An Improved Process for Obtaining Metals from Refractory Ores.
Year: 1896

page_text: Date of Application, 8th Feb., 1896
Complete Specification Left. 8th Dec.. 1896-Accented 6th Feb
1897
PROVISIONAL SPECIFICATION.
An Improved Process for Obtaining Metals from Refractory Ores.
We, JOHN STEWART WALLACE, of Cliftonville Avenue, Belfast, in the
County of Antrim, Ireland, Justice of the Peace, and JOHN CASTELL-EVANS, of
57 Westfield Road, Hornsey in the County of Middlesex, Chemist, do hereby
declare the nature of this invention to be as follows:-
This invention relates to the treatment of ores containing sulphides, selenides,
arsenides, and similar or like compounds, for the purpose of obtaining therefrom,
in a commercial form, the metals or other elements they contain; our invention is
applicable to the treatment of ores of silver, lead, zinc, cadmium and other ores,
and is particularly applicable to such ores as are commonly known as refractory
sulphide ores.
A chief feature in our invention, is the admixture with the ore or ores-either
in their raw condition or after one or more preparatory treatments-of some
substance or substances, all or part of which, when the charge is properly heated
will act as a reducing agent or agents and combine with the sulphur or such other
element that is present and cause liberation of the metal or metals from the ore;
this liberation, according to our invention, being effected under such condition as
will enable one or more of such metals to be removed from the other or others by
distillation or otherwise.
For example we may treat ores or mixtures of ores containing sulphides of zinc,
lead and silver by admixing therewith metallic iron, or any substance or mixture
of substances calculated to furnish metallic iron; so that when this mixture is
heated to a suitable temperature, the iron will unite with the sulphur, the metallic
zinc or most of it will be distilled off, and the other two metals, viz. the silver
and the lead, will remain in the furnace in the form of a metallic alloy. The
sulphur, which is now combined with iron, can be utilized in any desired manner,
for example, by being burned in a similar way to that in which pyrites are burned
for the manufacture of sulphuric acid, and the iron or compound thereof cau be
used again. The silver and lead can then be easily separated.
In some cases it will be found advantageous to first subject the ore to a roasting or
calcining treatment, or to subject it to the action of chlorine, or otherwise treat it
to remove all or part of any element the removal of which may be desired.
In some cases also we add to the refractory sulphide ores, other ores to ronder
the mass capable of being more easily fused.
The nature of the reducing agent, or agents or of the substance or substances
intended to furnish such agent or agents, may be varied to suit the requirements of
individual cases, and may be of such character that the sulphur, arsenic or other
element or elements in the ore under treatment, pass off during the process either
as the free element or elements, or as part of a volatile compound. For example
certain sulphides when heated with carbon or carbonaceous matter may give off
part or all of their sulphur as carbon disulphide.
One or more of the metals may be wholly or partially removed during the
process as oxide or other compound instead of being reduced to the metallic state.
Dated this 8th day of February 1896.
HASELTINE, LAKE & Co.,
45 Southampton Buildings, London, W.C., Agents for the Applicants.

page_text: An Improved Process for Obtaining Metals from Refractory Ores.
We, JOHN STEWART WALLACE, of Cliftonville Avenue, Belfast, in the
County of Antrim, Ireland, Justice of the Peace, and JOHN CASTELL-EVANS, of
57 Westfield Road, Hornsey, in the County of Middlesex, Chemist, 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 treatment of ores containing sulphides, selenides,
arsenides, and similar compounds, for the purpose of obtaining therefrom, in a
commercial form, the metals or other clements they contain. Our invention is
applicable to the treatment of ores containing lead, silver, zinc, cadmium and other
metals or elements such as arsenic and is particularly applicable to the treatment
of such ores as are commonly known as refractory or complex sulphide ores, such
as are found in the Broken Hill district in Australia and in Anglesea and Wicklow
and sometimes termed "bluestone."
Hitherto in the treatment of these ores it has been impossible on a commercial
scale to obtain all or practically all of the metals they contain owing principally
to the presence of zinc and to the peculiar manner in which it is, in practically all
such ores, combined with or united to the sulphur and other elements present.
Ores containing mixtures of galena (PbS) and blende (ZnS) are not at all uncommon
and in many cases they can, owing to their different densities, be fairly well
separated by a washing process or other known methods, but in the refractory ores
such as we propose to treat by our invention, it appears that, to a large extent at
least, the sulphides of lead and zinc are not merely intimately mixed but that the
three elements lead zinc and sulphur are actually in direct or indirect chemical
union with one another.
An essential feature of our invention consists in treating such ores or mixtures
thereof containing sulphides of zinc, lead and silver by admixing therewith a
reducing agent consisting of metallic iron, or any substance or mixture of substances
calculated to furnish metallic iron; so that when the whole mixture is heated to a
suitable temperature, and is caused to assume a sufficiently fluid condition the iron
will unite with the sulphur, the metallic zinc or most of it will be distilled off, and
the other two metals, viz. the silver and the lead, will remain in the furnace in
the form of a metallic alloy.
:
Where the weight of lead present in the ore under treatment is, say, between
four and five times as great as the weight of the zinc present, it will be found that
the ore fuses at what may be called a practicable temperature i.e. at a fair red
heat and that the mass will assume the requisite fluid condition to permit its
decomposition to be effected by the added iron or other ferruginous reducing agents.
If the ore is associated with a considerable amount of gangue then sufficient
quantities of fluxing material must be added to obtain this fluid condition of the
mass and the compound formed by such fluxing material and the gangue must
possess a comparatively low melting point.
It is an essential feature of our invention that the mass be brought to this fluid
condition in order that the reaction between the iron and sulphur can effectually
take place and for this purpose if the mass be not capable of assuming this fluid
condition of itself we add thereto either or both of the following ores reguli or
substances.
(a) Where the original ore or mixture of ores contains less lead in proportion to
the zinc than the ratio previously mentioned (4 or 5 of lead to 1 of zinc) then galena
(or other suitable ore or compound of lead or lead alone) is added until the desired

page_text: amount of lead is present in the charge. For example in au ore containing 14% of
lead and 8% of zinc as sulphides we should add per 100 tons of the ore, 30 tons
sulphide of lead or the equivalent amount of any ordinary galena at our disposal so
as to give us in the final ore mixture 40 tons of lead as sulphide of lead and 8 tons
of zinc. Associated with these quantities of lead and zinc we should have very
nearly 9-35 tons of sulphur and would consequently require 17.5 tons of iron for
their reduction.
As another instance we may take an ore containing
To this we add :
PbS 3.35% corresponding to 2.9 Pb+0.45 S giving as in all:-18.02 S, which
is not present as FeS and this amount would require 33.8 of Fe.
(b) Instead of galena, ferrous sulphide may be used in the proportion of about
88 parts of ferrous sulphide to 97 parts of sulphide of zinc over and above what
corresponds to one fifth of the lead present in the ore. Thus in the first example
2-8 tons of zinc corresponds to one fifth of the lead present in each 100 tons of ore
leaving 5.2 tons of zinc and this corresponds to about 7:04 tons of ferrous sulphide
as flux. The actual amount of FeS to be employed will depend on the quantity of
the lead sulphide present in the ore to be fluxed.
In some cases we propose to subject the ore or ores to preliminary treatments,
such as roasting, to get rid of such elements as arsenic before we attempt to fuse
the said ore or ores, this roasting being in some instances carried to such an extent
as to convert all or some considerable portion of the zinc into zinc oxide. This
will facilitate the fusion of the residual sulphides and other compounds.
As source of iron we can utilize the regulus from the earlier operations, which
we fuse with the necessary proportion of oxide thus:-
and the requisite quantity of oxide may be obtained by roasting some of the
regulus or from any other source.
The amount of reducing or desulphurizing iron to be added in order to obtain
the best results is found to be about 15 parts by weight to every 8 parts of sulphur
existing in the ore, other than as the proto-sulphide of iron.
The fused ore slag and iron are kept at a red heat for some time,-varying from
15 to 65 minutes depending on the composition of the ore-and it is found that the
reactions desired are expedited by stirring up the whole charge several times
during the operation. The reduced lead is then allowed to flow from the furnace,
pot, or retort, almost entirely but so as not to allow any regulus or slag to escape.
The flow is then stopped and the temperature is raised to incipient white heat so as to
cause the zinc to distil over from the upper end of the furnace, pot or retort. During
this period of increased temperature it is found advantageous from time to time to
run out from the lowest part of the furnace, pot or retort the lead that subsequently
collects, so as to minimise the loss of the lead that will be to some extent caused
by the increased temperature:
Practically the whole of the precious metals will be found in the lead. The zine
vapours may be condensed and collected as metallic zinc, or they may be allowed
to come in contact with atmospheric air at a suitable temperature and the resulting
oxide collected.

page_text: 3 PbS + 2 Fe,O, = 3 Pb + 4 Fe + 3 SO,
some of the reduced iron then reacts with a further quantity of galena as explained.
before, reducing a further quantity of lead and forming a regulus consisting of a
mixture of iron and iron sulphide.
Instead of the aforesaid reducing or desulphurizing iron or ferruginous substances,
or in addition thereto we-may use carbon or carbonaceous matter. This we do
either by mixing carbon in the form of charcoal or coke with the charge before
the separation of any of the lead, or better still with the residue remaining after
most or all of the lead has been separated. The carbon then reacts with the ZnS
as follows:-
2 ZnS C 2 Zn + CS,
the carbon disulphide being condensed collected and purified in the usual way.
The amount of carbon used to produce the best results is found to be about
3 parts by weight of carbon to every 16 parts of sulphur present in the ores as
zine sulphide. If carbou alone he used it should be in about the proportion of
3 parts of carbon to 16 parts of the total amount of sulphur present in the ores.
Having now particularly described and ascertained the nature of our said inven-
tion and in what manner the same is to be performed we wish it to be understood
that we are aware that small proportions of galena have been heretofore used in
the reduction of silver ores for the purpose of serving as a vehicle to carry down
the precious metals therein contained, and to such we make no claim, but what we
do claim is :-
1. A process for the treatment of complex sulphide ores containing lead and zinc
associated with precious or other metals, consisting in fusing such ores in the
presence of iron or ferruginous substances to convert the lead contained in the
charge to a metallic state, then removing a considerable portion of such lead and
subsequently raising the temperature of the remaining mass sufficiently to reduce
the zinc sulphide so that the zine may be volatilized, substantially as described.
2. A process for the treatment of complex sulphide ores containing lead and
zinc associated with precious or other metals, comprising the addition thereto. of a

page_text: sufficient quantity of a suitable compound of lead or compound of iron or both, to
render the mass sufficiently fluid to facilitate the reaction between the desul-
phurizing or reducing agent, and the sulphur, substantially as described and for the
purposes specified.
3. In the treatment of complex. sulphide ores as herein stated the complete or
partial substitution of carbon or carbonaceous matters for the reducing or desul-
phurizing iron or ferruginous substance substantially as described and for the
purpose specified.
4. Our improved process for the treatment of complex sulphide ores with the
substances herein mentioned and in the proportions substantially as hereinbefore-
stated and for the purposes described.
Dated this 8th day of December 1896.
JOHN STEWART WALLACE.
JOHN CASTELL-EVANS.
JOHN STEWART WALLACE.
JOHN CASTELL-EVANS.
Haseltine, Lake & Co.,
45 Southampton Buildings, London, W.C., Agents for the Applicants.