An Improved Process and Apparatus for Obtaining Silicates for Making Glass and the Production of Hydrochloric Acid.
Year: 1891

page_text: Date of Application, 4th Feb., 1891-Accepted, 9th May, 1891
COMPLETE SPECIFICATION.
An Improved Process and Apparatus for Obtaining Silicates for
Making Glass and the Production of Hydrochloric Acid.
I WALTER WALKER of 132 Adelaide Road London N.W. Engineer 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:-
The object of this invention is to produce pure silicates and hydrochloric acid by
special treatment from common sand and pure metallic chlorides. In carrying out
my invention common sand is finely pulverized and washed with hydrochloric acid
(produced in the process) for the purpose of removing any impurities detrimental
to the manufacture of a pure glass. The sand when dry is thoroughly mixed with the
proper proportions of dry chloride of calcium and chloride of sodium for producing
the class of glass required. The mixture is then heated to a red heat and steam,
preferably in a superheated state, is introduced, upon which hydrochloric acid will
be given off. The steam is continued until all the hydrochloric acid has been
collected and no trace of it remains. The chlorides will be then all decomposed
and the residue will be a friable mass of pure silicates of soda and lime in the
proportions required for making the highest class plate glass, or any other desired
quality in accordance with the quantities which were placed in the mixture. Thus
it will be seen that in the glass material produced by this process common sand
takes the place of the high priced imported sand chloride of calcium (which is a
waste product) takes the place of lime or finely powdered chalk; and common salt
the place of sulphate or carbonate of soda. And that hydrochloric acid is given off*
which may be sold or utilized for manufacturing bleaching powder and the
glass material is absolutely pure and fit for making the very highest class of
plate glass.
The common sand used in this process can be obtained from the sea-shore, or
elsewhere, but it is most important that it should be thoroughly pulverized
preferably wet and well washed with some of the hydrochloric acid recovered in the
process and then dried and perfectly mixed with the chlorides of calcium and
chloride of sodium. The chloride of calcium used can be the waste liquor obtained
from the Solvay soda process in which case the water will have to be evaporated
in the usual manner before mixing with the chloride of sodium and prepared sand.
And any chloride of sodium contained in the liquor will have to be allowed for and
deducted from the amount of chloride of sodium to be added to the mixture in the
shape of common salt.
The chloride of calcium can also be obtained from the waste liquor from the
Weldon process for making chlorine or any other source but in either case the water
must be evaporated first. The sand, chloride of calcium and chloride of sodium
must be well dried, powdered and mixed together before they are heated.
The hydrochloric acid given off in the decomposition will be collected in the
usual manner practised in the Le Blanc process and can be used for the manufacture
of bleaching powder.
If the mixture is made in the proportions necessary the silicates produced will
when melted with plate glass cullet in the usual manner make the very highest class
plate-glass, because the soda, lime and silica will all be practically pure. If thought
advisable dried chloride of calcium alone could be added in about equal parts to
the prepared sand and without the chloride of sodium could be treated exactly as
described above. Then the hydrochloric acid could be collected for making
bleaching powder and the resulting silicates of lime mixed with the proper pro-
portions of prepared sand and sulphate of soda and charcoal or carbonate of soda

page_text: melted down to a high-class plate glass. Care must be taken in making the
proportions of the mixture to always have the chlorides a little in excess of the
silica (sand).
But
I will now describe one means of carrying out my invention but wish to be
understood that I do not confine myself to this method alone because various kinds
of apparatus and proportions may be used to accomplish the same result.
what I have found most advantageous is a circular gas-fired regenerative furnace A
as shewn in the drawing and fitted with a movable bottom a supporting a crucible b
which may be of any size to contain a mixture composed of 60 parts prepared sand,
36 parts chloride of calcium and 32 parts chloride of sodium powdered dry and well
mixed together.
The crucible is arranged so that it can be lowered through the bottom of the
furnace by suitable means, preferably by hydraulic, for the purpose of emptying it
after the conversion of the sand and chlorides into silicates is completed, when it is
again elevated into the furnace to be refilled.
When the crucible is in position in the furnace its top enters a recess c in the top of
the furnace which will form a cover for it. In this cover there are 3 openings one
with a tight-fitting door d through which the mixture is placed into the crucible
and two through which suitable pipes e, f, made of fire-clay, porcelain or otherwise
are inserted. The one e goes to the bottom of the crucible and is open at that end
and perforated with numerous small holes. It fits at top into a pipe e¹ which is
arranged spirally around the crucible and communicates with a steam boiler. The
pipe only just goes through the cover of the crucible and leads to the tower or
other condenser for collecting the hydrochloric acid.
The mixture is then placed in the crucible all around the steam pipe and is then
heated to just below the vaporizing point of salt upon which the steam is turned
on and going through the bottom and perforations in the pipe thoroughly permeates
the whole mass of the mixture, decomposing all the chlorides and giving off hydro-
chloric acid and leaving the silicates of soda and lime. The steam is maintained
until no trace of hydrochloric acid is left and all the chlorides are decomposed.
The hydrochloric acid will escape through the pipe and be collected in the
condenser in the usual way. The residue in the pot is then ready to be melted
down with the addition of cullet &c., by the glass makers in the usual manner.
When the chloride of calcium is used with the prepared sand alone without the
chloride of sodium, the result will be silicate of lime which may be made into glass
by the addition of the proper proportions of prepared sand and carbonate of soda
or sulphate of soda with the addition of the proportions of pulverized coke or
charcoal or a sufficient excess of the prepared sand may be put with the chloride
of calcium to allow of a glass making material to be made by the additional
carbonate of soda alone.
As an alternative plan for carrying out this process the chloride of calcium in
any desired state may be thoroughly mixed with the proper proportion of prepared
sand and then have salt as a vapour blown in mixed with superheated steam; or
the salt may be fed in out of a closed hopper by an automatic or other feeder into
the top of the fire clay pipe and be vaporised by the heat of the steam.
This will
enable the work to be carried on at a higher temperature which may greatly
facilitate the reactions. From experiments made it seems that the reactions that
do take place in the crucible are the breaking up of the steam, and the formation
of the double silicate of soda and lime.
These combinations may be found advantageous to chemical works making
carbonate of soda by the Solvay process and in either case the hydrochloric acid
collected will enable them to make bleaching powder which they cannot do
economically at present.
It will readily be seen that this process may be carried out in reverberatory
furnaces such as are used for roasting copper ore, or rotary furnaces such as are
used for making black ash.
When carried out in a reverberatory or rotary furnace with water gas there may

page_text: be no necessity of introducing steam, the products of combustion being mostly
steam, but other steam may be added. In carrying out this process on a com-
mercial scale it may be found advantageous to take the chloride of calcium in a
saturated solution add the prepared sand and the salt and introduce the mixture
into the pot as a sludge and vaporize the water away before the steam is introduced;
or an arrangement may be made whereby the steam is thoroughly superheated
in the top of the furnace and constantly passed into the crucible through the
perforated pipe or through the bottom of the crucible in a similar manner to a
Bessemer stationary converter.
A mixture consisting of salt brine and saturated solution of chloride of calcium
and purified sand would be continuously fed into the crucible until it was full of a
dry friable mass when the addition of the mixture would be stopped, but the steam
continued until all the hydrochloric acid is given off.
The essential feature is to have the silica (finely pulverized and well washed with
hydrochloric acid) and the chlorides in intimate contact with each other in
conjunction with steam at a temperature suitable to bring about decomposition
which appears from experience to be just below the vaporizing point of common
salt.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner same is to be carried out I declare that what I
claim is:
1st. The process herein described for obtaining silicates of soda and lime or
silicates of lime suitable for making the highest class plate glass, consisting in
heating together common sand (thoroughly pulverised and washed with hydro-
chloric acid) chloride of calcium and chloride of sodium in or about the proportions
and at or about the heats given, and then introducing superheated steam into the
mixture whereby hydrochloric acid is given off and all the chlorides decomposed,
substantially in the manner and for the purposes above set forth.
2nd. The pulverization of the sand and washing of the same with hydrochloric
acid produced in the process for the purposes set forth.
3rd. The improved construction of furnace for use in carrying out my process,
substantially as hereinbefore described and shewn with reference to the accompanying
drawings.
4th. Injecting vaporized salt with superheated steam into a mixture of chloride,
of calcium and prepared sand substantially in the manner and for the purpose here
specified.
Dated 11
WALTER WALKER.
Ernest de Pass,
78, Fleet Street, London, Agent for the Applicant.