3,972,795 Axial flow electrolytic cell

Patent Number/Link:

-United States Patent [19]

Goens et al.

[11] 3,972,795

[45] Aug. 3, 1976

[56] References Cited

UNITED STATES PATENTS

756,328 4/1904 Christy 204/275 X

[54] AXIAL FLOW ELECTROLYTIC CELL

[75] Inventors: Duane N. Goens, Golden, Colo.;

James L. Lake, Lakewood, Ohio

[73]

[22]

[21 ]

[52]

[51 ]

[58]

Assignee: Hazen Research, Inc., Golden, Colo.

Filed: Sept. 11, 1974

Appl. No.: 505,029

U.S. Cl•................................ 204/269; 204/270;

. 204/275; 204/284

Int. CI,2 C25C 3/08; C25e 7/00

Field of Search ..; 204/267,269,275,284,

204/290 F, 149, 152, 153,278,270

3,701,724 10/1972 Entwisle et al... 204/290F

3,778,307 12/1973 Beer 204/290 F X

Primary Examiner-John H. Mack

Assistant Examiner-A. C. Prescott

Attorney, Agent, or Firm-Sheridan, Ross & Fields

[57] ABSTRACT

There is provided a membrane-free axial flow electrolytic

cell in which the anodes and cathodes are perforated

and lie transversely of a conduit through which

an ion containing and conducting medium is pumped.

This device is especially useful in the electrolytic recovery

of metal values from acid leach solutions from

low grade ores, e.g., copper, and for the carrying out

of electrochemical reactions such as the production of

sodium hypochlorite or sodium chlorate from NaCl.

16 Claims, 8 Drawing Figures

>-I)

en g-

I-'

..w.

-.J

..N.

-.J

Fig_2

42 11111' 1m ~.

.CI.:l

!a (D

/0 IIII 'rmlI~1 -r /6'1-'·,'<~9d\ :=1

f""t-

>c::

<!Cl

I-'

-..,J

50~

52 56

Fig_4

Fig_l

Fig_3

26~;llliLlcOC rflI rBl ~~

24U ~1;lrl ~

QJ.1,llltf II Jj CQ'J lf1l .

u.s. Patent Aug. 3, 1976 Sheet 2 of 2 3,972,795

..J"

",.

10.0

~8.0

:.J g

-6.0

~4.0

..J2.0

..J

4.0 0 50 100. 150 200 250 300

CURRENT DENSITY I

ASF

Fig_6

2.0 3.0

COPPER CONC.,

gIL

Fig_5

1.0

\;50 ASF 100 ASF ....200 ASF

\ I,:" \ - - -

IV ~ ~ ....

If , fj"

J b ;y " I J V

QIf J / Cu S04 - VARIED

P V V H2S04 -5 gil

Fe2 (S04)3 - 0 -5 gil

0 / V FLOW - 60 ft Imin.

'"y

100

-0

~80

i:>

WSO

lL.

!t40

w20

0.::

::::> u

TO LEACH

CURRENT

DENSITY-IOOASF

v Cu CONC. giL

,15-.20

0 --....

" 5 I

-2 >UZ

LL Itl

0.::

0.:: a o 20 40 60 80 100

LfNEAR VELOCITY,

ft Imin.

----+""'-(-)

(+)---+---

Fig_7 /2

STORAGE

VESSEL

PUMP

FROM

LEACH

3,972,795

AXIAL FLOW ELECTROLYTIC CELL BRIEF STATEMENT OF THE INVENTION

Briefly stated, the present invention is in an axial flow

BACKGROUND OF THE INVENTION AND PRIOR electrolytic cell which comprises in combination an

ART 5 electrically non~conductivetubular conduit having end

Electrolytic refining and recovery of metal values closures for each end of the conduit, and each of the

from leach solutions is well known. The principal activ- end closures having an opening therethrough for pasity

in this area has been, however, in the better grades sage of an ion containing and conducting medium. A

of ore. Where the primary metal to be recovered is in plurality of electrodes is provided in axially spaced

too low concentration, e.g., in the case of copper less 10 relation within the conduit and transversly disposed

than about 0.5 percent by weight, it is uneconomical to across the conduit, each of the electrodes being prorecover

the copper and such ore is frequently passed vided with macro openings extending therethrough.

over as worthless. Too much material must be handled First bus bar means are provided which electrically

connect alternate ones of the electrodes. Second bus

for current prices to justify the effort. The prior art has 15 bar means isolated from the first bus bar means also are

reported it to be all but impossible to extract the last of provided for electrically connecting the remaining

the copper electrolytically at a profit. (See U.S. Pat. electrodes. When fluid is pumped through the tubular

No. 1,195,616, Column 3, Line 28). device and the alternate electrodes are connected to

Ordinarily in electroplating by electrolysis, the manu- opposite poles of a source of direct current, rapid flow

facture of the chlorine by electrolysis, and such other 20 of the ion containing and conducting medium through

electrochemical reactions it is desirable to have maxi- the apparatus with minimum pressure drop may be

mum current density for the most rapid exchange of achieved and quite surprisingly, in such an arrangeelectrons

and hence electrochemical reaction. How- ment the current drain is most heavy in the initial porever,

the intensity of the current used or the current tion of the apparatus where the concentration of the

density is directly proportional to the concentration of, 25 desired ion, for example copper ion, is found, and gradfor

example, the metal being recovered from the ion ually decreases in the direction of flow of the ion concontaining

and conducting medium. As the ion con- taining and conducting medium as the concentration of

taining and conducting medium is depleted of the metal the desired ion decreases. It is believed that this phebeing

plated, for example, the efficiency of the cell nomenon is observed because the ion containing and

decreases rapidly. It has, therefore, been common 30 conducting medium is moved through all of the e1ecpractice

to use a given cell at maximum current density trodes alternating between positively and negatively

until a predetermined concentration of the desired ion charged electrodes in the course of its axial movement.

has been reached or efficiency has materially de- The flow is essentially turbulent flow in order to minicreased,

and then transfer the partially spent ion con- mize the effects of build up of ion concentration adjataining

and conducting medium to another ceIl where a 35 cent the electrode surfaces which concentrations tend

lower current density is being applied. Alternatively, to reduce the efficiency of the electrode. Because of

the current density in a cell such as that first described the parallel arrangement of the alternating positive and

may be manually adjusted as the desired metal ion is negatively charged electrodes, the control of the voltdepleted

from the ion containing and conducting me- age at which the desired plate reaction occurs is reladium

so as to correspond more nearly to the strength of 40 tively simple, and the current drain along the circuit

that medium. This is impractical. Thus, it has been becomes a function of the concentration of the desired

common practice to utilize a series of individual cells ion in the ion containing and conducting medium.

using decreasing current densities in succeeding cells In a more specific embodiment of this invention,

until the ion being recovered is finally depleted at the there is provided an axial flow electrolytic cell in which

end of the series of cells. 45 an ion containing and conducting medium flows axially

The present invention solves these problems by pro- through perforated electrodes of alternating polarity at

viding an apparatus in which the current drain auto- flow rates normally greater than 5 ft./minute and which

matically decreases in an axial direction as the concen- comprises in combination a rigid electrically noncontration

of the desired ion in the ion containing and ducting tube of uniform circular cross section. Electri50

cally nonconductive end closures are provided for each conducting medium also decreases. In like manner end of the tube, each of the enclosures having an openwhere

an electrochemical reaction is being carried out ing therethrough preferably tapped to receive a suitas

the concentration of a desired product increases, able conduit for the passage of an ion containing and

and the demand for conversion of the raw material conducting medium into and out of the ceIl respecdecreases,

also the current drain will automatically 55 tively. A plurality of circular expanded metal elecdecrease.

This improves the efficiency of the overaIl trodes of one sign is provided in axially spaced relation

cell. to each other and circumferentiaIly engaging the side-

Also, the a~ial flow type ceIl of the present in~ention waIls of the tube, each of the electrodes of the said one

enables effiCient recovery of low concentratIOns of sign having terminal means radially extending theredesired

ions from the ion containing and conducting 60 from and projecting through the wall of the conduit. A

medium which concentrations were prior to this time first bus bar externaIly of the tube and electrically conthought

to be uneconomicaIly recoverable. The im- necting all of the terminal means of the one sign is

proved ceIls of the present invention have the advan- provided. Also, a plurality of circular expanded metal

tage in that a single ceIl utilizing an axial flow principle electrodes of the opposite signs are provided in axially

for the ion containing and conducting medium replaces 65 spaced and alternating relation with the electrodes of

the multiple cell procedure previously described, as the one sign. These electrodes of the opposite sign also

weIl as those where the electrolyte foIlowed a tortuous circumferentiaIlY' engage the sidewall of the tube and

path between and around a stack of electrodes. have terminal means radiaIly extending therefrom and

3,972,795

electrodes. There is thus provided a tubular conduit 10

formed of an electrically nonconducting material. Any

suitable material may be used for this purpose, the most

economical being a plastic material such as polyethylene,

polypropylene, polystyrene, polymethylmethacrylate,

or the like. Such resinous material may be

transparent, transluscent or opaque so long as it serves

as an electrical insulator. The conduit 10 may be of any

suitable length and may under certain circumstances be

flexible or formed in a spiral or circuitous path for the

purpose of conserving space. For most purposes, a

straight-through tubular member will be found satisfactory.

The tubular conduit lOis provided with end closures

12 and 14, and each having openings such as the opening

16 extending through the end closure 12. This is

conveniently internally threaded to receive a conduit

for passage of fluid through the end closure 12. A similar

drilled and tapped opening is conveniently provided

in the end closure 14. Enclosure 12 is provided with a

circular groove 18 dimensioned to receive one end of

the conduit 10. A suitable compressible gasket 20 or

seal 20 may be provided. As best shown in FIG. 2 the

end closure 12 is also suitably drilled preferably at 90°

intervals as at 22 to receive compression rods 24 which

are conveniently threaded at each end and provide in

combination with nuts 26 and washers 28 a suitable

means for compressively retaining the end closures 12

and 14 in sealing engagement with the extremities of

the conduit 10.

As previously indicated, the cell is provided with a

plurality of transversely disposed electrodes. As shown

in FIG. 1, a series of first electrodes 30 are provided at

uniformly spaced intervals, these electrodes being of

35 circular configuration as best shown in FIGS. 3 and 4

and desirably formed of expanded titanium metal. The

periphery of the electrodes 30 closely approximates the

internal periphery of the conduit 10, there usually

being provided a slight clearance 32 for ease of assem-

40 bly. Each of the electrodes 30 is provided with a radially

projecting terminal member 34 which extends

through the sidewall ofthe conduit 10 in a suitable bore

36. The outer or distal end of the terminal 34 is conveniently

threaded as at 38 to receive a nut 40 useful for

45 both the purposes of retaining the electrode 30 in

proper position within the cell body 10 and for providing

electrical contact with a bus bar 42. The clearance

between the opening 36 and the terminal 34 is conveniently

filled with a hardenable sealant 44 (FIG. 3). In

50 the embodiment shown in FIG. 1, seven electrodes 30

are provided. Depending upon the manner in which the

electrodes are ultimately connected, the electrodes 30

may be either cathodes or anodes. In like manner there

are provided in alternating relationship with the elec-

55 trodes 30 a plurality of second electrodes 46. The electrodes

46 are of similar design, construction and dimension

to the electrodes 30. Accordingly, the electrodes

46 are provided with radially outwardly extending

terminals 48 extending through bores 50 in the

60 sidewall of the conduit 10. The distal ends of the terminals

48 are threaded as at 52 to receive retaining nuts

54 for the purpose of securing the electrodes 46 to a

bus bar 56 of opposite polarity to the bus bar 42 when

the cell is connected in an electric circuit not shown.

65 As in the case of the first electrodes 30, there is provided

a plurality of electrodes 46 in alternating relation

with the electrodes 30. In the embodiment shown six

electrodes 46 are provided. The total number of re-

projecting through the wall of the tube. A second bus

bar electrically isolated from the first bus bar and lying

externally of the tube electrically connects all of the

terminal means of the opposite sign.

In the further discussion of the present invention 5

reference will be had to an "ion containing and conductingmedium".

This is commonly and perhaps inaccurately

frequently referred to as an electrolyte. It is

believed to be more correctly defined as a medium

which conducts ions or allows for ion transport and a 10

medium which also contains such ions. For example,

water, neglecting for a moment the slight degree of

dissociation of pure water, is an ion conducting medium.

Until it contains ions of a desired nature, e.g.,

copper ions, it is not an ion containing and conducting 15

medium.

Reference will also be had to the electrodes as being

"macro" porous. This is to distinguish the electrodes of

the present invention from the micro porous electrodes

which are formed from pressed graphite or from pow- 20

dered sintered metal and in which the pores are extremely

fine. In the present invention the electrodes are

conveniently formed of expanded metal, e.g. titanium

metal, in which the minor dimension is approximately

3/16 of an inch and the major dimension is approxi- 25

mately 5/16 of an inch. The effective surface area of

such an expanded metal electrode is nearly 80 percent

of a solid plate and yet it has an open area of at least

50%. Any other perforated means may be used, e.g.

drilled or punched openings through the electrode 30

which will provide a large amount of electrode surface

with minimum resistance to the flow of liquid therethrough.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention may be better understood by

having reference to the annexed drawings wherein:

FIG. 1 is a side elevation, partially cut away, of an

axial flow cell in accordance with the present invention.

FIG, 2 is a top plan view of the cell shown in FIG. 1,

and showing the bus bar connectors radially extending

from either side thereof.

FIG. 3 is a fragmentary cross sectional view of the

apparatus shown in FIG. 1 as it appears in the plane

indicated by the line 3-3 in FIG. 1.

FIG. 4 is across sectional view of the apparatus

shown in FIG. 1 as it appears in the plane indicated by

the line 4-4 in FIG. 1 and showing a circular expanded

metal electrode circumferentially engaging the sidewalls

of the conduit.

FIG. 5 is a graph showing at different current densities

the relationship between current efficiency and the

concentration of copper at very low concentrations of

the metal.

FIG. 6 is a graph showing the relationship of cell

voltage to current density.

FIG. 7 is a graph showing the effect of flow rate on

current efficiency at very low copper concentration.

FIG. 8 is a schematic diagram of a copper recovery

system utilizing an axial flow electrolytic cell in accordance

with this invention.

DETAILED DESCRIPTION OF THE DRAWINGS

Referring now more particularly to FIGS. 1 and 2,

there is here shown a preferred embodiment of the

present invention, FIG. 1 being partially cut away to

show the internal construction and arrangement of the

3,972,795

5 6

spectiveelectrodes is immaterial insofar as the present sulfuric acid and in the cases indicated with sodium

cell structure is concerned, but seven first electrodes sulfate. This solution was pumped through the appara-

30 and six second electrodes 46 has been found satis- tus such as shown in the annexed drawings, the temperfactory.

ature of the ion containing and conducting medium

In order to maint';lin the electrodes 30 in suitably 5 noted, the amperage and the time over which the curspaced

relationship to the electrodes 46 of opposite rent was applied. The voltage was determined and reelectrical

charge there is provided a plurality of spacing corded.

collars 58 of similar axial dimension and dimensioned In the course of the electrolytic reaction, using copfor

close sliding fit within the internal diameter of the per sulfate as the ion yielding material, copper would

conduit 10. The spacing collars 58 are also formed of a lO be deposited from the cathode as small particles of

nonconducting material which may be the same as or copper powder, a substantial portion of which remains

different from the nonconducting material used in fab- suspended in the ion containing and conducting mericating

the conduit 10. dium as free metal. Some of the copper, however, ad-

It should be noted that in the preferred embodiment hered to the electrode or became trapped within the

the spacing between the electrodes of opposite charge, 15 structure. In order to remove this electrode deposited

e.g. electrodes 30 and 46, is uniform throughout the copper, a solution of NH4C03.NH4 was circulated

axial length of the cell. Prior art structures have sought through the cell to dissolve metallic copper. Since this

to improve cell efficiency by varying the distance be- copper has also been recovered· by electrochemical

tween the electrodes in order to accommodate various 20 reaction from the solution, it was determined and

concentrations of the desired ion. This is not necessary added to the quantity of metallic copper separated

in the present structure and therefore renders more from the spent ion containing and conducting medium.

simple and less expensive the construction of the de- The following table tabulates the results of tests carvice.

ried out under varying conditions and with varying

In like manner the terminals 48 are suitably sealed 25 amounts of copper in the ion containing and conductagainst

escape of liquid through the bores 50. The jng medium at the start. The "total Cu" is the summaterminals

such as terminals 34, are suitably secured to tion of the amount of copper powder collected in grams

the expanded metal electrodes, e.g. electrodes 30, by and the amount of copper recovered from the

welding or soldering as at 60 in order to ensure ade- NH4C03.NH4 solution in grams.

quate electrical connection. As indicated above, alter- 30 The axial flow cell used in the following tests innate

electrodes 30 and 46 extend through opposite

sides of the cell defined by conduit 10. The terminals cluded nine cathode plates and eight anode plates. The

34 and 48 also extend through bores 62 and 64 in bus cell body was formed of 2 inch internal diameter by 1fs

bars 42 and 56, respectively. The bus bars 42 and 56 in inch wall Plexiglass tube with slots milled for the electhe

embodiment shown in the drawings, lie along oppo- trode peripheries and holes drilled for the terminals. 35

site sides of the conduit 10 and are out of electrical The end caps were formed of V2 inch Plexiglass with an

contact with each other. These are conveniently ce- annular groove for the end of the conduit and sealing

mented as by hardening cement strips 66 and 68 re- ring and drilled and tapped for Y:! inch pipe in the censpectively

to the external surface of the conduit 10. ter thereof. The bus bars were formed of copper and

The laterally extending portions of the bus bars 42 40 suitably drilled to receive the electrode terminals. The

and 56 may be secured by any suitable means not anodes were formed of expanded titanium. The cathshown

to the opposite poles of a source of direct cur- odes were formed of perforated titanium punched and

rent. ground to the proper size and having titanium termi-

In operation, an ion containing and conducting mate- nals. The cell was approximately 10 inches between

rial containing for example copper ions in solution, is 45 end caps, and the electrodes were spaced V2 inch apart

introduced to the cell through the end plate 12 and a alternating cathode-anode-cathode, etc. and terminatsuitable

conduit threadedly engaged in the threaded ing with a cathode.

bore 16. This material is pumped quite rapidly (at ve- The present cell has also been used to recover copper

locities normally greater than 5 ft./minute) in an axial from aqueous acid leach solutions of copper ore condirection

through the perforated electrodes 30 and 46. 50 taining copper in very low concentration, e.g. from

Where the concentration of the copper ion is at its about 0.1 to about 2 grams per liter. In such a case, the

highest adjacent the end cap 12, the demand for elec- ore which is at approximately 325 mesh is slurried with

trical current generated by the electrodes 30 and 46 the acid leach composition, and the slurry pumped

first encountered will be at the highest. As the ion through the axial flow cell of the present invention.

containing and conducting medium passes through the 55 Under suitable current density conditions such as those

cell and the copper ion concentration is decreased by set forth in the following table, dendrites of copper

the formation of suspended particles of metallic cop- metal will be formed on the cathodes. These can easily

per, the current demand called for by adjacent elec- be dislodged and recovered.

trodes 30 and 46 also decreases. At the lower end of In order to facilitate recovery of material such as

the cell as shown in FIG. 1 approaching the end plate 60 copper dendrites adhering to the electrodes, it is con-

14, the concentration of the copper ion and the ion templated that the cell shall be divisible into halves and

containing and conducting medium is virtually zero, held together by suitable clamps and seals. When it is

depending upon the length of the cell and the flow rate. desired, then, to clean the electrodes, the half shells

The following data and specific examples show re- may be separated, and the electrodes exposed for results

obtained with an embodiment of the invention as 65 moval of the deposited dendrites of metal. The elecshown

in the annexed drawings and using various ion trode spacing ranges from 0.25 to 1 inch and the voltcontaining

and conducting media. The test .solutions age at which the cell is operated is generally from about

were prepared by dissolving copper in water along with 2 to about 10 volts.

3,972,795

7 8

TABLE I

RUN ION CONTAINING & COND. MEDIUM COMPo FLOW RATE C.D. AMP. TOTAL Cu CATHODE RISE MAT.

NO. H2SO, Fe Na,SO, Cu gm/I gpm asf HRS. gms. EFF TEMP BAL. '7c

Start Finish rk 0c. *

I 5 0 15 0.1'15 0.170 4.6 100 50 1.6 2.6 2 75.6

2 5 0 15 0.1'15 0.141 6.'1 100 50 4.7 8.1 2 87.8

3 5 0 15 0.1 '12 0.130 '1.2 100 50 6.3 10.6 101.0

4 5 0 15 0.2'12 0.085 9.2 200 170 21.5 10.7 8.5 103.9

5 5 0 15 0.288 0.157 '1.2 ;WO 85 '1.8 9.8 5.5 75.0

6 5 0 15 0.2'16 0.073 '1.2 50 47:5 1'1.7 35 1.0 88.5

7 5 0 15 0.2'14 0.235 '1.2 100 25 4.6 16 77.2

8 5 5 0 0.291 0.117 '1.2 50 47.5 14.7 27 0 '18.9

'I 5 0 15 0.278 0.053 '1.2 50 50 22.9 45 101.9"

10 5 5 0 1.890 1.430 '1.2 100 41.7 52.7 '10 2.0 114.6

II 5 0 I.R'IO 1.510 '1.2 200 100 34.6 70 '11.0

12 5 0 0.96'1 0.750 '1.2 50 21 23.7 '16 100.7

13 5 0 1.120 0.921 '1.2 100 21 16.3 66 1.0 82.1

14 0 15 0.'150 0.789 '1.2 100 21 15.7 63.5 1.0 97.7

*Matcrial Balancc '7c = 100 X gms Cu Powdcr + .gms Cu leached

Total Cu In soln.

**Rased on eu Powder recovered alone

In conventional copper electrowinning current densities

are normally 15-25 ampereslsq ft at copper concentrations

of 30-45 gil. The ratio of ASF to Cu is

25 limited to 0.5 to 1.0 over a wide range of copper concentrations.

Techniques such as directed flow of electrolyte, air

sparging, ultrasonic agitation, and mechanical wiping

have all been used to increase the copper mass trans30

port and thereby permit higher current densities. ASF:

Cu ratios as high as 2-7 have been achieved.

Copper powder has been produced in the axial flow

cell at ASF ratios in the range of 50-70. This ratio is of

significance in the field of copper electrowinning. As

35 will be noted in the following Table II in the electrowinning

of conventional copper per liter, the normal ASFICu

ratio is 0.5 to I. New techniques have improved the

ratio by a factor of up to 7. In the case of the very low

concentrations we are able to use, we are able to realize

ratios of up to 100 times those conventionally obtained

and from 7 to 10 times those of improved techniques.

TABLE II

25 - 400 ASF

20 - 30°C.

4.6 to '1.2 gal./min.

30 to 50 ft./min.

DSA

Titanium. or stainlcss stccl

0.1 to 2.0 gms/liter as Cu

5 gms/liter

o to 15 gms/liter

5 gms/liter

to one liter

CuSO,

H2S04 Na,SO,

Fe,(SO,h

Water

Anodcs

Cathodc

Current density

Temperature

Flow rate

Typical conditions for electrolysis in the specific

apparatus above described are as follows:

A typical composition for the ion contammg and

conducting medium for recovery of copper at low concentrations

is as follows:

In operation, copper forms as a powder on the cell

cathodes. It sloughs off and is carried through the out-

Copper Electrolysis Conditions

Cu H,SO, Current Density

g/I gil amp/ft'

ASF/Cu

Conventional

New techniques

Axial flow

30 - 50

0.2-2.0

150-300

5.0

15 - 25

30 - 300

50 - 200

0.5 - 1.0

1.0 - 7.0

50 - 70

TABLE III

The axial flow cell design does not permit the convenient

installation of a membrane or diaphragm therefore

it's principal application will be in those situations

where one-compartment cells are satisfactory. There

55 are several of those applications in the minerals industry

and also in the industrial chemicals industry. These

are tabulated in Table III.

let end 14 with the copper depleted ion containing and

conducting medium and collected in a thickener (see

FIG. 8). Overflow from the thickener 11 may be recycled

or directed to the leach bed and ultimately returned

to the system for passage through the axial flow

cell 10 diagrammatically shown in FIG. 8. Oxygen gas

also disengages in the thickener and is available for

recovery.

Experimental results are tabulated in Table I above. 60 _P_r_oc_e_ss_'A_pp_l_ic_a_tio_n E_le_c_tr_o....:ly_te_Sy:....s_te_m _

FIG. 5 illustrates the inter-relationship of copper con- Copper powder recovery Heap or dump leach liquors

centration, current density and current efficiency. In from copper oxide. Electrolyte

strip liquors.

calculating the copper concentration for plotting the Slurry electrolysis of mixed

points in FIG. 5, the average between the inlet copper oxide and sulfide copper.

concentrati.on and the out et cioncent'ration was used. 65 Electrooxidation Ocorveesrylurorfysailnvder,brginoled.fomr orley--

FIG. 6 shows the current density-cell voltage relation- bdenum, rhenium. lead-zinc.

ship. The effect of flow rate on current efficiency at Hypocholn'te generat'Ion sanead wmaetreCrUtrrYe·atment.

very low copper concentrations is shown in FIG. 7. Sewage treatmen!.

3,972,795

9 10

TABLE III-continued b. electrically nonconductive end closures for each

end of said tube, each of said end closures having

Process Application Electrolyte System an opening therethrough for passage of an ion-con-

Sodium chlorate production Sodium chloride brine. taining and conducting medium;

Sodium perchlorate production Sodium chlorate brine. 5 c. a plurality of circular expanded metal electrodes of

one sign in axial spaced relation and circumferentially

engaging the side wall ofsaid tube, each of

What is claimed is: said electrodes of said one sign having terminal

1. An axial flow electrolytic cell comprising in combi- means of the one sign radially extending therefrom

nation: 10 and projecting through the wall of said conduit;

a. anelectrically nonconductive completely closed d. a first bus bar external of said tube and electrically

conduit; connecting all of said terminal means of the one

b. end closures for each end of said conduit each of sign;

said end closures having an opening therethrough e. a plurality of circular expanded metal electrodes of

for passage of an ion-containing and conducting 15 the opposite sign in axially spaced and alternating

medium; relation with said electrodes of the one sign, said

c. a plurality of electrodes in axially spaced relation electrodes of the opposite sign also circumferenand

transversely disposed across said tubular con- tially engaging the side wall of said tube and having

duit, each of said electrodes having macro open- terminal means of the opposite sign radially exings

extending therethrough; 20 tending therefrom and projecting through the wall

d. first bus bar means electrically connecting alter- of said tube; and

nate ones of said electrodes; and f. a second bus bar electrically isolated from said first

e. second bus bar means isolated from said first bus bus bar, external of said tube and electrically conbar

means electrically connecting the remaining necting all of said terminal means of said opposite

electrodes. 25 sign.

2. An axial flow electrolytic cell in accordance with 14. An axial flow electrolytic cell in which high curclaim

1 in which the conduit is a rigid straight tube. rent densities can be obtained with low metal concen-

3. An axial flow electrolytic cell in accordance with tration electrolytes, comprising: a closed channel of

claim 2 in which the tubular conduit has a circular dielectric material forming the cell body, sealing means

cross section. 30 for sealing the ends of said closed channel to provide a

4. An axial flow electrolytic cell in accordance with completely sealed cell body, a liquid inlet channel in

claim 1 in which the end closures are formed of electri- one of said sealing means and a liquid outlet channel in

cally nonconductivematerial. the other of said sealing means, perforate axially-

5. An axial flow electrolytic cell in accordance with spaced electrodes in said channel supported in an oriclaim

1 in which the electrodes are in substantial pe- 35 entation substantially perpendicular to the long axis of

ripheral engagement with the side walls ofsaid conduit. said chennel, said electrodes being dimensioned so that

6. An axial flow electrolytic cell in accordance with their peripheries extend substantially to the internal

claim 1 in which the electrodes are axialIy spaced at periphery of said closed channel, means for spacing

regular intervals. said electrodes, an electrical terminal for each elec-

7. An axial flow electrolytic cell in accordance with 40 trode connected to the electrode and extending

claim 1 in which the electrodes are nonconsumable. through the wall of said channel, the openings in the

8. An axial flow electrolytic cell in accordance with wall of said closed channel through which said termiclaim

7 in which the electrodes are expanded metal nals extend being sealed against leakage of fluids, first

plates. and second spaced-apart longitudinal bus bars lying

9. An axial flow electrolytic cell in accordance with 45 along the outside of said closed channel, the electrical

claim 8 in which the electrodes are of titanium metal. terminals for alternate electrodes being connected to

10. An axial flow electrolytic cell in accordance with said first bus bar and the electrical terminals of the

claim 5 in which the electrodes are each provided with remaining electrodes being connected to said second

terminal means projecting therefrom for extension 0 bus bar, said bus bars being connected, respectively, to

through the conduit wall. 5 positive and negative sources of electricity so that alter-

11. An axial flow electrolytic celI in accordance with nate electrodes are, respectively, anodes and cathodes,

claim 1 in which the first and second bus bar means are whereby the electrolytic cell which is formed by the

each disposed externally of the tubular conduit. recited structure is completely sealed against the. es-

12. An axial flow electrolytic cell in accordance with 55 cape of liquids and gases from the cell body except at

claim 8 in which the ratio of the effective surface area the inlet and outlet channels.

of the .electrodes to the cross sectional area is at least 15. The electrolytic cell of claim 14 in which said

0.8 to l. closed channel is substantially circular and said bus

13. An axial flow electrolytic cell in which an ion- bars are substantially 1800 apart.

containing and conducting medium flows axially 60 16. The electrolytic cell of claim 14 in which said

through perforated electrodes of alternating polarity at spacing means are spacing collars of dielectric material

flow rates productive of turbulent flow and comprising betweenthe electrodes peripherially abutting the interin

combination: nal surface of said closed channel and closely abutting

a. a rigid, electrically nonconductive tube of uniform adjacent electrodes.

circular cross-section; 65 * * * * *