IMPROVEMENTS IN CALCINING ORES AND MINERALS
Year: 1868

page_text: LETTERS PATENT to Robert Oxland, of Plymouth, in the County of
Devon, Metallurgical Chemist, and John Hocking, the younger, of
Redruth, in the County of Cornwall, Engineer, for the Invention of
"IMPROVEMENTS IN CALCINING ORES AND MINERALS."
Sealed the 16th March 1869, and dated the 25th September 1868.
PROVISIONAL SPECIFICATION left by the said Robert Oxland and
John Hocking at the Office of the Commissioners of Patents, with
their Petition, on the 25th September 1868.
We, ROBERT OXLAND, of Plymouth, in the County of Devon, Metal-
lurgical Chemist, and JOHN HOCKING, the younger, of Redruth, in the
County of Cornwall, Engineer, do hereby declare the nature of the said
Invention for "IMPROVEMENTS IN CALOINING ORES AND MINERALS," to be as
follows:-

page_text: them to heat in contact with heated air by passing them through a
revolving tube or cylinder kept in constant steady motion regulated in
speed so as to keep them under the influence of heat a greater or less
length of time varying according to the constitution of the ores. The
tube is constructed of either wrought or cast iron, lined with fire-brick,
about 30 feet long and 4 feet diameter. On the exterior of the tube
are three or more flanged cast-iron rings which work on friction rollers,
and by which the tube is supported. The rotatory motion is imparted
by an endless screw working into a cogged ring fixed on the side of one
of the cast-iron rings. The ore is supplied in a regular steady stream
at the end furthest from the fire, and by the revolving of the tube which
is elevated at one end above the horizontal line (and which elevation
may be varied according to the requirements of the different ores) it is
advanced to the end of the tube or cylinder nearest to the fire, and from
it drops into a chamber, through which the fire passes from the furnace
into and through the tube.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said Robert Oxland and John Hocking in the Great
Seal Patent Office on the 25th March 1869.
TO ALL TO WHOM THESE PRESENTS SHALL COME, we, ROBERT
OXLAND, of Plymouth, in the County of Devon, Metallurgical Chemist,
and JOHN HOCKING, the younger, of Redruth, in the County of Cornwall,
Engineer, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Twenty-fifth day of September, in the year
of our Lord One thousand eight hundred and sixty-eight, in the thirty-
second year of Her reign, did, for Herself, Her heirs and successors, give
and grant unto us, the said Robert Oxland and John Hocking, Her
special licence that we, the said Robert Oxland and John Hocking, our
executors, administrators, and assigns, or such others as we, the said
Robert Oxland and John Hocking, our executors, administrators, and
assigns, should at any time agree with, and no others, from time to
time and at all times thereafter during the term therein expressed,
should and lawfully might make, use, exercise, and vend, within the

page_text: United Kingdom of Great Britain and Ireland, the Channel Islands,
and Isle of Man, an Invention for "IMPROVEMENTS IN CALCINING ORES AND
MINERALS," upon the condition (amongst others) that we, the said Robert
Oxland and John Hocking, our executors or administrators, by an instru-
ment in writing under our or their hands and seals, or under the hand
and seal of one of us or them, should particularly describe and ascertain
the nature of the said Invention, and in what manner the same was to
be performed, and cause the same to be filed in the Great Seal Patent
Office within six calendar months next and immediately after the date of
the said Letters Patent.
NOW KNOW YE, that I, the said Robert Oxland, on behalf of myself
and the said John Hocking, do hereby declare the nature of the said
Invention, and in what manner the same is to be performed, to be
particularly described and ascertained in and by the following statement
thereof, that is to say:-
The said Invention consists in calcining ores, such as tin and copper
containing sulphur, arsenic, or other foreign substances, by exposing
them to heat in contact with heated air by passing them through a
revolving tube or cylinder kept in constant steady motion, regulated in
speed so as to keep them under the influence of heat a greater or less
length of time, varying according to the constitution of the ores. The
tube is constructed of either wrought or cast iron lined with fire-brick,
about 30 feet long and 4 feet in diameter. On the exterior of the tube
are three or more cast-iron rings which work on friction rollers, by which
the tube is supported. The rotatory motion is imparted by an endless
screw working into a cogged ring. The ore is supplied in a regular
steady stream at the end farthest from the fire, and by the revolving of
the tube, which is elevated at one end above the horizontal line (and
which elevation may be varied according to the requirements of the
different ores), it is advanced to the end of the tube or cylinder nearest
to the fire, and from it drops into a chamber.
And in order that our said Invention may be most fully understood
and readily carried into effect we will proceed by reference to the
annexed Drawings to describe more fully the manner in which we prefer
to operate.
The furnace consists of a fire-place or heating compartment, in which
either coal, coke, or other solid fuel may be burnt, or in which gas may

page_text: be consumed as the source of heat of a calcined ore chamber immediately
adjacent, into which the calcined ore is delivered, of a wrought or cast
iron tube lined with fire-brick of a series of perpendicular flues for
catching any fine ore that may be blown over, and of cast or wrought
iron covering plates on the top of these flues for the drying of the raw
ore with the spare heat passing into the flues.
adjacent, into which the calcined ore is delivered, of a wrought or cast
iron tube lined with fire-brick of a series of perpendicular flues for
eatching any fine ore that may be blown over, and of cast or wrought
iron covering plates on the top of these flues for the drying of the raw
ore with the spare heat passing into the flues.
The annexed Drawing shews the particulars in detail.
Figure 1 is a sectional elevation of the whole of the furnace; Figure 2
is a transverse section of the tube.
In Figure 1 A is the fire-place; a', the ash-pit; b', the fire-bars; c', the
dumb plate; d', the fire-door; e', the fire-bridge and arch covering the
wrinkle or calcined ore chamber which with the covering arch h¹ forms
the flue through which the fire passes into the tube. Over the arch h
is another arch i forming the flue k through which air passes from the
entry l.
The air is thereby considerably heated before it comes into
contact at m with the products of combustion passing from the fire-
place into the tube.
The object of this arrangement is to provide the quantity of air
necessary for the perfect combustion of the fuel and also that required
for the perfect calcination of the ores or minerals. The entry should
be provided with a valve or damper for the regulation of the supply
of air. The tube B is constructed of wrought or cast iron lined with
fire-brick about thirty feet long and three feet internal diameter. The
lining of fire-brick m' is so arranged that every third or fourth brick
shall project one or more inches beyond the others, so as to form narrow
shelves for carrying up the ore, and as it becomes sufficiently elevated
projecting the same forward through the passing heated air and products
of combustion. Within the tube are three or more diaphragms or
baffle plates or discs of fire-brick or tiles, or of cast or wrought iron n
so supported as to leave a sufficient space between the inside of the
tube and the edge of the baffle plate all round for the passage of the
products of combustion. This space is varied according to the quantity
and size of the portions of ore passing through the furnace. If the
ore be in powder a space six inches wide will be sufficient, if the ore
be larger the width of the space may conveniently be increased up
to nine inches. The gaseous products of combustion pass off at 6² into
the chamber C; the tube is surrounded with three rings of wrought or

page_text: cast iron as at 63, 4, 5, which are in contact with the tube only at the
four places of attachment at c¹, 3, 3, ', in Figure 2, leaving spaces
of two inches between the tube and the ring through which the air
may circulate and cool the ring. The tube is supported by these rings
on three pair of friction rollers, as shewn in Figure 1 at 66, 7, and
in Figure 2 at d and e at an inclination of half an inch to an inch or
more to the foot. The revolution of the tube is produced by machinery
gearing into the cog wheel fastened in like manner to the other rings
and as shown in Figure 1 at 6º. We find it convenient to drive the
tube at a speed of one revolution in four minutes, but the speed may
be varied; at this speed an inclination of one inch in the foot will
cause the ore to travel from end to end of the tube in about two hours
and a half. If a more rapid travel be required it may be obtained
either by driving the tube faster or by increasing its inclination.
Similarly the ore may if desired be caused to dwell longer in the tube
by driving it at a slower speed or by diminishing its inclination. The
chamber C is divided into compartments by the partitions a, b, c,
by which any fine ore carried over is caught and deposited in the
bottom of the chamber, from which it may be removed by the doors d
and e. The products of combustion pass on to the chimney by the
flue f; the damper 9 serves for the regulation of the draft.
ore is dried on the iron plate and fed through the tube h; the ore
may also be fed by an endless or Archimedian screw. The calcined
ore is discharged from the end of the tube nearest the fire-place into
the wrinkle or calcined ore chamber, from which it may be removed
as required at the doors g'. This furnace may be used for burning
the "smalls" of iron pyrites for the manufacture of sulphuric acid.
For this purpose instead of heat from other fuel that from burning of
large pyrites may be rendered available; the pyrites kiln taking the
place of the coal fire-place shewn in the Drawing. The rate of revolution
of the tube and the quantity of smalls supplied to the furnace is so
regulated that the calcined ore discharged into the wrinkle may be
practically free from sulphur. In certain cases where the sulphur ore
is very fusible it may be desirable to pass even the larger ore through
the tube, and instead of discharging the perfectly calcined ore into the
wrinkle to pass it in a state of partial calcination into the kiln where
the calcination may be completed without risk of fusion. The furnace
is also intended for the calcination of copper ores, in order to the
The raw

page_text: utilization of the arsenic or of the arsenic and sulphur contained in
them to the calcination of ores of arsenic containing small quantities
of copper, or of tin, or of both, in order to the utilization of either or of
both; also to the calcination of ores of tin, in order to the removal
of the sulphur and arsenic, the evolution of carbonic, and of any
carbonate of iron contained in them, and oxidation of the iron, and
to the utilization of the arsenic, sulphur, and copper and oxides of iron
contained in them; also for the calcination of ores of zinc containing
sulphur such as blende or black jack ores of zinc containing carbonic
acid, such as calumine ores of iron containing carbonic acid or car-
bonic acid and sulphur, in order to the conversion of them as nearly
as possible into oxides of iron; also to the calcination of burnt pyrites
containing small portions of copper with or without common salt or
muriatic acid. Ores containing much sulphur and arsenic will require
but little fuel for their calcination, but those which contain but little
or none may be advantageously mixed with a small proportion of ground
or small coal or coke or charcoal, so that heat may be produced by its
combustion within the ore at an earlier stage of the process.
By the
use in the manner above described of a revolving tube or cylinder for
burning or calcining ore and minerals which are fed continuously into
the tube or cylinder at the further end, or that most distant from the
furnace and discharged at the end nearest to the furnace, the ore or
mineral is at first but moderately exposed to the fire heat, here the
sulphur and arsenic which the ore may contain are for the most part
burnt off, and their combustion raises the temperature of the charge.
By the time the sulphur and arsenic are for the most part consumed
the charge has approached more nearly to the fire which then completes
the roasting. In this way of working there is little risk of overheating
the ore or mineral at the commencement of the process, so as to cause
it to fuse and agglomerate, as frequently happens unless great care be
taken in the management in ordinary roasting and calcining furnaces
where the ore or mineral when first charged in is exposed both to the fire
heat and the heat developed by the combustion of the sulphur and arsenic
which it contains. In some cases I remove the fire-place A from the
other parts of the apparatus and pass into the tube by suitable flues
air highly heated by a furnace or fire at a distance.

page_text: tube or cylinder by exposing them to heat within the tube or cylinder
in the manner and for the purposes herein described.
In witness whereof, I, the said Robert Oxland, have hereunto set
my hand and seal, this Twenty-fourth day of March, in the year
of our Lord One thousand eight hundred and sixty-nine.
ROBERT OXLAND. (L.S.)