IMPROVEMENTS IN THE MANUFACTURE OF FERTILIZERS
Year: 1883

page_text: LETTERS PATENT to Herbert John Allison, of the firm of Allison Brothers,
Patent Agents, Southampton Buildings, London, for an Invention of
"IMPROVEMENTS IN THE MANUFACTURE OF FERTILIZERS," communicated to
him from abroad by The Scribner Process Company (Incorporated), of the
City and State of New York, United States of America.
COMPLETE SPECIFICATION filed by the said Herbert John Allison at the
Office of the Commissioners of Patents on the 21st August 1883.
HERBERT JOHN ALLISON, of the firm of Allison Brothers, Patent Agents,
Southampton Buildings, London, "IMPROVEMENTS IN THE MANUFACTURE OF
FERTILIZERS," communicated to me from abroad by The Scribner Process Company
(Incorporated), of the City and State of New York, United States of America.
This invention relates to methods of treating ferruginous and aluminous
minerals, commonly known as phosphates of iron and alumina, for the production*
therefrom of artificial fertilizers. The object of the process which constitutes the
said invention is to render available a larger proportion of the fertilizing principle
contained in the mineral than has heretofore been done, or, in other words, to
obtain an increased proportion of phosphoric acid from the mineral in a condition.
suitable for mixing with ammoniacal or other matters in the production of
fertilizers.
Heretofore, in the treatment of these mineral phosphates, the material has
usually been calcined, or roasted, and then combined with sulphuric or other acids,
while in many instances other substances have been added and the compounds'
subjected to various treatments in order to obtain fair results.
Over these processes the invention is an improvement, the present process being
not only more economical, but yielding a very much larger percentage of phosphatic
material in a condition known in the art as reverted, or available.
The invention, broadly stated, consists in simultaneously exposing ferruginous
and aluminous phosphates to the action of applied heat and sulphur, or, in other

page_text: •
words, bringing into contact with the phosphates, while hot, either the vapour of
sulphur or sulphurous anhydride.
To effect this, the mineral is ground, mixed with a small proportion of granulated
or powdered sulphur, and then roasted, or the sulphur may be vaporized or
burned in separate receptacles, and introduced in a gaseous state to the heated
mineral.
The method in detail of carrying out the invention is as follows:-
A proper quantity of the mineral commonly known as phosphate of iron and
alumina is primarily crushed or ground in any convenient manner, and with it is
intimately mixed a small proportion of granulated or powdered sulphur, the
proportion of the latter being about two per cent by weight.
The mixture is then roasted, no special appliance being essential to the ready
accomplishment of this step in the process, though an ordinary retort is preferable,
as by its use much of the sulphur may be saved by sublimation.
The physical action of the heat upon the mixture is primarily to dissociate from
the mineral phosphates the water contained in them, and to oxidize the sulphur,
this giving rise to the production of available phosphoric acid, which is preferably
due to the chemical re-action produced by vapor of sulphurous acid, which is
formed in immediate contact with the powdered mineral.
The mixture is roasted until this re-action is complete. This may be determined
by an examination of the chemical change taking place, or is evidenced by a
change in the color and character of the mass, which becomes darker in shade and
finer in. .grain.
When, in lieu of heating a mixture of the phosphatic rock with sulphur, the latter
is introduced as vapor, or sulphurous anhydride, to the mineral while roasting, the
process is conducted in the following manner:—
A suitable quantity of the phosphates is ground and heated in a receptacle or
retort.
In a separate receptacle sulphur vapor or sulphurous anhydride is produced by
the heating or burning of sulphur or compounds containing the same, and the
vapor or fumes is forced into the retort containing the mineral, while the latter
is roasting. By the action of heat water is dissociated from the mineral, and by
the chemical re-action resulting from the heat and the mixing of the vapor of
water and the vapor of sulphur or sulphurous anhydride, sulphurous acid is formed,
which, acting on the mineral, produces a large proportion of available phosphate.
In the case of most phosphates of iron and alumine, sufficient water is contained
in the mineral itself to produce the requisite chemical re-action. Certain other
substances, however, such as the phosphate of lime, contain little or no water in
their composition, and in these cases the déliciency may be supplied by introducing
into the heated retortia jet of steam along with the sulphur vapor.
In order that the action of the vapor of sulphur may reach all portions of the
nineral, the latter is agitated during the time that the vapor is introduced. This
may be done by stirring the mass, or revolving the receptacle in which it is
contained.'
The roasting and adinission of vapor are to be carried on simultaneously, and
care must be taken that the water contained in the mineral is not driven off before
the vapor is introduced, as otherwise no chemical change would take place.
The amount of sulphur vapor introduced should be about two per cent, by
weight, of mineral, and when passed slowly through the heated mass, the mineral
assumes a darker shade and becomes much finer. When sulphurous inhydride is
used, the amount may be determined by the effects produced, which are the same
as when sulphur vapor is employed.
After the mineral has been subjected to the treatment above described, it
becomes a commercially valuable fertilizing compound, containing a large per
centage of available phosphoric acid. It may then, without further treatment, be
mixed with potash or ammoniacal matters, as usually done in the manufacture of
these substances, or it may be subsequently treated with acids by processes similar

page_text: to that commonly applied to the reduction of phosphatic minerals when not
previously treated in the manner herein described..
To utilize the product resulting from the treatment described for the manufacture
of super-phosphates, sulphate of ammonia with sulphuric acid may be added to
yield any desired percentage of ammonia. Or it may be advantageous to add
kainite or muriate of potash before mixing with the acid, as in the first instance
the sulphate of ammonia serves to form a double soluble salt with the iron and
alumina phosphates, while in the second instance the sulphate of potash formed by
the addition of the sulphuric acid serves to dry out the super-phosphates, so that
the material may be more readily disintegrated and powdered for transportation
and use.
From the chemical changes that take place in the above process, viz: the
formation of sulphurous acid vapor throughout the heated mass, it is obvious that
in lieu of mixing the mineral and sulphur together and then heating them, that
the mineral alone may be heated and the vapor of sulphur introduced to the
heated mass. It is further true that the same results will be reached by the
introduction to the heated mass of sulphurous anhydride, and in general the objects
of the invention are attained by heating the mineral in the presence of any matters
which produce sulphurous acid by chemical union with the constituent parts of the
mineral.
Having now described the nature of the said invention, what I claim is:-
First. The treatment of phosphatic minerals, such as phosphates of iron and
alunina, for the production of fertilizers, by simultaneously exposing the said
minerals to the action of heat and sulphur or its equivalent.
Second. The treatment of phosphatic minerals such as phosphates of iron and
alumina, for the production of fertilizers, by mixing with a suitable quantity of the
said mineral when in a finely divided condition, a small percentage of sulphur or
its equivalent, and then roasting the said mixture.
Third. The process of manufacturing fertilizing compounds from mineral
phosphates, which consists in grinding and roasting the phosphates, and forcing
through the mineral, while roasting, the vapor of sulphur or sulphurous anhydride,
with or without steam.
Fourth. The process of manufacturing fertilizing compounds from mineral
phosphates, which consists in grinding and roasting the phosphates in a proper
receptacle, producing the vapor of sulphur, or sulphurous anhydride, in a separate
receptacle, and forcing the same through the roasting mineral,
Fifth. The process of manufacturing fertilizing compounds from mineral
phosphates, which consists in grinding and roasting the phosphates, forcing
through the same the vapor of sulphur, or sulphurous anhydride, at the same
time agitating or stirring the heated mineral.
In witness whereof, 1, the said Herbert John Allison, have hereunto set my
hand and seal this 21st day of August in the year of our Lord One thousand eight
hundred and eighty-three.
HERBERT. J. ALLISON. (L.S.)