Improvements in and connected with Gas Furnaces for Treating Lead Ores.
Year: 1899

page_text: Date of Application, 6th Jan., 1899-Accepted, 25th Feb., 1899
COMPLETE SPECIFICATION.
Improvements in and connected with Gas Furnaces for Treating Lead
Ores.
I, LUIS CORREA, of Felguera, Spain, Gentleman, do hereby declare the nature
of this invention and in what manner the same is to be performed, to be particu-
larly described and ascertained in and by the following statement:—
This invention relates to improvements in and connected with gas furnaces for
treating lead ores and has for its objects, firstly, to provide an improved process
furnace
for treating lead ores economically, and secondly, the construction of a gas
specially adapted for use in connection with the said process, wherein the lost
heat is recovered.
Hitherto the gas producer employed had to be specially designed to meet the
requirements of the different and numerous well known types of furnaces, which
necessity in my invention is entirely dispensed with.
According to my improved process the lead ores naturally oxidized or roasted
previously, are mixed with the necessary proportion of flux, consisting of car-
bonate of lime and oxide of iron.
In some cases carbon may be used for reducing the metallic oxide.
The lead ores mixed with the flux forms the smelting mixture. Before heating
the furnace it is charged with the said mixture, a quantity of charcoal sufficient
to effect the reduction of the metallic oxide being at the same time introduced.
The temperature is then raised in the furnace as much as possible, by closing
all the openings and by means of the valves the passage of the gases and hot air
may be regulated at will. The mixture in the furnace then smelts rapidly and
forms a bath having the following reactions.
The flux looses its carbonic acid and is converted into lime. The lime and
oxide of iron combines with the gangue of oxide of lead and forms a very fusible
silicate and bi-silicate.
The latter decompose the sulphate in the said bath and produce. sulphurous
acid, silicate of iron, of lime and of metallic lead.
The oxide of iron liberated replaces that of the lead in its combinations, leaving
the same isolated.
The charcoal mixed with the bath is burned by the oxygen of the metallic
oxide.
The oxide of lead being very reducible, when coming into contact with incan-
descent carbon and changing into carbonic oxide, gives off its oxygen, which
reduces the oxide in the bath and converts itself into carbonic acid, setting free
the metallic lead.
The intimate mixing of the smelting material and the extent of time during
which it is in the furnace causes the said reactions to take place gently so that the
whole of the lead separates itself and the scum which forms is quite fluid and
practically free from lead.
And in order that my invention may be more fully understood I have caused

page_text: to be appended hereunto one sheet of drawings marked with letters of reference
indicating like parts in the various figures.
Figs. 1, 2 & 3 being sectional plans and Figs. 4, 5 & 6 vertical sections of my
improved furnace. Figs. 1, 2 & 3 at lines gh, ij, kl of Figs. 6, 5 & 4, and
Figs. 4, 5 & 6 at lines ab, e-f, c-d of Figs. 1, 2 & 3 respectively.
In Fig. 1 the chamber is shown which receives the fumes from the smelting
chamber through the passages A formed in the circular furnace wall. The fume
collector B reaches to the centre of the said chamber and the fumes passing through
the general condensation gallery escape through the chimney.
In the collector B is a valve C and a damper D (Figs. 2 & 3) for regulating the
draught in the chimney and to permit of entering the said chamber when necessary.
The roof in the said chamber is formed hemispherically.
Fig. 2 shows the recovering chamber with which communicate the channels E
through which descends the air already heated in the upper part of the furnace.
The cold air euters under the dome F through the grid G formed at its upper end.
The air in the recovering chamber is heated to a high temperature and escapes
through the conduit H which reaches to the centre of the said chamber and at its
cuter end joins a vertical tube furnished with a valve I. From thie tube the air
passes through two openings into the semi-circular tube J and into the burner K
where it causes the combustion of the gas which arrives from the gas producer
through suitable tubes connected therewith.
The roof of the said chamber is also formed hemispherically.
Fig. 3 shows the smelting chamber.
In the circular wall which encloses the said chamber are formed three ports,
the lateral two ports serving for the introduction of the charge and the one facing,
for the outlet of the scum produced.
In the said wall are also formed vertical channels A through which the fumes
descend into the condensing chamber.
The top of the sole O in the smelting chamber is covered with a mixture of clay,
lime and powdered coke intimately mixed. The said sole rests upon the roof of
the recovering chamber and is slightly inclined towards the centre and from there
to a passage P formed through the whole thickness of the sole, Fig. 3, which by
means of a tube is brought into communication with another passage arranged
externally, through which the lead flows continuously, and from which it is tapped
into the moulds,
The roof of the smelting chamber is also formed hemispherically and has in
its centre a large hole leading to the burner. Over the said roof is fixed a hood
of iron F having at its top the grid G for the admission of atmospheric air. The
gas from the gas producer enters through the channel R, Figs. 2 & 5, a vertical
tube having a valve S through which it ascends into the semi-circular tube T,
from whence it enters the burner K through two holes. The channel R com-
municates also with the chimney which has a valve U, Fig. 3.
When it is desired to prevent the gas passing into the furnace it is diverted into
the chimney by turning the said valve accordingly.
The furnace is worked as follows;
-
The valve of the vertical tube I is opened, atmospheric air is allowed to enter
the hood through the grid G, the air then begins to be heated, and descends
through the vertical channel E into the recovering chamber, Fig. 2, and through
the channel H passes into the vertical tube having the valve I, then into the semi-
circular tube and finally into the burner K in two distinct currents.
The gas produced takes a distinct course. It passes through the channel R to
the vertical tube having the valve S through which it ascends into the semi-
circular pipe T from whence it enters the burner K through two holes arranged
separate from the air holes, where it mixes with the air and causes combustion to
take place below the roof of the smelting chamber.
The flames spreading continuously, the part of the furnace which requires
intense heat is strongly heated.

page_text: The fumes resulting from the combustion of the gas and treatment of the ores
descend through the vertical conduit H into the condensing chamber from whence
they pass through the collector and general gallery into the chimney.
By means of the valves I, S, the temperature in the smelting chamber can be
increased or lowered in a moment, by admitting a larger or smaller volume of air
and gas and by means of the valves C & D, the draught in the chimney may be
diminished or increased and the gas from the producer directed into the chimney
instead of into the furnace.
The smelting takes place as follows:-
The furnace having been suitably heated, is charged by the two side openings
with the ores, flux and the quantity of charcoal necessary for reduction of the
metallic oxide.
The ores smelted in this manner forms a bath and the reactions herein before
indicated in the description of the process, takes place.
As the oxide of lead is produced it runs down the passage P and from there
through a connection to the exterior tube Q and from the latter it is abstracted
into the moulds. The scum produced by the treatment of the ores forms a bath
which covers the whole surface of the sole and when all the lead has been run off,
is allowed to run out through an opening at the front of the furnace furnished
with a removable channel arranged outside the same, which finishes the operation.
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--
1st. The employment of a furnace having a sole for the reduction of lead ores,
all substantially as set forth.
2nd. In a gas furnace such as specified in the preceding claim and wherein the
heat is recovered, an air heating chamber arranged between the smelting chamber
and the chamber for the burned gases, which chamber receives the air previously
heated in a special chamber above the roof of the smelting chamber which covers
the inlets of the combustible gas and the hot air in the smelting chamber, all
substantially as set forth.
3rd. In the furnace specified in Claim 1, the employment of a gas burner in
the roof of the furnace, all substantially as set forth.
Dated this 5th day of January 1900
F. BOSSHARDT & Co.,
4, Corporation Street, Manchester, Agents to Applicant.