CONTAINER FOR CORROSIVE MATERIAL

CONTENANT POUR MATIERE CORROSIVE

English Abstract

An apparatus for recovering a metal from a toxic solution is disclosed. The
apparatus includes a plurality of vessels (10, 10a, 10b) for containing the
solution, each vessel (10) including an upper portion above the solution,
electrode (50) extending into the solution in each vessel (10) for passing an
electric current therethrough wherein toxic mist occurs in the upper portions
of the vessels (10, 10a, 10b) above the surfaces of the solution, at least one
pair of said vessels (10-10a and 10-10b) being disposed in a side-by-side
relation to define spaces (44, 46) therebetween, and creating an airflow in
the upper portion of the adjacent vessels from the space (44) between one pair
of vessels (10-10a) to the space (46) between another pair of vessels (10-10b)
for evacuating the toxic mist from above the solution in said vessels (10,
10a, 10b).

French Abstract

Appareil servant à récupérer un métal contenu dans une solution toxique. L'appareil comporte plusieurs cuves (10, 10a, 10b) destinées à contenir la solution, chaque cuve (10) comprenant une partie supérieure située au-dessus de la solution, une électrode (50) traversant la solution dans chaque cuve (10) pour y faire passer un courant électrique ceci produisant des embruns toxiques dans les parties supérieures des cuves (10, 10a, 10b) au-dessus des surfaces de la solution, au moins deux desdites cuves (10-10a et 10-10b) étant placées l'une à côté de l'autre pour définir des espaces (44, 46) entre ces dernières et pour créer un écoulement d'air dans la partie supérieure des cuves adjacentes depuis l'espace (44) existant entre les deux cuves (10-10a) jusqu'à l'espace (46) existant entre les deux autres cuves (10-10b) afin d'évacuer les embruns toxiques présents au-dessus de la solution située dans lesdites cuves (10, 10a, 10b).

Claims

1. An apparatus for recovering a metal from a
toxic solution and including a plurality of vessels for
containing the solution, each vessel including an upper
portion above the solution, electrode means extending
into the solution in each vessel for passing an
electric current therethrough wherein toxic mist occurs
in the upper portions of the vessels above the surfaces
of the solution, at least one pair of adjacent vessels
being disposed in a side-by-side relation, the outer
surfaces of side walls of the adjacent vessels defining
a space therebetween, means for closing the margins of
the space to define an enclosure, and means for
creating an airflow in the upper portions of the
adjacent vessels and over the surfaces of the solution
in said adjacent vessels and outwardly from said
vessels and into the enclosure defined by the outer
surface of the vessel side walls for evacuating the
toxic mist from above the solution in said vessels.
2. The apparatus set forth in claim 1 wherein
the side walls of the adjacent vessels have upper and
lower ends for defining upper and lower portions of
said enclosure, suction producing means coupled to the
lower end of the enclosure for drawing the toxic mist
downwardly between the side walls of the vessels.
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3. The apparatus set forth in claim 2 wherein
the means for enclosing said space includes a first
member extending across the gap between the upper ends
of the adjacent side walls and a second member
extending between lower ends of said side walls.
4. The apparatus set forth in claim 3 wherein
said vessels have and electrode support extending along
the upper end of the side walls, and openings formed
beneath the electrode support for communicating the
vessels with the enclosure.
5. An apparatus for recovering a metal from a
toxic solution and including a plurality of vessels for
containing the solution, each vessel including an upper
portion above the solution, electrode means extending
into the solution in each vessel for passing an
electric current therebetween wherein a toxic mist
occurs in the upper portions of the vessels and above
the surfaces of the solution, said vessels being
disposed in a side-by-side relation and each including
first and second side walls, each sidewall having an
outer surface disposed in an opposed relation to the
outer surface of an adjacent vessel to define a first
space between a first vessel and a second vessel
adjacent one side of the first vessel and a second
space between the first vessel and a third vessel
adjacent the other side of the first vessel, means for
-8-

enclosing said first and second spaces to define first
and second enclosures, means for communicating the
upper portions of the first and second vessels with the
first enclosure and the upper portions of the first and
third vessels with said second enclosure, means for
creating a positive pressure in the first enclosure and
means for creating a suction in the second enclosure
whereby currents are created in the upper portions of
the vessels causing the toxic mist to flow out of said
first and third vessels and into said second enclosure.
6. The apparatus set forth in claim 5 wherein
said suction producing means is coupled to the lower
end of the second enclosure for drawing the toxic mist
downwardly between the outer side surfaces of the first
and third vessels.
7. The apparatus set forth in claim 6 wherein
the means for creating pressure in the first enclosure
is coupled to the lower end thereof for introducing air
under pressure into the lower end of the first
enclosure, said air flowing over the upper portion of
the vessels for entraining the toxic mist and carrying
said mist into the second enclosure.
8. The apparatus set forth in any of claims 6 or
wherein each of said vessels have an upper end, the
means for enclosing said spaces includes a first member
-9-

extending across the gap between the upper ends of the
side walls of the vessels and a second member extending
between adjacent the lower ends of the side walls of
said vessels.
9. The apparatus set forth in any of claims 6-8
wherein the vessels have means extending along the
upper end of the side walls for supporting said
electrodes, and openings formed beneath the electrode
supporting means for communicating the vessels with the
first and second enclosures.
10. A method of electrowinning copper comprising
the steps of disposing a solution containing copper
ions and sulfuric acid in a vessel, suspending a
plurality of electrodes in the solution, passing an
electric current between said electrodes, wherein
copper is harvested on one of the electrodes and
wherein a mist of sulfuric acid is generated and
collects above the surface of the solution, passing an
air current from one side of the vessel to the other
and across the surface of the solution for entraining
the sulfuric acid mist, collecting the entrained
sulfuric acid mist and air in an enclosure formed on
two sides by the outer surfaces of two adjacent vessels
and drawing the air and entrained acid mist downwardly
in an enclosure defined on two sides by the outer
-10-

surfaces of the adjacent vessels and collecting said
acid mist adjacent the lower end of the enclosure.
11. An apparatus for recovering a metal from a
toxic solution and including a pair of vessels for
containing the solution, each of said vessels including
an upper portion above the solution, electrode means
extending into the solution for passing an electric
current therebetween wherein toxic mist occurs in the
upper portions of the vessels above the surface of the
solution, each of said vessels including side walls
having an outer surface, said vessels being disposed in
a side by side relation with one side wall of a first
vessel being located adjacent one side wall of the
second vessel to define a space, means for closing said
space to define an enclosure, means for creating an air
flow in the upper portion of the vessel and over the
surface of the solution and outwardly from said vessel
and into said enclosure for evacuating the toxic mist
from above the solution in said vessel and means for
creating a suction coupled to the lower end of the
space for drawing the toxic mist downwardly along the
side of the vessel.
12. The apparatus set forth in claim 11 and
including a third vessel provided with a side wall
having an outer surface the third vessel being disposed
adjacent the first vessel with the outer surface of the
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third vessel adjacent to the outer side wall surface of
the first vessel to define a second space which
communicates with the upper end of the vessel, means
enclosing the second space to define a second
enclosure, means coupled to said second enclosure for
creating pressure therein for producing an air flow
across the upper end of said first vessel and into said
first enclosure for entraining the toxic mist and carry
said mist into the first enclosure.
-12-

Description

CA 02240l2~ Igss-06-os
W097/22736 PCT/US96/19707
CONTATN~R FOR CORROSIVE MATERIAL
BACKGROUND OF THE lN V~iN~l lON
This invention relates to a pollution control
system and more particularly to a system for removing
noxious mists from electrowinning cells.
Electrowinning of copper involves a process of
recovering copper from a sulfuric acid solution by the
passage of electric current between an anode which may
be formed of a material such as lead and a copper
cathode upon which the copper is harvested.
The process is normally carried out in an
electrolytic cell in which a plurality of alternate
anodes and cathodes are suspended from cell top
furniture which extends along the sides of the vessel.
This process results in the formation of oxygen bubbles
which rise to the surface of the electrolyte and bu~st
thereby forming a mist of an acid such as sulfuric
acid. This acid mist is hazardous to wor~ers and must
be removed, or suppressed.
Attempts to solve the acid mist problem in copper
electrowinning facilities include the use of large
ventilation fans which can effectively reduce the mist,
but involve high capital costs. Another solution is to
cover the bath with foam strips located between the
electrodes, or with layers of plastic beads or balls.
These solutions are also not satisfactory because the
foam strips require the use of reagents which
cont~m;n~nt the solvent extraction process. Plastic

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wos7/22736 PCT~S96/19707
balls have not been wholly satis~actory because they
may affect cathode quality and beads are difficult to
contain within the cells.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a new
and improved method and apparatus for controlling acid
mists in copper electrowinning cells.
This and other objects and advantages of the
invention will become more detailed from the detailed
description thereof taken with the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIGURE l is a side elevational view in section
showing a cell according to the present invention;
FIGURE 2 is a view ta~en along lines 2-2 of Figure
l;
FIGURE 3 is a partial plan view of the cell
illustrated in Figure l; and
FIGURE 4 is an enlarged fragmentary cross section
showing a portion of the cell illustrated in Figure l.
DETATT.~ DESCRIPTION OF THE PREFERRED EMBODIMENT
Cell l0 according to the pre~erred embodiment of

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the invention is shown in the drawings to include a
bottom 12, side walls 13 and 14, and end walls 15 and
16. The cell may be formed of any suitable material
such as the polymer concrete disclosed in U.S. Patent
No. 4,885,072 which is incorporated by reference
~ he.rein. The inner and outer surfaces of the cell may
be coated with a corrosion-resistant lining as
disclosed in U.S. Patent No. 5,079,050, which is
incorporated by reference herein. A matrix of
reinforcing bars (not shown), of a non-conductive
material, such as FRP fiberglass, is disposed in the
bottom 12 and extends at least up the side and end
wal.ls 13, 14, 15 and 16 as reinforcement against
damage.
An overflow box 18 is provided in a generally
semi-circular ~ormation 19 integrally molded on the
outer surface of the end wall 16 and adjacent the side
wall 14. The overflow box 18 includes a recess 20
formed in the inner portion of formation 19 and opening
into the interior of cell 10. An overflow pipe 21 is
cast in the formation 19 and extends vertically from
the recess 20 downwardly for connection to a sump for
collection of the overflow electrolyte.
A longitudinal groove 24 formed on its inner
surface 25 of side wall 14 and adjacent the upper end
thereof. An adjustable weir 26 is fixed to the inner
surface 25 of wall 14 and adjacent the ~ower portion of
groove 24 in any suitable manner such as by means of

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WO 97/22736 PCT/US96/19707
screws 30 which extend through slots 31 formed in the
weir 26 and which are receivable within threaded
inserts 32 disposed in the wall 14 below groove 24.
The weir is formed of a suitable non-corrosive material
and its upper edge includes a plurality of notches 34.
Fresh electrolyte is introduced into the cell by means
of manifolds 36 ~Figure 2) which extend longitudinally
along the bottom 12 and adjacent the side walls 13 and
14 and each has apertures 36 through which electrolyte
flows into the cell 10. Overflow electrolyte flows
through the notches 34 in weir 26, one end of which
communicates with the overflow box 18. From the
overflow box 18, the electrolyte flows downwardly
through the overflow pipe 21.
The upper end of each of the side walls 13 and 14
has a plurality of spaced notches 40 and 42,
respectively, which are distributed uniformly from end
to end. The cells 10 in a copper electrowinning plant
are arranged in a side-by-side and end-to-end relation
as illustrated in Figure 2 where cell 10 is flanked by
cells 10a and 10b in an alternating orientation such
that the wall 13a of cell 10a is adjacent wall 13 of
cell 10 and wall 14b of cell 10b is adjacent the wall
14 o~ cell 10. This defines a first space 44 between
cells 10 and 10a and a second space 46 between cells 10
and lOb. The upper ends o~ the spaces 44 and 46 are
closed by capping boards 48 which are supported on the
upper edges of the side walls 13 and 13a and the

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W097/22736 PCT~S96/ls707
adjacent side walls 14 and 14b. As seen in Figure 2,
the cell top furniture provides support for the
electrodes 50 and extend from one end of the cells 10,
lOa and 10~ to the other. The cell top furniture rests
on the upper edges of the side walls 13, 13a, 14 and
14b so that a first series of gaps 52 are defined by
the notches 40 and 40a in side walls 13 and 13a and a
second series of gaps 54 and 54a are defined by the
notches 42 and 42b in side walls 14 and 14b. This
co~mtlnicates the interior o~ cells 10, lOa and lOb with
the spaces 44 and 46.
The lower ends of the spaces 44 and 46 are closed
by longitudinal flanges 52 and 54 extending
respectively from the lower ends of the side walls 14
of cell 10 and flange 52a extending from the lower end
of side wall 13a of cell lOa and flange 54b which
extends from the lower end of side wall 14b of cell
lOb. In a similar manner, the ends of space 44 are
cla,sed by flanges 56 and 58 extending from each of the
end. walls 15 and 16 of cell 10 and mating flanges 56a
extending from the end walls of cell lOa and 58b
ext.ending from the end walls of lOb.
An air delivery system 60 is connected by a
conduit 62 to an opening 64 formed in the flanges 52
and: 52a for providing air under pressure to the space
44. An exhaust system 66 is connected by a conduit 68
to an opening 70 formed in the flanges 54 and 54b so
tha.t the exhaust system 66 com~l~n;cates with the space

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46.
In operation, air under pressure is delivered from
the air system to the gap 44 and flows upwardly to the
upper end thereof and out between the openings 52 and
5~a. As seen in Figure 3, the notches 40 are wider at
their inner ends than the outer ends so that as the air
flows through the gaps 52, it fans outwardly over the
upper surface of the electrolyte. This forms an air
curtain which entrains the acid mists and carries it
across the upper end of the cell where it is drawn into
the space 46, downwardly between the walls 14 and 14b
and to the exhaust system 66. As a result, the acid
mists can be captured and removed without the need for
coverings such as foam pads, plastic balls or beads on
the upper surface of the electrolyte. It will be
appreciated that because both the inner and outer
surfaces of the side walls 13 and 14 are exposed to the
corrosive material, it is preferable that both the
inner and outer surfaces of the cell 10 be coated with
a corrosion resistant material.

Representative Drawing