HK1195599A - Permanent system for continuous detection of current distribution in interconnected electrolytic cells - Google Patents

Description

Persistent system for continuous detection of current distribution in interconnected electrolytic cells

Technical Field

The present invention relates to a current collecting bus bar comprising a plurality of electrode housings for receiving a plurality of electrodes in electrical contact therewith. Probes for measuring the potentials corresponding to those of the electrical contacts, which are established locally when the current passes through, are also connected to the bus bar. The invention further relates to a permanent monitoring system allowing continuous evaluation of the current distribution on each electrode of an electrolytic cell of a metal electrowinning or electrorefining plant.

Background

The current supplied to the cells of an electrochemical plant (with particular reference to metal electrowinning or electrorefining plants) may be distributed in a very different and non-uniform manner over the individual cell electrodes, thereby negatively affecting production. This phenomenon may occur for a number of different reasons. For example, in the particular case of metal electrowinning or electrorefining equipment, the negatively polarized electrodes (cathodes) are oftentimes withdrawn from their seats in order to allow access to the products deposited thereon, and then returned for a subsequent production cycle. This frequent treatment (usually performed on a very high number of cathodes) also often leads to an imperfect reset and a far from perfect electrical contact on these busbars, due to possible scale formation on the relevant seats. It is also possible that product deposition occurs on the electrode in an irregular manner, wherein the formation of a product mass gradient changes the profile of the cathode surface. When this occurs, an electrical imbalance condition is established due to the fact that the anode-to-cathode spacing is no longer constant along the entire surface: the resistance, which is a function of the spacing between each anode-cathode pair, becomes variable and thus exacerbates the problem of non-uniformity in current distribution.

Thus, the current can be split to each electrode in different amounts, both due to the poor electrical contact of the electrodes themselves with the current collecting bus-bars and the change in the cathode surface profile. Furthermore, even simple anode wear can affect the current distribution.

These non-uniformities in current distribution can lead to anode-cathode short circuit phenomena. In the event of a short circuit, current tends to concentrate on the shorted cathode, reducing the current to the remaining cathodes and severely hampering production, which cannot be recovered before the shorted cathode is disconnected from the cell.

Moreover, an irregular current distribution, in addition to causing losses in quality and productivity as described above, will challenge the integrity and lifetime of modern concepts of titanium mesh-fabricated anodes.

In the factory, the task of finding irregularities in the current distribution is a very complex task, given the high number of cells and electrodes present. Such detection in fact involves thousands of manual measurements, which are made by an operator with the aid of infrared or magnetic detectors. In the particular case of metal electrowinning or electrorefining plants, the operator performs such detection in a very warm environment and in the presence of acid mist (mainly containing sulfuric acid).

Furthermore, conventional manual elements used by operators, such as magnetometers or instruments with infrared sensors, only allow to locate large current distribution imbalances, since they actually detect imbalances associated with magnetic fields or temperature variations.

These manual or semi-manual systems have the disadvantage of not being able to work continuously, allowing only infrequent inspections to be carried out, and are very expensive.

There are known wireless systems for battery monitoring which, although they are permanent and work continuously, can only detect voltage and temperature changes of each battery and not of each single electrode. For the reasons explained above, this information is substantially inaccurate and inadequate as a whole. Furthermore, there are developed items whose purpose is to rely on the hall effect to continuously detect the current supplied to the individual cathodes by means of fixed current sensors: such sensors are active components that require a large external power source, such as a large battery pack.

Systems based on magnetic sensors are also known, however, they do not provide sufficient measurement accuracy.

For these reasons, there is a need in the industry for a technically and economically viable system for permanently and continuously monitoring the current distribution on all the electrodes installed in an electrowinning or electrorefining plant.

Disclosure of Invention

The present invention allows for continuous monitoring of the current distribution of thousands of electrodes in an electrochemical device (e.g., in a metal electrowinning or electrorefining device) without the use of externally powered active components and without requiring an operator to make manual measurements in an unhealthy environment by reporting the failure of one or more specific electrodes through an alarm system.

The invention additionally allows to cut off the current between the bus bar and one individual electrode by means of an electrical contact removal device.

The lack of active electronic components, such as infrared or magnetic sensors, provides a much cheaper and almost maintenance free system.

Various aspects of the invention are set out in the appended claims.

In one aspect, the invention relates to a current collecting bus-bar for electrochemical cells (for example, cells suitable for electrometallurgical plants), consisting of an elongated body having a uniform resistivity, comprising housings uniformly spaced for one or more optionally removable anodic and/or cathodic electrical contacts, the current collecting bus-bar further comprising probes for detecting the electric potential, connected to the bus-bar by fixing means corresponding to those electrical contacts established between the bus-bar and those electrodes housed thereon.

The term "housing" is used herein to denote a suitable seat suitable for housing and supporting the anode and the cathode, as well as facilitating optimal and optionally removable electrical contact points between the electrodes and the bus bar.

The inventors observed that by selecting a material suitable for the current collecting busbars characterized by a resistivity that is constant in all directions, a well-defined geometry of the electrode housings provided on the busbars and suitable electrical contacts between the busbars and the electrodes, the current that is distributed onto the electrodes can be directly correlated to the value of the potential difference that can be measured on the current collecting busbars.

In one embodiment, the current collecting bus bar is provided with a housing of one or more optionally removable anode and cathode electrical contact points arranged to be evenly spaced alternately in the longitudinal direction.

In a further embodiment, the current collecting bus bar is provided with housings of one or more optionally removable anode and cathode electrical contact points arranged evenly spaced apart in the longitudinal direction on opposite sides of the bus bar width.

It has also been observed that in an ideal system where a uniform amount of current is shared between all electrodes, the potential difference results to be constant for each pair of adjacent electrodes.

In the context of the present description, the term casing (with removable electrical contacts) is used to refer to suitable seats suitable for housing electrodes (anodes or cathodes) incorporating means for breaking the electrical contact between the electrodes and the bus-bars, for example devices comprising springs.

The current collecting bus-bar can be manufactured according to different shapes with the housings (positioned at equal distances along the length of the bus-bar); in one embodiment, the bus bar may have a sufficient width to allow for alternate positioning of the housings on two opposing sides along the length of the bus bar.

In another aspect, the invention relates to an apparatus comprising a plurality of electrolytic cells connected electrically in series with each other by means of current collecting busbars comprising one or more housings of optionally removable anode and cathode electrical contacts. The busbars further comprise probes for detecting electric potentials, which are connected to the busbars by fixing means corresponding to the optionally removable electric contacts.

In a further aspect, the invention relates to a system for continuously monitoring the current distribution in each electrode of an electrolytic cell as described hereinabove, comprising a plurality of current collecting busbars having a housing of one or more optionally removable anodic and/or cathodic electrical contacts, comprising a plurality of probes for detecting the electric potential, connected to the current collecting busbars by fixing means; an analog or digital data computing system that allows the current intensity value in each individual cathode or anode connected to an alarm device to be obtained; further comprising a processor adapted to compare the amperage measurement provided by the computing system for each anode and cathode with a set of predefined threshold values and to activate the alarm means whenever the calculated amperage measurement for any one anode or cathode does not correspond to said respective predefined threshold value.

In yet another aspect, the invention relates to a system for continuously monitoring the current distribution in each electrode of an electrolytic cell as described hereinabove, comprising a plurality of current collecting busbars having a housing of one or more removable anodic and/or cathodic electrical contacts, comprising a plurality of probes for detecting the electric potential, connected to the current collecting busbars by fixing means; an analog or digital data calculation system that allows to obtain the current intensity value on each individual cathode or anode connected to a remote controlled device for lifting the individual electrodes, optionally equipped with one or more springs; further comprising a processor adapted to compare the amperage measurement provided by the computing system for each anode and cathode with a set of predefined threshold values and to activate the lifting means whenever the calculated amperage measurement for any one anode or cathode does not correspond to said respective predefined threshold value, thereby disconnecting the individual non-corresponding anode or cathode.

According to various embodiments, the means of fixing the probes to the current collecting busbars may be selected between bolting and welding; these probes may consist of cables or wires.

The invention can also be implemented in the case of electrolytic cells having electrodes fed from one side and relying on an additional busbar on the other side.

The additional bus bars, also commonly referred to as compensation bus bars, are independent for the anode and the cathode.

Some embodiments of a bus bar according to the invention are described below with reference to the accompanying drawings, which have only the purpose of explaining the mutual arrangement of the different elements in a specific embodiment of the invention; in particular, these drawings will not be intended as scaled replicas.

Drawings

Fig. 1 and 2 show a three-dimensional schematic of three possible embodiments of the invention, comprising a current collecting bus bar, anodes, cathodes, electrode/bus bar contact areas, detection points associated with these contacts.

Figure 3 shows a schematic of an apparatus consisting of 3 electrolytic cells connected in series, each cell comprising 5 anodes and 4 cathodes.

Fig. 4 shows a schematic diagram including a compensating bus bar.

Fig. 5 shows a front view of one electrode in electrical contact with the current collecting bus bar (with relevant details shown in (5 a)) and a front view of one electrode without electrical contact (with relevant details shown in (5 b)).

Detailed Description

In fig. 1, a current collecting bus bar is shown, having a variable geometric profile 0, an anode 1, electrode/bus bar electrical contact areas 2, detection points 3 associated with the electrical contacts and a cathode 4.

In fig. 2, a current collecting bus bar 0, an anode 1, electrode/bus bar electrical contact areas 2, detection points 3 associated with these electrical contacts and a cathode 4 are shown.

In fig. 3, a schematic of an electrolysis apparatus is shown, which consists of: 3 electrolytic cells (cell 1, cell 2 and cell 3) electrically connected in series, each cell comprising 5 anodes (anode 1, anode 2, anode 3, anode 4 and anode 5), 4 cathodes (cathode 1, cathode 2, cathode 3 and cathode 4); an anode current collecting bus bar (bus bar 1); one cathode current collecting bus bar (bus bar 4); two bipolar current collecting busbars (busbar 2 and busbar 3); arrows indicate the direction of the current 6 and the potential detection point (a)_21-25、k_21-24、a_31-35、k_{31- 34}）。

In fig. 4, a schematic diagram of a cell is shown, which comprises a compensating bus bar (new anode balancing bus bar), the arrows indicating the direction of the main current (iinode Y) and the arrows indicating the direction of the compensating current (iinode Y).

Fig. 5 shows a front view comprising a bus bar 0, an electrode 1 in electrical contact therewith, means 7 for breaking the electrical contacts and details of the contact area where there is electrical contact (5a) and details of the same contact area where there is no electrical contact (5 b).

Some of the most important results obtained by the inventors are presented in the following example, which is not intended as a limitation on the scope of the invention.

Examples of the invention

An apparatus for copper electrowinning was assembled according to the schematic of figure 3. Three electrolytic cells, each comprising 5 anodes made of titanium mesh coated with catalytic layers based on iridium oxide and 4 copper cathodes, were electrically connected in series via two copper current collecting busbars having a trapezoidal base for the anodes and a triangular base for the cathodes (see figure 1). The 36 cables are then bolted to these busbars in correspondence with the 36 electrical contacts produced (two for each electrode). These cables are then connected in turn to a data logger equipped with a microprocessor and data memory programmed to activate an alarm connected thereto whenever a 10% difference with respect to the preset data is detected.

The method adopted for calculating the current split in this particular case is based on a model expressed by the following formula, in which the current I with respect to each anode and each cathode of the cell 2 is given by:

i (anode 1) = I' (k)₂₁,a₂₁)

I (Anode 2) = I' (k)₂₁,a₂₂)+I’(k₂₂,a₂₂)

I (Anode 3) = I' (k)₂₂,a₂₃)+I’(k₂₃,a₂₃)

I (Anode 4) = I' (k)₂₃,a₂₄)+I’(k₂₄,a₂₄)

I (Anode 5) = I' (k)₂₄,a₂₅)

I (cathode 1) = I' (k)₃₁,a₃₁)+I”(k₃₁,a₃₂)

I (cathode 2) = I' (k)₃₂,a₃₂)+I”(k₃₂,a₃₃)

I (cathode 3) = I' (k)₃₃,a₃₃)+I”(k₃₃,a₃₄)

I (cathode 4) = I' (k)₃₄,a₃₄)+I”(k₃₄,a₃₅)

Where I' and I "identify the current flowing through the portions of the current collecting bus bars contained between each pair of electrical contacts bridging each cathode and each anode.

Then for a general battery X, the following relationship applies:

i (Anode Y) = I' [ k ]_X(Y-1),a_XY]+I’(k_XY,a_XY)

I (cathode Y) = I' [ k =_(X+1)Y,a_(X+1)Y]+I”[k_(X+1)Y,a_(Y+1)(Y+1)]

The value of the resistance R between two adjacent electrical contacts of one bus bar is the same due to the homogeneity of the material and the structure of the current collecting bus bar.

When the difference in potential between two common adjacent electrical contacts is V, then the associated current is equal to 1/(RxV).

If I_totIs the total current and there are N cathodes and N +1 anodes per cell, then for a generic cell the following formula applies:

I_tot= Σ I (anode Y) (where Y ranges from 1 to N + 1) or I_tot= Σ I (cathode Y) (where Y is in the range from 1 to N + 1).

Throughout all cells: i is_tot=(1/R)x{∑V[k_X(Y-1),a_XY]+V(k_XY,a_XY) (wherein Y is in the range from 1 to N + 1) such that in each cell: 1/R = I_tot/{∑V[k_X(Y-1),a_XY]+V(k_XY,a_XY) Wherein Y is in the range from 1 to N + 1.

The same 1/R evaluation can be performed starting from those cathode currents in one cell.

This is done for all current collecting busbars.

In particular, for a single anode and a single cathode of a universal cell X, the following formula applies:

i (Anode Y) =1/Rx { V [ (k)_X(Y-1),a_XY)]+V(k_XY,a_XY)}

I(Cathode Y) =1/Rx { V [ k_(X+1)Y,a_(X+1)Y]+V[k_(X+1)Y,a_(Y+1)(Y+1)]}

Other models may be used by those of ordinary skill in the art, such as where a compensating bus bar is present.

In such a case, referring to fig. 4, if I (balanced anode) Y is the current received by the anode of the compensating bus bar (with the anode resting on the opposite side) and b_XIs the contact point between the compensation bus bar and the anode, then the following formula applies:

i (equilibrium anode Y) = Ib_X(Y+1),b_XY]-I[b_XY.b_X(Y-1)]

Then using R_bRepresenting the resistance of that part of the compensating busbar which is inserted between two adjacent electrical contacts, the following relationship is obtained:

i (equilibrium anode Y) =1/R_b*{V[b_X(Y+1),b_XY]-V[b_XY.b_X(Y-1)]And for these anodes the total current will be:

i (total current anode Y) = I (anode Y) + I (equilibrium anode Y).

The above description should not be taken as limiting the invention, which may be used according to different embodiments without departing from the scope thereof, and whose scope is only limited by the appended claims.

Throughout this specification and the claims of this application, the term "comprising" and variations thereof, such as "comprises" and "comprising," are not intended to exclude the presence of other elements, components or additional process steps.

Claims (11)

1. A current collection bus bar for an electrochemical device cell, the current collection bus bar comprising:

-an elongated body of uniform resistivity, said body comprising housings for one or more optionally removable anodic and/or cathodic electrical contacts, said housings being uniformly spaced apart;

-a plurality of probes for detecting electric potentials, said probes being connected to said current collecting bus-bar by fixing means in correspondence of said one or more electric contacts.

2. The current collecting bus bar of claim 1, wherein the housings for one or more optionally removable anode and cathode electrical contact points are alternately positioned in a longitudinal direction and evenly spaced apart.

3. The current collecting bus bar of claim 1, wherein the housings for one or more optionally removable anode and cathode electrical contacts are evenly spaced in the longitudinal direction and positioned on opposite sides of the bus bar width.

4. Electrochemical device comprising a plurality of electrolysis cells, said cells being electrically connected in series with each other by means of a current collecting bus-bar according to any one of claims 1, 2 or 3.

5. The apparatus of claim 4, wherein the plurality of batteries are electrically connected in series to:

-an anode end cell connected to the positive pole of a rectifier by means of a current collecting bus bar having housings for one or more anode electrical contacts; and

-a cathode end cell connected to the negative pole of a rectifier by means of a current collecting bus bar having housings for one or more cathode electrical contacts;

the current collecting bus-bar has a plurality of probes for detecting electric potential, which are connected to the current collecting bus-bar by fixing means in correspondence with the one or more electric contacts.

6. The current collecting bus bar of any one of claims 1, 2 or 3, wherein the securing means is selected from between bolting and welding.

7. The current collecting bus bar according to any one of claims 1, 2 or 3, wherein the probe for detecting electric potential is a cable or a wire.

8. A system for continuously monitoring the current distribution in each electrode of an electrolytic cell of an electrochemical device, the system comprising:

-a current collecting bus bar having a plurality of housings for one or more optionally removable anode and/or cathode electrical contact points, said bus bar comprising a plurality of probes for detecting electrical potentials connected to said bus bar by a fixing means;

-analog or digital calculation means for measuring the current intensity value on each individual electrode starting from those potential values detected by said probe;

-an alarm device connected to each electrode;

-a processor adapted to compare the current intensity measurement provided by said computing means for each electrode with a set of predefined critical values;

-means for activating said alarm device whenever said amperage result of any one electrode does not comply with said respective predefined critical value.

9. The system for continuously monitoring the current distribution in each electrode of an electrolytic cell of an electrochemical device according to claim 8, comprising:

-an alarm device connected to all electrodes;

-means for activating said alarm device whenever said amperage result of any one electrode does not comply with said respective predefined critical value.

10. A system for continuously monitoring the current distribution in each electrode of an electrolytic cell of an electrochemical device according to claim 8 or 9, comprising:

-means for lifting the individual electrodes;

-means for activating said lifting means whenever said amperage result of any one individual electrode does not comply with said respective predefined critical value.

11. The system for continuously monitoring the current distribution in each electrode of an electrolytic cell of an electrochemical device according to claim 10, wherein said lifting means comprises at least one spring.