IMPROVE MENTS IN THE TREATMENT OF PIT COAL, AND IN THE SEPARATION OF FOREIGN MATTERS THEREFROM
Year: 1858

page_text: LETTERS PATENT to Henry Bessemer, of 4. Queen Street Place, New
Cannon Street, in the City of London, for the Invention of "IMPROVE
MENTS IN THE TREATMENT OF PIT COAL, AND IN THE SEPARATION OF FOREIGN
MATTERS THEREFROM."
Scaled the 19th October 1858, and dated the 30th July 1858.
PROVISIONAL SPECIFICATION left by the said Henry Bessemer at the
Office of the Commissioners of Patents, with his Petition. on the
30th July 1858.
1. HENRY BESSEMER. of 4 Queen Street Place, New Cannon Street, in
the City of London, do hereby declare the nature of the Invention for
IMPROVEMENTS IN THE TREATMENT OF PIT COAL AND IN THE SEPARATION OF
FOREIGN MATTERS THEREFROM," to be as follows:--
My Invention consists in the separation of pyrites, shale, carbonate ni lime,
silica, and other foreign matters that are found associated with or which
become accidentally intermixed with pit, coal. This separation is effected by
the immersion of the mixture of coal and other matters in a tank or bath con-
taining a fluid, the specific gravity of which is greater than pure coal,, and less
Than the substances to be separated therefrom: every particle of the matter to
be operated upon (whatever its bulk may be) which is thrown into the bath
(unless it be of the precise specific gravity of the fluid therein contained) will
either float on the surface of the fluid or it will sink to the bottom of the bath,
and thus will be effected a complete separation of the coal from the various
foreign matters previously in a state of mechanical admixture therewith. The

page_text: floating pieces of coal may be removed from the surface of the fluid by any
convenient form of revolving or reciprocating skimming or raking apparatus,
and the foreign matters which sink to the bottom of the bath or tank may be
dredged out by any suitable arrangement of buckets or by an endless screw,
or preferably by a revolving or other sluice situated at the lowest part of the
tank, the bottom of which should in that case be made funnel shaped, so as
to direct the deposited matters to the proper point of exit, by which means
the process of separation may be carried on continuously, or if it be desired the
process may be made intermittent, the tank in that case being emptied from
time to time. And, further, in lieu of either raking or skimming the coal
from the surface of the fluid, the tank may be provided with a wide or with
several narrow weirs over which a current of the dense fluid (on which the
coal floats) may be made to flow and carry with it the floating pieces of coal
into a suitable receptacle, where a separation of the fluid from the solid parts
may be effected by drainage or filtration, or by centrifugal drying apparatus,
the fluid matter thus escaping at one end of the tank may be elevated by a
centrifugal pump or otherwise, and be made to enter the opposite end of the
tank charged with fresh portions of the mixture of coal and other matters,
which may be first moistened with water or may be well mixed with the dense
fluid in a drum or pug mill or by other convenient means prior to its entering
the bath. This supply of fresh materials to be acted upon may enter the
tank from above the surface of the fluid, or it may be made to enter the bath
by suitable feeding apparatus at some distance below the surface of the fluid,
whereby the lighter particles will have to float upwards for some distance
before they can flow over the weir, or be otherwise removed while the matters
that are heavier than the fluid will sink quietly down to the bottom of the
tank. When coal in a state of great purity is required. I prefer to separate
the greater part of the foreign matters by a first process, using the fluid bath
of rather a greater density than usual, and then treating the partially purified
coal a second time, in which case 1 prefer to make the fluid so near the
specific gravity of pure coal as to cause a much larger deposit to take place,
and thus only retain on its surface pieces of coal of extreme purity: the
deposited matters resulting from this second operation may be used for making
an inferior fuel. The coal may be used in any sized pieces, but in order to
render the process more perfect. I prefer to crush it between rollers or by
means of any other suitable crushing apparatus, so as to reduce the pieces to
a suitable size, and I also prefer to separate all the extremely small particles
or dust by a current of air, or by means of sieves, or by a combination of both.
The fluid used to form the floating bath may consist of any cheap liquid, the

page_text: specific gravity of which is greater than pure coal, and the density of which
admits of easy regulation. Metallic solutions, when rendered neutral, will be
found to answer well, and I have found a solution of iron in' muriatic acid
(when properly diluted to suit the density of the coal operated upon) very
suitable for the purpose.
In order to prevent a waste of the fluid, the coal should be well drained
after leaving the bath, and then have a shower of water fall over it, to
thoroughly cleanse the coal, or it may be moved progressively by a screw
along a semi-cylindrical trough in which waier circulates in an opposite
direction to that in which the coal is moving. The foreign matters separated
from the coal may also in like manner be drained and washed from the fluid
adhering to their surfaces, the wash water in both cases being allowed to flow
into a suitable evaporating pan, where it may be brought up to the required
density, and be again returned to the bath. When it is desired to have the
coal delivered in a dry state, a current of cold or heated air may be used, or
the coal may he'dried in a centrifugal drying apparatus, arranged so as to
discharge the dried coal continuously. It will be understood that the different
stages of the process herein-before described may be carried on independently
of each other, and in different localities, should it be found expedient to do so.
and on the other hand it will be understood that the entire process herein-
before described may be carried on in one combined apparatus, and thus
constitute a continuous self-acting process. The coal when thus treated and
separated from the foreign substances that were mechanically mixed therewith
may at once he used as fuel, or it may be made into artificial fuel by a partial
coking thereof in taper or conical wrought-iron retorts, or in other suitable
apparatus, the coal being used alone or mixed in any desirable proportion with
coal tar or with pitch obfained in the distillation of coal tar, and with or
without lime, the coking process not being carried so far as to deprive the
coal of the property of producing an abundant flame when used in a reverbera-
Or otherwise, the coal when
lory or other furnace where flame is desirable.
separated from its impurities in the manner herein-before described may be
used alone or mixed in any desirable proportion with coal tar or pitch, and
with or without lime, and be made into oven coke similar to the usual
It will be found
description, in so far as the amount of coking is concerned.
that coal when separated from pyrites and other foreign matters in the manner
herein-before described is especially suitable for the manufacture of coal gas,
and also for those metallurgic operations where the fuel itself or the products
of combustion are brought in contact with the metal.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said Henry Bessemer in the Great Seal Patent Office on the
28th January 1859.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I. HENRY
BESSEMER. of 4, Queen Street Place, New Cannon Street, in the City of
London, send greeting.
WHEREAS Her mosi Excellent Majesty Queen Victoria. by Her Letters
Patent, bearing date the Thirtieth day of July, in the year of our Lord One
thousand eight hundred and fifty-eight, in the twenty-second year of Her reign,
did. for Herself, Her heirs and successors, give and grant unio me, the said
Henry Bessemer, Ier special licence ihai T, the said Henry Bessemer, my
executors, administrators, and assigns, or such others as T. the said Henry
Bessemer, my 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, ise, exercise, and
vend, within the United Kingdom of Great Britain and Ireland, the Channel
Islands, and Isle of Man, an Invention for "IMPROVEMENTS IN THE TREATMENT
OF PIT COAL, AND IN THE SEPARATION OF FOREIGN MATTERS THEREFROM," upon the
condition (amongst others) that I. the said Henry Bessemer, my executors or
administrators, by an instrument in writing under my, or their, or one of their
hands and seals, 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 he filed in the Great Seal Patent Office within six calendar
months next and immediately after the date of the said Letters Palent.
NOW KNOW YE, that I, the said Henry Bessemer, do hereby declare the
nature of the said Invention, and in wbaf manner the same is to be per-
formed, to be particularly described and ascertained in and by the following
statement thereof, that is to say:--
Mineral or pit coal is very rarely, if ever, found in a state of absolute
purity, but is usually intermixed with other mineral or metallic substances
which are not only incombustible, but are more or less injurious in the many
metallurgical and other manufacturing processes in which pit coal is em-
ployed for not only is the quantity of combustible matter in a given weight.
of raw coal usually reduced by the presence of lime, clay, silica. shale, &c.,
but these incombustible substances having to be brought up to the same high
temperature as the rest of the materials in the furnace, absorb a portion of
the heat that might, but for their presence. have been usefully employed.
These substances therefore effect economically the value of the coal, but the

page_text: almost invariable presence in coal of pyrites or bisulphide of iron effects
chemically the value of the coal to a very great extent in operations such as
the smelting of iron ores, and the after-process of that manufacture, for the
commercial value of the iron produci is greatly modified by the amount of
the injurious mineral present in the coal employed; it is therefore desirable
to separate as far as practicable all the different carthy or mineral substances
associated with pit coal. Attempts have been made to separate the impurities
by a sort of washing operation, in which currents of water are caused to carry
and deposit the matters operated upon in different strata or io different parts
of the apparatus used. If we take a tall glass or other cylinder filled with
water or other fluid, and drop into it at the same moment several different.
sized fragments of pure coal heavier than the water or other fluid, the several
pieces will be seen to descend at different velocities, notwithstanding they are
of like specific gravity dependent on their peculiar shapes and on their size.
and also on the relative surface resistance opposed by the fluid to their
descending motion. Again, if these fragments or pieces were carried up or
along by currents of water or other fluid, they would obey the same law, and
would not all be taken to the same spot, but he deposited at distances varying
with the most minute difference in their exterior form as well as with their
cubic contents, the small thin fragments being carried beyond the large or
more cubic forms.
It follows that if this law of the resistance of fluids causes
a separation of the fragments or pieces of coal of like specific gravity, it will
do so with other matters combined or mixed with coal and with the pieces of
coal more or less impregnated or combined with impurities, such as pyrites,
and hence when it is attempted to separate the purer coal from the less pure
coal and from the separated impurities, they being of different specific
gravities and of different sizes. it happens that the separation cannot be
practically effected by currents of fluid; therefore avoid entirely the employ-
ment of this principle of the varying resistance of solids of different forms or
cubic contents to fluids in motion, and use the principle consequent on cm-
ploying fluids of greater specific gravity than that of coal, so that the better
parts of the coal may float and the less pure coal and the impurities sink.
My Invention consists in the separation of pyrites, shale, carbonate of lime,
silica, and other foreign matters that are found associated with or which
become accidentally intermixed with pit coal. By the immersion of the
mixture of coal and other matters in a tank or bath containing a fluid, the
specific gravity of which is greater than pure coal and less than the sub-
stances to be separated therefrom, every particle of the matter to be operated
upon (whatever its bulk may be), which is thrown into the hath (unless it be

page_text: of the precise specific gravity of the fluid therein contained) will either float
on the surface of the fluid or ii will sink to the bottom of the bathi, and thus
will be effected a complete separation of the coal from the various foreign
matters previously in a state of mechanical admixture therewith.
The power
of floatation of the purer coal on the surface of the fluid is not influenced by
the size or peculiarity in form of the pieces, since masses of one pound or
more in weight may be suspended for any length of time side by side with
other fragments not weighing a grain, the gravity of the fluid employed alone.
effecting its suspension and separation from other substances without me-
chanical force or the necessary of any motion of the fluid employed. In
order to illustrate this, it may be assumed (taking water as unity) that pare
coal has a specific gravity of 13. silica 26, carbonate of lime 27, shale 26,
and pyrites 39 to 41, hence we see that the lightest of these impurities is
about twice the specific gravity of coal, and the heaviest more than three
times its weight, thus affording ample means of separating them from coal
by the difference of their specific gravities. Now, if any fluid whose specific
gravity is greater than pure coal, say 135, is put into a tank or other vessel,
and lumps or fragments of raw coal be thrown therein, it will be understood
that all those lumps or fragments whose specific gravity exceeds 135 will
sink down to the bottom of the vessel, while all the lighter pieces of pure or
nearly pure coal will continue floating on its surface until removed; hence the
process of separating the coal from foreign matters, and from coal impregnated
or combined with foreign matters, may be effected without any machinery by
simply shovelling the coal to be treated into a tank containing the dense fluid.
while an attendant removes with a rake or skimmer all that floats upon the
surface, the heavy portions consisting of the foreign matters separated from
the coal being removed from the bottom of the tank from time to time, in
order to prevent their undue accumulation interfering with the skimming off
of the pure coal from the surface. I mention this simple mode of operation
to show that the separation of pure or comparatively pure coal from the great
bulk of foreign substances generally mixed or combined with it may be
effected by the simple action of gravity without having recourse to mechanical
force or motion of the fluid, and without any machinery heing employed in
the process.
Although I prefer in carrying my Invention into commercial
operation that certain mechanical appliances should be employed in order more
conveniently and more economically to carry on the same, it will therefore be
understood that the floating pieces of coal may be removed from the surface
of the fluid by any convenient form of revolving or reciprocating skimming
or raking apparatus, and the foreign matters which sink to the bottom of the

page_text: bath or tank may be dredged out by any suitable arrangement. of buckets, or
by an endless screw, or, preferably, by a revolving or other sluice situated at
the lowest part of the tank. the bottom of which should in that case be made
funnel-shaped, so as to direct the deposited matters to the proper point of
exit, by which means the process of separation may be carried on con-
tinuously, or, if it be desired. the process may be made intermittent, the tank
in that case being emptied from time to time.
And further, in lieu of either raking or skimming the coal from the surface
of the fluid, the tank may be provided with a wide or with several narrow
weirs, over which a current of the dense fluid (on which the coal floats) may
be made to flow and carry with it the floating pieces of coal into a suitable
receptacle, where a separation of the fluid from the solid parts may be effected
by drainage or filtration or by centrifugal drying apparatus. the fluid matter
thus escaping at one end of the tank may be elevated by a centrifugal pump
or otherwise, and be made to enter the opposite end of the tank charged with
fresh portions of the mixture of coal and other matters. which may be first
moistened with water or may be well mixed with the dense fluid in a drum or
pagill, or by other convenient means, prior to its entering the bath. This
supply of fresh materials to be acted upon may enter the tank from above the
surface of the fluid or it may be made to enter the bath by suitable feeding
apparatus at some distance below the surface of the fluid, whereby the lighter
particles will have to float upwards for some distance before they can flow
over the weir or be otherwise removed, while the matters that are heavier
than the fluid will sink quietly down to the bottom of the tank. When coal
in a state of great purity is required, I prefer to separate the greater part of
the foreign matters by a first process, using the fluid bath of rather a greater
density than usual and then treating the partially purified coal a second time,
in which case I prefer to make the fluid so near the specific gravity of purc
coal as to cause a much larger deposit to take place, and thus only retain on
its surface pieces of coal of extreme purity. The deposited matters resulting
from this second operation may be used for making an inferior fuel. The coal
may be used in any sized pieces, but in order to render the process more
perfect prefer to crush it between rollers or by means of any other suitable
crushing apparatus. so as to reduce the pieces to a suitable size, and I also
prefer to separate all the extremely small particles or dust by a current of
air or means of sieves, or by a combination of both.
The fluid used to form the floating bath may consist of any cheap liquid the
specific gravity of which is greater than pure coal and the density of which
admits of easy regulation. Metallic solutions when rendered neutral will be

page_text: found to answer well, and I have found a solution of iron in muriatic acid
(when properly diluted to suit the density of the coal operated upon) very
suitable for the purpose. I would, however, remark that any metallic or
other solutions may be used which have the requisite density and are not too
expensive, especially those met with in commerce as a waste product of some
other manufactures, such as the chloride of manganese: the chloride of
barium may also be employed, but I prefer to use the chloride of calcium,
although by no means confine myself to that substance.
In order to prevent a waste of the fluid the coal should be well drained
after leaving the bath and then have a shower of water fall over it to
thoroughly cleanse the coal. or it may be moved progressively by a screw
along a semi-cylindrical trough. in which water circulates in an opposite
direction to that in which the coal is moving. The foreign matters separated
from the coal may also in like manner be drained and washed from the fluid
adhering to their surfaces, the wash water in both cases being allowed to flow
into a suitable evaporating pan, where it may be brought up to the required
density and be again returned to the bath. This washing of the coal will
effectually separate from it the fluid matter forming the bath, the presence of
which might act injuriously in some cases in which the coal might be
employed. it also prevents that waste of the fluid which would otherwise take
place by restoring it to the proper degree of density by evaporation or other-
wise; the fluid employed may be filtered from time to time as occasion may
require and fresh portions added. to supply the small but unavoidable waste
which would occur.
When it is desired to have the coal delivered in a dry state, a current of
cold or heated air may be used, or the coal may be dried in a centrifugal
drying apparatus, arranged so as to discharge the dried coal continuously.
It will be understood that the different stages of the process herein-before
described may be carried on independently of each other and in different
localities should it be found expedient to do so and on the other hand, it will
be understood that the entire process herein-before described may be carried
on in one combined apparatus. and thus constitute a continuous self-acting
process. The coal when thus treated and separated from the foreign sub-
stances that were mechanically mixed therewith, may at once be used as
fuel or it may be made into artificial fuel by a partial coking, thereof in taper
or conical wrought-iron retoris. or in other suitable apparatus. the coal being
used alone or mixed in any desirable proportion with coal tar or with pitch
obtained in the distillation of coal tar, and with or without lime, the coking
process not being carried so far to deprive the coal of the property of pro-

page_text: ducing an abundant flame when used in a reverberatory or other furnace where
flame is desirable; or otherwise, the coal when separated from its impurities
in the manner herein-before described may be used alone or mixed in any
desirable proportion with coal tar or pitch, and with or without lime, and he
made into oven coke similar to the usual description. in so far as the amount
of coking is concerned.
It will be found that coal when separated from pyrites and other foreign
matters in the manner herein-before described is especially suitable for the
manufacture of coal gas, and also for those metallurgic operations where
the fuel itself or the products of combustion are brought in contact with the
metal.
Having described my Invention, and in what manner the same may be
carried into effect. I desire it to be understood that I lay no claim to any
special mechanical arrangement or any combination of machinery to be
employed in the process herein-before described: but what I do claim is.-
Firstly, the separation of pure or nearly pure pit coal from shale. carbonate
of lime, silica, and pyrites, or other earthy or mineral substances, and from
coal impregnated or combined therewith, by causing the purer portions of
the coal to float on the surface of a thuid of greater specific gravity than
pure coal, and less than the less pure coal and the substances to be separated
therefrom.
Secondly, claim the washing and separation from purified pit coal and
from the earthy or mineral substances obtained therefrom, of any dense fluid
that may have been employed in the the separation of such coal from mineral or
earthy substances; and also the evaporation of such fluid and its restoration
to that degree of density as will enable it to be again employed in the purifi-
cation of coal.
In witness whereof, I, the said Henry Bessemer, have hereunto set my
hand and seal, this Twenty-eighth day of January, in the year of our
Lord One thousand cirrhi hundred and fifty-nine.
Witness,
S. CARPMAEL.
HENRY BESSEMER. (L.S.)