IMPROVEMENTS IN FURNACES FOR THE TREATMENT OF ZINC ORES
Year: 1872

page_text: LETTERS PATENT to John Henry Johnson, of 47, Lincoln's Inn Fields,
in the County of Middlesex, Gentleman, for the Invention of
"IMPROVEMENTS IN FURNACES FOR THE TREATMENT OF ZINC ORES."-
A communication from abroad by La Société Metallurgique pour
l'Exploitation des Procódós Pongard of Paris France
PROVISIONAL SPECIFICATION left by the said John Henry Johnson
at the Office of the Commissioners of Patents, with his Petition,
on the 10th February 1872.
I, JOHN HENRY JOHNSON, of 47, Lincoln's Inn Fields, in the County
of Middlesex, Gentleman, do hereby declare the nature of the said
Invention for "IMPROVEMENTS IN FURNACES FOR THE TREATMENT OF ZINC
ORES," a communication to me from abroad by La Société Mettalurgique
pour l'Exploitation des Procédés Ponsard, of Paris, France, to be as
follows:-
This Invention relates to an improved construction and arrangement

page_text: increasing the durability of the crucibles employed, the faciliating the
charging and discharging of the said crucibles or horizontal retorts as
the case may be, the affording means for readily removing and replacing
a broken crucible whilst the furnace is in continuous operation, and the
heating of the said furnace by the application of the peculiar mode of
and apparatus for heating by gas in conjunction with a regenerator
described in the Specification of Letters Patent granted to me on behalf
of M. Ponsard, the 4th day of June One thousand eight hundred and
According to this Invention the furnace is constructed of a rectangular
form, and is in communication at one end with a gas regenerator, and at
the opposite end with a regenerator constructed in accordance with the
Specification of the Patent herein-before referred to. The central
portion of the furnace is occupied by several series of vertical crucibles
which rest at their lower ends upon the floor of the furnace, and are
supported at their upper ends by passing through openings in slabs of
fire-clay forming a part of the roof of the furnace. The mouth of each
crucible is provided with a lid or cover, and projects slightly above the
top of the furnace outside, and is charged by a spade or shovel direct
from a metal platform above, upon which the ore to be treated is
collected. When charged the lid of the crucible is closed and the joint
luted. The bottom of each crucible is perforated and communicates
with a moveable extension piece or short tube, which again opens
directly into a descending pipe wherein the vapours of zinc are con-
densed, and from which the metal falls, into wheeled receptacles below.
The moveable extension pieces above referred to are maintained in their
place against the bottom of the crucibles by means of vertical rods
which form collars at their upper ends to receive the lower end of each
extension piece, such rods being maintained in position by passing
through horizontal fixed supporting bars secured to cross beams under
the furnace bottom, the said bars, being provided with screws for holding
the rods in a fixed position therein. By loosening these screws the
extension piece may be readily removed laterally to allow of the
residuum in the crucible being removed, which may be facilitated by
inserting therein from above a poker or bar of iron. These extension
'pieces may be slightly conical tapering from above downwards, but in
some cases they may be replaced by simply prolonging upwards the
condensing tube.

page_text: Above the heat regenerator at one end of the furnace there is situate
an oven for heating the crucibles, the said oven containing a number of
vertical muffles or pots closed by lids or covers, in which the crucibles
to be heated are placed. The oven moreover is subdivided into a
number of separate chambers by double or hollow partition walls having
cross bricks built within the space to take up the heat more readily from
the flames which circulate through the said walls after issuing from the
furnace and before traversing the regenerator. Just before entering the
walls of the heating oven the flames pass under a baffling arch for the
purpose of depositing any dust that may be carried along with the
draught, the said dust being collected and removed through a side door
for the purpose.
The air which has been heated by passing through the
regenerator enters the furnace by an air flue at the end furthest from
the regenerator, and mingles with the gas from the gas generator, which
also enters this end of the furnace by a special flue or passage for that
purpose.
In some cases it is proposed to substitute for the vertical crucibles
horizontal fire-clay retorts provided with vertical feed pipes passing up
through the roof of the furnace and fitted with lids or covers.
The ores
to be treated are shovelled into these vertical pipes, and fall direct into
the horizontal retorts, the ends of which are removeable. These retorts
rest transversly upon a number of longitudinal parallel supported ribs
or walls of fire-clay, space being left between the several supports for the
free circulation of the flame all round the retorts.
5 SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said John Henry Johnson in the Great Seal Patent
Office on the 10th August 1872.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, JOHN
HENRY JOHNSON, of 47, Lincoln's Inn Fields, in the County of
Middlesex, Gentleman, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Tenth day of February, in the year
of our Lord One thousand eight hundred and seventy-two, in the 35th
year of Her. reign, did, for Herself, Her heirs and successors,..give

page_text: now proceed more particularly to my wi
shall refer to the several Figures on the annexed Sheet of Drawings, the
same letters of reference indicating corresponding parts in all the
corresponding Figures.
Figure 1 of the Drawings represents a vertical longitudinal section
along the line a, b, of the improved zinc furnace with vertical crucibles
or retorts; Fig. 2 is a horizontal section taken along the line c, d, e, f;
Fig. 3 is a transverse vertical section along the line g, h; Fig. 4 is a
longitudinal section along the line i, j, of the second type of furnace
with horizontal retorts; Fig. 5 is a horizontal section along the line k, l;
and Fig. 6 is a transverse section along the line m, n.
'
As will be seen on referring to Figs. 1, 2, and 3 the furnace is of
rectangular form and strengthened by plates disposed all round. At
one end there is erected a gas generator, and at the other a heat re-
generator constructed on the system Ponsard, but which separately
forms no part of the present Invention. The central part of the furnace
is occupied by several series of vertical crucibles or retorts a of fire-
clay, the lower ends of which rest upon the hearth 6 of the furnace,
whilst their upper portions closed by a lid or cover d traverse the roof of
the furnace, and are there maintained by plates c of fire-clay perforated
with holes and disposed in juxtaposition. The tubes a are perforated at
their lower ends, which effect a communication with the conical part e
composed of fire-clay and enclosed in an outer casing fitted with lugs
for the purpose of hooking them on to cross bars of wrought iron
disposed in the hearth b. These conical portions e are terminated by
metal tubes in which the vapours of zinc are condensed, the metal
falling in drops into the receivers g below placed on small carriages. It
is sufficient afterwards to melt the metal in suitable furnaces for the
The
purpose of purifying it and to cast it into plates for commerce.
mode of attachment for maintaining the conical parts e applied to the
bottoms of the vertical crucibles a is very simple. Upon the two sides
of the furnace are disposed slant T iron bars h, which receive the ends
of other and smaller T iron bars i placed transversely between each
series of two ranges of crucibles. To the bars i are rivetted the bent
wrought-iron supports j, having holes therein in which enter small
wrought-iron rods k, which are there fixed by means of screws,
and

page_text: The mode of operation of this furnace is as follows:-The roasted
calamine mixed with the necessary amount of fuel to effect its reduction
is accumulated in heaps or collected in receptacles placed on the upper
part of the furnace. This is charged, by means of shovels into hoppers
placed over the crucibles to be charged, which are then tightly closed by
having their lids luted down so as to prevent all escape of zinc fume.
So soon as the operation is completed and the zinc has ceased to distil
the conical part e is removed and pushed to one side, as is also the tube f
fixed thereto, and the residue is caused to descend into a suitable.
receptacle placed under the crucible which is being discharged. This
receptacle serves to convey the scoriæ away after they have been sorted
in order to extract any pieces which may not have been perfectly
calcined, and which are treated again by mixing them with fresh ore..
It will be seen that the charging and discharging of the crucibles are
effected with the greatest facility without the necessity for employing
men specially for the purpose; the operation is carried on regularly and
in a continuous manner, and the crucibles which are broken during the
operation may be readily replaced..
Figs. 4, 5, and 6 shew a modification of this system of furnace for
the treatment of zinc in which the calamine is charged into large hori-
zontal retorts by means of vertical tubes which are intended to facilitate
the introduction of the ore. The retorts t rest on long supports u of
fire-clay, which are disposed edgewise along the hearth of the furnace,
between which supports the flame is able to circulate; the supports are
also recessed at their lower part to correspond to a transverse passage v,
which admits of the withdrawal of any matter which may accumulate.
on the hearth, as for example by reason of the breaking of a retort.
The retorts carry at their upper part tubes 'x, which extend slightly
above the upper level of the furnace, and are used for the purpose of
introducing the ore disposed on the top of the furnace into the crucibles
as herein-before stated. These tubes are closed by a cover, and supported.
by means of supports of fire-clay, which are perforated with apertures
corresponding to each of the tubes and constitute the roof of the
furnace at those parts. The retorts are closed at both extremities by
stoppers, one of which y serves for the discharging of the retort, whilst
the other receives the metal pipe in which the zinc vapours are con-
densed. This furnace like the one herein-before described is heated by
2

page_text: horizontal or nearly horizontal retorts which are charged by means of
vertical tubes, the several parts in each furnace being arranged sub-
stantially as and for the purpose herein-before described.
In witness whereof, I, the said John Henry Johnson, have to this
.
my Specification set my hand and seal, this Thirtieth day of July
One thousand eight hundred and seventy-two.
J. HENRY JOHNSON. (L.S.)