An Improved Method chiefly designed for Enriching Calcareous Phosphates and for Manufacturing Superphosphates and Various Bye-products.
Year: 1891

page_text: Date of Application, 25th Mar., 1891
Complete Specification Left, 24th Dec., 1891-Accepted, 25th Mar., 1892
PROVISIONAL SPECIFICATION.
[Communicated from abroad by ALPHONSE BRIART, of Morlanwelz, Engineer,
and PAULIN JACQUEMIN, of Chapelle lez Herliamont, Chemist, both in the
Kingdom of Belgium.]
An Improved Method chiefly designed for Enriching Calcareous
Phosphates and for Manufacturing Superphosphates and Various
Bye-products.
I, HENRY HARRIS LAKE, of the firm of Haseltine Lake & Co., Patent Agents,
45 Southampton Buildings in the County of Middlesex do hereby declare the
nature of this invention to be as follows:-
This invention relates to a method which is chiefly designed for enriching
calcareous phosphates, and for manufacturing superphosphates and various bye-
products.
Its fundamental idea consists in utilizing the grouping of certain modes of
manufacture giving rise to the production of sulphurous acid for causing the
latter by means of special methods to react upon comparatively poor calcareous
phosphate ores, from which it removes a more or less considerable part of carbonate
of lime.
Sulphites and bisulphites of lime result from this reaction and the ore is enriched
proportionally to the quantity of carbonate thus transformed.
The principal modes of manufacture giving rise to the production of sulphurous
acid are the treatment of various metals, such as iron, copper, zinc, by concentrated
sulphuric acid for obtaining sulphate therefrom, the combustion or roasting of
sulphides of iron, copper, lead, zinc and the like for the manufacture of sulphuric
acid or for the extraction of these various metals; the treatment of ores of sulphur
which consists in burning part of the sulphur for extracting the rest; and the com-
bustion of the same ores.
When put in presence of poor calcareous phosphates the sulphurous acid acts
upon the carbonate of lime, expels the carbonic acid, but under certain special con-
ditions attacks only very slowly the phosphate itself.
This is the
From this results a neutral sulphite of lime which by means of an excess of acid
is transformed into a soluble bisulphite which can be easily decanted having the
enriched phosphate in an undissolved state.
The sulphurous acid must preliminarily be dissolved in water.
starting point and the practical basis of the improved method.
The dissolution of the sulphurous acid can be effected very rapidly in contact
with water in a state of great division and within suitable limits of temperature.
In case the sulphurous acid is obtained in the combustion or roasting of pyrites,
blendes or other metallic sulphides, part is conducted from the furnaces with all the
gases with which it is mixed, and after having passed through the drying furnace
and cooling apparatus hereinafter described is introduced into a series of chambers
or dissolving towers constructed of wood, lead or any suitable material which
cannot be attacked by the acid. The water is distributed therein in the form of
jets and cascades, or projects from rose heads or spraying apparatus. The general
movement of the gases takes place in the opposite direction to that of the water,
the gases which are rich in sulphurous acid arriving from one side and the pure
water from the other, the latter passing again and again through the apparatus
until it has attained the desired degree of concentration. The other part of the
sulphurous gases is passed into leaden chambers in order to be converted therein
into sulphuric acid which is necessary for the subsequent operations.

page_text: In case the sulphurous acid is obtained in the treatment of various metals for
extracting sulphates therefren, the gas being much richer can be conducted directly
or after cooling from sulphatisation vessels into dissolving apparatus of much
smaller capacity than those necessary for the gases from the pyrites furnaces.
this case the sulphurous solution itself constitutes a bye-product which is sufficiently
concentrated for being put in the market.
In
The same object can be obtained by the dissolution of gaseous sulphurous acid
proceeding from the recovering or other apparatus hereinafter referred to, and
which irrespective of the air inlets is always much richer than that which comes
from pyrites furnaces. The gases leaving these special apparatus having been
partly deprived are passed to towers for dissolving the gases from the pyrites
furnaces.
In any case the dissolution of the sulphurous acid will never be complete. In
order that the undissolved part shall not be really lost it is conveyed to leaden
chambers with the part coming from the pyrites furnaces. It is this mode of opera-
tion which constitutes improved method.
The solution of sulphurous acid can also be prepared by the compression of this
gas in contact with water. It is in fact well known that its liquefaction takes
place at the pressure of from 2 to 3 atmospheres, but it will not be necessary
to attain this pressure in order that a great part of the acid shall be precipitated
and dissolved the rest passing to the leaden chambers.
The solution of sulphurous acid is conducted in proportion to the requirements
and in a slow and continuous manner into enriching vessels provided with an
agitator, in which it encounters the phosphate ore to be enriched. This phosphate
is first pulverized if it is enriched in the crude state, but the reaction is greatly
facilitated by the previous calcination at the same time the attack of the tricalcic
phosphate is considerably retarded, chiefly by reason of the great facility of the
attack of the lime which causes much more rapidly the neutralization of the
sulphurous acid. After agitating a certain time and after a sufficient rest a first
decantation of water charged with bisulphite takes place either by means of
cocks or by siphons and the partially enriched phosphate remains in the vessel
with a certain quantity of the solution. Another quantity of sulphurous water is
then introduced the agitation takes place a second time and is followed by a second
decantation and so on until the enrichment is deemed sufficient.
The solutions of bisulphites can be obtained in two distinct titrations according
to the solutions of sulphurous acid employed. If bisulphite of commerce is to be
obtained use is made of a solution of sufficiently concentrated sulphurous acid,
which is easily obtained by the employment of rich gases such as those resulting
from the manufacture of metallic sulphates, on coming from recovering vessel
as will be set forth. In the contrary case, that is to say, if poor gases coming
from pyrites or roasting furnaces are employed the solution of bisulphite cannot
attain the desired degree for being put in the market, and the sulphurous acid
gas would to a great extent be lost if it were not recovered by the following
operations.
The solutions of poor sulphites are treated by sulphuric acid in recovering vessels
provided with agitators. Insoluble sulphate of lime is formed, which sets free the
sulphurous acid that is either disengaged in the gaseous state or remains in solution
in the mother liquors.
When the reaction has been effected to a sufficient extent all the liquid containing
the sulphate of lime in suspension is slowly introduced into a large precipitating
tower through one or more holes provided at a short distance from the base, that is
to say at a sufficiently great depth below the level of the water. Scrapers
arranged in a suitable manner are set in motion in a very slow manner by means of
a central axis for the purpose of moving the solid materials towards the discharge
opening.
A valve opened according to requirements, or preferably a pump which acts
much more regularly, causes the sail materials to be discharged into large basin-

page_text: from which the sulphate of lime precipitated again is removed in order to be put in
the market after drying and before or after calcination. It may be observed that
this sulphate of lime is chemically pure absolutely deprived of carbonate of lime,
and gives a plaster which is unexceptionable as regards the fineness of its grains,
and, in the case of the previous calcination, as regards its colour, and it is
adapted for uses which require the very best qualities. From this is obtained one
of my chief bye-products and it may be remarked that this is the first time that an
artificial sulphate of lime is employed in the manufacture of plaster. As to the
mother liquors which have remained in the precipitating tower and have been
rendered clear at the upper part, they are caused to return to the dissolving towers
in which they are charged again with sulphurous acid in addition to that which
they have retained.
With the object of collecting the greatest part of the mother liquors conducted
to the precipitating towers and at the same time effecting the recovery of the
sulphurous acid as far as possible the liquors charged with sulphate may be caused
to pass to filter presses instead of discharging them directly into depositing basins.
The orifices through which they are conveyed to the presses are likewise provided
at the lower part of the tower. The sulphate coming from the filter presses in a
pasty state may be immediately stored in sheds and put in the market after having
been subjected to the above-mentioned operations.
The phosphoric acid of the phosphate originally dissolved by the sulphurous
solution is in its turn recovered in the same manner as the sulphurous acid, but the
following conditions are observed. The lime of the dissolved phosphate passes,
like the lime of the sulphite, to the state of sulphate of lime. The phosphoric
acid, set at liberty, remains in the solution. In the following operation a fresh
quantity is added in consequence of the same reactions and from this results a
continuous accumulation of phosphoric acid. This phosphoric acid concurs with
the sulphurous acid to enrich the phosphates, and having reached a given degree of
concentration it may effect this enrichment alone.
Furthermore it may be employed exclusively for dissolving the phosphate and
treated by sulphuric acid as hereinbefore stated, it gives solutions of more and
more concentrated phosphoric acid adapted in this state to be put in the market,
for which purpose it only needs a complementary concentration by evaporation.
The weak or concentrated phosphoric solutions can be utilized in the course of
the operations either as diluting liquors for the manufacture of superphosphate, the
phosphoric acid then becoming an active agent concurrently with the sulphuric
acid, or when sufficiently concentrated it may be employed alone.
The solutions of phosphoric acid may also be employed for the manufacture of
precipitated phosphates or for any other industrial uses.
It will be understood that the employment of sulphurous acid as an agent for
enriching phosphate leads to the preparation of phosphoric solutions capable of
producing the same effects, but which are of much more extensive industrial
application. This is the first time that these solutions are produced in a state
of such great purity and that they are utilized in such a complete manner.
may be added that these solutions can be very rapidly obtained in a high
degree of concentration by the attack of carbonated or uncarbonated rich ores
and by the employment of the same apparatus and reactions as hereinbefore
mentioned.
It
The enriched phosphate which has remained in the enriching vessels is dis-
charged immediately after the last decantation and carried away by the water
in excess into a vessel from which a bucket chain conducts it to a funnel placed
above a measuring apparatus. This apparatus which may be of cylindrical or
other suitable form serves for measuring exactly the quantity of phosphate to be
introduced into the kneading apparatus above which it is placed. The com-
munications of the measuring apparatus on the one hand with the funnel for the
bucket chain, and on the other hand with the kneading apparatus can be

page_text: interrupted by valves. When the valve of the kneading apparatus is closed the
valve of the funnel is open and permits the enriched phosphate to accumulate
in the measuring apparatus. When the latter is full the valve of the funnel is
closed and the valve of the kneading apparatus opened, which permits the material
to fall into the kneading apparatus wherein it is treated by sulphuric acid either
alone with a view to the manufacture of superphosphate only, or with azotized,
potassic or other substances with a view to the manufacture of compound manures.
Whatever may be the product manufactured it is caused to flow into cooling pits
then dried as hereinafter set forth, and crushed in order to be put in the market.
All the operations above described, namely the dissolution of sulphurous acid,
the enrichment of the phosphates, the treatment of the mother liquors by sulphuric
acid for recovering the sulphurous acid, the separation of the sulphates from the
same mother liquors and the treatment of the enriched phosphate for converting it
into superphosphate, must be carried out in closed vessels, but the latter com-
municate freely with the large gas pipe leading from the pyrites or other
furnaces through the dissolving towers to the leaden chambers. This is a
necessary precaution the importance of which it is easy to understand. It has
for its object to avoid not only losses of sulphurous acid, which would result
from an operation in the open air, but also the serious inconveniences caused by
the diffusion of this sulphurous acid into the atmosphere both as regards the work
in the factory and the injuries occasioned in the neighbourhood. For this purpose
in the large gas pipe is always a suction to the outside, that is to say a slight
depression relatively to the external atmospheric pressure. In order that this
condition shall be constantly fulfilled and considering that the hot gases coming
from the furnaces inust descend, circulate in the pipes of the drying apparatus and
the dissolving towers, which causes many obstacles to their normal movement, the
latter may be assisted by artificial means such as a fan or the like arranged at any
point of their passage. Valves for regulating the current may be provided at
different points of the pipes, chiefly for the purpose of suitably regulating the part
of the gases which has to pass to the dissolving towers, and that which passes
directly to the leaden chambers.
For completing the description of the operations comprised in the improved
method of manufacture it remains to be explained how I effect the drying of the
enriched phosphate if it is not immediately transformed into superphosphate; the
drying, and the calcination of the sulphate of lime if it takes place; and the drying
of the superphosphate.
These operations are carried out by the aid of the heat of the gases leaving the
furnaces. This heat is at about 1100 degrees and it must be lowered to at most
30 degrees before the introduction of the gases into the dissolving towers, and to
from 50 to 60 degrees before their admission into the leaden chambers.
The burning of the plaster, that is to say the departure of the water of
crystallization comirences at 115 degrees and does not require for its completion a
much higher temperature. As to the drying of the phosphates and super-
phosphates this is effected by the evaporation of the water, which can take place
at 100 degrees and even below.
For this purpose 1 construct in the immediate neighbourhood of the pyrites
furnaces drying furnaces of masonry divided into compartments and capable of
holding one or more carriages each. These carriages are made of iron and formed
of superposed floors which receive the materials to be dried. Thus charged they
are introduced into the said compartment by moving them on rails arranged above
a subsoil where cast iron or earthenware pipes having a large diameter are placed,
and in which the gases coming from the furnaces circulate. The doors of the
compartments are carefully closed after the introduction of the carriages, the air
being admitted at the lower part underneath the pipes so that it can be regulated
at will.
The atmosphere of the compartment being heated more and more ultimately

page_text: produces the desired effect. The compartments nearest to the inlet for the gases
from the furnaces being heated to the greatest extent receive the substances
requiring the most heat, the sulphates first, the superphosphate next, and the
phosphates last. As to the heated air charged with humidity it escapes from the
compartments through special pipes communicating directly with the chimney of
the factory or with a special chimney. Hearths are arranged in connection with
certain of the compartments of the drying furnaces for aiding the heat of the gases
if this heat is not sufficient.
The hot gases circulating in the pipes become cooler the wider the air passages
are open; but the cooling cannot be carried to such an extent that the gases may
be introduced into the dissolving towers or into the leaden chambers. It is
necessary or useful in this case to subject them previously to a complementary
cooling action which brings them to the suitable temperatures, for example by
sufficiently prolonging the pipes of the conduit so as to extent either into the open
air or into cold water or by employing any of the usual apparatus.
Accordingly the above described method comprises:
(1) The production of sulphurous acid by the usual means or utilization of the
acid actually lost in the various industries.
(2) The dissolution in water of part of the sulphurous acid, which is an essential
condition.
(3) The passage of the other part of the sulphurous acid and of the undissolved
part into leaden chambers for manufacturing sulphuric acid therefrom.
(4) The treatment by the sulphurous water mentioned in the 2nd clause of
comparatively poor natural or artificial phosphates which have or have not been
subjected to a previous calcination and the enrichment of which has commenced.
From the result (a) enriched phosphate in the solid state, and (b) sulphites of
lime dissolved in the mother liquors.
(5) The drying of the enriched phosphate or the treatment of the said phosphate.
by sulphuric acid for obtaining superphosphates or compound manures.
(6) The solutions of sulphite of lime which are not sufficiently rich are treated
by sulphuric acid with the object of recovering the sulphurous acid. By this means
sulphate of lime is obtained.
(7) The precipitation of the sulphate of lime, which is collected in order to be
either dried only or calcined as plaster stone.
(8) The strengthening of the mother liquors by fresh sulphurous acid and
re-employment of the said liquors for enriching the phosphate as mentioned in the
4th clause.
The
(9) The utilization of the phosphoric acid dissolved in the enriching operations
mentioned in the 4th clause, either as enriching agent concurrently with sulphurous
acid or alone after the solution has been deprived of sulphurous acid.
utilization of the phosphoric solutions in the manufacture of superphosphate or
in the manufacture of precipitated phosphate or for the concentration of these
solutions.
(10) The utilization of the excessive heat of the gases leaving the pyrites or
other sulphide furnaces for the drying or the calcination of the solid products or
the concentration of the phosphoric acid.
The principal commercial products which may result from these various
operations are:-
Metallic sulphates, such as sulphate of iron, zinc, copper and the like.
Concentrated solutions of sulphurous acid.
Rich phosphates of lime.
Superphosphates of lime.
Precipitated phosphates.
Compound manures.
Concentrated bisul hites of lime.
Burned or unburned sulphate of lime.

page_text: Безщитоке от пон.
Weak or concentrated phosphoric solutions.
Dated this 25th day of March 1891.
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, W.C., Agents for the Applicant.
COMPLETE SPECIFICATION.
An Improved Method chiefly designed for Enriching Calcareous
Phosphates and for Manufacturing Superphosphates and Various
Bye-products.
I. HENRY HARRIS LAKE, of the firm of Haseltine Lake & Co. Patent
Agents 45 Southampton Buildings in the County of Middlesex do hereby
declare the nature of this invention and in what manner the same is to be
performed, to be particularly described and ascertained in and by the following
statement:-
This invention relates to a method which is chiefly designed for enriching
calcareous phosphates, and for manufacturing superphosphates and various bye-
products.
Its fundamental idea consists in utilizing the grouping of certain modes of
manufacture giving rise to the production of sulphurous acid for causing the latter
by means of special methods to react upon comparatively poor calcareous phosphate
ores, from which it removes a more or less considerable part of carbonate of lime.
Sulphites and bisulphites of lime result from this reaction, and the ore is
enriched proportionately to the quantity of carbonate thus transformed.
The principal modes of manufacture giving rise to the production of sulphurous
acid are the treatment of various metals, such as iron, copper, zinc, by concentrated
sulphuric acid for obtaining sulphates therefrom; the combustion or roasting of
sulphides of iron, copper, lead, zinc and the like for the manufacture of sulphuric
acid or for the extraction of these various metals; the treatment of ores of sulphur
which consists in burning part of the sulphur for extracting the rest; and the
combustion of the same ores.
When put in presence of poor calcareous phosphates the sulphurous acid acts
upon the carbonate of lime, expels the carbonic acid, but under certain special
conditions attacks the phosphate itself very slowly.
The sulphurous acid must be previously dissolved in water.
point and the practical basis of the improved method.
This is the starting
From this results a neutral sulphite of lime which by means of an excess of acid
is transformed into a soluble bisulphite which can be easily decanted leaving the
enriched phosphate in an undissolved state.
The dissolution of the sulphurous acid can be effected very rapidly in contact
with water in a state of great division and within suitable limits of temperature.
In case the sulphurous acid is obtained in the combustion or roasting of pyrites,
blendes or other metallic sulphides, part is conducted from the furnaces with all the
gases with which it is mixed, and after having passed through the drying furnace
and cooling apparatus hereinafter described is introduced into a series of chambers
or dissolving towers constructed of wood, lead or any suitable material which
cannot be attacked by the acid. The water is distributed therein in the form of
jets and cascades or projects from rose heads or spraying apparatus.
The general movement of the gases takes place in the opposite direction to that
of the water the gases which are rich in sulphurous acid arriving from one side
and the pure water from the other, the latter passing continuously through the
apparatus until it has attained the desired degree of concentration. The other part
of the sulphurous gases is passed into leaden chambers in order to be converted
therein into sulphuric acid which is necessary for the subsequent operation.

page_text: In case the sulphurous acid is obtained in the treatment of various metals for
extracting sulphates therefrom, the gas being much richer can be conducted
directly or after cooling from sulphatization vessels into dissolving apparatus of
much smaller capacity than those necessary for the gases from the pyrites furnaces.
In this case the sulphurous solution itself constitutes a bye-product which is
sufficiently concentrated for being put in the market.
The same object can be obtained by the dissolution of gaseous sulphurous acid
proceeding from the recovering or other apparatus hereinafter referred to, and
which irrespective of the air-inlets is always much richer than that which coines
from pyrite furnaces. The gases leaving these special apparatus having been
partly deprived are passed to towers for dissolving the gases from the pyrite
furnaces.
In any case the dissolution of the sulphurous acid will never be complete. In
order that the undissolved part shall not be really lost it is conveyed to leaden
chambers with the part coming from the pyrite furnaces. It is this mode of
operation which constitutes the improved method.
The solution of sulphurous acid is obtained by simply dissolving the gas in water
or is obtained by liquefying the sulphurous acid gas under the action of the
pressure in the presence of water, the dissolution of this gas will never be
absolutely complete; it is useful that the undissolved portion shall not be lost in
the air. For this purpose this portion of the sulphurous gases is directed towards
the leaden chambers to serve for the manufacture of sulphuric acid.
The solution of sulphurous acid is conducted, in proportion to the requirements
and in a slow and continuous manner, into enriching vessels provided with agitators,
in which it encounters the phosphate ore to be enriched. This phosphate is first
pulverized if it is enriched in the crude state, but the reaction is greatly facilitated
by the previous calcination, at the same time the attack of the tricalcic phosphate
is considerably retarded, chiefly by reason of the great facility of the attack of the
lime which causes much more rapidly the neutralization of the sulphurous acid.
After agitation for a certain time and after a sufficient rest, a first decantation of
water charged with bisulphite takes place, either by means of cocks or by syphons,
and the partially enriched phosphate remains in the vessel with a certain quantity
of the solution. Another quantity of sulphurous water is then introduced, the
agitation takes place a second time and is followed by a second decantation and so
on until the enrichment is deemed sufficient.
The solutions of bisulphites can be obtained in two distinct titrations according
to the solutions of sulphurous acid employed. If bisulphite of commerce is to be
obtained use is made of a solution of sufficiently concentrated sulphurous acid,
which is easily obtained by the employment of rich gases such as those resulting
from the manufacture of metallic sulphates, on coming from recovering vessels as
will be set forth. In the contrary case, that is to say, if poor gases coming from
pyrites or roasting furnaces are employed the solution of bisulphite cannot attain
the desired degree for being put on the market, and the sulphurous acid gas would
to a great extent be lost if it were not recovered by the following operations.
The solutions of poor sulphites are treated by sulphuric acid in recovering vessels
provided with agitators. Insoluble sulphate of lime is formed, which sets free the
sulphurous acid that is either disengaged in the gascous state or remains in solution
in the mother liquors.
When the reaction has been effected to a sufficient extent all the liquid containing
the sulphate of lime in suspension is slowly introduced into a large precipitating
tower through one or more holes provided at a short distance from the base, that is
to say, at a sufficient depth below the level of the water. Scrapers arranged in a
suitable manner are set in motion in a very slow manner by means of a central axis
for the purpose of moving the solid materials towards the discharge opening.
A valve opened according to requirements, or preferably a pump which acts much
more regularly, causes the said materials to be discharged into large basins from
which the sulphate of lime precipitated again is removed in order to be put on the

page_text: market after drying and before or after calcination. It may be observed that this
sulphate of lime is chemically pure, is absolutely deprived of carbonate of lime, and
gives a plaster which is unexceptionable as regards the fineness of its grains, and,
in the case of the previous calcination, as regards its colour, and it is adapted for
uses which require very best qualities. From this is obtained one of our chief
bye-products, and it may be here remarked that this is the first time that an
artificial sulphate of lime has been employed in the manufacture of plaster. As to
the mother liquids which remain in the precipitating tower and which have been
rendered clear at the upper part, they are caused to return to the dissolving towers
in which they are charged again with sulphurous acid in addition to that which
they have retained.
With the object of collecting the greatest part of the mother liquors conducted
to the precipitating towers, and at the same time effecting as far as possible the
recovery of the sulphurous acid, the liquors charged with sulphate may be caused
to pass to filter presses instead of discharging them directly into depositing basins.
The orifices through which they are conveyed to the presses are likewise provided
at the lower part of the tower. The sulphate coming from the filter presses in a
pasty state may be immediately stored in sheds and put on the market after having
been subjected to the above mentioned operations.
The phosphoric acid of the phosphate originally dissolved by the sulphurous
solution is in its turn recovered in the same manner as the sulphurous acid, but the
following conditions have to be taken into account. The lime of the dissolved
phosphate passes, like the lime of the sulphite, to the state of sulphate of lime.
The phosphoric acid, set at liberty, remains in the solution. In the following
operation a fresh quantity is added in consequence of the same reactions, and from
this results a continuous accumulation of phosphoric acid. This phosphoric acid
concurs with the sulphurous acid to enrich the phosphates, and having reached a
given degree of concentration it may effect this enrichment alone.
Furthermore, it may be employed exclusively for dissolving the phosphate, and,
treated by sulphuric acid as hereinbefore stated, it gives solutions of more and more
concentrated phosphoric acid adapted in this state, to be put on the market, for
which purpose it only needs a complementary concentration by evaporation.
The weak or concentrated phosphoric solutions can be utilised in the course of
the operations either as diluting liquors for the manufacture of superphosphate, the
phosphoric acid then becoming an active agent concurrently with the sulphuric
acid, or when sufficiently concentrated it may be employed alone.
The solutions of phosphoric acid may also be employed for the manufacture of
precipitated phosphates or for any other industrial uses.
It will be understood that the employment of sulphurous acid as an agent for
enriching phosphate leads to the preparation of phosphoric solutions capable of
producing the same effects, but which are of much more extensive industrial
application. This is the first time that these solutions have been produced in a
state of such great purity and utilized in such a complete manner. It may be
added that these solutions can be very rapidly obtained in a high degree of con-
centration by the attack of carbonated or uncarbonated rich ores and by the
employment of the same apparatus and reactions as hereinbefore mentioned. The
enriched phosphate which has remained in the enriching vessels is discharged
immediately after the last decantation and carried away by the water in excess into
a vessel from which a bucket chain conducts it to a funnel placed above a measuring
apparatus. This apparatus which may be of cylindrical or other suitable form
serves for measuring exactly the quantity of phosphate to be introduced into the
kneading apparatus above which it is placed. The communications of the measuring
apparatus on the one hand with the funnel for the bucket chain, and on the other
hand with the kneading apparatus can be controlled by valves. When the valve
of the kneading apparatus is closed the valve of the iunnel is open and permits the
enriched phosphate to accumulate in the measuring apparatus. When the latter
is full the valve of the funnel is closed and the valve of the kneading apparatus

page_text: opened, which permits the material to fall into the kneading apparatus wherein it
is treated by sulphuric acid either alone with a view to the manufacture of super-
phosphate only, or with azotized, potassic or other substances with a view to the
manufacture of compound manures. Whatever may be the product manufactured
it is caused to flow into cooling pits, then dried as hereinafter set forth, and crushed
in order to be put on the market.
All the operations above described, namely the dissolution of sulphurous acid,
the enrichment of the phosphates, the treatment of the mother liquors by sulphuric
acid for recovering the sulphurous acid, the separation of the sulphates from the
same mother liquors and the treatment of the enriched phosphate for converting it
into superphosphate, must be carried out in closed vessels, which however commu-
nicate freely with the large gas pipe leading from the pyrites, or other furnaces
through the dissolving towers to the leaden chambers.
This is a necessary precaution the importance of which it is easy to understand.
It has for its object to avoid not only losses of sulphurous acid, which would result
from an operation in the open air, but also the serious inconveniences caused by the
diffusion of this sulphurous acid into the atmosphere both as regards the work in
the factory and the injuries occasioned in the neighbourhood. For this purpose
there is in the large gas pipe always a suction to the outside, that is to say, a slight
depression relatively to the external atmospheric pressure. In order that this
condition shall be constantly fulfilled, and considering that the hot gases coming
from the furnaces must descend, circulate in the pipes of the drying apparatus and
the dissolving towers, which causes many obstacles to their normal movement, the
latter may be assisted by artificial means, such as a fan or the like arranged at any
point of their passage.
Valves for regulating the current may be provided at
different points of the pipes, chiefly for the purpose of suitably regulating the part
of the gases which has to pass to the dissolving towers, and that which passes directly
to the leaden chambers.
For completing the description of the operations comprised in the improved
method of manufacture it remains to be explained how I effect the drying of the
enriched phosphate if it is not immediately transformed into superphosphate; the
drying, and the calcination of the sulphate of lime if it takes place, and the drying
of the superphosphate.
These operations are carried out by the aid of the heat of the gases leaving the
furnaces. This heat is at about 1100 degrees Centigrade and it must be lowered
to at most 30 degrees Centigrade before the introduction of the gases into the
dissolving towers and to from 50 to 60 degrees Centigrade before their admission
into the leaden chambers.
The burning of the plaster, that is to say the departure of the water of crystalli-
zation commences at 115 degrees Centigrade and does not require for its com-
pletion a much higher temperature. As to the drying of the phosphates and
superphosphates this is effected by the evaporation of the water, which can take
place at 100 degrees Centigrade and even at a lower temperature.
For this purpose I construct in the immediate neighbourhood of the pyrite
furnaces drying furnaces of masonry divided into compartments and capable of
holding one or more carriages each. These carriages are made of iron and formed
of superposed floors which receive the materials to be dried. Thus charged they
are introduced into the said compartments by moving them on rails arranged above
a subsoil where cast-iron or earthenware pipes having a large diameter are placed,
and in which the gases coming from the furnaces circulate. The doors of the
compartments are carefully closed after the introduction of the carriages the air
being admitted at the lower part underneath the pipes so that it can be regulated
at will.
The atmosphere of the compartment being heated more and more ultimately
produces the desired effect. The compartments nearest to the inlet for the gases
from the furnaces being heated to the greatest extent receive the substances
requiring the most heat, the sulphates first, the superphosphates next, and the
D

page_text: phosphates last. As to the heated air charged with humidity it escapes from the
compartments through special pipes communicating directly with the chimney of
the factory or with a special chimney. Hearths are arranged in connection with
certain of the compartments of the drying furnaces for aiding the heat of the gases
if this heat is not sufficient.
The hot gases circulating in the pipes become cooler the wider the air passages
are open; but the cooling cannot be carried to such an extent that the gases may
be introduced into the dissolving towers or into the leaden chambers. It is
necessary or useful in this case to subject them previously to a complementary
cooling action which brings them to the suitable temperatures, for example by
sufficiently prolonging the pipes of the conduit so as to extend either into the open
air or into cold water or by employing any of the usual apparatus.
Accordingly the above described method comprises:
(1.) The production of sulphurous acid by the usual means or utilization of the
acid actually lost in the various industries.
(2.) The dissolution in water of part of the sulphurous acid, which is an essential
condition.
(3.) The passage of the other part the sulphurous acid and of the undissolved
part into leaden chambers for the manufacture of sulphuric acid therefrom.
(4.) The treatment by the sulphurous water above mentioned of comparatively
poor natural or artificial phosphates which have or have not been subjected to a
previous calcination and the enrichment of which has commenced.
From this result enriched phosphate in the solid state and sulphites of lime
dissolved in the mother liquors.
(5.) The drying of the enriched phosphate or the treatment of the said phosphate
by sulphuric acid for obtaining superphosphates or compound manures.
(6.) The solutions of sulphite of lime which are not sufficiently rich are treated
by sulphuric acid with the object of recovering the sulphurous acid. By this means
sulphate of lime is obtained.
(7.) The precipitation of the sulphate of lime, which is collected in order to be
either dried only or calcined as plaster stone.
(8.) The strengthening of the mother liquors by fresh sulphurous acid and
re-employment of the said liquors for enriching the phosphate as mentioned in the
4th clanse.
(9.) The utilization of the phosphoric acid dissolved in the enriching operations
mentioned in the 4th clause, either as enriching agent concurrently with sulphurous
acid or alone after the solution has been deprived of sulphurous acid. The
utilization of the phosphoric solutions in the manufacture of superphosphate
or in the manufacture of precipitated phosphate or for the concentration of these
solutions.
(10.) The utilization of the excessive heat of the gases leaving the pyrites or
other sulphide furnaces for the drying or the calcination of the solid products or the
concentration of the phosphoric acid.
The principal commercial products which may result from these various operations
are:-
Metallic sulphates such as sulphate of iron, zinc, copper, and the like, concen-
trated solutions of sulphurous acid, rich phosphates of lime, superphosphates of lime,
precipitated phosphates, compound manures concentrated bisulphites of lime, burned
or unburned sulphate of lime, sulphuric acid sesquioxide of iron, weak or concen-
trated phosphoric solutions.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed as communicated to me
by my foreign correspondents, I declare that what I claim is :-
The herein described process for enriching phosphates of lime, which consists in
pulverizing and calcining the ore of phosphate of lime, then treating it by sulphurous
acid dissolved in water, and subsidiarily the manufacture, as by-products of sulphite

page_text: and bisulphite of lime by the action of sulphurous acid upon the carbonate of lime,
contained in the ore, also of artificial sulphate of lime by the action of sulphuric
acid upon the bisulphite of lime with recovery of the sulphurous acid; and also of
a solution of phosphoric acid, the whole substantially as herein before described.
Dated this 24th day of December 1891.
453
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, Agents for the Applicant.