Improvements in Method and Apparatus for Reducing Zinc Ores and other Volatile Metals in Blast Furnaces.
Year: 1898

page_text: Date of Application, 2nd Apr., 1898-Accepted, 10th Sept., 1898
2
COMPLETE SPECIFICATION.
Improvements in Method and Apparatus for Reducing Zinc Ores and
other Volatile Metals in Blast Furnaces.
I, AMEDEE MATHURIN GABRIEL SEBILLOT, of 60, Boulevard de Clichy, Paris,
France, 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:-
The dressing of zinc ores in blast furnaces has not been realized hitherto, not-
withstanding the numerous trials that have been made; however the metal has
been produced in a pulverulent form known as zinc flower; zinc flower seems to
be formed of particles of metal covered with a very thin coat of carbonate of
zinc, oxide of zinc or zinc flower having a very great affinity for carbonic
anhydride,
To obtain metallic zinc capable of being cast in bars, it was necessary to make
great modifications in the blast-furnace which realize the theoretical conditions
also practised in other methods of extracting zinc, allowing liquid zine to be
obtained.
Such is the object of the present invention, but before setting forth and
describing the apparatus with which it is to be performed, the principles upon
which the extracting of zinc is founded and the reactions which must be accom-
plished to separate the metal must be indicated.
With the Belgian, Silesian or English methods, the principle is always to reduce
zinc flower, whether it is produced by oxydized zinc-carbonate or by zinc-sulphuret;
zinc-oxide with an excess of coal produces zinc and carbonic oxide gas; the metal
is condensed near the retort where the reaction is operated, since a short nozzle
of sheet-iron is sufficient to operate the condensation in the liquid state.
We see, therefore, that two conditions are necessary for obtaining the metal,
an excess of coal so as to distil the zinc in a reducing atmosphere and a condensation
which is not too sudden, that is to say, zinc vapour must not be caused to pass
without transition from the gaseous to the solid state.
Indeed, zinc becomes firm at 410° (C.) and. deliquates at 9320 (C.), the result of
which is, that the condensating heat must be above 410° and below 932°.
If these principles are not observed, if the atmosphere, in which the distillation
is operated, contains even a small quantity of oxygen and carbonic anhydride and
if the condensation is operated as usual with the assays of dressing zinc in blast
furnaces, we obtain only zinc flower and a very great part is lost with the zinc-
powder carried away. Such is the result I have obtained with a furnace in which
I have dressed zinc-carbonate; the condensation was operated in a cast iron pipe
where the zinc was quickly accumulated in the form of zinc flower, whilst a part
was lost in the chimney.
These experiments and those made by other inventors for the same purpose
have suggested to me the arrangements described hereinafter.
There are two cases to be considered, according to dressing zinc-carbonate or
zinc-sulphuret.
If we employ zinc-carbonate, it has been previously calcined in order to expel
the carbonic anhydride, whereby we obtain zinc-oxide to be dressed in the furnace.

page_text: The chemical formula is then simply ZnO + C
=
Zn + CO.
If we employ zinc-sulphuret (ZnS) the sulphur must be removed by means of a
dissulphuring agent, such as metallic or oxydized iron, or in certain particular
cases, oxydized copper ores, the affinity of copper for the sulphur being still
greater than that of iron; but this latter condition will rarely be realized and
iron especially should be employed.
The reaction is then 2 ZnS + Fe2O3 + C
=
2 Zn + 2 FeS + 3 CO + (n-3) C.
The result of the operation is consequently metallic zinc and a ferruginous
matt.
Of course, in both cases, the batches must be formed in accordance with the
analysis, so as to form a fusible and essentially basic slag, the zinc easily.com-
bining with the dross when the latter is acid.
These principles being set forth, the following description gives the arrange-
ments according to which the operation is made. The blast furnace is of the well
known type called "water-jacket," but it is hermetically closed at the top and the
gas can escape only by a lateral hole, intended for the outlet of the reducing
mixture carrying away the vaporized zinc.
For this purpose, this gas-hole is placed between two series of blast pipes, one
above and the other below the gas-hole, at a distance so calculated that the
reactions have all time to be effected and the air from the blast the time to con-
sume completely.
For the sake of security and in order to assure the reducing of the atmosphere,
the gas-hole is succeeded by a chamber for reducing the carbonic anhydride, that
might remain in the mixture by forcing it to pass over charcoal; the mixture must
pass through this chamber to reach the condenser.
The complete apparatus is shown in elevation Fig. 1, in a vertical section
Fig. 2, and in plan Fig. 3.
The furnace is formed of a metallic casing A B with water circulation; this
casing is succeeded by another simple one in sheet-iron C 1) supporting the filling
apparatus.
The water-circulation casing rests upon a brick-mass foundation forming hearth
for the fixed products of the fusion; it is provided with holes for the introduction
of the air from the blast, one series of holes E E E being arranged all around at
the top part, the other series F F F at the lower part; it is between these two
rows of blast pipes that the gas-hole G is made; this hole is furnished with fire-
proof parts or, better, with water circulation tubes H H H forming a grating to
hold the combustible and the substance passing into the furnace; another
grating G in fire-bricks, surrounds the space I containing charcoal supplied by
the cylinder J as soon as it is consumed; this cylinder, the hoops and the condenser
are formed by one metallic casing with a brick lining.
The gas after passing through the bed of charcoal goes through the flue K,
where the zinc begins to condense, to accumulate in the vat L which is provided
with a tap-hole M; the gas passes over the obturator N and follows a flue N¹
having an ascending slope of a length calculated so that there remains a tempera-
ture of about 700° to 800° at its end finally it enters the powder-chamber O
where the zinc, which has escaped condensation is completely condensed; finally
after passing around the obturator P the gas is evacuated through the chimney Q.
The whole apparatus is hermetically closed, as will be seen.
The air blown by the upper pipes passes through the matters from top to
bottom that, blown by the lower pipes passes from bottom to top and the two
currents pass together through the outlet-hole between the two rows of blast-pipes.
The upper part of the furnace forms a neutral space, the filling apparatus form-
ing an air-tight closing and allowing no communication between the interior of
the furnace and the outer air. For this purpose, the upper end of the casing C D
is provided with a planed cast-iron flange R upon which the valve T may slide.
The valve-box U is provided with a stuffing-box through which the slide-valve-
rod V passes, the said rod being actuated by the handle lever X; the bottom part

page_text: of the hopper Y is also planed, the slide-valve being so engaged between two
smooth friction surfaces; the hopper has a cover Z' which leans on the bottom of
a groove provided with a lining of asbestos and cotton; the cover is lifted or let
down by the agency of the lever W.
The slide-valve being in place, the hopper is filled and the cover let down; then
the slide valve is operated to uncover the orifice; the charge falls and the slide-
valve is shut again for a fresh charge and so on.
A similar arrangement may be applied to the charcoal-cylinder; however as
this charcoal is consumed very slowly and only acts, as it were, as a filtering
matter to transform the small quantity of carbonic anhydride into carbon-oxide, a
double closing or a single air-tight cover may be employed, the changing of the
charcoal being necessary only at long intervals.
This furnace owing to the height of the space in which a high temperature
exists, comports with a much larger water-jacket surface than with the ordinary
water-jacket; it also comports with a greater heat; this jacket may also be used
as a boiler when the fuel is to be economised; for this purpose the water jacket
is connected with an annular reservoir ab forming steam chamber.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is:-
-
1. A method of manufacturing metallic zinc with blast furnaces by reducing
zinc-ores, such as zinc-carbonate, zinc sulphuret or mixed ores, the said method
consisting of the disoxydation of the zinc-oxide or zinc flower obtained by the
calcined zinc-carbonate, or by treating zinc-sulphuret with oxydized or metallic
iron, or also with oxydized copper-ores and by the addition of carbon in both cases,
serving as a reducing agent, the said process being effected in a hermetical double-
blast furnace, the complete disoxydation of zinc being obtained by the passage of
its vapours over incandescent coals, before reaching the condenser, the said con-
denser being placed into a double-sloped flue maintaining the temperature above
the fusion of zinc, to obtain this metal at the tap-hole, substantially as and for
the purpose set forth.
a
2. The above mentioned method and the arrangement of a furnace hermetically
closed at the top and formed by a metallic casing A B, with water circulation
and supported by brick-mass foundation, the said casing or jacket
being provided with holes to introduce the air from the blast, these holes being
arranged at the top and at the bottom of the furnace, and between which holes
the gas-hole G is placed, this latter being provided with water-circulation
tubes H H H forming a grating, another grating G in fire-bricks surrounding
the space I containing charcoal, which is supplied by the cylinder J, substantially
as described and for the purpose set forth.
3. In the above-mentioned furnace the combination with two rows of blast-
pipes, the upper row of which blowing air which passes through the matters from
top to bottom, the lower one forcing the air from bottom to top and the two
currents passing together through the outlet-hole arranged between these two
rows of blast-pipes, substantially as and for the purpose set forth.
4. Finally the application of the above-mentioned process and apparatus to the
treatment of all zinc-ores, such as zinc-carbonate, zinc-sulphuret and mixed ores
and for the separation in general of fixed and volatile metals in blast-furnaces,
substantially as described and for the purpose set forth.
L. DUVINAGE,
Agent for Applicant, 8, Rue des Princes, Brussels, Belgium.