EP0434994A1 - Process for rinsing the surface of workpieces treated in an aqueous activating solution and apparatus for performing the process - Google Patents

Abstract

The invention proceeds from a process for rinsing or spray-cleaning the surface of workpieces which have been treated in an aqueous activating solution (2) which functions in the cold without appreciable evaporation of its aqueous component. In this process a plurality of spray-cleaning or rinsing devices (3.1-3.3), arranged one behind the other, for the treated workpieces to be cleaned in a cascade are provided and fresh rinsing water is fed into the cascade, the flow direction (19) of said rinsing water being opposite to the direction of conveyance (4) of the workpieces. In order to make possible a mode of operation free of waste water and accompanied by negligible fresh-water requirement, the fresh rinsing water (20) is recovered from the aqueous activating solution (2) of the actual activating bath which performs the treatment and used rinsing bath solution (24), if necessary after purification and/or regeneration (32), is fed back to the activating solution (2) performing the treatment. The invention further relates to a system for performing said process.

Description

The invention initially relates to a method according to the preamble of claim 1. Such a method and a cascade arrangement are known from electroplating technology 77 (1986 No. 2, (pages 294 to 300). Although this method achieves a reduction in the consumption of rinse water, larger ones are incurred Amounts of wastewater that contain the entire amount of the towed active bath solution in diluted form that has to be treated. Such treatment can be very cost-intensive. There is also the risk of neutralizing salts and sludges in the sewage that is channeled into the sewage system Residual materials, such as heavy metal hydroxide sludge, accumulate in landfills. If these problems are not adequately observed, collisions with environmental protection regulations can arise. Especially the wastewater side has to be given more and more attention today, because here the costs for the above mentioned Disposal increase disproportionately. This is due to the fact that the permitted limits for the discharge of wastewater into the public sewer network are getting lower and, on the other hand, the taxes for discharge are increasing.

Galvanotechnik 78 (1987) No. 3 (pages 642 to 648) starts with an active bath that works at a relatively high temperature, e.g. 60 ° C, at which the water content of the active bath evaporates and is released into the environment. This arrangement and the method operated with it differ in this essential point from the preamble of claim 1 and thus from the procedure of the present invention. The version according to the last-mentioned literature reference requires suction devices and possibly also arrangements in order to separate chemical components contained in the evaporation so that they do not get into the environment. Fresh rinse water must also be constantly supplied. The mentioned consequences of evaporation, as well as the constant supply of fresh rinsing water require considerable costs. Contaminated rinse water is also fed from the first stage of the cascade, viewed in the direction of transport of the objects, to a device which concentrates this contaminated rinse water, the concentrate being fed to the treatment tank of the active bath and the separated water being fed into the feed of the fresh rinse water. As a result, the active bath solution dragged out of the active bath by the treated objects is returned to the active bath. So there is no waste water mixed with an active bath solution. A disadvantage, however, is the effort explained, which results from the fact that this arrangement or this method provides an active bath with a relatively high working temperature. These evaporation losses of the aqueous solution of the active bath are also necessary in the arrangement of this reference to the water-active bath mixture, which is concentrated from the aforementioned device, in the active bath container to be able to accommodate.

In contrast, the object of the invention is first of all to design a method according to the preamble of claim 1 in such a way that, while avoiding the disadvantages described, a wastewater-free mode of operation is possible when the fresh water requirement is negligible.

The solution to this problem is first seen, starting from the preamble of claim 1, in the features of the characterizing part of claim 1. Waste water is no longer generated in this cycle, as a result of which the above-described problems and expenses associated with waste water disposal are avoided. In particular, heavy metals do not accumulate or only in a very small residual proportion, which only insignificantly pollute the corresponding landfills. Rather, the active solution carried away by the objects from the active bath is rinsed back into the active treatment bath. There is also the advantage that practically no fresh rinse water has to be supplied since the rinse water required of the cascade is formed by the circuit present here. Only minor evaporation losses have to be replaced from time to time. Either water from the public supply network or treated, ie deionized or deionized water is used for this. When carrying out the method according to the invention, the rinsing process can either be carried out in an immersion sink or the aqueous active bath solution still adhering to the treated objects is rinsed off with the rinsing water in corresponding chambers via a spray device, the rinsing water being used here in a cascade-like manner in the various stages. In both of the aforementioned cases, the water contains rinsed or sprayed active bath solution, the proportion of which would increase continuously with the number of rinsing or spraying processes with the same amount of water, if not according to the preamble of claim 1 Active bath solution is brought out of the contaminated spray or rinse water. As already mentioned, the requirements for the effectiveness of the flushing or spraying are extremely high. The method according to the invention meets all these requirements and also has the advantage that its implementation is not dependent on the presence of a higher temperature, for example of 60 ° C., of the active bath, as is the case with previously known arrangements or methods (see e.g. Galvanotechnik 78 (1987) No. 3, pages 642 to 648) is the case. Rather, the method according to the invention will be used in cold working baths without significant natural evaporation of the water content of the active bath. These are usually temperatures up to 35 - 40 ° C. Working at such low temperatures, as already mentioned, has the great advantage that there are no evaporation losses in water and therefore there is no need for the disposal and removal of the evaporation and for the corresponding fresh water supply. Due to the removal of aqueous active bath solution to form fresh rinse water, space is created in the active bath tank in order to be able to return the amounts of contaminated spray or rinse water to the active bath tank. Since there is a closed cycle here, the amount of aqueous active bath solution withdrawn from the active bath tank is equal in quantity to the supply of active bath solution and a corresponding proportion of rinsing or spraying water in the active bath tank.

The invention also achieves the object of creating an arrangement for carrying out the method according to the invention. For this purpose, the features of claim 4 are initially provided. They represent an effective and at the same time simple arrangement for carrying out the method.

Fig. 1:

eine Schemadarstellung einer Anlage nach der Erfindung und des zugehörigen Verfahrensablaufes,

Fig. 2:

ein erstes Ausführungsbeispiel der Trenneinrichtung (Eindicker),

Fig. 3:

ein weiteres Ausführungsbeispiel der Trenneinrichtung (Eindicker).

Further advantages and features of the invention are both Further claims, as well as the following description and the associated, essentially schematic drawing of possible embodiments according to the invention. The drawing shows:

Fig. 1:

a schematic representation of a system according to the invention and the associated process flow,

Fig. 2:

a first embodiment of the separating device (thickener),

Fig. 3:

another embodiment of the separator (thickener).

In the active bath container 1 there is the aqueous active bath solution 2, in which the, for example chemical, treatment of the objects not shown takes place. This is followed by a rinsing group 3 in the direction of transport 4 of the goods, in the form of a cascade for immersion rinsing, which can also be followed by a rinsing station 5 in the direction of the arrow 4. The material to be treated is dipped into the active container 1 according to arrow 6 and removed after the treatment according to arrow 7 and introduced into the first immersion container 3.1 of the cascade 3 according to arrow 8 and washed around by the rinsing water therein in order to still work on the product or the objects to remove adhering residues of the aqueous active bath solution 2. The product is then removed from the immersion container 3.1 according to arrow 9 and immersed into the further immersion container 3.2 of the cascade according to arrow 10, in order to be removed after the flushing according to arrow 11 and to be immersed and rinsed off into the third immersion container 3.3 of the cascade according to arrow 12. This is followed by removal according to arrow 13 and use according to arrow 14 in the container 15 of the rinsing station, in order to finally be removed and transported away according to arrow 16 to become. In the circuit of the purge station 5, its water is only provided with a very small amount of active bath components which are separated from this water in an ion exchanger 7 and removed at 18.

After the material first enters the immersion container 3.1 of the cascade with the aqueous active bath solution attached to it, it can be seen that the relatively highest proportion of active bath in relation to the content of the immersion containers 3.2 and 3.3 is present in this immersion container 3.1. Fresh rinsing water at 20 is now introduced into the immersion container 3.3 in the counterflow 19 to the transport direction 4 of the goods. This reduces the proportion of active baths in the immersion bath tanks. The liquid flows over the overflow edge 21 from the immersion bath container 3.3 into the immersion bath container 3.2, over the further overflow edge 22 from the immersion bath container 3.2 into the immersion bath container 3.1 and finally from there via the overflow edge 23 and a line 24 to a collecting container 25, the function of which will be described below is explained in more detail. This results in the aforementioned reduction in the active bath content in these three immersion bath containers, in particular in container 3.1, the excess of the first immersion bath container 3.1, which is still relatively strongly mixed with active bath content, being removed as explained. When the goods travel from the active container 1 via the immersion bath container to the container 15 of the rinsing station, the same amount of liquid is carried in and out of the station in question in each case, if one disregards the small viscosity differences of the different liquids and assumes that that a treatment in aqueous solution has also taken place in front of the active bath container 1. In the above-mentioned stations, there is therefore equilibrium with regard to the amount of liquid carried in and out. However, the concentration of the active bath solution 2 in the individual stations differs. In the active bath Container 1 is the concentration Co 100%, which should be equated with the value 1.0. Experience has shown that in the three-stage rinsing group 3 the following concentrations or concentration ranges can be achieved with relatively little use of rinsing water 20:

It can be seen from this that between 95 and 99% of the active bath solution 2 carried over from the active bath container 1 can be recycled. The small remaining fraction of 1-5% is retained by the ion exchanger 17. Only this small amount is supplied to the respective wastewater system or landfill when the ion exchanger needs to be regenerated from time to time.

The extraction of the fresh rinsing water 20 from the aqueous active bath solution 2 according to the invention takes place according to the illustrated embodiment in a cycle as follows:

The aqueous active bath solution 2 with the concentration C₀ is e.g. by means of a pump via a line 27 to a separating device 28, which can generally be referred to as a "thickener". Examples of the structure and mode of operation of such separation devices 28 are explained in more detail in FIGS. 2 and 3.

Basically, the separating device 28 has the task of separating from the aqueous active bath solution 2 a water portion to be used as rinsing water 20, which then serves in the rinsing group 3 to rinse the active bath solution 2 from the treated goods. The rinsing water 20 obtained from the separating device 28 is conducted via line 29 to the last station (immersion bath container) 3.3 of the rinsing group. From here, as explained, it flows in a cascade direction 19 through the stations 3.2 and 3.1 to the collecting tank 25. The active bath solution 2 'reduced by the rinsing water portion 20 also flows into this collecting tank 25 via the line 30. The mixture of the overflow of the immersion bath container 3.1 and the active bath solution 2 'separated in the separating device is then returned to the active bath container 1 via the line 31 and the pump 26. It is advantageous that this mixture has approximately the concentration of the aqueous active bath solution 2. A regeneration unit 32 can be installed in the line 31 from the collecting container 25 to the active bath container 1, with which regeneration products and other harmful constituents can be removed from the circulated mixture conveyed by the pump 26.

According to the exemplary embodiment in FIG. 2, the “thickener” or the separating device 28 can be designed as a vacuum evaporation system 33 using a heat pump 34. For this purpose, a boiling chamber 36 is arranged in a housing 35 in the lower region, while a condensate chamber 37 is located in the upper region. The heat pump 34 in a known embodiment compresses the refrigerant vapor in its compressor, the temperature of which increases. This reaches the heating coil 39 in the boiling chamber 36 via the line 38, giving off heat. From this heating coil 39, the steam is guided to a cooler 40, in which the temperature of the steam is further reduced, so that it condenses. In the cooler 40, the heat can be released into the environment or can be used in another process. The liquid refrigerant is then expanded in the expansion valve 41 and fed to the cooling coil 42 designed as an evaporator. In it, it absorbs heat and thereby evaporates again.

This steam is sucked in again by the compressor of the heat pump 34, as a result of which the circuit is closed. The aqueous active bath solution 2 is circulated through the boiling chamber 36 and brought to a higher temperature by the heat given off by the heating coil 39. As a result, 2 water evaporates from this active bath solution. This water vapor rises up into the condensate chamber 37, where it is deposited on the cold walls of the cooling coil 42. The resulting condensate is passed to a distillate container 43, a water jet pump 44 being used for the pumping. This water jet pump also serves to generate a vacuum in the housing 35, as a result of which the evaporation of the water from the aqueous active bath solution 2 is promoted. The required amount of rinsing water 20 is removed from the distillate container 43 and passed to the rinsing group 3. The concentrated active bath solution 2 ′ separated from the water 20 by the thickener 43 is removed from the lower region of the boiling chamber 36 and fed to the collecting container 25.

Through the use of a heat pump, the energy expenditure for the evaporation of the water from the aqueous active bath solution 2 is considerably less than with direct heating, for example with electrical energy.

The energy consumption when using a reverse osmosis system for the extraction of the rinsing water 20 is even lower. Here it is only about 0.05 kWh per liter of water. The diagram of such a device is shown in the exemplary embodiment in FIG. 3. The reverse osmosis module 45 also has the task here of separating the rinsing water portion 20 that is discharged via line 29 from the aqueous active bath solution 2 supplied via line 27. The concentrated active bath solution 2 ′ reduced by the rinse water content 20 is returned to the active bath container 1 via line 30.

Other components of this device are the feed pump 46, the prefilter 47, the ultrafine filter 48 and the high pressure pump 49.

Claims (9)

Process for rinsing or spraying the surface of objects that have been treated in an aqueous, active bath solution that works cold without any significant evaporation of their water content, whereby several spraying or rinsing devices, for example immersion baths, are provided in succession for the objects treated and to be cleaned in a cascade and wherein fresh rinsing water is introduced into the cascade, the flow direction of which runs opposite to the transport direction of the objects, characterized in that the fresh rinsing water (20) is obtained from the aqueous active bath solution (2) of the active bath performing the treatment itself and that used rinsing bath solution ( 24), if necessary after cleaning and / or regeneration (32) is returned to the active bath solution (2) performing the treatment. A method according to claim 1, characterized in that aqueous active bath solution (2) is removed and separated into rinsing water (20) and concentrated active bath solution (2 '), the rinsing water of the cascade (3) and the concentrated active bath solution (2') being the treated active bath is supplied. Process according to claims 1 and 2, characterized in that the concentrated active bath solution (2 ') obtained by the separation is mixed with the overflowing rinsing bath solution (24) of the first cascade stage (3.1) in the transport direction of the objects and fed to the active bath. Arrangement for carrying out the method according to one of claims 1 to 3, characterized in that a discharge (27) from the container (1) of the aqueous active bath solution (2) to a separating device (28) in the form of a thickener, that of the separating device Line (29) of the separated water (20) leads to the last station (3.3) of the cascade (3) in the direction of transport of the objects and that from the separating device a further line (30) for the separated concentrated active bath solution (2 ') to the active bath container (1st ) or an intermediate collecting container (25). Arrangement according to claim 4, characterized in that the separating device is a vacuum evaporation system (33) with a heat pump (34). Arrangement according to claim 4, characterized in that the separating device is formed by a reverse osmosis system (45). Arrangement according to one of claims 4 to 6, characterized in that a discharge (24) of the liquid in this immersion bath container leads to the active bath container (1) from the immersion bath container (3.1) of the cascade located first in the transport direction (4) of the treated material. Arrangement according to one of claims 4 to 7, characterized in that the discharge (30) of the concentrated active bath solution (2 ') from the separating device (28) and the discharge (24) of the immersion bath liquid of the first immersion bath container (3.1) together into the collecting container ( 25) are introduced and that the mixture of these two liquids are fed from the collecting container (25) via a line (31) to the active bath container (1). Arrangement according to one of claims 4 to 8, characterized in that in the transport direction (4) of the treated material, the cascade (3) is followed by a rinsing station 5 with ion exchanger (17) for the treated objects.

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