DE2330200A1 - Oil droplets removed by ultra filtration - from spent cleaning, cooling or cutting liqs - Google Patents

Abstract

Oil droplets or suspended particles are removed from emulsions or dispersions respectively (used for cleaning purposes) by pref. repeated ultrafiltration, whereby substances having relatively low mol. wt. such as emulsifiers or some detergents, penetrate (together with water) the semipermeable membrane and can be recycled, whilst the emulsion or dispersion becomes enriched in oil droplets or suspended particles (such as soil particles) and, hence, can be more economically processed below the disposal. The process is used for the processing of spent cleaning, cutting or cooling liquids. The quantity of the recycled contaminated liquid is kept constant by adding fresh portions of the spent cleaning liquid in the same amt. as that of the liquid purified by the ultrafiltration and returned. When the contaminated liquid reaches the optional content of the impurities, it is withdrawn to a special tank.

Description

DiPL-ING. GRÄMK0V7 DR. MULLER-BCRE

DlPL-PHYS. DR. MANITZ DIPL-CHEM. DR. DEUFEL DIPL-ING. FI N STERWALD

PATENT LAWYERS 2330200

7 STUTTGART SO (BAD CANNSTATT) SEELBERGSTRASSE 23/25 ι -z C

Gr / Ka / Rö OD 66

Applicant ;

Otto Dürr, 7 Stuttgart 40 (Zuffenhausen), Spitalwaldstrasse

"Method for separating oil, suspended particles or the like. from emulsions or dispersions "

The invention relates to a method for separating oil, Suspended particles or the like. from emulsions or dispersions that are used, for example, for cleaning or other purposes. One such The process is particularly important for the surface treatment of metallic workpieces that are contaminated with oil are, for example in washing, cleaning, grinding processes or the like. Liquids are used here, for example, which contain emulsifiers, or to which such are added and thus have the ability to remove what adheres to the workpieces To absorb oil.

The service life, i.e. the useful life of such emulsions is limited:

a) by the oil absorbency, with a degree of saturation is also achieved when the

AO§ $ BS / Q $ 31

Receptivity is made; b) by the maximum permissible degree of pollution, which could interfere with the treatment process, e.g. in the case of mechanical contamination from metal chips, scaling or the like.

Usually after reaching the service life, for example at Reaching the maximum permissible oil and dirt concentration, the circulated treatment liquid, for example the cleaning, cutting or cooling emulsion, e.g. through Drain or destroy, discarded and must be exchanged for a new amount of treatment fluid. As a rule, however, valuable unused chemicals are lost in this process.

While it is possible to use these liquids or emulsions by various methods, but these methods are generally cost and wastewater quality unsatisfactory.

The main object of the invention is to reduce the losses of unused, usable chemicals and to increase the economic efficiency of the process and the plant. The invention accordingly consists essentially in that the liquid (emulsion) discharged from the treatment process, for example from a cleaning bath, is a preferably multiple ultrafiltration with filtering out small-

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molecular substance such as emulsifier and optionally active washing substance is subjected in the cycle. Through this it is achieved that the useful constituents that are still in the mixed with the oil or dirt particles Liquids are contained, are increasingly filtered out as a filtrate and the remaining residual liquid up is enriched with the oil and dirt particles to the maximum permissible or maximum possible degree of contamination.

Preferably this is made up of purified liquid and valuable unused chemicals in the filtrate again the treatment process, e.g. the cleaning or Wash nozzles or baths supplied.

In a preferred embodiment of the process according to the invention, the emulsion to be fed to the ultrafiltration is used collected before ultrafiltration and again after separating out the filtrate by ultrafiltration of the amount collected forwarded.

A particularly preferred implementation of the method is also that the collected - e.g. dirt or oil particles containing in increasing concentration - emulsion

(dirty)
in each case as much amount of / emulsion is fed back from the treatment process as is withdrawn from the amount in circulation by the ultrafiltration of filtrate. If necessary, the feed can take place in a continuous process. The inflow of emulsion to the amount collected can be controlled automatically.

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Ultrafiltration as such is known. It is a kind of reverse osmosis in which the to. filtering liquid is led past semipermeable walls under pressure. Small molecules, especially water and detergent substances that can still be used, as well as some of the emulsifiers built into the emulsions, pass through the membrane-like semipermeable walls, while the macromolecules, especially oil molecules and dirt particles, are retained. However, ultrafiltration differs from reverse osmosis in that it is more permeable. When the (dirty) emulsions enriched with oil and dirt particles are processed by ultrafiltration, an emulsion remains, as already mentioned, which is heavily enriched with oil and dirt particles. This oil and dirt concentration increases the more frequently the liquid remaining after the filtration is returned to the circuit and fed back to the ultrafiltration, while the clean filtrate from the ultrafiltration can either be diverted to the outside or used again for a new batch.

In this way, the originally relatively large amount is loaded with relatively small amounts of dirt and oil Amount of emulsion concentrated on a relatively small amount with a relatively large proportion of oil and dirt. Contains for example a collecting tank initially an amount of 20 cbm in the treatment process used emulsion with an oil and Dirt concentration of 1 g / l, so after a large number

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of circulations of the emulsion through the ultrafiltration device get an increasingly stronger concentration until, for example, the amount is 0.2 cbm with an oil and has reduced the dirt concentration of 100 g / l.

The invention will be explained in more detail with reference to the drawing.

Show it

1 shows an exemplary diagram for the concentration depending on the time,

Pig. 2 äas scheme of a plant according to the invention and FIG. 3 shows a variant of FIG. 2.

Fig. 1 shows the increase in the oil concentration c in one Collection container connected to a treatment device as a function of time t. For example, I will according to curve k, (theoretically a straight line) the maximum permissible value of the oil concentration after a standing time t. achieved. Once this value is reached, the bath is discarded, i.e. discharged to the outside or destroyed by incineration.

Removes a certain amount of the treatment liquid during the operating time and separates it from oil and dirt and replacing this amount with fresh water or purified water, the service life can be increased so that the maximum permissible concentration is only reached after a long period of time,

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for example, according to the curve kp after a standing time daily If the continuously withdrawn amount of oil so it is important that the amount of oil contained in the contaminated emulsion corresponds to the amount of oil supplied by the process, it can be achieved that a concentration value is set which is below the maximum permissible concentration value c "_",

Max

as this is indicated, for example, by the curve k ^. Theoretically, the service life can be increased to infinity, e.g. by approximating an asymptote, that of an optimal Concentration c ^ corresponds.

This result cannot be easily achieved with ultrafiltration alone. It is true that a highly purified liquid can be discharged as a filtrate through ultrafiltration; However, since the ultrafiltration does not separate oil, but rather retains it in the circuit, a treatment process can initially only take place in a specific cycle depending on the service life, for example with a service life t or t ₂ .

However, an almost continuous discharge of oil and dirt can be achieved by a system according to FIG. 2.

In the treatment device, e.g., a washing machine 10 with a liquid container 10a, objects to be degreased or treated in another similar manner are degreased or treated accordingly. A pump 11 can supply the treatment liquid (e.g. one mixed with an emulsifier

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Liquid or
/ Emulsion) in the circuit to the spray nozzles 12. The used treatment liquid, for example an emulsion enriched with oil and dirt particles, can be fed through a line 15 opening out at the bottom of the container 10a via a valve 14 to a collecting container 15, from which it is fed by a pump 16 via an ultrafiltration device 17 with one of the Liquid flowing through semipermeable membrane l8 and a line 19 is returned in the circuit to the collecting container. The membrane l8 arranged, for example, in a serpentine shape allows the small-molecule components of the liquid - except water, for example detergent substances - to pass through to the outside, whereupon they can be fed back to the treatment process of the washing machine 10 via a line 20 and a pump 21, while the membrane l8 High molecular weight constituents of the liquid that have not passed through, in particular oil and dirt particles, return to the collecting container 15.

If no new liquid, for example as a used emulsion from the treatment process, is fed to the collecting container 15, this would be emptied to a minimum amount in a relatively short time, with the remaining amount concentrating more and more. On the other hand, however, there is the possibility of refilling the collecting container 15 via the line 1J> with further used treatment liquid. So that a constant liquid level is maintained in the collecting container 15, a float control

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tion l4a provided for the valve l4, which is through the float is shut off as soon as the desired liquid level in the collecting container 15 is reached.

A cooling device 22 is used to cool the heated liquid located in the collecting container 15 Coolant, e.g. cooling water, supplied via a valve 23 will. After flowing through the cooling device 22, the cooling liquid is via a line 24 into the liquid container 10a of the washing machine 10 or the like. or also directed to the outside, as indicated at 25.

As a result of the ongoing withdrawal of filtrate, the concentration in the collecting container 15 accumulates up to the maximum permissible value c _ ". If this maximum value is reached, the concentrate is fed from the collecting container 15 via a line 2.6 with valve 27 and pump 28 to a concentrate draining container 29, whereupon the collecting container 15 is again filled with used treatment liquid. During the emptying time, which can, however, be kept very short and depends on the emptying speed, the continuous treatment process must be interrupted.

The treatment in the treatment device, e.g. washing machine 10, not having to interrupt, can also

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a system according to FIG. 3 may be provided. Same or equivalent Parts as in FIG. 2 are denoted by the same reference numerals, but increased by 100 in each case. the end the (not shown) treatment device is the used liquid, e.g. an oil-dirt emulsion, via the line 113 with a heat exchanger 130, e.g. for heating fresh water, that of the treatment device is fed to a shuttle valve Il4, from which the emulsion either via a valve 114A to a collecting container 115 or via a valve 114B to a collecting container 115B. Swimmers Il4a and 115b can again as in the previously described embodiment, the valves Control ll4A and 114b. In Fig. 3 it is indicated, for example, that the collecting container 115A is filled, the collecting container 115B is essentially deflated.

From the collecting tanks 115A and 115B, the liquid can be fed via drain lines 131A or 13IB to a three-way valve which feeds the liquid either from the collecting tank 115A or from the collecting tank II5B via the pump II6 of the ultrafiltration device II7. When passing through the semipermeable membrane of this device, which corresponds to the device YJ according to FIG. 2, the small molecular components of the oil-dirt emulsion are again filtered off as filtrate and, in the exemplary embodiment according to FIG , from which the filtrate is about

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a pump 1J4 can either be removed to the outside or fed back into the treatment device, for example washing machine 10. A float 135 controls the pump 1JÄ by putting it into operation when the container 133 is filled to the maximum permitted level and out of operation when it is filled to the minimum, as indicated schematically in FIG.

The liquid leaving the ultrafiltration device 117 after the filtrate has been separated off is fed to a 3-way valve from which the liquid is fed back either through a line 119A to the collecting container 115A or via a line 119B to the collecting container 115B. The valve is coupled to valve 132 in such a way that when line 119A is released, line 13IA is also released, lines 119B and 13IB, on the other hand, are closed or reverse control takes place. Floats 115a and 115b in the collecting tanks 115A and 11 ^{, respectively;} 5B can operate the pump II6 as a function of the liquid level in the collecting tanks. Lines 12βΑ and 126B can the gradually concentrating liquid in the collecting tanks 115A and 115B alternately via the changeover or »3-way valve 127 via the line 126 to the outside, in a container or the like. forward onto.

The alternate connection of the collecting container 115A and 115B, continuous operation can be achieved by using the valve during emptying of one container the other container is filled via the valve 114 or its contents can be gradually concentrated via the ultrafiltration device 117.

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Claims (1)

June 13, 1973 Expectations: 1. A method for separating oil, suspended particles or the like. off for cleaning or the like. Serving emulsions or dispersions, characterized in that the from the Treatment process discharged emulsion of a preferably multiple ultrafiltration with a filtering out of small molecular substance such as emulsifier and optionally detergent substance or the like. is subjected in the cycle. 2. The method according to claim 1, characterized in that the filtrate is fed back to the treatment process. 3. The method according to claim 1 or 2, characterized in that the emulsion or dispersion to be fed to the ultrafiltration collected before ultrafiltration and after separating out the filtrate by ultrafiltration of the collected Emulsion is fed again. 4. The method according to any one of claims 1 to 3, characterized characterized in that the collected - e.g. dirt or oil particles in increasing concentration containing emulsion in each case as much amount of emulsion is fed back from the treatment process as that in circulation The amount of piltrate present is removed by ultrafiltration. 409885/0531 5. The method according to any one of claims 1 to 4, characterized in that the feed of the emulsion to the collection amount is controlled automatically. 6. The method according to any one of claims 1 to 5 *, characterized in that that after reaching the maximum concentration in the collection amount, these are discharged and passed through a new collection quantity from the treatment process is replaced. 7. The method according to claim 6, characterized in that several collection quantities connected next to each other and alternately switched on in the treatment process. 8. Plant for carrying out the method according to one of claims 1 to 7, characterized in that the treatment tank (washing machine 10) is followed by a collecting tank (15J, 115A, 115B) serving to receive the emulsion to be discharged and connected to this by a circuit via an ultrafiltration device (17 ; 117) is connected. 9. Plant according to claim 8, characterized in that a or several lines (20; 120) the ultrafiltration system (17; 117) with the treatment tank (10) to the return line of the filtrate under the pressure of a pumping device (21,134). 409885/0531 -13- 233Q200 10. Plant according to claim 8 or 9 »characterized in that that with the collection container (s) (15; 115A, 115B) for the contaminated emulsion a control system (l4; ll ^ A, 114b) for automatic further feeding of soiled emulsion depending on the amount of the in the collecting container located emulsion mixture is connected. 11. Plant according to claim 8, 9 or 10, characterized in that the collecting container (15) for the soiled emulsion a drain container (29) is connected. 12. Plant according to one of claims 8 to 11, characterized in that that the collecting container (15) for the soiled emulsion is provided with a cooling device (22). 15. Plant according to claim 12, characterized in that the Cooling device (22) is operated with a cooling liquid to be supplied to the treatment emulsion. l4. System according to one of Claims 1 to 13 *, characterized in that that two collecting containers (115A, 115B) with a common ultrafiltration device (117) to alternate Connection to the treatment tank are connected in parallel to each other. 409885/0531 Blank page