Improvements in the Construction of Rotary Furnaces for the Calcination of Sulphide and other Ores.
Year: 1890

page_text: Date of Application, 17th Nov., 1890-Accepted, 30th, May, 1891
COMPLETE SPECIFICATION.
Improvements in the Construction of Rotary Furnaces for the
Calcination of Sulphide and other Ores.
OF
I, FRANCIS HYLTON MOLESWORTH of Globe Chambers, Grote Street Adelaide
in the Province of South Australia Analytical Chemist, do hereby declare the
CONSTRUCTION
nature of my invention for "IMPROVEMENTS IN THE
ROTARY FURNACES FOR THE CALCINATION OF SULPHIDE AND OTHER ORES"
and in what manner the same is to be performed, to be particularly described and
ascertained in and by the following statement :-
My invention relates to certain improvements in the construction of rotary
furnaces for calcining metalliferous ores, and more particularly gold and silver
bearing and other ores containing sulphides or arsenides.
The special object of my invention is to provide a rotary calciner of such
construction as to admit of the heat being applied from the outside in such manner
as to be evenly distributed over the whole of its surface. By the employment of
this method of heating, the oxidising properties of the atmosphere are utilised to
the fullest extent and their effect is not in any degree neutralised by the gases or
other products of the combustion of the fuel of the heating furnace.
A further object of my invention is to construct the rotating cylinder of the
calciner of such form as to concentrate at their inlet, the per-oxide or other gas
which may be introduced during the process of calcination, whilst at the same time
permitting the free escape of the gases formed by the combustion of the oxidised
sulphides.
I accomplish the more even distribution of the heat over the whole of the surface
of the rotary calciner by constructing a series of flues arranged spiral fashion around
or along the body of the calciner. By this means the heat or flame from the
furnace is caused to circulate around or along the body of the calciner from end
to end until it finally escapes into the flue connected with the chimney stack.
The calciner itself is constructed with converging sides, the smaller end being
that at which the ore is discharged and at which the peroxide or other gas-if such
be used to assist the process of oxidisation-is allowed to enter, the larger end being
that into which the ore is fed from the hopper, and from which the gases formed
by the combustion of the oxidised sulphides escape into a condensing chamber
immediately connected with the same. provide the interior of the calciner with a
series of ledges by means of which the ore is lifted and then allowed to fall, being
gradually carried forward during the process from the entrance to the exit end of
the calciner, from which it is finally discharged into a shoot, to be removed for after
treatment.
In order that my invention may be the better understood 1 will now proceed to
describe the same by reference to the accompanying drawings, in which
Fig. I is a sectional elevation of the rotary calciner and furnace.
Fig. 11 a half end sectional elevation of the same.
Fig. III side sectional elevation of longitudinal flues.
Similar letters refer to similar parts in all figures.
A is a calciner having converging sides, and constructed preferably in sections
bolted together. A' internal shelves projecting inwards from the sides of the
calciner A. A discharge end of the calciner A provided with suitable central
boss. A spindle, one end of which is secured to the central boss of the discharge
end of the calciner A and the outer is provided with suitable bearing and pulley or
gear wheel by means of which it is driven. A friction rollers by which the
calciner A. is supported, and upon which it revolves. B furnace of any ordinary
construction. B¹ flues extending spiral fashion around or along the whole length of

page_text: the brickwork which forms the outer casing of the calciner A and provided with
soot doors in the ordinary way. B outlet flue to chimney stack. B³ ash
pit. Chopper from which the ore to be treated is fed into the inlet end of the
calciner A. D condensing chambers immediately connected with the inlet end of
the calciner A. E discharge shoot from which the roasted pyrites are removed for
after treatment. F inlet pipe, by means of which nitrogen peroxide or other gas is
introduced into the calciner for the purpose of assisting the more rapid oxidisation
of the sulphides or arsenides contained in the ore.
It will be readily perceived that from the special construction of the flues B¹ the
flame or heat from the furnace B is caused to circulate around the outside of the
calciner A from end to end in spiral fashion and in this way even temperature,
capable of being controlled can be maintained during the whole of the process.
Or, by the alternative construction of the flues shewn in Fig. Ill the flame or heat
will circulate backwards and forwards along and around the whole length of the
calciner until it reaches the outlet flue B².
From this special construction of the rotary calciner A with converging sides, a
peroxide or other gas used for securing the more perfect oxidisation of the suphides
or arsenides contained in the ore under treatment is concentrated upon the ore
during the final period of the operation, whilst at the same time the gases formed
in the calciner by the combustion of the oxidised sulphides or arsenides escape
freely from the larger end into the condensing chambers immediately connected
therewith.
The speed at which the calciner is driven, being under control may be varied
according to the nature of the ore under treatment in such way that the pyrites
may be carried through more or less readily according to the sulphur or arsenic
which they may contain.
Having now particularly described and explained the nature of my said inven-
tion and in what manner the same is to be performed I declare that what I
claim is :-
First. The construction of the furnaces of rotary calciners to which heat is
applied from the outside with flues arranged spiral fashion around the rotary
cylinder of the calciner substantially as herein described and for the purpose
indicated.
Second. The construction of the furnaces of rotary calciners to which heat is
applied from the outside with flues arranged in longitudinal spiral fashion from end
to end of and around the rotary cylinder substantially as herein described and
shewn in Fig. III and for the purpose indicated.
Third. In rotary calciners to which heat is applied from the outside by means of
spiral flues, the construction preferably in sections of the body of the calciner
with converging sides, substantially as herein described and for the purpose
iudicated.
Fourth. The herein described calciner and furnace as a combination of parts.
Dated this 14th day of October 1890.
F. H. MOLESWORTH.
W. P. Thompson & Boult,
Agents for the Applicant.