CN213790049U - Forced circulation evaporation crystallization system - Google Patents

Abstract

The utility model relates to a forced circulation evaporative crystallization system, which comprises a crystallizer; the crystallizer is provided with a first material inlet, the crystallizer is communicated with the first heat exchanger and the second heat exchanger respectively, the circulating pump is communicated with the first heat exchanger and the second heat exchanger, and the crystallizer is provided with a secondary steam outlet. The utility model discloses an between the export of crystallizer and the import of circulating pump, all be equipped with the heat exchanger between the export of circulating pump and the import of crystallizer, when the handling capacity of treating the evaporation material is great, need not to increase single shell and tube heat exchanger's heat transfer area, adopt the biserial shell and tube heat exchanger to join in marriage the system scheme of a crystallizer promptly, compare in current general forced circulation evaporation crystallizer, under the handling capacity the same condition, guarantee the higher velocity of flow in the heat exchange tube of shell and tube heat exchanger, when making the crystallized salt granule can not block up the heat exchange tube, reduce half with the circulation volume of system, reduce circulating pump power, very big reduction system energy consumption, environmental protection and energy saving more.

Description

Forced circulation evaporation crystallization system

Technical Field

The utility model relates to a technical field of sewage evaporation crystallization, concretely relates to forced circulation evaporation crystallization system.

Background

The forced circulation evaporative crystallization system is a continuous crystallizer of crystal slurry circulation type, is mainly used for the evaporative crystallization of waste water zero release, salt-containing water, its work circulation path is as follows: the crystallization chamber → a heat exchanger → a circulating pump → a crystallization chamber, which circulates in turn and is finally led out by a discharge pump; steam in the crystallization chamber enters a steam compressor from a secondary steam outlet to be compressed, then enters a heat exchanger to exchange heat, and condensed water generated in the working process of the heat exchanger flows into a condensing tank from a condensed water outlet and is finally led out by a condensed water pump. The working principle of the forced circulation evaporation crystallizer for evaporation treatment of sewage is that sewage is heated substantially, a large amount of water molecules are vaporized, the crystallization principle is used for separating solid solute with crystallization performance in the sewage, the solution is supersaturated through evaporation concentration, redundant solute crystals are separated out, the crystals can be suspended and do not settle, and the crystals begin to fall into a lower conical cavity of an evaporator after fully growing. The mixture of the crystal and the mother liquid can be pumped out by a pump and sent into a settling tank for cooling crystallization, and the crystal in the mixture is separated by a centrifuge after being settled.

The existing common forced circulation evaporative crystallizer is mostly composed of a shell and tube heat exchanger, a crystallizer and a forced circulation axial-flow pump. However, when the processing amount of the material to be evaporated is large, the heat exchange area of the required tube type heat exchanger is also large, so that the total drift diameter of the tube side of the tube type heat exchanger is increased, and in order to prevent crystallized salt particles from blocking the heat exchange tube, a certain flow velocity in the tube must be maintained, so that the circulation amount of a crystallization system is inevitably increased, a large-power forced circulation axial-flow pump needs to be equipped for the system, more energy is consumed, and the energy conservation and environmental protection are not enough. Therefore, improvement is desired.

SUMMERY OF THE UTILITY MODEL

The utility model provides a forced circulation evaporation crystallization system has solved above technical problem. The utility model provides a scheme as follows of above-mentioned technical problem:

a forced circulation evaporative crystallization system comprises a crystallizer, a first heat exchanger, a second heat exchanger and a circulating pump; the crystallizer is provided with a first material inlet communicated with an external crystallization solution to be evaporated, the first heat exchanger and the second heat exchanger are both tubular heat exchangers, the crystallizer is respectively communicated with a tube side inlet of the first heat exchanger and a tube side outlet of the second heat exchanger, an inlet of the circulating pump is communicated with a tube side outlet of the first heat exchanger, an outlet of the circulating pump is communicated with a tube side inlet of the second heat exchanger, the crystallizer is provided with a secondary steam outlet for discharging steam, the crystallization solution to be evaporated circularly flows from the crystallizer, the first heat exchanger, the circulating pump, the second heat exchanger and the crystallizer in sequence under the driving action of the circulating pump, and part of water in the crystallization solution to be evaporated forms steam after the crystallization solution to be evaporated carries out twice heat exchange in the first heat exchanger and the second heat exchanger in the circulating flow process, and discharging from a secondary steam outlet on the crystallizer.

Further, the bottom of the crystallizer is provided with a sampling port for sampling a saturated crystal mixture after evaporative crystallization.

Further, the bottom of the crystallizer is provided with a lower funnel, and the lower end of the lower funnel is the extraction port.

Further, the lower end of the lower funnel is provided with a mother liquor inlet which is set to be in a normally closed state.

Further, the lower part of the crystallizer is communicated with a third circulating pipeline, the crystallizer is communicated with a tube side inlet of the first heat exchanger through the third circulating pipeline, a fourth circulating pipeline is communicated with the crystallizer, the crystallizer is communicated with a tube side outlet of the second heat exchanger through the fourth circulating pipeline, the upper end of the third circulating pipeline is an inlet of the third circulating pipeline, the upper end of the fourth circulating pipeline is an outlet of the fourth circulating pipeline, the outlet of the fourth circulating pipeline is positioned above the liquid level of the crystallization solution to be evaporated in the crystallizer, and the inlet of the third circulating pipeline is positioned below the liquid level of the crystallization solution to be evaporated in the crystallizer.

Furthermore, the evaporative crystallization system further comprises a steam compressor, the first heat exchanger shell pass is provided with a first secondary steam inlet, a first raw steam inlet and a first condensate outlet, the second heat exchanger shell pass is provided with a second secondary steam inlet, a second raw steam inlet and a second condensate outlet, the first raw steam inlet and the second raw steam inlet are communicated with a raw steam source, the secondary steam outlet is communicated with an inlet of the steam compressor, and the first secondary steam inlet and the second secondary steam inlet are communicated with an outlet of the steam compressor.

Furthermore, the first raw steam inlet and the second raw steam inlet are both communicated with raw steam inlet pipelines.

Further, a first circulating pipeline is arranged between an inlet of the circulating pump and a tube pass outlet of the first heat exchanger; and a second circulating pipeline is arranged between the outlet of the circulating pump and the tube pass inlet of the second heat exchanger, and a sewage draining outlet is arranged on the second circulating pipeline and is set to be in a normally closed state.

Furthermore, a plurality of sight glasses and a plurality of cleaning ports are arranged on the wall surface of the crystallizer; a plurality of sprayers are arranged in the top of the crystallizer, and a spraying cleaning port is formed in the upper end of each sprayer.

The utility model has the advantages that: the utility model provides a forced circulation evaporation crystal system has following advantage:

1. the heat exchangers are arranged between the feed opening of the crystallizer and the inlet of the circulating pump and between the outlet of the circulating pump and the inlet of the crystallizer, when the treatment capacity of the material to be evaporated is large, the heat exchange area of a single tubular heat exchanger does not need to be increased, namely, a system scheme that a double-row tubular heat exchanger is matched with one crystallizer is adopted, compared with the existing general forced circulation evaporation crystallizer, under the condition that the treatment capacity is the same, the high flow velocity in the heat exchange tubes of the tubular heat exchanger is ensured, on one hand, the crystallized salt particles can not block the heat exchange tubes, on the other hand, the circulation capacity of the system is reduced by half, the power of the circulating pump is reduced, the energy consumption of the system is greatly reduced, and the crystallizer is more environment-friendly and energy-saving;

2. the device has low modification cost and convenient installation, and directly modifies the device in the prior art, namely, a heat exchanger is additionally arranged between the outlet of the circulating pump and the inlet of the crystallizer.

The above description is only an overview of the technical solution of the present invention, and in order to make the technical means of the present invention clearer and can be implemented according to the content of the description, the following detailed description is made with reference to the preferred embodiments of the present invention and accompanying drawings. The detailed description of the present invention is given by the following examples and the accompanying drawings.

Drawings

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the invention without undue limitation to the invention. In the drawings:

fig. 1 is a schematic diagram of a forced circulation evaporative crystallization system according to an embodiment of the present invention;

FIG. 2 is an enlarged schematic view of a crystallizer in the forced circulation evaporative crystallization system provided in FIG. 1;

FIG. 3 is an enlarged schematic view of a first heat exchanger in the forced circulation evaporative crystallization system provided in FIG. 1;

FIG. 4 is an enlarged schematic view of a second heat exchanger in the forced circulation evaporative crystallization system provided in FIG. 1.

In the drawings, the components represented by the respective reference numerals are listed below:

100. an evaporative crystallization system; 10. a crystallizer; 11. a liquid inlet pipeline; 12. a first material inlet; 13. a secondary steam outlet; 14. a sight glass; 15. cleaning the opening; 16. a funnel is arranged below; 161. An extension tube; 1611. a mother liquor inlet; 1612. a production port; 20. a sprayer; 21. spraying a cleaning port; 30. a demister; 40. a first heat exchanger; 41. a first secondary steam inlet; 42. A first raw steam inlet; 43. a first non-condensable gas outlet; 44. a second non-condensable gas outlet; 45. A first condensate outlet; 50. a second heat exchanger; 51. a second secondary steam inlet; 52. A second raw steam inlet; 53. a third noncondensable gas outlet; 54. a fourth noncondensable gas outlet; 55. A second condensate outlet; 60. a raw steam inlet pipeline; 70. a vapor compressor; 80. a circulation pump; 90. a first circulation pipe; 91. a second material inlet; 101. a second circulation pipe; 1011. a sewage draining outlet; 102. a third circulation pipe; 1021. an inlet of a third circulation pipeline; 103. A fourth circulation pipe; 1031. and an outlet of the fourth circulating pipeline.

Detailed Description

The principles and features of the present invention are described below in conjunction with the accompanying fig. 1-4, the examples given are intended to illustrate the present invention and are not intended to limit the scope of the invention. The invention is described in more detail in the following paragraphs by way of example with reference to the accompanying drawings. The advantages and features of the present invention will become more fully apparent from the following description and appended claims. It should be noted that the drawings are in simplified form and are not to precise scale, and are provided for convenience and clarity in order to facilitate the description of the embodiments of the present invention.

It will be understood that when an element is referred to as being "secured to" another element, it can be directly on the other element or intervening elements may also be present. When a component is referred to as being "connected" to another component, it can be directly connected to the other component or intervening components may also be present. When a component is referred to as being "disposed on" another component, it can be directly on the other component or intervening components may also be present. The terms "vertical," "horizontal," "left," "right," and the like as used herein are for illustrative purposes only.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

As shown in fig. 1-4, the present invention provides a forced circulation evaporative crystallization system, wherein the evaporative crystallization system 100 comprises a crystallizer 10, a first heat exchanger 40, a second heat exchanger 50 and a circulation pump 80; the crystallizer (10) is provided with a first material inlet (12) which is used for being communicated with an external crystallization solution to be evaporated, the first heat exchanger (40) and the second heat exchanger (50) are both tubular heat exchangers, the crystallizer (10) is respectively communicated with a tube side inlet of the first heat exchanger (40) and a tube side outlet of the second heat exchanger (50), an inlet of a circulating pump (80) is communicated with a tube side outlet of the first heat exchanger (40), an outlet of the circulating pump (80) is communicated with a tube side inlet of the second heat exchanger (50), the crystallizer (10) is provided with a secondary steam outlet (13) which is used for discharging steam, and the crystallization solution to be evaporated sequentially circularly flows from the crystallizer (10), the first heat exchanger (40), the circulating pump (80), the second heat exchanger (50) and the crystallizer (10) under the driving action of the circulating pump (80), and in the circulating flow process, after the solution to be evaporated and crystallized undergoes two heat exchanges in the first heat exchanger (40) and the second heat exchanger (50), part of water in the solution to be evaporated and crystallized forms water vapor, and the water vapor is discharged from a secondary steam outlet (13) on the crystallizer (10).

Further, the bottom of the crystallizer 10 is provided with a withdrawal port 1612 for withdrawing a saturated crystal mixture after evaporative crystallization.

It should be noted that the first material inlet 12 is connected to a liquid inlet pipe 11, and the liquid inlet pipe 11 is generally used for injecting salt-containing water or waste water. The salt-containing water is taken as an example below.

And starting the circulating pump 80, enabling the salt-containing water to enter the crystallizer 10 from the liquid inlet pipeline 11, then entering the first heat exchanger 40 for first heating to generate a part of water vapor, then pumping the salt-containing water into the second heat exchanger 50 for second heating through the circulating pump 80 to generate a larger amount of water vapor, then entering the crystallizer 10 and discharging from the secondary steam outlet 13.

The embodiment provides a forced circulation evaporative crystallization system, has following advantage:

1. through arranging the heat exchangers between the outlet of the crystallizer 10 and the inlet of the circulating pump 80 and between the outlet of the circulating pump 80 and the inlet of the crystallizer 10, when the treatment capacity of the material to be evaporated is large, the heat exchange area of a single tubular heat exchanger does not need to be increased, namely, a system scheme that a double-row tubular heat exchanger is matched with one crystallizer is adopted, compared with the existing general forced circulation evaporation crystallizer, under the condition that the treatment capacity is the same, the high flow rate in the heat exchange tubes of the tubular heat exchanger is ensured, on one hand, the crystallized salt particles can not block the heat exchange tubes, on the other hand, the circulation capacity of the system is reduced by half, the power of the circulating pump 80 is reduced, the energy consumption of the system is greatly reduced, and the environment protection and energy conservation are realized;

2. the device is low in modification cost and convenient to install, and directly modifies the device in the prior art, namely a heat exchanger is additionally arranged between the outlet of the circulating pump 80 and the inlet of the crystallizer 10.

Further, the bottom of the crystallizer 10 is provided with a withdrawal opening 1612 for collecting a mixture remaining after the evaporative crystallization. The mixture is a mixed solution of crystals and mother liquor, and is convenient for the next operation through the extraction opening 1612, for example, the mixture is sent into a settling tank for cooling crystallization, and the crystals in the mixture are separated through a centrifugal machine after settling.

Further, a lower funnel 16 is disposed at the bottom of the crystallizer 10, and the lower end of the lower funnel 16 is the extraction opening 1612.

Further, an extension pipe 161 is arranged at the lower end of the lower funnel 16, a mother liquid inlet 1611 is arranged on the extension pipe 161, the mother liquid inlet 1611 is set to be in a normally closed state, and the extraction opening 1612 is arranged at the lower end of the extension pipe 161.

The mother liquor inlet 1611 is arranged on the extension pipe 161, so that the salt concentration of the mixed solution of the crystal and the mother liquor can be conveniently adjusted, and the next cooling crystallization or sedimentation separation operation can be conveniently carried out.

Further, a third circulation pipeline 102 is communicated with the lower portion of the crystallizer 10 to facilitate blanking, the crystallizer 10 is communicated with a tube side inlet of the first heat exchanger 40 through the third circulation pipeline 102, a fourth circulation pipeline 103 is communicated with the interior of the crystallizer 10, the crystallizer 10 is communicated with a tube side outlet of the second heat exchanger 50 through the fourth circulation pipeline 103, an upper end of the third circulation pipeline 102 is a third circulation pipeline inlet 1021, an upper end of the fourth circulation pipeline 103 is a fourth circulation pipeline outlet 1031, the fourth circulation pipeline outlet 1031 is located above a liquid level of a crystallization solution to be evaporated in the crystallizer 10, and the third circulation pipeline inlet 1021 is located below the liquid level of the crystallization solution to be evaporated in the crystallizer 10.

By locating the outlet 1031 of the fourth recycling conduit above the liquid level of the crystallization solution to be evaporated in the crystallizer 10, it is convenient to rapidly discharge the vapor from the top of the crystallizer 10; by locating the third circulation conduit inlet 1021 below the level of the crystallization solution to be evaporated in the crystallizer 10, the salt solution is conveniently drained by gravity.

Further, the evaporative crystallization system 100 further includes a vapor compressor 70, a first secondary vapor inlet 41, a first raw vapor inlet 42 and a first condensed water outlet 45 are arranged on the shell pass of the first heat exchanger 40, a second secondary vapor inlet 51, a second raw vapor inlet 52 and a second condensed water outlet 55 are arranged on the shell pass of the second heat exchanger 50, the first raw vapor inlet 42 and the second raw vapor inlet 52 are both used for communicating with a raw vapor source, and the first secondary vapor inlet 41 and the second secondary vapor inlet 51 are both communicated with the secondary vapor outlet 13 through the vapor compressor 70. The first secondary steam inlet 41 and the second secondary steam inlet 51 are both communicated with the outlet of the steam compressor 70. The operation method comprises the steps of firstly introducing raw steam into the first raw steam inlet 42 and the second raw steam inlet 52 for a period of time to primarily heat the heat exchangers, closing the raw steam inlet pipeline 60 when the salt solution in the crystallizer 10 volatilizes enough steam flow to keep heating, only starting the steam compressor 70, pressurizing and heating the secondary steam inlets 41 in the steam compressor 70 after entering the steam inlet of the steam compressor 70, discharging high-heat steam from the steam compressor 70 into the heat exchangers to heat the mixed solution, and discharging the high-heat steam as condensed water from condensed water outlets after cooling.

The top and the bottom of the first heat exchanger 40 are respectively provided with a first non-condensable gas outlet 43 and a second non-condensable gas outlet 44, and the top and the bottom of the second heat exchanger 50 are respectively provided with a third non-condensable gas outlet 53 and a fourth non-condensable gas outlet 54. These non-condensable gas outlets are typically arranged in a normally closed state and are opened when required.

Further, in order to facilitate smooth discharge of the steam, the secondary steam outlet 13 is located at the top of the mold 10.

Further, a raw steam inlet pipeline 60 is communicated with the first raw steam inlet 42 and the second raw steam inlet 52.

Further, a first circulation pipeline 90 is arranged between the inlet of the circulation pump 80 and the tube side outlet of the first heat exchanger 40; a second circulating pipeline 101 is arranged between the outlet of the circulating pump 80 and the tube pass inlet of the second heat exchanger 50, a sewage outlet 1011 is arranged on the second circulating pipeline 101, and the sewage outlet 1011 is set to be in a normally closed state.

The first circulation duct 90 is provided with a second material inlet 91, and the second material inlet 91 is set to a normally closed state, and is opened when it is needed to be used, so that the feeding speed can be increased.

The drain 1011 may be opened when the second circulation pipe 101 is cleaned.

Furthermore, a plurality of sight glasses 14 and a plurality of cleaning ports 15 are arranged on the wall surface of the crystallizer 10; a plurality of sprayers 20 are arranged in the top of the crystallizer 10, and a spray cleaning port 21 is arranged at the upper end of each sprayer 20, so that the crystallizer 10 can be cleaned at a later stage.

The upper part of the crystallizer 10 is provided with a foam remover 30 for removing foam from the liquid surface of the mixed solution.

The utility model discloses a concrete theory of operation and application method do:

the heat exchanger is initially heated by first introducing raw steam into the first raw steam inlet 42 and the second raw steam inlet 52 for a period of time.

And simultaneously, starting the circulating pump 80, enabling the salt-containing water to enter the crystallizer 10 from the liquid inlet pipeline 11, then enabling the salt-containing water to enter the first heat exchanger 40 through the third circulating pipeline 102 for first heating to generate a part of water vapor, then pumping the water vapor into the second heat exchanger 50 through the circulating pump 80, then enabling the salt-containing water to be heated for the second time through the fourth circulating pipeline 103 to generate a large amount of water vapor, then enabling the salt-containing water to enter the crystallizer 10 and discharging the salt-containing water from the secondary steam outlet 13.

When the salt solution in the crystallizer 10 volatilizes enough steam flow to keep heating, the raw steam inlet pipeline 60 is closed, the steam compressor 70 is only started, after each secondary steam inlet 41 enters the inlet of the steam compressor 70, pressurization and heat generation are carried out in the steam compressor 70, high-heat steam discharged from the steam compressor 70 enters each heat exchanger to heat the mixed solution, and the mixed solution is discharged as condensate water from each condensate water outlet after temperature reduction.

The utility model provides a pair of forced circulation evaporation crystallization system is for improving circulation intensity and heat transfer coefficient, forces liquid at a plurality of tubulations mesocycle of 2 heat exchangers through a circulating pump 80, makes solution homogeneous mixing to maintain favorable crystallization condition. Heating to overheat at the pressure higher than normal liquid boiling point, and after entering the separator, the pressure of the liquid is dropped rapidly to cause flash evaporation or boiling of partial liquid, the evaporated water vapor escapes from the top of the separator, and the condenser is used for condensing water to obtain pure water. Since the circulation of the liquid is maintained constantly, the flow rate and temperature in the tube can be controlled to suit the requirements of the respective product without being subject to a preselected temperature difference.

The invention provides a forced circulation evaporative crystallization system, which has the following advantages:

1. through arranging the heat exchangers between the outlet of the crystallizer 10 and the inlet of the circulating pump 80 and between the outlet of the circulating pump 80 and the inlet of the crystallizer 10, when the treatment capacity of the material to be evaporated is large, the heat exchange area of a single tubular heat exchanger does not need to be increased, namely, a system scheme that a double-row tubular heat exchanger is matched with one crystallizer is adopted, compared with the existing general forced circulation evaporation crystallizer, under the condition that the treatment capacity is the same, the high flow rate in the heat exchange tubes of the tubular heat exchanger is ensured, on one hand, the crystallized salt particles can not block the heat exchange tubes, on the other hand, the circulation capacity of the system is reduced by half, the power of the circulating pump 80 is reduced, the energy consumption of the system is greatly reduced, and the environment protection and energy conservation are realized;

2. the device is low in modification cost and convenient to install, and directly modifies the device in the prior art, namely a heat exchanger is additionally arranged between the outlet of the circulating pump 80 and the inlet of the crystallizer 10.

The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention in any way; the present invention can be smoothly implemented by those skilled in the art according to the drawings and the above description; however, those skilled in the art should understand that changes, modifications and variations made by the above-described technology can be made without departing from the scope of the present invention, and all such changes, modifications and variations are equivalent embodiments of the present invention; meanwhile, any changes, modifications, evolutions, etc. of the above embodiments, which are equivalent to the actual techniques of the present invention, still belong to the protection scope of the technical solution of the present invention.

Claims (9)

1. A forced circulation evaporative crystallization system, wherein the evaporative crystallization system (100) comprises a crystallizer (10), a first heat exchanger (40), a second heat exchanger (50) and a circulation pump (80);

the crystallizer (10) is provided with a first material inlet (12) which is used for being communicated with an external crystallization solution to be evaporated, the first heat exchanger (40) and the second heat exchanger (50) are both tubular heat exchangers, the crystallizer (10) is respectively communicated with a tube side inlet of the first heat exchanger (40) and a tube side outlet of the second heat exchanger (50), an inlet of a circulating pump (80) is communicated with a tube side outlet of the first heat exchanger (40), an outlet of the circulating pump (80) is communicated with a tube side inlet of the second heat exchanger (50), the crystallizer (10) is provided with a secondary steam outlet (13) which is used for discharging steam, and the crystallization solution to be evaporated sequentially circularly flows from the crystallizer (10), the first heat exchanger (40), the circulating pump (80), the second heat exchanger (50) and the crystallizer (10) under the driving action of the circulating pump (80), and in the circulating flow process, after the solution to be evaporated and crystallized undergoes two heat exchanges in the first heat exchanger (40) and the second heat exchanger (50), part of water in the solution to be evaporated and crystallized forms water vapor, and the water vapor is discharged from a secondary steam outlet (13) on the crystallizer (10).

2. A forced circulation evaporative crystallisation system as claimed in claim 1, wherein the bottom of the crystalliser (10) is provided with a withdrawal outlet (1612) for withdrawing a saturated crystal mixture after evaporative crystallisation.

3. A forced circulation evaporative crystallisation system as claimed in claim 2, wherein the bottom of the crystalliser (10) is provided with an underlying funnel (16), the lower end of the underlying funnel (16) being the withdrawal outlet (1612).

4. A forced circulation evaporative crystallisation system as claimed in claim 3, wherein the lower end of the down-funnel (16) is provided with a mother liquor inlet (1611), said mother liquor inlet (1611) being arranged in a normally closed position.

5. A forced circulation evaporative crystallisation system according to claim 1, wherein the lower part of the crystalliser (10) is connected to a third circulation duct (102), the crystallizer (10) is communicated with a tube side inlet of the first heat exchanger (40) through the third circulating pipeline (102), a fourth circulating pipeline (103) is communicated in the crystallizer (10), the crystallizer (10) is communicated with a tube side outlet of the second heat exchanger (50) through the fourth circulating pipeline (103), the upper end of the third circulating pipeline (102) is provided with a third circulating pipeline inlet (1021), the upper end of the fourth circulating pipeline (103) is a fourth circulating pipeline outlet (1031), the outlet (1031) of the fourth circulating pipeline is positioned above the liquid level of the crystallization solution to be evaporated in the crystallizer (10), and the inlet (1021) of the third circulating pipeline is positioned below the liquid level of the crystallization solution to be evaporated in the crystallizer (10).

6. A forced circulation evaporative crystallization system as defined in claim 3 wherein the evaporative crystallization system (100) further comprises a vapor compressor (70), the shell side of the first heat exchanger (40) is provided with a first secondary steam inlet (41), a first raw steam inlet (42) and a first condensed water outlet (45), the shell side of the second heat exchanger (50) is provided with a second secondary steam inlet (51), a second raw steam inlet (52) and a second condensed water outlet (55), the first raw steam inlet (42) and the second raw steam inlet (52) are both used for being communicated with a raw steam source, the secondary steam outlet (13) is communicated with the inlet of the steam compressor (70), the first secondary steam inlet (41) and the second secondary steam inlet (51) are both communicated with the outlet of the steam compressor (70).

7. The forced circulation evaporative crystallization system of claim 6, wherein the first raw steam inlet (42) and the second raw steam inlet (52) are both connected with a raw steam inlet pipe (60).

8. A forced circulation evaporative crystallisation system according to claim 1, wherein a first circulation conduit (90) is provided between the inlet of the circulation pump (80) and the tube-side outlet of the first heat exchanger (40); a second circulating pipeline (101) is arranged between the outlet of the circulating pump (80) and the tube pass inlet of the second heat exchanger (50), a sewage outlet (1011) is arranged on the second circulating pipeline (101), and the sewage outlet (1011) is set to be in a normally closed state.

9. A forced circulation evaporative crystallization system as defined in any one of claims 1 to 8 wherein, a plurality of sight glasses (14) and a plurality of cleaning ports (15) are provided on the wall surface of the crystallizer (10); a plurality of sprayers (20) are arranged in the top of the crystallizer (10), and a spraying cleaning port (21) is arranged at the upper end of each sprayer (20).

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