SURFACE TREATMENT PLANT, PRECONDITIONING APPARATUS AND PROCESS FOR TREATING PROCESS MEDIUM AND/OR RINSING MEDIUM

Abstract

A surface treatment plant for treating objects, in particular vehicle bodies, has a thin film conversion process in which a ceramic thin film is applied to the objects using a process medium, a subsequent rinsing step in which the objects are rinsed with rinsing medium after the thin film conversion process, and a deionization plant which has a cation exchanger and a downstream anion exchanger and is configured for deionizing the process medium and/or the rinsing medium. For economical operation, the deionization plant is preceded by a preconditioning apparatus which is configured for removing complex anions which are formed and/or present in the thin film conversion process from the process medium and/or the rinsing medium. Furthermore, a corresponding preconditioning apparatus and a treatment process are described.

Claims

1. A surface treatment plant for treating objects, comprising: a) a thin film conversion process in which a ceramic thin film is applied to objects using a process medium, b) a subsequent rinsing step in which the objects are rinsed with a rinsing medium after the thin film conversion process, and c) a deionization plant which comprises a cation exchanger and a downstream anion exchanger and is configured for deionizing the process medium and/or the rinsing medium, wherein d) a preconditioning apparatus which is configured for removing complex anions which are formed and/or present in the thin film conversion process from the process medium and/or the rinsing medium is located upstream of the deionization plant.

2. The surface treatment plant according to claim 1, wherein the preconditioning apparatus comprises an anion exchanger which is configured for replacing the complex anions by other anions.

3. The surface treatment plant according to claim 2, wherein the anion exchanger of the preconditioning apparatus comprises a selective exchanger material.

4. The surface treatment plant according to claim 2, wherein the anion exchanger of the preconditioning apparatus is regenerated using a regenerating agent which has a pH of less than about 6.

5. The surface treatment plant according to claim 2, wherein the preconditioning apparatus comprises a further anion exchanger in addition to the first anion exchanger, so that the two anion exchangers are operated and regenerated alternately.

6. The surface treatment plant according to claim 1, wherein the preconditioning apparatus has a device for precipitating the complex anions from the process medium or the rinsing medium and also a subsequent separation device.

7. The surface treatment plant according to claim 1, wherein the rinsing medium from a plurality of rinsing tanks is fed to the preconditioning apparatus.

8. The surface treatment plant according to claim 1, wherein the surface treatment plant has a control unit which is configured for operating and regenerating the preconditioning apparatus in such a way that the complex anions go at most in an undamaging concentration into the deionization plant.

9. A preconditioning apparatus which is intended to be installed upstream of a deionization plant of a surface treatment plant and is configured for removing complex anions which are formed and/or present in a thin film conversion process of the surface treatment plant from a process medium and/or a rinsing medium.

10. A process for treating process medium from a thin film conversion coating process in a surface treatment plant and/or treating rinsing medium from subsequent rinsing steps, the process comprising the following steps: a) providing a deionization plant which comprises a cation exchanger and a downstream anion exchanger and is configured for deionizing the process medium and/or the rinsing medium; b) providing a preconditioning apparatus which is located upstream of the deionization plant and is configured for removing complex anions which are formed and/or present in the thin film conversion process from the process medium and/or the rinsing medium; c) removing complex anions from the process medium and/or the rinsing medium.

11. A Surface treatment plant for treating objects, comprising: a) a thin film conversion process in which a ceramic thin film is applied to objects using a process medium, b) a subsequent rinsing step in which the objects are rinsed with a rinsing medium after the thin film conversion process, and c) a membrane filtration plant which is configured for deionizing the process medium and/or the rinsing medium, wherein d) the membrane filtration plant is preceded by a preconditioning apparatus which is configured for removing complex anions which are formed and/or present in the thin film conversion process from the process medium and/or the rinsing medium.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0075] Illustrative embodiments of the invention will be described in more detail below with the aid of the drawings. The drawings show:

[0076] FIG. 1 a surface treatment plant having a deionization plant and a preconditioning apparatus according to the invention;

[0077] FIG. 2 a surface treatment plant having a deionization plant and a preconditioning apparatus according to the invention as per another illustrative embodiment;

[0078] FIG. 3 a surface treatment plant having a deionization plant and a preconditioning apparatus according to the invention as per a further illustrative embodiment.

DESCRIPTION OF PREFERRED EMBODIMENTS

[0079] While this invention is susceptible to embodiments in many different forms, there is described in detail herein, preferred embodiments of the invention with the understanding that the present disclosures are to be considered as exemplifications of the principles of the invention and are not intended to limit the broad aspects of the invention to the embodiments illustrated.

[0080] FIG. 1 shows a surface treatment plan denoted overall by 10 having a transport system 12 which conveys objects 14, here in the form of vehicle bodies, through the individual treatment steps of the surface treatment plant.

[0081] The extract shown in FIG. 1 from the surface treatment plant comprises firstly two rinsing tanks 16 and 18 which follow a preceding treatment step, for example a cleaning operation.

[0082] Furthermore, the surface treatment plant 10 for carrying out a thin film conversion process has a thin film conversion tank 20 which is here configured as dipping tank.

[0083] The thin film conversion process is followed by two rinsing steps in the form of a rinsing cascade. For this purpose, a spray rinsing tank 22 which is operated using overflow water from the subsequent rinsing tank 24, which is configured as dipping tank, is arranged downstream of the thin film conversion tank 20. The overflow water can overflow from the rinsing tank 24 into the spray rinsing tank 22 or be actively pumped.

[0084] The rinsing tank 24, on the other hand, is supplied with deionized water (DI water) from a conduit 26.

[0085] The conduit 26 is in turn supplied by a deionization plant 28 which produces the DI water and is therefore frequently also referred to as DI water plant.

[0086] The surface treatment plant 10 additionally comprises a preconditioning apparatus 30.

[0087] The preconditioning apparatus 30 is supplied with contaminated rinsing water 33 from the rinsing tank 24 via a discharge conduit 32. An outlet 34 of the preconditioning apparatus 30 is connected to a process water tank 36 from which the deionization plant 28 is in turn supplied via a conduit 38.

[0088] The process water tank 36 additionally has a process water feed conduit 40 via which process water from the municipal water supply or spring water can be introduced into the plant.

[0089] Finally, a wastewater conduit 42 leads from the spray rinsing tank 22 into a drainage system (not shown) or a physicochemical wastewater treatment plant of the facility.

[0090] The surface treatment plant 10 additionally has, as indicated in FIG. 1, a control unit 44 which is configured for monitoring and controlling the processes of the plant via various measurement positions 46, pumps 48 and valves 50.

[0091] The deionization plant 28 has a cation exchanger column 52 and an anion exchanger column 54 in its interior. Positively charged ions are replaced by hydrogen ions (H.sup.+ ions) by means of the cation exchanger column 52. In the downstream anion exchanger column 54, on the other hand, negatively charged ions are replaced by hydroxide ions (OH.sup. ions). Since the corresponding ion exchange materials become exhausted over time, they have to be regenerated from time to time. For this purpose, the deionization plant has a regenerating agent inlet 56 and 58 and also corresponding regenerate outlets 60 and 62 for each column.

[0092] In the illustrative embodiment of FIG. 1, the preconditioning apparatus 30 has an anion exchanger column 64 having a selective exchanger material. Here too, a regenerating agent inlet 66 and a regenerate outlet 68 are provided.

[0093] The surface treatment plant 10 operates as follows:

[0094] In the thin film conversion tank 20, the objects are coated with a nanosize ceramic layer. The chemicals used here comprise compounds of zirconium (Zr), titanium (Ti) and silicon (Si) as fluoride complexes. These are, for example, hexafluorozirconic acid (H.sub.2ZrF.sub.6), hexafluorotitanic acid (H.sub.2TiF.sub.6) and hexafluorosilicic acid (H.sub.2SiF.sub.6) or their readily soluble alkali metal salts and/or ammonium salts. Thin film conversion solutions in the form of (organo)silanes can also be used.

[0095] These compounds go by means of entrainment by means of the objects from the thin film conversion process into the two subsequent rinsing tanks 22 and 24.

[0096] In the preconditioning apparatus 30, the complex anions from the thin film conversion process which are present in the downflowing rinsing water 33 and comprise zirconium, titanium or silicon are replaced by other anions, with acid anions generally coming into question here. Thus, ion exchange of these complex anions which are problematical for the deionization plant 28 takes place by means of the selective exchanger material in the anion exchange column 64 of the preconditioning apparatus 30.

[0097] The acid anions then leave the preconditioning apparatus 30 together with the remaining rinsing water 33 via the conduit 34 and are introduced into the process water tank 36. From there, they go, optionally together with freshly introduced process water to maintain the total amount of liquid in the system of the surface treatment plant 10, into the deionization plant 28.

[0098] In the deionization plant 28, the cations are firstly replaced by hydrogen cations and the anions are subsequently replaced by hydroxide anions in a manner known per se, with anions which are unproblematical for the later regeneration being incorporated into the exchanger material of the deionization plant 28 by means of the ion exchange in the preconditioning apparatus 30.

[0099] The deionization plant 28 can thus be regenerated in a known way by the cation exchanger column 52 being regenerated under acidic conditions and the anion exchanger column 54 being regenerated under alkaline conditions. Thus, blocking of the ion exchanger material due to precipitation of the complex anions in the alkaline regeneration does not occur in the deionization plant 28.

[0100] To regenerate the anion exchanger column 66 of the preconditioning apparatus 30, a regeneration in the acidic or neutral range is carried out instead of an alkaline regeneration. For this purpose, regenerating agents which have a pH of less than 6 are used at the regenerating agent inlet 66 of the ion exchanger column 64. This can be achieved by means of acid ions of strong acids since these do not shift the pH, while acid ions of medium-strength or weak acids would increase the pH, as a result of which the complex anions would precipitate in the anion exchanger column 64 in the preconditioning apparatus 30.

[0101] Since, in the illustrative embodiment of FIG. 1, additional regenerate is formed in the preconditioning apparatus 30 compared to the prior art, FIG. 2 shows an illustrative embodiment which is improved in this respect, with components having a similar or identical function being denoted by the same reference numeral.

[0102] As can be seen from FIG. 2, the regenerate arising in the deionization plant 28 is fed at least in part as regenerating agent to the preconditioning apparatus 30.

[0103] For this purpose, both or only one of the two regenerate outlets 60, 62 of the deionization plant 28 are connected to a regenerate tank 70. The figure does not show a branching-off opportunity in order to discard regenerate instead of conveying it to the regenerate tank 70. The regenerate tank 70 is also joined to the regenerating agent inlet 66 of the preconditioning apparatus 30. This makes it possible to use regenerating agent a number of times and/or to reduce the installation costs.

[0104] For example, the cation exchanger column 52 can be regenerated using an excess of hydrochloric acid (HCl) as regenerating agent. In the first runnings of the regenerate, i.e. at the beginning of regeneration, the foreign ions from the cation exchanger column 52 are firstly present in high concentration. These first runnings of the regenerate can be discarded via the branching-off opportunity. The concentration of the foreign ions in the regenerate then decreases and the regenerate is then collected in the regenerate tank 70. However, the regenerate present in the regenerate tank 70 has a somewhat lower acid content, i.e. a somewhat higher pH, compared to the regenerating agent at the inlet.

[0105] The anion exchanger column 64 of the preconditioning apparatus 30 is then supplied with this less concentrated hydrochloric acid as regenerating agent.

[0106] A further possibility is to reuse the ions which are exchanged with the complex anions in the anion exchanger column 64 (for example Cl.sup. ions) and go via the process water into the deionization plant 28. This is possible because these ions firstly become absorbed in the anion exchanger column 54 during normal operation of the deionization plant 28 and are replaced by OH.sup. ions. During the regeneration, these Cl.sup. ions can be collected in the regenerate tank 70 from where they go back as regenerating agent into the anion exchanger column 64 of the preconditioning apparatus 30. This results in a circuit by means of which the regenerating agent requirement is reduced and, in addition, the process water consumption is decreased further.

[0107] However, additional instrumentation is necessary for regenerate monitoring and further introduction possibilities.

[0108] Finally, FIG. 3 shows a further illustrative embodiment in which the preconditioning apparatus 30 comprises a device 72 for precipitating the complex anions and a subsequent separation device 74, for example a sedimentation and/or filtration unit, for separating the precipitated solids off from the aqueous rinsing water 33.

[0109] In the case of this illustrative embodiment, the complex anions from the thin film conversion process which are problematical for the deionization plant 28 are precipitated from the rinsing water by addition of appropriate precipitating chemicals at a precipitant inlet 76. For example, the pH can be shifted into the alkaline range. It is also possible to use flocculants which assist flocculation of the solids.

[0110] The separation device 74 is connected to the process water tank 36 in which the process water is, as in the preceding illustrative embodiments, collected for further treatment in the deionization plant 28.

[0111] As can also be seen from FIG. 3, the rinsing water 33 can also be taken from the spray rinsing tank 22. This applies for all illustrative embodiments.

[0112] Depending on the design of the plant, a person skilled in the art is also free to employ combinations of the abovementioned illustrative embodiments.

[0113] Thus, it is, for example, conceivable in the illustrative embodiment of FIG. 3 to provide an anion exchanger column 64 corresponding to FIGS. 1 and 2 downstream of the separation device 74 in the preconditioning apparatus 30.

[0114] The rinsing water from a plurality of rinsing tanks 22 and 24 can also be combined.

[0115] Furthermore, it is in principle conceivable to treat the process medium of the thin film conversion process in a similar manner. This is because it can also be useful for the thin film conversion coating tank 20 for downflowing process medium to be treated and/or disposed of by means of a combination of preconditioning apparatus 30 and a deionization plant 28.

[0116] As a modification of the above illustrative embodiments, an activated carbon filter can be used in addition to or as an alternative to a gravel filter as prefilter upstream of the preconditioning apparatus. This can, as adsorptively acting filter, remove, for example, interfering surfactants, biocides and/or disinfectants. Depending on the specific use, an activated carbon filter can be provided especially when the DI water produced is not only to be recirculated to the rinsing process but also to be used in other process sections. An activated carbon filter downstream of the preconditioning apparatus and/or the deionization plant can also be advantageous.

[0117] Independently of the subject matter at the time of the invention, it has been recognized that a preconditioning apparatus according to the invention can advantageously also be provided upstream of a membrane filtration plant, e.g. a reverse osmosis plant, in order to remove complex anions. This is because the complex anions described can also cause malfunctions as a result of blocking of the membrane (also known as fouling or scaling). For this reason, water containing the constituents of the thin film conversion has hitherto not been conveyed through membrane filtration plants. Here too, an upstream preconditioning apparatus according to the invention could remove the interfering complex anions, which would make further deionization by means of the membrane filtration plant possible.

[0118] In the figures, the deionization plant 28 would then be taken to be a membrane filtration plant 28 having one or more membrane filters 52 and 54.

[0119] The applicant reserves the right to pursue these ideas further, for example in the context of subapplications.

[0120] In particular, an inventive idea can be regarded generally as removing complex anions from any water from surface treatment plants by means of an anion exchanger whose pH is regulated as described above in the context of a preconditioning step.

[0121] While this invention is susceptible to embodiments in many different forms, there is described in detail herein, preferred embodiments of the invention with the understanding that the present disclosures are to be considered as exemplifications of the principles of the invention and are not intended to limit the broad aspects of the invention to the embodiments illustrated.