Improvements in Roasting and Drying Ores and Apparatus therefor.
Year: 1897

page_text: PROVISIONAL SPECIFICATION.
Improvements in Roasting and Drying Ores and Apparatus therefor.
I, GEORGE FREDERICK REDFERN, of the Firm of G. F. Redfern and Co., The
General Patent Office, No. 4, South Street, Finsbury, in the County of London,
Patent Agents, do hereby declare the nature of this invention (a communication to
me by Philip Argall, of Denver, Colorado, United States of America, Mechanical
Engineer) to be as follows:-
This invention relates to the roasting and drying of ores and to a rotatable
furnace therefor, the said furnace being applicable for drying ores preparatory to
crushing the same for the cyanide, chlorination or other process where the ores
must be crushed in the dry state, for roasting dried and pulverized ore, or for the
general roasting or calcination of fine ores or furnace products.
The chief objections to the rotatable furnaces and processes heretofore in use
for roasting ore are, (1) that on account of the great diameter of the furnace, the
flame and gases are not brought into intimate contact with the ore, (2) that the ore
is not thoroughly oxidized because of its insufficient contact or admixture with the
air, (3) that loss of ore is heavy as the draught carries off large quantities of the
fine ore as dust and (4) that the cylinder in such furnaces is always out of balance
while being rotated, which necessitates the employment of great and expensive
power.
The object of my invention is to overcome all these difficulties and to this end
it comprises a novel mode of bringing the flame and gases into contact with the
ore to be roasted or dried and for introducing air into the charge during the opera-
tion, and a novel revoluble furnace for carrying out that process, whereby the ore
to be treated may be rapidly and perfectly oxidized, and the loss of fine ore, or dust,
reduced to a minimum, the said furnace being balanced 80 that but little
motive power is required.
According to my invention I provide a series of cylinders or tubes of relatively
small diameter as compared with their length (preferably made of steel plate for
the sake of lightness) rivetted together at the point of contact and also to a centre
piece and encircled by rings or track bands running on suitable supporting and
driving rollers, the said tubes being lined with fire clay or other non-conducting
material and merging at each end into large tubes also lined with fire clay or the .
like.
At one end of this series of tubes, which for convenience of description I will
hereinafter refer to as the " roaster," is a smoke chamber into which extends a
chute through which the ore is fed into the large tube at the feed end of the
roaster and having a hopper at the upper end.
At the discharge end of the roaster is a furnace advantageously arranged for oil
fuel.
To supply hot air for drying or oxidizing the ore, one or more hollow chambers
which I term rabbles is or are fixed in each tube. Each rabble is preferably made
in one casting, closed at both ends, and formed with two passages into one of
which hot air is introduced by means of a fan or other suitable means through a

page_text: rotating air box and distributing pipe and from the other of which it emerges
through a row of holes, a projecting ledge or flange adjacent to the said holes
aiding in the proper distribution of the ore during aeration and also preventing
the air holes from being clogged by the shifting mass of ore.
The supporting wheels or rollers are mounted upon suitable bearings which in
turn are carried upon base blocks or standards, the inclination of which can be
varied according to the inclination to be given to the roaster, the said rollers being
revolved by means of power transmitted to them through say a drive chain and
sprocket wheels and gearing. A revolving thrust bearing is arranged at the
lower end of the roaster.
The capacity of the furnace may be increased or diminished by changing the
speed of its revolutions, or by changing the angle of its inclination.
It is to be understood that the roaster is always balanced when the tubes are
charged no matter what position the tubes are in so that it requires but little motive
*power to revolve it, thereby causing a considerable economy as compared with a
single cylinder roaster. Also as the diameter of the tubes is small as compared
with their length great differences of temperature can be obtained between the fire
end and the feed end, for instance, the fire end can be kept red hot while the
feed end will remain comparatively cool, the heat being absorbed by the ore and
moisture when the roaster is used for drying ore, whereas, in a single tube roaster,
the flame would rush through and heat the roaster nearly as much at the feed end
as at the fire end thereby occasioning great waste of fuel.
Working results have shewn that a four tube roaster will dry a given quantity
of ore about sixty per cent. less fuel and eighty per cent. less power than a single
tube roaster would consume in drying a similar quantity, the area of the single
tube being equal to the aggregate areas of the four tubes.
The operation of the apparatus in roasting the ore, is as follows:―
As the roaster revolves, the raw ore is fed into the large tube and gradually
passes into the small tubes and thence along them to the discharge end. The
small tubes bring the flame and gases in intimate contact with the ore, while the
hollow rabbles at the same time pass pure, hot air uncontaminated by the pro-
ducts of combustion, directly into and through the entire mass of ore as the
furnace revolves thus oxidizing and completing the roasting in the most rapid and
perfect manner.
When the furnace is to be used for roasting, I prefer to form the discharge end
with a conical hood into which the hot gases from the furnace enter through a
central opening, the roasted ore being discharged through lateral openings located
at intervals around the hood as these openings during the revolution of the roaster
successively come to the bottom.
A band covers all the openings except those near the bottom, the object of the
band being to keep the flame and hot gases from escaping.
In treating ore the apparatus is operated in a similar manner to that before
described, except that the ore to be operated on is generally much coarser than
when being dried and the temperature employed is much lower; here also, the
hot air ejected into the body of the ore as the roaster is revolved rapidly carried off
the moisture and dries the ore more effectually than if it were subjected alone to
the action of the flame and gases of combustion passing over it.
Dated the 15th dox of Dacomba 1807

page_text: Improvements in Roasting and Drying Ores and Apparatus therefor.
I, GEORGE FREDERICK REDFERN, of the Firm of G. F. Redfern and Co., The
General Patent Office, No. 4, South Street, Finsbury, in the County of London,
Patent Agents, do hereby declare the nature of this invention (a communication to
me by Philip Argall, of Denver, Colorado, United States of America, Mechanical
Engineer) and in what manner the same is to be performed, to be particularly
described and ascertained in and by the following statement:-
_
This invention relates to the roasting and drying of ores and to a rotatable fur-
nace therefor, the said furnace being applicable for drying ores preparatory to
crushing the same for the cyanide, chlorination or other process where the ores
must be crushed in the dry state; for roasting dried and pulverized ore; or for
the general roasting or calcination of fine ores or furnace products.
The chief objections to the rotatable furnaces and processes heretofore in use
for roasting ore are, (1) that on account of the great diameter of the furnace, the
flame and gases are not brought into intimate contact with the ore, (2) that the
ore is not thoroughly oxidized because of its insufficient contact or admixture with
the air, (3) that loss of ore is heavy as the draught carries off large quantities of
the fine ore as dust and (4) that the cylinder in such furnaces is always out of
balance while being rotated, which necessitates the employment of great and
expensive power.
The object of my invention is to overcome all these difficulties and to this end
it comprises a novel mode of bringing the flame and gases into contact with the
ore to be roasted or dried and for introducing air into the charge during the
operation, and a novel revoluble furnace for carrying out that process, whereby
the ore to be treated may be rapidly and perfectly oxidized, and the loss of fine
ore, or dust, reduced to a minimum, the said furnace being balanced so that but
little motive power is required.
According to my invention I provide a series or plurality of cylinders or tubes
of relatively small diameter as compared with their length (preferably made of
steel plate for the sake of lightness) rivetted together at the point of contact and
also to a centre piece and encircled by rings or track bands running on suitable
supporting and driving rollers, the said tubes being lined with fire clay or other
non-conducting material and merging at each end into large tubes also lined with
fire clay or the like.
At one end of this series of tubes, which for convenience of description I will
hereinafter refer to as the " roaster," is a smoke chamber into which extends a
chute through which the ore is fed into the large tube at the feed end of the roaster
and having a hopper at the upper end.
At the discharge end of the roaster is a furnace advantageously arranged for oil
fuel.
To supply hot air for drying or oxidizing the ore, one or more hollow chambers
which I term rabbles is or are fixed in each tube. Each rabble is preferably made
in one casting, closed at both ends, and formed with two passages into one of which
hot air is introduced by means of a fan or other suitable means through a rotating
air box and distributing pipe and from the other of which it emerges through a
row of holes, a projecting ledge or flange adjacent to the said holes aiding in the
proper distribution of the ore during aeration and also preventing the air holes
from being clogged by the shifting mass of ore.
The supporting wheels or rollers are mounted upon suitable bearings which in
turn are carried upon base blocks or standards, the inclination of which can be
varied according to the inclination to be given to the roaster, the said rollers

page_text: being revolved by means of power transmitted to them through say a drive chain
and sprocket wheels and gearing. A revolving thrust bearing is arranged at the
lower end of the roaster.
To enable the said invention to be fully understood I will describe the same by
reference to the accompanying drawings in which:-
Figures 1 and 1 represent together a longitudinal section of the entire furnace,
a portion of which is taken on the lines 1-1 of Figures 2 and 3.
Figure 2 is a transverse section on the line 2-2 of Figure 1 showing the parts
beyond the sectional plane in elevation:
Figure 3 is a sectional view on the line 3-3 of Figure 1*:
Figure 4 is a transverse section drawn to an enlarged scale of a portion of one
of the cylinders and its rabble the section being taken on the line 4-4 of Figure 5:
Figure 5 is a side elevation of the rabble, partly in section, the said section being
taken on the line 5-5 of Figure 4:
Figure 6 is a plan view of the rabble, partially broken away:
Figure 7 is a side elevation partly in section and partly broken away illustrating
a modification of the discharge end of the apparatus, and
Figure 8 is an end view partly in section and partly broken away of the parts
shewn in Figure 7.
Similar letters of reference indicate corresponding parts in the several figures.
a¹, a², a³, a are the tubes of the furnace which tubes are firmly rivetted together
at the point of contact and also to the cast-iron centre pieces b, b and c, c¹ are the
encircling cast-iron rings, or track bands which are also securely attached to the
said tubes to form as it were, one tube, or a series of tubes which rotate as one
tube. is the fire-clay lining of the said tubes, which lining may be in the form
of cylinders or rings.
I find in practice, that a suitable length for the tubes is twenty five to thirty
feet for roasting and fifteen to twenty feet for drying ores, with a diameter to
allow from twenty to twenty six inches inside the lining; it is to be understood
however that I do not intend to limit the invention to tubes of these exact dimen-
sions nor to limit myself to the use of four tubes, as it is obvious that the dimen-
sion of the tubes may be varied and that more than this number of tubes may be
used without departing from the nature of my invention.
e indicates the smoke chamber and f the hopper and g the chute through which
the ore is fed into the furnace. is the large tube at the feed end of the furnace,
into which all the tubes a¹, a, a³, a open and which is also lined with fire-clay d.
This tube h is in the nature of a cap or hood which fits over and is secured to the
ends of the series of tubes, and at the same time fills up the interstices between
the said tubes, so that the ore may be properly fed to them.
At the discharge end of the furnace, the tubes are preferably joined into one
large tube similar in construction to the large tube h so that the flame from the
furnace which in the drawing is arranged for oil fuel, may readily pass into the
tubes.
1, 2 are the rabbles for supplying hot air for drying or oxidizing the ore, one or
more of such rabbles being used in each tube, although in the drawing .each
tube is represented as having only one. These rabbles are each preferably made
in one casting, closed at both ends and secured to the inside of its tube by means
of the bolts a central partition Figures 5 and 6 forming two passages 13, 13. The
air is circulated through these rabbles by a fan or other suitable means. The air
passes through the supply pipe m, thence into the rotating air box n and thence
through the distributing pipes n¹, n², n³, n into the passage 13, and having
traversed the full length of the rabble 7, passes at the fire end of the furnace into
the passage and emerges through the holes 1. Over the row of holes /, I have
shown a projecting ledge or flange which not only aids in the proper distribution
of the ore during aeration but also protects the outlet air passages and prevents
them from being clogged by the shifting mass of ore,

page_text: The pipe m revolves in the sleeve m' and rotates, together with the connections
between itself and the rabbles, with the furnace tubes.
0, ol and o², o are two pairs of supporting wheels or rollers the track band c rest-
ing upon the wheels o,
and the track band e' upon the wheels 02, 03. The said
supporting wheels are mounted upon suitable bearings which in turn are mounted
upon suitable base blocks or standards as shown in Figures 1 and 1^.
The furnace is revolved by means of power transmitted to the wheels o¹, o³
through the medium, for instance, of a drive chain the sprocket wheel p, the inter-
meshing cog-wheels 22, 23 and the shaft pt, to which the said wheels o¹, o³ are
rigidly secured.
q is the revolving thrust bearing, mounted upon suitable bearings in the block q¹
which is securely bolted to the base blocks or standards.
The capacity of the furnace may be increased or diminished by changing the
speed of its revolutions, or by changing the angle of its inclination.
To permit of the latter the under sides of the blocks q, q3 are provided with
male plates adapted to fit into female plates on the block 3 thus forming a
rocking bearing, which permits the tilting of the furnace and the mechanism for.
revolving the same without the liability of disarranging the parts.
s, and are cast iron frames fastened to the side of the smoke chamber and t, t
are aprons, elliptical in form, fastened to the said frames respectively and extend-
ing nearly to and around the tube h; $2, are similar cast iron frames
fastened to the side of the furnace and 2, 3 similar aprons fastened to the
said frames respectively and extending nearly to and around the tube i, the said
frames and aprons serving to close the openings around the said tubes.
When it is desired to increase or diminish the angle of inclination of the tubes,
the base blocks under and near the feed end of the furnace are raised or lowered
and the aprons t and t, 3 and 13 raised or lowered as the case may be. The said
angle of inclination is adjusted by jack-screws or other suitable means.
It is to be observed that the furnace is always perfectly balanced, no matter.
what position the tubes are in, as may be seen from examination of Figure 3 in
which represents the ore. The furnace therefore, requires but little motive
power to revolve it, thereby causing a considerable economy as compared with a
single cylinder roaster.
Also as the diameter of the tubes is small as compared with their lengths great
differences of temperature can be obtained between the fire end and the feed end,
for instance the fire end can be kept red hot while the feed end will remain com-
paratively cool, the heat being absorbed by the ore and moisture when the furnace
is used for drying ore, whereas, in a single tube furnace, the flame would rush
through and heat the roaster nearly as hot as the feed end as at the fire end and
resulting in a great waste of fuel.
Working results have shown that my four tube furnace will dry a given
quantity of ore with about sixty per cent. less fuel and eighty per cent. less power
than a single tube furnace would consume in drying a similar quantity, the area
of the single tube being equal to the aggregate area of the four tubes."
The operation of the furnace in roasting the ore, in so far as it has not already
been described, is as follows:-
As the furnace revolves, the raw ore is fed into the large tube h, and gradually
passes into the small tubes a¹, a², a³ and a¹ and thence along them to the discharge
end. The small tubes bring the flame and gases in intimate contact with the ore,
while the hollow rabbles at the same time eject pure, hot air uncontaminated by.
the products of combustion, directly into and through the entire mass of ore as
the furnace revolves thus oxidizing and completing the roasting in the most rapid
and perfect manner.
When the furnace is to be used for roasting, I prefer the form of discharge end
or hood having a conical end I as shewn in Figures 7 and 8.
In this arrange-
ment the hot gases from the fixed fire box enter at the opening A and the roasted
ore is discharged through the openings B in the hood which are in the form of

page_text: hollow castings E set into the fire clay d and are secured to the hood by means of
bolts F, F. The said openings are located at intervals around the hood and as
during the revolution of the cylinder they successively come to the bottom as
at B2 Figure 8, the roasted ore drops out through them into a hopper placed out-
side the furnace,
C is a fixed iron band covering all the holes B except one or two near the bottom
of the furnace, the said band serving to prevent the flame and hot gases from
escaping through the other holes or openings.
This band is somewhat similar to a brake strap on a wheel and is kept in its
proper position by means of flanges G, G on the outer faces of the castings E, E
and by means of a suitable support H and rods I, I.
K is a T-iron rib secured to the band C for strengthening the latter.
In drying ore the furnace is operated in a similar manner to that before
described except that the ore to be operated on is coarser than when being roasted
and the temperature employed is lower; here also the hot air ejected into the body
of the ore as the furnace is revolved rapidly carries off the moisture and dries the
ore more effectually than if it were subjected alone to the action of the flame and
gases of combustion passing over it.
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. In a roasting or drying furnace the combination of a series or plurality of
independent cylinders or tubes symmetrically arranged around a common axis
mounted in an inclined position so as to be rotated as one and adapted to receive
charges of ore which balance one another a combustion chamber discharging
its products of combustion through all the tubes simultaneously and means, pro-
vided in each tube, for sending pure hot dry air through the charges of ore during
rotation, substantially as described and specified.
2. In a roasting or drying furnace, a revoluble cylinder or tube in combination
with a hollow rabble fixed relatively thereto and means for supplying air through
the said rabble to the charge during the process of roasting or drying, sub-
stantially as specified.
3. In a roasting or drying furnace, a revoluble cylinder or tube in combination
with a hollow rabble comprising an air tube having adjacent communicating
passages and air outlets leading into the said cylinder, the said rabble being fixed
relatively with the said revoluble tube to the interior thereof, and with means for
supplying air to the said rabble during the process of roasting, substantially as
specified.
4. In a roasting or drying furnace, a revoluble cylinder or tube in combination
with a hollow rabble fixed relatively thereto to the interior thereof, the said rabble
comprising an air tube having adjacent communicating passages and air outlets
leading into said cylinder, with means for preventing the air passages from
becoming clogged, and with means for supplying air to the said rabble while the
cylinder is revolving, substantially as specified.
5. In a furnace for roasting and drying ores, a revoluble group of independent
cylinders terminating in a single tube or hood at the feed end of the apparatus,
and in a single tube at the discharge end, in combination with means for revolving
the said group of cylinders, means for sending heated gases simultaneously
through the cylinders while in revolution, and means for feeding ore to the
same, and means for ejecting pure, hot, dry air into the said ore, substantially as
specified.
6. In a furnace for roasting or drying ores, a revoluble group of cylinders pro-
vided both at the feed end and at the discharge end with enlarged terminal tubes
or extensions, in combination with a feeding hopper and chute, means for revolv-
ing the said group of cylinders and means for supplying air to the ore under

page_text: treatment therein, during the process of roasting or drying through a hollow
rabble located in each cylinder, substantially as specified.
7. In a furnace for roasting or drying ores, the revoluble group of tubes or
cylinders a¹, a, a³, at in combination with the hollow rabbles, fixed relatively
thereto and having communicating passages and outlets, and means for supplying
air through the said rabbles to the ore during the process of roasting or drying,
substantially as specified.
8. In a furnace for roasting or drying ores, the revoluble group of tubes or
cylinders a¹, a, a, at in combination with the hollow rabbles 1, (one in each tube)
fixed to the insides thereof, the said rabbles being closed at both ends and having
passages, and perforations 1, the supply pipe m, the air box n, the distributing
pipes n', n², n³, n* and means for supplying air through the supply pipe m and the
distributing pipes while the furnace is in operation, substantially as specified.
9. The combination of a revoluble group of tubes or cylinders having a single
terminal tube or extension at each end, hollow rabbles, fixed to the insides of the
said cylinders and having communicating passages and outlets means for revolving
the said group of cylinders, means for sending heated products of combustion
through all the cylinders simultaneously during rotation, and means for supplying
air through the said rabbles and their outlets to the ore during its agitation whilst
being revolved and heated, all substantially as and for the purposes specified.
10. In a furnace for roasting and drying ores, a discharge hood provided with a
conical end, the said hood having discharge holes around its periphery and near
the point where the conical end is joined thereto, and means for covering said
discharge holes, substantially as described.
11. In a furnace for roasting and drying ores, the revoluble group of indepen-
dent cylinders terminating in a single large tube or hood provided with a conical
end, the said hood being also provided with discharge holes located around its
periphery and at the point where the conical end is joined to the hood, and a band
for covering the said discharge holes, substantially as described.
L 001
T
P
"1 1000
G. F. REDFERN & Co.,
4, South Street, Finsbury, London, Agents for the Applicant.