Improvements in the Treatment of Sulphide Ores.
Year: 1899

page_text: PROVISIONAL SPECIFICATION.
Improvements in the Treatment of Sulphide Ores.
We, JAMES SWINBURNE, of 82, Victoria Street, London, S.W., Engineer, and
EDGAR ARTHUR ASHCROFT of same address, Metallurgist, do hereby declare the
nature of this invention to be as follows:-
Our invention has reference to the treatment of sulphide ores or products with
chlorine, for the purpose of separating the valuable from the worthless con-
stituents, and the resulting metallic chlorides may be electrolysed so as to con-
stitute a cyclic process.
The process is applicable to various sulphides but we will describe it specially
in connection with mixed lead-zinc sulphide ores.
The ore is ground finely, and it is made into a cream with fused chloride of
zinc, or preferably a mixture of chloride of zinc with sodium or potassium chloride.
The cream is put into a converter of special design in which it is treated with
chlorine, the gas being forced in at the bottom (in a manner similar to the
converter used for treatment of copper and other ores or mattes by air blast).
At a suitable temperature the chlorine is. rapidly absorbed by the metals and
sulphur is given off in its place. The re-action is most vigorous at a high tem-
perature and being exothermic the temperature may be regulated by increasing
or decreasing the blast of chlorine. If desired, the operation may be pushed so far
as to more or less completely volatilize the zinc and the other metallic chlorides
leaving the gangue behind as a residue, associated only with small quantities of
chlorides. To start the operation it is most convenient to fuse the chlorides etc..
in a separate vessel or furnace. The treatment is carried on till all or nearly all the
sulphides are converted into chlorides, and the iron which is practically always
present, may also be all converted into the ferric state and in this state it is
readily precipitated as Fe, O, by the addition of ZnO (roasted zinc ore) to the pot.
During nearly the whole of the process the chlorine is completely absorbed,
sulphur, (and at certain temperatures sulphur chloride) being liberated. These
are collected and condensed. Towards the end a little excess of chlorine may be
necessary to make sure of oxidizing all the iron to the ferric state. Any chlorine
that passes over at this stage may be returned to the chlorine store after con-
densation of the sulphur. The sulphur is comparatively pure and may be sold
for any common purpose. If it is associated with important quantities of metallic
chlorides, as will be the case when conducting the process at high temperatures
the chlorides may be dissolved in water, leaving the insoluble sulphur behind.
At the end of the treatment the converter contains varying quantities of fused
chlorides of zinc lead, silver and iron and all the gangue. If zinc oxide has been
added to the charge the iron is all present as ferric oxide and the gangue and
the iron may now be allowed to settle, preferably in a separate vessel or furnace,
and the clear chlorides poured off. The fused chlorides may then be treated with
metallic lead or zinc which removes all the metals which will part with their

page_text: chlorine to lead, such as silver and. gold and antimony. The lead which is now
rich in silver, and in some cases gold, may be then run off to be treated for
the precious metals. The fused chlorides may then be treated with zinc, which
takes out the lead by substitution. The fused mass then contains zinc, and
potassium chlorides and some trace of chlorides of manganese and other metals
(or the mixed chlorides may be electrolysed without previous treatment with lead
and zinc in which case the silver-lead and zinc will separate progressively and
may be drawn off from the electrolysis bath at suitable intervals in a more or
less divided state. Instead of precipitating the iron when the charge is in the
converter, the fused chlorides may be dissolved in water and the solution treated
for the removal of iron, by means of zinc oxide or otherwise, the iron being
brought to the ferric state by chlorine. The resulting solution of zinc and sodium
or potassium chloride is then evaporated down and fused, and electrolysed to
extract the zinc with or without the previous precipitation of silver by lead and
lead by zinc, as above described. The double chlorides of sodium or potassium
and zinc are preferred because they decompose little on drying and are very
fusible. They also fume but little on melting and exposure to the air.
As to the mixture of gangue and fused chlorides from which the clear chlorides
have been described as having been poured off or partially distilled off, the cream
may be treated with lead and then with zinc in the same way as the clear
chlorides. On dissolving in water there will be found some small globules of
lead or zinc which have been mixed with the gangue; but they are easily separated
under water. Or the chlorides may be distilled from the gangue by heating.
The more or less pure product of ZnKCl, resulting from the above operations
is conveniently treated by electrolysis in the fused state, the resulting zine may be
collected as molten metal and the chlorine drawn off to be used for the converters.
The electrolysis is best carried on in a vat which is heated and kept hot by the
electric current, which causes the decomposition of the chloride: the volts
necessary at the terminals of the bath will depend to a large extent on the means
employed to conserve the heat in the bath. With large vats from 2.5 to 5 volts
will be required.
The chlorine from the electrolysis vat may be pumped direct to the converter,
but preferably it is cooled and compressed and stored in the liquid state. The
storage may be assisted by cooling to a low temperature such as-30° C.
This converter method of treating sulphides with chlorine is applicable to other
sulphides, such as iron, copper, nickel, cobalt, antimony etc. In the case of iron
pyrites ores particularly, these ores can be treated in conjunction with oxidised
zinc ores. The sulphur is first expelled and the iron chloride raised to the ferric
state by chlorine. The iron is then precipitated as Fe, O, by the addition of
oxidised zinc ore. The resulting zinc chloride is then removed and electrolysed
as before. The residue of ferric oxide may also constitute a valuable product as
iron ore or paint.
An operation analogous to the above may be carried on by placing the cream
in a revolving furnace of form similar to a Bruckner roasting cylinder, contracted
at the ends. The gas is admitted through a pipe leading into the centre door
and the sulphur distils off through a similar pipe in the other end door. The
doors can be removed and a movable fire box and flue substituted to heat the
charge initially.
1
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page_text: improvements in the Treatment of Sulphidə Ores.
We, JAMES SWINBURNE, Engineer, and EDGAR ARTHUR ASHCROFT, Mining
Engineer, both of Grosvenor Mansions, 82, Victoria Street, Westminster, 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:-
-
Our invention has reference to the treatment of sulphide ores or products with
chlorine, for the purpose of separating the valuable from the worthless con-
stituents, and the resulting metallic chlorides may be electrolysed so as to con-
stitute a cyclic process.
The process is applicable to the numerous sulphide ores in which the various
metals are contained single or together, but we will describe it particularly in
connection with mixed lead-zinc silver sulphide ores, such as the well known
Broken Hill ores.
In carrying this invention into effect, the ore is crushed and it is made into a
cream with fused chloride of zinc, or a mixture of chloride of zinc with sodium or
potassium chloride. The cream is put into a converter or suitable vessel in which
it is treated with chlorine, the gas being forced in at the bottom. At a suitable
temperature for instance a low red heat, the chlorine is rapidly absorbed by the
metals and sulphur is given off in its place. The reaction is most vigorous at high
temperatures well above the fusing point of zinc chloride, and being exothermic,
the temperature may be maintained and regulated by increasing or decreasing the
blast of chlorine. If desired the operation may be pushed so far as to more or less
completely volatilize the zinc and the other metallic chlorides, leaving the gangue
behind as a residue, associated only with small quantities of chlorides. To start
furnace, the converter being heated by internal action. The treatment is carried
the operation it is convenient to fuse the chlorides etc. in a separate vessel or
on till all or nearly all the sulphides are converted into chlorides. Fresh supplies
of sulphides are added to the converter and the operation is carried on until the
residual gangue has accumulated so as to make the mixture with the remaining
chloride too thick for working. The iron which is practically always present, may
also be all converted into the ferric state by chlorine, and in this state it is
really precipitated as l'e, 3 by the addition of ZnO (roasted zinc ore) to the pot.
Manganese is also precipitated as oxide by passing in chlorine in the presence of
zinc oxide. Or manganese and iron are both precipitated by blowing in air in
the presence of zinc oxide. This zine oxide may be made from the sulphide if
desired by oxidising a portion of the sulphur of the ore by means of the air blast
instead of carrying the decomposition of the sulphide to completion by means of
the chlorine blast. During nearly the whole of the process the chlorine is com-
pletely absorbed, sulphur being liberated. This is collected and condensed.
Towards the end a little excess of chlorine may be necessary to make sure of
oxidising all the iron to the ferric state. Any chlorine that passes over at this
stage may be returned to the chlorine store after condensation of the sulphur,
taking care to avoid the formation of chloride of sulphur by keeping the chlorine
from coming into contact with the sulphur. The sulphur is comparatively pure
and may be sold for any common purpose. If it is associated with important
quantities of metallic chlorides, as will be the case when conducting the process
at high temperatures, the chlorides may be dissolved in water, leaving
insoluble sulphur behind, or they may be separated by fractional distillation. At
the end of the treatment the converter contains varying quantities of fused
the

page_text: chlorides of zinc lead, silver, iron and manganese and all the gangue. If zinc
oxide has been added to the charge the iron and manganese are present as oxides,
the gangue and the iron and manganese oxides may be allowed to settle, pre-
ferably in a separate vessel or furnace, and the other chlorides poured off. The
fused chlorides may then be treated with metallic lead, which removes all the
metals which will part with their chlorine to lead, such as silver and gold and
antimony. The excess lead, which is now rich in silver, and in some cases gold,
may be then run off to be treated for the precious metals. The fused chlorides
may then be treated with zinc, which takes out the lead by substitution. The fused
mass then contains zinc chloride or zinc and sodium or potassium chlorides and
some traces of chlorides of iron and manganese and other metals. Or the mixed
chlorides may be fractionally electrolysed without precious treatment with lead
or zinc, in which case the silver-lead and the zinc will separate progressively
and may be drawn off from the electrolysis bath at suitable intervals. Instead
of precipitating the iron and manganese when the charge is fused, the chlorides
after the extraction of lead and precious metals, may be dissolved in water and
the solution treated for the removal of iron and manganese by means of zinc
oxide or otherwise, the iron being brought to the ferric state by chlorine. The
resulting solution of zinc chloride or zinc and sodium or potassium chlorides
is then evaporated down and fused and electrolysed to extract the zinc.
double chlorides of sodium or potassium and zinc are preferred for electrolysis
because they decompose little on drying and are more fusible and conduct better.
They also fume but little on melting and exposure to the air. But simple
chloride of zinc is preferred in the converter. As to the mixture of gangue and
fused chlorides from which the clear chlorides have been poured off or partially
distilled off, the cream may be treated with lead and then with zinc in the same
way as the clear chlorides. The zinc chloride or the zinc and potassium or
sodium chlorides may be dissolved out in water, when some small globules of lead
or zinc which have been mixed with the gangue, and which are easily separated
under water may be observed. Or the chlorides may be distilled from the gangue
by heating. The more or less pure product of zinc chloride resulting from the
above operations is conveniently treated by electrolysis in the fused state, the
resulting zinc may be collected as molten metal and the chlorine drawn off to
be used for the converters. The electrolysis is best carried on in a vat which is
heated and kept hot by the electric current which causes the decomposition of the
chloride; the pressure necessary at the terminals of the bath will depend to a
large extent on the means employed to conserve the heat in the bath.
The
The chlorine from the electrolysis vat may be pumped direct to the converter,
but preferably it is cooled and compressed, and stored in the liquid state. The
storage may be assisted by cooling to a low temperature. This converter method
of treating sulphides with chlorine is applicable to the treatment of other sul-
phides, such as iron, copper, nickel, cobalt, antimony etc.
Having now particularly described and ascertained the nature of our said
invention and in what manner the same is to be performed, we declare that
what we claim is:
1. Treating sulphide ores, suspended in or mixed with a fused chloride or
chlorides with chlorine, substantially as described.
2. Treating metallic sulphides with a fused chloride or chlorides and passing
chlorine through the mixture, substantially as described.
3. Obtaining sulphur from sulphide ores by passing chlorine through a mixture
of the ore and a fused salt, substantially as described.
4. Treating ore mixed with chloride in a converter heated essentially by the
chemical action of the chlorine.
5. The cyclic process of treating ores suspended in fused salt with chlorine
and electrolytically decomposing the resulting chlorides into metal and chlorine.

page_text: 6. As a step in the herein described process, separating from the fused chlorine
treated charge, iron and manganese, by precipitation as oxide substantially as
described.
Dated this oru day of March 1990.
EDGAR A. ASHCROFT,
Boult, Wade & Kilburn,
Agents for the Applicants.