An Improved Method or Process for the Production of Zino or Spelter from Ores or Compounds containing the same.
Year: 1891

page_text: CUBLI DJELN DI MUITIATION
An Improved Method or Process for the Production of Zino or
Spelter from Ores or Compounds containing the same.
I, CHRISTOPHER JAMES of Ida Villa Swansea in the County of Glamorgan,
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 an improved method of, or process for producing
metallic zinc from any ores or compounds containing the same and has for its object
the diminution of the usual known calcining operations, the utilisation of the natural
sulphur of the ore to assist or effect reduction, the employment of reverberatory or
gas furnaces instead of the costly and troublesome retort furnaces hitherto used,
the greater percentage of metallic zinc recovered from the ore, and the better
collection of the zinc in a distinct condenser avoiding the present heavy losses
through cracked retorts, imperfect clay connections and waste of metal in the retort
refuse.
In the ordinary methods now in use zinc ores are calcined till all the zinc present
either as carbonate or sulphide is changed to an oxide. This is then mixed with
coal or other carbonaceous matter placed in retorts, a large number of which are
arranged in the same furnace and subjected to a great heat. The oxide of zinc
formed by the calcination is reduced by the coal added to the charge, as expressed
by the equation 2 ZnO + C 2 Zn + CO,. The zinc thus reduced to metal is at
once volatilised by the heat at which the furnace is worked, and leaves as gas the
gangese of the ore and the unconsumed coal. This gas is condensed in the cooler
part of the retort and in suitable connections outside the retorts. This process in
oxceedingly wasteful and expensive. The zinc is only very partially reduced by
the coal, and so much zinc is left in the retort refuse, that ores containing a large
percentage of zinc are not as profitably worked as they should be owing to great
refuso: enormous losses occur through the cracking and breaking of the clay retorts,
and the process is generally extravagant in labour, coal and zinc.
In my new process described herein for the first stop I may (as one alternative)
calcine only a portion of the ore until all the sulphur is driven off and all the zinc
is oxidised to a high or low degree of oxidation.
This calcined portion I mix with such a portion of raw zinc sulphide (Blende) as
will suffice when the whole is heated together as a second step in my process to
reduce the whole of the oxide of zinc in the calcined portion itself as well as the
sulphide itself by their mutual reaction to zinc and SO, or as an equivalent but
alternative process for the first step I so limit the calcination of the ore (mixed
ores or otherwise) that sufficient sulphur is left in the ore (either as undecomposed
sulphide or as sulphate formed by the calcination) to effect the after reduction such
as would be otherwise performed by the added portion of zinc Blende (sulphide) as
above described for the second step in a reducing furnace.
The above mentioned oxide of zinc may be produced from carbonate ores of zine
by burning in kilns as usually practised or in reverberatory furnaces and utilised in
my above process for the reduction of Blende or raw sulphides of zinc.
The charge of mixed calcined and raw ore as above (or alternatively of partially
calcined or sulphated ore only) I put conveniently for the second step of my process
in a reverberatory furnace, in which I maintain a reducing atmosphere, and in which
I can apply any amount of heat without fear of loss from the breaking of clay
retorts and consequent leakage. The zinc entirely reduced by the reaction of the
mixed oxides and sulphides or of the sulphated zinc under the reducing atmosphere
s perfectly volatilized by the high degree of heat maintained in the furnace. The

page_text: volatilized zinc is conducted into a separate condensing chamber,, surrounded by a
water jacket casing or partly filled with tubes through which the zinc gas passes,
the tubes being surrounded with water. In the chamber or tubes the zinc is
condensed and is then laded out ready for the market.
-
The reduction as above described where the sulphur in the ore is utilised in
reduction is more natural and perfect than when coal or similar carbonaceous
matter is used. The reaction of my method under the first alternative is chemically
expressed by the formula 2 ZnO + ZnS 3 Zn + SO, that is two parts by weight
of zinc oxide mixed with one part of zinc sulphide, when heated together, give all
the zinc free and all the sulphur and oxygen combined as sulphurous anhydride.
In my second alternative the sulphur and O are present in exact proportion
necessary for its complete reduction under heat with a neutral atmosphere.
One great superiority of this process arises from the collection and condensation
of the zinc being effected in a large distinct and easily accessible chamber, or in
an apparatus equally open to frequent examination, so that no loss of zinc takes
place through leakage. Whilst the small amount of oxide of zinc which may be
formed by any free oxygen which can pass into the furnace I' collect in suitable
flues and chambers to be again used as calcined zinc ores.
The expense of working such a furnace will be very small compared to the
ordinary retort furnace, the repairs much less, whilst the labour and loss of time
caused by the breaking and consequent changing of damaged retorts is entirely
avoided.
By my above method of reduction, ores.containing less than ten per cent. of zinc
can be profitably worked, in consequence of the decreased cost following the use
to effect reduction of the natural sulphur of the ore in lien of coal which latter is
not only expensive itself, but renders the retort refuse unfit for any after treatment
for the recovery of other metals than zinc contained in the ore. By my method
the refuse from the retorts or furnace will be in a better condition for further
treatment, whilst very nearly all the zinc originally present in the ore is driven off
and condensed.
It is obvious that my process so far as the utilization of the natural sulphur of
the orcs to effect the reduction of the oxide of zinc might be carried on in the
ordinary retorts, with some advantage, as regards the present system of extreme
calcination and subsequent carbonisation for reduction but a much better advantage
would be obtained by the use of reverberatory or gas furnaces as herein before
described.
Although my process has been described as applied (probably most beneficially)
to a mixture of calcined (oxidised) and uncalcined sulphides of zinc, and to the
partial calcination of a sulphide ore so as to retain a due proportion of the sulphur
to react upon the oxygen present, it has been before pointed out that the calcined
or oxidised sulphide ore or Blende may be replaced by any natural or other oxide
of zine and further I now point out that the sulphide of zinc may be replaced by
sulphur, added in any form either as sulphur, or a sulphide of iron (iron pyrites)
or if any other metal or earth, the mutual reaction of the sulphur and oxygen to
free the metallic zinc would be the same as hereinbefore described and therefore
within the essence of my invention.
Having now particularly described and ascertained the nature of my inven
tion and in what manner the same is to be performed I declare that what I
claim is :-
1st. The process for the treatment of zinc ores consisting of first calcination of
a part of the ore.to the form of an oxide, and thereafter mixing the calcined ore
with a proportion of crude zinc sulphide (Blende) for reduction conveniently in a
reverberatory or suitable furnace, the quantity of sulphide, to calcined ore, being
so proportioned that they are both entirely reduced to metallic zinc and. SO, by
mutual reaction, the zinc being volatilised and collected by condensation in a
chamber distinct from the furnace substantially as described.

page_text: 2nd. The equivalent and alternative process for the treatment of zinc ores con-
sisting of first the cessation of the calcination of the ore when brought up to the
form of sulphate and thereafter a reduction of the same to zinc by heating in a
reverberatory or suitable furnace, the zinc being volatilised and collected by con-
densation in a chamber distinct from the furnace substantially as described.
3rd. In a process for the treatment of zinc ores the admixture in a suitable
neutral furnace or retort of the oxide and sulphide of zinc or of the oxide of zinc
and sulphur or sulphides of any metal or earth in such relative portions that by
heat the sulphur and oxygen will mutually react to entirely reduce the zinc to a
metallic but vaporized condition, substantially as described.
Dated this 7th day of July 1891.
FELL & WILDING,
1, Queen Victoria Street, E:C., Agents for the Applicant.
FELL & WILDING,
1, Queen Victoria Street, E.C., Agents for the Applicant.