IMPROVEMENTS IN AND IN FURNACES FOR REFINING IRON
Year: 1881

page_text: LETTERS PATENT to Alexander Melville Clark, of 53, Chancery Lane, in the
County of Middlesex, Patent Agent, for an Invention of "IMPROVEMENTS IN
AND IN FURNACES FOR REFINING IRON." A communication from abroad by
Jules Garnier, of Paris, France.
PROVISIONAL SPECIFICATION left by the said Alexander Melville Clark
at the Office of the Commissioners of Patents on the 9th November 1881.
ALEXANDER MELVILLE CLARK, of 53, Chancery Lane, in the County of
Middlesex, Patent Agent. "IMPROVEMENTS IN AND IN FURNACES FOR REFINING
IRON." [A communication from abroad by Jules Garnier, of Paris, France.]
This Invention relates to a process of refining pig iron and scrap iron containing
phosphorus upon a neutral or basic hearth by the employment of a false bearth
of limestone, which is oxidising and basic, and acts moreover mechanically.
In carrying out the Invention I operate in any suitable furnace at a high
temperature and having either a fixed or rotary permanent hearth, which may
either be basic and made of lime, calcined dolomite, or magnesia, and the like, or
Deutral and made of alumina sesquioxide of chromium, silicate of zinc, and the
like.
At each operation for steel I provide the furnace with a false hearth, which is
intended to act both chemically and mechanically on the metal to be dephosphorised.
This false hearth is composed first of a bed of raw limestone, which is shovelled on
to the permanent hearth and levelled. The quantity of the limestone is proportionate
to the weight of the metal to be treated, and to the impurities such as phosphorus
and silicon to be eliminated therefrom. In order to promote the oxidising action
upon the bath of metal and retard the decomposition of the limestone into its
gaseous and solid elements (although this is not absolutely necessary), I cover the
limestone with a thin layer of iron ore as rich and calcareous as possible.
If the charge is solid metal the charge of pig or scrap iron is piled on the false
hearth without further preparation, but if the charge of cast iron is run in liquid,
I first frit the surface of the false hearth in order to prevent its elements rising

page_text: immediately to the surface of the bath. In either case the limestone is decomposed
into its two elements (carbonic acid and bases) after the cast iron is more or less
in a state of fusion. The carbonic acid which is disengaged in abundance expanded
by the high temperature of the furnace has a considerable volume. It traverses
the at first pasty and afterwards liquid bath of cast iron, which it oxidises rapidly
and becomes itself converted into carbonic oxide which burns at the surface. The
ore is also reduced to its lowest degree of oxidation in presence of the more
combustible elements of the bath. The clements of the false hearth are reduced to
bases consisting principally of lime and protoxide of iron which rise slowly through
the mass of metal, which becomes more and more liquid. During their passage
through the bath they combine with the phosphoric and silicic acids, formed so
that the scoria which floats on the surface contains the greater part of the
impurities of the metal. At this moment the manganiferous cast iron may be
added and the furnace tapped.
If it is desired to carry the purification of the bath still further, it must be
submitted to a second oxidising operation, which will act more especially on the
remaining phosphorus and silicon. One method of oxidising the bath consists in
poling" it with a pole of green wood, which causes an ebullition and an oxidation
of the drops of metal. I may also skim off the scoria and add manganiferous cast
iron, which causes an energetic boiling and consequently an oxidising action.
Lastly, I add to the bath lime or other powerful bases, which combine with the
phosphoric and silicic acids formed.
I would remark_that_the_addition_of_ferro_manganese, contrary_to_what_takes_
place in the basic Bessemer process, does not reintroduce phosphorus into the bath,
and it is therefore unnecessary to skim if a merchantable inetal for rails, sheet iron,
angle irons, &c., is to be produced.
This process is also suitable for pig irons, which are very silicious and contain
little or no phosphorus, provided that the weight and nature of the false hearth
are regulated by calculation and experience, according to the proportion of
impurities to be eliminated.
This process is more rapid than the ordinary processes on the hearth in
consequence of the great disengagement of carbonic acid; the products are softer,
being less silicious, and the fact that the addition of manganese does not reintroduce
phosphorus, permits of the employment of fine metal, but slightly manganiferous
for the final charge.
This Invention also relates to the construction of the furnace when the
permanent hearth is stationary. If the hearth be basic and constructed of lime or
calcined dolomite in the form of bricks or pise work, I carry it up as high only as
the level of the surface of the bath, and at this point I superpose a course of bricks
of bauxite or pure magnesia, and upon this I build up the remaining courses and
the arch of ordinary silica bricks. The alumina and the pure magnesia do not
combine with one another at the temperature of the furnace, nor with the silica,
nor with the lime or the calcined dolomite, and therefore this construction of
furnace is both practical and economical.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by.
the said Alexander Melville Clark in the Great Seal Patent Office on the
8th May 1882.
ALEXANDER MELVILLE CLARK, of 53, Chancery Lane, in the County of
Middlesex, Patent Agent. "IMPROVEMENTS IN AND IN FURNACES FOR REFINING
IRON." A communication from abroad by Jules Garnier, of Paris, France.
This Invention relates to a process of refining pig iron and scrap iron containing
phosphorus upon a neutral or basic hearth by the employment of a false hearth of
limestone, which is oxidising and basic and acts moreover mechanically.
In carrying out the Invention I operate in any suitable furnace at a high
temperature and having either a fixed or rotary permanent hearth, which may either
be basic and made of lime, calcined dolomite, or magnesia, and the like, or neutral
and made of alumina, sesquioxide of chromium, silicate of zinc, and the like.
At each operation for steel I provide the furnace with a false hearth, which is
intended to act both chemically and mechanically on the metal to be dephosphorised.
This false hearth is composed first of a bed of raw limestone which is shovelled
onto the permanent hearth and levelled. The quantity of the limestone is propor-
tionate to the weight of the metal to be treated, and to the impurities such as
phosphorus and silicon to be eliminated therefrom. In order to promote the
oxidising action upon the bath of metal and retard the decomposition of the lime-
stone into its gaseous and solid elements (although this is not absolutely necessary)
I cover the limestone with a thin layer of iron ore as rich and calcareous as
possible.
If the charge is solid metal the pig and scrap iron is piled on the false hearth
without further preparation, but if the charge of cast iron is run in inolten, I first.
frit the surface of the false hearth in order to prevent its elements rising
immediately to the surface of the bath. In either case the limestone is decomposed
into its two elements (carbonic acid and bases) after the cast iron is more or less in
a state of fusion. The carbonic acid which is disengaged in abundance, expanded
by the high temperature of the furnace, has a considerable volume. It traverses
the at first pasty and afterwards liquid bath of cast iron which it oxidises rapidly,
and becomes itself converted into carbonic oxide which burns at the surface. The
ore is also reduced to its lowest degree of oxidation in presence of the more com-
bustible elements of the bath. The elements of the false hearth are now reduced
to bases consisting principally of lime and protoxide of iron which rise slowly
through the mass of metal which becomes more and more liquid, and during their
passage through the bath they combine with the phosphoric and silicic acids formed,
so that the scoria which floats on the surface contains the greater part of the
impurities of the metal. At this moment the manganiferous cast iron may be
added and the furnace tapped. If it is desired to carry the purification of the bath
still further, it must be submitted to a secoud oxidising operation which will act
more especially on the remaining phosphorus and silicon. One method of oxidising
the bath consists in "poling it with a pole of green wood which causes an
ebullition and an oxidation of the drops of inetal. I may also skim off the scoria
and add manganiferous cast iron which causes an energetic boiling and consequently
an oxidising action. Lastly, I add to the bath lime or other powerful bases which
combine with the phosphoric and silicic acids formed.
I would remark that the addition of ferro manganese, contrary to what takes
place in the basic Bessemer process, does not reintroduce phosphorus into the bath,
and it is therefore unnecessary to skim if a merchantable metal for rails, sheet iron,
angle irons, &c., is to be preduced.

page_text: This process is also suitable for pig irons which are very silicious and contain
little or no phosphorus provided that the weight and nature of the false hearth are
regulated by calculation and experience according to the proportion of impurities
to be eliminated. This process is more rapid than the ordinary processes on the
hearth in consequence of the great disengagement of carbonic acid; the products
are softer being less silicious, and the fact that the addition of manganese does not
reintroduce phosphorus permits of the employment of fine metal but slightly
manganiferous for the final charge.
This Invention also relates to the construction of the furnace when the
permanent hearth is stationary. If the hearth be basic and constructed of lime or
calcined dolomite in the form of bricks or pisé work, I carry it up as high as the
level of the surface of the bath and interpose a course of bricks of bauxite or puro
magnesia at this point, the remaining courses and the arch being built up of
ordinary silica bricks. It is indeed preferable to carry up the basic hearth about
as high as the springing of the arch and to interpose the course of bauxite or pure
magnesia bricks at this point in order to avoid, when relining the hearth with basic
materials, the contact of the latter with the silica bricks and the consequent
melting of the latter. The alumina and the pure magnesia do not combine with
one another at the temperature of the furnace, nor with the silica, nor with the
lime or the calcined dolomite, and therefore this construction of furnace is both
practical and economical.
Having described the nature of the said Invention and the manner of performing
the same, I declare that what I claim as the Invention to be protected by tho
hereinbefore in part recited-Letters Patent is,
1st. The employment upon a stationary or rotary permanent hearth, whether
basic or neutral, of a false hearth formed of carbonates of earthy metals and
peroxide of iron, the said false hearth being oxidising and basic and acting also
mechanically on the bath of molten cast iron by the evolution of carbonic acid gas,
substantially as and for the purposes specified.
2nd. In the construction of basic furnaces in which the permanent hearth is
stationary, the interposing a course of bauxite (alumina) or pure magnesia bricks at
the level of the bath of metal or at the springing of the arch in order to separate
the basic material of the hearth from the silica of the upper part of the furnace as.
described, and enable the furnace to be readily and economically constructed.
In witness whereof, I, the said Alexander Melville Clark, have hereunto set
my hand and seal, this Eighth day of May, A.D. 1882.
A M CLARK (L.S.)