Improvements in or appertaining to the Smelting of Complex Sulphide Ores containing Zinc and Lead.
Year: 1898

page_text: Date of Application, 26th July, 1898
Complete Specification Left, 25th Apr., 1899-Accepted, 8th July, 1899
PROVISIONAL SPECIFICATION.
Improvements in or appertaining to the Smelting of Complex
Sulphide Ores containing Zinc and Lead.
I, JOHN ARMSTRONG, of 13, Sherborne Lane, in the City and County of London,
Metallurgical Chemist, do hereby declare the nature of this invention to be as
follows:
This invention has for its object improvements on my process set forth in
Patent, No. 22361 of 1896. In this specification a process is described whereby
roasted or raw pulverized refractory ores or mattes containing lead and zinc
are mixed in a fine powder with carbonate, bicarbonate or nitrate of sodium or
potassium and lime flux and carbon and are heated out of contact of air. In
the specification the lime is mentioned as combining with the silica and as acting
as a flux and in the third claim it is only mentioned by the words
necessary flux," still throughout the specification it would appear what I then
thought the fact, that lime was necessary for the process.
and the
One improvement in my process consists in extracting the silica by any well-
known means prior to the re-action, in which case no lime is required, also in
those ores which do not contain silica the lime as a rule is quite unnecessary.
One of my improvements therefore in the aforesaid process consists in doing
without lime. Secondly I have found that the more finely the ore is divided
before treatment and the more intimate the mixture of the materials the better
is the result and that the charge should preferably after being ground and
mixed be able to pass through a sieve of at least 30 meshes to the linear inch;
a 60 mesh sieve will however give still better results. The actual degree of
fineness is only limited by considerations of economy in the grinding or other
process and inside these limits the finer the particles are the better. The carbon
especially should be ground extremely fine and preferably before admixture with
the charge or a carbonaceous substance already in the state of fine powder such
as soot can be used. The metal which is reduced by these operations is princi-
pally lead and where there is a deficiency of lead and there is a large percentage
of precious metals it is desirable to add lead oxide or galena to the charge the
lead carrying with it practically all the silver and gold while the slag carries
practically all the zinc in a finely divided condition and largely as a sulphide.
From my experiments so far I am convinced that the re-action is mainly due to
the formation of nascent alkali metal which re-acts on the galena but does not
appear to have even a partial effect on the blend or pyrites, and it is this limitation
of the effect of the nascent sodium which permits of the truly remarkable separa-
tion of the lead silver from the zinc, this separation being effected at the com-
mencement of the process and thus later steps in the method only effect the
separation of the individual metals in the separate first products. I have further
found it very desirable previous to mixing the raw or ground ore with the other
reducing materials to separate all or the larger portion of the barren calcareous
or other matrix from metalliferous minerals in the crushed ore by means of any

page_text: known apparatus. or method such as jigging, vanning, buddling or by water
concentration. Doing this obviates the necessity for a flux and thus a larger
amount of ore can be reduced in a given sized furnace and with less waste. The
ground intimately mixed charge of ore alkali and carbon is fed on to the hearth
of the reducing furnace in a strictly reducing atmosphere and kept at a suitable
temperature say from a red to an orange heat. The furnace described in the
original specification is well adapted for the requirements of the process, but I
do not confine myself to this variety of furnace as almost any furnace in which
the charge is heated sufficiently and out of contact of air or only in a reducing
atmosphere and which gives sufficient tapping and slagging facilities may be
employed. The hearth indeed may be stationary oscillating or revolving and
rabbling or mechanical agitation of the charge during reduction can be used
with advantage to the thoroughness of the main separation of silver lead from
zinc which occurs in this re-action. The time of reaction varies naturally with
the type of furnace, variety of ore and degree of charge operated upon and may
be from a quarter of an hour to two hours. The furnace can be arranged to
work continuously with a slow continuous feed and continuous or intermittent
tapping of reduced metal and zinc bearing slag. The tapped silver lead and
gold bullion is removed for further treatment by any known refining or desilver-
izing process for effecting the final separation of gold, silver and lead from
each other. The zinc slag may be at once distilled in suitable retorts for the
recovery of the zinc in the metallic condition or treated with copper as originally
specified in my former specification, but if the soda salts are recovered and the
distillation conducted to recover the zinc without occupying so much space in
the retorts the following routine is preferable. The cooled slag is roughly
broken and moistened with water, rapid disintegration occurs and the mass in
a few hours is reduced to a moist powder. This powder is then lixiviated, per-
colated or leached with water for the. recovery of the soluble soda salts present.
The alkali can be recovered from these solutions in several well-known ways
for re-use. The washed residue consisting of finely divided sulphides of zinc,
iron, etcetera, with silica, and other earthy matter is dried and preferably calcined
in a separate furnace and in an oxidising atmosphere whereby the sulphides
are for the most part converted into oxides. These residues are finally mixed
with a suitable proportion of finely ground carbon with or without the addition
of lime, clay or the like, and charged into ordinary zinc distillation apparatus.
I have found however that if before the slag has been allowed to come in contact
with air or moisture sufficient to decompose it, it be at once distilled with car-
bon, a large part or even the whole of the zinc can be distilled off in a much
shorter time than oxide of zinc can be reduced and distilled with ordinary car-
bon, but in this case it is preferable to use a large excess of carbon so as to
keep the materials in a pasty instead of liquid condition. In working my
Patent No. 22361 of 1896 I have become convinced that the actual cause of my
success consists in the formation of nascent alkali metal and other modes of
making nascent alkali metal can be used, but they are not nearly as economical
and cheap as the production of the said nascent alkali metal by the re-action of
carbon on carbonate of soda. Metallic iron and the hydrate oxide or carbonate
of the alkali metal can be employed provided the iron be in a state of sufficiently
fine division and intimate mixture or the heat be sufficiently raised to bring
about the re-action. In such case the iron simply takes the place of a part or
the whole of the carbon in my original process, and it is obvious that the oxide
or hydrate of an alkali metal can be substituted for the carbonate in my original
process.
W. P. THOMPSON & Co.,
Of 6, Lord Street, Liverpool,
Patent Agents for the Applicant.

page_text: Improvements in or appertaining to the Smelting of Complex
Sulphide Ores containing Zinc and Lead.
I, JOHN ARMSTRONG, late of 13, Sherborne Lane, but now of 46, Lombard
Street, in the City and County of London, Metallurgical Chemist, do hereby
declare the nature of this invention and in what manner the same is to be per-
formed, to be particularly described and ascertained in and by the following
statement:-
This invention has for its object improvements in the details of my process
set forth in Patent No. 22361 of 1896. In the specification of that patent, a
process is described whereby roasted or raw pulverized refractory ores or mattes
containing zinc and lead are mixed in a fine state of division with an alkali
metal salt capable of being easily decomposed at the heat used, lime flux and
carbon being also added, and the whole thoroughly mixed and heated out of
contact of air. In the specification the lime is mentioned as being used to enter
into combination with the silica, and thus act as a flux, and in the third claim
it is only mentioned by the words "and the necessary flux," still throughout
the specification it might appear that lime was necessary to the process.
My first improvement consists in doing without lime by extracting the silica
by any well known chemical or mechanical means prior to the re-action, or
using ores devoid of silica, in either of which case no lime as a rule is required.
My second improvement consists in dividing the ore and mixing the materials
as finely as practicable, as the more intimate the mixture, the better is the
result. I therefore prepare the materials so that they shall be able to pass
through a sieve of at least 30 meshes to the linear inch, passing through a sieve
however of 60 meshes will give a still better result. The actual degree of
fineness is only limited by considerations of economy in the grinding or com
minuting. The carbon should be ground extremely fine or carbonaceous matter
in a state of fine powder such as soot can be used. In practice however I prefer
pulverized anthracite coal to any other, and in mixing I prefer to first mix the
alkali and anthracite before adding the ground ore. My third improvement
consists in adding lead, either in the form of metallic lead, lead oxide, carbonate,
sulphate, sulphide, or other suitable salt of lead, where the ore is deficient in
that metal, and has a large percentage of precious metals. This lead or lead
oxide or salt must be intimately mixed with the charge. By its reduction the
precious metals in the ore under operation are secured, as they are found all
to collect in the metallic lead. The zinc contents in the ore are found in the
slag in a finely divided state mainly oxide, but mixed with other compounds.
of zinc and alkali, and all such baser metals that may have been present in the
zine ore, such as iron and aluminium. From my experiments I am convinced
that the re-action is mainly due to the formation of nascent alkali metal which
re-acts on the galena, reducing it to metallic lead, and that if there be sufficient
of this in or with the ore, it will carry all the precious metals down with it.
Nascent alkali acts also partially upon the zinc blend transforming the greater
portion to an oxide and forming a mixture of zinc compounds extremely finely
divided. This mixture may even contain a small percentage of finely divided
metallic zinc as I have obtained traces of metallic zinc in the reduced lead
when iron is present, as it usually is in zinc blend ores. The iron appears to be
partially acted upon by the nascent alkali metal, and is thus partly reduced to
the metallic state, as I have found traces of iron also in the reduced lead. The

page_text: iron however having greater affinity for sulphur than the other metals of the
ore is generally found in a state of sulphide. My fourth improvement consists
in the process of distilling the zinc. This can be done as set forth in my former
specification by intimately mixing it with carbon and distilling in the usual
manner or adding copper. If however the soda salts are recovered and the dis-
tillation conducted so as to recover the zinc also, then the following routine is
preferable, since it occupies less space and a larger amount of material can there-
fore be operated upon at a given time and at less expense. The cooled slag is
either thrown upon a grate, through which vapour, steam or moist air is blown
or it is piled in a heap and exposed to the weather, when rapid disintegration
takes place and the mass gradually falls to powder. This powder is then lixi-
viated, percolated or leached with water for the recovery of the alkaline salts
present, and the recovery effected in any manner wellknown. The washed
residue consisting mainly of finely divided oxide of zinc, sulphide of iron, sili-
cates and other earthy matter is dried and preferably calcined in a separate
furnace, and if iron sulphides are present, in an oxidizing atmosphere, whereby
the sulphides are for the most part converted into oxides. This latter roasting
is not however really essential to the process, as the slag after being washed can
be distilled in the ordinary manner employed in distilling zinc from zinc car-
bonate or zinc oxide. The slag, roasted or unroasted, is mixed with a suitable
proportion of finely divided carbon and with or without the addition of lime,
alumina, clay, or the like, and is charged into the ordinary zinc distilling
apparatus. In my former specifications I described a furnace for reducing the
lead and its concomitant metals, but I do not confine myself to this variety of
apparatus, as I find almost any furnace, in which the charge is heated suffi-
ciently and out of contact of air or only in a reducing atmosphere, and which
allows sufficient tapping and slagging facilities, may be employed. The hearth
may be stationary, oscillating or revolving, and rabbling or mechanical agita-
tion of the charge during reduction can be used with advantage to the thorough-
ness of the main separation of the silver and gold with the lead from zinc which
occurs in this re-action. The furnace can be arranged to work continuously
with a slow continuous feed and continuous or intermittent tapping of reduced
metal and zinc-bearing slag. The tapped silver, lead, and gold bullion is
removed for further treatment by any known refining or desilverizing process
for effecting the final separation of gold, silver, and lead, from each other. In
working my Patent, No. 22361 of 1896, I have become convinced that the actual
cause of my success consists in the formation of nascent alkali metal. Other
modes of making nascent alkali metal therefore can be used, but they are not
nearly so economical and cheap as the production of the said nascent alkali
metal by the re-action of the carbon and carbonate of soda. Metallic iron and
the hydrate or oxide of the alkali metal can be employed, provided the iron be
in a state of sufficiently fine division and intimate mixture and the heat be suffi-
ciently raised to bring about the re-action. It will be found however much
more expensive and difficult to work with than carbon, and I merely mention
this, and that the oxide or hydrate of an alkali metal can be substituted for the
carbonate in my original process in order to prevent others from claiming this
as a further modification of my invention, my invention consisting practically
in the application of nascent alkali metal for this purpose.
Having now particularly described and ascertained the nature of my said in-
vention, and in what manner the same is to be performed, I declare that what I
claim is;-
The various improvements on my patented process, No. 22301 of 1896, sub-
stantially as herein described, and only in combination with or parts of an entire
process for treating complex sulphide ores (or slags therefrom) containing zinc
namely (a) the preliminary elimination of gangue as far as practicable, and the
consequent carrying on of the process without the use of lime.

page_text: (b) The addition of lead when the original ores are rather poor in that metal.
(c) The preliminary and very fine grinding of the materials.
(d) The treatment of the slag herein set forth.
(e) The application of nascent alkali metal for the smelting of complex sul-
phide ores containing zinc when the nascent alkali metal is produced in other
ways from that set forth in my aforesaid patent.
Dated this 24th day of April 1899
WM. P. THOMPSON & Co.,
Of 6, Lord Street, Liverpool, Agents for the Applicant.