METHOD AND DEVICE OF CONDUCTING A CLOSED CYCLE OF THE BATH FOR PLATING OF COATINGS

Abstract: The device for conducting a closed cycle of the electrop­ lating bath, especially in the process of electroplating, com­ prising an electrolytic tank, an evaporation device connected with the electrolytic tank through a device feeding the electro­ plating bath, is characterized in that in the electrolytic tank or in the vicinity thereof heating devices (17) are comprised and in the evaporation chamber of the evaporation device (10) there are no heating devices, the evaporation chamber (2) of the evaporation device is horizontal and comprises a partition (3), the inlet (1) of the bath to the evaporation chamber is situated on the opposite side in relation to the partition (3), the evaporation chamber (2) comprises a perforated conduit (6) or conduits and/or conduits having porous walls, the evap­ oration chamber (2) is connected from the side of the partition (3) with a separator (4), the upper part of the separator (4) comprises a drop catcher (7), and the lower part of the separator (4) comprises a conduit (5) taking off the concen­ trated bath to the electrolytic tank (9), the heating device (17) in the tank being connected to a temperature-control system (14, 15, 16) for control of the temperature of the bath.

Description: Method and Device of conducting a closed cycle of the bath for platinq of coatings The subject of the invention is a method of conducting a closed cycle of the both for plating of coatings, especially in the process of electroplating, and devices for conducting s closed cycle of the bath for plating of coatings, especiel iy in the process of electroplating. The known methods of conducting e closed cyc ie of the bath in the process of electroplating consist usually in conducting the evaporative process. It is most often aimed at evaporation of we- ter used for rinsing and at obtaining P concen trated solution of the composition corresponding to the composition of electropleting bath, after which rinsing follows. The known evaporative processes applied for this purpose are usually conducted at lowered pressure and indirect heating, most ofien at a raising film of the liquid. The application of vacuum is Pimed at lowering the temperPture of the process and at increasing the intensity thereof. This increases, nowever, the degres of difficulty of conducting the process and raises the cost of the process. Those skilled in the art konw al- so vacuum processes with forced circulation, of still higher degree of complication and additionally increased costs of conducting the process. Another method of conducting the evaporati- ve process is direct evaporation at atmospheric preaure. The feed is heated in an external heat exchanger, supplied upward to a column with n pack- ing, wherein it evaporates, flowing down in the counter-current in relation to the flowing air. It should be indicated that in all presently applied methods of evaporation the solution to be evaporated is heated in the evaporation zo- ne. Known devices for conducting the closed cycle of bath in the process of electroplating comprise usually an evaporator. This is mont often aimed at eveporation of sate used for rinsing and at obtaining a concentrated solution of the composition corresponding to the composition of electroplating bath, after shich rinsing follows. The know evaporators are, as e rule, vPcuum devices, with an external hesting chamber (indirect evaporators). Most often they are the so -called evaporetors with a raising film of the liquid (of the companie@ Pfaudler, Corning, Cos mos). The application of vacuum is aimed at lo wering the temperature of the process and at in creasing the intensity thereof. Thi± raises, how- ever, the cost of the device. Known also ere ve- cuum circulating evaporators (of the Simax com pany). Another group of the applied evsporators are direct evaporators, in which evaporation proceeds at atmospheric pressure (evaporators of the Lancy company). The feed is heated in the external heat ex changer, supplied upward to a column with n pack ing, wherein while flowing don in the counter -current in relation to the flowing air it evapo- rates. In ell presently applied methods of evepo- ration the heating chamber is an integrel part of the evaporator. The cost of hitherto applied methods and de vices is considerable, especially in the case of chemically aggressive baths, e.g. the chromium plating bath. In the case of aggressive baths, heating elements of the evaporetor should be made of special borosilicate glass (Simax company) or of special materials, e.g. titanium, tantalum,. Auxiliary equipment must be of special design (e.g. pumps) etc. F-or example, the cost of the evaporator of Corning company. of the yield of Q=67 1 of evapo rated liquid/hr is of the order of US # 20,000 (1977). Such a considerable investment cost, in spite of economic management of the whole enterprise and obvious effects of environmentpl protection, sets back the progress of the new technique of utili zation of wastes. The task of the invention is to work out p method and a device for pumping off the bath, comprising an appropriate evaporation device, so that it ifi possible to achieve the required evaporation of water from the system at the minimum costs. The method of conducting s closed cycle of the bath for plating of coatings, especially in the process of electropleting, consists in feed ing the bath from the electrolytic machining zone to the evaporation zone; nd'from the evapora- tion zone - efter concentration of the bath in the evaporation zone - back to the electrolytic machining zone, bnd according to the essence of the invention it is characterized by that the electroplating bath is heated in the electroly tic machining zone and" is introduced to the evaporation zone in which the bath is conducted in .e flow in a thin layer horizontally, whereby in the whole evaporation zone or only in e part the reof through the horizontally conducted bath air is conducted from below upwards by barbotage, eventually, the conducted air is heated and af terwards wet air conducted through the bath is taken off outside from the circulation after pre vious separation of entrained particles by the inertie method, and the concentrated solution from the evaporation zone ir led beck to the elec trolytic machining zone, the electroplating bath being made up in a continuous way by washings from a water washer for rinsing of objects after the said electroplating bath. According to the invention it i8 preferab- le that the electroplating bath is heated in the electrolytic machining zone, supplying in the said zone at least 25% of heat necessary for evepora- tion in the evaporation zone. In this case the re mining emount of necessary heat is supplied to air which passes through the bath in the evnpors- tion zone, by berbotage. according to the invention it i8 edviseble to introduce to the evaporation zone at least 55% of the volume of the electroplating bath. It is preferable, according to the invention, to introduce to the electroplating bath at least 55% of the volume of washings after rinsing of objects treated in the said electroplating bath. According to the invention it is advisable that the air taken off outside from the circule tion is used for mixing the rinsing water in wash- ers for washing the objects after the said elec troplating bsth. It is preferable, according to the invention, that the air taken off outside from the circulation, after adding water vapour thereto, is used for washing the objects after the said electropla ting bath. according to the invention it ie advisable tnPt from wet Pir conducted through the bath, taken off outside from the circulation, water is condensed off and said condensed-off water is @- sed as washing water in washers. The device for conducting a closed cycle of the bath for plating of coatings, especially in the process of electroplating, comprising an electrolytic tenk, an evaporation'device connected with the electrolytic tank through n device fedd- ing the electroplating bath, preferably an air lift pump-, according to the essence of the invention is characterized by that in the electrolytic tank heating devices are comprised, and in the evaporation chamber of the evaporation device there are no heating devices, the eveporation chsm- ber of the evaporation device is horizontal and comprises e partition whose height establishes the thickness of the layer of the liquid, the bath inlet to the evaporation chamber is at the opposite side in relation to the partition, the evaporation chamber comprises a perforated conduit or conduits and/or conduits with porous walls, through which air is supplied to the evaporated bath, eventually heated air, the evaporation cham ber is from the side of the par tit ion connected with a sepsrator, the upper part of the separator comprises a drop catcher through which wet air is taken off, and the lower part of the separator comprises a conduit taking off the concentrated beth to the electrolytic tank, whereby the hePt ine, device in the tenk is connected to the tem- perature-control system to control the temperature of the bath. It is preferable that the constructional ma terial for building the evaporation device is polyvinyl chloride. It is advisable that the drop catcher is of s labyrinth type and comprises air-flow guide ve nes. According to the invention only the bath is evaporated, and hest necessary to heat the liquid is supplied, in principle, only to the' bath in the electrolytic tank or in the vicinity thereof, with the use of the heating element being the standard equipment of the said tank, or only the Fir intro duced to the evaporation zone is heated. When the evaporator is assembled with the already operating electroplating equipment, we use the heating alement already existing in the electrolytic ma chining zone. Due to this, in newly designed lines we avoid doubling the heating elements. The method according to the invention reduces al so, the number of devices necessery for automatic control of the working parameters of the bath. If necessary for power reasons, additional hent- ing is employed, with the supply of heat power being the complement between the heat power of the already existing equipment and the heat power necessary to conduct evaporation with the re@ui- red yield. According to the invention, eveporation is effected directly, by letting the air pass through the bath being evaporated flowing in 8 closed channel, being in the phase of dynamic foam, Tile solution. according to the invention is described in the example of reelisetion by meens of the drawing of the exemplery device, which serves for realisation of the method. Fig.l presents a schematic device together with s washer and s feeding tank, and fig.2 presents schemetically e single' evaporation module applied for realisation according to the invention and merked in fig.l with number 10. The feed is supplied by e stub pipe 1, it flows by 8 flow pipe 2, overflows through s partition 3, and from e separator 4 is taken off by a stub pipe 8. In the evaporated solution, perallel to the axis of the pipe 2, a supply pipe6 of air is immeraed, said air, passing through the solution, causes barbotage and evaporation thereof. The drop catcher 7 arrests particles of the solution entrained by air. As materials for building the device polyvinyl chloride pipes are usually used. Such a solution has a number of advantages in relation to the axisting devices. The device and the method ere .charecterized by big design si@plicity, eesiness of execution, simple operation and failure-free work during use. On the basis of one standard module, such as shown in the example in fig.1, it is possible to build to the device According to the invention multi- -module evaporators of the required yield, usual ly to Pbout 100 l/hr of the evaporated liquid. Such evaporators require little space and can be easily compiled with the already operating electro plating line. In laboratory conditions the ope ration of one module of the evaporator presented in fig.l, of the length of the pipe 2 of D=70 and the length of the evaporation zone l=0.5 m. In the second experiment to modules of the evaporator were used for closing the material cir culation after chromium plating in a small elec troplating plant working in a semi-technical scale. Parameters of a single module. D=110 mm, l=1200 mm. As shown in fig.2, washings from washers 8 ere directed as a whole by e conduit 20 to en electrolytic tank 9. The rate ,of flow of the bath through the evaporator 10 is controlled by the vel- ve 11. The device tips an emergency overflow whose overflow conduit is marked in fig.2 with number 18. After evaporation, the bath is supplied by the pump 12 to the-feeding tank 13 wherefrom it flows to the tPnk 9. The temperature in the tank is con trolled by s tempereture-control system consist ing of elements 14, 15. 16, 17. The outlet of. air from the evaporation module is marked with number 19. Total evaporation from two modules connected parallely was 10 I/hr. It enables closing the ma terial circulation of the electroplating plant. Fig.2 does not @now ion-exchange columns whrough which washings flow in order to eliminate impurities, mainly ions Cr3+, Fe3+.

Claims: Patent Claims 1, A method of conducting a closed cycle of the beth for plating of coatings, especially in the pro cesp of electroplating, consisting in feeding the bath from the electrolytic machining zone to the evaporation zone, end from the eveporation zone after concentretion of the bath in the evapora tion zone back to the electrolytic' machining zone, characterized in that the electroplating bath is heated in the electrolytic machining zone and is introduced to the evaporation zone in which the bath in conducted in the flow in n thin film ho rizontally, whereby in the whole evaporation zo ne or only in a part thereof through the hori-. zontally conducted bath from below upwards air is conducted by barbotage, eventually, the air being conducted is heated, end afterwards wet sir conducted through the bath is taken'off outside from the circulation efter previous separation of entrained particles by the inertia method, and the concentrated solution from the evaporation zone is introduced back to the electrolytic ma- chining zone, and thereafter the electroplating' bath is made up in a continuous way with wash ings from the water washer for washing the ob jects after said electroplating bath. 2. @ method according to clais 1, characterized in that the electroplating bath is heated in the e lectrolytic machining zone, at least 25% of heat necessary for evaporation in the evaporation zo ne being supplied in trie said zone. 3. A method according to claim 1, characterized in thet to the evaporation zone at least 55% of the volume of the electroplating beth is fed. 4. A method according' to claim 1, characterized in that to the electroplating bath at least 55% of the vo lume of washings after washing of objects treated in the said electroplating bath is fed. 5. A method according to claim 1, characterized in that air taken off outside from the circulation is used for mixine of washing water ib washers for washing the' objects after the said electrople- ting bath. 6. A method according to claim 1, characterized in that air taken off outside from the circulation is, after adding water vapour thereto, used for washing the objects after the said electroplating bath. 7. A method according to claim 1, characterized in that from wet air conducted through the bath,, ta- ken off outside from the circulation, water is condensed off and said condensed-off water is used as washing waier in washers. 8. A device for conducting a closed cycle of the bath for plating of coatings, especially in the pro cess of electroplating, comprising an electroly tic tank, an evaporation device connected with the electrolytic tarik through s device feeding the electroplating bath, preferably an air lift pump, characterized in that , the electrolytic tank comprises heating devices (17) and in the evapora- tion chamber of the evaporation device (10) the re ere no heating devices, the evaporation chamber (2) of the evaporation device is horizontal and comprises s partition (3) whose height esteblish- es the thickness of the horizontal layer of the bath, the inlet (1) of the bath to the evapora- tion chamber is at the opposite side in relation to; the partition (3), the evaporation chamber (2) comprises a perforsted conduit (6) or conduits and/or conduits having porous walls, through whict to the evaporated bath air is fed, eventually hea ted air, the evaporation chamber (2) is connec ted from the, side of the partition with 9 sepa- rator (4), the upper part of the separator (4) comprises a drop catcher (7) through which wet air i8 taken off, and the lower part of the se- parator (4); comprises a conduit (5) taking -off the concentrated bath to the tank (9), the hest- ing device (17) being connected to the temDerature -control system (14, 15, 16) for controlling the temperature of the bath. 9. A device according to cleim 8, characterized' in that the constructional material to build the: evaporation device is polyvinyl chloride. 10. A device according to claim 8, characterized in that the drop catcher (7) is of the labyrinth type and comprises air-flow guide vanes.

Inventors: CICHOWSKI, DARIUSZ, CIECKO, PAWEL, KIESZKOWSKI, MAREK, WASIAK, RYSZARD, ZUBR, MACIEJ
Applicants: INSTYTUT MECHANIKI PRECYZYJNEJ
Application year: 1984
Main classification: C25D21
IPC codes: C25D21