IMPROVEMENTS IN THE MANUFACTURE OF ALKALIES AND PHOSPHATES
Year: 1884

page_text: I SIDNEY GILCHRIST THOMAS of 9 Palace Chambers Westminster Bridge London
temporarily residing at the Hotel Kirsch, Algiers, Africa Metallurgist do hereby
declare the nature of said Invention for IMPROVEMENTS IN THE MANUFACTURE OF
ALKALIES AND PHOSPHATES to be as follows:-
This invention relates to the manufacture of caustic alkali and phosphate of soda
and lime and other commercial alkaline salts. I find that I can manufacture these
by means of the nascent phosphoric acid (which would otherwise be a waste
product) produced by treating molten phosphoric iron in a Siemens furnace or
Bessemer converter with a lime or magnesian lining, from salt. I thus substitute
for the expensive sulphuric acid and carbonic acid employed in the Leblanc process
an acid which is now practically wasted and which is itself utilized by my
process.
In carrying out my invention I run molten iron which I prefer to be first
desiliconised or low in silicon into a lime or magnesian line converter or Siemens
furnace. The salt is added in the proportion of more than six parts of salt to each
one part of Phosphorus with a similar amount for any silicon contained in the
metal. Part may be thrown into the converter or furnace before the metal is run
in, volatilisation being prevented by covering it with lime or limestone or enclosing
it in a rough cast iron or lime casing. The greater part of the salt may however
be introduced with advantage by blowing it in through twyers with some lime or
lime and oxide of iron Water gas superheated steam or hydrogen yielding
substances may be also blown in to promote the decomposition of the salt.
a test shows that the whole of the phosphorus has been transformed into P₂ 0,
the easily fluid slag produced is run off and the phosphate of soda lixiviated out.
From the solution phosphate of lime may be precipitated with milk of lime leaving
caustic soda solution. Carbonate of soda may be produced by passing CO, through
the solution and other soda salts may be similarly produced.
When
The gases evolved from the converter should be passed through condensing
towers to precipitate any volatilised phosphate etc. with water.
Chloride of potassium may be substituted for the sodium salt when it is desired
to produce potassic compounds.
Dated this first day of January 18S4.

page_text: I SIDNEY GILCHRIST THOMAS of 9 Palace Chambers Westminster Bridge, London,
temporarily residing at the Hotel Kirsch, Algiers Africa Metallurgist do hereby
declare the nature of my invention for IMPROVEMENTS IN THE MANUFACTURE OF
ALKALIES AND PHOSPHATES 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 the manufacture of caustic alkali and phosphates of
soda and lime and other commercial alkaline salts and also (as bye-products) to the
production of chlorine and hydrochloric acid.
I find that I can manufacture these, by means of the nascent phosphoric acid
(which would otherwise be a waste product) produced by treating molten highly
phosphoric iron in a Reverberatory gas furnace or Bessemer converter, with a lime
or magnesian or other basic or neutral lining, from salt.
I thus substitute for the expensive sulphuric acid employed in the Leblanc
Process, an acid which is now practically unused and which is itself utilised by my
Process. The phosphoric iron preferably employed should be very rich in
phosphorus, such as that known as ferrophosphorus, which is made chiefly from
Basic converter slag sinelted with silicious phosphoric ores or slags; as a phosphide
of iron nearly free from carbon and silicon may be thus readily obtained, containing
from five to thirty per cent of phosphorus-If the iron employed contains any
considerable amount, say one per cent, of silicon and carbon, these substances are
first removed preferably by blowing in a gannister lined Bessemer vessel. The
phosphoric iron in a molten state and free or practically free from silicon and
carbon is run as hot as possible into a gas furnace or converter lined with lime,
magnesia, refractory iron ore, water cooled ingot iron blocks, or other basic or
neutral lining. I find the presence of carbon or silicon prevents or retards the
formation of phosphate of soda. I prefer a Siemens furnace, though other gas
furnaces or a converter may be used-Before introducing the decarburised
phosphoric metal, a part or all of the salt to be converted is spread on the furnace
hearth, being covered with magnesia, oxide of iron, limestone or lime, or even with
a plate of or rough casing of cast iron to prevent too rapid volatilisation-I find it
generally best only to add a part of the salt in this way, the rest being blown in
through one or more twyers with an air blast.
I also blow into the iron phosphide bath superheated steam with the air, and
salt to promote and facilitate the reaction; the supply of steam should be increased
or diminished so that while a lively reaction takes place the metal is not set or
rendered cold.
The air blast may, when non silicious iron-ore is readily obtainable, be replaced
more or less completely by iron ore additions as an oxidising agent. The bath of
metal should be considerably deeper than in the ordinary Siemens practise and a
rotating circular hearth may be advantageously used-The total quantity of salt
used should not be less than six or seven times the weight of the phosphorus
contained in the iron, and it is generally requisite to add considerably more than
this to allow for loss by volatilisation. When the metal is very high in phosphorus
the addition of salt may be with advantage divided into several parts and the slag
run off from time to time before adding a fresh quantity. The operation is
continued till a sample of the furnaced metal shows by its fracture that the iron is
free from phosphorus, or if the alkaline slag gives indications of too rapid
volatilisation, this also may be considered a sign that the alkaline slag should be
run off and the metal finished by treating it if necessary with lime and then with
spiegel etc in the way usual with steel makers.

page_text: If the conversion of the salt is operated in a Bessemer Converter, which is
generally only desirable when exceedingly hot metal not very high in Phosphorus
is employed, it is best not only to use steam superheated to a very high degree but
also hot blast. The salt is best added in part before the metal is run in and in
part through the twyers and great care must be taken not to allow so much steam
to pass as to unduly cool the metal. The reactions and conduct of the operations
is otherwise the same as when a Reverberatory furnace is used.
If it is desired to recover the chlorine and hydrochloric acid which are liberated,
the gases evolved from the bath should be passed through condensing towers where
also a certain amount of volatilised alkali and phosphate may be recovered by
washing the gases by well known appliances and methods. This recovery is more
readily effected when a Bessemer converter is used. The fluid slag which is
produced as above described consists mainly of phosphate of soda with some oxide
of iron and other bases and a little silica. It is run from the furnace or converter
into bogeys and transferred into lixiviating tanks preferably while still hot, as this
saves much grinding. The alkaline phosphate is here lixiviated out and the
solution run off and either evaporated or treated with milk of lime so as to obtain
caustic soda and phosphate of lime. Carbonate of soda and other soda salts may
be also readily obtained by well known means from these solutions.
Chloride of potassium may be substituted for sodic chloride when it is desired to
produce potassic compounds.
I do not claim as part of my invention the addition of small quantities of salt in
any iron or steel-making process as a flux this having been often before proposed
and having nothing in common with my invention; nor do I claim as part of my
present invention the employment of basic or neutral materials for furnace linings;
nor do I claim generally the use of lime as a means of precipitating solutions of
phosphate of soda; but Having now particularly described and ascertained the
nature of my said invention, and in what manner the same is to be performed I
declare that what I claim is The herein described improvements in the manufacture
of alkalies and phosphates consisting in: The process of decomposing alkaline
chlorides by means of the Phosphoric acid produced by oxidising molten
decarburised phosphoric iron or phosphide of iron in a basic or neutral lined
furnace or converter in the presence of steam substantially as herein described.
Dated this eighth day of October 1884.