CN221243986U - System for producing lithium dihydrogen phosphate by heat pump steam coupling low-temperature evaporation crystallization - Google Patents

Abstract

The utility model relates to a system for producing lithium dihydrogen phosphate by heat pump steam coupling low-temperature evaporative crystallization, which comprises a heat pump steam system of reverse Carnot cycle and an evaporative crystallization system of two-effect forced circulation; the heat pump steam system comprises a refrigerant evaporator, a compressor, a refrigerant condenser, a hot water circulating pump, an expansion valve and a chilled water pump which are connected through pipelines for refrigerant circulation; the evaporation crystallization system comprises a first-effect heater, a first-effect separator, a second-effect heater, a second-effect separator, a steam condenser and a vacuum system which are connected through pipelines, wherein the system comprises a low-temperature two-effect evaporation crystallizer, a DTB or Oslo crystallizer is adopted, and lithium dihydrogen phosphate obtained through continuous crystallization is larger than lithium dihydrogen phosphate particles obtained through flash evaporation crystallization while evaporating at low temperature at the second effect, so that the subsequent solid-liquid separation is facilitated; the system adopts the inverse Carnot circulation heat pump negative pressure steam generator, adopts the refrigerant to recover the heat of the condenser, generates negative pressure steam and realizes the recycling of energy.

Description

System for producing lithium dihydrogen phosphate by heat pump steam coupling low-temperature evaporation crystallization

Technical Field

The utility model belongs to the technical field of products prepared by evaporative crystallization, and relates to a system for producing lithium dihydrogen phosphate by heat pump steam coupling low-temperature evaporative crystallization.

Background

Lithium dihydrogen phosphate is an important inorganic salt and is mainly used for preparing cathode materials (such as LiFePO ₄). The lithium dihydrogen phosphate has higher electrochemical stability and good solubility, and is beneficial to improving the capacity and the cycle life of the battery.

The preparation method of the lithium dihydrogen phosphate mainly comprises the following steps:

1. Direct synthesis: mixing lithium source (such as lithium carbonate or lithium hydroxide) and phosphoric acid source (such as orthophosphoric acid or pyrophosphoric acid) according to a certain proportion, and directly synthesizing lithium dihydrogen phosphate at high temperature. The disadvantage of this method is the high temperature and the high energy consumption.

2. And (3) a double decomposition method: and carrying out double decomposition reaction on the phosphoric acid solution and the lithium hydroxide solution to generate lithium dihydrogen phosphate and lithium hydroxide. The process requires control of the reaction temperature and pH to ensure product purity and yield stability.

The lithium dihydrogen phosphate solution obtained by the above method has a concentration of about 40%, and if lithium dihydrogen phosphate crystals are further obtained, it is necessary to evaporate excessive water. The solution concentration and temperature relationship is shown in fig. 1 due to the great solubility of lithium dihydrogen phosphate. It can be seen from the figure that the solubility of lithium dihydrogen phosphate in water is very high, and the solubility increases with the temperature, so that the lithium dihydrogen phosphate is usually evaporated from a dilute solution to obtain a solution with high concentration, such as a common single-effect or multiple-effect evaporator, and the temperature of the concentrated solution obtained from the single-effect or multiple-effect evaporator is usually higher than 50 ℃ due to the temperature limitation of a cooling tower in summer (the temperature is usually higher than 30 ℃), and then the lithium dihydrogen phosphate solution with high temperature and high concentration is cooled for crystallization or flash evaporation for crystallization, so as to obtain crystals of lithium dihydrogen phosphate, as shown in fig. 2.

The patent adopts the reverse Carnot cycle heat pump unit, and simultaneously provides low-pressure steam (heat source) at 70-100 ℃ and chilled water (cold source) at 10-30 ℃. Then, the conventional single-effect or multi-effect evaporator requires an external cooling tower, especially in summer, and the cooling water temperature of the cooling tower is high, so that the conventional single-effect or multi-effect production is greatly influenced by the environment. The two-effect evaporator provided with the reverse Carnot cycle heat pump unit is a relatively closed system, is not influenced by external environment, and can realize direct evaporation crystallization of lithium dihydrogen phosphate due to low temperature of provided chilled water, and obtain lithium dihydrogen phosphate crystals during evaporation.

Disclosure of utility model

In view of the above, the utility model provides a system for producing lithium dihydrogen phosphate by vapor coupling low-temperature evaporation crystallization of a heat pump, which aims to solve the problems that the existing lithium dihydrogen phosphate preparation method is adopted to prepare lithium dihydrogen phosphate crystals, the evaporation crystallization process is greatly influenced by environment, the uniformity of obtained lithium dihydrogen phosphate particles is poor, and the product quality is poor.

In order to achieve the above purpose, the present utility model provides the following technical solutions:

A system for producing lithium dihydrogen phosphate by heat pump steam coupling low-temperature evaporative crystallization comprises a heat pump steam system of reverse Carnot cycle and an evaporative crystallization system of two-effect forced circulation;

The heat pump steam system comprises a refrigerant evaporator, a compressor, a refrigerant condenser, a hot water circulating pump, an expansion valve and a chilled water pump which are connected through pipelines to circulate the refrigerant, and the hot water circulating pump realizes water circulation in the refrigerant condenser;

The evaporative crystallization system comprises a first-effect heater, a first-effect separator, a second-effect heater, a second-effect separator, a water vapor condenser and a vacuum system which are connected through pipelines, wherein the temperature and the absolute pressure of the first-effect heater are respectively 70-100 ℃ and 30-100Kpa, the temperature and the absolute pressure of the second-effect heater are respectively 50-60 ℃ and 12-20Kpa, and the temperature and the absolute pressure of the water vapor condenser are respectively 25-40 ℃ and 3-8Kpa; the primary separator is connected with a raw material tank with a feed pump, low-pressure steam generated by the refrigerant evaporator enters the primary separator to carry out primary flash evaporation on material flow after heat exchange of the primary heater, and the material is concentrated; the DTB crystallizer is arranged in the secondary separator, secondary steam generated by the primary separator enters the secondary separator to carry out secondary evaporation crystallization on the material flow after heat exchange of the secondary heater, condensed water in the secondary heater is discharged into the water vapor condenser, secondary steam generated by the secondary separator enters the water vapor condenser and is discharged after condensed water, the refrigerant evaporator is connected with a water vapor condenser pipeline to recycle secondary steam heat, and a vacuum system connected with the water vapor condenser adopts a Roots pump and a water ring vacuum pump or a screw vacuum pump, so that the absolute vacuum degree reaches 0.5-3Kpa, and the high vacuum degree of the secondary separator is ensured.

Further, the top of the refrigerant condenser is a refrigerant condenser upper pipe box, the bottom of the refrigerant condenser is a refrigerant condenser lower pipe box, and the hot water circulating pump is communicated between the refrigerant condenser upper pipe box and the refrigerant condenser lower pipe box to realize water circulation in the refrigerant condenser.

Further, the upper part of the refrigerant condenser is provided with a refrigerant gas-phase inlet, the lower part of the refrigerant condenser is provided with a refrigerant liquid-phase outlet, and the refrigerant evaporator, the compressor, the expansion valve and the chilled water pump are communicated between the refrigerant gas-phase inlet and the refrigerant liquid-phase outlet to realize refrigerant circulation.

Further, a low-pressure steam outlet, a low-pressure steam condensate water return port and a pure water supplementing port are arranged on the lower pipe box of the refrigerant condenser.

Further, an effective heater steam inlet communicated with the low-pressure steam outlet is formed in the upper portion of the effective heater, an effective heater condensate water outlet communicated with the low-pressure steam condensate water return port is formed in the lower portion of the effective heater, a low-pressure steam condensate water temperature sensor is installed on a connecting pipeline, and the low-pressure steam temperature sensor is installed on a pipeline connected with the effective heater steam inlet from the low-pressure steam outlet.

Further, a refrigerant condenser lower pipe box liquid level meter is arranged on the refrigerant condenser lower pipe box, an effective separator liquid level meter which is convenient for observing the liquid level in the effective separator is arranged on the effective separator, and a two-effect separator liquid level meter which is convenient for observing the liquid level in the two-effect separator is arranged on the two-effect separator.

Further, an effective automatic feed valve is arranged on a pipeline, the upper part of the effective separator is connected with the feed pump, an effective forced circulation pump which is communicated with the effective heater and the effective separator is arranged below the effective heater and the effective separator, and the effective forced circulation pump is used for pushing steam circulation in the effective heater and material circulation heat exchange in the effective separator to flash evaporation, so that materials are concentrated, and the effective automatic feed valve is in coordination with a liquid level meter of the effective separator to regulate the liquid level in the effective separator to be stable.

Further, the two-effect heater, two-effect separator below is provided with the two-effect forced circulation pump that all communicates with two-effect heater and two-effect separator, through taking one effect to two-effect to change the pipeline intercommunication of material automatic valve between one-effect forced circulation pump and the two-effect forced circulation pump, the material is by one effect through one effect to two-effect to change the material automatic valve from one-effect forced circulation pump export forward flow to two-effect forced circulation pump entry and then transport to two-effect separator, one effect to two-effect to change material automatic valve and two-effect separator level gauge coordination cooperation, the liquid level is stable in the regulation two-effect separator.

Further, the bottom of the two-effect separator is connected with a two-effect discharging pump, the middle part of the two-effect separator is connected with a solid-liquid separation system with a two-effect discharging automatic valve, after the material is subjected to two-effect evaporation crystallization, lithium dihydrogen phosphate crystals enter the DTB crystallizer, part of the lithium dihydrogen phosphate crystals are recycled in the two-effect by the two-effect discharging pump, and the part of the lithium dihydrogen phosphate crystals are discharged into the solid-liquid separation system through the two-effect discharging automatic valve.

Further, a discharging sampling valve is arranged on a pipeline connected with the two-effect discharging pump and the two-effect separator, and the content of crystals in the two-effect separator can be periodically sampled and analyzed through the discharging sampling valve.

Further, the condensed water negative pressure pump is further connected to the water vapor condenser, so that condensed water in the water vapor condenser is conveniently discharged through the condensed water negative pressure pump.

Further, an effective heater pressure sensor and an effective heater temperature sensor which are convenient for observing the temperature and the pressure of steam in the effective heater are arranged on the effective heater, and a double-effect heater pressure sensor and a double-effect heater temperature sensor which are convenient for observing the temperature and the pressure of steam in the double-effect heater are arranged on the double-effect heater.

The utility model has the beneficial effects that:

1. The utility model discloses a system for producing lithium dihydrogen phosphate by heat pump steam coupling low-temperature evaporative crystallization, which comprises a heat pump system of reverse Carnot cycle and an evaporative crystallization system of two-effect forced circulation. The reverse Carnot cycle heat pump system provides low-pressure steam at 70-100 ℃ and chilled water at 10-30 ℃ simultaneously, the low-pressure steam is used as a heat source of a two-effect heater in the evaporative crystallization system, the chilled water is used as a cold source of a condenser, and the Roots-water ring or screw vacuum system is adopted due to the fact that the temperature of the chilled water is low, and the evaporation at 35-50 ℃ in the second effect can be achieved under the condition of high vacuum, and lithium dihydrogen phosphate crystals are obtained through crystallization. The lithium dihydrogen phosphate obtained by the method has large and uniform particles, is convenient for subsequent solid-liquid separation and has good product quality because of crystallization while evaporation. Compared with the traditional evaporation-cooling crystallization, the method has the advantages that one cooling crystallization step is omitted, the process is simpler, and the operation is simple and convenient.

2. The system for producing the lithium dihydrogen phosphate by the heat pump steam coupling low-temperature evaporation crystallization adopts the inverse Carnot cycle heat pump negative pressure steam generation system, adopts the refrigerant to recover the heat of the condenser to generate negative pressure steam, realizes the recycling of energy, only needs 11-130kwh of electric power for evaporating one ton of water, and can save 50 percent of energy cost compared with the traditional two-effect evaporator which needs 0.6 ton of steam for evaporating one ton of water.

Additional advantages, objects, and features of the utility model will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the utility model. The objects and other advantages of the utility model may be realized and obtained by means of the instrumentalities and combinations particularly pointed out in the specification.

Drawings

For the purpose of making the objects, technical solutions and advantages of the present utility model more apparent, the present utility model will be described in the following preferred detail with reference to the accompanying drawings, in which:

FIG. 1 is a graph of lithium dihydrogen phosphate concentration versus temperature in the prior art;

FIG. 2 is a diagram of a process for preparing lithium dihydrogen phosphate by evaporation-cooling crystallization in the prior art;

FIG. 3 is a schematic diagram of a system for producing lithium dihydrogen phosphate by vapor coupling low-temperature evaporative crystallization of a heat pump according to the present utility model;

FIG. 4 is a schematic diagram of the heat pump steam system of FIG. 3;

fig. 5 is a schematic structural diagram of the evaporative crystallization system of fig. 3.

Reference numerals: the system comprises a refrigerant evaporator 1, a compressor 2, a refrigerant gas phase inlet 3, a refrigerant condenser upper pipe box 4, a refrigerant condenser 5, a refrigerant liquid phase outlet 6, a refrigerant condenser lower pipe box level gauge 7, a refrigerant condenser lower pipe box 8, a hot water circulating pump 9, a low-pressure steam outlet 10, a low-pressure steam condensate water return port 11, a pure water supplementing port 12, a first-effect automatic feed valve 13, a low-pressure steam temperature sensor 14, a low-pressure steam condensate water temperature sensor 15, a first-effect heater condensate water outlet 16, a first-effect heater condensate water outlet 17, a first-effect heater non-condensate gas outlet 17, a first-effect heater pressure sensor 18, a first-effect heater temperature sensor 19, a first-effect heater steam inlet 20, a first-effect heater 21, a first-effect separator 22, a first-effect separator level gauge 23, a second-effect heater 24, a second-effect heater pressure sensor 25, a second-effect heater temperature sensor 26, a first-effect to-second-effect automatic feed valve 27, a second-effect automatic feed pump 28, a second-effect separator 29, a second-effect heater pressure sensor 30, a positive-effect pump 32, a positive-pressure pump 32, a positive-displacement pump 40, a first-effect pump 37, a positive-to-discharge pump 32, a second-effect pump 43, a positive-pressure pump, a condensate water pump 37, a positive-to-discharge pump, a second-effect pump, a positive-feed pump, a condensate water pump, a 37, a positive-to be, a vacuum system, a negative-to be, a positive-pressure pump, a discharge system, a positive-to be, and a negative-to be, and a positive-to be.

Detailed Description

Other advantages and effects of the present utility model will become apparent to those skilled in the art from the following disclosure, which describes the embodiments of the present utility model with reference to specific examples. The utility model may be practiced or carried out in other embodiments that depart from the specific details, and the details of the present description may be modified or varied from the spirit and scope of the present utility model. It should be noted that the illustrations provided in the following embodiments merely illustrate the basic idea of the present utility model by way of illustration, and the following embodiments and features in the embodiments may be combined with each other without conflict.

Wherein the drawings are for illustrative purposes only and are shown in schematic, non-physical, and not intended to limit the utility model; for the purpose of better illustrating embodiments of the utility model, certain elements of the drawings may be omitted, enlarged or reduced and do not represent the size of the actual product; it will be appreciated by those skilled in the art that certain well-known structures in the drawings and descriptions thereof may be omitted.

The same or similar reference numbers in the drawings of embodiments of the utility model correspond to the same or similar components; in the description of the present utility model, it should be understood that, if there are terms such as "upper", "lower", "left", "right", "front", "rear", etc., that indicate an azimuth or a positional relationship based on the azimuth or the positional relationship shown in the drawings, it is only for convenience of describing the present utility model and simplifying the description, but not for indicating or suggesting that the referred device or element must have a specific azimuth, be constructed and operated in a specific azimuth, so that the terms describing the positional relationship in the drawings are merely for exemplary illustration and should not be construed as limiting the present utility model, and that the specific meaning of the above terms may be understood by those of ordinary skill in the art according to the specific circumstances.

Examples

The system for producing the lithium dihydrogen phosphate by the heat pump steam coupling low-temperature evaporative crystallization as shown in figures 3-5 comprises a heat pump steam system using inverse Carnot circulation and an evaporative crystallization system with two-effect forced circulation, wherein the heat pump steam system using inverse Carnot circulation provides negative pressure low-temperature steam with the temperature of 70-100 ℃ as a heat source of a two-effect heater in the evaporative crystallization system, and simultaneously provides chilled water with the temperature of 10-30 ℃ as a cold source of a water steam condenser 30 in the evaporative crystallization system. The heat pump steam system provides saturated negative pressure steam with the temperature of 70-100 ℃ and the absolute pressure of the steam is 30-100Kpa, and the steam is a non-pressure vessel.

The heat pump steam system comprises a refrigerant evaporator 1, a compressor 2, a refrigerant condenser 5, an expansion valve 44 and a chilled water pump 43, wherein the refrigerant evaporator 1 is connected with pipelines for refrigerant circulation, a refrigerant gas-phase inlet 3 is formed in the upper part of the refrigerant condenser 5, a refrigerant liquid-phase outlet 6 is formed in the lower part of the refrigerant condenser, the compressor 2 is connected with the refrigerant gas-phase inlet 3, the expansion valve 44 is connected with the refrigerant liquid-phase outlet 6, the refrigerant evaporator 1 is connected with a water steam condenser 30 in an evaporative crystallization system through an A/B port, the refrigerant circulation is realized, the water steam condenser 30 provides heat for the refrigerant evaporator 1, pure water is used as a heat carrier, and the heat recycling of the evaporative crystallization system is realized. Pure water continuously circulates under the action of a chilled water pump 43, enters the water vapor condenser 30 from the A port of the water vapor condenser 30, exits from the B port of the water vapor condenser 30, has an inlet-outlet temperature difference of about 5 ℃, and continuously conveys the heat of secondary steam with secondary effect in the water vapor condenser 30 to a refrigerant reverse Carnot circulation heat pump steam system.

The top of the refrigerant condenser 5 is a refrigerant condenser upper pipe box 4, the bottom of the refrigerant condenser is a refrigerant condenser lower pipe box 8, and a hot water circulating pump 9 is communicated between the refrigerant condenser upper pipe box 4 and the refrigerant condenser lower pipe box 8 to realize the water circulation in the refrigerant condenser 5.

The lower pipe box 8 of the refrigerant condenser is provided with a low-pressure steam outlet 10, a low-pressure steam condensate water return port 11 and a pure water supplementing port 12. The low-pressure steam generated by the refrigerant condenser 5 provides low-pressure steam for the two-effect evaporation system through the low-pressure steam outlet 10, the low-pressure steam condensate water return port 11 is used for refluxing condensate water condensed by the one-effect heater 21, pure water entering the refrigerant condenser 5 from the pure water supplementing port 12 is continuously circulated under the action of the hot water circulating pump 9, and heat is obtained through the refrigerant condenser 5, so that low-pressure steam is continuously generated for the two-effect evaporator.

A refrigerant condenser lower pipe box liquid level meter 7 which is convenient for observing the liquid level in the refrigerant condenser 5 is arranged on a refrigerant condenser lower pipe box 8 at the bottom of the refrigerant condenser 5.

The forced circulation evaporative crystallization system has the advantages that the forced circulation is free of a crystallizer, the forced circulation is a DTB crystallizer, and materials are crystallized while being evaporated in the forced circulation.

The evaporative crystallization system comprises a first-effect heater 21, a first-effect separator 22, a second-effect heater 24, a second-effect separator 28, a steam condenser 30 and a vacuum system 35 which are connected through pipelines, wherein the temperature and absolute pressure of the first-effect heater 21 are respectively 70-100 ℃ and 30-100Kpa, the temperature and absolute pressure of the second-effect heater 24 are respectively 50-60 ℃ and 12-20Kpa, and the temperature and absolute pressure of the steam condenser 30 are respectively 25-40 ℃ and 3-8Kpa. An effective heater steam inlet 20 communicated with the low-pressure steam outlet 10 is formed in the upper portion of the effective heater 21, an effective heater condensate water outlet 16 communicated with the low-pressure steam condensate water return port 11 is formed in the lower portion of the effective heater 21, a low-pressure steam condensate water temperature sensor 15 is installed on a connecting pipe, low-pressure steam is connected with the effective heater steam inlet 20 from the low-pressure steam outlet 10, a low-pressure steam temperature sensor 14 is installed on the connecting pipe, after heat exchange of the effective heater 21, the low-pressure steam is changed into condensate water, the effective heater 21 is discharged from the effective heater condensate water outlet 16, and the condensate water returns to the low-pressure steam condensate water return port 11. The primary heater 21 is also provided with a primary heater pressure sensor 18 and a primary heater temperature sensor 19 which facilitate the observation of the temperature and pressure of steam in the primary heater 21.

The upper part of the effective separator 22 is connected with a raw material tank 41 with a feed pump 40 through a pipeline, an effective automatic feed valve 13 is arranged on the pipeline, the top air outlet of the effective heater 21 is communicated with the effective separator 22, an effective forced circulation pump 39 communicated with the effective heater 21 and the effective separator 22 is arranged below the effective heater 21 and the effective separator 22, and the effective forced circulation pump 39 is used for pushing steam circulation in the effective heater 21 and material circulation heat exchange in the effective separator 22 to flash evaporation, so that the materials are concentrated. The first-effect separator 22 is provided with a first-effect separator liquid level meter 23 which is convenient for observing the liquid level in the first-effect separator 22, and the first-effect automatic feed valve 13 is matched with the first-effect separator liquid level meter 23 in a coordinated manner to adjust the liquid level in the first-effect separator 22 to be stable within a certain range.

The DTB crystallizer 34 or oslo crystallizer is installed in the second-effect separator 28, the secondary steam generated by the first-effect separator 22 enters the second-effect separator 28 to carry out second-effect evaporation crystallization on the material flow after the heat exchange of the second-effect heater 24, the air outlet at the top of the second-effect heater 24 is communicated to the second-effect separator 28, and the second-effect heater 24 is also provided with a second-effect heater pressure sensor 25 and a second-effect heater temperature sensor 26 which are convenient for observing the steam temperature and the pressure in the second-effect heater 24. The two-effect heater 24, be provided with the two-effect forced circulation pump 38 that all communicates with two-effect heater 24 and two-effect separator 28 below, the pipeline through taking one effect to two-effect material automatic valve 27 is led to between one effect forced circulation pump 39 and the two-effect forced circulation pump 38, the material is led to the two-effect forced circulation pump 38 entry and then is transported to two-effect separator 28 by one effect through one effect to two-effect material automatic valve 27 from one effect forced circulation pump 39 export, be provided with the two-effect separator level gauge 32 that is convenient for observe the liquid level in the two-effect separator 28 on the two-effect separator 28, one effect to two-effect material automatic valve 27 and two-effect separator level gauge 32 coordinate the cooperation, the liquid level in the two-effect separator 28 is stabilized in a certain limit of regulation. The bottom of the secondary separator 28 is connected with a secondary discharge pump 37, the middle part is connected with a solid-liquid separation system 31 with a secondary discharge automatic valve 29, after the secondary evaporation and crystallization of the material, lithium dihydrogen phosphate crystals enter a DTB crystallizer 34, part of the lithium dihydrogen phosphate crystals are recycled in the secondary inside by the secondary discharge pump 37, and the other part of the lithium dihydrogen phosphate crystals are discharged into the solid-liquid separation system 31 through the secondary discharge automatic valve 29. The pipeline that the second-effect discharge pump 37 is connected with the second-effect separator 28 is provided with a discharge sampling valve 42, and the internal crystal content of the second-effect separator 28 can be periodically sampled and analyzed through the discharge sampling valve 42.

The lower part of the secondary heater 24 is provided with a secondary heater condensate outlet communicated with the steam condenser 30, secondary steam generated by the secondary separator 28 enters the steam condenser 30 and is discharged after condensed into water, the refrigerant evaporator 1 is connected with the steam condenser 30 through a pipeline to recycle secondary steam heat, the vacuum system 35 is connected to the steam condenser 30, the vacuum system 35 adopts a Roots pump and a water ring vacuum pump or a screw vacuum pump, the absolute vacuum degree reaches 0.5-3Kpa, and the high vacuum degree of the secondary separator 28 is ensured. The water vapor condenser 30 is also connected with a condensate negative pressure pump 36, so that condensate in the water vapor condenser 30 is conveniently discharged through the condensate negative pressure pump 36.

The negative pressure steam generated by the refrigerant reverse Carnot cycle heat pump steam system requires a vacuum environment provided by the vacuum system 35 of the two-effect evaporator, and the refrigerant reverse Carnot cycle heat pump steam system is connected with the two-effect forced circulation evaporative crystallization system through the one-effect heater noncondensable gas outlet 17 and is regulated through a valve behind the outlet.

The material trend and control in the system for producing lithium dihydrogen phosphate by vapor coupling low-temperature evaporation crystallization of the heat pump are as follows: material is pumped from a feed tank 41 into the primary separator 22 by a feed pump 40, the feed inlet being above the level of primary separator stock 33. The material enters the first-effect heater 21 to exchange heat under the pushing of the first-effect forced circulation pump 39, and returns to the first-effect separator 22 to flash, so that the material is concentrated. The one-effect automatic feeding valve 13 is linked with the one-effect separator liquid level meter 23, and the liquid level in the one-effect separator is stable within a certain range through the opening/closing of the one-effect automatic feeding valve 13. The material flows from the outlet of the first-effect forced circulation pump 39 to the inlet of the second-effect forced circulation pump 38 through the first-effect to second-effect material transferring automatic valve 27, the first-effect to second-effect material transferring automatic valve 27 is linked with the liquid level meter 32 of the second-effect separator, and the liquid level in the second-effect separator is stable within a certain range through the opening/opening of the first-effect to second-effect material transferring automatic valve 27. After the material is subjected to the double-effect evaporation crystallization, the lithium dihydrogen phosphate crystal enters a DTB crystallizer 34, part of the material is recycled in the double-effect by a double-effect discharging pump 37, and the other part of the material is discharged into a solid-liquid separation system 31 through a double-effect discharging automatic valve 29. The secondary internal crystal content can be periodically sampled and analyzed by the discharge sampling valve 42. The material of the two-effect evaporation crystallization system adopts forward flow, the material enters the system from the one effect, flows into the two effects from the one effect, and then is discharged out of the system through the two-effect discharge pump 37 after being evaporated and crystallized from the two effects.

The trend of the secondary steam and the condensed water is as follows: the secondary steam generated by the primary separator 22 serves as a heat source for the secondary heater 24, and is condensed into water in the secondary heater 24 and discharged into the steam condenser 30. The secondary steam generated by the two-effect separator 28 enters a steam condenser 30 to be condensed into water. All of the condensate is discharged by condensate negative pressure pump 36. The vacuum system 35 employs a Roots pump + water ring vacuum pump or screw vacuum pump with an absolute vacuum level as high as 0.5-3Kpa, thereby ensuring that the two-way separator 28 operates at a higher vacuum level.

Finally, it is noted that the above embodiments are only for illustrating the technical solution of the present utility model and not for limiting the same, and although the present utility model has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that modifications and equivalents may be made thereto without departing from the spirit and scope of the present utility model, which is intended to be covered by the claims of the present utility model.

Claims (10)

1. The system for producing the lithium dihydrogen phosphate by the heat pump steam coupling low-temperature evaporative crystallization is characterized by comprising a heat pump steam system of reverse Carnot cycle and an evaporative crystallization system of two-effect forced circulation;

The heat pump steam system comprises a refrigerant evaporator (1), a compressor (2), a refrigerant condenser (5), a hot water circulating pump (9), an expansion valve (44) and a chilled water pump (43), wherein the refrigerant evaporator is connected with the pipelines to circulate the refrigerant, and the hot water circulating pump (9) realizes the water circulation in the refrigerant condenser (5);

The evaporative crystallization system comprises a first-effect heater (21), a first-effect separator (22), a second-effect heater (24), a second-effect separator (28), a water vapor condenser (30) and a vacuum system (35), wherein the temperature and the absolute pressure of the first-effect heater (21) are respectively 70-100 ℃ and 30-100Kpa, the temperature and the absolute pressure of the second-effect heater (24) are respectively 50-60 ℃ and 12-20Kpa, and the temperature and the absolute pressure of the water vapor condenser (30) are respectively 25-40 ℃ and 3-8Kpa; a raw material tank (41) with a feed pump (40) is connected to the first-effect separator (22), low-pressure steam generated by the refrigerant evaporator (1) enters the first-effect separator (22) to carry out first-effect flash evaporation on the material flow after heat exchange of the first-effect heater (21), and the material is concentrated; the DTB crystallizer (34) is arranged in the secondary separator (28), secondary steam generated by the primary separator (22) enters the secondary separator (28) to carry out secondary evaporation crystallization on a material flow after heat exchange of the secondary heater (24), condensed water in the secondary heater (24) is discharged into the water vapor condenser (30), secondary steam generated by the secondary separator (28) enters the water vapor condenser (30) to be discharged after being condensed into water, the refrigerant evaporator (1) is connected with the water vapor condenser (30) through a pipeline to recycle secondary steam heat, a vacuum system (35) connected with the water vapor condenser (30) adopts a Roots pump and a water ring vacuum pump or a screw vacuum pump, and the absolute vacuum degree reaches 0.5-3Kpa, so that the high vacuum degree of the secondary separator (28) is ensured.

2. The system for producing lithium dihydrogen phosphate as defined in claim 1, wherein the top of the refrigerant condenser (5) is a refrigerant condenser upper pipe box (4), the bottom of the refrigerant condenser lower pipe box (8), and the hot water circulating pump (9) is communicated between the refrigerant condenser upper pipe box (4) and the refrigerant condenser lower pipe box (8) to realize water circulation in the refrigerant condenser (5).

3. The system for producing lithium dihydrogen phosphate as defined in claim 2, wherein the refrigerant condenser (5) has a refrigerant gas phase inlet (3) formed at an upper portion thereof, a refrigerant liquid phase outlet (6) formed at a lower portion thereof, the refrigerant evaporator (1), the compressor (2), the expansion valve (44) and the chilled water pump (43) are communicated between the refrigerant gas phase inlet (3) and the refrigerant liquid phase outlet (6), and the refrigerant condenser lower pipe box (8) has a low pressure steam outlet (10), a low pressure steam condensate water return port (11) and a pure water supply port (12) formed therein.

4. A system for producing lithium dihydrogen phosphate as in claim 3, wherein an effective heater steam inlet (20) communicated with the low pressure steam outlet (10) is provided at the upper part of the effective heater (21), an effective heater condensate outlet (16) communicated with the low pressure steam condensate return port (11) is provided at the lower part of the effective heater (21), and a low pressure steam condensate temperature sensor (15) is installed on the connecting pipe, and a low pressure steam temperature sensor (14) is installed on the connecting pipe of the low pressure steam outlet (10) and the effective heater steam inlet (20).

5. A system for producing lithium dihydrogen phosphate as defined in claim 3, wherein the refrigerant condenser lower pipe box (8) is provided with a refrigerant condenser lower pipe box liquid level gauge (7), the first effect separator (22) is provided with a first effect separator liquid level gauge (23) which facilitates the observation of the liquid level in the first effect separator (22), and the second effect separator (28) is provided with a second effect separator liquid level gauge (32) which facilitates the observation of the liquid level in the second effect separator (28).

6. The system for producing lithium dihydrogen phosphate as defined in claim 5, wherein an effective automatic feed valve (13) is installed on a pipeline connected with a feed pump (40) at the upper part of the effective separator (22), an effective forced circulation pump (39) communicated with both the effective heater (21) and the effective separator (22) is arranged below the effective heater (21) and the effective separator (22), and the effective forced circulation pump (39) is used for pushing steam circulation in the effective heater (21) and material circulation heat exchange in the effective separator (22) to flash so that materials are concentrated, and the effective automatic feed valve (13) is matched with an effective separator liquid level meter (23) in a coordinated manner to regulate liquid level stabilization in the effective separator (22).

7. The system for producing lithium dihydrogen phosphate as defined in claim 6, wherein a two-effect forced circulation pump (38) communicated with both the two-effect heater (24) and the two-effect separator (28) is arranged below the two-effect heater (24) and the two-effect separator (28), a one-effect forced circulation pump (39) is communicated with the two-effect forced circulation pump (38) through a pipeline with a one-effect to two-effect automatic material transferring valve (27), materials flow from an outlet of the one-effect forced circulation pump (39) to an inlet of the two-effect forced circulation pump (38) from one-effect to two-effect automatic material transferring valve (27) to be transported to the two-effect separator (28), and the one-effect to two-effect automatic material transferring valve (27) and the two-effect separator liquid level gauge (32) are in coordination to adjust the liquid level stability in the two-effect separator (28).

8. The system for producing the lithium dihydrogen phosphate according to claim 7, wherein the bottom of the secondary separator (28) is connected with a secondary discharge pump (37), the middle part of the secondary separator is connected with a solid-liquid separation system (31) with a secondary discharge automatic valve (29), after the material is subjected to secondary evaporation crystallization, lithium dihydrogen phosphate crystals enter a DTB crystallizer (34), partial secondary internal circulation is realized by the secondary discharge pump (37), and partial secondary internal circulation is realized, and the material is discharged into the solid-liquid separation system (31) through the secondary discharge automatic valve (29).

9. The system for producing lithium dihydrogen phosphate as defined in claim 8, wherein a discharge sampling valve (42) is disposed on a pipeline connecting the secondary discharge pump (37) and the secondary separator (28), and the condensate negative pressure pump (36) is connected to the steam condenser (30).

10. The system for producing lithium dihydrogen phosphate as defined in claim 1, wherein the first effect heater (21) is provided with a first effect heater pressure sensor (18) and a first effect heater temperature sensor (19) for facilitating the observation of the temperature and pressure of steam in the first effect heater (21), and the second effect heater (24) is provided with a second effect heater pressure sensor (25) and a second effect heater temperature sensor (26) for facilitating the observation of the temperature and pressure of steam in the second effect heater (24).