CN112358017A

CN112358017A - System and method for treating sewage by utilizing induced crystallization

Info

Publication number: CN112358017A
Application number: CN202011168128.0A
Authority: CN
Inventors: 王晓阳; 洪元堂; 谢晓朋; 周义
Original assignee: Beijing Hanqi Environment Technology Co ltd
Current assignee: Beijing Hanqi Environment Technology Co ltd
Priority date: 2020-10-27
Filing date: 2020-10-27
Publication date: 2021-02-12
Anticipated expiration: 2040-10-27
Also published as: CN112358017B

Abstract

The application relates to the technical field of sewage treatment, and particularly discloses a system and a method for treating sewage by utilizing induced crystallization. The system comprises a coagulation tank, a flocculation tank and a sedimentation separation tank which are sequentially communicated, wherein a guide cylinder is vertically arranged in the flocculation tank, and an upper lifting type axial flow stirrer is arranged in the guide cylinder; a water passing channel is arranged in the flocculation tank, the flocculation tank is communicated with the coagulation tank through the water passing channel, and the water passing channel is used for enabling the effluent at the top of the coagulation tank to enter the guide cylinder from the bottom of the guide cylinder; the water passing channel is communicated with a crystal nucleus feeding device; a backflow channel is arranged in the flocculation tank, surrounds in the circumferential direction of the guide shell and is used for enabling part of sewage coming out of the top of the guide shell to flow back to the bottom of the guide shell. The system has simple structure, is easy to control, is particularly suitable for recycling pollutants with useful value in water, and obtains recycled crystal beads with higher purity; the effluent quality of the treated sewage is good, and secondary treatment is not needed; the cost of sewage treatment is lower.

Description

System and method for treating sewage by utilizing induced crystallization

Technical Field

The application relates to the technical field of sewage treatment, in particular to a system and a method for treating sewage by utilizing induced crystallization.

Background

In the field of sewage treatment, a chemical substance is added into the wastewater, and the chemical substance reacts with some dissolved substances in the wastewater to generate insoluble salt which is then precipitated, which is called a chemical precipitation method. The formation of a precipitate in chemical precipitation is a gradual process from endless to endless and small to large, which is very complicated. The precipitate produced by the chemical precipitation process is often an amorphous precipitate formed by loosely aggregating many tiny precipitate particles, which is disorderly arranged and often contains a large amount of moisture and other impurities, so that the precipitate is a loose flocculent precipitate and the volume of the whole precipitate is large.

In order to accelerate the formation of the sediment, measures such as excessive dosing, adding treatment agents and the like are generally adopted, so that impurities are added in the sludge, the recycling value of the sediment sludge is greatly reduced, and the difficulty of sludge treatment is increased. Moreover, the sludge produced by the chemical precipitation process is often dangerous waste and needs special disposal, but the unit cost of the special disposal is high, and the water content of the waste sludge is as high as 60-80%, which further causes the large amount of the waste sludge, and further increases the disposal cost.

In order to solve the above-mentioned problems of sludge treatment, in recent years, an "induced crystallization precipitation technology" has been developed rapidly, which uses induced crystallization as a principle and combines a fluidized bed or a packed bed reactor to make substances to be removed undergo an induced crystallization reaction on seed crystals so as to be deposited on the seed crystals, and then sludge is discharged from the bottom of the seed crystals, so that the purpose of treatment is achieved, and effective recovery of some substances can be achieved. Among these, the most common is the pellet reactor, which has the ability to remove some contaminants from the wastewater that can precipitate in crystalline form.

However, the pellet reactor has the following disadvantages: the effluent treated by the pellet reactor needs to be subjected to secondary treatment by a sand filter and the like, so that the cost is too high; the pellet reactor has a large body size and high investment cost; meanwhile, in order to recycle the better pellets, the controlled reaction conditions are harsh, the process is not stable in actual operation, and the risk of unstable effluent quality exists.

Disclosure of Invention

In order to reduce sewage treatment costs, capital costs, and improve the stability of sewage treatment processes, the present application provides a system and method for treating sewage using induced crystallization.

In a first aspect, the present application provides a system for treating sewage by induced crystallization, which adopts the following technical scheme:

a system for treating sewage by utilizing induced crystallization comprises a coagulation tank, a flocculation tank and a precipitation separation tank which are sequentially communicated, wherein a guide cylinder is vertically arranged in the flocculation tank, and the inner diameter of the bottom of the guide cylinder is larger than that of the top of the guide cylinder; an upper lifting type axial flow stirrer is arranged in the guide cylinder;

a water passing channel is arranged in the flocculation tank, the flocculation tank is communicated with the coagulation tank through the water passing channel, and the water passing channel is used for enabling the effluent at the top of the coagulation tank to enter the guide cylinder from the bottom of the guide cylinder;

the water passing channel is communicated with a crystal nucleus feeding device;

and a backflow channel is arranged in the flocculation tank, surrounds the periphery of the guide shell and is used for enabling part of sewage coming out of the top of the guide shell to flow back to the bottom of the guide shell.

By adopting the technical scheme, sewage enters the coagulation tank, the treatment agent is put into the sewage, then the sewage enters the bottom of the guide shell from the water passing channel, at the moment, the induction crystal nucleus is put into the water passing channel, the treatment agent reacts with pollutants in the sewage, and the generated precipitate is wrapped on the surface of the induction crystal nucleus to form the embryonic crystal beads; and after the sewage enters the guide cylinder, adding a flocculating agent into the flocculation tank, reacting the pollutants to be removed in the sewage with the flocculating agent again, and continuously reacting on the formed rudiment crystal beads to enlarge the rudiment crystal beads. Under the action of the upper lifting type axial flow stirrer, sewage in the guide shell flows out from the top of the guide shell, and at the moment, part of sewage containing larger crystal beads enters a precipitation separation tank; and part of sewage containing the small crystal beads flows to the bottom of the guide shell along the return channel and flows into the guide shell again from the bottom of the guide shell to form internal circulation. In the cycle process than, the tiny crystal pearl is bigger and bigger, has become great crystal pearl, then along with sewage inflow sedimentation tank, great crystal pearl is as ballast in the sedimentation tank, and mud can subside very fast, realizes mud-water separation fast, and the clear water is discharged from the sludge impoundment top, and mud is discharged from sedimentation tank bottom.

The sewage that the system of this application came out can directly discharge or utilize, need not pass through secondary treatment such as sand filter, and sewage treatment's cost is lower relatively. The sediment that obtains through the system of this application is crystal form sediment, and its structure is inseparable, easily deposits to the bottom of the pool, and mud is bulky very reducing, and the moisture content of mud is low, easily recycle or final processing.

The lifting axial flow stirrer is combined with a water flow mode that the guide cylinder enters from bottom to top and flows out from top to bottom, so that a suspension effect can be generated, sewage is driven to flow upwards, the driving force can be reduced, and electric energy is saved.

The system is simple in structure, easy to control and easy to reform, and is particularly suitable for upgrading and reforming the existing sewage treatment plant. Reform transform on former sewage treatment plant's treatment tank basis and can obtain the sewage treatment system of this application, need not additionally increase the pellet reactor, can practice thrift the cost, reduce area, reduce sewage treatment's cost and degree of difficulty.

Preferably, a first retaining wall is arranged between the flocculation tank and the coagulation tank, and sewage can enter the flocculation tank from the coagulation tank by turning over the first retaining wall; a second retaining wall is arranged between the flocculation tank and the sedimentation separation tank, and sewage can enter the sedimentation separation tank from the flocculation tank by turning over the second retaining wall;

a drainage plate is vertically arranged in the flocculation tank, the drainage plate is positioned between the guide cylinder and the first retaining wall, one end of the drainage plate is fixed at the top of the flocculation tank and used for preventing sewage which turns over the first retaining wall from entering the guide cylinder from the top of the guide cylinder, a gap is reserved between the other end of the drainage plate and the bottom of the flocculation tank, and a space between the drainage plate and the first retaining wall forms the water passing channel;

the annular space that lateral wall and drainage plate, second barricade of draft tube formed does return channel.

Through adopting above-mentioned technical scheme, in this application, through reforming transform flocculation basin and flocculation basin, sedimentation tank, set up first barricade between flocculation basin and flocculation basin, set up the second barricade between flocculation basin and sedimentation tank to and set up drainage plate etc. can realize passing through laying of water passageway and backflow channel, the structure is exquisite, and easy to carry out and reform transform practices thrift sewage treatment's cost and investment cost.

Preferably, at least two supporting blocks are arranged in the return channel and used for fixing the guide cylinder between the drainage plate and the second retaining wall;

the flocculation tank is internally provided with a support rod, one end of the support rod is connected with the guide cylinder, and the other end of the support rod is connected with the bottom wall of the flocculation tank.

Through adopting above-mentioned technical scheme, the guide shell is fixed in the support that the supporting shoe can be stable support. The bracing piece is located draft tube below, and the stable operation of flocculation reactor is favorable to supporting the draft tube that can stabilize. In the system, the supporting block and the supporting rod can support the fixed guide cylinder without influencing the circulation of sewage, thereby being beneficial to improving the sewage treatment efficiency.

Preferably, the supporting block is vertically arranged, the top end of the supporting block is flush with the upper edge of the guide shell, and the length of the supporting block is smaller than the height of the guide shell;

a plurality of baffles are vertically arranged in the backflow channel along the radial direction of the guide shell, and the baffles are fixed between the outer wall of the guide shell and the inner wall of the flocculation tank;

the top end of the baffle is 30-50mm higher than the upper edge of the guide shell, and the bottom end of the baffle is positioned above the lower edge of the guide shell.

Through adopting above-mentioned technical scheme, the supporting shoe top flushes with the last edge of draft tube, avoids the supporting shoe to stop the sewage that comes out from the draft tube top and turns over the supporting shoe, is favorable to sewage circulation. The supporting blocks are vertically arranged, and sewage coming out of the top end of the guide cylinder can flow to the bottom of the guide cylinder along a channel between the adjacent supporting blocks, so that the circulating sewage can be prevented from generating vortex and rotational flow to a certain extent, and the speed of sewage circulation can be increased.

The sewage from the top of the guide shell flows to the bottom of the guide shell along the channel between the adjacent baffles, and the circulating sewage can be prevented from generating vortex and rotational flow to a certain degree, so that the sewage circulating speed can be increased. The top of the baffle is 30-50mm higher than the upper edge of the guide shell, which is beneficial to ensuring that the sewage from the top of the guide shell flows to the bottom of the guide shell uniformly, and the system can operate stably.

Preferably, a medicament adding ring is fixedly arranged in the guide cylinder at a position 200-300mm away from the bottom of the upward-lifting axial flow stirrer, a medicament adding hole is formed in the medicament adding ring, and an opening of the medicament adding hole faces downwards.

By adopting the technical scheme, the medicament feeding ring is arranged at the bottom of the upper-lifting axial flow stirrer, the earlier the medicament and sewage are mixed, the more uniform the mixing is, and the better the flocculation effect is. The dosing hole faces downwards, the water flow direction is opposite to the dosing direction, and the sewage and the medicament are fully mixed, so that better flocculation is facilitated.

Preferably, a water separator is horizontally arranged below the medicament feeding ring in the guide shell and fixedly connected with the side wall of the guide shell, wherein the water separator is circular, and the top surface of the water separator is shaped like a Chinese character 'mi'.

Through adopting above-mentioned technical scheme, the water knockout drum can be integrated the rivers of draft tube from the equidirectional not bottom and become to flow along the vertical ascending direction of draft tube, has effectively avoided phenomenons such as whirl, the vortex of sewage, can make better internal circulation of sewage. And the arrangement of the water separator can ensure that the sewage flowing into the guide shell is more balanced, thereby being beneficial to flocculation.

Preferably, the flocculation tank is rectangular or circular;

when the flocculation tank is rectangular, the ratio of the depth to the width of the flocculation tank is (2-3) to 1; the ratio (0.3-0.5) between the inner diameter of the top of the guide shell and the width of the flocculation tank is as follows: 1;

when the flocculation basin is round, the ratio of the depth to the diameter of the flocculation basin is (2-3) to 1; the ratio (0.3-0.5) of the inner diameter of the top of the guide shell to the diameter of the flocculation tank is as follows: 1;

the distance between the bottom end of the guide shell and the bottom wall of the flocculation tank is 1/3-2/3 of the inner diameter of the top of the guide shell.

Through adopting above-mentioned technical scheme, flocculation basin and draft tube design according to specific proportion satisfy specific specification, are favorable to the better circulation of sewage, also can prevent the flocculating constituent at the flocculation basin sedimentation, have improved flocculation efficiency, are favorable to the operation that the system is stable.

Preferably, a plurality of inclined pipes are obliquely arranged in the sedimentation separation tank, the inclination angle between each inclined pipe and the horizontal plane is 60-75 degrees, and the length of each inclined pipe is 0.75-1.5 m;

the inner wall of the sedimentation separation tank is provided with a water collecting tank, and the top of the water collecting tank is provided with a sawtooth-shaped overflow port.

Through adopting above-mentioned technical scheme, through being provided with pipe chute and water catch bowl, be favorable to the mud-water quickly separating in the sewage, improve sewage treatment's efficiency.

Preferably, the system for treating sewage by utilizing induced crystallization further comprises a sludge reflux pump, a hydrocyclone, a sludge tank, a crystal bead screening device and a crystal bead collecting device;

the inlet end of the sludge reflux pump is communicated with the bottom of the sedimentation and separation tank, and the outlet end of the sludge reflux pump is communicated with the hydrocyclone;

the hydraulic cyclone is communicated with the sludge tank through a sludge discharge pipe;

the inlet end of the bead screening device is communicated with the bottom end of the hydrocyclone, and the outlet end of the bead screening device is communicated with the flocculation tank;

the crystal bead collecting device is communicated with the crystal bead screening device.

By adopting the technical scheme, the sludge reflux pump directly conveys sludge (mixed liquid of sludge and crystal beads) at the bottom of the precipitation separation tank into the hydrocyclone, the hydrocyclone carries out cyclone separation on the crystal beads and the sludge, and the separated sludge can be directly discharged into the sludge tank; and the brilliant pearl after the separation is filtered through brilliant pearl sieving mechanism, and the brilliant pearl that the particle diameter is greater than 3mm is collected in brilliant pearl collection device, and other brilliant pearls can flow back the flocculation basin and regard as induced crystal nucleus once more, resources are saved and the follow-up brilliant pearl of retrieving of being convenient for.

In a second aspect, the present application provides a method for treating sewage by induced crystallization, which adopts the following technical scheme:

a method for treating sewage by using induced crystallization comprises the following steps:

feeding the pretreated sewage into a coagulation tank, adding a treatment agent into the coagulation tank, allowing the sewage to stay in the coagulation tank for 2-12min, then feeding the sewage into the bottom of a guide cylinder from a water passage, and then feeding 1000-3000mg/L induction crystal nuclei into the water passage through a crystal nucleus feeding device;

the sewage enters the guide shell, 1-5mg/L of flocculating agent is added into the flocculation tank, and under the action of the lifting axial flow stirrer, the sewage in the guide shell flows out from the top of the guide shell; at the moment, part of the sewage containing the crystal beads turns over the second retaining wall to enter the precipitation separation tank, and the rest of the sewage containing the crystal beads flows to the bottom of the guide shell along the return channel and flows into the guide shell again from the bottom of the guide shell; and the sewage entering the sedimentation separation tank realizes sludge-water separation, clear water flows out from the top of the separation tank, and sludge is discharged from the bottom of the separation tank.

By adopting the technical scheme, pretreated sewage enters a coagulation tank, a treatment agent is added into the coagulation tank for reaction for 2-12min, then the sewage enters the bottom of a draft tube from a water passage, an induction crystal nucleus is added into the water passage at the moment, the treatment agent or other agents react with pollutants in the sewage, and generated precipitate is wrapped on the surface of the induction crystal nucleus to form rudiment crystal beads; after the sewage enters the guide cylinder, adding a flocculating agent into the flocculation tank, reacting the pollutants to be removed in the sewage with the flocculating agent again, and continuously reacting on the formed rudiment crystal beads to enlarge the rudiment crystal beads; under the action of the upper lifting type axial flow stirrer, sewage in the guide shell flows out from the top of the guide shell, and at the moment, a part of sewage containing crystal beads flows into the sedimentation separation tank through the retaining wall; and the residual part of the sewage containing the crystal beads flows to the bottom of the guide shell along the return channel and flows into the guide shell again from the bottom of the guide shell. In the flocculation tank, a fluidization state of internal water flow is formed by taking the guide cylinder as the center; can ensure that immature crystal beads (crystal beads with the particle size of less than or equal to 3mm) can be circularly fluidized in the guide shell, and in the circulating fluidization process, the immature crystal beads become larger crystal beads along with the increasing fluidization state in the guide shell, and then enter the precipitation separation tank along with sewage.

The original sewage of this application at first through preliminary treatment, get rid of great impurity or suspended solid in the sewage, the preliminary treatment can for the conventional processing in sewage treatment field.

In the method, by the system, the quality of the effluent can be improved by only controlling the dosage and the dosage of the induction crystal nucleus, and the compact and high-purity crystal beads are obtained. Compared with the treatment of sewage by using a pellet reactor, the method has the advantages of simple process, less harsh treatment conditions, high treatment capacity, high treatment efficiency, easiness in control, low risk of unstable effluent quality and stable sewage treatment process.

Preferably, the sludge discharged from the bottom of the sedimentation separation tank flows back through a sludge reflux pump, and the reflux amount of the sludge reflux pump is 3-10% of the water inflow amount of the coagulation tank;

the sludge from the outlet end of the sludge reflux pump enters the hydrocyclone, is subjected to cyclone separation, is discharged into a sludge tank through a sludge discharge pipe, crystal beads are sent to the crystal bead screening device, crystal beads with the particle size larger than 3mm are sent to the crystal bead collecting device through the screening of the crystal bead screening device, and the crystal beads with the particle size smaller than or equal to 3mm flow back into the flocculation tank.

Through adopting above-mentioned technical scheme, the mud (including mud and brilliant pearl) of sedimentation separation bottom of the pool discharge is carried in hydrocyclone by the backward flow of mud backwash pump, obtain mud and brilliant pearl after hydrocyclone divides soon, at this moment, mud is discharged in the mud pond, and in the brilliant pearl was carried crystal pearl sieving mechanism, brilliant pearl sieving mechanism was screened the crystal pearl, and the qualified crystal pearl that the particle diameter is greater than 3mm sends into brilliant pearl collection device, and the unqualified crystal pearl that the particle diameter is less than or equal to 3mm flows back in the flocculation basin. In the process, qualified crystal beads are screened out and recovered. Unqualified crystal beads return to the flocculation tank and are used as an induced crystal nucleus again, the crystal nucleus is circulated in the flocculation tank, the fluidization growth is continued until the crystal beads become qualified, and the crystal beads enter the precipitation separation tank. The induction crystal nucleus can be repeatedly utilized, resources are saved, and the environment is protected.

In summary, the present application has the following beneficial effects:

1. because the method adopts the induced crystallization principle and is matched with a special flocculation tank, part of sewage containing smaller crystal beads flows to the bottom of the guide shell along the return channel and flows into the guide shell again from the bottom of the guide shell to form internal circulation, in the process of the internal circulation, the smaller crystal beads (unqualified crystal beads) become larger crystal beads (qualified crystal beads), and the larger crystal beads can be rapidly precipitated in the precipitation separation tank to obtain crystal form precipitate; compared with common precipitates, the crystal form precipitates have the advantages of small volume, low water content and compact structure, and are easy to precipitate to the bottom of the tank, so that sludge separated from the crystal form precipitates is easy to recycle or finally treat, and meanwhile, effluent of the precipitation separation tank has good water quality and does not need to be subjected to secondary treatment by a sand filter or the like, so that the cost of sewage treatment is reduced;

2. the system has simple structure, easy control and easy modification, and can be suitable for upgrading and modifying the existing sewage treatment plant without additionally adding a pellet reactor, thereby saving the investment and cost of sewage treatment;

3. the sewage treatment method has the advantages of high treatment capacity, high treatment efficiency and relatively stable treatment process;

4. the system and the method are combined, and the system and the method are particularly suitable for recycling the pollutants with useful values in water, and the purity and the yield of the obtained recycled crystal beads are high.

Drawings

FIG. 1 is a schematic structural view of the overall structure of the sewage treatment system of the present embodiment.

FIG. 2 is a cross-sectional view of the flocculation tank of the embodiment taken along the height direction of two symmetrical supporting blocks.

FIG. 3 is a cross-sectional view of the flocculation tank of the present embodiment taken along the height direction of two symmetrical baffles.

FIG. 4 is a top view of the flocculation basin of the present embodiment.

Description of the drawings: 1. a coagulation tank; 11. a sewage inlet pipe; 12. a stirrer; 13. a dosing device; 2. a flocculation tank; 21. a draft tube; 211. an overhead axial flow agitator; 212. a medicament adding ring; 213. a water separator; 22. a water passage; 221. a crystal nucleus adding device; 23. a return channel; 24. a drainage plate; 25. a fixed mount; 26. a support block; 27. a support bar; 28. a baffle plate; 3. a sedimentation separation tank; 31. a clear water outlet channel; 32. a pre-settling zone; 33. a pipe chute separation zone; 34. a water collection tank; 35. a mud scraper; 4. a sludge reflux pump; 5. a hydrocyclone; 6. a sludge tank; 7. a bead screening device; 8. a bead collection device; 9. a first retaining wall; 10. and a second retaining wall.

Detailed Description

The present application is described in further detail below with reference to figures 1-4.

A system for treating sewage by utilizing induced crystallization is shown in figure 1 and comprises a coagulation tank 1, a flocculation tank 2, a sedimentation separation tank 3, a sludge reflux pump 4, a hydrocyclone 5, a sludge tank 6, a crystal bead screening device 7 and a crystal bead collecting device 8. The coagulation tank 1, the flocculation tank 2 and the sedimentation separation tank 3 are sequentially communicated, a sewage inlet pipe 11 is arranged at the bottom end of the coagulation tank 1, and a clear water outlet channel 31 is arranged at the top of the sedimentation separation tank 3. The inlet end of the sludge reflux pump 4 is communicated with the bottom of the sedimentation and separation tank 3, and the outlet end of the sludge reflux pump 4 is communicated with the hydrocyclone 5. A sludge discharge pipe is arranged between the hydrocyclone 5 and the sludge tank 6 and is used for discharging the sludge separated by the hydrocyclone 5 into the sludge tank 6; the bottom of the hydrocyclone 5 is communicated with a crystal bead screening device 7, and crystal beads separated by the hydrocyclone 5 are conveyed into the crystal bead screening device 7. The crystal bead screening device 7 is communicated with the flocculation tank 2, a crystal bead return pipe is arranged between the crystal bead screening device 7 and the crystal bead collecting device 8, the crystal beads are screened by the crystal bead screening device 7, qualified crystal beads (the particle size is larger than 3mm) are collected in the crystal bead collecting device 8, and unqualified crystal beads (the particle size is smaller than or equal to 3mm) are returned to the flocculation tank 2 for circulation.

As shown in FIG. 1, a stirrer 12 is installed at the top of the coagulation tank 1, and the blade of the stirrer 12 is located at the center of the coagulation tank 1; the coagulation tank 1 is communicated to a drug adding device 13 for adding a treatment agent to the coagulation tank 1, and preferably, the treatment agent is added from the top of the coagulation tank 1; the agitator 12 is used to agitate the wastewater to thoroughly mix the wastewater with the administered treatment agent.

In one embodiment, the coagulation tank 1 is connected to an acid-base regulator feeding device for feeding an appropriate acid or base to the coagulation tank 1, so that the pH of the sewage in the coagulation tank 1 can be controlled. In one embodiment, an on-line pH meter is provided on the side wall of the coagulation tank 1 for real-time monitoring of the acidity or alkalinity of the wastewater in the coagulation tank 1. And controlling the type and the dosage of the acid-base regulator put in the acid-base regulator putting device according to the reading of the pH meter.

As shown in fig. 1 and 2, a draft tube 21 is vertically arranged in the flocculation tank 2, and the inner diameter of the bottom of the draft tube 21 is larger than that of the top. In this embodiment, the guide shell 21 includes a cylindrical shell and a horn ring fixedly connected to the lower end of the cylindrical shell, and the edge of the narrower end of the horn ring is integrally connected to the cylindrical shell. The flocculation tank 2 is rectangular, and the ratio of the depth to the width of the flocculation tank 2 is (2-3): 1; the ratio of the inner diameter of the cylinder to the width of the flocculation tank 2 is (0.3-0.5): 1; the distance between the edge of the wider end of the horn ring and the bottom wall of the flocculation tank 2 is 1/3-2/3 of the inner diameter of the cylinder.

In one embodiment, the flocculation basin 2 is circular, and the ratio between the depth and the diameter of the flocculation basin 2 is (2-3): 1; the ratio of the inner diameter of the cylinder to the diameter of the flocculation tank 2 is (0.3-0.5): 1; the distance between the edge of the wider end of the horn ring and the bottom wall of the flocculation tank 2 is 1/3-2/3 of the inner diameter of the cylinder.

As shown in fig. 1 and 2, a first retaining wall 9 is arranged between the flocculation tank 2 and the coagulation tank 1, and sewage can enter the flocculation tank 2 from the coagulation tank 1 by turning over the first retaining wall 9; and a second retaining wall 10 is arranged between the flocculation tank 2 and the sedimentation separation tank 3, and sewage can be turned over the second retaining wall 10 and enters the sedimentation separation tank 3 from the flocculation tank 2.

As shown in fig. 1 and 2, a drainage plate 24 is vertically arranged in the flocculation tank 2, the drainage plate 24 is located between the guide cylinder 21 and the first retaining wall 9, and one end of the drainage plate 24 is fixed at the top of the flocculation tank 2 and is used for preventing sewage which overturns the first retaining wall 9 from entering the guide cylinder 21 from the top of the guide cylinder 21; a gap is reserved between the other end of the drainage plate 24 and the bottom wall of the flocculation tank 2, a water passing channel 22 is formed in the space between the drainage plate 24 and the first retaining wall 9, and the water passing channel 22 is used for enabling the effluent at the top of the flocculation tank 1 to enter the guide cylinder 21 from the bottom of the guide cylinder 21. An annular space formed by the side wall of the guide cylinder 21, the drainage plate 24 and the second retaining wall 10 is a backflow channel 23, and the backflow channel 23 is used for enabling part of sewage coming out of the top of the guide cylinder 21 to flow back to the bottom of the guide cylinder 21. In this embodiment, a fixing frame 25 for fixing the drainage plate 24 is arranged at the top of the flocculation tank 2.

As shown in fig. 1 and 2, at least two supporting blocks 26 are disposed in the return channel 23, one end of each supporting block 26 is welded to the drainage plate 24 or the second retaining wall 10, the other end of each supporting block 26 is welded to the outer wall of the cylinder, and the supporting blocks 26 fix the guide cylinder 21 between the drainage plate 24 and the second retaining wall 10, which is favorable for stable installation of the guide cylinder 21. The supporting block 26 is vertically arranged, the length of the supporting block 26 is smaller than the height of the guide shell 21, in this embodiment, the height of the supporting block 26 is consistent with the height of the cylinder, the top end of the supporting block 26 is flush with the upper edge of the cylinder, and the bottom end of the supporting block 26 is flush with the junction of the cylinder and the horn ring. The sewage from the top of the guide shell 21 flows to the bottom of the guide shell 21 along the channel between the adjacent supporting blocks 26, so that the circulating sewage is prevented from generating vortex and rotational flow, and the sewage circulating speed is increased.

As shown in fig. 1 and 2, a support rod 27 is disposed in the flocculation tank 2, one end of the support rod 27 is fixed on the inner wall of the draft tube 21 (at the junction between the cylindrical tube and the horn ring) by a bolt, and the other end of the support rod 27 is fixedly connected to the bottom wall of the flocculation tank 2 by a bolt. The number of the supporting rods 27 can be 4-8. The support bar 27 is matched with the support block 26, and can stably fix the guide shell 21 in the flocculation tank 2. The support rod 27 is arranged at the bottom of the flocculation tank 2, and can support the guide shell 21 without influencing the sewage entering the guide shell 21.

As shown in fig. 1 and 2, an upward axial flow agitator 211 is installed in the draft tube 21, the upward axial flow agitator 211 includes an agitating shaft and an impeller fixedly connected to the agitating shaft, and the impeller extends below the center of the draft tube 21 to facilitate better mixing of the sewage. The lifting axial flow stirrer 211 can convey the sewage at the bottom of the guide shell 21 upwards, thereby being beneficial to the circulation of the sewage. The medicament adding ring 212 is arranged in the guide shell 21 at a position 200-300mm away from the bottom of the upward-lifting axial flow stirrer 211, the medicament adding ring 212 is positioned at the bottom end of the guide shell 21, the mixing time of the medicament and the sewage entering from the bottom end of the guide shell 21 is earlier, and the mixing and flocculation effects are better; the medicament feeding ring 212 is provided with a plurality of medicament feeding holes, the openings of the medicament feeding holes face downwards, the water flow direction is opposite to the medicament feeding direction, and the sewage and the medicament are fully mixed, so that better flocculation is facilitated.

As shown in fig. 1 and 2, a water separator 213 is horizontally installed in the draft tube 21 below the medicament feeding ring 212, the water separator 213 is fixedly connected with the inner side wall of the draft tube 21, the water separator 213 is circular, and the top surface of the water separator 213 is shaped like a Chinese character 'mi'. The water separator 213 integrates the sewage from the bottom of the draft tube 21 in different directions, and the sewage in different directions is changed into water flow along the vertical direction of the draft tube 21, so that the phenomena of rotational flow, vortex and the like of the sewage are effectively avoided, and the sewage can better circulate in the flocculation tank 2.

As shown in fig. 3 and 4, a plurality of baffles 28 are vertically arranged in the return channel 13 along the radial direction of the

guide shell

21, and 2 to 8 baffles 28 can be arranged, in this embodiment, 4 baffles 28 are arranged for convenience of display. The baffle 28 is fixed between the outer wall of the guide shell 21 and the inner wall of the flocculation tank 2; the top end of the baffle 28 is 30-50mm higher than the upper edge of the guide shell 21, and the bottom end is positioned above the lower edge of the guide shell 21. The sewage from the top of the guide shell 21 flows to the bottom of the guide shell 21 along the channel between the adjacent baffles 28, so that the circulating sewage is prevented from generating vortex and rotational flow, and the speed of sewage circulation is increased.

As shown in fig. 1, a pre-settling zone 32, an inclined tube separation zone 33 and a water collection tank 34 are arranged in the sedimentation separation tank 3 along the water flow direction; the water flow speed of the pre-settling area 32 is set to be 30-80 m/h; a plurality of inclined pipes are obliquely arranged in the inclined pipe separation area 33, the length of each inclined pipe is 0.75-1.5m, the inclined angle between each inclined pipe and the water surface is 60-75 degrees, and each inclined pipe is made of PE materials; the top of the water collecting tank 34 is provided with a sawtooth-shaped overflow port which is communicated with the clear water outlet channel 31. A mud scraper 35 is arranged in the sedimentation separation tank 3, so that the sludge at the bottom of the tank can be cleaned conveniently.

The sewage treatment process comprises the following steps:

sewage enters the coagulation tank 1 from the sewage inlet pipe 11, a treatment agent (the treatment agent can be aluminum salt, iron salt or an organic treatment agent, specifically calcium chloride or sodium sulfide) is added into the sewage through the dosing device 13, the sewage stays in the coagulation tank 1 for 2-12min, and then the sewage turns over the first retaining wall 9 and enters the bottom of the guide cylinder 21 from the water passage 22; at the moment, putting an induction crystal nucleus into the water channel 22 (the induction crystal nucleus is put into the water channel 22 through the crystal nucleus adding device 221 at the beginning, after the system stably operates, the induction crystal nucleus can be supplemented through the circulating crystal beads, and when the circulating amount is insufficient, a new induction crystal nucleus is added through the crystal nucleus adding device 221), at the moment, the treatment agent reacts with the pollutants in the sewage, and the generated precipitate is wrapped on the surface of the induction crystal nucleus to form a rudiment crystal bead;

after the sewage enters the guide shell 21, a flocculating agent is added through the agent adding ring 212, pollutants to be removed in the sewage react with the flocculating agent again, and the pollutants continue to react on the formed rudiment crystal beads to enlarge the rudiment crystal beads; under the action of the upper lifting type axial flow stirrer 211, the sewage in the guide shell 21 flows out from the top of the guide shell 21, and at the moment, part of the sewage containing larger crystal beads turns over the second retaining wall 10 and enters the sedimentation separation tank 3;

part of sewage containing small crystal beads flows to the bottom of the guide shell 21 along the return channel 23 and flows into the guide shell 21 again from the bottom of the guide shell 21 to form an internal circulation, in the circulation process, the small crystal beads become larger and larger crystal beads, and then the sewage flows to the precipitation separation tank 3 along with the sewage; in the sedimentation separation tank 3, the beads are used as ballast, sludge can be quickly settled, sludge-water separation is quickly realized, clear water is discharged from a clear water outlet channel, and sludge (mixed liquid of the sludge and the beads) is discharged from the bottom of the sedimentation separation tank 3.

The sludge reflux pump 4 conveys sludge (mixed liquid of sludge and crystal beads) into the hydrocyclone 5, the hydrocyclone 5 carries out cyclone separation on the sludge, and the sludge separated by the hydrocyclone 5 is directly discharged into a sludge tank 6 through a sludge discharge pipe; the crystal beads separated by the hydrocyclone 5 enter a crystal bead screening device 7; the crystal bead screening device 7 screens crystal beads, the crystal beads with the particle size larger than 3mm can be collected in the crystal bead collecting device 8, and the crystal beads with the particle size smaller than or equal to 3mm flow back to the flocculation tank 2 to be used as an induction crystal nucleus again.

The system of this application simple structure, process conditions easily controls, and play water quality of water is stable, and the system of this application goes out sewage and can directly discharge or utilize, need not carry out secondary treatment through sand filter etc. and sewage treatment's cost is lower relatively. The sediment that obtains through the system of this application is crystal form sediment, and its structure is inseparable, easily deposits the bottom of the pool, and the mud volume of discharging is less, the moisture content is low, easily recycle.

Application example 1

The fluorine-containing wastewater of a certain project has the treatment water amount of 200m³The specific treatment method is as follows:

firstly, sewage is pretreated by a high-efficiency sedimentation tank to remove a large amount of suspended matters in the water.

The pretreated sewage enters the coagulation tank 1 from the sewage inlet pipe 11, 3000mg/L calcium chloride solution and 210mg/L NaOH are added into the sewage through the dosing device 13, the mixture is fully mixed through the stirrer 12, and the sewage stays in the coagulation tank 1 for reaction for 8 min. Then, the sewage turns over the first retaining wall 9 and enters the water passage 22, and at the moment, 3000mg/L quartz sand (induction crystal nucleus) with the average grain diameter of 0.1-0.3mm is thrown in the water passage 22 through the crystal nucleus throwing device 221; the sewage flowing out of the water passage 22 enters the guide shell 21 from the bottom of the guide shell 21, and fine CaF is generated in the sewage at the moment₂The quartz sand is taken as a crystal nucleus and attached to the quartz sand to form primary prototype crystal beads.

The rudiment crystal beads enter the guide shell 21 along with the sewage, 1mg/L of flocculating agent is added through the agent adding ring 212, at the moment, the sewage in the guide shell 21 flows out from the top of the guide shell 21 under the action of the upper lifting type axial flow stirrer 211, and at the moment, a part of the sewage containing the crystal beads enters the sedimentation separation tank 3 through the second retaining wall 10; the residual part of the sewage containing the crystal beads flows to the bottom of the guide shell 21 along the return channel 23, and flows into the guide shell 21 again from the bottom of the guide shell 21, and a fluidized state of internal water flow is formed in the flocculation tank 2 by taking the guide shell 21 as the center, so that the immature crystal beads can be circularly fluidized in the guide shell 21; in the circulation process, the smaller crystal beads become larger crystal beads along with the larger fluidization state in the inner part, and then the larger crystal beads come into the sedimentation separation tank 3 along with the sewage.

The sewage entering the sedimentation separation tank 3 firstly passes through the pre-settling zone 32, the flow speed of the water passing through the pre-settling zone 32 is set to be 30m/h, then passes through the inclined tube separation zone 33, and finally flows into the clear water outlet channel 31 from the zigzag overflow port of the water collection tank 34. The sewage is separated from the mud in the sedimentation and separation tank 3, clear water flows out from the clear water outlet channel 31, and sludge is discharged from the bottom of the sedimentation and separation tank 3. The sludge at the bottom of the sedimentation separation tank 3 is conveyed into a hydrocyclone 5 by a sludge reflux pump 4 (the reflux amount of the sludge reflux pump 4 is 3 percent of the water inflow amount of a sewage inlet pipe 11), the separated sludge is conveyed into a sludge tank 6 after being separated by the hydrocyclone 5, and the separated crystal beads enter a crystal bead screening device 7; the crystal bead screening device 7 screens crystal beads, qualified crystal beads with the particle size larger than 3mm enter the crystal bead recovery device, unqualified crystal beads with the particle size smaller than or equal to 3mm return to the flocculation tank 2, and the crystal beads continue to fluidize and grow until the crystal beads become qualified crystal beads.

The crystal beads recovered in the crystal bead recovery device are calcium fluoride crystal beads, namely fluorite.

The quality of the inlet water in the sewage inlet pipe 11 and the quality of the outlet water in the clear water outlet channel 31 in application example 1 were measured, and the measurement results are shown in table 2 below.

TABLE 1 Water quality detection Table for inflow and outflow

Item	pH value	Fluoride (mg/L)	SS(mg/L)
				Inflow water	7-9	500-1000	100-200
Discharging water	7-9	8.4	15.3

The indexes of the recovered beads by detecting the beads obtained in the bead recovery apparatus are shown in table 2 below.

TABLE 2 index of recovered beads

Item	Particle size (mm)	Purity of	Yield (kg/h)
				Crystal bead	＞3	92％	324

As can be seen from the observation of tables 1 and 2: the sewage treatment system and the sewage treatment method are used for treating sewage, the sewage treatment effect is good, and the yield and the purity of the recovered crystal beads are high.

The fluoride in the effluent is 8.4mg/L, the SS is 15.3mg/L, the effluent quality of the sewage is good, and secondary treatment is not needed; the purity of the recovered crystal beads is 92%, and the yield is 324 kg/h; the yield is high, which indicates that a large amount of pollutants in the sewage are intensively attached to the surface of the crystal nucleus instead of being mixed in the sludge, so that the cost and the difficulty of sludge treatment can be effectively reduced; the high yield and purity indicate that the system and method of the present application are particularly useful for the recovery of valuable contaminants from water.

Application example 2

The phosphorus-containing wastewater of a certain project has the treatment water volume of 100m³The specific treatment method is as follows:

The pretreated sewage enters the coagulation tank 1 from the sewage inlet pipe 11, 350mg/L calcium chloride solution and 180mg/L NaOH are added into the sewage through the dosing device 13, the mixture is fully mixed through the stirrer 12, and the sewage stays in the coagulation tank 1 for reaction for 12 min. Then, the sewage turns over the first retaining wall 9 and enters the water passage 22, and at the moment, 1500mg/L quartz sand (induced crystal nucleus) with the average grain diameter of 0.1-0.3mm is thrown in the water passage 22 through the crystal nucleus throwing device 221; the sewage flowing out of the water passage 22 enters the guide shell 21 from the bottom of the guide shell 21, and fine CaF is generated in the sewage at the moment₂The quartz sand is taken as a crystal nucleus and attached to the quartz sand to form primary prototype crystal beads.

The rudiment crystal beads enter the guide shell 21 along with the sewage, 5mg/L of flocculant is added through the medicament adding ring 212, and at the moment, the sewage in the guide shell 21 flows out of the top of the guide shell 21 under the action of the upper lifting type axial flow stirrer 211; at this time, a part of the sewage containing the crystal beads turns over the second retaining wall 10 and enters the sedimentation separation tank 3; the residual part of the sewage containing the crystal beads flows to the bottom of the guide shell 21 along the return channel 23, and flows into the guide shell 21 again from the bottom of the guide shell 21, and a fluidized state of internal water flow is formed in the whole flocculation tank 2 by taking the guide shell 21 as the center, so that the immature crystal beads can be circularly fluidized in the guide shell 21; in the circulation process, the smaller crystal beads become larger crystal beads along with the larger fluidization state in the inner part, and then the larger crystal beads come into the sedimentation separation tank 3 along with the sewage.

The sewage entering the sedimentation separation tank 3 firstly passes through the pre-settling zone 32, the flow speed of the water passing through the pre-settling zone 32 is set to be 80m/h, then passes through the inclined tube separation zone 33, and finally flows into the clear water outlet channel 31 from the zigzag overflow port of the water collection tank 34. The sewage is separated from the mud in the sedimentation and separation tank 3, clear water flows out from the clear water outlet channel 31, and sludge is discharged from the bottom of the sedimentation and separation tank 3. The sludge at the bottom of the sedimentation separation tank 3 is conveyed into a hydrocyclone 5 by a sludge reflux pump 4 (the reflux quantity of the sludge reflux pump 4 is 10 percent of the water inflow quantity of a sewage inlet pipe 11), the separated sludge is conveyed into a sludge tank 6 after being separated by the hydrocyclone 5, and the separated crystal beads enter a crystal bead screening device 7; the crystal bead screening device 7 screens crystal beads, qualified crystal beads with the particle size larger than 3mm enter the crystal bead recovery device, unqualified crystal beads with the particle size smaller than or equal to 3mm return to the flocculation tank 2, and the crystal beads continue to fluidize and grow until the crystal beads become qualified crystal beads.

The quality of the inlet water in the sewage inlet pipe and the quality of the outlet water in the clear water outlet channel in application example 2 were measured, and the measurement results are shown in table 3 below.

TABLE 3 quality of inlet water and quality of outlet water detecting table

Item	pH value	Phosphate (mg/L)	SS(mg/L)
				Inflow water	7-9	150	150
Discharging water	7-9	0.35	7.9

The indexes of the recovered beads by detecting the beads obtained in the bead recovery apparatus are shown in table 4 below.

TABLE 4 index of recovered beads

Item	Particle size (mm)	Purity of	Yield (kg/h)
				Crystal bead	＞3	90％	21.5

As can be seen from the observation of tables 3 and 4: the sewage treatment system and the sewage treatment method are used for treating sewage, the sewage treatment effect is good, and the purity of the recovered crystal beads is higher.

Phosphate in the effluent is 0.35mg/L, SS is 7.9mg/L, the effluent quality of the sewage is good, and secondary treatment is not needed; the purity of the recovered crystal beads is 90 percent, and the yield is 21.5 kg/h; the pollutant in the sewage can be attached to the surface of the crystal nucleus, so that the cost and the difficulty of sludge treatment can be reduced; the high purity indicates that the system and method of the present application is particularly useful for the recovery of valuable contaminants from water.

Application example 3

The amount of treated water of a project of copper-containing wastewater is 250m³The specific treatment method is as follows:

The pretreated sewage enters the coagulation tank 1 from the sewage inlet pipe 11, 200mg/L sodium sulfide solution and 65mg/L NaOH are added into the sewage through the dosing device 13, the sewage is fully mixed through the stirrer 12, and the sewage stays in the coagulation tank 1 for reaction for 8 min. Then the sewage turns over the first retaining wall 9 and enters the water passage 22, at the moment, 1000mg/L quartz sand (induced crystal nucleus) with the average grain diameter of 0.2-0.5mm is put into the water passage 22 through the crystal nucleus adding device 221, and the generated fine CuS takes the quartz sand as the crystal nucleus and is attached to the quartz sand to form primary embryonic crystal beads.

The rudiment crystal beads enter the guide shell 21 along with the sewage, 2mg/L of flocculating agent is added through the agent adding ring 212, at the moment, under the action of the upper lifting type axial flow stirrer 211, the sewage in the guide shell 21 flows out from the top of the guide shell 21, and at the moment, a part of the sewage containing the crystal beads enters the sedimentation separation tank 3 through the second retaining wall 10; the residual part of the sewage containing the crystal beads flows to the bottom of the guide shell 21 along the return channel 23, and flows into the guide shell 21 again from the bottom of the guide shell 21, and a fluidized state of internal water flow is formed in the flocculation tank 2 by taking the guide shell 21 as the center, so that the immature crystal beads can be circularly fluidized in the guide shell 21; in the circulation process, the smaller crystal beads become larger crystal beads along with the larger fluidization state in the inner part, and then the larger crystal beads come into the sedimentation separation tank 3 along with the sewage.

The sewage entering the sedimentation separation tank 3 firstly passes through the pre-settling zone 32, the flow speed of the water passing through the pre-settling zone 32 is set to be 50m/h, then passes through the inclined tube separation zone 33, and finally flows into the clear water outlet channel 31 from the zigzag overflow port of the water collection tank 34. The sewage is separated from the mud in the sedimentation and separation tank 3, clear water flows out from the clear water outlet channel 31, and sludge is discharged from the bottom of the sedimentation and separation tank 3. The sludge at the bottom of the sedimentation separation tank 3 is conveyed into a hydrocyclone 5 by a sludge reflux pump 4 (the reflux quantity of the sludge reflux pump 4 is 6 percent of the water inflow quantity of a sewage inlet pipe 11), the separated sludge is conveyed into a sludge tank 6 after being separated by the hydrocyclone 5, and the separated crystal beads enter a crystal bead screening device 7; the crystal bead screening device 7 screens crystal beads, qualified crystal beads with the particle size larger than 3mm enter the crystal bead recovery device, unqualified crystal beads with the particle size smaller than or equal to 3mm return to the flocculation tank 2, and the crystal beads continue to fluidize and grow until the crystal beads become qualified crystal beads.

The crystal beads recovered in the crystal bead recovery device are calcium sulfide crystal beads.

The quality of the inlet water in the sewage inlet pipe and the quality of the outlet water in the clear water outlet channel in application example 3 were measured, and the measurement results are shown in table 5 below.

Table 5 water quality detecting meter for water inflow and water outflow

Item	pH value	Copper (mg/L)	SS(mg/L)
				Inflow water	7-9	150	150
Discharging water	7-9	0.3	8.3

The indexes of the recovered beads by detecting the beads obtained in the bead recovery apparatus are shown in table 6 below.

TABLE 6 index of recovered beads

Item	Particle size (mm)	Purity of	Yield (kg/h)
				Crystal bead	＞3	91.2％	56.5

As can be seen from the observation of tables 5 and 6: the sewage treatment system and the sewage treatment method are used for treating sewage, the sewage treatment effect is good, and the yield of the recovered crystal beads is higher.

The copper in the effluent is 0.3mg/L, the SS is 8.3mg/L, the effluent quality of the sewage is good, and secondary treatment is not needed;

the purity of the recovered crystal beads is 91.2%, and the yield is 56.5 kg/h; the higher yield indicates that pollutants in the sewage are more intensively attached to the surface of the crystal nucleus, so that the cost and the difficulty of sludge treatment can be reduced; the high purity indicates that the system and method of the present application is particularly useful for the recovery of valuable contaminants from water.

The present embodiment is only for explaining the present application, and it is not limited to the present application, and those skilled in the art can make modifications of the present embodiment without inventive contribution as needed after reading the present specification, but all of them are protected by patent law within the scope of the claims of the present application.

Claims

1. The utility model provides an utilize system of induced crystallization processing sewage, includes coagulation basin (1), flocculation basin (2) and sedimentation tank (3) that communicate in proper order, its characterized in that:

a guide shell (21) is vertically arranged in the flocculation tank (2), and the inner diameter of the bottom of the guide shell (21) is larger than that of the top of the guide shell; an upper lifting type axial flow stirrer (211) is arranged in the guide shell (21);

a water passing channel (22) is arranged in the flocculation tank (2), the flocculation tank (2) is communicated with the coagulation tank (1) through the water passing channel (22), and the water passing channel (22) is used for enabling outlet water at the top of the coagulation tank (1) to enter the guide cylinder (21) from the bottom of the guide cylinder (21);

the water passing channel (22) is communicated with a crystal nucleus feeding device (221);

a backflow channel (23) is arranged in the flocculation tank (2), and the backflow channel (23) surrounds the circumference of the guide shell (21) and is used for enabling part of sewage coming out of the top of the guide shell (21) to flow back to the bottom of the guide shell (21).

2. The system for treating sewage by using induced crystallization according to claim 1, wherein: a first retaining wall (9) is arranged between the flocculation tank (2) and the coagulation tank (1), and sewage can enter the flocculation tank (2) from the coagulation tank (1) by turning over the first retaining wall (9); a second retaining wall (10) is arranged between the flocculation tank (2) and the sedimentation separation tank (3), and sewage can enter the sedimentation separation tank (3) from the flocculation tank (2) by turning over the second retaining wall (10);

a drainage plate (24) is vertically arranged in the flocculation tank (2), the drainage plate (24) is positioned between the guide cylinder (21) and the first retaining wall (9), one end of the drainage plate (24) is fixed at the top of the flocculation tank (2) and used for preventing sewage turning over the first retaining wall (9) from entering the guide cylinder (21) from the top of the guide cylinder (21), and a gap is reserved between the other end of the drainage plate (24) and the bottom of the flocculation tank (2); the space between the drainage plate (24) and the first retaining wall (9) forms the water passing channel (22);

the annular space that lateral wall and drainage plate (24), second barricade (10) of draft tube (21) formed does return channel (23).

3. The system for treating sewage by using induced crystallization according to claim 2, wherein: at least two supporting blocks (26) are arranged in the return channel (23) and are used for fixing the guide cylinder (21) between the drainage plate (24) and the second retaining wall (10);

the utility model discloses a flocculation basin, be provided with in the flocculation basin (2) bracing piece (27), bracing piece (27) one end is connected with draft tube (21), and the other end is connected with flocculation basin (2) diapire.

4. The system for treating sewage by using induced crystallization according to claim 3, wherein: the supporting block (26) is vertically arranged, the top end of the supporting block (26) is flush with the upper edge of the guide shell (21), and the length of the supporting block (26) is smaller than the height of the guide shell (21);

a plurality of baffles (28) are vertically arranged in the backflow channel (23) along the radial direction of the guide shell (21), and the baffles (28) are fixed between the outer wall of the guide shell (21) and the inner wall of the flocculation tank (2);

the top end of the baffle (28) is 30-50mm higher than the upper edge of the guide shell (21), and the bottom end of the baffle is positioned above the lower edge of the guide shell (21).

5. The system for treating sewage by using induced crystallization according to claim 1, wherein: a medicament adding ring (212) is fixedly arranged in the guide cylinder (21) at a position 200-300mm away from the bottom of the upward-lifting axial flow stirrer (211), a medicament adding hole is formed in the medicament adding ring (212), and an opening of the medicament adding hole faces downwards.

6. The system for treating sewage by using induced crystallization according to claim 5, wherein: a water separator (213) is horizontally arranged below the medicament feeding ring (212) in the guide shell (21), the water separator (213) is fixedly connected with the side wall of the guide shell (21), the water separator (213) is circular, and the top surface of the water separator (213) is shaped like a Chinese character 'mi'.

7. The system for treating sewage by induced crystallization according to any one of claims 1 to 6, wherein: the flocculation tank (2) is rectangular or circular;

when the flocculation tank (2) is rectangular, the ratio of the depth to the width of the flocculation tank (2) is (2-3): 1; the ratio (0.3-0.5) between the inner diameter of the top of the guide cylinder (21) and the width of the flocculation tank (2) is as follows: 1;

when the flocculation tank (2) is round, the ratio of the depth to the diameter of the flocculation tank (2) is (2-3): 1; the ratio (0.3-0.5) between the inner diameter of the top of the guide shell (21) and the diameter of the flocculation tank (2) is as follows: 1;

the distance between the bottom end of the guide shell (21) and the bottom wall of the flocculation tank (2) is 1/3-2/3 of the inner diameter of the top of the guide shell (21).

8. The system for treating sewage by utilizing induced crystallization according to claim 1, wherein a plurality of inclined pipes are obliquely arranged in the sedimentation separation tank (3), the inclination angle between each inclined pipe and the horizontal plane is 60-75 degrees, and the length of each inclined pipe is 0.75-1.5 m;

the inner wall of the sedimentation and separation tank (3) is provided with a water collecting tank (34), and the top of the water collecting tank (34) is provided with a sawtooth-shaped overflow port.

9. The system for treating sewage using induced crystallization according to any one of claims 1 to 8, wherein: the device also comprises a sludge reflux pump (4), a hydrocyclone (5), a sludge tank (6), a crystal bead screening device (7) and a crystal bead collecting device (8);

the inlet end of the sludge reflux pump (4) is communicated with the bottom of the sedimentation separation tank (3), and the outlet end of the sludge reflux pump is communicated with the hydrocyclone (5);

the hydraulic cyclone (5) is communicated with the sludge tank (6) through a sludge discharge pipe;

the inlet end of the bead screening device (7) is communicated with the bottom end of the hydrocyclone (5), and the outlet end is communicated with the flocculation tank (2);

the crystal bead collecting device (8) is communicated with the crystal bead screening device (7).

10. A method for treating sewage using induced crystallization according to any one of claims 1 to 9, comprising: the method comprises the following steps:

the pretreated sewage enters a coagulation tank (1), a treatment agent is added into the coagulation tank (1), the sewage stays in the coagulation tank (1) for 2-12min, then the sewage enters the bottom of a guide cylinder (21) from a water passage (22), and at the moment, 1000 and 3000mg/L of induction crystal nuclei are put into the water passage (22) through a crystal nucleus adding device (221);

sewage enters the guide shell (21), 1-5mg/L of flocculating agent is added into the flocculation tank (2), and under the action of the upper lifting type axial flow stirrer (211), the sewage in the guide shell (21) flows out from the top of the guide shell (21); at the moment, part of the sewage containing the crystal beads turns over the second retaining wall (10) to enter the precipitation separation tank (3), and the rest of the sewage containing the crystal beads flows to the bottom of the guide shell (21) along the return channel (23) and flows into the guide shell (21) again from the bottom of the guide shell (21);

the sewage entering the sedimentation separation tank (3) realizes sludge-water separation, clear water flows out from the top of the separation tank (3), and sludge is discharged from the bottom of the separation tank (3).

11. The method for treating sewage using induced crystallization according to claim 10, wherein: the sludge discharged from the bottom of the sedimentation separation tank (3) flows back through a sludge reflux pump (4), and the reflux amount of the sludge reflux pump (4) is 3-10% of the water inflow of the coagulation tank (1);

the sludge discharged from the outlet end of the sludge reflux pump (4) enters the hydraulic cyclone (5), is subjected to rotary separation through the hydraulic cyclone (5), is discharged into a sludge tank (6) through a sludge discharge pipe, is sent to the crystal bead screening device (7), is screened by the crystal bead screening device (7), is sent to the crystal bead collecting device (8) by crystal beads with the particle size larger than 3mm, and is refluxed into the flocculation tank (2) by crystal beads with the particle size smaller than or equal to 3 mm.

12. The method for treating sewage using induced crystallization according to claim 10, wherein: the grain size of the induction crystal nucleus is 0.1-0.5 mm;

the induction crystal nucleus is selected from one or more of quartz sand, silver sand, ore sand, garnet and marble.