CN212282946U

CN212282946U - Equipment for producing inorganic salt with solubility changing along with temperature by utilizing cooling crystallization

Info

Publication number: CN212282946U
Application number: CN201922259973.8U
Authority: CN
Inventors: 尹博闻
Original assignee: Individual
Current assignee: Individual
Priority date: 2019-12-17
Filing date: 2019-12-17
Publication date: 2021-01-05
Anticipated expiration: 2029-12-17

Abstract

The utility model relates to an utilize equipment of cooling crystallization production solubility along with temperature variation inorganic salt, include: consecutive nucleus generates controller, first delivery pump, crystal grower, heat preservation settler, second delivery pump, centrifuge and vibration drying bed, and the nucleus generates the controller and includes: the crystal nucleus generates jar, first circulating pipe, condenser and vacuum pump, first circulating pipe one end links to each other with crystal nucleus generation jar lateral wall, the first circulating pipe other end stretches into in the jar from crystal nucleus generation tank bottom end, stretch into jar in the first circulating pipe other end be the horn mouth form, first circulating pipe one end height is greater than its other end height, the inlet pipe is equipped with at the outside first circulating pipe lower extreme of crystal nucleus generation jar, first circulating pipe sectional area is inlet pipe sectional area 3-7 times, be close to crystal nucleus generation tank bottom end and be equipped with the discharging pipe, the discharging pipe links to each other with crystal growth ware through first delivery pump, it is consecutive with condenser and vacuum pump on crystal nucleus generation tank top, crystal growth ware is including linking to each other two at least crystallizers in proper order.

Description

Equipment for producing inorganic salt with solubility changing along with temperature by utilizing cooling crystallization

Technical Field

The utility model relates to an utilize cooling crystallization step by step, control crystal nucleus earlier and generate quantity, the device that the inorganic salt crystal was produced in the growth of the control crystal again, especially utilize the device that cooling crystallization produced the inorganic salt of solubility along with the temperature variation.

Background

The general crystallization mode is divided into two kinds of evaporation concentration crystallization and cooling crystallization, the cooling crystallization is suitable for the substance with the solubility changing along with the temperature change, and many inorganic salt substances with the characteristics can be produced by the cooling crystallization method, such as sodium sulfate, magnesium sulfate heptahydrate, potassium sulfate, magnesium nitrate hexahydrate, potassium chloride and the like

The existing process for producing inorganic salt by utilizing cooling crystallization has the common problem that the supersaturation degree of a solution is too large and the condition of explosive nucleation is caused because the quantity of crystal nucleation can not be effectively controlled in the cooling process, so that crystals are difficult to grow to the required granularity due to too many crystal nuclei, and meanwhile, the distribution range of the granularity of the product is large and very uneven, so that the separation difficulty of the crystals and a mother solution is large, the amount of the entrained mother solution is high, and the purity of the dried product is influenced.

Disclosure of Invention

The utility model discloses a utility model aims at overcoming the crystal that present cooling crystallization technology often produced and too tiny and inhomogeneous shortcoming, and provide a control crystal nucleus earlier and generate quantity, the device that the inorganic salt crystal was produced in the growth of the recontrol crystal, is one kind and utilizes cooling crystallization technology, produces the inorganic salt's that the solubility is showing the change along with temperature variation device.

In order to accomplish the utility model discloses a utility model purpose, the utility model discloses a following technical scheme:

the utility model discloses an utilize equipment of cooling crystallization production solubility along with temperature variation inorganic salt, it includes: consecutive nucleus generation controller, first delivery pump, crystal grower, heat preservation settler, second delivery pump, centrifuge and vibration drying bed, wherein: the nucleus generation controller includes: the crystal nucleus generates jar, first circulating pipe, condenser and vacuum pump, the one end of first circulating pipe links to each other with the lateral wall that the crystal nucleus generated jar, the other end of first circulating pipe stretches into in the crystal nucleus generates jar from crystal nucleus generation jar bottom end, the other end that stretches into the first circulating pipe in the crystal nucleus generates jar is the horn mouth form, the height that highly is greater than its other end of one end of first circulating pipe, the inlet pipe is equipped with to first circulating pipe lower extreme outside the crystal nucleus generation jar, the sectional area of first circulating pipe is 3-7 times of inlet pipe sectional area, the discharging pipe is equipped with in the bottom that is close to the crystal nucleus generation jar, the discharging pipe links to each other with the crystal grower through first delivery pump, it links to each other in proper order with condenser and vacuum pump on crystal nucleus generation jar top, the crystal grower includes.

The utility model discloses an utilize equipment of cooling crystallization production solubility along with temperature variation inorganic salt, wherein: the crystal grower includes: the first crystallizer and the second crystallizer that link to each other in proper order, first crystallizer and second crystallizer include: the crystallizer, the heat exchanger, second circulating pipe and circulating pump, the lower extreme of crystallizer passes through the second circulating pipe and the lower extreme of circulating pump and heat exchanger links to each other, the upper end of heat exchanger passes through the second circulating pipe and links to each other with above-mentioned crystallizer upper end, it has the feed inlet to open on the second circulating pipe between circulating pump and crystallizer, the discharge tube links to each other with the feed inlet of first crystallizer through first delivery pump, the crystallizer upper end is opened there is the discharge gate, the discharge gate of first crystallizer passes through the pipeline and links to each other with the feed inlet of second crystallizer, the discharge gate of second crystallizer passes through the pipeline and links to each other with the heat preservation settler.

The utility model discloses an utilize equipment of cooling crystallization production solubility along with temperature variation inorganic salt, wherein: the crystal grower comprises a first crystallizer, a second crystallizer and a third crystallizer which are connected in sequence, wherein the first crystallizer, the second crystallizer and the third crystallizer comprise: the crystallizer, the heat exchanger, second circulating pipe and circulating pump, the lower extreme of crystallizer links to each other with the lower extreme of heat exchanger through second circulating pipe and circulating pump, the upper end of heat exchanger links to each other with the crystallizer upper end through the second circulating pipe, it has the feed inlet to open on the second circulating pipe between circulating pump and crystallizer, the discharge tube links to each other with the feed inlet of first crystallizer through first delivery pump, the crystallizer upper end is opened there is the discharge gate, the discharge gate of first crystallizer passes through the pipeline and links to each other with the feed inlet of second crystallizer, the discharge gate of second crystallizer passes through the pipeline and links to each other with the feed inlet of third crystallizer, the discharge gate of third crystallizer passes through the pipeline and links to each other with the heat preservation settler.

The utility model discloses an utilize equipment of cooling crystallization production solubility along with temperature variation inorganic salt, wherein: the crystal grower comprises a first crystallizer, a second crystallizer, a third crystallizer and a fourth crystallizer which are connected in sequence, wherein the first crystallizer, the second crystallizer, the third crystallizer and the fourth crystallizer comprise: the crystallizer comprises a crystallizing tank, a heat exchanger, a second circulating pipe and a circulating pump, wherein the lower end of the crystallizing tank is connected with the lower end of the heat exchanger through the second circulating pipe and the circulating pump, the upper end of the heat exchanger is connected with the upper end of the crystallizing tank through the second circulating pipe, a feed inlet is formed in the second circulating pipe between the circulating pump and the crystallizing tank, a discharge pipe is connected with the feed inlet of a first crystallizer through a first conveying pump, a discharge outlet is formed in the upper end of the crystallizing tank, the discharge outlet of the first crystallizer is connected with the feed inlet of a second crystallizer through a pipeline, the discharge outlet of the second crystallizer is connected with the feed inlet of a third crystallizer through a pipeline, the discharge outlet of the third crystallizer is connected with the feed inlet of a fourth crystallizer through a pipeline, and the discharge outlet of the fourth.

The utility model discloses an utilize equipment of cooling crystallization production solubility along with temperature variation inorganic salt, wherein: the upper ends and the lower ends of the first crystallizer, the second crystallizer, the third crystallizer and the fourth crystallizer are conical, the middle part of the first crystallizer, the second crystallizer, the third crystallizer and the fourth crystallizer is cylindrical, the volume of the crystallization tank ensures that the retention time of materials in the tank is 50-100 minutes, and the length-diameter ratio of the cylindrical shape is not less than 1.8: 1.

The utility model has the advantages that:

the process of crystallizing the inorganic salt from the solution is divided into two stages, nucleation and growth. The utility model has the advantages of accomplish these two stages of crystallization in the equipment of difference, control respectively to reach crystal granularity controllable, the even effect of granularity can reduce the mother liquor simultaneously and smuggle secretly, improve the purity of final product, it is big to be suitable for the production requirement granularity, the high inorganic salt product of product purity.

The crystal nucleus generator is the core of the present utility model, the process of solute precipitation from saturated solution, firstly under the power of supersaturation, the process of spontaneous nucleation, also called primary nucleation, and under the condition of crystal existing in solution, because the collision of crystal and crystal in fluid, the collision of crystal and wall of vessel, and other processes of crystal nucleus generated by some action, called secondary nucleation, the number of crystal nucleus generated by spontaneous nucleation has very strong correlation with supersaturation, and the supersaturation is too large, which can cause the mass generation of spontaneous nucleation, called burst nucleation.

The crystal nucleus generator utilizes the method of evacuation messenger saturated solution cooling, through the range of control temperature reduction to the supersaturation of control solution makes the quantity control of nucleation in certain extent, especially designed the self-circulating pipe of jar body, can make the crystal nucleus that produces earlier circulate in jar and flow the suspension, make the liquid supersaturation distribution in jar even, so fine control the crystal nucleus quantity of appearing from saturated solution, avoid the production of uncontrollable outbreak nucleation.

The utility model discloses well crystal grower's principle utilizes the method of cooling step by step, makes the supersaturation of solution release step by step, and under the condition that the crystal nucleus exists, because the promotion of supersaturation, the solute of appearing more tends to continue to grow on existing crystal nucleus more, makes it grow up, and less produces new crystal nucleus, through cooling step by step like this, the solute of newly appearing in every grade crystallizer all makes existing crystal grow gradually, produces the inorganic salt product of great granule at last.

The number of the crystallization tanks in the crystal grower is determined by comprehensively considering the intensity of the change of the solubility of the substances according to the temperature change and the initial temperature of the feed liquid.

The utility model has the characteristics that: the core of the utility model is the technological method of firstly controlling the nucleation quantity and then gradually cooling to continuously grow the crystal. The utility model discloses a heat exchanger utilizes the refrigerant heat transfer of different temperatures, makes the feed liquid lower the temperature step by step to reach inorganic salt solubility and reduce along with the temperature reduction constantly, the solute constantly appears, makes the purpose that the crystalline grain constantly grows up.

The utility model discloses in utilize the mode of heat exchanger cooling step by step, compare flash vaporization cooling method step by step and have following characteristics:

1) suitable for processing large-scale material amount (more than 40M)³H) throughput of more than 40M³The flash cooling needs a larger evaporation section, which results in large scale of equipment, especially when the vacuum degree is required to be high. And the larger the equipment is, the more difficult the crystal distribution is to be uniform, so that the crystal grain growth effect is not good. The cooling mode of the utility model can be applied to wider material processing scale, from 5M³/h--200M³The case of/h can be handled. So the method is particularly suitable for the condition of large production scale. Such as the production of inorganic salts by concentrating salt lake water, or the concentration and extraction of inorganic salts from mining wastewater. And the gradual flash cooling method is more suitable for the preparation process of small-scale fine products.

2) The final cooling temperature of the material can reach below-15 ℃. Because of utilizing the refrigerant heat transfer, the material can be as required, according to the condition of solubility, confirms ultimate cooling temperature, can reach-15 ℃ at minimum and if utilize the vacuum flash cooling, because the limit of steam jet pump, the material can only cool off about 10 ℃ at minimum usually, so this is also one of the refrigerated advantage of the utility model discloses well heat exchanger.

3) The crystallizer used for crystal growth is simple in structure, the main body of the crystallizer is cylindrical, no complex auxiliary structure is arranged in the crystallizer, and materials in the crystallizer are in a uniform suspension state under the action of power of the circulating pump, so that inorganic salt is not easy to scale in the crystallizer, and the stability of a crystallization process is easy to guarantee.

Drawings

FIG. 1 is a schematic view of an apparatus for producing inorganic salts with solubility varying with temperature by cooling crystallization according to the present invention, in which a crystal grower comprises four crystallizers;

FIG. 2 is a schematic view of another apparatus for producing inorganic salts with solubility varying with temperature by cooling crystallization according to the present invention, in which the crystal grower comprises three crystallizers;

FIG. 3 is a schematic view of another apparatus for producing inorganic salts with solubility varying with temperature by cooling crystallization according to the present invention, in which the crystal grower comprises two crystallizers.

In fig. 1 to 3, reference numeral 1 denotes a nucleus generation controller; reference numeral 2 is a condenser; reference numeral 3 is a vacuum pump; reference numeral 4 is a first circulation pipe; reference numeral 5 is a feed pipe; reference numeral 6 is a discharge pipe; reference numeral 7 is a first delivery pump; reference numeral 8 denotes a crystal grower; reference numeral 9, a crystallizer; reference numeral 10 is a centrifuge; reference numeral 11 is a vibration drying bed; reference numeral 12 is a second delivery pump; reference numeral 13 is a heat-insulating settler; reference numeral 14 is a first crystallizer; reference numeral 15 is a second circulation pipe; reference numeral 16 is a heat exchanger; reference numeral 17 is a second crystallizer; reference numeral 18 is a discharge port; reference numeral 19 is a third crystallizer; reference numeral 20 is a fourth crystallizer; reference numeral 21 is a feed port; reference numeral 22 is a circulation pump; reference numeral 23 denotes a nucleus generating pot.

Detailed Description

Example 1

As shown in figure 1, the equipment for producing inorganic salt with solubility changing along with temperature by using cooling crystallization of the utility model comprises: consecutive nucleus generation controller 1, first delivery pump 7, crystal grower 8, heat preservation settler 13, second delivery pump 12, centrifuge 10 and vibration drying bed 11, nucleus generation controller 1 includes: a crystal nucleus generating tank 23, a first circulating pipe 4, a condenser 2 and a vacuum pump 3, wherein one end of the first circulating pipe 4 is connected with the side wall of the crystal nucleus generating tank 23, the other end of the first circulating pipe 4 extends into the crystal nucleus generating tank 23 from the bottom end of the crystal nucleus generating tank 23, the other end of the first circulating pipe 4 extending into the crystal nucleus generating tank 23 is in a bell mouth shape, the height of one end of the first circulating pipe 4 is larger than that of the other end thereof, the feed pipe 5 is installed at the lower end of the first circulation pipe 4 outside the nucleus generating tank 23, the cross-sectional area of the first circulation pipe 4 is 3 to 7 times the cross-sectional area of the feed pipe 5, a discharge pipe 6 is arranged at the bottom end close to the crystal nucleus generating tank 23, the discharge pipe 6 is connected with a crystal grower 8 through a first delivery pump 7, the top end of the crystal nucleus generating tank 23 is connected with the condenser 2 and the vacuum pump 3 in sequence, and the crystal grower 8 comprises four crystallizers connected in sequence.

The crystal grower 8 includes a first crystallizer 14, a second crystallizer 17, a third crystallizer 19, and a fourth crystallizer 20 connected in sequence, and the first crystallizer 14, the second crystallizer 17, the third crystallizer 19, and the fourth crystallizer 20 include: a crystallization tank 9, a heat exchanger 16, a second circulating pipe 15 and a circulating pump 22, wherein the lower end of the crystallization tank 9 is connected with the lower end of the heat exchanger 16 through the second circulating pipe 15 and the circulating pump 22, the upper end of the heat exchanger 16 is connected with the upper end of the crystallization tank 9 through the second circulating pipe 15, a feed inlet 21 is arranged on a second circulating pipe 15 between a circulating pump 22 and the crystallizing tank 9, a discharge pipe 6 is connected with the feed inlet 21 of a first crystallizer 14 through a first conveying pump 7, a discharge outlet 18 is arranged at the upper end of the crystallizing tank 9, the discharge outlet 18 of the first crystallizer 14 is connected with the feed inlet 21 of a second crystallizer 17 through a pipeline, the discharge outlet 18 of the second crystallizer 17 is connected with the feed inlet 21 of a third crystallizer 19 through a pipeline, the discharge outlet 18 of the third crystallizer 19 is connected with the feed inlet 21 of a fourth crystallizer 20 through a pipeline, and the discharge outlet 18 of the fourth crystallizer 20 is connected with a heat-preserving settler 13 through a pipeline.

The upper ends and the lower ends of the first crystallizer 14, the second crystallizer 17, the third crystallizer 19 and the fourth crystallizer 20 are conical, the middle part is cylindrical, the volume of the crystallization tank ensures that the retention time of materials in the tank is 50-100 minutes, and the length-diameter ratio of the cylindrical shape is not less than 1.8: 1.

Example 2

Example 2 is substantially the same as example 1, and the same parts will not be described again, except that: as shown in fig. 2, the crystal grower 8 includes a first crystallizer 14, a second crystallizer 17, and a third crystallizer 19 connected in sequence, and the first crystallizer 14, the second crystallizer 17, and the third crystallizer 19 include: the device comprises a crystallizing tank 9, a heat exchanger 16, a second circulating pipe 15 and a circulating pump 22, wherein the lower end of the crystallizing tank 9 is connected with the lower end of the heat exchanger 16 through the second circulating pipe 15 and the circulating pump 22, the upper end of the heat exchanger 16 is connected with the upper end of the crystallizing tank 9 through the second circulating pipe 15, a feed inlet 21 is formed in the second circulating pipe 15 between the circulating pump 22 and the crystallizing tank 9, a discharge pipe 6 is connected with the feed inlet 21 of a first crystallizer 14 through a first conveying pump 7, a discharge outlet 18 is formed in the upper end of the crystallizing tank 9, the discharge outlet 18 of the first crystallizer 14 is connected with the feed inlet 21 of a second crystallizer 17 through a pipeline, the discharge outlet 18 of the second crystallizer 17 is connected with the feed inlet 21 of a third crystallizer 19 through a pipeline, and the discharge outlet 18 of the third crystallizer 19 is connected with a.

Example 3

Example 3 is substantially the same as example 1, and the same parts will not be described again, except that: as shown in fig. 3, the crystal grower 8 includes: a first crystallizer 14 and a second crystallizer 17 connected in series, the first crystallizer 14 and the second crystallizer 17 comprising: the device comprises a crystallization tank 9, a heat exchanger 16, a second circulating pipe 15 and a circulating pump 22, wherein the lower end of the crystallization tank 9 is connected with the lower end of the heat exchanger 16 through the second circulating pipe 15 and the circulating pump 22, the upper end of the heat exchanger 16 is connected with the upper end of the crystallization tank 9 through the second circulating pipe 15, a feed inlet 21 is formed in the second circulating pipe 15 between the circulating pump 22 and the crystallization tank 9, a discharge pipe 6 is connected with the feed inlet 21 of a first crystallizer 14 through a first conveying pump 7, a discharge outlet 18 is formed in the upper end of the crystallization tank 9, the discharge outlet 18 of the first crystallizer 14 is connected with the feed inlet 21 of a second crystallizer 17 through a pipeline, and the discharge outlet 18 of the second crystallizer 17 is connected with a heat-preservation.

The inorganic salt with the solubility changing along with the temperature is the inorganic salt with the solubility changing along with the temperature, and the inorganic salt is magnesium sulfate, potassium chloride, sodium sulfate, magnesium nitrate, potassium sulfate, magnesium sulfate heptahydrate, sodium sulfate decahydrate or magnesium nitrate hexahydrate.

The above-mentioned embodiments are only described for the preferred embodiments of the present invention, but not for limiting the scope of the air inlet of the present invention, and various modifications and improvements made by those skilled in the art without departing from the design spirit of the present invention should fall into the protection scope defined by the claims of the present invention.

Claims

1. An apparatus for producing an inorganic salt having a solubility varying with temperature by cooling crystallization, comprising: consecutive nucleus generation controller (1), first delivery pump (7), crystal grower (8), heat preservation settler (13), second delivery pump (12), centrifuge (10) and vibration drying bed (11), its characterized in that: the nucleus generation controller (1) includes: a crystal nucleus generating tank (23), a first circulating pipe (4), a condenser (2) and a vacuum pump (3), wherein one end of the first circulating pipe (4) is connected with the side wall of the crystal nucleus generating tank (23), the other end of the first circulating pipe (4) extends into the crystal nucleus generating tank (23) from the bottom end of the crystal nucleus generating tank (23), the other end of the first circulating pipe (4) extending into the crystal nucleus generating tank (23) is in a horn mouth shape, the height of one end of the first circulating pipe (4) is larger than that of the other end of the first circulating pipe, a feeding pipe (5) is arranged at the lower end of the first circulating pipe (4) outside the crystal nucleus generating tank (23), the sectional area of the first circulating pipe (4) is 3-7 times that of the feeding pipe (5), a discharging pipe (6) is arranged at the bottom end close to the crystal nucleus generating tank (23), the discharging pipe (6) is connected with a crystal grower (8) through a, the top end of the crystal nucleus generating tank (23) is sequentially connected with a condenser (2) and a vacuum pump (3), and the crystal grower (8) comprises at least two crystallizers which are sequentially connected.

2. The apparatus for producing an inorganic salt having a solubility varying with temperature according to claim 1 by cooling crystallization, wherein: the crystal grower (8) includes: a first crystallizer (14) and a second crystallizer (17) connected in series, the first crystallizer (14) and the second crystallizer (17) comprising: a crystallization tank (9), a heat exchanger (16), a second circulating pipe (15) and a circulating pump (22), wherein the lower end of the crystallization tank (9) is connected with the lower end of the heat exchanger (16) through the second circulating pipe (15) and the circulating pump (22), the upper end of the heat exchanger (16) is connected with the upper end of the crystallization tank (9) through the second circulating pipe (15), a feed inlet (21) is formed in a second circulating pipe (15) between a circulating pump (22) and a crystallizing tank (9), a discharge pipe (6) is connected with the feed inlet (21) of a first crystallizer (14) through a first conveying pump (7), a discharge outlet (18) is formed in the upper end of the crystallizing tank (9), the discharge outlet (18) of the first crystallizer (14) is connected with the feed inlet (21) of a second crystallizer (17) through a pipeline, and the discharge outlet (18) of the second crystallizer (17) is connected with a heat-preservation settler (13) through a pipeline.

3. The apparatus for producing an inorganic salt having a solubility varying with temperature according to claim 1 by cooling crystallization, wherein: the crystal grower (8) comprises a first crystallizer (14), a second crystallizer (17) and a third crystallizer (19) which are connected in sequence, wherein the first crystallizer (14), the second crystallizer (17) and the third crystallizer (19) comprise: a crystallizing tank (9), a heat exchanger (16), a second circulating pipe (15) and a circulating pump (22), wherein the lower end of the crystallizing tank (9) is connected with the lower end of the heat exchanger (16) through the second circulating pipe (15) and the circulating pump (22), the upper end of the heat exchanger (16) is connected with the upper end of the crystallizing tank (9) through the second circulating pipe (15), a feed inlet (21) is arranged on the second circulating pipe (15) between the circulating pump (22) and the crystallizing tank (9), a discharge pipe (6) is connected with the feed inlet (21) of a first crystallizer (14) through a first conveying pump (7), a discharge outlet (18) is arranged at the upper end of the crystallizing tank (9), the discharge outlet (18) of the first crystallizer (14) is connected with the feed inlet (21) of a second crystallizer (17) through a pipeline, the discharge outlet (18) of the second crystallizer (17) is connected with the feed inlet (21) of a third crystallizer (19) through a pipeline, the discharge hole (18) of the third crystallizer (19) is connected with the heat-preservation settler (13) through a pipeline.

4. The apparatus for producing an inorganic salt having a solubility varying with temperature according to claim 1 by cooling crystallization, wherein: the crystal grower (8) comprises a first crystallizer (14), a second crystallizer (17), a third crystallizer (19) and a fourth crystallizer (20) which are connected in sequence, wherein the first crystallizer (14), the second crystallizer (17), the third crystallizer (19) and the fourth crystallizer (20) comprise: a crystallizing tank (9), a heat exchanger (16), a second circulating pipe (15) and a circulating pump (22), wherein the lower end of the crystallizing tank (9) is connected with the lower end of the heat exchanger (16) through the second circulating pipe (15) and the circulating pump (22), the upper end of the heat exchanger (16) is connected with the upper end of the crystallizing tank (9) through the second circulating pipe (15), a feed inlet (21) is arranged on the second circulating pipe (15) between the circulating pump (22) and the crystallizing tank (9), a discharge pipe (6) is connected with the feed inlet (21) of a first crystallizer (14) through a first conveying pump (7), a discharge outlet (18) is arranged at the upper end of the crystallizing tank (9), the discharge outlet (18) of the first crystallizer (14) is connected with the feed inlet (21) of a second crystallizer (17) through a pipeline, the discharge outlet (18) of the second crystallizer (17) is connected with the feed inlet (21) of a third crystallizer (19) through a pipeline, the discharge port (18) of the third crystallizer (19) is connected with the feed port (21) of the fourth crystallizer (20) through a pipeline, and the discharge port (18) of the fourth crystallizer (20) is connected with the heat-preservation settler (13) through a pipeline.

5. The apparatus for producing an inorganic salt having a solubility varying with temperature by cooling crystallization as claimed in claim 2, 3 or 4, wherein: the upper ends and the lower ends of the first crystallizer (14), the second crystallizer (17), the third crystallizer (19) and the fourth crystallizer (20) are conical, the middle part is cylindrical, the volume of the crystallization tank ensures that the retention time of the materials in the tank is 50-100 minutes, and the length-diameter ratio of the cylindrical shape is not less than 1.8: 1.