An Improved Process for the Reduction of Argentiferous and Auriferous Copper Ores, Mattes, or Compounds without Loss of the Copper, Silver, or Gold.
Year: 1896

page_text: Date of Application, 6th July, 1896-Accepted, 15th Aug., 1896
COMPLETE SPECIFICATION.
An Improved Process for the Reduction of Argentiferous and
Auriferous Copper Ores, Mattes, or Compounds without Loss
of the Copper, Silver, or Gold.
I, CHRISTOPHER JAMES, of Ida Villa, Swansea, South Wales, Metallurgist,
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 reduction of argentiferous and auriferous copper
ores, mattes, or compounds, and consists of a process of reduction whereby
practically no loss beyond that of the usual assay methods, is made, of either the
copper, gold, silver or lead, when present, and the product is an argentiferous and
auriferous alloy of copper, in a condition suitable for further treatment for the
production of metallic or refined copper and the collection of the gold and silver by
known electrolytical or other means, the lead, where present, being absorbed in a
leady slag, from which it is easily recovered.
It is well known that in all processes at present carried out for the reduction of
argentiferous and auriferous copper ores from which matte may be made, there is
practically little or no loss until the final process of "roasting" or "Bessermerising'
of the concentrated matte to copper, but so soon as a liquefaction of the matte takes
place, with a blast or draught of air for oxidising purposes, the lead is entirely
volatilized or absorbed by the copper, and practically lost as a product, carrying
with it considerable silver, and the loss of silver is upwards of 6% and of copper
about 2% to 5%-
Now I have found that I can entirely avoid these losses by carrying out the
whole reduction, by providing in the charge, before smelting, a sufficiency of
oxygen in a solid condition, distributed uniformly throughout and within the
charge, to react chemically upon the sulphur or other oxidisable components of the
copper charge, and thus entirely avoiding the application of air for oxidising
purposes, as a blast or draught the oxygen of which is in a gaseous condition.
The lead where present is oxidised and I absorb it in a silicate slag from which it
can be easily recovered.
A usual method, generally at present followed, in the treatment of argentiferous
and auriferous sulphuretted copper ores, is to first concentrate the copper and the
precious metals into a regulus or "matte" of 70% to 75% copper and then to
or Bessermerize the whole of this regulus to metallic copper, and from
this copper to separate such gold and silver as are left therein, by electrolytical
decomposition or otherwise.
roast
"
Either of the operations of "roasting" or "Besserinerizing are extremely
expensive and very wasteful of the metals, especially of the silver.
Should lead be present, this has hitherto been found, though not intrinsically of
much value, a most troublesome item in the "roasting" process, partly dissipating,
and partly alloying with the copper, and in the "Bessermerizing" is volatilized and
lost in the flues, increasing the loss of silver.
In carrying out my improved process I avoid both "roasting" with external
air-draft and “Bessermerizing" with air-blast through the molten metal.
I treat

page_text: part of the ore only, to convert it into an oxide or an oxidised form of the metal,
or otherwise may add a highly oxidising salt to the charge, so as to ensure a large
percentage of oxygen in a solid form in the charge.
1 find it convenient and most suitable in dealing with sulphuretted ores to first
concentrate a part of the ore to a regulus of 70% to 75% of copper and then
calcine (at a low temperature without liquefaction) the part so concentrated, until
it is "sweet" or free from sulphur and thoroughly oxidised, or to such other pitch
of oxide or of sulphate or of mixed oxides and sulphates as may best suit the
conditions of operation. I then mix this calcined regulus or matte with a suitable
portion of a raw sulphuretted ore, in the proportion of about
2 parts of calcined regulus to
1 part of raw ore, such as Bratsberg ore; or alternatively I may mix about
equal parts of the calcined regulus of 75% copper, and of the uncalcined regulus
of the same percentage of copper.
I have found that on carrying out the final smelting under the conditions, that
I add to the mixture in a diffused condition throughout the charge, sufficient
oxygen in a solid state either in the form of oxides, or oxidising salts to combine
entirely with the sulphur or other oxydisable components in the added part of raw
ore or of uncalcined regulus, I obtain all the copper reduced to a metallic state,
carrying with it practically all the silver and gold, as indicated by original assay
of the ore without loss.
Where lead is present in the ore and resulting white metal, which is very general
up to from 2% to 6%, I remove all trouble from this ingredient in obtaining
metallic copper free from lead, and further free the lead in such a manner that
the lead is readily recovered, by mixing after oxidation of the lead according to
the quantity of lead in the charge, an amount of silica which will combine with the
lead to form a leady slag. This slag may be skimmed off from the surface of
the bath, is very free from silver, and contains no gold or copper, whilst on the
other hand the argentiferous and auriferous copper product, is free from any
particle of lead.
The lead is easily recovered from the leady slag by known means.
I submit a probable theory of the wasteful effect of an oxidising blast, as at
present used, in comparison with the action of my improved process as above
described, showing the probable cause of the great saving of the copper and
precious metals as effected by me, as follows:-
In the known " roasting process the pigs of metal are exposed to
draught of air, and heated and gradually melted down, the process lasting from
strong
24 to 36 hours, and during the whole of this time the reaction of the air on the
sulpbur of the regulus takes place only on the surface, whether of the pigs or
of the melted charge, and myriads of fine granules of regulus and copper, both
carrying the precious metals, are blown away from the surface, the action taking
place on the surface only. Directly a particle of copper is formed by the regulus
being deprived of its sulphur, the copper sinks by gravity into the regulus below,
and is immediately reconverted into regulus, to be again exposed at the surface and
blow off more particles of regulus (and copper) containing silver and gold, this
goes on until the sulphur gets too small to keep all the copper in the state of
regulus, and copper accumulates on the furnace bottom, carrying with it, in the
portions first formed, the greater part of the gold, but the silver is still held in the
regulus, and is still "blown out" by the escaping gases and lost, the amount so
lost being very heavy; part of the precious metals may be caught in the flues, but
with all precautions practised, the loss is acknowledged to be serious.
The losses of precious metals in the "Bessemerizing" process are not so well
ascertained as yet, but they are admittedly heavier than by roasting, the violent
boiling and heavy pressure of air blown through the melted rich regulus
carrying off more particles of regulus and copper (containing the precious metals)
than even the slower but more prolonged roasting.

page_text: In my improved process the action is altogether different. The mixed calcined
rich regulus and raw sulphide ore or regulus is filled into a furnace, and as the heat
increases the surface becomes pasty at first, it parts with sulphur gas (SO,) and
becomes copper, the melting and reaction extends downward and more SO, is given
off and more copper formed, always in a downward direction, and under the molten
portion of copper covered by slag, each particle of copper as it forms in nascent
condition eagerly absorbs the adjacent particles of gold and silver, and is not
further disturbed, because there is no sulphur to spare to the copper when
produced, only enough being in the charge to satisfy the oxygen. The reaction
between the sulphur and oxygen and the escape of SO, takes place under the
surface, and as the melting proceeds the depth from the surface increases, and the
escaping gases passing through the molten surface are deprived of any particles of
copper or precious metals by the molten surface through which they pass. The
melting of the complete charge of sometimes twenty tons occupies about eight or
nine hours, and proceeds with a quiet (almost still) working at the surface, yielding,
almost all the copper contained in the charge, containing all the silver and gold,
and slags poor in copper and rich in oxygen which may be used in the earlier
stages. Repeated and exhaustive trials show that practically not the slightest loss
of metals takes place, either copper, silver, or gold.
The copper (containing the precious metals) is now at the stage for tapping or
lading into water to form copper "shot" for making sulphate, (sulphate of copper,)
in which the gold and silver are recovered, or it may be refined and laded into
anodes for electrolytical decomposition and the recovery of the gold and silver,
the operation costing far less and yielding much more copper than either roasting
or "Bessemerizing."
Even a regulus of as low a percentage as 50% can be
therefore worked by my process to advantage.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed, I declare that what
I claim is :-
1st. A process for the production of an alloy of copper and the precious metals,
from argentiferous and auriferous sulphuretted copper ores, or their mattes, with no
loss under assay value of the gold and silver originally contained consisting of a
preparation of part of the charge before smelting, so that it contains oxygen in a
solid form, the uniform distribution of such oxidised portion throughout and
mixture with a raw sulphuretted portion of the original ore or of its matte in such
relative proportion as will enable the contained oxygen to uniformly and
simultaneously react upon and completely combine with the whole of the sulphur
of the raw ore or matte, and a final smelting to produce an alloy of copper and the
precious metals contained in the original charge without loss below assay value.
2nd. A process for the production of an alloy of copper and the precious metals
from argentiferous and auriferous sulphuretted ores, with no loss under assay value
of the gold and silver originally contained, consisting of a preparation of part of
the charge by concentration to a matte of 70 to 75 %% copper, a calcination of such
concentrated portion of matte to an oxidised condition, an intimate and thorough.
mixture of such calcined and concentrated portion of matte with a part of the raw
ore, in the proportion of 2 parts of calcined inatte to 1 part of raw ore (such as
Bratsberg) and a final smelting together, substantially as and for the purposes
described.
3rd. A modification of the process claimed in Claim 2 consisting of the mixture
of equal parts of calcined concentrated matte, and raw or uncalcined concentrated
matte of the same percentage of copper, for the final smelting, substantially as and
for the purposes described.
4th. In a process for the reduction of argentiferous and auriferous sulphuretted
ores containing lead, the addition to the charge when smelting of sufficient silica
to absorb the oxidised lead into a leady slag, free from the precious metals, and

page_text: with little copper, the removal of the lead from the leady slag by known means,
and the utilization of the highly oxidised slag free from lead in the earlier stages
of concentration of further ore, substantially as described.
Dated this 6th day of July 1896.
FELL & JAMES,
1 Queen Victoria Street, London, E.C., Agents for the Applicant.