (10).

4. The method for producing phosphate using the continuous crystallization system of phosphate as described in claim 2, characterized in that, The monoammonium phosphate generation system (100) also includes a mist separator (6), a pre-neutralization circulation pump (2), and an ammoniation reactor (4). The steam outlet of the pre-neutralization reactor (1) is connected to the input of the mist separator (6). The gas phase output of the mist separator (6) is connected to the crystallization heater (10). The liquid phase output of the mist separator (6) is connected to the material output of the pre-neutralization reactor (1). The material output of the pre-neutralization reactor (1) is connected to the input of the pre-neutralization circulation pump (2) and the feed pump (5). The output of the feed pump (5) is the output of the monoammonium phosphate slurry of the monoammonium phosphate generation system (100). The output of the pre-neutralization circulation pump (2) is connected to the input of the pre-neutralization heater (3). The input of the ammonification reactor (4) is connected to ammonia and the output of the pre-neutralization heater (3). The output of the ammonification reactor (4) is connected to the circulating material input of the pre-neutralization reactor (1). The material input of the pre-neutralization reactor (1) is used to input the first concentration of raw material phosphoric acid.

5. The method for producing phosphate using the continuous phosphate crystallization system according to claim 1, characterized in that, The system also includes a mother liquor collection tank (16) and a crystallization washing circulation pump (18). The upper liquid output end of the thickener (13) and the mother liquor output end of the centrifuge (15) are connected to the mother liquor collection tank (16). The input end of the crystallization washing circulation pump (18) is connected to the mother liquor collection tank (16). The output end of the crystallization washing circulation pump (18) is connected to the recovery material input end of the integrated continuous crystallizer (7).

6. The method for producing phosphate using the continuous phosphate crystallization system according to claim 1, characterized in that, The system also includes a washing circulation pump. The washing section of the integrated continuous crystallizer (7) is provided with a demister cleaning nozzle (20), a gas washing nozzle (21) and a gas distributor (22) from top to bottom. The input end of the washing circulation pump is connected to the gas distributor (22) above, and the output end of the washing circulation pump is connected to the demister cleaning nozzle (20).

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