IMPROVE- MENTS IN THE ROASTING OR CALCINING OF ORES, APPLICABLE ALSO TO THE OXIDISING OF OTHER SUBSTANCES
Year: 1859

page_text: LETTERS PATENT to John Henry Johnson, of 47, Lincoln's Inn Fields,
in the County of Middlesex, and of 166, Buchanan Street, in the City
of Glasgow, North Britain, Gentleman, for the Invention of "IMPROVE-
MENTS IN THE ROASTING OR CALCINING OF ORES, APPLICABLE ALSO TO THE
OXIDISING OF OTHER SUBSTANCES."-A communication from abroad by
Professor Jean François Persoz, of Paris, in the Empire of France.
Sealed the 4th November 1859, and dated the 20th May 1859.
PROVISIONAL SPECIFICATION left by the said John Henry Johnson
at the Office of the Commissioners of Patents, with his Petition, on the
20th May 1859.
I, JOHN HENRY JOHNSON, of 47, Lincoln's Inn Fields, in the County of
Middlesex, and of 166, Buchanan Street, in the City of Glasgow, North
Britain, Gentleman, do hereby declare the nature of the said Invention for
"IMPROVEMENTS IN THE ROASTING OR CALCINING OF ORES, APPLICABLE ALSO TO THE
OXIDISING OF OTHER SUBSTANCES," a communication from abroad by Professor
Jean François Persoz, of Paris, in the Empire of France, to be as follows:―
This Invention relates to an improved system or mode of carrying out the
process of roasting or calcining ores, or of oxidising other substances, whereby
the products of combustion, which usually escape by the chimney of the
furnace employed, are collected and utilised, the noxious sulphurous emanations
arising from the roasting or calcining of ores is prevented, the sulphur emitted
from the ores during the roasting or calcining process is utilised, and the
disulphuration of ores is greatly facilitated.
The essential feature of this Invention consists in the substitution for the
draught of the ordinary chimney, a physical or mechanical combination, by
means of which the products of combustion and noxious sulphurous vapours

page_text: are collected and expelled at pleasure without any necessity for modification or
change in the construction of the furnace retorts or other calcining apparatus
employed. As an example of the mode of effecting this object, the ordinary
chimney may be replaced by an exhaust and force pump, suitably constructed,
to withstand the heat of the vapours or gases, and also the corrosive effects of
sulphurous acid. This pump draws all the products of combustion and sul-
phurous fumes from the body of the furnace, and directs them to any convenient
locality where the otherwise waste heat may be employed, in the evaporation
of liquids or in the drying of substances generally, whilst the sulphurous acid
when existing may be utilized either by direct application or employed in
the manufacture of sulphuric acid. As the mixture of air, sulphurous acid,
and products of combustion attain a very high degree of temperature, it is
proposed to cause them to pass through chambers or flues suitably arranged,
wherein they are partly cooled, and the particles of matter which may have
been carried along with the draught are deposited before reaching the pump.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said John Henry Johnson in the Great Scal Patent Office on
the 19th November 1859.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, JOHN
HENRY JOHNSON, of 47, Lincoln's Inn Fields, in the County of Middlesex,
and of 166, Buchanan Street, in the City of Glasgow, North Britain,
Gentleman, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Twentieth day of May, in the year of our Lord
One thousand eight hundred and fifty-nine, in the twenty-second year of
Her reign, did, for Herself, Her heirs and successors, give and grant unto
me, the said John Henry Johnson, Her special license that 1, the said
John Henry Johnson, my executors, administrators, and assigns, or such
others as I, the said John Henry Johnson, my exccutors, administrators, or
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 law-
fully might make, use, exercise, and vend, within the United Kingdom of
Great Britain and Ireland, the Channel Islands, and Isle of Man, an Inven-
tion for "IMPROVEMENTS IN THE ROASTING OR CALCINING OF ORES, APPLICABLE ALSO TO
THE OXIDISING OF OTHER SUBSTANCES," a communication from abroad by Professor
Jean François Persoz, of Paris, in the Empire of France, upon the condition

page_text: (amongst others) that I, the said John Henry Johnson, by an instrument in
writing under my hand and seal, should particularly describe and ascertain the
nature of the said Invention, and in what manner the same was to be per-
formed, 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 John Henry Johnson, 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, that is to say:-
The said Invention relates to an improved system or mode of carrying out
the process of roasting or calcining ores, or of oxidising other substances,
whereby the products of combustion which usually escape by the chimney of
the furnace employed are collected and utilized, the noxious sulpherous ema-
nations arising from the roasting or calcining of ores is prevented. The
sulphur emitted from the ores during the roasting or calcining process is
utilized, and the desulphuration of ores is greatly facilitated.
The essential feature of this Invention consists in the substitution for the
draught of the ordinary chimney, a physical or mechanical combination, by
means of which the products of combustion and noxious sulphurous vapours
are collected and expelled at pleasure without any necessity for modification or
change in the construction of the furnace, retorts, or other calcining apparatus
employed. As an example of the mode of effecting this object, the ordinary
chimney may be replaced by an exhaust and force pump suitably constructed
to withstand the heat of the vapours or gases, and also the corrosive effects of
sulphurous acid. This pump draws all the products of combustion and sul-
phurous fumes from the body of the furnace, and directs them to any conve-
nient locality where the otherwise waste heat may be employed in the evapora-
tion of liquids, or in the drying of substances generally, whilst the sulphurous
acid when existing may be utilized either by direct application, or employed in
the manufacture of sulphuric acid. As the mixture of air, sulphurous acid, and
products of combustion attain a very high degree of temperature, it is proposed
to cause them to pass through chambers or flues suitably arranged wherein
they are partly cooled, and the particles of matter which may have been
carried along with the draught are deposited before reaching the pump.
Having thus briefly set forth the nature of the said Invention, I will now
proceed to traco generally the process adopted up to the present time for
treating ores containing sulphur, in order that the precise objects of the said
Invention may be more clearly understood.

page_text: In the roasting of ores, reverberatory furnaces are employed of various
forms and dimensions, but having this feature common to all, that is, that the
hearth which is formed with an arched top or cover, and on to which are
spread the ores to be roasted, communicates at one side with a chimney, the
diameter and height of which depends upon the volume of air to be passed
over the ore in a given space of time. The object indeed of this chimney is
to create a draught or current of external air, and cause it to penetrate into
the interior of the furnace where it is required to assist the combustion
of, first, the fuel which is required to produce the heat necessary to the
chemical action; second, the ore which in the process of roasting produces
sulphurous gas and a metal, sulphurous gas and an oxide, and sulphurous gas
and sulphates.
On the other hand, this hearth communicates with the external atmosphere
by as many holes as may be required for the easy introduction or removal of
the ore, and for the stirring of the same during the roasting, in order to facili-
tate the oxidation of the sulphur by the continual removal of the surfaces in
contact with the current of air. After having traversed the furnace, where it
loses the greater part of its oxygen, the air enters the chimney, drawing off
with it the sulphurous acid produced, which becomes dispersed and wasted in
the atmosphere, rendering it equally hurtful to animal and vegetable life.
The high price demanded for raw sulphur at certain periods has determined
some manufacturers of sulphuric acid to utilize the sulphur of pyrites. For
this purpose the pyrites are burnt in furnaces or muffles in proximity to leaden
chambers, and the sulphurous acid arising from the burning or roasting process
is caused to enter these chambers by means of a chimney erected at the
opposite or farthest extremity of the chambers. But this process, besides that
it is only applicable to certain kinds of sulphur, is liable to cause great irregu-
larity in the working of the leaden chambers, and prevents, by reason of the
resulting products, the employment of many agents which would effect tho
desulphuration of the ores in a perfect and satisfactory manner.
The process which constitutes the present Invention is totally free from
these objections, and if the best arrangements of ordinary furnaces be pre-
served, the present improved process admits of the roasting or calcining of
minerals containing sulphur without injury to health, and enables the whole of
the sulphur contained therein to be utilized. For this purpose the chimney,
which has always been considered an essential organ up to the present time,
is replaced by an exhaust and force pump, which whilst producing the
mechanical effect of the chimney by removing the sulphurous acid formed in
the furnace, enables this acid to be utilized at will either by direct application

page_text: or by the manufacture or sulphuric acid, by its ulterior oxidation in suitable
apparatus.
Since the mixture of air and sulphurous acid which leaves the furnace
possesses a high degree of heat, it is proposed to pass it, before reaching the
piston of the pump, through suitably arranged chambers or cavities, in which
it is not only freed from any solid particles of matter which may have been
mechanically carried along with it, but is sufficiently cooled down. The
necessity for, causing a circulation of the gas before using it, so far from being
an objection, enables, on the contrary, a great portion of the hitherto waste
heat to be utilized with profit, since it may be applied either to the ovapo-
ration of liquids; or to the drying of substances generally.
In roasting or calcining ores according to this Invention, recourse is had
eeither to simple or complex reverberatory furnaces, such as are well known in
the science of metallurgy, or to retorts of cast-iron or fire-clay, of a similar
construction to those employed in gasworks, with this slight difference, that.
their roofs are lower in order to effect greater economy of heat, or to cylinders
placed vertically, or to a species of muffle with a low roof.
According to circumstances, the receptacle which is used for the desulphu-
ration of the ore is closed or open, and the ore heated directly by the flame
circulating in the interior of the furnace, or indirectly by radiation from the
sides, but in either case the gas, as it passes from the furnace, retort, or
cylinder, is immediately drawn into a passage or flue divided into as many
compartments as may be necessary to separate the matters held in suspension
therein, and for effecting the cooling of the gas. The extremity of this flue
or passage is in communication with the exhaust and force pump, which
removes the gases and directs them to the apparatus intended for collecting
the sulphurous acid, or for employing them in any other manner. Amongst
the matter carried off by the gases are frequently found particles of arsenious
acid in variable proportions, sometimes oxide of antimony, and always a con-
siderable quantity of sulphuric acid; arising from the decomposition of certain
accidentally formed sulphates, as well as numerous small particles of raw or
calcined ore.
.
In the calcining or desulphuration of ores according to this Invention,
different methods of treatment may be employed according to the nature of
the ore. For example, the ore alone may be introduced into the furnace where
it is to undergo the oxidising action of the air after having been first broken
up or divided. Or before submitting it to any treatment, or after partially
roasting it, the ore may be mixed with suitable proportions of sulphuric acid,
bisulphates, or sulphates or carbon, and the whole is calcined whilst excluding

page_text: the air, so as to accomplish, as the case may be, one or other of the following
reactions:-
reactions:-
4 SO'
$
+M, SMO, SO3 + 4 SO 2
(MO, SO) + M, S = 4 M 0, +450*
(MO, SO) + MS=5M+ 5 SO²
MO, SO ³ +C = M + SO * +CO
Any kind of exhaust and force pump capable of resisting the action of the
gases arising from combustion, and particularly the corrosive action of sul-
phurous acid, and which will not be incommoded in its working by the heat
still retained by the gases, for a short time after their leaving the furnace, will
perfectly answer the objects to be effected in the calcining process, and in all
processes for the axidation of bodies. A pump having its essential parts con-
structed of cast-iron and vulcanized india-rubber will bo found to answer
admirably.
Having now described and particularly ascertained the nature of the said
Invention, and the manner in which the same is or may be used or carried
into effect, I would observe in conclusion that what I consider to be novel
and original, and therefore claim as the Invention secured to me by the
hercin-before recited Letters Patent, is,―
First, the general system or mode of roasting or calcining and oxidising
ores and other substances, and utilizing the products obtained in such pro-
cesses as herein-before described.
Second, the application and use to and in the roasting or calcining of ores,
and the inceneration of combustible bodies of a physical or mechanical means
for drawing off the gases and vapours produced by such processes, and utilising
the same, without permitting them to pass into the atmosphere, as herein-
before described.
Third, the substitution of an exhaust and force pump for the ordinary
draught chimney in the roasting or calcining of ores, and incineration of com-
bustible substances for the purpose herein-before described.
In witness whereof, I, the said John Henry Johnson, have hereunto set
my hand and seal, this Nineteenth day of November, One thousand
eight hundred and fifty-nine.
J. HENRY JOHNSON. (L.B.)