Improvements in Furnace and Apparatus for Working Gold, Silver, Copper, and other Ores.
Year: 1894

page_text: Date of Application, 28th Mar., 1894-Accepted, 9th June, 1894
COMPLETE SPECIFICATION.
Improvements in Furnace and Apparatus for Working Gold, Silver,
Copper, and other Ores.
I, CHARLES ARTHUR ALLISON, of 52 Chancery Lane, London, in the County
of Middlesex, Patent Agent, do hereby declare the nature of this invention, (which
has been communicated to me from abroad by Jacob Jones Storer, of Helena,
County of Lewis and Clarke, State of Montana, United States of America, Patent
Solicitor, Frank Martin, of Helena, County of Lewis and Clarke, State of
Montana, United States of America, Engineer and Mining Superintendent, and
George Oscar Eaton, of Helena, County of Lewis and Clarke, State of Montana,
United States of America, United States Surveyor General for the State of
Montana,) and in what manner the same is to be performed, to be particularly
described and ascertained in and by the following statement:-
This invention is designed as an improvement on furnaces and apparatus for the
reduction of gold. silver, copper and other ores, into which the raw ore to be
operated upon is introduced on an air current in a finely pulverized condition, and
in its several forms or modifications is applicable to the reduction of such ores by
wet or dry processes without permitting the escape of metallic fumes or deleterious
gases.
This invention consists of a hollow, upright shaft of masonry in the form of a
truncated cone, uniting at its base with a horizontal flue, the bottom of which may
be formed by a water trough, or tank, in which is a horizontal, revoluble, screw
conveyor; or in one of its modifications, by a flat or concave dry-hearth devoid of
a screw-conveyor; and in another of its modifications by a melting pot or crucible
with certain auxiliaries.
The invention further consists of combinations of two or more devices for the
prevention of the escape into the air of metallic fumes, ore dust and deleterious
gases, all of which will be herein-after set forth.
Reference is to be had to the accompanying drawings forming part of the
Specification, in which similar letters of reference indicate corresponding parts.
Figure 1 represents a vertical, longitudinal section of the improved furnace as
adapted to the working of various ores by the wet process.
Figure 2 represents a sectional plan of fire places and gas expansion chamber on
lines X, X, Figure 1.
Figure 3 represents a longitudinal, sectional elevation of another form of the
furnace adapted to the working of various ores by what is known as the dry
process.
Figure 4 represents a vertical section on line y, y, Figure 3.
Figure 5 represents a longitudinal, sectional elevation, showing another form of
the receiving hearth, or reservoir, adapted to the smelting of matting of certain
ores, and shows also, as is shown in part, in Figures 1 and 3, a sectional elevation
of combined devices for arresting metallic fumes and gases.
Figure 6 represents a horizontal section on line Z, Z, Figure 5.
In the drawings, A represents the water tank, constructed preferably of brick,
and internally cemented. Connected with this at one end, and rising vertically
therefrom, is the furnace shaft A' of cylindrical cross section, and expanding from
above downward. This shaft, which extends from the roofs of the fire place
downward, consists of an exterior wall A2, and an anterior fire brick wall A³,
between which is an annular air space A which is preferably closed at both top
and bottom. About the top of this shaft, and constructed so as to internally

page_text: communicate with it, are fire places B, directly opposite each other, so constructed
with sloping grates B₁ and sloping roofs 13 that the heat therefrom shall be
radiated through their throats, as indicated by arrows, directly into the vertical
axis of the shaft. Openings B³, that may be closed by stoppers or doors B' are
for feeding fuel into these fire places. In the fire place roofs are fixed stove
pipes B, provided with dampers B, which pipes serve to carry off the smoke and
gases when the fires are first lighted.
A cylindrical pipe or conductor C, preferably of brick, is set vertically above
and between the fire places, with its vertical axis corresponding with that of the
shaft A. This construction of shaft and fire places is the same in all forms or
modifications of this furnace.
The tank, or water bearth, A, as will be seen, is completely covered, partly by
the furnace shaft A' and partly by an arch D, extending horizontally from the
furnace shaft A', and partly by a chamber or flue D' containing dust deflecting
walls D. In the end wall of the chamber D₁ openings D³ communicate with a
spray wheel chamber E, in which is an exhaust fan E' which also serves as a spray
wheel for comminuting into fine spray, water that is designed to be introduced
upon it during the operation of the furnace, through a pipe E. The exit E³, from
the spray wheel chamber, communicates with the interior of the smoke stack F,
which latter is filled for some distance, from the bottom upwards, with lattice or
cob work F¹, constructed preferably of strips of wood F², laid in horizontal planes
with alternating spaces F. The combined areas of these openings or spaces being
amply sufficient for the easy escape of all the furnace gases that are not wetted
down by the spray wheel.
In the bottom of the smoke stack is shown a pipe F, for conducting away the
water that may be thrown into said stack and cob work. A screw conveyor G, is
shown in the bottom of tank A, the purpose of which is to thoroughly agitate in
the water the ore that is introduced through the furnace shaft, and remove it into
one or more settling pits, one of which is shown at G'.
In operating this furnace, it is designed to keep the tank A partly filled with
water, the water line being indicated by dotted line G².
This furnace is designed for the heating and roasting of ores, especially those to
be worked for the gold and silver they may contain; and preparatory to being
introduced into the furnace they are to be finely pulverized. If an ore contains
sufficient sulphur to maintain the desired temperature in the furnace, by its com-
bustion as it falls down the shaft, the heat and flame from the fire places will not
have to be supplemented by other fuel; but if the ore does not contain sufficient
sulphur for such purpose, pulverized coal in proper quantity is mixed and introduced
with it.
In operating this furnace, fires are built in the fire places, and the dampers in the
smoke pipes are kept open until the fuel is well ignited; then the said dampers are
closed and the spray wheel is made to revolve, thus causing the flames from the
fire places to be drawn closely over the fire bridges down the interior of the
shaft A. When the interior of said shaft has become sufficiently heated, the finely
pulverized ore is introduced into the head of the shaft, by a current of air
down the conductor C. On issuing from the mouth of this conductor, the descending
column of air-borne ore, or mingled ore and coal, is instantly exposed on all sides
to the heat radiated from the grate fires, and the sloping walls of the fire places
through their wide open throats, and is thereby at that point superficially ignited.
In some cases, in the class of furnaces above referred to, the flame from the fire
places being drawn closely down over the fire bridges, have little or no effect on
the falling ore, until the latter has passed below the said fire bridges. But this
improved furnace essentially differs from others in the respect that in others there
is no direct radiation of heat upon the falling ore from the fire surfaces and
interior walls of the fire places; the heated air and gases alone conveying heat into
the shaft, so that none of the ore could ignite until it had reached and passed the
fire bridges. Nor was there space there afforded for the necessary lateral

page_text: expansion of the gases generated by combustion of the ores; bence, when formed,
these gases were violently forced downward in the line of least resistance, carrying
with them the ore, a considerable portion of which would reach the water in the
tank in an unsufficiently heated, and but partially de-sulphurized condition, unless
the shaft were very high, or the ore but slowly fed into it.
In this furnace, however, it will be seen that at the lower end of the conductor C,
and between it and the fire bridge walls, a gas expansion chamber C¹ is formed by
the wide open throats of the surrounding fire places.
It is found that the hot air and gases generated in these fire places, and issuing
therefrom, form what may be called an elastic cushion, that yields to the lateral
expansion of the gases generated by the falling ore, sufficiently to prevent its too
rapid downward movement, so that time is there afforded to the whole mass of the
ore for ignition at that point, and, consequently, for subsequent complete combus-
tion in its passage down the shaft. Thus it is obvious that the gas expansion
chamber is necessary for the proper working of furnaces of this class, and that it
also very materially increases their capacity.
Falling down the shaft A', the heavier particles of the ore fall into the water,
and settle to the bottom of the tank. The lighter particles, drawn forward by the
action of the draft and spray wheel, pass beneath the arch D, which causes them
to converge, so that they are brought in contact with the sloping lip D* thereof,
whereby they are deflected downward, so that the bulk of them are thrown into
the water of the tark while still at a red heat; it being a very desirable matter
in working some classes of ores, that all the particles, if possible, should enter the
water at a high temperature.
-
The most minute air-floated particles of ore, together with the gaseous products
of combustion, pass along the horizontal chamber or flue,-where some of the
particles of ore are deflected downward into the water by the deflecting walls D³,
and out through the opening or openings in the end of said chamber or flue, into
the spray wheel chamber, where they are wetted down and thrown forward with
the spray, into and upon the cob or lattice work in the base of the smoke stack.
This cob or lattice work presents a very extended surface, which, when wetted by
the spray, serves, in combination with it, to thoroughly condense and wet down all
gases, metallic fumes and ore dust escaping from the furnace, which might
otherwise pass up and out of the smoke stack; and these gases and dust being
thus wetted down and held in solution or suspension in water, are conducted off
and out of the smoke stack to a suitable place of deposit (not shown) by a pipe F',
to be treated or disposed of as may be desired.
In Figure 3 is shown another form of the furnace, in which the vertical shaft A¹,
its fire places B, gas expansion chamber C, conducting pipe C, spray wheel E, and
the condensing device F in the smoke stack, reinain the same, while the water
tank or hearth A. has substituted for it a dry hearth H, and its auxiliaries.
Directly beneath the shaft A', a receptacle or dry hearth H, is formed by the
inward sloping of the rear wall as shown at H', and by an opposite bridge wall H³,
while the horizontal flue H³, covered by a roof H', extends forward to the spray
wheel chamber E.
The ore to be treated in this form of furnace is, after being finely pulverized,
fed down this conductor C, into the heated shaft A', being introduced into said
con luctor on an air current from a fan blower, or through a sieve (not shown).
If it be an ore containing sufficient sulphur for maintaining by its combustion a
proper temperature, it will, if sufficient air be admitted with it, become thoroughly
desulphurized by the combined action of the heat and oxygen, before reaching the
dry hearth, or reservoir H, which is constructed beneath the shaft A', as shown.
If it be an oxide ore, or one containing but a small amount of sulphur, pulverized
coal may be introduced with it, so that, by its combustion, the proper temperature
may be maintained in the shaft A'; the desired temperature being between a dull
red and a white heat, according to the character of the ore to be treated.
If salt be introduced down the heated shaft finely pulverized and mixed with

page_text: the ore, the latter will be brought into the best condition for subsequent chlorina-
tion, amalgamation, or leaching with suitable chemical solutions, for the purpose of
obtaining the precious metals it may contain. The ore, as it accumulates in the
dry hearth, or furnace, (of the form shown in Figures 3 and 4) may be drawn out
through the door H³ Just beyond the outer wall of the shaft A', and in the roof
of the horizontal flue H³, is shown a hood plate I, so arranged as to slide up or
down in suitable guides (not shown), to diminish or increase the area of the throat
of said reservoir, as may be desired, as shown by dotted lines.
By fixing this hood as shown by full lines, a narrow opening or throat is left
between its lower edge and the bridge wall H, so that, if desired, the hot air and
gases from the shaft A', being thereby retarded and retained in the reservoir, may
operate to bring the mass of ore therein deposited to a higher temperature.
The gases generated by the ore constituents, and of the introduced fuel if there
be any, together with some of the finest ore dust, will pass out through the furnace
or dry hearth into the smoke flue H³, where they will be partially wetted down
and condensed by water sprays issuing from the water pipes He, as indicated in
Figure 3, and fall upon the sloping bottom of said flue, and flow off through a.
pipe H, into a suitable reservoir (not shown) for further treatment.
The residue of the dust, and gases will pass on through an opening or openings D³
in the end wall of the flue H³, into the spray wheel chamber E, where it is wetted
down by the action of the draft and spray wheel E', which, when in operation,
causes the downward draft of the hot air and flames from the fire places at the top
of the shaft A' and of the ore introduced into said shaft.
Water, or water with the proper chemical re-agents in suspension or solution, in
sufficient quantity for the production of the requisite amount of spray, is introduced
upon the spray wheel through the pipe E³, and this spray with the absorbed gases
and dust, is thrown by the wheel E¹, upon and through the cob or lattice work F¹,
which fills the base of the smoke stack F, and thence drains off, through a pipe F4,
into a suitable reservoir, (not shown).
The great value of this cob or lattice condensing lies in the extensive condensing
and arresting surface which it presents to the escaping steam, water-spray, gases
and dust.
In Figure 5 is shown another form of furnace covered by this invention. In this
case, the hearth designed for the reception of the ore introduced down the shaft A¹
is made concave or bowl-shaped, as shown at K, Figures 5 and 6, for the purpose
of holding the molten metal when extracted from the ore. This form of hearth or
furnace is adapted for smelting or matting; and for this purpose, it is made of
greater area, that it may hold a large amount of metal, and its side walls K'are
outwardly curved, as shown in Figure 6, so that it is, in effect, a reverberatory
furnace; and, that it and the ore falling into it may be heated to any desirable
temperature for the fusion of the ore and the separation of the metal from the
gangue, an auxiliary fire place L, is constructed in the rear, to furnish additional
beat, and preferably pulverized fuel may be introduced by means of a fan or
pulverizer, as indicated at M, through an opening or tuyere MI' in the rear wall of
the furnace, over the fire of this auxiliary fire place, so that it will there ignite and
burn over the mass of ore in the furnace bottom. But the fire place L may be
made of sufficient dimensions to furnish, by itself, the required heat to the furnace.
In order to prepare this smelting hearth or furnace for the reception of the ore
into it from above, a fire is made in the auxiliary fire place L, and urged until it is
sufficiently hot to set fire to the pulverized fuel that may be introduced over it ;
then the hood plate I, which, in this instance, may be made to serve as a damper,
is lowered, as indicated by dotted lines, Figure 5, to close the throat of the furnace;
then the pulverized coal, mingled with air sufficient for its combustion, is introduced
over the throat of the auxiliary fire place into the furnace by means of the fan or
pulverizer above referred to, and is there consumed with intense heat, while a
portion of the flame and gaseous products of combustion ascend the shaft A', and
escape through the conductor C, and the fire place pipes B³.

page_text: Thus, in a very short time the temperature of this furnace can be raised
throughout to the ore melting point, and the shaft A' be heated to a high degree.
When the furnace is thus sufficiently heated, the hood or damper I, is raised so
as to open the furnace throat, the draft and spray wheel is set in motion, and the
introduction of the ore through the conducting pipe C is begun, while the air-borne,
pulverized fuel is still fed horizontally into the furnace by the fan or pulverizer.
The fine particles of air-borne ore falling down the heated shaft, and becoming
thereby desulphurized and oxidized, pass through the horizontal sheet of the
carbonizing and deoxidizing flame and gases of the pulverized fuel, entering through
the tuyere M', which instantly reduce the bulk of the oxides to metals that fall
with the gangue into the bottom of the hearth or furnace, where they both
accumulate in a molten condition.
Because of its less specific gravity the molten gangue or slag floats on the top of
the molten metal, and what unreduced oxides the slag may contain are quickly
reduced by the deoxidizing flame in the furnace, and then sink through the liquid
slag into the metal bath below.
It is found that when the ore is reduced to sufficient fineness, all the sulphur is
eliminated from it in its brief passage of one or two seconds down the heated
shaft A', and that hence no sulphides reach the hearth to retard the reduction of
the metals.
When it is desired to tap out the melted slag and metal, the feeding in of the
ore may be suspended, and when this operation is over, the feeding of the ore may
be resumed as before.
What re-agents or fluxes are necessary in working the ores may be laid upon the
hearth in the form of grouting, may be spread upon the surface of the charge in
the furnace through suitable doors (not shown), may be introduced down the shaft
with the raw ore, or may be introduced with the pulverized fuel.
The exit or smoke flue H³, leading to the spray wheel, has in it several
perforated walls N, constructed of brick or tile, or other acid-resisting material,
laid with wide spaces through them for the passage of the furnace gases; and
these walls being constantly wetted and cooled by water from the pipes N', serve
to cool and condense the greater portion of the escaping gases, smoke and metallic
fumes, and to arrest most of the ore dust from the volume passing on to the spray
wheel, where the residue is wetted down.
I am aware that water sprays, perforated walls kept wet with water, and jets of
steam, have long been used for arresting and condensing the gases, dust and
metallic fumes in the flues of ore roasting furnaces, and therefore I do not claim
these broadly. But so far as known, the effect of these separately or in
combination is only partial, for the resulting steam or mist escaping from the
furnace flues is found in all cases to contain a very appreciable amount of metallic
dust. In order to prevent this loss, and to prevent the injurious effects upon the
surrounding vegetation from this dust deposit, I have combined with these usual
condensing devices, an exhaust fan and spray wheel E', upon which cold water
alone, or water holding chemical re-agents, such as chloride of lime, quicklime,
carbonate of soda, chloride of sodium, chloride of potassium, etc., is introduced, to
be converted into a fine spray and be thrown forward upon and into a pile of cob
or lattice work F1, which may partly or completely fill the smoke stack.
By the arrangement of a series of sprays or jets of water constantly dripping
over the perforated walls N, many of the particles of matter are arrested and
carried down by the dripping water before it arrives at the spray and draft wheel,
and thus there is much less work for it to do, and hence less power is required to
drive the wheel, as it has not to carry so much of the material carried by the gases.
This effect is increased by the use of the perforated walls, although, in some cases,
the simple spray may be found sufficient.
This draft and spray wheel may be made of any desired dimensions, and may be
run at any required speed, and any required supply of water or chemical solution
may be introduced upon said wheel, while the pile of cob or lattice work may

page_text: easily be of such dimensions as to present an absolutely effective condensing
surface. Hence it is obvious that this improved, combination, condensing device
must effect the desired results.
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 1
claim is :-
1. In a furnace constructed substantially as shown, a gas expansion chamber
formed in the upper part of the ore heating and desulphurizing shaft, and fire
places surrounding the same, with wide open throats arranged to allow the heat
therefrom to act by radiation on the descending ore, substantially as described.
2. In a furnace constructed substantially as and for the purpose specified,
wherein the raw ore is fed into the top of a heated shaft, the combination with said
shaft, of fire places, having wide open throats, with their tops arranged to radiate
heat directly upon the descending ore, substantially as described.
3. In a furnace constructed substantially as and for the purpose described,
wherein a covered water tank for the reception of the desulphurized and oxidized
ore is set beneath, and arranged to communicate with a vertical shaft, down which,
when heated, the pulverized ore is fed, the combination with said tank and shaft, of a
passage leading from the vertical shaft over a portion of the tank and terminating
in a deflecting lip, to deflect the fine, air-floated particles of ore into the water,
substantially as described.
4. An ore roasting, smelting or matting furnace constructed substantially as
herein shown and described, with an upright ore-feeding and desulphurizing shaft,
expanding from above downward, having about its top opposite fire places with a
gas-expansion chamber between them, each fire place being constructed so as to
deflect and radiate the heat therefrom directly into said combustion chamber, an
ore-receiving dry hearth or furnace at the bottom of said shaft, and, at the top,
communicating with it; and a flue leading from the exit or throat of said dry
hearth or furnace to a smoke stack; as and for the purposes set forth.
5. An ore roasting, smelting or matting furnace constructed substantially as
herein shown and described, with an upright ore feeding and desulphurizing shaft,
having opposite a gas expansion chamber between them, fire places about its top, a
reverberatory dry hearth or furnace at the bottom of said shaft and at its top
connecting with it; an auxiliary fire place connected with said reverberatory
furnace, and a flue extending from the exit of said furnace for the escape of the
gases therefrom, as set forth.
6. An ore roasting, smelting or matting furnace, constructed substantially as
herein shown and described, with an upright ore feeding and roasting shaft having
fire places about its top; a reverberatory dry hearth or furnace at the bottom of
said shaft and at its top communicating with it; an auxiliary fire place connected
with said reverberatery furnace, the rear wall of said reverberatory furnace being
provided with an opening or tuyere for the introduction of air-borne, pulverized
fuel, substantially as set forth.
7. The combination with the upright shaft, the hearth or furnace at the bottom
thereof, and with the flue leading from the exit of said hearth or furnace, of an
adjustable damper, substantially as herein shown and described; said damper being
designed for adjusting or closing the furnace throat or exit, as set forth.
8. An ore roasting, smelting or matting furnace constructed substantially as
herein shown and described, with a vertical, cylindrical chaft, expanding from above
downward, and forming a free passage, being interiorly devoid of shelves, inclined
planes, or other ore-arresting devices, terminating in a reverberatory hearth or
furnace, said shaft being designed for heating, and conducting hot into its terminal
receptacle pulverized ores which may be fed into its top, as set forth.
9. The combination with an ore roasting or smelting furnace and with its exit
flue, of spraying pipes arranged in said flue, a spray wheel chamber communicating
with and intermediate between the cxit end of said flue and a smoke stack; a spray

page_text: wheel in said chamber, and a device for introducing water upon the wheel, all
arranged and operating substantially as herein shown and described.
10. The combination with an ore roasting or smelting furnace, and with its exit
flue, of spraying pipes arranged in said flue; one or more perforated division walls
fixed in said flue to receive the spray from said pipes; a spray wheel chamber
communicating with and intermediate between the exit end of said flue and a smoke
stack; a draft and spray wheel in said chamber; and a pipe for spraying said
wheel; all arranged and operating substantially as herein shown and described.
11. The combination with an ore roasting or smelting furnace and with its exit
flue, of spraying pipes arranged in said flue; one or more perforated division walls
fixed in said flue to receive the spray from said pipes; a spray wheel chamber
communicating with the exit enȧ of said flue and with a smoke stack; a spray
wheel in said chamber, and a gas and dust condenser and arrester, constructed of
lattice or cob work, fixed in the base of the smoke stack; all arranged and operating
substantially as herein shown and described
12. As a means for arresting and condensing the dust, gases and metallic fumes,
escaping from an ore roasting or smelting furnace, the combination with the furnace
flue, of a spray wheel chamber; a spray wheel set in said chamber and arranged
so as to revolve; a water supply for said spray wheel; and an inclosed surface
condenser, composed of cob or lattice work, having interstices both in vertical
and horizontal planes; all arranged and operating substantially as set forth.
Dated this 27th day of March 1894.
ALLISON BROS.,
Agents for the Applicant.