IMPROVEMENTS IN THE UTILIZATION OF PHOSPHATIC METALLIC
Year: 1883

page_text: LETTERS PATENT to George Pitt of Sutton in the County of Surrey for an
Invention of "IMPROVEMENTS IN THE UTILIZATION OF PHOSPHATIC METALLIC
"
SCORIA communicated to me from abroad by Georges Rocour of Liège
Belgium.
PROVISIONAL SPECIFICATION left by the said George Pitt at the Office of
the Commissioners of Patents on the 6th April 1883.
"
GEORGE PITT of Sutton in the County of Surrey "IMPROVEMENTS IN THE
UTILIZATION OF PHOSPHATIC METALLIC SCORIA [communicated to me from abroad
by Georges Rocour of Liège Belgium.]
Experience of the process for the utilization of phosphatic metallic scoria
described in the Patent N° 299 in the year 1882 has shown that modifications may
be usefully made.
The first part of the process consisting in a reducing fusion of the scoria in a
tank furnace with the object of concentrating the greater part of the phosphorus
of the scoria in a phosphatic matte (or phosphide of manganese and iron) is
retained.
It is important nevertheless to notice that matters should be so arranged that the
fused mass may contain a total weight of iron and manganese at least double but
better treble the weight of the phosphorus which it contains in order that a phosphatic
matte as rich as possible in phosphorus may be obtained whilst limiting the loss of
phosphorus carried off with the gases and the furnace slags.
In order to effect the separation of the phosphorus from these slags the decom-
position of the phosphates should be ensured by maintaining the silica in the slags
at from 30 to 40 per cent of the whole and keeping up the heat of the furnace
sufficiently to reduce all of the iron oxide.
Natural or artificial phosphates may be added to the fused bath so long as its
composition be confined within the limits above indicated.
In practice it has been found that a phosphatic matte may be conveniently
obtained containing 20 to 25 per cent of phosphorus. In this state it presents itself

page_text: after fusion in the form of a blackish mass with metallic lustre and very fragilo
fibrocrystalline structure easy to reduce to fine powder for the subsequent treatment
now to be described.
The attack of this phosphatic matte by acids being very slow and difficult in
place of following the methods indicated in the original Patent, the following is
now preferred.
The phosphatic matte crushed to a fine powder is mixed with a certain quantity
of anhydrous sulphate of soda or of potash also crushed fine (3 to 7 parts of alkaline
sulphate for one of phosphorus contained in the matth). This mixture is then
brought to a red heat in a reverberatory furnace the flame of which is rendered as
little oxidising as possible.
A lively reaction takes place in the whole of the mixed mass, with emission of
heat, a reaction which results in a great part of the phosphorus passing into the
state of phosphate of soda or of potash whilst a part of the iron and manganese
becomes phosphate, sulphide and oxide.
The mass being then withdrawn from the furnace is treated with water to
separate by crystallization from the liquor the phosphate of soda or of potash
which it has dissolved mixed more or less with the excess of sulphate which
successive crystallizations fail to separate.
The insoluble residue if it contains a sufficient proportion of insoluble phosphate
(of iron and manganese) is dried and ground fine and mixed with a further quantity
of sulphate of soda or of potash in relation to the quantity of phosphate of iron it
contains and carbon in powder.
The mixture being then treated at a red heat in a reverberatory furnace with a
reducing flame, the alkaline sulphate becomes sulphide and this latter, under the
influence of as high a temperature as possible aided by the stirring of the mass
transforms the phosphate of iron and manganese into alkaline phosphate and
metallic sulphide.
The cooled mass treated with water yields a further quantity of alkaline
phosphate which is soluble and crystallizable.
The insoluble residue may when it has been heated and oxidized, to drive off
the sulphur be employed or sold as a manganiferous iron mineral. As to the
alkaline phosphate it may be employed or sold for the manufacture of chemical
manure or for other uses in which its alkaline richness and its soluble phosphoric
acid are both useful.
The lixiviation of the mass between the two reverberatory furnace treatments
prescribed above may be omitted so as to have only one final lixiviation yielding
at once the alkaline phosphate. This latter method is more rapid and economical
in the cost of treatment but the reactions being less precise there is a risk of losing
a larger quantity of phosphorus not converted into alkaline phosphate.
In place of alkaline sulphate, caustic soda or potash may be employed if circum-
stances permit or the nitrates of the same bases but the sulphates are generally
more advantageous.
The phosphatic matte may also be treated as follows:-
As it is produced in the cupola or blast furnace or after remelting in the cupola
it is refined pneumatically in a Bessemer converter with a basic lining; from 2 to 4
parts of lime (magnesian or not) being added for each part of phosphorus contained
in the matte. To facilitate the fusion of the phosphatic scoria which forms, a little
alkali may be added and the lime should be put in little by little as the combustion
of the phosphorus proceeds which produces the heat necessary for the fusion into
phosphatic scoria. Lime previously heated is preferable. Before the complete
dephosphorization of the metallic bath the phosphatic scoria is drawn off and more
lime is added to effect the complete dephosphorization of the metal by the Thomas
Gilchrist system as usual. Proceeding thus a phosphatic scoria is obtained
containing relatively but little iron and manganese and a proportion of phosphoric
acid so much the greater as the addition of lime has been smaller and the
temperature higher.

page_text: This scoria constitutes an artificial phosphorite which may be used directly as a
manure after simple grinding or after treatinent by acids as superphosphate.
This second method of treatment of the phosphatic matte yields the phosphorus
in a form of less commercial value than that which results from the treatment by
alkaline sulphates but in certain circumstances the value of the metal of the matte
transformed into steel by the same operation may more than compensate for this
difference.
SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said George Pitt in the Great Seal Patent Office on the 5th October
1883.
"
GEORGE PITT of Sutton in the County of Surrey "IMPROVEMENTS IN THE
UTILIZATION OF PHOSPHATIC METALLIC SCORIA A communication to me from
abroad by Georges Rocour of Liège Belgium
The subject of the present Patent is a process to obtain in a commercial form
the phosphoric acid contained in the metallic slags or cinders produced by the
metallurgical processes (known as the basic process, or Thomas Gilchrist process)
by puddling process; but it can be applied with advantage to other natural or
artificial compounds rather poor in phosphoric acid or containing too much lime,
magnesia, iron or manganese to be treated by acids for superphosphate with
advantage.
The first operation is a fusion of the phosphatic matter containing iron and
manganese or mixed with a sufficient proportion of matter containing those metals
in order to concentrate the phosphorus into a phosphide of iron and manganese
which I name phosphoric matte.
The fusion must be operated in reducing conditions and I prefer to use for that
purpose a cupola or blast furnace, but reverberating or crucible furnaces could also
be used if coal is added to the mixture. The phosphoric matters to be melted
should contain or be mixed with such fluxes, as to contain as a whole about
3 to 4 parts of iron and manganese together for 1 part of phosphorus, and 30 to 50
of silica for 70 to 50 of alumina lime and magnesia together. The fuel should be
coke, anthracite coal or charcoal, and temperature high enough to reduce a large
portion of the manganese oxide contained.
The products of the melting are a phosphoric matte with 20 to 25% of
phosphorus and a slag very poor in phosphoric acid, a small portion of the
phosphorus is volatilized with the gases of the furnaces and could be condensed if
in sufficient quantity.
The phosphoric matte obtained can be treated by one of the following processes,
the economical conditions of the works shall command one or another.
I. The fused phosphoric matte just obtained, or remelted in a cupola, is blown
in a basic converter as ordinary pig iron with additions of 2 to 4 parts of lime or
calcined dolomite for one part of phosphorus in the matte.

page_text: Small quantities of sulphate or carbonate of soda can be added in the converter
to facilitate the fusion of the phosphoric slag produced, and; for the same purpose,
it will be good to make the total additions in several times so that a new
addition can be dissolved in a preexisting slag, floating on the metallic bath, by
the growing temperature produced by the oxidation of the phosphorus by the
blast.
On lowering the converter before complete dephosphorisation of the metal, a
slag very rich in phosphoric acid and rather poor in manganese and iron can be
run, which slag can be utilized as natural phosphorite or treated by sulphuric acid
for superphosphate for agricultural purposes.
After the running of that slag the metal can be completely dephosphorised and
utilised in the usual manner described in former Patents.
II. The phosphoric matto is ground and mixed with 3 to 7 parts of sulphate of
soda or potash for 1 part of phosphorus in the matte and about ½ part of coal
or coke.
The whole mixture being ground is heated to redness in a reverberatory furnace
first by a reducing flame and then the mass is retained under an oxidising flame
and temperature raised as high as possible.
By that treatment the phosphorus of the matte is oxidised and transformed
into phosphate of soda or potass, part of iron and manganese become oxide and
part sulphide.
It can be found useful in order to facilitate reactions to add to the mixture
heated in the reverberatory furnace 10 to 12 parts of sulphur or rather 40 to 42
parts of iron pyrites for 100 parts of phosphorus in the matte.
The mass cooled is then lixiviated, and the phosphate of soda or potass
obtained in solution can be crystallized and sold in that form for chemical
manure, in which shall be found in any case all the phosphoric acid contained (all
soluble) and all the potass when sulphate of potass has been used.
When sulphate of soda has been used the solution of phosphate can be
precipitated by lime into the state of commercial precipitate phosphate of calcium,
and the liquid concentrated by evaporation gives caustic soda marketable.
If an excess of sulphato has been used in the initial mixture of the matte the
correspondent alkali shall be found as sulphide in the solution' where phosphate has
been crystallized. That sulphide evaporated to dryness can be used instead of a
part of sulphate and coal in the mixture for another operation, or treated by the
known processes for caustic alkali.
The insoluble residue of lixiviation can be roasted to climinate sulphur and gives
then a purple ore to be melted for pig iron.
Having thus described the nature of the said Invention and the manner in which
it is to be performed I claim-'
First. The process and method of utilising phosphatic cinders or slags by melting
them with convenient fluxes and fuel in cupola, blast furnace or other reducing
furnace to obtain a phosphorus matte" containing the phosphorus iron and
manganese of the cinders or slags.
Second. The method of transforming the phosphorus of the matte into alkaline
phosphate soluble by heating in a reverberatory or other furnace the ground
phosphorus matte mixed with sulphate of sodium or potassium and coal in powder
with or without sulphur or pyrites.
In witness whereof I the said George Pitt have hereunto set my hand and seal
this fourth day of October in the year of our Lord One thousand eight hundred
and eighty three.