Roast′ing-fur′nace.
（
Metallurgy.) A furnace in which ore is heated to drive off the sulphur and other volatile particles.
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Roasting-furnaces. |
A is
Parke's roasting-oven for copper ore, in which the ore is stirred by machinery.
The hearth is in two stories, each of which has its own rotary stirrer attached to the central shaft and operated by gearing in the vault below.
The hot gases from the furnace pass over the two chambers in turn, and thence to the chimney.
The hearths are about 12 feet in diameter.
On the other side of the hearth appear the openings at which the working tools are introduced.
These are closed by iron doors.
The charge is introduced at an opening in the roof of the upper chamber.
Each hearth has a charge of 4 tons.
The material is raked from one floor to the other, and eventually falls into a vault beneath.
B is a shaft-furnace for roasting iron by means of gases from hydrocarbons.
The stack is hooped with iron, and has a central cavity of a truncated cone shape.
The cast-iron hearth has three slopes which incline to the discharge-holes, which have doors in which are air-holes.
Above the openings leading to the doors is a carrying piece projecting into the shaft.
The gases are led in at a tube shown on the left, from which they reach the interior by a number of tuyeres at various hights in the shaft, whence they issue, and, coming in contact with atmospheric air, are burned.
The entrance is regulatable by dampers at the various tuyeres of the respective series.
C is a reverberatory furnace for roasting arsenical ores, in which the fumes are conducted from the furnace through a long flue, in which they are condensed in cooling.
By such means either valuable materials are saved, or the fumes are suppressed, so as to avoid contaminating the surrounding atmosphere.
See arsenic-furnace. Along the condenser are doors for extraction of the deposited material.
See Plattner's “Metallurgischen Rostprozesse,”
Freiburg, 1836.
[
1955]
Fig. 4369 is a furnace with a rotating hearth, the contents of which are moved by stationary stirrers.
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Revolving-hearth furnace. |
Another form of roasting-furnace has inclined cylinders, through which the ores pass, being heated by the furnace.
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Reverberatory furnace. |
In Rivot's furnace (
Fig. 4370), the
gold or
silver ores are mixed with oxide of iron, and then submitted during the roasting process to the action of superheated steam.
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Whelpley and Storer's shaft-furnace. |
In Whelpley and
Storer's furnace, patented January 12, 1864, the ore, in a finely comminuted state, is forced by a fan-blower
a through the tube
b into the descending shaft
c of the apparatus; this has furnaces
d d′ on each side, provided with chimneys
e e, to the action of which the ore falling from the tube
b is exposed.
The bottom of the horizontal shaft
f is covered with water, into which the heavier particles of ore fall; the lighter portions are arrested in the chamber
g by means of a spray of water injected thereinto.
A rapidly revolving fan
h in this chamber withdraws the products of combustion through the up-cast shaft
i.
Stetefeldt's furnace for roasting silver ores is of the class known as a
shaft-furnace, in which the powdered ore is calcined while falling through the flame rising from a fire.
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Stetefeldt roasting-furnace. |
The ore, having been crushed by the rock-breaker, is then mixed with salt and pulverized by the stamp battery.
From this the pulp is carried by a conveyor to the feeder
a, which consists of a hopper, whose bottom is provided with a coarse wire screen, shaken by means of eccentrics, and a hollow cast-iron base, on which the hopper stands, and through which a current of cool water is caused to circulate.
The base has a grate covered by a perforated
sheet-iron screen.
A number of thin iron blades are arranged across the hopper, nearly touching the wire sieve, and keeping the pulp in place.
The reciprocations of the wire screen cause its meshes to cut through the pulp, which falls into the shaft
b in a continuous shower.
c is one of two flues of a gas-generator, which enter the shaft on each side.
The shaft
d is provided with a light cover and a slide
e, on which charcoal is burned.
The carbonic oxide produced by this is mingled with air introduced through the flue
f, and passes in a state of ignition through the shaft
g into
h, where it heats the shower of falling pulp, which is thus desulphurized and dechloridized, and falls upon the inclined bottom of the shaft, whence it is withdrawn through the door
i. The fine particles, freed from sulphur and chloridized, which pass through the shaft
h, are deposited in the flue
k and dustchambers
l l, and withdrawn at intervals.
See page 1571.
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Aiken's roasting-furnace. |
In
Aiken's furnace (
Fig. 4373), the stamped ore fed through the aperture
a is conveyed by the screw
b into the conductor
c, and drops into the roasting-chamber
d: this has an inclined arched top
e, and is heated by two furnaces
f f, which open directly into the chamber; the doors
g g, pivoted, and having cranks
h h by which they may be placed in horizontal or vertical position, serve to discharge the roasted pulp; the waste gases after passing through the ascending and descending shafts
i k and flue
l, serve to dry the ore previous to stamping.
