IMPROVED PROCESSES AND APPARATUS FOR ENRICHING PHOSPHATES OF LIME BY THE SEPARATION OF CARBONATE OF LIME FROM THEIR GANGUE
Year: 1879

page_text: LETTERS PATENT to William Robert Lake, of the Firm of Haseltine, Lake,
& Co., Patent Agents, Southampton Buildings, London, for the Invention of
"IMPROVED PROCESSES AND APPARATUS FOR ENRICHING PHOSPHATES OF
LIME BY THE SEPARATION OF CARBONATE OF LIME FROM THEIR GANGUE."
A communication from abroad by Charles de la Roche, of Paris, France.
PROVISIONAL SPECIFICATION left by the said William Robert Lako at
the Office of the Commissioners of Patents on the 15th January 1879.
WILLIAM ROBERT LAKE, of the Firm of Haseltine, Lake, & Co., Patent Agents,
Southampton Buildings, London. " IMPROVED PROCESSES AND APPARATUS FOR
ENRICHING PHOSPHATES OF LIME BY THE SEPARATION OF CARBONATE OF LIME
FROM THEIR GANGUE" [A communication from abroad by Charles de la Roche,
of Paris, France.]
This Invention relates to improved processes and apparatus for enriching
phosphates of lime.
The phosphates generally employed in the manufacture of superphosphate of
lime contain from 60 to 70 per cent. of tri-basic phosphate of lime.
The phosphates worked on a large scale for the purposes of agriculture contain
for the most part too small a proportion of phosphate and too large a proportion of
carbonate of lime to be transformed into superphosphates. It has not been possible
heretofore to remove by mechanical means the carbonated gangue with which they
are intimately mixed. The chemical process employed for the same purpose consist
not only in dissolving the carbonate of lime but also the phosphate of lime with
the object of preparing a precipitated phosphate as is done for the phosphate of
bone. By this method a mixture of phosphate of lime, of hydrate of lime, and of
chloride of calcium is obtained; that is to say, an impure phosphate, of which the
cost of production is very high. These phosphates, known in commerce under the
name of precipitated phosphates, are mixed with azotic substances for the manu-
facture of manure; they cannot be treated economically for transformation into
superphosphates.
The process to which this Invention relates consists in separating the carbonate
of lime from the gangue without attacking the phosphate of lime. When a natural
phosphate containing from 35 to 40 per cent. of phosphate of lime and 34 to 38 per
cent. of carbonate of lime is heated to a high temperature under the influence of
steam a mixture of phosphate of lime and of quicklime is obtained. By the inter-

page_text: vention of steam the decarbonization is complete and the product no longer
effervesced in the least with the acids. In order to separate the lime from such a
mixture I make use of hydrochloric acid or of diluted pyroligneous acid in sufficient
quantity to avoid all dissolution of the phosphate. The chloride of calcium or the
pyrolignite of lime which then moistens the insoluble phosphate is carried off by
prolonged washings. The phosphate resulting from this treatment is exclusively
composed of a mixture of phosphate of lime and of clayey silicious gangue.
This
new phosphate can be used directly without previous desiccation for the manufacture
of the superphosphate with sulphuric acid from the chambers at 53°. Under these
circumstances all the mixed sulphuric acid is employed usefully without waste since
there is no more carbonate of lime to be attacked at the same time as the
phosphate.
The phosphate thus enriched and dried is not only deprived of carbonate of lime
but also of its constituent water which it has lost at a high temperature. Thus
with Southern rock phosphate of the following composition, that is to say,-
Carbonate of lime, 34,
Phosphate of lime, 36,
I obtain a phosphate which after desiccation contains 75 per cent. of phosphate of
lime.
This method of enrichment is not only applicable to the poor phosphates known
as phosphates of the second quality but also to the rich carbonated phosphates,
which may thus produce from 75 to 90 per cent. of phosphate of lime.
Phosphates of granitic origin stated to contain from 80 to 90 per cent. of phosphate
of lime have been recently imported from Canada and from Norway. Theso
phosphates coming from a depth although relatively rich are very difficult to attack
by sulphuric acid, and even by means of that acid can only yield phosphates which
are not very assimilable.
The phosphates enriched by the process to which this Invention relates yields
superphosphates, the agricultural value of which is considerable, since all the
phosphates may be brought to the state of superphosphate completely soluble in
water, and consequently very assimilable.
In order to effect the removal of the carbonic acid by the aid of superheated steam
I employ a furnace which avoids the necessity of using a steam generator, but this
is not absolutely necessary except for the treatment of certain phosphates. I may
substitute for steam a simple current of hot air in order to effect the elimination of
the carbonic acid.
In the accompanying Drawing I have represented as a specimen a furnace con-
structed according to this Invention.
A is the receiver containing the water; B is the water conduit; E is the cylin-
drical part of the furnace containing the phosphate; H is the passage reserved for
the flame from the fire; O is the opening through which the part E is filled; R is
the fire grate; C is a cap of refractory material for preventing the phosphate from
stopping up the orifice K of the water conduit B; D, D, are holes cut in the cap C
for the passage of the steam; F is the door of the furnace S; L is a man hole to
permit the removal of the calcined matters from the crucible or cylindrical part E of
the furnace; a, b, represents the constant level of the water in the pipe B.
The pipe B containing the water to be evaporated is arranged for the half of its
height in the furnace above the fire-grate. The flame from the fire causes this part
of the pipe to become red hot, and the water in contact evaporates, passes through
the orifices D, and fills up the part E of the furnace which contains the phosphate
calcined by the flame from the fire-place S which surround it at its lower part as
well as in the part H, thence the superheated steam traverses the mass of phosphate
arrives at the orifice O, and carries with it into the suction pipes the carbonic acid
obtained during the operation. To obtain a greater volume of steam or a stronger
pressure it is only necessary to raise suddenly the level a, b, of the water in the
conduit B.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said William Robert Lake in the Great Seal Patent Office on the 15th July
1879.
WILLIAM ROBERT LAKE, of the Firm of Haseltine, Lake, & Co., Patent Agents,
Southampton Buildings, London. "IMPROVED PROCESSES AND APPARATUS FOR
ENRICHING PHOSPHATES OF LIME BY THE SEPARATION OF CARBONATE of Lime
FROM THEIR GANGUE” A communication from abroad by Charles de la Roche, of
Paris, France.
This Invention relates to improved processes and apparatus for enriching
phosphates of lime. The phosphates generally employed in the manufacture of
superphosphate of lime contain according to chemical analysis from 60 to 70 per
cent. of tribasic phosphate lime.
The phosphates worked on a large scale for agricultural purposes contain for the
most part too small a proportion of phosphate and too large a proportion of carbonate
of lime to be transformed into superphosphates. It has not been practicable hereto-
fore to remove by mechanical means the carbonated gangue with which they are
intimately mixed. The chemical processes employed for the same purpose not only
dissolve the carbonate of lime but also the phosphate of lime with the object of
preparing a precipitated phosphate as for the phosphate of bone. By this method
a mixture of phosphate of lime, hydrate of lime, and chloride of calcium is obtained,
that is to say, an impure phosphate, of which the cost of production is very high.
These phosphates, known in commerce under the name of precipitated phosphates,
are mixed with azotic substances for the manufacture of manure; they cannot be
treated economically for transformation into superphosphates.
The process to which this Invention relates consists in separating the carbonate
of lime from the gangue without attacking the phosphate of lime. When a natural
phosphate containing from 35 to 40 per cent. of phosphate of lime and 34 to 38 per
cent. of carbonate of lime is heated to a high temperature in the presence of steam,
a mixture of phosphate of lime and quicklime is obtained. By the intervention of
steam the decarbonization is complete and the product no longer effervesces in the
least with the acids. In order to separate the line from such a mixture I make use
of hydrochloric acid or of diluted pyroligneous acid in sufficient quantity to prevent
any dissolution of the phosphate. The chloride of calcium or the pyrolignite of
lime which then inoistens the insoluble phosphate is carried off by prolonged
washings. The phosphate resulting from this treatment is exclusively composed of
a mixture of phosphate of lime and of clayey-silicious gangue. This new phosphate
can be used directly without previous desiccation for the manufacture of the super-
phosphate with sulphuric acid from the chambers at 53°. Under these conditions
all the mixed sulphuric acid is employed usefully without waste since there is no
more carbonate of lime to be attacked at the same time as the phosphate.
The phosphate thus enriched and dried is not only deprived of carbonate of lime
but also of its constituent water which it has lost at a high temperature. Thus
with a rock phosphate of the following composition, that is to say,-
Carbonate of lime, 34 per cent., and
Phosphate of lime, 36 per cent.
I obtain a phosphate which after desiccation contains 75 per cent. of phosphate of
lime.
This method of enrichment is not only applicable to the poor phosphates known
as phosphates of the second quality but also to the rich carbonated phosphates,
which may thus produce from 75 to 90 per cent. of phosphate of lime.
Phosphates of granitic origin and stated to contain from 80 to 90 per cent. of
phosphate of lime have been recently imported from Canada and from Norway,
These phosphates although relatively rich are very difficult to attack by sulphuric

page_text: acid, and even by means of this acid can only be made to yield phosphates which
are very slightly assimilable.
But the phosphates enriched by the process to which this Invention relates yield
superphosphates, the agricultural value of which is considerable, since all of tho
phosphate may be brought to the condition of a superphosphate completely soluble
in water, and consequently very assimilable.
In order to effect the removal of the carbonic acid by the aid of superheated
steam employ a furnace which obviates the necessity of using a steam generator,
but this treatment is not absolutely necessary except for the treatment of certain
phosphates. I may substitute for steam a simple current of hot air in order to
effect the elimination of the carbonic acid.
In the accompanying Drawing I have represented in vertical section as an
example a furnace constructed according to this Invention.
A is the receiver containing the water; B is the water conduit; E is the central
part of the furnace containing the phosphate; H is the passage for the flame from
the fire; O is the opening through which the furnace E is filled; R is the furnace
grate; C is a cap of refractory material for preventing the stoppage of the orifice K
of the water conduit B by the phosphate; D, D, are holes formed in the cap C for
the passage of the steam; F is the door of the furnace S; L is a manhole to permit
the removal of the calcined matters from the crucible or cylindrical part of the
furnace E; a, b, indicate the level of the water in the pipe B.
The pipe B containing the water to be evaportated lins its upper half or part in
the furnace above the fire-grate R. The flame from the fire causes this part of the
pipe to become red hot, consequently the water in contact therewith evaporates,
passes through the orifices D, and fills the part E of the furnace which contains the
phosphate calcined by the flame from the fire place S which surrounds it at its
lower part as well as in the part H, thence the superheated steam traverses the
mass of phosphate, arrives at the orifice O, and carries with it into the suction
pipes the carbonic acid obtained during the operation. To obtain a greater volume
of steam on a stronger pressure it is only necessary to raise suddenly the level a, b,
of tho water in the conduit B.
Having thus fully described the said Invention as communicated to me by my
foreign correspondent, and the manner of performing the same, I wish it understood
that I claim,-
The novel process above specified and the apparatus as described and shown in
the accompanying Drawing for the purpose set forth.
In witness whereof, I, the said William Robert Lake, have hereunto set
my hand and seal, this Fifteenth day of July, in the year of our Lord One
thousand eight hundred and seventy-nine.
DOD
TR
L
W. ROB LAKE. (S.)