EP0733724A1 - Apparatus for separating metals from metal containing electrolytes - Google Patents

Abstract

The appts. for precipitation of metals from electrolytes, in particular, those used for coating steel strip incorporates vertical coating cells arranged one after another. The strip to be coated passes from one cell into another via guide and/or current rolls. There is a gap between the vertical strip segments and vertically oriented anodes, while the direction of electrolyte flow points against the direction of strip motion. Two opposing walls of adjacent cells (2,3) take the form of anode plates (12,13) which bound a precipitation space (13) between them.

Description

The invention relates to a separating device for metals from a metal-containing electrolyte, in particular for coating steel strips, consisting of lined up vertical coating cells, in which the strip to be coated, which runs from an upper deflection and / or flow roller to a lower, deflecting roller and from there is guided to a further upper deflection and / or current roller, the strip section running downwards and upwards respectively passing a gap between vertically arranged anodes and being able to be acted upon by an electrolyte stream fed in by means of pumps, preferably in the opposite direction of the belt running.

Such a device has become known from EP 0 196 420 B1. Separate housings are arranged around the anodes forming the anode-cathode spaces or deposition spaces for both the downward and the upward band section, in which electrolyte flows are circulated separately via liquid jet pumps arranged in the space between the housing walls of the outer housing and the anodes be moved. By supplying the electrolyte flow at high speed in the opposite direction of the belt running, a turbulent counterflow that accelerates the electrolytic deposition is generated. The outer housing enclosing the two anode pairs is completely filled with electrolyte up to an overflow, which not only entails a higher energy requirement when circulating the electrolyte, but also makes the assembly, maintenance and repair of the coating cells more complex. In addition, there are no longer controllable or controllable flow velocities of the jet nozzles electrolyte injected by increased pressure; furthermore, it is impossible to prevent iron hydroxide sludge from accumulating on the bottom of the cell.

The invention is therefore based on the object of making a generic deposition device for the electrolytic deposition of metals, in particular zinc, from aqueous solutions of the metal salts simpler and more economical.

This object is achieved in that two mutually opposite walls of the coating cells are designed as anode plates and adjacent anode plates of successive coating cells delimit a deposition space. The deposition caused by electrical current is thus limited to a deposition space which is formed on the one hand from the insoluble anode plates of the parallel anode longitudinal walls of adjacent coating cells and on the other hand from closing plates which can preferably be pushed in and pushed out at the two lateral openings of the pair of anode plates. There is thus a box-shaped separation space open at the top and bottom, through the center of which, viewed in the longitudinal direction, the strip to be coated is passed parallel to the anode plates and to the side closing plates. The electrolyte, which is forcibly pumped in or through in the opposite direction to the tape running direction, only completely fills the two sub-spaces there with electrolyte, which is created by the tape passing through the box-shaped separation space between an anode plate and the tape. The two subspaces represent very flat rectangular channels.

Except in the sub-rooms, there is no electrolyte in the coating cell, which is thus in the form of a dry cell and allows a cassette construction of the coating system in a simple manner. Each coating cell or cassette can be designed as a complete functional unit and can be moved sideways out of the system in the shortest possible time with the strip in place. Inspections, adjustments and repairs can therefore be carried out Carry out outside the coating line or in a separate workshop. Furthermore, there is the possibility of replacing the drying cell in the shortest possible time by providing reserve or exchangeable coating cells in the event of malfunctions, which is accompanied by a considerable advantage in terms of production and maintenance costs. The coating cell according to the invention can be designed in an open frame construction, ie there are only lateral end walls, namely the anode plates of a coating cell lying opposite one another, while the end faces of the coating cell are open; the piping and distribution for the electrolyte flowing in and out into the deposition space or its two subspaces can extend in the space between the two anode plates. Alternatively, the coating cell can have a closed frame, that is to say also a wall provided on the front side.

One embodiment of the invention provides that inflow and outflow slots are arranged at the upper and lower ends of the anode plates and extend over the entire anode width. Whether the inflow point is at the top or bottom depends on the direction of the belt. The slots can advantageously be provided by slot nozzles, which can either be integrated outside, in front of the anode plates, or in the anode plates; in any case, they permit a flow velocity that is uniform over the full anode width and thus create a prerequisite for an even strip coating.

Redirection channels connected to the inflow and outflow slots are advantageously connected to inflow / outflow lines, which lead to a suction tank in which the vacuum required for suctioning off the electrolyte after flowing through the two subspaces of the deposition space can be set. The electrolyte emerging from the coating cells flows freely, arrives in a collecting trough and from there continues to flow freely into an electrolyte collecting container. From there it can be returned to the coating cells by the pumps. It is also possible to use the drip pan as a Use of electrolyte template for the pumps.

It is proposed that the narrow sides of the closing plates facing the band edges be provided with edge masks - known per se from DE 41 39 066 A1. While the closing plates that can be pushed in and pushed out completely seal off the box-shaped separation area on the sides, the edge masks, for example U-profiles that are open towards the belt edges, enclose the belt sides without contact. They shield the strip edges and prevent excessive coating there, e.g. made of zinc, and thus an undesirable bead build-up. The closing plates, on the other hand, are brought up to the belt edges on both sides and consequently reduce the separation or flow space to the respective extent of the bandwidth, which can vary; At the same time, they cover the inflow slots outside the bandwidth and thus ensure that the electrolyte only flows in the band area.

The anode plates are completely covered outside of the bandwidth by the closing plates which can be pushed in and out, like the edge masks made of electrically non-conductive material, so that in these areas there is also no current transmission from one anode plate to another, for example at different voltages of the anode plates. The adjustment and thus adjustment to the respective bandwidth of the locking plates with the edge masks they carry can be achieved via motor-driven threaded spindles or via swing arms designed as parallel links and connected to a drive. With a one-sided coating of the strip, the edge masks are of further importance if the anode plate that is not required is not switched off or is not removed in order to avoid coating the strip on the back. In order to avoid coating the de-energized, switched-off anode plate due to voltage differences in these cases, it has become known from DE 39 01 807 C2 to divide the de-energized anode plate horizontally and thus to interrupt any short-circuit currents.

According to a preferred proposal of the invention, a first coating cell carries the current roller, a second coating cell carries the deflection roller and the next coating cell again a current roller, etc. By alternating the two types of coating cells in series or in series, coating systems of any length, i.e. create any coating capacity. Each coating cell is identical with an electrolyte supply and two power connections (on / off). The current distribution and the electrolyte flow distribution to the respective slot nozzles are provided within the coating cell.

A further embodiment of the invention provides that the lined-up coating cells are locked together with quick-release fasteners. In the case of coating cells anchored to one another, possible thermal expansions in the longitudinal direction of the system can have no effect on the gap width of the anode or deposition spaces or on the parallelism of the current rollers to one another. The individual coating cells support each other, and no external support structure is required to absorb strip tensile forces.

It is advisable to provide splash walls that shield the coating cells from the side. Alternatively, it is possible to arrange the coating cells in a spray box. However, in the dry cells achieved according to the invention, liquid-tight and acid-resistant cell housings are neither required for the bulkheads nor for a spraying box, which also must be of high mechanical stability, as is the case with known coating systems.

If doors, in particular sliding doors, are advantageously arranged in the spray walls or in the spray box, the cassette design of the coating cells lined up next to one another also offers a simple way of inspecting the coating system during operation. For free access or access, namely, need the sliding doors are only pushed open accordingly; at the same time, a single coating cell can be easily moved out of the coating line to the outside with the sliding door open. For pure visual inspection, the spray walls or boxes could also be made of a transparent material.

According to a proposal of the invention, support and slide rails are arranged on the bottom of the coating cells, with which the coating cells used can be positioned or simply moved out of the coating line. It is recommended that lifting arms attack the bottom of the coating cells, which can be adjusted together by a motor, and make it possible to lift a coating cell that is set at a lower level in the coating line and positioned there for removal to a higher extension level.

Fig. 1

als Einzelheit einer Beschichtungsanlage im Längsschnitt drei aneinandergereihte Beschichtungszellen, deren Längswände aus Anodenplatten bestehen und von denen jeweils zwei einander benachbarte Anodenplatten aufeinanderfolgender Beschichtungszellen einen Abscheideraum einschließen, schematisch mit ihren Versorgungsleitungsanschlüssen zu einem Absaugetank und einem Vorratstank bzw. Umlaufbehälter dargestellt;

Fig. 2

in Kassettenbauweise aneinandergereihte und über stirnseitig angeordnete Riegel untereinander verspannte Beschichtungszellen in einer Seitenansicht;

Fig. 3

eine Vorderansicht einer Beschichtungszelle mit dieser links und rechts zugeordneten, ein- und ausschiebbaren, spindelverstellbaren Schließplatten;

Fig. 4

in einer Seitenansicht mehrere in Betriebsposition in einer Beschichtungsanlage eingesetzte Beschichtungszellen, die bodenseitige Auflager- und Gleitschienen zum Positionieren und seitlichen Herausfahren aufweisen;

Fig. 5

in der Vorderansicht als Einzelheit eine in einem Spritzkasten angeordnete Beschichtungszelle;

Fig. 6

eine Vorderansicht einer Beschichtungszelle für eine Breitbandbeschichtungsanlage mit Bewegungsmechanismen für die ein- und ausschiebbaren Schließplatten sowie zum Anheben der Beschichtungszelle von ihrer Einbauposition auf ein Ausfahrniveau, zum Ausfahren der Beschichtungszelle in die im rechten Teil von Fig. 6 gezeigte Ausfahrposition; und

Fig. 7

als Einzelheit eine Ansicht auf ein Anodenpaar mit zueinander verstellbaren Anodenplatten, im Bandkantenbereich mit Abdichtung der ein- und ausschiebbaren Schließplatte gezeigt.

Further details and advantages of the invention result from the claims and the following description, in which exemplary embodiments of the subject matter of the invention are explained in more detail. Show it:

Fig. 1

as a detail of a coating system in longitudinal section, three coating cells lined up in a row, the longitudinal walls of which consist of anode plates and of which two adjacent anode plates of successive coating cells each enclose a deposition space, shown schematically with their supply line connections to a suction tank and a storage tank or circulation tank;

Fig. 2

A side view of the coating cells that are lined up in a cassette design and braced to one another via bolts arranged on the end face;

Fig. 3

a front view of a coating cell with this left and right assigned, push-in and push-out, spindle-adjustable locking plates;

Fig. 4

a side view of a plurality of coating cells used in the operating position in a coating system, which have bottom-side support and slide rails for positioning and lateral removal;

Fig. 5

in the front view as a detail a coating cell arranged in a spray box;

Fig. 6

a front view of a coating cell for a broadband coating system with movement mechanisms for the retractable and retractable locking plates and for lifting the coating cell from its installation position to an extension level, for extending the coating cell in the extended position shown in the right part of Fig. 6; and

Fig. 7

As a detail, a view of a pair of anodes with mutually adjustable anode plates is shown, in the band edge area with sealing of the insertable and retractable closing plate.

Of a deposition device or coating system 1 for coating steel strips (not shown in detail), three vertically arranged coating cells 2 and 3 arranged in a cassette construction are shown in FIG. 1. While the coating cells 2 are provided with current rollers 4 at the top, the coating cell 3 at the bottom in the exemplary embodiment has a deflection roller 5, which is rubber-coated or plastic-coated to protect the belt. Nevertheless, it is within the scope of the system design to provide a current roller instead of a deflection roller, which leads to a Energy saving, less cooling effort per roll and because of the halved current could lead to simpler current rolls and current transfers.

The metal strip 6 to be coated with zinc, for example, passes through the coating installation 1 in the direction of the arrow 7 or 8 once upwards or downwards. The metal strip 6 is thereby guided by head and bottom, adjustable guide rollers 9 and 10 respectively. The outer walls of the coating cells 2, 3, which run parallel to the metal strip 6, are designed as anode plates 11, 12, and two adjacent anode plates 11, 12 of adjoining coating cells 2, 3 and 3, 2 respectively form a deposition space 13 which is passed through the continuous metal strip 6 is divided into two very flat, rectangular sub-rooms 14, 15. The coating cells 2 and 3 are closed on their narrow sides by end walls 16 which bridge the distance between the two opposite anode plates 11, 12 of each coating cell 2 and 3.

The deposition space 13 delimited by adjacent anode plates 11, 12 adjoining coating cells 2, 3 and 3, 2 is open at the top and bottom, while its lateral, left and right openings are arranged by sealing plates 17, 18 (see FIG. 3). are closed, which are formed on their narrow sides facing the band edges with edge masks 19 covering the band edges (cf. FIG. 7). Sealing strips 20 are assigned to the closing plates 17, 18, which extend over the entire anode height, e.g. Sealing lips which form a V-shape on the plate or inflatable seals, so that in any case a laterally completely closed seal of the closing plates 17, 18 which moves between the anode plates 11, 12 is achieved. This also applies if the distance between the locking plates 17, 18 according to the embodiment according to FIG. 7 is changed by means of a lever system consisting of levers 22 which are articulated on the one hand on the cell frame 21 and on the other hand on the anode plates 11, 12; Despite moving anode plates 11, 12, the lateral gap seal is retained.

The coating cells 2 and 3 are dry cells, because the electrolyte pumped in countercurrent to the direction of travel of the metal strip and forced through the deposition spaces 13 only fills the two subspaces 14, 15 separated from the metal strip 6. For supply of the deposition spaces 13 with the electrolyte are - because of the countercurrent supply according to the upward and downward arrows 23, 24 in the coating cells 2 and 3 in FIG. 1 - either inflow slits 25 or at the upper and lower ends of the anode plates 11, 12 Outflow slots 26 are arranged, which extend over the entire width of the anode. These are connected to the top and bottom diversion channels 27, which are connected to inflow / outflow lines 28, 29, which in the exemplary embodiment are supplied with the electrolyte from a storage tank or circulation tank 30, which is connected to a suction tank 31, for which purpose the pipes 32 pumps are arranged.

As can be seen from the side view according to FIG. 2, in which otherwise essentially only the inlet slot nozzles 25 for the electrolyte and the current and deflection rollers 4 and 6 mounted in support blocks are shown, the individual coating cells 2 and 3 are on the front side Arranged bars clamped together or with each other, so that thermal expansion in the longitudinal direction of the system can not have a disadvantageous effect. From Fig. 3, which shows the coating cells of Fig. 2 seen from the left, it can be seen in more detail that the closing plates 17, 18 have been moved there by means of a spindle drive 44 to the spacing dimension 6 corresponding to the smallest width Bmin of the metal strip; up to the maximum occurring bandwidth Bmax, the mutually opposite locking plates 17, 18 can be variably adjusted.

4, five coating cells 2, 3 are lined up and shown in their installation position, in which they rest on the base frame, not shown, with base-side support and slide rails 45, which is easily possible due to the coating cells which permit a cassette construction. The support and slide rails 45 make it possible, instead of expanding a coating cell 2, 3 vertically upwards, to move it out to the side, as can be seen in the right part of FIG. 6.

In the embodiment according to FIG. 5, the coating cells 2 and 3 are arranged in a spray box 46, which at the same time serves as a carrier for the storage of the current rollers 4 and the deflection rollers 5. Instead of protecting the immediate surroundings of the coating cells 2, 3 by means of a spray box 46, the spraying cells 47, in the exemplary embodiment according to FIG. 6, are assigned spray walls 47 which extend in the longitudinal direction of the coating system. On the one hand, for inspection of the system during operation and, on the other hand, for removing a coating point 2 or 3 by moving it sideways out of the coating line, as shown for coating cell 2 in the right part of FIG. 6, are in the bulkheads 47 - or at 5 integrated in the spray box 46 - sliding doors, not shown, which allow free access after opening.

In order to remove and extend the cell frame 21 with the anode plates 11, 12 and the current roller 4 arranged at the top, the coating cell 2 is raised from its installed position (cf. FIG. 4) to an extension level. It is then in alignment with a roller conveyor 48, on which the coating cell 2 can then be pulled out. In order to raise or lower the coating cell 2, lifting arms 49 which are pivotally movably attached to the bottom of the cell frame 21 and which are actuated by a drive 51, e.g. a cylinder drive, acted upon and adjusted.

FIG. 6 also shows another variant of a device for adjusting the locking plates 17, 18 to Bmin or Bmax or values in between, which differ from that in FIG. 3. This consists of a pair of parallelogram links 52 arranged to the left and right of the two adjacent anode plates 11, 12 forming an anode pair, which are pivoted by means of an air / hydraulic motor drive, whereby the locking plates 17, 18 adjust to the desired width dimension. The position of the parallelogram link pairs 52 drawn in solid lines corresponds to the maximum width Bmax of the metal strip 6 to be coated and to the inside pivoted-in, dash-dotted position corresponds to the smallest occurring width Bmin of the metal strip 6 to be coated.

Claims (12)

Separation device for metals from a metal-containing electrolyte, in particular for coating steel strips, consisting of vertical coating cells arranged in a row, in which the strip to be coated, which runs from an upper deflection and / or flow roller, to a lower, deflecting roller and from there to a further upper one Deflection and / or current roller is guided, wherein the strip section running downwards or upwards passes a gap between vertically arranged anodes and can preferably be acted upon by an electrolyte current fed in by circulation by means of pumps, in the opposite direction to the belt running direction,
characterized by
that two opposite walls of the coating cells (2; 3) are designed as anode plates (11, 12) and adjacent anode plates (11; 12) of successive coating cells (2, 3 and 3, 2) delimit a deposition space (13). Separating device according to claim 1,
marked by
At the upper and at the lower end of the anode plates (11, 12) arranged, extending over the entire anode width inlet and outlet slots (25, 26). Separating device according to claim 2,
characterized by
that connected to the inlet and outlet slots (25, 26) bypass channels (27) with inflow / outflow lines (28, 29) are. Separating device according to one of claims 1 to 3,
characterized by
that the side openings of the pair of anode plates (11; 12) insertable and retractable closing plates (17, 18) are assigned. Separating device according to claim 4,
characterized by
that the narrow sides of the closing plates (17) facing the band edges are provided with edge masks (19). Separating device according to one of claims 1 to 5,
characterized by
that a first coating cell (2) carries the current roller (4), a second coating cell (3) the deflection roller (5) and the next coating cell (2) again a current roller (4). Separating device according to one of claims 1 to 6,
characterized by
that the lined-up coating cells (2; 3) are locked together with quick-release fasteners (33). Separating device according to one of claims 1 to 7,
marked by
the coating cells (2; 3) are laterally shielded spray walls (47). Separating device according to claim 8,
marked by
doors arranged in the bulkheads (47). Separating device according to one of claims 1 to 9,
characterized by
that support and slide rails (45) are arranged at the bottom of the coating cells. Separating device according to claim 10,
characterized by
that attack on the bottom of the coating cells (2, 3) lifting link (49). Separating device according to one of claims 1 to 7 and 11,
characterized by
that the coating cells (2, 3) are arranged in a spray box (46).

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