CA2058008A1

CA2058008A1 - Jumper switch means and method

Info

Publication number: CA2058008A1
Application number: CA002058008A
Authority: CA
Inventors: Pierluigi Attilio Vittorio Borrione; Maurizio Marzupio; Gregory Jean Eldon Morris
Original assignee: Individual
Current assignee: De Nora SpA
Priority date: 1990-12-21
Filing date: 1991-12-18
Publication date: 1992-06-22
Also published as: AU8825191A; JPH04301090A; IT1246987B; ZA919566B; IT9022510A0; IL100265A0; PT99890A; HUT59967A; CS398791A3; BR9105476A; RU2076908C1; IL100265A; HU209837B; IT9022510A1; MX9102715A; PL292897A1; ATE145255T1; FI915926A; FI915926A0; PL167716B1

Abstract

NOVEL JUMPER SWITCH MEANS AND METHOD

ABSTRACT OF THE DISCLOSURE

An electric jumper switch means for electric current bypass of at least one electrolyzer consisting of individ-ual electrolysis cells, out of a plurality of monopolar electrolyzers connected in series to an electrical power source characterized in that said jumper switch means comprises a multiplicity of extension arms suitable for connection to the anodic contact point of each individual cell of the electrolyzer preceding the electrolyzer to be bypassed and a multiplicity of extension arms suitable for connection to the cathodic contact point of each individu-al cell of the electrolyzer immediately following the electrolyzer to be bypassed, Said jumper switch means comprises a resistor means to provide a uniform reduction of the current flow in the individual cells of the electrolyzer to be bypassed without a shift of electrical current in the adjacent cells of the electrolyzers immed-ately preceding and following the electrolyzer to be bypassed and a method of shutting down an electrolyzer in a series of electrolyzers.

Description

STATE OF TEE ART

Electrolyzers such as membrane electrolyzers of the chlor-alkali filter-press type for the electrolysis of sodium chloride a~e ~u~ceptihle to damage when disconnect.-ing one electrolyzer from a series of electrolyzers in a circuit. One type of damage affects the ele~trocatalytically active coating on the cathode surface o the electrolyzer to be bypassed and it is caused by reverse current flow; damage will also occur if excessive current passes through indiYidual cell~ of the electrolyzers adjacent to the electrolyzer to be bypassed as a consequence of shifting the current fl~w to those cell~ closest ta the bypa~s switch cannec~iDn~
A number of solutions to these problems~have been proposed such as in U,S. Patents No. 4,561,949 and No. 4,589,966 which. bqth de~cribe short circuit devices that permit partial or total flow of electri~ current to :be bypassed around an ~lectrolyzer. Both pate~ts provide a method to redire~t the.current aroun~ the electrolyze~
to be disconnected without creating a reverse current flow to the:~bypassed~ electrolyzer. HoweYer, neither patent:
provides a~ means for uniform flow ~of current from a plurality o~ cells o~a preceding adjacent electrolyzer to a plurality:of~cells in a following adjacent electrolyzer.

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, OBJECTS OF TH~ IHv~ roN

It is an object of the inventian to provide an apparatus for shutting down an electr.olyzer in a plurality of electrolyzers connected in series to an electrical power source, especially monopolar electrolytic electrolyzers for the electrolysis of aqueous ~olution~., which apparatus is capable to prevent the shift in current through individual cells of the electroly2ers adjacent to the electrolyzer to be hypa~sed and to pre~ent damage.to electrolyzers by avoiding reverse current flow.
It is a further object of the present invention to provide for an improved method for by-passing an electrolyzer in an~ multiplic ty of elect~olyzers by using the jumper switch means o~ the invention.
These and.other ob~ects and a~van~ges of the inven-:
tion will become obvious from the followin~ detailed description.

The~ novel electrical jumper switch meanB of the invention: f:or electric current bypass of at least one e1ectrolyzsr conslsting of individual electrolysis cells., out~of~a~plurslity;of monopolar electrolyzers connected in ': -:: . . . . .

series to an electrical power source characterized in thatsaid jumper switch means comprises a multiplicity of extension arms suitabl~ for connection to the anodic contact point of each individual cell of the electralyzer preceding the electrol~zer to be bypassed and a multiplic~
ity of extension arms suitable for connection to the cathodic contact point of each individual cell of the electrolyzer immediately following ths electrolyzer to be bypassed, said jumper switch means comprising a resistor means to prouide a uni~orm reduction of the cu~rent flow in the individual ~ells of the electrolyzer to be bypassed without a shift in electrical current in the adjacent cells of the electrQlyzer~ immediately preceding a~d following the electrolyzer to be bypassed.
Referring now ~o the drawings:
Figs. 1 and 2 illustrate a conve~tional short circuit switch of the prior art and the current flow therethrough.
Figs. 3, 4 and 5 schematically illustrate one ~:.
~ embodiment of the inventio~ consisting of an overhead . ~ ~
jumper switch means in a top, front (section X-X~ and side view respectively.

Fig.~6 is a pictorial view of the embodiment of figs.

~; 3, 4 and 5.

; Fig. 7 s a pictorial view of a second embodiment of ~, ~: , ~ , :~ : : :

, the invention of a jumper switch means located beneath the electrolyzers.
Figs. 8, 9 and 10 schematically illustrate three of the several alternatives for the internal electrical circuitry of the jumper switch of the invention directed to a~oid a shift of electrical current in the adjacent cells of the electrolyzers immediately preceding and following the electrolyzer to be bypassed.
In Figs. 1 and. 2, the conventional short circuit switch is intended to bypass electrolyzer 2 by connecting the short circuit switch to bus bars 6 and 7. This appara-tus does not prevent the shi~t. of electric current flow (i) towards the apparatus contact points at ~us bars 6 and 7. Fig. 2 illustrates the current flow in electrolyzers 1 and 3 just before and after electrolyzer 2 once the switch has been closed. The dashed current lines (i) indicate the increase of current flow of electrolyzers 1 and 3 closest to the switch contact point~, as a.-conse~uence of the shorter current path in bus bars 6 and 7.
Figs. 3, 4 and 5 schematically describe the top, front (section X-X) and side view of a serie~ of monopolar electrolyzers 1, 2 and 3, each contain~ng a plurality of . ~ :
ad~acently positioned electrolytic cells 4 and 5 and an overhead jumper switch means 8 directed to bypass : electrolyzer 2. The jumper switch means 8 is supported by :
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, ,: ' ~t ~ rJ ~;, supporting means 9 and 10 fixed to electrolyzers 1 and 3 and is connected to the anodic contact points 11 of each monopolar cell 4 of the immediately preceding electrolyzcr 1 by a multiplicity o~ extension arm~ 1~. The jumper switch means 8 is also connected to the cathodic contact points 14 of each monopolar cell 5 of the immediately following electrolyzer 3 by a multiplicity of extensiQn arms 13. In order to obtain a low-resistance connectiou between each couple of extension arms and anodic or cathodic contact point~, said.extension arms~ ~hich may be either rigid or flexible, may be provided in their lower ends with ~pring-located pincers. These last ones are forced ta pinch the strip-shaped anodic or cathndi~
contact points by the weight of the jumper ~witch means 8 itself. The jumper switch means 8 is also connected to a , : ; travelling cra~e., which allows for positioninq th~ jumper.
~switch means just above the electrolyzer to be by-passed in a series of several electrolyzers o~ a cell room of an ~ : industrial elec~r.olysis plant.
: : : Fi~. 6 is a pictorial view of the embcdiment ~chema-tized in ~igs. 3, 4 and S.
Fig. 7 is an analogous pictorial. view o~ a secQnd ~: :
embodiment of the invention wherein the jumper ~witch means 8 is positioned beneath the electrolyzers and is :; : :
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supported by a cart travelling along rails located just below each row of electrolyzers.
The remaining components are unchanged as well as the relevant numerals.
The electric current is directed from the monopolar cells 4 of the immediately preceding electrolyzer through the contact points 11 and the multiplicity of extension arms 12 to the jumper switch 8. The electric current then flows through resistor mean~ in the jum~er switch 8 to control the flow of electric current to the multiplicity of extension arms 13 and to the contact points 14 of the monopola~ cel- .e 5 o~ the immedia~eLy following electrolyzer 3. The curre~t is withdrawn progressively in equa~ portions from the mono~ol~r c~ls 4 and is fed in equal portiona to the monopolar ~ell~ 5 : in such a way the problems associated with shifti~g of the current previously discussed are completely overcome.
Figs. 8, 9 and 10 show three passiblQ arrangeme~s for the internal circuitry of the jumper switch means 8 of~
the invention.
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More particularly, fig. 8 shows that sxte~iQ~ arms 12 and 13 can be connected to bus bars 15 and 16 the cross area of which is by far larger than the ons o~ bus bars connecting the electrolyzers (numerals 6 and 7 in the preceding figures). This generously sized cross area ",~ :

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prevents any practically significant shift of current in the adjacent individual cells of the electrolyzers immedi-ately preceding and following the electrolyzer to be bypassed. The jumper switch. means 8 ic alsa provided.with two switch units 17 and 18 and a resistor means 19: once the extension arms 12 and 13 have been connected to the anodic and cathodic contact points. ~11 and 14 in fig~.
3-7) switch unit 17 is closed and part of the total electric current is bypassed through resistor means l9o The remaining minor paLt of the elect~ical cu~re~t still fed to the electrolyzer to be bypassed allows operat.ing conditions to be established in the electro}yzer so that . .
reverse cuLre~t is. preYe~t~d on a suh~e~uent shoGt-ciL-;cuiting sequence. After a suitable time after closing switch unit 17, switch unit 18 is also closed, allowing the complete by-passing o~ the electrolyzer without :
practically important reverse current orossing the electrolyzer itself.
~ An~alternative electrical cixcui.try is ill~trated in :: : Fig. 9: in this~ case the bus bars hav~ been divided in SUbUnltS 20, 21 and 22, 23 respectively, to which exten-sion arms 12. and 13 are connected. Each subunlt.which.is :;. eiectrically insulated from the other is;provided with switch units l24,~25 and 27, 28 respectively) and reslstor ~: :

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means (26, 29) to be operated as described ahove for the jumper switch of Fig. 8.
Dividing the bus bars in subunits avoids the shift of the electrical current mentioned above, without recurrin~
to the us~ of massive metal at the cost of some added complexity of the electrical circuitry.
Fig. 10 describes the circuitry of Fig. 9 in the extreme case where each couple of anodic and cathodic extension arms 12, 13 is connected to its own switch unit (30, 31) and resistor means (32) in a modular arrangement.
When using the parallel arrays of switch units and resis-tor mean~ desc~i~ed i n Figs. 9 and 10, the swit~hes are to be operated simultaneously (e.g. in Fig. 9: 24 and 27 and then 25 and 28).
To properly cQmprehend the inventiQn, it should be undexstood that resistivity is thP direct current (d.c.) ~,resistance between opposlte parallel faces of a portion of the materiaL ha~ing a unit lenght and a unit cross sec-tion.~ The resistivity of a material determines the elec-;, trical~ resistance offered by a material and resistance iscalaulated,acco~ding ta the formula:
R =pL/A (1) :
where~ ~ ~
R~- resistance~ln micro-ohms p =~resistivity in microohms.centimeter : ' 1 ~ :

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L = lenght in cm A = cross sectional area in cm2 Example of resistivity of several metals are as follows:
METAL RESISTIVITY (microohm-cm) aluminum 2.655 copper 1.673 cast iron 7~ - 98 lead 20.65 magnesium 4.46 nickel 6.84 steel 11 - 45 The voltage drop in a bus bar as identified ~y ~: numerals ~ and 7 in figures 1, 2, may be cal~ulated for the arrangement of ~ig. 1, where a conventional short :.
circuit switch is used to bypass electroIyzer~2,: and is giveD by :
: V = 0,5 R I (2) :where R;is as~deflned in equatio~ (1) above I is:the total current flowing through the electrolyzers.
Assuming a~total current~of 60.000 Amps, the~lenght L
equal to :200~ cm and the cross sectional area A e~ual to , :~ :
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100 cm2, the voltage drop V along the bus bar results to be 0,1 Volt.
It is for this reason that attaching a short circuit device of the prior art to one end o~ the bus bar 6 and 7 will cause a shift in current in those cells closest to the jumper switch contact points as illustrated in Fig. 2.
In those cases where the prior art taught the ufie of a switching device attached to bus bars 6 ~nd 7 as in U.S.
Patents No. 4,561,949 and No. 4,589,966, the electrolyzers were limited to a few monopolar cells to avoid an exces.-sive shift in current flow.
As can be seen, the electrical resistance can be minimized by ~ decreasi~g the.lenght of the current path; or (2) by increasing the thickne~s of the bus bars.
In both cases, the prior art is limited by practical consideratiQns. Therefo~e, the prior art will. always experience some shift in current.
With the jumper switch means of the present inven-~ : tion, current can be transferred uniformily from :. : electrolyzers comprising any numher of individual cell : units without causing a shift in electrical.currentO
... As a mat~er of fact the.electrical culrent is dire.ct-ly ~fed from: the individual cells of the electrolyzers ~ : :
through the ext:ension arms into the jumper switch means of ~ the invention without travelling across the bus bars which : :`: :: : :
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electrically connect the electrolyzers during normal operation. In additio~ the internal circuitry of the jumper switch means of the invention is designed to allow the portions o~ the total current which travel along the extension arms to be e~ual. This result is achieve~ ~y using the design alternatives. shown in Figs. 8, 9, 10, that is oversized internal bus bars, that is sized in order to give less than 50 mV ohmic drap, or internal bus bars divided into subunits, each one provided with switch and resistox means, individual switch and resistor means for each exten~ion a~m, this last. arrangeme~t allowing, as a further advantage a better con.trol of the heat generated ~y the electrical current~
With conventional jumper switches, the bypa~sed electrolyzer must be removed by lifting over the jumper switch along aside it which results in unsafe conditions for the workers.~ The electr.olyzer LS heavy and is a~ove the workers with the possibility of electrolyte which can : be 32~ caustic and chlorinated brine in chlor-alkali electrolysi~ leaking dQwn on the workers. The jumper switch also blocks access to and from the bypassed :electrolyzer. By placing the jumper switch of the inven-tion overhead or benea~h the bypassed electrolyzer, these problems are avoided and the electrolyzer may be kept at ground level and removed by a conventional fork-lift ~, :

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truck, for example. There is no risk of the electrolyzer dropping on the workers and access to the elec~rolyzer is open.
With the jumper switch means of the inventi.on, there is a saving cf up to 40% of copper since the bus bars connecti~g the electLolyzers can be designed just to transfer current between the electrolyzers and not to minimize the shift of electrical current in the individual cells of the electrQlyzers cause~ by prior art swi~ch means. Also, in view of the fact that the total current is divided into small portions per each extension arms, the voltage. drop alang the extensiQn arms i~ negligib.~Q.anl the connectio~ between each extension arm-and the relevant anodic or cathodic contact points may be of th~ friction type (e.g.. the spring-loaded. pincera mentio~e~ heore) rather than the bolted type re~uired by the prior art ~ .
switch means where the total high current flows therethraugh~ The prior art bolting is time consumi~g anl requires~ the workers to be between the operating :
~ e1ectrolyzers:for a longer period o~ time which is danger-:
;: ous.
: Another advantage of the jumper switch means of the invention is that there is no limit to the number of cells n the;electrolyzer to be ~ypassed.

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Various modifications of the apparatus and method of the invention may be made without departing from the spirit or scope thereof and it should be understood that the invention is intended to be limited only as defined in the appended claim~.

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Claims

1. An electric jumper switch means for electric current bypass of at least one electrolyzer consisting of individual electrolysis cells, out of a plurality of monopolar electrolyzers connected in series to an electri-cal power source characterized in that said jumper switch means comprises a multiplicity of extension arms suitable for connection to the anodic contact point of each indi-vidual cell of the electrolyzer preceding the electrolyzer to be bypassed and a multiplicity of exten-sion arms suitable for connection to the cathodic contact point of each individual cell of the electrolyzer immedi-ately following the electrolyzer to be bypassed.

2. An electric jumper switch means as defined in claim 1, wherein said jumper switch means comprises at least an internal bus bar, switch and resistor means to provide a uniform reduction of the current flow in the individual cells of the electrolyzer to be bypassed without a shift of electrical current in the adjacent cells of the electroLyzers immediately preceding and following the electrolyzer to be bypassed.

3. An electric jumper switch means as defined in claim 2, wherein said bus bar is sized in order to give less than 50 mV ohmic drop.

4. An electric jumper switch means as defined in claim 2, wherein said bus bar is divided in subunits.

5. An electric jumper switch means as defined in claim 2 wherein each couple of extension arms is provided with its own switch and resistor means in a modular arrangement.

6. An electric jumper switch means as defined in claim 1, wherein the connection between extension arms and anodic or cathodic contact points is friction type connec-tion.

7. An electric jumper switch means as defined in claim 1, wherein the extension arms are rigid.

8. An electric jumper switch means as defined in claim 1, wherein the extension arms are flexible.

9. In a method of electrically bypassing an electrolyzer in a plurality of monopolar electrolyzers serially connected to an electrical power source, the improvement comprising using the jumper switch means of claims 1 to 8.

10. The method of claim 9 wherein said electric jumper switch means is placed above the bypassed electrolyzer.

11. The method of claim 9 wherein said electric jumper switch means is placed beneath the bypassed electrolyzer.