CA1073597A - Process and apparatus for treating polyvinyl alcohol containing waste liquid - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
A process and an apparatus for treating waste liquid containing polyvinyl alcohol (hereinafter will be called PVA) wherein the waste liquid which is generated through textile pro-duct treating processes such as desizing, scouring, etc. is col-lected in a reaction tank. Reaction is carried out in the tank by adding a PVA binder such as formalin, salt cake, soda ash, bo-rax, etc. with air or steam blown in as required to produce the insoluble solid of PVA. The insoluble solid of PVA is separated from the waste liquid and an apparatus comprising a waste liquid treating reaction tank, a chemical tank, an air or steam blowing-in mechanism, a centrifugal separator or a filtrating mechanism with a timing control mechanism, a treating liquid reservoir, a solid receiving tank, etc.

Description

- 10'735~9~

This invention relates to a process and an apparatus for separating and recovering PVA, which is contained in a waste li-quid used for artificial sizing of textile and for purifying the waste liquid to eliminate the possibility of a public pollution, by separating and recovering the solidified PVA from the liquid.
Heretofore, the waste liquid which is generated through such desizing processes for textile products has been treated by an activated sludge process or the like before discarding it.
In accordance with the conventional treating processes, however, reduction in C,O,D. is impossible while B.O.D. can be lowered to a value below a given value.
The sizing compound (PVA~ employed in the textile wear-ing process is washed off to a great extent during desizing and scouring treatment. The washed off siæing compound flows into rivers. This has been causing a public pollution. Furthermore, in cases where a high temperature desizing or scouring treatment is carried out for cloth materials, the C.O.D. of such environ-,' ment contaminating PVA flowing out together with hot water amounts to about lO,000 to 12,000 p.p.m. Whereas, the maximum allowable C.O.D. limit is 30 p.p.m. according to the Inland SeaRegulation of Japan.
Particularly, a great amount of water is required for desizing, scouring and bleaching T/~ cloth materials. In such a process, the sizing compound PVA sticking to the cloth material is washed away together with water while it is still on the weaving machine. This intensifies the public nuisance. With ; the operating speed of T/C cloth weaving machines having been increased in these days, the sizing compound for warp contains about 6~/o PVA and about 4~/O starch paste. The public pollution problem in terms of B.O.D. has completely been solved. Ho~ever, the C.O.D. problem still remains unsolved throughout the world.
Yet, in recent years, the regulations against i ,. ...

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environmental pollution ha~e been strengthened including severer regulations in terms of C,O.D. Hence, there is a strong require-ment for an environmental pollution preventing process applicable to the desizing treatment of the PVA sizing compound.
In accordance with the treating process of this inven-tion, the PVA containing waste water is completely ~ecovered without allowing it to flow out and is stored in a waste water treating reaction tank. Then, a PVA binder or a flocculating gelation agent such as ammonium sulfate, soda ash, borax, forma-line or salt cake with an acid is added to the waste liquid in the tank and is mixed with the waste liquid there. By ~his, PVA
is qolidified, preferably through a high temperature treatment and with air or steam blown into the mixture as required. Most ~about 98%) of PVA is removed by one process of this treatment by sepa-rating the solidified PVA from the waste water and is continuous~
ly and automatically discharged. In this process, it is also pos-sible to discharge PVA alone. The PVA thus recovered can be re-used as material for various purposes such as adhesive for ply-wood, artificial soil, coating materials, etc.
Thus according to one aspect of the invention there is provided a process for treating waste water containing poly-vinyl alcohol to remove the polyvinyl alcohol therefrom comprising the step~ of: a) adding to said waste water a polyvinyl alcohol binder selected from the group consisting of ammonium sulfate, soda ash, borax, formalin, and salt cake; b) heating and mixing the mixture from a) to a temperature in the range from about 80 to 100C by blowing air or steam into the waste water to produce an insoluble solid of polyvinyl alcohol; c) adding a flocculating agent to the waste water at a temperature effective for flocculation; and d) separating flocculated solid from the waste water.

B ~ - 2 _ . . : : - -In another aspect of the invention there is provided an apparatus for treating polyvinyl alcohol containing waste water, the apparatus comprising: i) at least one treating reaction tank having a water supply pipe, ii) at least one chemlcal additive containing tank communicating with the treating reaction tank; iii) air or steam blowing-in pipe connected to an opening provided in the bottom of the treating reaction tank; iv) separating means for separating solidified polyvinyl alcohol solids and waste water; v) means for receiving unsolubilized solids from said separating means; and -vi) means for receiving waste water from said separating means.
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With the waste water temporarily stored in the treating reaction tank without allowing it to flow away; the PVA is solid-ified in 15 to 30 minutes when the treating process is carried out at a constant temperature of 50C and 3 to 5 minutes when the pro-cess is carried out at a high temperature of 160C under high pressure. The solidified PVA is separated from water and is col-lected by allowing it to float or to precipitate.
This invention is also directed to the provision of a PVA recovering process and an arrangement for carrying out the process, wherein, for example, an absorbing gelation agent is added to the waste water in a first treating reaction tank. Then the temperature o~ the waste water to which the absorbing gela-tion agent is added, is adjusted to about 80C with stirring.

B 2a -: . ' ', 1~73S9'~' Following this, the mixture is supplied to a second reaction tank, In the second tank, a flocculating agent is added to the mixture and reaction is carried out at a temperature of about 60C with stirring. Then the solid-liquid separation is carried out to recover PVA, By this method, the recovery rate of the PVA
contained in the waste water can be enhanced. In addition to such heating treatment, the effect of the invented process can also be enhanced by blowing in air or steam to effect stirring or to simultaneously effect stirring and heating.
Where the waste water in the above mentioned heat treating tank is treated with addition of salt cake or formalin with acid either at normal temperature or with heating, or at high temperature and high pressure, to separate PVA from water, the formalin contained in the separated waste water can be neu-tralized with the waste water resulting from chlorite processing to change it into formic acid for reuse.
According to the present invention, PVA in the waste liquid is formalized by addition of formalin to solidify PVA
and is separated, or PVA is gelated by addition of boron com-pounds such as borax and boric acid and separated optionally withaddition of inorganic acid salts of sodium, ammonium magnesium, calcium and aluminium.
The formalization of PVA by formalin is preferably effected with addition of inorganic acid such as sulfuric acid, hydrochloric acid, phosphoric acid, etc. at a temperature pre-ferably between 80 - 100C for 5 to 10 minutes. The reaction goes according to the formula - CH2CH(OH) - CH2 - CH(OH) - + HCHO----~CH2CH - CH2CH - + H20 O - CH _ O

2 (l) (water-soluble) (non-water-soluble) ... . .. .. - . . --i~q3S9 As shown in Figure 9, it is desirable that 10 - 30cc of 37% formalin solution and 5 - 15cc of 66Be sulfuric acid are added to 1~ of the waste liquid for 70 to 10~/o formali-zation of PVA.
When PVA is gelated by addition of the boron compound, the reaction goes according to the formula -~CH2CH(OH) ~n + B - CH2 ~ fH ~ CH2 - CH ~

\ _ / +
B ~ Na o/ ~ O, (2) ~ CH2 ~ CH - CH2 ~ CH -The above reaction proceeds more effectively when the pH value is between about 8 and 10, and by this reaction PVA
gelates discharging water. In this case, it is desirable to add hydroxide of sodium potassium, ammonium and calcium, etc. for the adjustment of the pH value. As shown in Figure 10, it is de-sirable that 1 - 2 gle of the boron compound (borax), 3 - 6 gle of ammonium sulfate are added for obtaining the desired results.
Also as understood from the reaction formula (2), the gelated PVA is easily converted into water-soluble PVA~ 50 that the recovered PVA can be reused, and almost 100% recovery of PVA
is attained without causing formation of sludge.
Further as understood from Fig. 11, when the PVA con- -taining waste liquid is heated to about 80C with or without ; stirring, by blowing heated air or steam, the recovery of PVA is improved, As described in the foregoing, this invention has many advantages and the hitherto unsolved problem of how to remove PVA from waste water can be quite effectively solved by the in-vented process and apparatus.
Further objects, features and advantages of the method ~ 4 ~

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-~Oq3597 and apparatus of this invention will become apparent from the following detailed description of the preferred embodiments taken in connection with the accompanying drawings in which:
FIGURE 1 is a side view illustrating a first embodiment example of the apparatus to be employed in the waste water treat-ing process of the present invention.
FIGUP~E 2 is a side view illustrat~ng a second example of the apparatus.
FIGURE 3 is a side view illustrating a third example of the apparatus.
FIGURE 4 is a schematic illustration of the arrangement of the first example and the sequence of the treating process.
FIGURE 5 is another schematic illustration of the ar-rangement of the second example and the sequence of the treating process accomplished thereby.
FIGURE 6 is a schematic illustration of the third ex-ample.
FIGURE 7 is another schematic illustration of an arrange-ment wherein there is provided a device for pulverizing and dry-ing the PVA, which has been flocculated and solidified in accord-ance with the invented process.
FIGURE 8 shows another embodiment of the present inven-tion.
FIGURE 9 is a graph showing recovery of PVA by addition of formalin.
FIGURE 10 is a graph showing recovery of PVA by addition of borax, and FIGURE 11 is a graph showing effects of heating on the recovery of PVA, Example 1 (Figure 1) Referring to Figure 1, PVA containing waste water (li-quid temperature 85C) is supplied through a water feeding port 2 to a PVA liquid tank 1, which is kept at a temperature between 80C and 100C, In the tank 1, the formalin which is added from a liquid reservoir 3 and an acid which is added from another li-quid reservoir 4 are allowed to react to insolubilize and solidi-fy the PVA contained in the waste water. At the bottom of the tank 1, there is provided an air blowing-in port 5 for the com~
bined purposes of temperature adjustment and stirring.
The waste water in which a solid matter has been pro-duced by reaction with PVA enters a centrifugal type rotary con-tinuous separator 6, which separates the water content containingan excess of formalin to store it in a formalin containing water reservoir 7 disposed in the lower part On the other hand, the solid content of the waste from which the water content has been thoroughly removed is placed on a solid matter conveyor 8 to be taken out thereby, there are also provided a pulley 9, a motor 10 and an outlet port 11.
Ex mple 2 (Figure 2) In this example, the arrangement is identical with the preceding example up to the point of the waste water tank 1 as illustrated in Figure 2. However, the liquid from the tank 1 is time adjusted in a timing chamber 13 in which there is provided a multi-stage shoot 12 for the purpose of ensuring thorough for-mation of the solid matter by the reaction with formalin. Fol-lowing this, the liquid is allowed to fall on an endless net con-veyor 14. The water content is stored in the formalin containing water reservoir 7 while the solid content is collected at a re-ceiving tank 16 through a shoot 15.
Example 3 (Figure 3) Referring to Figure 3, the waste water is collected in a waste water tank 104 in the same manner as i~ Example 2. In Example 3, however, the additives to be added to the waste water come from a borax ~or boric acid) reservoir 114, a soda ash (or 1~359'~

brine) reservoir 115 and an ammonia sulfate reservoir 116 The reaction is carried out a~ a temperature of 20C or thereabout with stirring. For this purpose, a temperature adjustment air blowing-in port 117 is provided in the bottom of the tank 104 with the above mentioned stirring effected also through this.
Since the liquid inside the tank 104 immediately pro-duces the precipitation of PVA, the liquid is allowed to flow out as it is onto a filtering plate 109. The water content sep-arated by this is allowed to drip into a receiving tank 110. In Figure 3, reference numeral 101 indicates a waste water feeding pipe ; 102 a filtering plate: 103 a receiver for waste, etc,; and 113 a precipitate receiving tank.
Example 4 (Figure 4) In this example as shown in Figure 4, chemical reser-voirs 201 and 202 contain liquid chemicals such as formalin, etc.
which are stirred by stirrers 203 before they are supplied into a mixing tank 205 through a liquid flow meter 204, The mixing tank 205 is arranged t~ be fed by a waste water supply pump 206 with PVA containing waste wa~er which is discharged, for example, from a continuous cloth material desizing process, The discharged waste water is mixed with the liquid chemicals inside the mixing tank 205, With the liquid chemicals having been added to the dis-charged waste water, the mixture is supplied to a first reaction tank 208 through a discharged liquid passing long pipe 207 which is wound into a spiral shape to prevent short passing of the liquid mixture for maintaining a sufficiently long period of reaction time, The discharged liquid passing spiral pipe 207 is disposed inside a temperature control tank 209 so that the liquid passing through the spiral pipe 207 can be maintained at a desired temperature with water or hot water of a suitable temperature supplied to the inside of the temperature control tank. In the present example, the tem-perature of the discharged waste water to be fed into the mixing .

lOq359q tank is about 80C. The coagulation of PVA can be facilitated by lowering the temperature to about 60C inside the spiral passing pipe 207 In addition to that, the use of the tempera-ture control tank 207 also permits adjustment to a temperature that is suitable for the liquid chemicals employed as additives The liquid supplied into the first reaction tank 208 is stirred by a stirring screw 211 to be flocculated or coagulated there. After this, the liquid is supplied to a second reaction tank 210 and is further stirred by another stirring screw 211 for gelation The gellèd solid and other liquid contents are allowed to overflow the second reaction tank 210 and flow down on a solid-liquid separating plate 212 where the solid is separated from the liquid.
The liquid is then transferred to a water tank 213 while the solid i9 transferred by a conveyor 214 to the point of desired subse-quent process. The reference numeral 218 indicates a discharge liquid flow meter.
As described in the foregoing, the discharged liquid to which liquid chemicals have been added is supplied through the discharged liquid passing pipe 207 to the first and second reaction tanks 208, 210 one after the other. For passing through the pipe 207, a suitable length of time is consum~d to ensure a suitable length of reaction time. At the same time, the liquid temperature is adjusted to the desired temperature of ; about 60C to prevent gelation in the passing pipe. In addition to such advantages, the temperature is adjustable also according to the chemicals to be employed, so that such chemicals can be selected out of a wider range of chemicals. Furthermore, the use of such a pipe for timing prevent short passing of the liquid flow to ensure homogeneous reaction.
Example 5 (Figure 5) In this example, as shown in Figure 5, the first re-action tank 208 employed in Example 4 is replaced with a smaller B

~0~359~

reaction tank 208'; above the upper part of the solid-liquid sep-arating plate 212 employed in Example 4, there is added a solid-liquid separating pipe 215 which communicates with the outlet port of the second reaction tank 210; a spiral reaction pipe 216 is connected to the discharge port of the water tank 213 of Ex-ample 4; and an additional solid-liquid separating plate 217 is provided at the outlet end of the spiral reaction pipe 216 Furthermore, in accordance with this embodiment example, there is provided an air injection pipe 219 at the bottom of the second reaction tank 210 for the purpose of injecting air into the dis-charged liquid. The provision of the air injecting pipe not only facilitates the recovery of PVA but also accelerates stirring with air.
With the size of the first reaction tank 208' being arranged small, the whole system can be made smaller in accord-ance with this example. Also, since the solid-liquid separating step is repeated by the provision of the solid-liquid separating pipe 215 and the solid-liquid separating plates 212 and 217, reac-tion can be made thoroughly to ensure better separation of the solid from the liquid. Thus this example gives these advantages in addition to those mentioned in Example 4.
Example 6 (Figure 6) Referring to Figure 6, the discharged waste liquid coming through a discharged liquid supply pipe 321 is supplied to a first reaction tank 320. In the first reaction tank 320, there are provided baffle boards 322 to cause the discharged liquid to move up and down in a zigzag manner for the purpose of stirring, A liquid chemical container 323 is mounted on the discharged waste liquid supply pipe 321~ Another liquid chemical container 335 is mounted on the reaction liquid outlet pipe 324, which is provided also with branch pipes 324' and 324" serving as discharged liquid supply pipes for second reaction tanks 325 and 32S'. These second _ 9 _ 1~73~9~^~

reaction tanks 325 and 325' are surrounded by cooling water tanks 326 and 326' respectively. At the bottoms of these second reaction tanks, there are provided bottom lids 328 and 328i which are opened and closed by cylinders 327 respectively~
Beneath the second reaction tanks 325 and 325l, there is provided a net conveyor 329 ~r the purpose of solid-liquid separation. Beneath this net conveyer, there is provided a water receiving tank 330 which communicates with a stirring tank 331. A solid-liquid separating plate 332 follows the stirring tank 331. The reference numerals 333 and 334 indicates a water tank and a solid matter container respectively. The system as described above operates as follows:
The discharged waste water to which a liquid chemical from the liquid chemical container 323 has been added is supplied to the first reaction tank 320, in which a convection of the liquid takes place to effect a moderate stirring. After that, for example, a flocculating agent or coagulant is added from the chemical container 335 while the waste liquid is flow-ing through the outlet pipe 324. Then, the liquid is supplied to the second reaction tanks 325 and 325'. The first reaction liquid which is thus supplied into the second reaction tanks 325 and 325' is stirred at about 60C by stirring screws and/or stirring air (unillustrated) in conjunction with the cooling water tanks 326 and 326'. W~en the stirring has been completed, when the PVA has flocculated or coagulated, the lid 328 or 328' is opened by actuating the cylinder327. Then, the solid and water contents which have reacted inside the second reaction tank 325 ; ar 325' are separated on the conveyor 329 and are respectively guided to the container 334 and the water tank 330. The liquid supplied to the water tank 330 is stirred inside the stirring tank 331 in which PVA further coagulates and is separated at the next solid-liquid separating plate 332 before recovery thereof. In accor--- 10 _ :lOq359~

dance with this embodiment example, a plurality of second reaction tanks are provided. Th~s arrangement permits con-tinuous processing operation of the apparatus by alternately opening or closing the bottom lids of these tanks and also enables the operation to have a longer period of time for reaction inside the second reaction tanks~
Example 7 (Fig. 7) This embodiment example which is illustrated in Fig.
7 includes the provision of a recovering arrangement wherein the PVA recovered from the discharged waste liquid is pulverized and dried to facilitate preservation or transportation of the PVA for reuse of commercialization thereof.
Referring to Fig. 7, a first reaction tank 401 is provided with a waste liquid supply port 402 which permits the inflow of the PVA containing waste liquid and an outlet port 403 which is for the outflow of reaction liquid. A cooling water tank 404 surrounds the periphery of the first reaction tank 401 to permit cooling water supply. Inside the first reaction tank 401, there is provided a stirring screw 406 which is rotated by a motor 405. The reference numeral 407 indicates a container for a chemical to be employed as additive and 408 a second reaction tank. The second reaction tank 408 is equipped with an inlet 409 which allows the first reaction liquid coming from the first reaction tank 401 to enter the second tank, a stirring screw 410 which stirs the liquid inside the reaction tank 408, a motor for rotating the screw 410, a chemical container contain-ing a chemical to be added to the liquid inside the tank 408 and an outlet port 413 for allowing the second reaction liquid to flow out after reaction in the second reaction tank 408. A
cooling water tank 414 surrounds the periphery of the second -reaction tank 408. A solid-liquid separating plate 415 separates the solid content of the second reaction liquid from the liquid ~0~35~'~

content thereof. The liquid content separated from the solid is received by a water tank 416 while the separated solid comes into a hopper 417 which supplies the solid to a pulverizer 418 disposed below the hopper. A conveyer 419 is provided on the discharge side of the pulverizer and is arranged to travel through the inside of a drying chamber 421 which is provided with a heat source 420. Leveling rolls 422 are disposed inside the drying chamber and above the conveyer. The pulverized PVA
is received by a container 423.
This embodiment example of the invention being arranged as described in the foregoing, it operates as follows: The PVA
containing waste liquid which is discharged, for example, from a cloth desizing process is supplied to the first reaction tank 401, Following this, ~ suitable amount of an absorbing gelation agent contained in the chemical container is added to the liquid. Concurrently with this, the waste liquid inside the first reaction tank 401 is kept at a temperature of about 80C by means of cooling water supplied into the cooling water tank 404. A primary reaction treatment is thus carried out at about 80C for about 30 minutes with gentle stirring. The first reaction liquid which had undergone the primary reaction is supplied to the second reaction tank 408 where a suitable amount of a coagulant contained in the chemical container 412 is added to the first reaction liquid and a secondary reaction is carried out with stirring and keeping the liquid inside the second reaction tank at a temperature of about 60C with cooling water supplied into the cooling water tank 414. The second reaction liquid which has undergone the secondary reaction in this manner is allowed to flow out through the outlet port 413 to flow downward over the solid-liquid separating plate 415 which separates the solid and liquid components of the liquid. The solid is guided into the hopper 417 while the liquid goes into - 12 _ 10'7359q the water tank 416. The solid put into the hopper is gradually pulverized by the pulverizer 418 and is then put on the conveyer 419 which carries the pu~verized solid into the drying chamber 421. The pulverized solid is dried there and is put into the container 423.
Example 8 (Fig. ~
Referring now to Fig. 8, on the upper cover o~ each of reduced pressure cooling tanks 501a, 501b and 501c, there are provided an inlet pipe 502 which supplies the waste liquid coming from an unillustrated desizing tank, a chemical injecting pipes 504 which are connected to chemical tanks 503 filled with chemicals such as formalin, etc. and a vacuum pipe 505, all of these pipes piercing the upper cover of each reduced pressure cooling tank and being held there. A steam injecting pipe 506 is disposed on the bottom of each of the reduced pressure cool-ing tanks 501a, 501b and 501c. Each cooling tank is provided with a bottom lid 508 which is opened and closed by an air cylinder 507. A shoot 509 is provided beneath the steam inject-ing pipes 509 in such a way as to receive the liquid falling off these steam injecting pipes 509. Over the shoot, there is pro-vided a first filtrating plate 510 of a wire gauze-like form.
A second filtrating plate 511 follows the first filtrating plate 510 with a separated water receiving tank 512 disposed beneath the second filtrating plate. The second filtrating plate 511 is followed by a solid container 513. There are also provided a vacuum pump 514 which communicates with the vacuum pipe 505, a water receiving tank 51S which receives the water sucked in by the vacuum pump and solenoid valves 516 and 517. The embodiment example which is arranged as described above operates in the following manner:
When the solenoid valve 516 is opened, the waste liquid from the desizing tank is supplied into the reduced pressure cool-ing tanks 501a, 501b and 501c. The solenoid valve 516 auto-.

~)"Y3S9~

matically closes when these reduced pressure cooling tanks have been supplied with a preset amount of the waste liquid. Con-currently with the closing of the solenoid valve 516, another solenoid valve 517 opens to add a preset amount of a liquid chemical from the liquid chemical tank 503 to the waste liquid.
Then, steam is injected from the steam injecting pipe S06. This steam injection serves not only to heat but also to stir and mix the waste water and the added liquid chemical. After stirring by the steam injection has continued for about 10 to 20 minutes, the steam supply is cut off. Following this, the vacuum pump 514 is actuated to reduce pressure and to cool the liquid temperature down to about 75 to 50C. This causes the solidifi-cation of the PVA contained in the waste liquid.
With the PVA content having been thus solidified, the waste water is allowed to flow out from the reduced pressure cooling tank and to flow down over the shoot S09. For this, the bottom lid of the reduced pressure cooling tank 501a is first opened. When the flowing down of the liquid from the tank 501a has been completed, the bottom lid o~ the next reduced pressure cooling tanks 5~1b is opened to allow the liquid to flow down from the tank 501b. While the liquid in the tank 501b is in process of flowing down therefrom, the bottom lid of the tank 501a may be closed and the solenoid valve thereof may be opened to resume the supply of the waste liquid to the reduced pressure cooling tank 501a. ~hen, in the same manner as described above, the bottom lid of the reduced pressure cooling tank 501c opens upon completion of the flowing of the waste liquid out from the reduced pressure cooling tank 501b. Mean-while, the waste liquid in the reduced pressure cooling tank 501a is stirred and the waste water is supplied also to the reduced pressure cooling tank 501b.

As described in the foregoing a plurality of reduced pressure cooling tanks are provided with arrangement to delay the timing for steps to supply the waste liquid, to stir it and to discharge it for these tanks one after another. This arrangement ensure thorough stirring of the waste liquid per unit volume thereof inside each tank and yet permits continuous processing operation.
Since the mixing and heating of the waste liquid and the liquid chemical are accomplished by means of a steam injecting force, the two liquids are effectively stirred and mixed. Furthermore, with the liquid mixture being cooled under reduced pressure by means of a vacuum pump, the PVA content of the waste water is solidified efficiently and without fail, so that the purpose of the operation can be attained without difficulty.

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Claims (11)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A process for treating waste water containing poly-vinyl alcohol to remove the polyvinyl alcohol therefrom com-prising the steps of:
a) adding to said waste water a polyvinyl alcohol binder selected from the group consisting of ammonium sulfate, soda ash, borax, formalin and salt cake, b) heating and mixing the mixture from a) to a temperature in the range from about 80 to 100°C
by blowing air or steam into the waste water to produce an insoluble solid of polyvinyl alcohol, c) adding a flocculating agent to the waste water at a temperature effective for flocculation;
and d) separating flocculated solid from the waste water,

2. A process according to claim 1, wherein in c) said flocculating agent is added at a temperature of about 60°C.

3. A process according to claim 1 or 2, wherein steam is blown into the waste water in b).

4. A process according to claim 1 or 2, wherein air is blown into the waste water in b).

5. An apparatus for treating polyvinyl alcohol containing waste water, the apparatus comprising:
i) at least one treating reaction tank having a water supply pipe, ii) at least one chemical additive containing tank communicating with the treating reaction tank;

iii) air or steam blowing-in pipe connected to an opening provided in the bottom of the treating reaction tank;
iv) separating means for separating solidified polyvinyl alcohol solids and waste water, v) means for receiving insolubilized solids from said separating means; and vi) means for receiving waste water from said separating means.

6. An apparatus according to claim 5, wherein said separating means iv) comprises a centrifugal separator disposed so as to permit solidified polyvinyl alcohol contain-ing waste water to flow thereto from said reaction tank;
said means vi) being disposed beneath said centrifugal separator; and said means v) comprising a solid matter conveyor disposed below a solid matter outlet part in the separator.

7. An apparatus according to claim 5, further including a timing chamber containing a multistage shoot disposed between said reaction tank and said separating means, said separating means comprising; a net conveyor adapted to convey solid solidified polyvinyl alcohol from the liquid falling from the timing chamber, and a shoot disposed at a front end of the conveyor said shoot communicating with said means v).

8. An apparatus according to claim 5, wherein said treating reaction tank includes a primary filtrating plate and a waste receiver disposed at an upper end of the tank to receive polyvinyl alcohol containing waste water entering through an inlet pipe; a second filtrating plate connected to a discharge port provided in the bottom of the reaction tank;
a receiving plate connected to a front end of the second filtrating plate, said means vi) being disposed beneath said second filtering plate, and said means v) being disposed beneath said receiving plate.

9. An apparatus according to claim 5, including a waste liquid passing long pipe disposed between said communicat-ing with said reaction tank i) and said additive tank ii) adapted to adjust waste water to a preset temperature and to prevent short pass of the waste water after a polyvinyl alcohol solidifying chemical has been added to the waste water.

10. An apparatus according to claim 9, wherein each at least one tank i) includes a stirring screw adapted to stir liquid in the tank.

11. An apparatus according to claim 9 or 10, further including a pulverizer adapted to pulverize the polyvinyl alcohol separated from the polyvinyl alcohol containing waste water; and a drying chamber adapted to dry pulverized matter discharged from said pulverizer.