A Process for Recovery of Zinc from Blende Ores.
Year: 1896

page_text: Date of Application, 27th Feb., 1896
Complete Specification Left, 27th Nov., 1896-Accepted, 23rd Jan., 1897
[Communicated from abroad by STEPHEN HENRY EMMENS, of Amaden City,
California, and of Columbus, Ohio, in the United States of America.]
A Process for Recovery of Zinc from Blende Ores.
We, THE EXPLORING AND GOLD MINING ASSOCIATION LIMITED, of
Dashwood House, New Broad Street, in the County of London, do hereby declare
the nature of this invention to be as follows:-
The object of this invention is to recover zinc economically from blende ores,
such as for example, the zinc-lead sulphide ores of Broken Hill in Australia.
For this purpose, first the ore is crushed to powder, then the crushed ore is
roasted in a reverberatory or other furnace, the temperature and admission of air
being so regulated as to convert the zinc sulphide into zinc sulphate, without
decomposing any considerable proportion of such sulphate.
A series of vats are arranged ench of which has a sheet-lead or other insoluble
anode at the bottom and a horizontal cathode-plate of zinc or other suitable metal
suspended in the upper part. These electrodes are connected to a source of
electricity by switches so arranged that an electric current may, whenever desired,
be caused to pass from the anodes to the cathodes through the contents of the vats.
Each rat has an inlet pipe extending to the bottom and an outlet pipe or spout
leading from the top; the vats and pipes being so arranged and connected, that a
flow of liquid can be caused to traverse the entire series alternately descending
and ascending.
The vats are charged with the crushed roasted ore, and water is caused to flow
into vat No. 1 which, at the outset, is cut off from the electric circuit. The water
dissolves the zinc sulphate in vat No. 1, and the solution passes on to the bottom
of vat No. 2, which is connected to form an electrolytic cell. The solution rises
through the ore in vat No. 2 taking up a further amount of zinc sulphate, and
finally reaches the cathode, on which metallic zinc is deposited, while a corre-
sponding quantity of sulphuric acid is set free in the liquid. The solution, thus
acidified, passes on to vat No. 3, which is cut off from the electric circuit, and
becomes neutralised by dissolving some of the zinc oxide and basic zinc sulphate
contained in the roasted ore; it then flows into vat No. 4, which is connected to
the electric circuit, where it deposits a further quantity of zinc, and again becomes
acidified. The flow of the solution, thus alternately neutralised and acidified,
continues through the whole series of vats; and, on leaving the last, it is sent
again into vat No. 1 to resume its circulation.
At suitable intervals of time, such as, for example, every half-hour, the
vats Nos. 2, 4, 6, &c. are cut out of the electric circuit, and the vats Nos. 1, 3, 5
&c. are put in circuit so that they become the acidifying vats.
The flow of the solution, and the change of the electric current from vat to vat
are continued until the desired amount of metallic zinc and zinc sulphate is
separated from the ore which may then be smelted. The residuary solution may
be treated by known means for precipitation of the zinc or may be crystallised as
sulphate or otherwise disposed of.
Finally side doors of the vats are opened, and, by means of a jet of water, the

page_text: lenched ore is washed out into conduits leading to a settling tank, from which,
after settlement, the wash-water may be delivered to a storage tank, to be used
as the leach-water for a fresh charge of ore. The leached and washed ore is
then removed from the settling tank and dried; after which it is ready for the
market.
Dated this 27th day of February 1896.
We, THE EXPLORING AND GOLD MINING ASSOCIATION LIMITED, of
Dashwood House, New Brond Street, in the County of London, do hereby declare
the nature of this invention and in what manner the same is to be performed to be
particularly described and ascertained in and by the following statement :-
This invention relates to the removal of zine from zinc bearing ores, and is
particularly applicable to the treatment of such ores as contain zine and lead
sulphides, ns, for example tho zinc lend sulphide ores of Broken Hill in Australia.
The invention consists in an improved process hereinafter set forth, and in a
novel segregable part of said process; the objects of the invention being to
economically remove the zinc contents from such ores and to this end to subject
the crushed and roasted ore to a system of progressive leaching in which the
solution remains at all times in contact with the ore and yet becomes alternately
acid and neutral or less acid as it travels continuously through the ore.
The accompanying drawing is a diagrammatic section of the lenching apparatus
and its appurtenances.
We carry our invention into effect in the following manuer :-
First we crush the ore, by known means, to a suitable degree of fineness, which
in most cases may be from 20 to 30 mesh.
Secondly we subject the crushed ore to a roast in a reverberatory furnace, which
may be of known construction; the temperature and admission of air being so
regulated as to convert the zinc-sulphide or other zinc mineral present into zinc-
sulphate, without decomposing any considerable proportion of such sulphate.
Thirdly we provide a series of vats, represented at 1, 2, 3 and 4 in the drawing;
each vat having a sheet-lead or other insoluble anode A at the bottom and a
horizontal cathode-plate C of zine or other suitable metal suspended in its upper
portion. These electrodes are connected in an electric circuit, D, E so arranged
that an electric current may, whenever desired he caused to pass from the anodes
to the cathodes through the contents of the vats. We also provide each vat with
an inlet pipe extending to the bottom of the vessel, and with an exit pipe or
trough Gleading from the top of the vat; the respective pipes and troughs being
so arranged and connected that a flow of liquid may traverse the entire series of
vats in an alternately descending and ascending manner. A storage tank H
discharges through a pipe I into the inlet pipe F of the first vat, and the trough G
of the last vat of the series discharges into a receiving tank J.
Fourthly, we partially fill the vats with the crushed and roasted ore, represented
at Z, and cause a flow of water to pass from the storage tank 1 through the pipe I
and the first inlet pipe F into vat No. 1, which at the outset is not made part of
the electric circuit. The water dissolves the zinc-sulphate in vat No. 1 and the
solution passes forward by its exit trough G into vat No. 2 which is at that time
made part of the electric circuit. As the liquor rises it passes through the ore,
taking up more zinc-sulphate, and on reaching the cathode plate C of said

page_text: vat No. 2 closes the electric circuit, whereupon a flow of electricity takes place
and an electrolytic action is set up, depositing metallic zinc on the cathode and
setting free a corresponding quantity of sulphuric acid. The solution, thus
acidified, flows from vat No. 2 into vat No. 3, which is not then part of the electric
circuit, and as it rises through the ore becomes neutralized by dissolving some of
the zinc-oxide and basic zinc-sulphate in the ore. It next flows into vat No. 4
which is then part of the electric circuit, where it deposits a further quantity of
zinc and again becomes acidified. The flow of the solution thus alternately
neutralized and acidified continues through the whole series of vats, which may be
more or less numerous. On leaving the last vat it enters the receiving tank J,
from which it is elevated by a pump K or other suitable means to a level from
which it flows back into the storage-tank H; being conducted by a pipe or pipes L;
and is thus enabled to resume its circulatory travel.
Fifthly, at suitable intervals of time, as for example every half hour, we cut
vats 2, 4 &c. out of the electric circuit, and cause the electric current to pass
through vats 1, 3 &c. which thereupon become acidifying vessels. This change is
preferably effected by suspending each neighbouring pair of the cathodes C from
the ends of a metallic beam M, pivotted in its middle and forming part of the
circuit-leg E connecting the cathode-plates with the negative pole of the dynamo
which furnishes the electric current. By turning the beam M on its pivot to a
sufficient extent, oue cathode is depressed into the solution in the vat to which it
belongs, and the cathode at the other end of the beam is raised out of the solution
in its vat; thereby closing or opening the electric circuit in either vat as may be
desired, and removing the deposited zinc from risk of re-solution in the vat which
is cut out of the circuit.
Sixthly, we continue the flow of the solution and the change of the electric
current from vat to vat until the metallic zinc deposited and the zinc-sulphate in
the solution amount together to a quantity showing that the zinc contents of the
ore have been removed sufficiently to render the residual ore fit for smelting. The
solution is then run off through a pipe or pipes N into a sulphate-tank O, where
the zinc may be precipitated by known means as hydrate, or crystallized as
sulphate, or disposed of in any preferred manner.
Seventhly, we open side-doors P with which the vats are provided, and by means
of a jet of water, we wash the leached ore into sluices Q leading to a settling-
tank R, from which, after subsidence, the wash-water is elevated by a pump S, or
its equivalent, through a pipe T, into the storage-tauk H, to be used as the
leaching solution for a fresh charge of ore. The leached and washed ore is then
removed from the settling tank R and dried, after which it is ready for smelting
or for the market.
The leaching-vats 1, 2, 3, &c., may, as already indicated, be of any required or
preferred number; a draining-pipe may extend from the bottom of each vat to the
sulphate-tank O as indicated by dotted lines at N'; various known substitutes may
take the place of the beams M and rising and falling cathodes C for alternately
opening and closing the electric circuit through successive vats; and other like
modifications will suggest themselves to those skilled in the art.
Having now particularly described and ascertained the nature of our said inven-
tion and in what manner the same is to be performed we declare that what we
claim is :-
1. A process of treating zinciferous ores which consists in pulverizing and
roasting such ores and then leaching them with water in a series of vessels, the
solution being rendered alternately acid and neutral, or more acid and less acid, in
contact with the ores, as it flows through the series; such acidification being caused
by the action of an electrolytic current periodically traversing each vessel to
deposit a portion of the zinc, and such complete or partial neutralising being caused
by the dissolving of basic matter in the leaching vessels through which for the
time being no electric current is passing, substantially as described.

page_text: 2. In the treatment of zinciferous ores by leaching and electrolysis in a series of
vessels, intermittently subjecting the contents of each vessel to electrolytic action
followed by a neutralizing period, whereby the leaching solution is maintained in
contact with the ore throughout the series and yet becomes alternately acid and
neutral or more acid and less acid as it travels through the ore.
Dated this 27th day of November 1896.
ABEL & IMRAY,
Agents for the Applicants.