CN111137930B

CN111137930B - PVA wastewater treatment and recovery system and treatment and recovery process thereof

Info

Publication number: CN111137930B
Application number: CN202010047181.9A
Authority: CN
Inventors: 陈斯哲; 刘燕萍; 张爱鹏; 林佑青; 刘振华
Original assignee: Individual
Current assignee: Individual
Priority date: 2020-01-16
Filing date: 2020-01-16
Publication date: 2022-10-11
Anticipated expiration: 2040-01-16
Also published as: CN111137930A

Abstract

The invention relates to the field of wastewater recycling and discloses a PVA wastewater treatment and recovery system and a PVA wastewater treatment and recovery process. The invention solves the problems of difficult recovery and treatment, high cost and great pollution of a large amount of PVA waste water, and large water content, poor quality and difficult reutilization of the recovered PVA.

Description

PVA wastewater treatment and recovery system and treatment and recovery process thereof

Technical Field

The invention relates to the field of wastewater recycling, in particular to a PVA wastewater treatment and recovery process and a PVA wastewater recovery process.

Background

Polyvinyl alcohol (PVA) is a water-soluble high-molecular polymer with wide application, and the performance of the PVA is between that of plastics and that of rubber. PVA is an important chemical raw material, and is used for manufacturing polyvinyl acetal, gasoline-resistant pipelines, vinylon synthetic fibers, fabric treating agents, emulsifiers, paper coatings, adhesives, glue and the like. PVA is used as sizing agent with excellent performance, the application of the sizing agent solves a plurality of problems in sizing, PVA non-woven fabrics are generally used as the layout in computer embroidery, the PVA non-woven fabrics must be cleaned after the surface embroidery is finished, and the rest workpieces are used as artware or clothes. The PVA used as a sizing agent in the textile industry of China is about 3 million tons every year, and a large amount of wastewater containing PVA and other impurities is generated. Due to the extremely low natural biodegradation rate of PVA, direct discharge causes a sharp rise in the Chemical Oxygen Demand (COD) of the water body. Even the wastewater with PVA content of only 1.5 percent has average COD of 5000-1000 mg/L, and if the wastewater is directly discharged without any treatment, the wastewater causes damage to water bodies which is difficult to repair. However, the conventional process has extremely high treatment cost for PVA wastewater and unsatisfactory effect. Moreover, the lower the concentration of PVA, the higher the treatment cost, and the difficulty in eliminating the harm of PVA waste water with huge amount and low concentration is always in the field of environmental protection. PVA itself is widely used, and if the wastewater containing PVA in large quantity is recycled, it is a good matter of both beauty.

Disclosure of Invention

The invention aims to solve the problems of difficult recovery and treatment, high cost and great pollution of a large amount of PVA wastewater at present.

Another purpose of the invention is to solve the problems of large water content, poor quality and difficult recycling of the existing recovered PVA.

In order to solve the technical problems, the invention adopts the following technical scheme:

a PVA wastewater treatment and recovery system is characterized by comprising a salting-out reaction zone, a solid-liquid separation zone, a solid crushing zone, a drying zone and a liquid medicine regeneration zone, wherein the liquid medicine regeneration zone and the solid-liquid separation zone are respectively connected with the salting-out reaction zone, the solid crushing zone is connected with the solid-liquid separation zone, and the drying zone is connected with the solid crushing zone; the salting-out reaction zone comprises a wastewater inlet, a liquid medicine inlet and a plurality of stacked reaction tanks, and each layer of each reaction tank is provided with an overflow port; the waste water inlet and the liquid medicine inlet are arranged at the top layer of the reaction tank, and the last layer of the reaction tank is connected with the solid-liquid separation zone; the solid-liquid separation zone is provided with a liquid collecting port and a solid collecting port, and the solid collecting port is connected with the solid crushing zone; the solid crushing area is provided with a second liquid collecting port and a solid powder collecting port, and the solid powder collecting port is connected with the drying area; the liquid medicine regeneration area comprises a liquid medicine recovery tank and a liquid medicine regeneration tank, and the liquid medicine recovery tank is connected with the liquid medicine regeneration tank through a pipeline; the liquid medicine recovery tank is connected with the liquid collecting port and the second liquid collecting port, and the liquid medicine regeneration tank is connected with the liquid medicine inlet.

Preferably, the top of the reaction tank is provided with a booster plate, and the booster plate is far away from the wastewater inlet and the liquid medicine inlet; the boosting plate is a plate frame and is arranged on a conveying belt, and the boosting plate moves in the reaction tank through the conveying belt.

Preferably, the solid-liquid separation zone comprises a screw extruder, and the solid collecting port is arranged at the extrusion end of the screw extruder; the bottom of the screw extruder is provided with a liquid recovery hole which is communicated with the liquid collecting port.

Preferably, the screw extruder is a twin screw extruder.

Preferably, the solid crushing area comprises a screw cylinder, a screw rod, an extrusion head and a rotary driving device, the screw rod is rotatably arranged in the screw cylinder, the extrusion head is fixedly connected with the opening end of the screw cylinder, and the end part of the screw rod extends outwards and is fixedly connected with the rotary driving device; the screw comprises a conveying section, a grinding section and an extrusion section, the conveying section, the grinding section and the extrusion section are sequentially arranged along the extrusion direction, the inner wall of the screw barrel is circumferentially provided with a shearing part matched with the grinding section of the screw for shearing and grinding, and the side wall of the bottom of the screw barrel is provided with a plurality of inclined micropores along the extrusion direction; a feeding hole is formed in the side wall of the top of the screw, which is adjacent to the conveying section of the screw, the center of the extrusion head is provided with the solid powder collecting hole, the inner wall of the extrusion head is circumferentially provided with a plurality of flow guide grooves, and the rotary driving device drives the screw to rotate to grind and crush the solid; the inclined micropores are communicated with the second liquid collecting port.

Preferably, the pitch of said conveying section is greater than the pitch of said grinding section; the cross section of the screw cylinder is gradually increased along the extrusion direction; the cross section of the extrusion head is in a truncated cone shape, and a plurality of second inclined micro-holes are formed in the flow guide groove at the bottom of the extrusion head; the second inclined micropores are communicated with the second liquid collecting port.

A treatment and recovery process of the PVA wastewater treatment and recovery system comprises the following steps:

A. PVA waste water enters the salting-out reaction zone through the waste water inlet, and simultaneously salting-out liquid enters the salting-out reaction zone through the liquid medicine inlet to form mixed liquid, and the mixed liquid starts to contact and react in the top layer of the reaction tank to separate out PVA solid;

B. the mixed solution flows through the reaction tanks of each layer through the overflow ports until the reaction is completed;

C. the mixed liquid and the PVA solid enter the solid-liquid separation zone at the last layer of the reaction tank, the mixed liquid is separated from the PVA solid, the mixed liquid enters the liquid medicine regeneration zone through the liquid collection port after being separated, and the PVA solid enters the solid crushing zone through the solid collection port after being separated;

D. the solid crushing area crushes and extrudes the PVA solid, the mixed liquid wrapped in the PVA solid is discharged, PVA powder is obtained, the mixed liquid enters the liquid medicine regeneration area through the second liquid collecting opening after being discharged, and the PVA powder enters the drying area through the solid powder collecting opening;

E. drying the PVA powder in the drying area to obtain a PVA recovery product;

F. and B, after the mixed solution enters the liquid medicine regeneration area, the mixed solution is firstly collected in the liquid medicine recovery tank, then enters the liquid medicine regeneration tank through a pipeline for concentration and regeneration, and then returns to the step A for replacing part of the salting-out solution for recycling through the liquid medicine inlet.

It can be seen that the steps D and F are respectively independent steps, which can be performed simultaneously in the actual operation process, so as to ensure the timely regeneration cycle of the salting-out solution and the integrity of the process.

Preferably, in the step a, the salting-out solution is brought into contact with the PVA wastewater to react for 30 seconds, and then the mixed solution is assisted to flow.

Preferably, in the step a, the salting-out solution is a mixed solution of mirabilite, caustic soda and sulfuric acid.

Preferably, in step F, there are a plurality of the chemical solution regeneration tanks, and the concentrating and regenerating operations are: evaporating excess water from the mixed liquor; and (3) after the mixed solution is regenerated, returning to the step (A) to replace 80-90% of the salting-out solution for recycling.

The implementation of the invention has the following beneficial effects:

the invention adopts a multilayer structure design to recycle PVA wastewater, skillfully combines the characteristic that the reaction of the PVA wastewater and the salting-out solution changes along with time, efficiently treats the PVA wastewater, can effectively extract and treat PVA in the wastewater for recycling, can recycle the salting-out solution, and greatly reduces the treatment cost of the PVA wastewater. The inner wall of the screw cylinder is provided with a shearing part which is matched with the screw rod for extrusion grinding, and the shearing part is pushed by the screw rod and crushed into powder, so that a PVA molecular film is damaged, and moisture wrapped in the PVA molecular film is released, and the aim of obtaining a PVA recovery product with low water content is fulfilled. The separated water or dirt flows out from the inclined micropores to achieve the cleaning effect, and the ground PVA powder is squeezed and recovered from the extrusion head, so that the reuse of waste water is realized, and the waste of resources is prevented.

Drawings

FIG. 1 is a schematic view of the overall structure of the present invention;

FIG. 2 is a schematic view of a portion of the present invention;

FIG. 3 is an enlarged view of a portion of the structure of the present invention;

FIG. 4 is an enlarged view of the booster plate of the present invention;

FIG. 5 is an enlarged view of the structure of the solid pulverizing section of the present invention;

FIG. 6 is an enlarged view of the structure of the screw for the solid pulverizing section of the present invention;

FIG. 7 is an enlarged view of the interior of the barrel in the solid pulverizing region of the present invention;

FIG. 8 is an enlarged view of the interior of the extrusion head of the solid pulverizing area of the present invention;

wherein, salting-out reaction zone 1, waste water inlet 101, liquid medicine inlet 102, reaction tank 103, overflow port 1031, boosting plate 1032, conveyor belt 1033, solid-liquid separation zone 2, liquid collection port 201, solid collection port 202, screw extruder 203, liquid recovery hole 2031, solid crushing zone 3, screw barrel 301, shearing part 3011, inclined micro-hole 3012, feed port 3013, screw 302, conveying section 3021, grinding section 3022, extrusion section 3023, extrusion head 303, solid powder collection port 3031, diversion groove 3032, second inclined micro-hole 3033, rotary driving device 304, second liquid collection port 305, drying zone 4, liquid medicine regeneration zone 5, liquid medicine recovery groove 501 and liquid medicine regeneration tank 502.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail with reference to the accompanying drawings.

Example 1

As shown in figures 1 to 7, the invention is a PVA wastewater treatment and recovery system, which comprises a salting-out reaction zone 1, a solid-liquid separation zone 2, a solid crushing zone 3, a drying zone 4 and a liquid medicine regeneration zone 5, wherein the liquid medicine regeneration zone 5 and the solid-liquid separation zone 2 are respectively connected with the salting-out reaction zone 1, the solid crushing zone 3 is connected with the solid-liquid separation zone 2, and the drying zone 4 is connected with the solid crushing zone 3. The salting-out reaction zone 1 comprises a wastewater inlet 101, a liquid medicine inlet 102 and a reaction tank 103 stacked in multiple layers, each layer of the reaction tank 103 is provided with an overflow port 1031, the top of the reaction tank 103 is provided with a boosting plate 1032, and the boosting plate 1032 is far away from the wastewater inlet 101 and the liquid medicine inlet 102. The power assisting plate 1032 is a plate frame, is provided on the conveyor 1033, and moves in the reaction tank 103 by the conveyor 1032. The waste water inlet 101 is arranged at the top layer of the reaction tank 103. The last layer of the reaction tank 103 is connected with a solid-liquid separation zone 2.

The solid-liquid separation device 2 is provided with a liquid collecting port 201 and a solid collecting port 202, and further comprises a screw extruder 203, wherein the solid collecting port 202 is arranged at the extrusion end of the screw extruder 203. The bottom of the screw extruder 203 is provided with a liquid recovery hole 2031, and the liquid recovery hole 2031 is communicated with the liquid collection port 201. The solids collection port 202 is connected to the solids comminution zone 3.

The solid crushing area 3 comprises a screw barrel 301, a screw 302, an extrusion head 303 and a rotary driving device 304, wherein the screw 302 is rotatably arranged in the screw barrel 301, the extrusion head 303 is fixedly connected with the opening end of the screw barrel 301, and the end part of the screw 302 extends outwards and is fixedly connected with the rotary driving device 304. The screw 302 comprises a conveying section 3021, a grinding section 3022 and an extrusion section 3023, wherein the conveying section 3021, the grinding section 3022 and the extrusion section 3023 are sequentially arranged along the extrusion direction, the screw pitch of the conveying section 3021 is greater than that of the grinding section 3022, and the cross section of the screw barrel 301 is gradually increased along the extrusion direction. The inner wall of the screw barrel 301 is circumferentially provided with a shearing part 3011 which is matched with the grinding section 3022 of the screw 302 for shearing and grinding, the side wall of the bottom of the screw barrel 301 is distributed along the extrusion direction and provided with a plurality of inclined micropores 3012, and the side wall of the top of the screw 302 is adjacent to the conveying section 3021 of the screw 302 and is provided with a feeding port 3013. The center of the extrusion head 303 is provided with a solid powder collecting port 3031, the cross section of the extrusion head 303 is in a cone shape, the inner wall of the extrusion head 303 is circumferentially provided with a plurality of flow guide grooves 3032, and the flow guide grooves 3032 at the bottom of the extrusion head are provided with a plurality of second inclined micropores 3033. The PVA solid is grinded and crushed by the rotation of the screw 302 driven by the rotary driving device 304, and the solid powder collecting port 3031 is connected with the drying area 4. The inclined micropores 3012 and the second inclined micropores 3033 communicate with the second liquid collecting port 305.

The drying zone 4 can dry the PVA powder by any conventional drying means to obtain a PVA recovery product.

The liquid medicine regeneration area 5 comprises a liquid medicine recovery tank 501 and a liquid medicine regeneration tank 502, and the liquid medicine recovery tank 501 can be stacked under the bottom of the last layer of the reaction tank 103 to save space and can also be arranged separately. The liquid medicine recovery tank 501 is connected with the liquid medicine regeneration tank 502 through a pipeline; the liquid medicine recovery tank 501 is connected with the liquid collection port 201 and the second liquid collection port 305, and the liquid medicine regeneration tank 502 is connected with the liquid medicine inlet 102.

In general, the PVA content in industrial PVA waste water, especially PVA waste water produced in the computer embroidery industry, is about 5%, because the PVA content in water reaches 5%, which is difficult to use in industrial production and can only be discharged in the form of waste water. The PVA content is 5 percent, and the PVA is discharged and then enters the treatment and recovery system of the invention for treatment, and the treatment process comprises the following steps:

A. PVA waste water enters the salting-out reaction area 1 through a waste water inlet 102, and simultaneously salting-out liquid enters through a liquid medicine inlet 101 to form mixed liquid, the mixed liquid starts to contact and react in the top layer of the reaction tank 103, and PVA components in the waste water are separated out in a solid form to form PVA solid. After the salting-out solution is contacted with PVA to react for 30s, the boosting plate 1032 starts to boost the mixed solution with the help of the conveyor belt 1033 to assist the flow of the mixed solution.

The flow of the reaction solution can be efficiently promoted by the aid of the assisting plate 1032, but the reaction is in an initial state immediately after the PVA waste water is brought into contact with the salting-out solution, and the PVA deposited is present in a very viscous state. If the boosting plate is used for contact pushing, the separated PVA is very easy to adhere to the boosting plate, so that the recovery of the PVA is influenced, the boosting plate is damaged, and the normal operation of equipment is influenced. Therefore, the power-assisted plate is far away from the waste water inlet. Repeated experiments show that after the PVA wastewater is discharged from the liquid inlet and is contacted with the salting-out liquid for 30 seconds, a layer of smooth film structure is formed on the surface of the precipitated PVA, so that the viscosity is reduced sharply, and the assisting plate is not adhered when being contacted with the salting-out liquid. The PVA waste water and the salting-out solution are ensured to be in contact reaction for 30 seconds and then are boosted by a boosting plate.

The salting-out solution can be a mixed solution of mirabilite, caustic soda and sulfuric acid, and the concentration is about 7 percent approximately. The salting-out solution may be any other agent capable of precipitating PVA as a solid.

B. The mixture flows through the reaction vessels 103 via the overflow 1031 until the reaction is complete.

The design of the reaction tank 103 with multiple layers of layers ensures that the salting-out solution has sufficient contact time with PVA wastewater and can ensure that the PVA is completely precipitated.

C. The mixed liquor and PVA solid enter a solid-liquid separation zone 2 at the end layer of the reaction tank 103, the mixed liquor is separated from the PVA solid, the mixed liquor enters a liquid medicine regeneration zone 4 through a liquid collection port 201, and the PVA solid enters a solid crushing zone 3 through a solid collection port 202.

The separated PVA solid and the mixed solution are separated under the action of the solid-liquid separation zone 2, and the PVA solid can be recovered. The mixed liquid is collected into the chemical liquid recovery tank 401 in the chemical liquid regeneration area 4 through the liquid recovery hole 2031.

D. The solid crushing zone 3 crushes and extrudes the PVA solid, mixed liquid wrapped in the PVA solid is discharged to obtain PVA powder, the mixed liquid is discharged and then enters the liquid medicine regeneration zone 5 through the second liquid collecting port 305, and the PVA powder enters the drying zone 4 through the solid powder collecting port 3031.

In the salting-out process, a PVA component in the wastewater is dehydrated to form a solid, but the process is slow, the law that the outer layer PVA is firstly contacted with the salting-out liquid and is firstly solidified and the inner layer is then contacted with the salting-out liquid and is then solidified is presented, a large amount of water and mixed liquid are wrapped in the outer layer of the PVA which is firstly solidified at the moment, the water is tightly surrounded by a PVA molecular membrane, and the PVA can not be separated by means of conventional solid-liquid separation. The invention adopts a specially-made grinding screw extruder to complete the step of destroying the PVA molecular film and releasing the mixed solution.

PVA solid enters the screw barrel 301 from the feeding port 3013, the rotary driving device 304 drives the screw 302 to rotate, the PVA solid is matched with the conveying section 3021 of the screw 302 through the shearing part 3011 of the inner wall of the screw barrel 301, and the PVA solid is pushed forwards to the grinding section 3022 for grinding. The screw pitch of the conveying section 3021 of the screw 302 is greater than that of the grinding section 3022, so that the gap between the conveying section 3021 and the screw barrel 301 is increased, the conveying effect of the screw 302 is improved, and the gap between the grinding section 3022 and the interior of the screw barrel 301 is decreased, so that the extrusion force applied to the PVA solid is increased. When the PVA solid is pushed to the grinding section 3022, the PVA solid is subjected to shearing grinding through the matching of the shearing part 3011 on the inner wall of the screw barrel 301 and the outer edge of the grinding section 3022 of the screw rod 302, the PVA solid is crushed and ground into powder, a PVA molecular membrane is damaged, the mixed liquid wrapped in the PVA solid is released, and the PVA solid naturally flows out of the plurality of inclined micropores 3012 which are distributed on the side wall of the bottom of the screw barrel 301 along the axial direction. Increase the shearing force of shearing part 3011 inner wall through shearing part 3011 to improve the grinding effect, avoid screw rod 302 to take place to skid at propulsion in-process PAV solid simultaneously, make the unable normal propulsion of PVA solid.

After the grinding section 3022 is ground into a powder to break the molecular film, the PVA solids are pushed forward to the extrusion section 3023 for extrusion. The cross section of the screw barrel 301 is gradually increased along the extrusion direction, so that the volume of the screw barrel 301 is gradually increased, the ground PVA powder is gradually expanded, a plurality of flow guide grooves 3032 are arranged on the inner wall of the extrusion head 303 along the circumferential direction, the cross section of the extrusion head 303 is in a truncated cone shape, and the space of the extrusion head 303 is gradually reduced, so that the pressure applied to the PVA powder in the extrusion process is gradually increased, and the PVA powder flows to a solid powder collecting port discharge port 3031 along the flow guide grooves 3032 to be extruded and recovered. A plurality of second inclined micropores 3033 are formed in the flow guide groove 3032 at the bottom of the extrusion head 303, and mixed liquid which cannot be naturally discharged from the grinding section 3022 after being released is discharged from the second inclined micropores 3033 under the matched extrusion of the extrusion section 3023 and the extrusion head 303, so that the squeezing effect is achieved.

The driving speed of the rotary driving device 304 is controlled to be slow, within the range of 10-30r/min, preferably 15r/min, so as to avoid the heating up of the PVA solid caused by the over-high rotating speed and the PVA solid being adhered on the surface of the screw 302 or the inner wall of the screw barrel 301.

E. And drying the PVA powder in a drying area 4 to obtain a PVA recovery product.

The water content of PVA powder obtained after grinding and squeezing is greatly reduced, and then the PVA powder is dried in a drying area 4 to obtain a PVA recovery product which has almost no difference with a newly prepared PVA product and can be used as an industrial raw material again.

F. The mixed liquor enters a liquid medicine regeneration area 5, is collected in a liquid medicine recovery tank 501, then enters a liquid medicine regeneration tank 502 through a pipeline for concentration and regeneration, and then returns to the step A through a liquid medicine inlet 102 to replace part of salting-out liquid for recycling.

The mixed solution contains other impurities in the wastewater and a large amount of effective components of the salting-out solution, the salt concentration of the mixed solution is returned to about 7 percent through treatment, and then the mixed solution can be used for replacing about 80 to 90 percent of the salting-out solution in a new round of reaction, so that the treatment cost of the PVA wastewater is greatly reduced, and the influence of high-salt discharge on the environment is avoided. The concentration regeneration is a responsible evaporation impurity removal process, and needs a plurality of liquid medicine regeneration tanks 402 to be matched to complete the process, so that redundant water and impurities mixed in the salting-out process are removed, and the concentration of the salting-out solution is improved.

Effect example 1

The PVA products obtained in example 1 were subjected to a water content test, and the results are shown in the following table:

sampling phase	Step C	Step D	Step E
				Water content	85％-90％	40％-50％	10％-15％

From the test data it can be seen that: the PVA solid precipitated after the salting-out reaction (i.e., step C) still contains a large amount of water of 85% to 90% even after the solid-liquid separation treatment, and therefore, the PVA solid is hardly recovered and reused. And the water content of the crushed PVA powder is reduced to 40-50% (step D), and the water attached to the surface of the PVA powder instead of being wrapped in the PVA powder can be removed by a conventional drying method. The water content of the dried PVA product is only 10-15%, and the PVA product is almost not different from the PVA sold in the market, and can be used as an industrial raw material.

Effect example 2

The water discharged after the treatment in step F in example 1 was subjected to data detection, and the results are shown in the following table:

as can be seen, all indexes of water discharged after being treated by the PVA wastewater treatment and recovery system can meet the environmental protection requirement, particularly the COD value is reduced from tens of thousands of the common PVA industrial wastewater to dozens of the common PVA industrial wastewater, and the PVA wastewater treatment and recovery system makes excellent contribution to the environmental protection industry.

While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

Claims

1. A PVA waste water treatment and recovery system is characterized by comprising a salting-out reaction area, a solid-liquid separation area, a solid crushing area, a drying area and a liquid medicine regeneration area, wherein the liquid medicine regeneration area and the solid-liquid separation area are respectively connected with the salting-out reaction area, the solid crushing area is connected with the solid-liquid separation area, and the drying area is connected with the solid crushing area; the salting-out reaction zone comprises a wastewater inlet, a liquid medicine inlet and a plurality of stacked reaction tanks, and each layer of each reaction tank is provided with an overflow port; the waste water inlet and the liquid medicine inlet are arranged at the top layer of the reaction tank, and the last layer of the reaction tank is connected with the solid-liquid separation zone; the solid-liquid separation zone is provided with a liquid collecting port and a solid collecting port, and the solid collecting port is connected with the solid crushing zone; the solid crushing area is provided with a second liquid collecting port and a solid powder collecting port, and the solid powder collecting port is connected with the drying area; the liquid medicine regeneration area comprises a liquid medicine recovery tank and a liquid medicine regeneration tank, and the liquid medicine recovery tank is connected with the liquid medicine regeneration tank through a pipeline; the liquid medicine recovery tank is connected with the liquid collecting port and the second liquid collecting port, and the liquid medicine regeneration tank is connected with the liquid medicine inlet;

the solid crushing area comprises a screw barrel, a screw rod, an extrusion head and a rotary driving device, the screw rod is rotationally arranged in the screw barrel, the extrusion head is fixedly connected with the opening end of the screw barrel, and the end part of the screw rod extends outwards and is fixedly connected with the rotary driving device; the screw comprises a conveying section, a grinding section and an extrusion section, the conveying section, the grinding section and the extrusion section are sequentially arranged along an extrusion direction, a shearing part matched with the grinding section of the screw for shearing and grinding is arranged on the inner wall of the screw barrel along the circumferential direction, and a plurality of inclined micropores are distributed on the side wall of the bottom of the screw barrel along the extrusion direction; a feeding hole is formed in the side wall of the top of the screw, which is adjacent to the conveying section of the screw, the center of the extrusion head is provided with the solid powder collecting hole, the inner wall of the extrusion head is circumferentially provided with a plurality of flow guide grooves, and the rotary driving device drives the screw to rotate to grind and crush the solid; the inclined micropores are communicated with the second liquid collecting port.

2. The PVA wastewater treatment and recovery system according to claim 1, wherein a booster plate is arranged at the top of the reaction tank, and the booster plate is far away from the wastewater inlet and the liquid medicine inlet; the boosting plate is a plate frame and is arranged on a conveying belt, and the boosting plate moves in the reaction tank through the conveying belt.

3. The PVA wastewater treatment and recovery system of claim 1, wherein the solid-liquid separation zone comprises a screw extruder, and the solid collection port is arranged at an extrusion end of the screw extruder; the bottom of the screw extruder is provided with a liquid recovery hole which is communicated with the liquid collecting port.

4. The PVA waste water treatment and recovery system according to claim 3, wherein the screw extruder is a twin screw extruder.

5. The PVA waste water treatment and recovery system according to claim 1, wherein the pitch of the conveying section is greater than the pitch of the grinding section; the cross section of the screw cylinder is gradually increased along the extrusion direction; the cross section of the extrusion head is in a truncated cone shape, and a plurality of second inclined micro-holes are formed in the flow guide groove at the bottom of the extrusion head; the second inclined micropores are communicated with the second liquid collecting port.

6. A treatment and recovery process using the PVA wastewater treatment and recovery system according to claim 1, comprising the steps of:

B. the mixed solution flows through the reaction tanks of all layers through the overflow ports until the reaction is completed;

D. the solid crushing area crushes and extrudes the PVA solid, the mixed liquid wrapped in the PVA solid is discharged, PVA powder is obtained, the mixed liquid enters the liquid medicine regeneration area through the second liquid collecting port after being discharged, and the PVA powder enters the drying area through the solid powder collecting port;

E. drying the PVA powder in the drying area to obtain a PVA recovery product;

F. and B, the mixed liquor enters the liquid medicine regeneration area, then is collected in the liquid medicine recovery tank, then enters the liquid medicine regeneration tank through a pipeline for concentration and regeneration, and then returns to the step A through the liquid medicine liquid inlet to replace part of the salting-out liquid for recycling.

7. The treatment and recovery process of the PVA waste water treatment and recovery system according to claim 6, wherein the salting-out solution is contacted with the PVA waste water to react for 30 seconds in the step A, and then the mixed solution is boosted to assist the flow of the mixed solution.

8. The PVA waste water treatment and recovery system treatment and recovery process according to claim 6, wherein in the step A, the salting-out solution is a mixed solution of mirabilite, caustic soda and sulfuric acid.

9. The recycling process for PVA waste water treatment system according to claim 6, wherein in the step F, the plurality of the chemical liquid recycling tanks are provided, and the concentration recycling is performed by: evaporating the excess water in the mixed solution; and (3) after the mixed solution is regenerated, returning to the step (A) to replace 80-90% of the salting-out solution for recycling.