Improvements in the Treatment of Complex Ores.
Year: 1898

page_text: PROVISIONAL SPECIFICATION.
Improvements in the Treatment of Complex Ores.
I, GUY DE BECHI, of 17, Boulevard de la Madeleine, Paris, France, Chemical
Engineer, do hereby declare the nature of this invention to be as follows:
1
This invention relates to the treatment of zinc bearing complex ores, such as
Broken Hill ore. Heretofore much difficulty has been experienced in the extrac-
tion of the metals from such ores, and the object of my invention is to obviate
this difficulty and to enable the metals to be extracted from such ores by a wet
process in which useful and valuable bye-products are obtained, a part of which
may be employed in the carrying out of the process. Another object of my
invention is to facilitate the roasting of ores containing a large proportion of zinc
blende, which, under the usual conditions of a chloridizing roasting are liable
to become pasty and thereby incapable of a dead roast.
According to my invention I treat ores of the kind referred to in the following
mauner:-
The pulverized ore and sodium chloride or other salt rich in alkaline chlorides,
are roasted separately, the gases proceeding from the roasted ore being caused
to pass over the said chloride salt. Or I may mix a small quantity of this salt,
say 5% or 10% by weight with the ore before heating, the remainder of said
salt being heated in the separate furnace. This small percentage of sodium
chloride is not sufficient to render the mass pasty and hence a dead roast of the
ore can be obtained. Steam is injected into the furnaces, in suitable quantities,
Hydrochloric acid, chlorine and sulphurous and sulphuric anhydride are given
off during the roasting of the ore; in cases where a small quantity of sodium
chloride is mixed with the ore probably some vaporized metallic salts will also
be given off. In passing over the sodium chloride the sulphurous and sulphuric
anhydride, in the presence of air and moisture (steam), combine with the sodium
of the salt to form salt cake (sodium sulphate), while further quantities of hydro-
carhloric acid are produced.
In the cases of ores that do not give off a sufficient quantity of sulphurous
compounds to form the sodium sulphate, I may roast at the same time, either
mixed with the ore or in a separate furnace, a suitable quantity of pyrites.
The gases and vapours, consisting mainly of hydrochloric acid, passing off
from the furnaces are condensed in suitable condensing towers. Some or all
of the acidulated water from these towers containing the condensed gases and
vapours is then utilised for leaching or lixiviating the roasted ore, any sulphuric
acid which such water may contain being previously eliminated preferably by
the addition of a sufficient quantity of calcium chloride or lime.
By this lixiviation a solution is obtained which will contain, according to the
nature of the ore under treatment, the chlorides of, say, zinc, copper, silver, man-
ganese, sodium and calcium. The residue will contain, say, lead, iron in the
form of the insoluble subsalt or oxide, zinc and silver. If an excess of hydro-
chloric acid has been employed in the leaching fluid (iron may also be present
in the solution as a chloride, and in such case it may be removed by adding to

page_text: such solution some fresh roasted ore and lixiviating the same therewith, when
the zinc of the zinc oxide contained in such ore will combine with the chlorine
of the ferric chloride, and the iron will be deposited in the form of the insoluble
subsalt or hydrated oxide. This step will also neutralize the solution.
Any silver contained in the solution is then precipitated with copper or zinc
and the remaining metals are successively separated by fractional precipitation
with lime or other alkaline earth or with soda ash. For instance, supposing
the solution to contain zinc chloride, manganese chloride and cupric chloride
then a quantitative analysis is made to determine the amount of cupric chloride
in the solution and sufficient lime is added to act upon the chlorine of such salt
and thus separate the copper as a hydrate. As the lime will not attack the other
chlorides until all the cupric chloride is decomposed, and as only sufficient lime is
added to decompose this chloride, none of the other metals are separated. The
solution is then filtered and the filtrate is similarly treated so as to separate the
zine; and subsequently, if it be desired to do so, further similarly treated to
separate the manganese.
The metals will thus be precipitated in the form of hydrates or hydrated
oxides which are subsequently reduced or otherwise treated in any desired
manner.
The residue of the lixiviation is treated in a cupola furnace for the recovery
of the metals therein, in the known manner.
The filtrate remaining after the separation of the metals can be employed for
precipitating sulphuric acid or soluble metallic sulphates in the leaching liquid.
Dated this 4th day of November 1898.
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, W.C.,
Agents for the Applicant.
Improvements in the Treatment of Complex Ores.
I, GUY DE BECII, of 17, Boulevard de la Madeleine, Paris, in the Republic of
France, Chemical Engineer, 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 complex zinc bearing ores, such as
Broken Hill ore. Heretofore much difficulty has been experienced in the extrac-
tion of the metals from such ores; the chief object of my invention is to obviate
this difficulty and to enable the metals to be recovered by a wet process in the
form of compounds capable of being readily reduced, or converted into saleable
salts. Another object of my invention is to facilitate the roasting of the ore,
and to obtain useful and valuable bye-products during such roasting, a part of
which bye-products may be employed in the carrying out of the process.
According to my invention I treat ores of the kind referred to in the following
manner:-
The pulverized ore and a chloridising salt such as sodium chloride or other salt
rich in alkaline chlorides, are roasted in separate chambers or receptacles, the
gases proceeding from the roasted ore being caused to pass over or about and in
contact with the said salt. Or I may mix a small quantity of this salt with the ore
before heating, the remainder of said salt being heated separately. The propor-
tion of the quantity of salt mixed with the ore varies from five (5) to ten (10)
parts by weight of sodium chloride, or its equivalent, to one hundred (100) parts

page_text: of ore, according to the nature or composition of the latter. This small propor
tion of sodium chloride is not sufficient to render the mass pasty, and hence a
dead roast of the ore can be obtained. Superheated steam is injected into the
furnaces, in suitable quantities.
Hydrochloric acid, chlorine, and sulphurous and sulphuric anhydrides are
given off during the roasting of the ore and the chloride salt. In cases where a
small quantity of sodium chloride is mixed with the ore, probably some vaporised
metallic salts will also be given off. On coming in contact with the sodium chlor-
ide the sulphurous and sulphuric anhydrides, in the presence of air and water
(steam) combine with the sodium of the salt to form salt cake (sodium sulphate),
while further quantities of hydrochloric acid are produced.
In the cases of ores that do not give off a sufficient quantity of sulphurous
compounds to form the sodium sulphate, I roast at the same time, either mixed
with the ore or in a separate receptacle or furnace, a quantity of pyrites sufficient
to supply the required amount of sulphur. The iron contained in the pyrites
also serves to facilitate the recovery of the lead from the residue of the leaching
process hereinafter described.
The gases and vapours, consisting mainly of hydrochloric acid, passing off
from the furnaces are condensed in suitable condensing towers. Some or all of
the acidulated water from these towers containing the condensed gases and
vapours is then utilized for leaching or lixiviating the roasted ore.
By this lixiviation a solution of various metallic chlorides is obtained, accord-
ing to the nature of the ore under treatment. If the roasted ore, as is generally
the case, contain some soluble sulphate, liquor containing dissolved calcium
chloride (which liquor is obtained during my process as will be hereinafter des-
cribed) is added to the said acidulated water before leaching, The calcium of
the calcium chloride combines with the acid radical of the soluble sulphate to
form insoluble calcium sulphate. The calcium chloride will also in the same
manner eliminate any sulphuric acid which the acidulated water may contain,
so that the latter is converted into a fairly pure hydrochloric acid solution; and
the filtrate obtained from the subsequent lixiviation of the roasted ore with this
solution then contains all the metals exclusively in the form of chlorides.
The solution may contain a small quantity of silver chloride, which is soluble
to a slight extent in solutions containing large quantities of soluble chlorides.
Thus the solution obtained may contain, for example, the chlorides of zinc,
copper, silver, manganese, sodium and calcium. As however, it is better that
the silver be retained wholly in the residue in an insoluble form, I convert the
silver chloride into sulphide (which is quite insoluble in a solution of metallic
chlorides) by adding a very small quantity of lime and calcium sulphide to the
said solution. The whole of the silver is thus precipitated in the form of sul-
phide and remains with the residue. This residue will now contain, say, lead,
silver, gold, iron in the form of the insoluble sub-salt or oxide, and a certain
quantity of zinc which will always remain in the residue even when the hydro-
chloric acid is used in excess.
If an excess of hydrochloric acid has been employed in the leaching fluid, iron
may also be present in the solution as a chloride, and in such case it may be
removed by adding to this solution some fresh roasted ore and lixiviating the
same therewith, when the zinc of the zinc oxide contained in such ore will com-
bine with the chlorine of the ferric chloride, and the iron will be deposited in
the form of the insoluble sub-salt or hydrated oxide. This step will also neutral-
ize the solution.
In proceeding with the treatment of the solution, if the precipitation of any
silver chloride contained therein has not been effected by the addition of lime and
calcium sulphide, this silver is first precipitated with copper or zinc, and the
remaining metals are successively separated by fractional precipitation with lime
or other alkaline earth, or with soda ash. For instance supposing the solution to
contain zinc chloride, manganese chloride and cupric chloride, then a quantita-

page_text: tive analysis is made to determine the amount of cupric chloride in the solution
and sufficient lime is added to act upon the chlorine of such salt and thus separ-
ate the copper as a hydrate. As the lime will not attack the other chlorides until
all the cupric chloride is decomposed, and as only sufficient lime is added to
decompose this chloride, none of the other metals are separated at this stage.
The solution is then filtered and the filtrate is similarly treated for the separation
of the zinc; and subsequently, if it be desired to do so, further similarly treated
to separate the manganese.
The metals will thus be precipitated in the form of hydrates or hydrated
oxides, which is a very convenient form for producing the salts of said metals.
If, for example, the copper is required in the form of copper sulphate, the hydrate
of copper is dissolved in sulphuric acid and copper sulphate crystallized out from
the solution in the well known manner. Zinc salts may be similarly obtained
by dissolving the hydrate of zinc in an appropriate acid."
The residue remaining after the leaching of the roasted ore contains, besides
the iron, practically the whole of the lead and silver of the ore as well as any
gold that may be present and a certain quantity of zinc as previously explained.
This residue is treated in a cupola or other suitable furnace, and an alloy thus
obtained which contains practically all the lead, silver and gold in the ore, the
iron remaining in the slag.
During this treatment a certain quantity of lead and, if the right composition
for the slag is used, nearly all the zine remaining in the residue, are volatilized
and driven off as fumes, and are condensed in suitable chambers or towers. The
product of such condensation is added to fresh roasted ore prior to the leaching
thereof. The zinc is dissolved in the form of chloride, and the lead remains in
the insoluble residue.
The last filtrate remaining after the separation of the metals contains a large
quantity of dissolved calcium chloride; this liquid can be employed for elimi-
nating from the roasted ore or from the leaching liquid any soluble sulphates or
sulphuric acid, as previously explained.
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:
1. The method of treating complex ores, consisting in roasting the ore and an
alkaline chloride salt in separate receptacles into which steam is injected, passing
the vapours and gases from the ore over and in contact with the salt so as to
produce a sulphate, recovering the acid gases issuing from the roasting chambers,
lixiviating the roasted ore with liquor containing said acid gases, and separating
the metals dissolved in said liquor by fractional precipitation, substantially as
described.
2. In the method referred to in Claim 1, the roasting of pyrites with the ore
substantially as and for the purposes specified.
3. The method of treating complex ores substantially as herein described and
for the purposes specified!
Dated this 4th day of Arronet 1800
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, W.C.,
Agents for the Applicant.