IMPROVEMENTS IN THE MANUFACTURE OF ALKALINE SILICATES AND OTHER ALKALINE SALTS
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 ALKALINE SILICATES AND OTHER ALKALINE SALTS to be as
follows:-
This invention consists in the manufacture of alkaline that is sodic or potassic
silicates and carbonates from sodic or potassic chloride by means of the silicon
contained in pig iron by utilising the heat and furnaces used in the conversion of
pig iron into ingot metal. The silicic acid thus produced is at present a waste
product.
For carrying out my invention I use a Bessemer Converter or Siemens furnace
lined with lime or inagnesia and I prefer to employ a very silicious pig iron. For
every one part of silicon in the pig I add from five to ten parts of the alkaline
chloride, part of this may be thrown into the Bessemer vessel or furnace before the
metal in which case I prefer it to be enclosed in a rough cast iron casing or covered
with a rough iron plate or with lime or to be enclosed in a compressed lime casing
to prevent volatilisation and part is preferably blown in through vertical or
horizontal twyers. I also find it advantageous to blow in water gas superheated
steam or other hydrogen supplying body to facilitate the reaction.
The slag will be found to consist chiefly of silicate of soda with some sulphate
of soda which is run off lixiviated and evaporated or it may be treated with
carbonic acid gas whereby carbonate of soda and free silicate is formed.
If phosphorus is also present in the pig a further quantity of salt is employed as
described in another specification lodged by me at the same time as the present.
The quality of the steel is by no means deteriorated by this operation but rather
improved and the waste diminished so that the alkaline silicate is obtained with
very little further expense than the cost of the chloride. I prefer to condeuse the
gases produced in the operation which contain hydrochloric and chlorine gases.
Dated this twelfth day of January 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 my invention for IMPROVEMENTS IN THE
MANUFACTURE OF ALKALINE SILICATES AND OTHER ALKALINE SALTS 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 alkaline silicates and ultimately of
carbonates and other alkaline salts from common salt or potassic chloride. The
acids at present used for the preliminary decomposition of alkaline chlorides are
either sulphuric acid or carbonic acid, and in both the processes at present
employed viz the Leblanc and the ammonia process-large quantities of lime
are converted into a waste product. In the ammonia process the expensive agent,
ammonia, is also wasted in considerable quantity, while expensive and special plant
is required in carrying out both processes.
The decomposition of chlorides by sand and steam by the use of special apparatus
has also been proposed but, owing to the cost of the apparatus and imperfection of
the decomposition, the difficulty of maintaining an adequate temperature, and
other drawbacks, has not proved technically successful. By my invention I
substitute for the decomposing reagents above mentioned nascent silica produced
by exposing highly silicious molten iron to oxidising influences and so utilise not
only the silica produced, which is now a waste product, but also the intermolecular
heat liberated in its oxidation.
In carrying out my invention I uso a Bessemer converter or a gas furnace,
preferably a Siemens furnace, with a silicious lining, or a neutral lining may be
used, and I employ a highly silicious pig iron. What is generally known as silicon-
pig containing from five to twenty per cent of silicon may be most advantageously
used. It is also very important to have as little carbon as possible in the iron, as
carbon and carbonic oxide impede the formation of alkaline silicate, and carbon
when exposed to the action of steam abstracts heat from the surrounding media.
In carrying out the decomposition of the chloride, an amount of salt is employed
amounting to from six to ten times the weight of the silicon contained in the iron
with which it is treated, the excess beyond the theoretical quantity providing for
the variable loss by volatilisation. A great part of the salt is introduced into the
converter or furnace before the iron is run in, this part should be protected from
too rapid volatilisation by a rough iron plate or casing, or by covering it with iron
orc, or sometimes with lime or, if a Siemens furnace is used, with limestone. The
metal is then run in as hot as possible and exposed to the oxidising action of jets
of superheated steam and air which should also be superheated. A further quantity
of salt should be introduced through the twyers. If a converter is used I prefer
one with side twyers. Great care must be taken so to regulate the admission of
steam that the metal is not too much cooled at any time. It is also frequently
desirable for the same reason and to prevent volatilisation to divide the salt
addition into several parts and to run off part of the slag from time to time.
When a gas furnace is used, magnesia or lime bricks may be used in the roof as
these are less affected by volatilised alkali and alkaline slag splashings than silica
bricks. The operation may be pushed to the point of removing all the silicon if
the bath is kept hot enough. If however the metal cools too much or when the
metal is shown by a test piece to be quite desiliconised, whichever first happens,
the remaining slag is run off into bogeys and the metal finished in the usual way

page_text: if it contains phosphorus it is finished in another basic converter or furnace. The
slag thus formed consists of silicate of soda with some oxide of iron and other
basic silicates, and it requires very prolonged boiling in water, preferably under
pressure, to dissolve out the sodic silicate which is often very difficultly soluble in
water. From the sodic silicate, carbonate and hydrate of soda may be obtained by
well known processes, alkaline silicate being readily decomposed.
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. 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 use of salt as a flux in metallurgical
operations 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 alkaline
silicates and other alkaline salts consisting in the decomposition of alkaline
chlorides by the silica produced by oxidising molten silicious pig iron in presence of
alkaline chlorides substantially as herein described.
Dated this eighth day of October eighteen hundred and eighty four.