IMPROVEMENTS IN THE UTILIZATION OF PHOSPHATIC METALLIC SLAGS
Year: 1882

page_text: LETTERS PATENT to Sydney Pitt, of Sutton, in the County of Surrey, for an
Invention of "IMPROVEMENTS IN THE UTILIZATION OF PHOSPHATIC METALLIC
SLAGS." A communication from abroad by Georges Rocour, of Liége,
Belgium.
PROVISIONAL SPECIFICATION left by the said Sydney Pitt at the Office
"
of the Commissioners of Patents on the 20th January 1882.
SYDNEY PITT of Sutton in the County of Surrey. "IMPROVEMENTS IN THE
UTILIZATION OF PHOSPHATIC METALLIC SLAGS." [A communication from abroad
by Georges Rocour of Liége Belgium.]
This Invention has for its object improvements in the utilization of phosphatic
metallic slags by extracting from them in a commercial form the metallic oxides
and phosphoric acid which they contain.
This process is especially applicable to the treatment of the slags produced in
dephosphorizing iron either in a Bessemer converter or in a reverberatory furnace
by the Thomas-Gilchrist process or in puddling and reheating furnaces.
The first operation consists of a reducing melting conducted by preference in a
tank furnace, a cupola or a blast furnace, with a view of concentrating into a
phosphatic matt almost all of the iron, the manganese and the phosphorus of the
slag.
In order best to attain this end the slags are assorted so as to insure the
decomposition of the phosphate of lime which they may contain by a suitable
proportion of silica by forming a slag containing about 30 to 40 per cent of silica
or else silicious matters are added so as to realize these conditions.
When circumstances render it economical it is found advantageous to introduce
the silica necessary for the treatment of the basic slags of dephosphorization (which
contain an excess of lime) by putting puddling slags (which contain an excess of
silica) into the melting bath.
It is advantageous to charge the slags in as finely divided a state as possible so
as to stop the reduction of the metals and phosphoric acid, this state of division
can often be obtained with advantage by granulating the melted slags in water.
•
The tank furnace should be kept very hot during working so as to insure the

page_text: reduction of the phosphoric acid, and the manganese as in the manufacture of
ferro-manganese.
The phosphatic matt obtained is run into masses as small as possible or better
still is granulated in water so as to facilitate its ulterior treatment by the wet
process.
This matt is then treated with sulphuric or hydrochloric acid in receptacles as
little attackable by these acids as possible (stone, brick, earthenware, wood, lead
with the joints coated or impregnated with tar or resin) under the best condition
of pressure and temperature which experience determines, a steain jet allowing the
temperature to be raised at will and even the pressure by working in a closed
vessel. In the latter case the receptacle should be of iron lined with the
unattackable materials indicated above.
The attack of the matt by the acids gives rise to a disengagement of hydrogen
gas and phosphoretted hydrogen which are conducted by a pipe to a series of burners
placed so as to heat a small reverberatory or combustion furnace. At the end of
this furnace is a chimney leading into the top of a condensing column formed of
descending pipes cooled on the outside by water or the surrounding air or by a
spray inside.
The hydrogen gas and the phosphoretted hydrogen burn producing steam and
phosphoric acid which are drawn into the condensing column and are collected at
the bottom in the form of aqueous solution of phosphoric acid. This solution is
concentrated by evaporation and the phosphoric acid so obtained forms a commercial
product of great value.
The matt dissolved by the acids gives rise to a solution of chloride or sulphate
of iron and manganese more or less pure which may contain in the form of acid
phosphate a greater or less proportion of phosphorus according to the more or less
oxidising condition which existed during the attack of the matt.
If the solution was made with hydrochloric acid the iron and manganese are
precipitated either together or separately in the state of oxide simply by the
addition of lime in excess or a measured quantity of carbonate of lime (chalk) may
first be added.
In place of lime it is found advantageous to employ basic slags finely ground
containing an excess of lime. Under these conditions the oxides of iron and
manganese and the phosphoric acid of these slags are added to the precipitated
oxide and phosphate of iron and thus avoid the cost of concentration of the
corresponding matt.
The phosphoric acid is precipitated in the state of basic phosphate of iron
accompanied by the oxide of that metal.
To effect the separation of these two products and to obtain directly the phos-
phoric acid in a convenient form for chemical manures the ferro-phosphate precipitate
is mixed with commercial sulphate of potass and the mixture is calcined to a red
heat in a reverberatory furnace. The calcined mass is then treated with water,
which leaves an insoluble, residue of oxide of iron and dissolves the phosphate of
potass which is easily separable by evaporation or crystalization.
The phosphate of potass thus obtained constitutes a new commercial product
applicable directly as a manure with or without mixture with lime or other
substance or manure or saleable to manufacturers of chemical manures according to
the proportions of its two elements phosphoric acid and potass.
If under certain circumstances it is judged to be preferable to produce the
phosphoric acid in the form of precipitated phosphate of lime it suffices to add
lime to the phosphate of potass and to evaporate to dryness the decanted or
precipitated solution so as to obtain the potass in the caustic state.
Sulphate of soda may in the last case be substituted for sulphate of potass.
The precipitates of the oxides of iron and manganese obtained mixed or separate
as has been described above are sold to manufacturies producing iron or spiegel-
eisen or ferro-manganese for well known uses (glass for painting, iron minium,
rouge for polishing, glass makers soap, linings for puddling furnaces &c. &c.)

page_text: If sulphuric acid is used for the solution of the matt, then the greater part of the
phosphorus will be obtained in the form of phosphoric acid and the solution will
only contain a proportion too small to justify the cost of a special treatment to
separate it.
A part of the iron can then be obtained either by crystallization in the state of
sulphate (green copperas of commerce) or the two sulphates of iron and manganese
obtained by evaporation to dryness may be decomposed by heat by calcining them
in a closed vessel communicating with a suitable condensing apparatus as in the
Nordhausen manufacture of sulphuric acid or in a reverberatory furnace or muffle
communicating with lead chambers thus recovering the acid used in the treatment
of the phosphatic matt
The local economical conditions as to the price of the acids and the value of
products obtained will determine which of the above described methods is to be
fanned

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
'
by the said Sydney Pitt in the Great Seal Patent Office on the 19th July
1882.
SYDNEY PITT of Sutton in the County of Surrey. "IMPROVEMENTS IN THE
UTILIZATION OF PHOSPHATIC METALLIC SLAGS." A communication from abroad
by Georges Recour of Liege Belgium.
This Invention has for its object improvements in the utilization of phosphatic
metallic slags by extracting from them in a commercial form the metallic oxides
and phosphoric acid which they contain. This process is specially applicable to
the treatment of the slags produced in dephosphorizing iron either in a Bessemer
converter or in a reverberatory furnace by the Thomas-Gilchrist process or in
puddling and reheating furnaces.
The first operation consists of a reducing melting conducted by preference in
a tank furnace a cupola or a blast furnace with a view of concentrating into a
phosphatic matt almost all of the iron the manganese and the phosphorus of
the slag.
In order best to attain this end the slags are assorted so as to ensure the decom-
position of the phosphate of lime which they may contain by a suitable proportion
of silica forming a slag.containing about 30 to 40 per cent. of silica or else
silicious matters are added so as to realize these conditions. When circumstances
render it economical it is found advantageous to introduce the silica necessary
for the treatment of the basic slags of dephosphorization (which contain an excess
of lime) by putting puddling slags (which contain an excess of silica) into the
melting bath.
It is advantageous to charge the slags in as finely divided a state as possible
so as to determine the reduction of the metals and phosphoric acid--this state
of division can often be obtained with advantage by granulating the melted slags
in water.
The tank furnace should be kept very hot during working so as to insure the
reduction of the phosphoric acid and the manganese as in the manufacture of
ferro-manganese or manganetic iron. The phosphatic matt obtained is run into
masses as small as possible or better still is granulated in water so as to facilitate
its ulterior treatment by wet process.
This matt is then treated with sulphuric or hydrochloric acid in receptacles as
little attackable by these acids as possible (stone, brick, earthenware, wood, lead,
with the joints coated or impregnated with tar or resin) under the best conditions
of pressure and temperature which experience determines, a steam jet allowing the
temperature to be raised at will and even the pressure by working in a closed
vessel. In the latter case the receptacle should be of iron lined with the
unattackable materials indicated above.
The attack of the matt by the acids gives rise to a disengagement of hydrogen
gas and phosphoretted bydrogen which are conducted by a pipe to a series of
burners placed so as to heat a small reverberatory or combustion furnace. At the
end of this furnace is a chimney leading into the top of a condensing column
formed of descending pipes cooled on the outside by water, or the surrounding air
or by a spray inside.
The hydrogen gas and the phosphoretted hydrogen burn producing steam and
phosphoric acid which are drawn into the condensing column and are collected at
the bottom in the form of aqueous solution of phosphoric acid. This solution is
concentrated by evaporation and the phosphoric acid so obtained forms a
commercial product of great value suitable for the manufacture of phosphorus for
matches &c. a product which at present is only known in laboratories.

page_text: The matt dissolved by the acids gives rise to a solution of chloride or sulphate
of iron and manganese more or less pure and which may contain in the form of
acid phosphate a greater or less proportion of phosphorus according to the more
or less oxidizing conditions which existed during the attack of the matt.
If the solution was made with hydrochloric acid the iron and manganese
are precipitated either together or separately in the state of oxide simply by the
addition of lime in excess or a measured quantity of carbonate of lime (chalk) may
first be added..
In place of lime it is found advantageous to employ when available basic
refinery slags finely ground and containing an excess of lime. Under these
conditions the oxides of iron and manganese and the phosphoric acid of these slags
are added to the precipitated oxide and phosphate of iron and thus avoid the cost
of concentration of the corresponding matt.
The phosphoric acid is precipitated in the state of basic phosphate of iron
accompanied by the oxide of that metal.
.
To effect the separation of these two products and to obtain directly the
phosphoric acid in a convenient form for chemical manures, the ferro phosphate
precipitate is mixed with commercial sulphate of potass and the mixture is
calcined to a red heat in a reverberatory furnace. The calcined mass is then
treated with water which leaves an insoluble residue of oxide of iron and
dissolves the phosphate of potass which is easily separable by evaporation or
crystallization.
The phosphate of potass thus obtained constitutes a new commercial product
applicable directly as a manure with or without mixture with lime or other
substance or manure or saleable to manufacturers of chemical manures according
to the proportions of its two elements phosphoric acid and potass.
If under certain circumstances it is judged to be preferable to produce the
phosphoric acid in the form of precipitated phosphate of lime it suffices to add lime
to the phosphate of potass and to evaporate to dryness the decanted or precipitated
solution so as to obtain the potass in the caustic state.
Sulphate of soda may in the last case be substituted for sulphate of potass.
The precipitates of the oxides of iron and manganese obtained inixed or separate
as has been described above are sold to manufacturers producing iron or
speigel-eisen or ferro manganese for well known uses-(glass for painting, iron
minium rouge for polishing, glass makers' soap, linings for puddling furnaces,
&c. &c.)
If sulphuric acid has been used for the solution of the matt-then the greater
part of the phosphorus will have been obtained in the form of phosphoric acid and
the solution will only contain a proportion too small to justify the cost of a special
treatment to separate it.
A part of the iron can then be obtained either by crystallization in the state of
sulphate (green copperas of commerce) or the two sulphates of iron and manganese
obtained by evaporation to dryness may be decomposed by heat by calcining them
in a closed vessel communicating with a suitable condensing apparatus as in the
Nordhausen manufacture of sulphuric acid or in a reverberatory or muffle furnace
communicating with lead chambers thus recovering the acid used in the treatment
of the phosphatic matt.
The local economical conditions as to the price of the acids and the value of
products obtained will determine which of the above described methods is to be
preferred.
The decomposition of the granulated or pulverised matt of phosphoretic iron
can also be effected by a current of superheated steam, or of hydrochloric acid
gas or of gaseous chlorine-In this latter case the chloride of phosphorus
produced is decomposed by water ultimately into phosphoric acid and hydrochloric
acid which is separated by evaporation or distillation the phosphoric acid remaining
fixed.

page_text: Having thus described the nature of the said Invention and the manner of
performing the same I would have it understood that I claim
First. The processes above described for the utilization of phosphatic metallic
slags, consisting in concentrating them into a matt and then treating them by
humid process substantially as described.
Second. The method of obtaining phosphoric acid and phosphate of potassa by.
the combustion of hydrogen phosphide substantially as described.
Third, The employment substantially as described of basic slag in place of lime
to precipitate acid phosphatic solutions of iron and of manganese.
In witness whereof I the said Sydney Pitt have hereunto set my hand and
seal this nineteenth day of July One thousand eight hundred and
eighty two.