Phosphate continuous crystallization system and phosphate manufacturing method

Abstract

The invention relates to the technical field of chemical equipment, and provides a phosphate continuous crystallization system and a phosphate manufacturing method. Comprising a monoammonium phosphate generation 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 a second-concentration raw material phosphoric acid and ammonia gas, or is connected with a monoammonium phosphate slurry output end of a monoammonium phosphate generation system, and a circulating material output end of the integrated continuous crystallizer is connected with a circulating material input end through a crystallization circulating pump and a crystallization heater in sequence; the crystallized material output end is connected with the input end of the centrifugal machine through the crystallized material pump and the thickener in sequence, and the centrifugal machine outputs phosphate to be dried. And process equipment for reaction, concentration, crystallization, tail gas washing and the like is not needed any more, so that the number of required equipment and the occupied area are greatly reduced, and the initial investment cost and the long-term operation cost are reduced.

Description

Technical Field

[0001] The invention relates to the technical field of chemical equipment, and in particular to a phosphate continuous crystallization system and a phosphate manufacturing method. Background Art

[0002] Existing phosphorus chemical enterprises produce industrial-grade / food-grade monoammonium phosphate by generally adopting a production method of reaction of concentrated phosphoric acid (such as 75% or 85% H3PO4 industrial-grade / food-grade phosphoric acid) with ammonia and intermittent crystallization. The product quality is unstable and requires process flows such as neutralization reaction, crystallization, and tail gas washing, as well as major process equipment such as neutralization reactor, crystallizer, and tail gas scrubber. The investment cost is high, the operating cost is high, and the land occupation is large.

[0003] If medium-concentration raw phosphoric acid (40-58% H3PO4) is used, it requires neutralization reaction, double-effect concentration, crystallization, tail gas washing and other process flows, as well as many process equipment and supporting systems such as neutralization reactor, first-effect concentration system, second-effect concentration system, crystallizer, tail gas scrubber, etc. It also has the characteristics of high investment cost, high operating cost and large land occupation.

[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 the present application provide a phosphate continuous crystallization system and a phosphate manufacturing method, which have stable product quality and no longer require the installation of process equipment such as reaction, concentration, crystallization, and exhaust gas washing, thereby greatly reducing the required number of equipment and floor space, thereby reducing initial investment costs and long-term operating costs.

[0006] A first aspect of an embodiment of the present application provides a phosphate continuous crystallization system, including a monoammonium phosphate production system, an integrated continuous crystallizer, a crystallization circulation pump, a crystallization heater, a crystallization vacuum condensation system, a crystallization material pump, a concentrator, and a centrifuge;

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

[0008] The integrated continuous crystallizer comprises a washing section located at the upper part and used for washing the crystallization tail gas, and a reaction crystallization section located at the lower part, 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 used to be connected to the second concentration raw materials of phosphoric acid and ammonia, or to be connected to the monoammonium phosphate slurry output end of the monoammonium phosphate production system, the circulating material output end of the integrated continuous crystallizer is connected to the circulating material input end of the integrated continuous crystallizer through a crystallization circulation pump and a crystallization heater in sequence, the crystallization material output end of the integrated continuous crystallizer is connected to the input end of the centrifuge through the crystallization material pump and the thickener in sequence, the centrifuge outputs the phosphate to be dried, and the phosphate to be dried is used to obtain phosphate after drying;

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

[0010] The embodiment of the present application realizes the full process automation control from raw materials to finished products by integrating the monoammonium phosphate production system, the integrated continuous crystallizer and the related circulation and processing equipment, which not only improves the production efficiency and the consistency of product quality, but also completes the multi-step operations such as reaction, concentration, crystallization and tail gas washing in the integrated continuous crystallizer at the same time, and no longer needs to set up the process equipment such as reaction, concentration, crystallization, tail gas washing, etc., which greatly reduces the required number of equipment and floor space, thereby reducing the initial investment cost and long-term operation cost. The input end of the integrated continuous crystallizer is connected to the output of the monoammonium phosphate production system, or directly connected to the second concentration of raw phosphoric acid and ammonia, and different production processes can be adopted for raw phosphoric acid of different concentrations, which has higher flexibility and applicability. In addition, by reheating the circulating material of the integrated continuous crystallizer in the crystallization heater, the crystallizer is combined with the concentration system function, and the small particle crystals in the crystallizer can also be extracted and dissolved, so that the product particle size distribution tends to the large particle size, and the particle size distribution is more concentrated. The system uses phosphoric acid and ammonia as raw materials, is green and environmentally friendly, has high energy utilization, low production and operation costs, and good energy saving effect.

[0011] In one embodiment, the monoammonium phosphate production 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 end of the pre-neutralization reactor is connected to the input end of the mist separator, the gas phase output end of the mist separator is connected to the crystallization heater, the liquid phase output end of the mist separator is connected to the material output end of the pre-neutralization reactor, the material output end of the pre-neutralization reactor is respectively connected to the input ends of the pre-neutralization circulation pump and the feed pump, the output end of the feed pump is the monoammonium phosphate slurry output end of the monoammonium phosphate production system, the output end of the pre-neutralization circulation pump is connected to the input end of the pre-neutralization heater, the input end of the amination reactor is connected to ammonia gas and the output end of the pre-neutralization heater, the output end of the amination reactor is connected to the circulating material input end of the pre-neutralization reactor, and the material input end of the pre-neutralization reactor is used to input raw phosphoric acid of a first concentration.

[0013] In the embodiment of the present application, the flash gas of the pre-neutralization reactor is separated from the mist and water droplets of the flash gas by a mist separator, thereby increasing the dry gas ratio of the flash gas, thereby facilitating the heat exchange efficiency of the crystallizer heater and effectively preventing the flash gas from scaling in the crystallizer heater. By using the flash gas of the pre-neutralization reactor as the heat source of the crystallizer heater, the heat of the flash gas is effectively utilized, the heat utilization rate of the system is improved, and at the same time, a set of material concentration system is saved, reducing investment and operating costs.

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

[0015] The embodiment of the present application ensures a mild temperature rise (1-6 degrees) of the material in the pre-neutralization heater by reasonably allocating the material flow to the pre-neutralization circulation pump and the feed pump (in a ratio of 20:1 to 50:1), effectively alleviating the internal scaling and clogging problem, extending the operation cycle of the equipment, and ensuring the full reaction of ammonia and phosphoric acid, thereby enhancing the quality of the monoammonium phosphate slurry.

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

[0017] In the embodiment of the present application, the second concentration of raw phosphoric acid is input into the washing section and the ammonia gas is input into the reaction crystallization section, thereby ensuring the tail washing effect and increasing the reaction time with ammonia, thereby achieving full reaction between ammonia and phosphoric acid.

[0018] In one embodiment, it also includes a mother liquor collection tank and a crystal washing circulation pump, the upper liquid output end of the concentrator and the mother liquor output end of the centrifuge are connected to the mother liquor collection tank, the input end of the crystal washing circulation pump is connected to the mother liquor collection tank, and the output end of the crystal washing circulation pump is connected to the recovered material input end of the integrated continuous crystallizer.

[0019] The embodiment of the present application constructs a closed-loop material circulation mechanism by introducing a mother liquor collection tank and a crystal washing circulation pump, so that the upper liquid of the thickener and the mother liquor produced by the centrifuge can be reintroduced into the integrated continuous crystallizer to participate in a new round of reaction. This not only helps to reduce waste emissions and reduce environmental pollution risks, 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 phosphoric acid ranges from 40% to 58%, and the phosphoric acid concentration of the second concentration raw phosphoric acid ranges from 75% to 85%.

[0021] In one embodiment, a washing circulation pump is also included. 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 arranged on the upper part of the integrated continuous crystallizer in the embodiment of the present application includes a demister cleaning nozzle, a gas washing nozzle and a gas distributor, as well as a corresponding washing circulation pump, which realizes effective washing of the crystallization tail gas. This design reduces the demand for additional tail gas washing equipment, improves the recovery rate of ammonia, ensures that the tail gas meets the emission standards, reduces environmental impact, and reflects environmental benefits.

[0023] A second aspect of the embodiments of the present application provides a phosphate manufacturing method of a phosphate continuous crystallization system, comprising:

[0024] Feeding a first concentration of raw phosphoric acid having a phosphoric acid concentration range of 40 to 58% to a monoammonium phosphate production system to obtain flash steam and monoammonium phosphate slurry, and inputting the monoammonium phosphate slurry to an integrated continuous crystallizer to obtain a crystallized material;

[0025] Alternatively, the second raw material phosphoric acid with a phosphoric acid concentration ranging from 75% to 85% and ammonia gas are input into an integrated continuous crystallizer to obtain a crystallized material;

[0026] The crystal material is concentrated, centrifuged and dried in sequence to obtain phosphate.

[0027] The embodiment of the present application provides a flexible selection scheme for raw phosphoric acid of different concentrations: the first concentration raw phosphoric acid of lower concentration (40-58%) is firstly used to generate monoammonium phosphate slurry through the monoammonium phosphate production system; the second concentration raw phosphoric acid of higher concentration (75%-85%) is directly added to the washing section of the integrated continuous crystallizer, and ammonia is sent to the reaction crystallization section. It meets the needs of raw materials of different qualities and ensures that the system can operate under optimal conditions, maximizes the use of reaction heat, ensures product stability and high yield, and simplifies the process flow and reduces energy consumption.

[0028] In one embodiment, it further includes:

[0029] A first concentration of raw phosphoric acid having a phosphoric acid concentration range of 40 to 58% is delivered to the pre-neutralization reactor, and the materials of the monoammonium phosphate production system are respectively input into the pre-neutralization heater and the feed pump at a ratio of 20:1 to 50:1;

[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 the monoammonium phosphate slurry.

[0031] In one embodiment, it further includes:

[0032] The flash steam is input to the crystallization heater, and the integrated continuous crystallizer outputs the material to the crystallization heater, and the material is returned to the integrated continuous crystallizer after being heated by the crystallization heater through the flash steam.

[0033] The phosphate continuous crystallization system provided by the first aspect of the embodiment of the present application realizes the full process automation control from raw materials to finished products by integrating the monoammonium phosphate production system, the integrated continuous crystallizer and the related circulation and processing equipment, which not only improves the production efficiency and the consistency of product quality, but also completes the multi-step operations such as reaction, concentration, crystallization and tail gas washing in the integrated continuous crystallizer at the same time, and no longer needs to set up process equipment such as reaction, concentration, crystallization, tail gas washing, etc., which greatly reduces the required number of equipment and floor space, thereby reducing the initial investment cost and long-term operating cost. Compared with the traditional method of controlling the crystallization particle size only by controlling the crystallization temperature and residence time, the obtained crystal particle size distribution is wide and the product stability is poor. The integrated continuous crystallizer of this system has a more refined control over the slurry crystallization process, extracts the fine crystals through the crystallization circulation pump, heats the fine crystals by the crystallization heater to dissolve the fine crystals and returns them to the integrated continuous crystallizer, thereby obtaining large-particle crystals with uniform particle size, and the particle size classification is more concentrated, and the product stability is high.

[0034] It can be understood that the beneficial effects of the second aspect mentioned above can be found in the relevant description of the first aspect mentioned above, and will not be repeated here. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

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

[0037] In the figure, 100-monoammonium phosphate production system, 1-pre-neutralizer, 2-pre-neutralization circulation pump, 3-pre-neutralization heater, 4-high-efficiency amination reactor, 5-feeding 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 rotary 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 DESCRIPTION

[0038] In the following description, specific details such as specific system structures, technologies, etc. are provided for the purpose of illustration rather than limitation, so as to provide a thorough understanding of the embodiments of the present application. However, it should be clear to those skilled in the art that the present application may also be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits, and methods are omitted to prevent unnecessary details from obstructing the description of the present application.

[0039] It should also be understood that the term “and / or” used in the specification and appended claims refers to any and all possible combinations of one or more of the associated listed items, and includes these combinations.

[0040] In addition, in the description of the present application specification and the appended claims, the terms "first", "second", "third", etc. are only used to distinguish the descriptions and cannot be understood as indicating or implying relative importance.

[0041] References to "one embodiment" or "some embodiments" etc. described in the specification of this application mean that one or more embodiments of the present application include specific features, structures or characteristics described in conjunction with the embodiment. Therefore, the statements "in one embodiment", "in some embodiments", "in some other embodiments", "in some other embodiments", etc. that appear in different places in this specification do not necessarily refer to the same embodiment, but mean "one or more but not all embodiments", unless otherwise specifically emphasized in other ways. The terms "including", "comprising", "having" and their variations all mean "including but not limited to", unless otherwise specifically emphasized in other ways.

[0042] like Figure 1 As shown, the phosphate continuous crystallization system provided in the embodiment of the present application is a phosphate continuous crystallization system, characterized in that it includes a monoammonium phosphate production 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 concentrator 13 and a centrifuge 15;

[0043] The MAP production system 100 is used to obtain MAP slurry based on raw phosphoric acid with a first concentration;

[0044] The integrated continuous crystallizer 7 includes a washing section located at the upper part and used for washing the crystallization tail gas, and a reaction crystallization section located at the lower part. 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 used to be connected to the second concentration raw materials of phosphoric acid and ammonia, or to be connected to the monoammonium phosphate slurry output end of the monoammonium phosphate production 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 through the crystallization circulation pump 9 and the crystallization heater 10 in sequence. The crystallization material output end of the integrated continuous crystallizer 7 is connected to the input end of the centrifuge 15 through the crystallization material pump 12 and the thickener 13 in sequence. The centrifuge 15 outputs the phosphate to be dried, and the phosphate to be dried is used to obtain phosphate;

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

[0046] In application, the monoammonium phosphate production system 100 is used to process raw phosphoric acid of a first concentration (whose concentration is lower than that of raw phosphoric acid of a second concentration) to generate monoammonium phosphate slurry through chemical reaction. The slurry or the second concentration raw phosphoric acid is fed into the integrated continuous crystallizer 7 together with ammonia. In the integrated continuous crystallizer 7, the material undergoes washing, reaction and crystallization processes. The material circulation inside the integrated continuous crystallizer 7 is maintained by a crystallization circulation pump 9 and a crystallization heater 10, and the crystallized material finally produced is transported to a centrifuge 15 via a crystallization material pump 12 and a concentrator 13 for solid-liquid separation to obtain phosphate to be dried, and these solids become finished phosphates after drying. An integrated continuous crystallizer agitator 8 is arranged at the bottom of the integrated continuous crystallizer 7, and the integrated continuous crystallizer agitator 8 is a propulsion type with a rotation speed of 6000-12000rmp. A crystallization vacuum condensation system 11 is connected to the top of the integrated continuous crystallizer 7 to maintain a vacuum state and condense evaporated water. When the integrated continuous crystallizer 7 uses monoammonium phosphate slurry as raw material, it does not need to add fresh steam to provide a heat source, and its heating heat source comes from the flash gas of the pre-neutralization reactor 1 in the monoammonium phosphate production system 100; when the second concentration raw phosphoric acid (such as 75% or 85% H3PO4 industrial grade / food grade phosphoric acid) is used as raw material, it also does not need to add fresh steam to provide a heat source, and the heating heat source is the reaction heat of phosphoric acid and ammonia.

[0047] In one embodiment, the monoammonium phosphate production 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 end of the pre-neutralization reactor 1 is connected to the input end of the mist separator 6, the gas phase output end of the mist separator 6 is connected to the crystallization heater 10, the liquid phase output end of the mist separator 6 is connected to the material output end of the pre-neutralization reactor 1, the material output end of the pre-neutralization reactor 1 is respectively connected to the input ends of the pre-neutralization circulation pump 2 and the feed pump 5, the output end of the feed pump 5 is the monoammonium phosphate slurry output end of the monoammonium phosphate production system 100, the output end of the pre-neutralization circulation pump 2 is connected to the input end of the pre-neutralization heater 3, the input end of the ammoniation reactor 4 is connected to the output ends of ammonia gas and the pre-neutralization heater 3, the output end of the ammoniation reactor 4 is connected to the circulating material input end of the pre-neutralization reactor 1, and the material input end of the pre-neutralization reactor 1 is used to input raw phosphoric acid of a first concentration.

[0049] In application, the pre-neutralization reactor 1 receives the first concentration of raw phosphoric acid and performs a preliminary neutralization reaction therein, and the reaction temperature of the pre-neutralization reactor is 100-115°C. The pre-neutralization reactor 1 is provided with a material heater to evaporate more water from the material in the neutralization reactor, thereby realizing the neutralization and material concentration functions of the pre-neutralizer. The steam generated during the reaction is output from the steam outlet of the pre-neutralization reactor 1 to the mist separator 6, where the gas component is separated and connected to the crystallization heater 10 as a heat source through the gas phase output end; the liquid component returns to the pre-neutralization reactor 1 through the liquid phase output end of the mist separator 6. The material output end of the pre-neutralization reactor 1 is divided into two paths, one of which is connected to the pre-neutralization circulation pump 2 to continue to participate in the reaction, and the other is output through the feed pump 5 for subsequent use. The pre-neutralization heater 3 is responsible for heating the material to promote the reaction, and the ammonia reactor 4 is used to introduce ammonia to complete the final ammonia reaction, and the generated material (monoammonium phosphate) is returned to the pre-neutralization reactor 1 to form a closed cycle. A small amount of fresh steam with a temperature of 158 degrees and 0.5 MPag is introduced into the pre-neutralization heater 3 to provide heat.

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

[0051] In application, the ratio of the material output end of 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 an appropriate amount of monoammonium phosphate slurry to be removed from the system in time for the next stage of treatment. By adjusting this ratio, the temperature rise of the material in the pre-neutralization heater 3 can be effectively controlled, the scaling and clogging problem can be alleviated, and the equipment operation cycle can be extended.

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

[0053] In application, for the integrated continuous crystallizer 7, the second concentration raw phosphoric acid is introduced into its washing section, and ammonia is added to the reaction crystallization section. This arrangement allows the raw materials to be added at the most suitable position to optimize the reaction conditions and improve the reaction efficiency. Among them, the second concentration raw phosphoric acid directly entering the washing section helps to improve the tail gas washing effect, and the addition of ammonia to the reaction crystallization section ensures the effective reaction of ammonia and phosphoric acid and promotes the formation of phosphate crystals.

[0054] In one embodiment, it also includes a mother liquor collecting tank 16 and a crystal washing circulation pump 18. The upper liquid output end of the concentrator 13 and the mother liquor output end of the centrifuge 15 are connected to the mother liquor collecting tank 16, the input end of the crystal washing circulation pump 18 is connected to the mother liquor collecting tank 16, and the output end of the crystal washing circulation pump 18 is connected to the recycled material input end of the integrated continuous crystallizer 7.

[0055] In the application, the mother liquor collection tank 16 and the crystal washing circulation pump 18 together constitute a closed-loop mother liquor recovery mechanism. The thickener 13 is provided with a thickening rotary rake 14, and the mother liquor collection tank 16 is provided with a mother liquor collection tank agitator 17. The liquid from the upper layer of the thickener 13 and the mother liquor from the centrifuge 15 are collected in the mother liquor collection tank 16, and then these liquids are reintroduced into the integrated continuous crystallizer 7 through the crystal washing circulation pump 18. Not only does it reduce wastewater discharge and environmental pollution risks, it also achieves effective reuse of resources and reduces production costs.

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

[0057] In one embodiment, the phosphoric acid concentration of the first concentration raw phosphoric acid ranges from 40% to 58%, and the phosphoric acid concentration of the second concentration raw phosphoric acid ranges from 75% to 85%.

[0058] In the application, the phosphoric acid concentration of the first concentration raw phosphoric acid is 40-58%, that is, the medium concentration raw phosphoric acid. It is suitable for preliminary treatment in the monoammonium phosphate production system 100; the phosphoric acid concentration of the second concentration raw phosphoric acid is 75%-85%, specifically, it can be 75% or 85% raw phosphoric acid, that is, high concentration raw phosphoric acid. It is suitable for directly entering the integrated continuous crystallizer 7 to participate in the reaction. The selection of the two concentration ranges is set 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 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 the 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 provided for circulating the washing liquid. This ensures that the tail gas can fully contact the washing liquid, effectively remove impurities and harmful substances, and avoids the risk of internal blockage of the equipment. The design of the washing section improves the reliability and safety of the system, reduces the need for additional tail gas washing equipment, and improves the recovery rate of ammonia.

[0061] The present application provides a phosphate production method of a phosphate continuous crystallization system, comprising:

[0062] A first concentration raw phosphoric acid having a phosphoric acid concentration range of 40 to 58% is delivered to a monoammonium phosphate production system 100 to obtain flash steam and a monoammonium phosphate slurry, and the monoammonium phosphate slurry is input into an integrated continuous crystallizer 7 to obtain a crystallized material;

[0063] Alternatively, the second raw material phosphoric acid with a phosphoric acid concentration ranging from 75% to 85% and ammonia gas are input into the integrated continuous crystallizer 7 to obtain a crystallized material;

[0064] The crystalline material is concentrated, centrifuged and dried in sequence to obtain phosphate.

[0065] The present application is aimed at medium-concentration raw phosphoric acid (40-58% H3PO4), combines the traditional neutralization reaction with the first-effect concentration in the double-effect concentration, combines the second-effect concentration system of the double-effect concentration with the integrated continuous crystallizer, and then passes the reaction liquid through the integrated continuous crystallizer, and the crystallized material is centrifuged and dried to obtain an industrial-grade / food-grade phosphate product. This process not only improves the quality stability of the industrial-grade / food-grade phosphate product, but also adapts to concentrated phosphoric acid such as industrial-grade / food-grade phosphoric acid raw materials and medium-concentration phosphoric acid raw materials, and at the same time improves the energy utilization rate of the system, compresses the process flow, reduces equipment, reduces investment, and saves operating costs.

[0066] In one embodiment, it further includes:

[0067] A first concentration of raw phosphoric acid having a phosphoric acid concentration range of 40 to 58% is delivered to the pre-neutralization reactor 1, and materials of the monoammonium phosphate production system 100 are respectively delivered to the pre-neutralization heater 3 and the feed pump 5 at 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 the monoammonium phosphate slurry.

[0069] In one embodiment, it further includes:

[0070] The flash steam is input to the crystallization heater 10, and the integrated continuous crystallizer 7 outputs the material to the crystallization heater 10, and returns to the integrated continuous crystallizer 7 after being heated by the flash steam in the crystallization heater 10.

[0071] Using phosphoric acid having a first concentration of 40 to 58% as a raw material, the method for producing phosphate using the system is as follows:

[0072] When using the first concentration raw phosphoric acid, the phosphoric acid is first fed into the pre-neutralization reactor 1 in the monoammonium phosphate production system 100, where it undergoes a preliminary neutralization reaction with ammonia. The first concentration raw phosphoric acid received by the pre-neutralization reactor 1 is fully mixed with ammonia and then reacts to generate monoammonium phosphate slurry and flash steam. The generated steam is separated by the mist separator 6, and the gas component is connected to the crystallization heater 10 as a heat source for subsequent material heating, while the liquid component returns to the pre-neutralization reactor 1 to continue to participate in the reaction.

[0073] The material output end of the pre-neutralization reactor 1 is divided into two paths according to a ratio of 20:1 to 50:1: one path enters the pre-neutralization heater 3 through the pre-neutralization circulation pump 2 for further heating. In the pre-neutralization heater 3, the material temperature rises by only 1-6 degrees to alleviate the scaling and clogging problem and ensure uniform heating; the other path outputs the monoammonium phosphate slurry through the feed pump 5 for the next step of processing. The output end of the feed pump 5 is the monoammonium phosphate slurry output end of the monoammonium phosphate production system 100, and the slurry is then sent to the reaction crystallization section of the integrated continuous crystallizer 7.

[0074] In the integrated continuous crystallizer 7, the monoammonium phosphate slurry undergoes a series of steps such as washing, reaction, concentration and crystallization. The washing section is located at the upper part, and the top is connected to the crystallization vacuum condensation system 11. The crystallization vacuum condensation system 11 is used to evacuate the inside of the integrated continuous crystallizer 7 to achieve crystallization. The washing section is used to wash the crystallization tail gas and recover the ammonia and other volatile substances therein. The reaction crystallization section is located at the lower part and is the main place for reaction and crystallization. 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 through the crystallization circulation pump 9 and the crystallization heater 10 in turn, forming a closed material circulation path to ensure that the material can fully react and crystallize. The final crystallized material is sent out from the side nozzle of the integrated continuous crystallizer 7, enters the thickener 13 through the crystallization material pump 12, and enters the centrifuge 15 for solid-liquid separation after further thickening. The obtained solid phosphate becomes the final product after drying. The mother liquor after centrifugation is collected into 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 with a phosphoric acid concentration range of 75% to 85% as a raw material, the method for producing phosphate using the system is as follows:

[0076] For the second concentration of raw phosphoric acid, it is directly added to the washing section of the integrated continuous crystallizer 7, while ammonia is input into the reaction crystallization section. High-concentration phosphoric acid first enters the washing section of the integrated continuous crystallizer 7, and the demister cleaning nozzle 20, the gas washing nozzle 21 and the gas distributor 22 work together to effectively remove impurities in the tail gas and ensure environmentally friendly production. At the same time, ammonia is added from the input end of the reaction crystallization section, rises rapidly and reacts with phosphoric acid, and at the same time, the material evaporates part of the water under vacuum to achieve concentration, and reaches a supersaturated state to crystallize ammonium phosphate crystals.

[0077] The top of the integrated continuous crystallizer 7 is connected to a crystallization vacuum condensation system 11, which is used to maintain the vacuum state of the system and condense the evaporated water to ensure that the crystallization process is carried out under ideal conditions. The crystallized material is sent out from the side nozzle of the integrated continuous crystallizer 7, enters the thickener 13 through the crystallization material pump 12, and enters the centrifuge 15 for solid-liquid separation after further thickening. The obtained solid phosphate becomes the final product after drying. The mother liquor after centrifugation is collected into 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 recovered material input end of the integrated continuous crystallizer 7 by the crystallization washing circulation pump 18 to form a closed-loop system.

[0078] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application, and should all be included in the protection scope of the present application.

Claims

1. A phosphate continuous crystallization system, characterized in that: It comprises a monoammonium phosphate production 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 concentrator (13) and a centrifuge (15); The monoammonium phosphate production system (100) is used to obtain a monoammonium phosphate slurry based on a first concentration of raw phosphoric acid; The integrated continuous crystallizer (7) comprises a washing section located at the top and used 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 used to be connected to the second concentration raw materials of phosphoric acid and ammonia, or to be connected to the monoammonium phosphate slurry output end of the monoammonium phosphate production 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) through a crystallization circulation pump (9) and a crystallization heater (10) in sequence. The crystallization material output end of the integrated continuous crystallizer (7) is connected to the input end of the centrifuge (15) through the crystallization material pump (12) and the thickener (13) in sequence. The centrifuge (15) outputs the phosphate to be dried, and the phosphate to be dried is used to obtain phosphate. The concentration of the first-concentration raw phosphoric acid is lower than that of the second-concentration raw phosphoric acid.

2. The phosphate continuous crystallization system according to claim 1, characterized in that: The monoammonium phosphate production system (100) comprises 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); The steam outlet end of the pre-neutralization reactor (1) is connected to the input end of the mist separator (6), the gas phase output end of the mist separator (6) is connected to the crystallization heater (10), the liquid phase output end of the mist separator (6) is connected to the material output end of the pre-neutralization reactor (1), the material output end of the pre-neutralization reactor (1) is respectively connected to the input ends of the pre-neutralization circulation pump (2) and the feed pump (5), the output end of the feed pump (5) is the monoammonium phosphate slurry output end of the monoammonium phosphate production system (100), the output end of the pre-neutralization circulation pump (2) is connected to the input end of the pre-neutralization heater (3), the input end of the ammoniation reactor (4) is connected to ammonia gas and the output end of the pre-neutralization heater (3), the output end of the ammoniation reactor (4) is connected to the circulating material input end of the pre-neutralization reactor (1), and the material input end of the pre-neutralization reactor (1) is used to input raw phosphoric acid of a first concentration.

3. The phosphate continuous crystallization system according to claim 2, characterized in that: The ratio of materials output from the material output end of the pre-neutralization reactor (1) to the pre-neutralization circulation pump (2) and the feed pump (5) is in the range of 20:1 to 50:

1.

4. The phosphate continuous crystallization system according to claim 1, characterized in that: The second concentration raw phosphoric acid is input into the washing section of the integrated continuous crystallizer (7), and the ammonia gas is input into the reaction crystallization section of the integrated continuous crystallizer (7).

5. The phosphate continuous crystallization system according to claim 1, characterized in that: It also includes a mother liquor collecting tank (16) and a crystal washing circulation pump (18), the upper liquid output end of the concentrator (13) and the mother liquor output end of the centrifuge (15) are connected to the mother liquor collecting tank (16), the input end of the crystal washing circulation pump (18) is connected to the mother liquor collecting tank (16), and the output end of the crystal washing circulation pump (18) is connected to the recycled material input end of the integrated continuous crystallizer (7).

6. The phosphate continuous crystallization system according to claim 1, characterized in that: The phosphoric acid concentration of the first-concentration raw phosphoric acid ranges from 40% to 58%, and the phosphoric acid concentration of the second-concentration raw phosphoric acid ranges from 75% to 85%.

7. The phosphate continuous crystallization system according to claim 1, characterized in that: It 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) 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).

8. A method for producing phosphate using a phosphate continuous crystallization system according to any one of claims 1 to 7, characterized in that: include: A first concentration of raw phosphoric acid having a phosphoric acid concentration in the range of 40 to 58% is delivered to a monoammonium phosphate production system (100) to obtain flash steam and monoammonium phosphate slurry, and the monoammonium phosphate slurry is delivered to an integrated continuous crystallizer (7) to obtain a crystallized material; Alternatively, the second raw material phosphoric acid with a phosphoric acid concentration ranging from 75% to 85% and ammonia gas are input into an integrated continuous crystallizer (7) to obtain a crystallized material; The crystal material is concentrated, centrifuged and dried in sequence to obtain phosphate.

9. The method for producing phosphate in the phosphate continuous crystallization system according to claim 8, characterized in that: Also includes: A first concentration of raw phosphoric acid having a phosphoric acid concentration in the range of 40 to 58% is delivered to the pre-neutralization reactor (1), and materials of the monoammonium phosphate production system (100) are respectively delivered to the pre-neutralization heater (3) and the feed pump (5) at a ratio of 20:1 to 50:1; 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 the monoammonium phosphate slurry.

10. The method for producing phosphate in the phosphate continuous crystallization system according to claim 8, characterized in that: Also includes: The flash steam is input into the crystallization heater (10), the integrated continuous crystallizer (7) outputs the material to the crystallization heater (10), and the material is returned to the integrated continuous crystallizer (7) after being heated by the flash steam in the crystallization heater (10).

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