IMPROVEMENTS IN THE CONSTRUCTION AND USE OF APPARATUS EMPLOYED IN EFFECTING CHEMICAL DECOMPOSITION." PROVISIONAL SPECIFICATION
Year: 1880

page_text: LETTERS PATENT to Robert Stirling Newall and Frederick Stirling Newall,
both of the Washington Chemical Works, Newcastle upon Tyne, for an Inven-
tion of "IMPROVEMENTS IN THE CONSTRUCTION AND USE OF APPARATUS
EMPLOYED IN EFFECTING CHEMICAL DECOMPOSITION."
PROVISIONAL SPECIFICATION left by the said Robert Stirling Newall and
Frederick Stirling Newall at the Office of the Commissioners of Patents on
the 15th June 1880.
ROBERT STIRLING NEWALL and FREDERICK STIRLING NEWALL, both of the
Washington Chemical Works, Newcastle upon Tyno. "IMPROVEMENTS IN THE
CONSTRUCTION AND USE OF APPARATUS EMPLOYED IN EFFECTING CHEMICAL
DECOMPOSITION."
Our Invention is especially applicable to the decomposition of salt in the
manufacture of soda, but may be used for other purposes.
The apparatus at present commonly used for decomposing salt consists of a cast
iron pan and one or two furnaces, called "roasters." The pan measures from 7 to
10 feet in diameter, and 20 to 24 inches in depth in the centre. The bottom is
from 5 to 7 inches thick, tapering to 2 inches at the upper parts, which rests on
brickwork, and weighs about 6 tons. The pan has sometimes a metal cover, in
which case heat is applied both below and above; if the cover is of brick heat is
applied below. In this pan the salt is partially decomposed. The "roaster in
which the decomposition is completed is either an open furnace, through which the
flame or heated air from the fire passes in contact with the partially decomposed
salt, or it is a close furnace or muffle having the salt in the interior, and the heat
from the firo outside.
"
The mixture of about equal weights of salt and acid is put into the pan, and after
partial decomposition it is shoved into the roaster, and stirred by hand until the
process is completed. The whole process involves a very great expenditure of
labour and fuel, and from the bydrochloric acid being given off rapidly in the first
part of the process, and being mixed with air and gases from the fire, it requires
farger and more expensive condensers than if the hydrochloric acid were kept free
[Price 621
'

page_text: from admixture. The pans also suffer much from corrosion, and often break from
the cooling of the thick metal when putting the charge into them when nearly red
hot, and otherwise they entail great expense for repairs, and great stoppage of
work. The nature of our Invention to remedy these defects consists,―
First. In making the pans of phosphor bronze, which we find withstands the
effects of acids much better than cast iron or steel. If the pan is of the usual form
and size, or from 7 to 10 feet diameter, and 15 to 24 inches deep in the middle, we
make the top sides about of an inch thick, and the bottom part about an inch
and a quarter thick, and taper it off to join the side, which is less subject to wear.
Second. Our Invention consists in making the pans of such a form that they may
bo heated by steam or hot air instead of by a furnace as at present. We have
found by experiment that a mixture of salt and sulphuric acid is rapidly decomposed
at a temperature of about 120° centigrade, or a steam pressure of 30 lbs.
We thereforo make the pan double, and in the interspace we admit steam or hot
air. On the upper surface of this double pan we place the mixture of salt and acid,
which wo keep stirred by mechanical or other means until the decomposition is
carried to the required degree, when we expel the sulphate from the steam pan into
the roaster, where the decomposition is completed. The pan is covered as usual to
collect the gas which is conveyed to the condenser. The roaster may be of the
usual kind, or it may be a rotating pan, such as those now used for carbonating
furnaces, or it may be a fixed pan with rotating stirrers.
Third. We prefer however to completo the decomposition in one pan and to keep
the furnace gases entirely separate from the hydrochloric acid. For this purpose
we use the pan heated from below by hot air to about 350° centigrade, and wo
make the process continuous by feeding the salt and acid into the pan regularly and
in small quantities, and stirring the mixture by mechanical means until the
decomposition is completo, by which time the sulphato will have reached tho
opening either in the side of the pan or in the centre, through which it is expelled
by the working of the apparatus.
Wo profer feeding at the centre and working the materials to the side, so as to
do away with the necessity of a rim to the pan.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Robert Stirling Newall and Frederick Stirling Newall in the Great Seal
Patent Office on the 15th December 1880.
ROBERT STIRLING NEWALL and FREDERICK STIRLING NEWALL, both of the
Washington Chemical Works, Newcastle on Tyne. 'IMPROVEMENTS IN THE
CONSTRUCTION AND USE OF APPARATUS EMPLOYED IN EFFECTING CHEMICAL
DECOMPOSITION."
Our Invention of "Improvements in the Construction and use of Apparatus
Employed in Effecting Chemical Decomposition" is especially applicable to the
decomposition of salt in the manufacture of soda, but may be used for other
purposes.
The apparatus at present commonly used for decomposing salt consists of a cast
iron pan and one or two furnaces called "roasters." The pan measures from seven
to ton feet in diameter, and twenty to twenty four inches in depth in the centre.
The bottom is from five to seven inches thick, tapering to two inches at the upper
part, which rests on brickwork, and weighs about six tons. The pan has sometimes
a metal cover, in which case heat is supplied both below and above; if the cover is
of brick heat is applied below. In this pan the salt is partially decomposed.
The roaster in which the decomposition is completed is either an open furnace,
through which the flame or heated air from the fire passes in contact with the
partially decomposed salt, or it is a close furnace or muffle having the salt in tho
interior, and the heat from the firo outside. The mixture of about equal weights
of salt and acid is put into the pan, and after partial decomposition it is shoved
into the roaster, and stirred by hand until the process is completed. The wholo
process involves a very great expenditure of labour and fuel, and from the hydro-
chloric acid being given off rapidly in the first part of the process, and being mixed
with air and gases from the fire, it requires larger and more expensive condensers
than if the hydrochloric acid were kept free from admixture. Tho pans also suffer
much from corrosion, and often break from the cooling of the thick metal when
putting the charge into them when nearly red hot, and otherwise they entail great
expense for repairs and great stoppage of work.
The nature of our Invention to remedy theso defects consists, first, in making
the pans of phosphor bronze, which we find withstands the effects of acids much
better than cast iron or steel. If the pan is of the usual form and sizo, or from
seven to ten feet diameter, and fifteen to twenty four inches deep in the middlo, we
make the top sides about three quarters of an inch thick, and the bottom part about
an inch and a quarter thick, and taper it off to join the side, which is less subject
to wear.
Second. Our Invention consists in making the pans of such a form that they
may be heated by steam or hot air instead of by a furnace as at present. We have
found by experiment that a mixture of salt and sulphuric acid is rapidly decom-
posed at a temperature of about one hundred and twenty degrees centigrade or a
steam pressure of thirty pounds.
We therefore make the pan double, and in the interspace we admit steam or hot
air. On the upper surface of this double pan we place the mixture of salt and
acid, which we keep stirred by mechanical or other means until the decomposition
is carried to the required degree, when we expel the sulphato from the steam pan
into the roaster, where the decomposition is completed. The pan is covered, as
usual, to collect the gas, which is conveyed to the condenser. The roaster may
be of the usual kind, or it may be a rotating pan such as those now used for
carbonating furnaces, or it may be a fixed pan with rotating stirrera.

page_text: Third. We prefer, however, to complete the decomposition in one pan, and to
keep the furnace gases entirely separate from the hydrochloric acid. For this
purpose we use the pan heated from below by hot air to about throe hundred and
fifty degrees centigrade, and we make the process continuous by feeding the salt
and acid into the pan regularly aud in small quantities, and stirring the mixture
by mechanical means until the decomposition is complete, by which time the
sulphate will have reached the opening either in the side of the pan or in the
centre, through which it is expelled by the working of the apparatus.
We prefer feeding at the centro and working the materials to the side, so as to do
away with the necessity of a rim to the pan,
Having thus stated the nature of the said Invention, wo will proceed to describe
the
Fig. 1 represents a fixed pan composed of phosphor bronzo and made in the
proportions and manner hereinbefore stated, which pan is adapted to be heated by
steam or hot air. The top and bottom plates are fastened together at a short
distance apart. Steam of the required temperature (we prefer it to be super
heated) is admitted into the interspace, and a pipe is used to carry off the condensed
water. This pan is worked in the usual way.
Fig. 2 represents a rotating pan heated by steam or hot air. The pan is double,
with a space between the top and bottom plates, and super-heated steam or hot air
at the requisite temperature is admitted into the interspace by a pipe led through
the bottom of the pan. There are holes in the edge of the pan which cause a
circulation of the steam or hot air through the pan. There is a stuffing box on the
outside and a pipe to carry off the condensed steam. Stirrers, such as those
patented by Robert Stirling Newall in One thousand eight hundred and seventy
nine, No. 5230, or others suitable, are used for mixing the materials and discharging
them. Tho pan is supported on live wheels, and motion may be given to it in the
usual way; but wo prefer that shewn in the annexed Drawing, where wheels
. communicate motion from the engine to a shaft which carries a pulley, which, by
means of a wire rope or chain working round a large pulley attached to the edge
of the pan, moves it at the speed of about one revolution per minute. On tho
upper end of the pulley shaft is a crank, which causes the ploughs or stirrers to
Oscillate so as to mix or stir the material. The amount of oscillation is regulated
We find that if the crank shaft revolves six
by altering the length of the crank.
and a half times for onc revolution of the pan it answers admirably, the pulley's
being, of course, in the same proportion. When discharging, we drive at a greater
speed by disengaging one set of spur wheels and putting another into gear.
The salt to be decomposed is fed into the furnace regularly and in small quan-
tities from the hopper on the roof of the pan, by the action of a tappet, as in corn
inills or otherwise, and the requisite quantity of sulphuric acid is admitted by a
pipo from a cistern. These materials are mixed and slowly worked from the centre
of the pan to the outside opening by the ploughs, which are made to act as
dischargers by placing them at the proper angle, and they are so adjusted that the
time of passage of the material across the pan is enough to allow of the required
amount of decomposition to take placo, so that there will be a constant feeding and
a constant discharge combined with a continual mixing of the materials. If it is
stopped, tho crank rod is
wished to discharge the furnace completely the feed
disconnected, and the ploughs are fixed at such an angle as will discharge the
materials in a few revolutions of the pan. The gases are conveyed by flues from
the pan to the condenser, and as they are given off in small regular quantity owing
to the mode of feeding the furnace, and are not mixed with furnace gases, a small
condenser answers the purpose. ·
:

page_text: Having thus described the nature of the said Invention, and in what manner
the same is to be performed, we hereby declare that what we claim as of our
Invention is,-
First. Making decomposing pans of phosphor bronze, as herein before described.
Secondly. Heating decomposing pans by steam or hot air.
Thirdly. The combination of decomposing pans heated by steam or hot air with
continuous feed and discharge actuated by mechanical stirrers.
Fourthly. Using steam pans for the partial decomposition of the salt and
completing it in a roaster heated by a furnace.
And, Fifthly. The mode of moving the pan and ploughs as described.
In witness whereof, we, the said Robert Sterling Newall and Frederick
Sterling Newall, have hereunto set their hands and seals, the Thirteenth
day of December, in the year of our Lord One thousand eight hundred and
eighty
R. S. NEWALL.
(L.S.)
FRED. S. NEWALL. (L.S.)