Improvements in Furnaces and Apparatus for Heating Pots and Crucibles.
Year: 1888

page_text: Date of Application, 6th Oct., 1888
Complete Specification Left, 6th July, 1889-Accepted, 17th Aug., 1889
PROVISIONAL SPECIFICATION.
Improvements in Furnaces and Apparatus for Heating Pots and
Crucibles.
I, WILLIAM GEORGE FORSTER of Lonesome Chemical Works, Streatham Common
in the County of Surrey, Chemist, do hereby declare the nature of this invention
to be as follows:-
The object of my invention is to effect economy in heating pots and crucibles
especially in concentrating alkali liquors and in the distillation of sodium and
potassium. 1st. by providing a furnace which will minimise the destruction of the
pots, pans and retorts used in such operations and will also largely economise fuel.
2nd. by supplying an improved method of setting the pots or retorts together with the
mechanical appliances necessary for carrying my invention into practical use.
It is well known that the present mode of firing alkali pots and also sodium and
potassium retorts is generally by means of direct flame acting on the external surfaces
of the pots or retorts. Coal or coal slack is the fuel used with an almost unlimited
admission of air.
The result of this method of heating is the production of flame which acting on
the iron vessel at a high velocity and at a temperaturo akin to white heat exercises' a
very destructive effect on the metallic surfaces in contact-rapid oxidation follows-
evinced by continuous scaling. Further with this system it is impossible to secure
regularity of temperature and from this cause alone great damage is done owing to
the continual contraction and expansion of the iron thereby perpetually breaking the
crystallization of the metal-a fruitful source of cracks..
The manner in which alkali pots and retorts are at present set is such that the
weakest part, that is the part mostly directly acted upon by the strongest heat, has in
a great measure to support the weight of the vessel and its contents.
I am aware that in order to meet this, and also to provide for the wear by scaling
the pots are thickened at the bottom, but still bulges are common-cracking frequent
and collapse not unusual.
By my invention 1 remedy or greatly ameliorate the foregoing evils.
1st. By economy of fuel-2nd. By controlling the temperature-3rd. By supplying
heat without flame (practically so) and without appreciable velocity-4th. By
mechanical arrangements for so setting the pot or the retort as to lessen the dangers
above referred to-and thereby lengthening the life of the pot or other vessel
employed.
The description of my furnace &c. is as follows-
The furnace consists of a brick building lined with fire brick-the interior is
either conical or domed. A sufficiently large aperture is provided on top to admit of
the pot or retort being lowered into position. The fire grate instead of being one bed
is formed into a circular fire by means of a brick pier which rises from the common
foundation of the furnace and makes a brick centre. The diameter of this pier in
conjunction with the superficial area of the fire grate required determines the length
of the fire bars which radiate to the surrounding walls. The height of the pier above
the grate regulates the depth of the fire. The ash pit is the space immediately
beneath the fire bars, which when the furnace is at work is completely closed in the
openings constructed for withdrawing ashes and handling the fire bars being filled
in with loose brick and clayed up leaving only one or two slits for the admission
of air.
The top of the furnace is fitted with stout iron plates to withstand the wear and
tear of the workmen who feed the furnace from above. The pot or retort is
lowered into position and is maintained suspended by chains or hanging rods

page_text: fitted with screw hooks which afford facilities for regulating the distance between
the bottom of the pot and the central pier below it. The pier also enables me to use
a discharge pipe from the bottom of the vessel-which in some operations is of
importance. In such cases the pipe is brought through the pier which protects it
from the fire-and is carried below into a tunnel specially provided for this purpose.
My object in dividing the fire by a pier is to obtain a more economical distribution
of the superficial area of the fire grate required to heat a given quantity-and at the
same time to diminish the direct action of the fire on the bottom of the vessel.
In firing I adopt the system of slow combustion. The fuel I use is preferably coke,
free from bituminous matter and as dry as possible. Only sufficient air is admitted
to maintain a slow and steady combustion. The slits left open for this purpose may be
diminished according as the temperature rises.
Dated this 6th day of October 1888.
.
COMPLETE SPECIFICATION.
Improvements in Furnaces and Apparatus for Heating Pots.and
Crucibles.
I, WILLIAM GEORGE FORSTER, of Lonesome Chemical Works, Streatham Common,
in the county of Surrey, Chemist, 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:-
"
My invention relates to furnaces or apparatus for heating pots and crucibles, and
especially such as are used in concentrating alkali liquors and in the distillation of
sodium and potassium.
It is well known that the present mode of firing alkali pots and also sodium and
potassium retorts is generally by means of direct flame acting on the external surfaces
of the pots or retorts, coal or coal slack being the fuel used with an almost
unlimited admission of air.
The result of this method of heating is the production of flame, which, acting on
the iron vessel at a high velocity and at a temperature akin to white heat, exercises
a very destructive effect on the metallic surfaces in contact, so that rapid oxidation
follows as is evinced by continuous scaling. With this system of heating also it is
impossible to secure regularity of temperature and from this cause alone great damage
is done owing to the continual contraction and expansion injuring the crystallization
of the metal which thus ultimately cracks.
Further alkali pots and.retorts are at present set in such a manner that the weakest
part, that is the part most directly acted upon by the strongest heat, has, in a
great measure, to support the weight of the vessel and its contents.
I am aware that in order to meet this, and also to provide for the wear by scaling,
the pots are thickened at the bottom, but still bulges are common, cracking frequent
.and collapse not unusual.
The object of my invention is to provide a furnace which will be heated regularly
and uniformly whereby the destruction of the pots, pans and retorts used in the
various operations will be minimized and which will also largely economise fuel; and
to supply an improved method of setting the pots or retorts, together with mechanical
appliances necessary for carrying my invention into practical use.
In the accompanying drawing,
Figure 1 is a vertical section of a furnace constructed according to my invention, a
pot or retort being shown located therein.
Figure 2 is.a plan of the same, partly in section on the line xx figure 1.
Figure 3 is a view of a detail.
The furnace comprises a brick building.a having an internal chamber 6 lined with
fire-brick. This chamber is domed, or of a conical shape, as shown, and has at the top
an aperture c to allow of the introduction and removal of the pot or retort.d.
A

page_text: Around the upper part of the furnace are a series of openings e, through which the
fumes pass into the fluo f, the latter having an outlet g into a flue h, the said outlet
being provided with a damper i.
The pot or retort is supported upon a central pier j, surrounded by a fire-grate k
having the bars 1, which radiate to the surrounding walls. The height of the pier
above the grate regulates the depth of the fire. By dividing the fire by means of
the pier I obtain an economical distribution of the heat, and diminish the direct
action of the fire upon the vessel. The inclined sides of the furnace serve to reflect
the heat from the grate onto the retort. The space m immediately beneath the fire-
bars serves as an ash-pit, passages n n being provided, as indicated by dotted lines in
figure 2, for withdrawing the dust and ashes from the ash-pit. When the furnace is
at work the openings to these passages are almost or completely closed being filled in
with loose brick and clayed or luted up, leaving only one or two slits for the admission
of air. Or sliding or other adjustable dampers or doors can be used for the purpose.
The top of the furnace is fitted with stout iron plates o to withstand the wear and
tear of the workmen who feed the furnace through the openings o¹..
2°
The pot or retort having been lowered into position is maintained partly suspended
by chains p p, as shown in figure 1 (or by hanging rods) fitted with screw-hooks q
carried by stirrups r, having nuts s, s, or otherwise arranged for permitting of regu-
lating the extent to which the pot or retort bears upon the pier.
The said pot or
retort is thus prevented from collapsing when heated. The chains are connected to
the retort by eyes or loops tt, the latter being held in position by the bolts u u which
secure the cover of the retort.
By the use of the pier I am enabled to use a discharge pipe, which in some opera-
tions is of importance. In such cases the pipe is brought from the bottom of the
vessel, through the pier which protects it from the fire, and is carried below into a
tunnel w specially provided for this purpose.
In the use of my furnace I preferably employ gas-coke as fuel, as it is practically
free from bituminous matter. The fuel should be as dry as possible. The supply of
air to the furnace is regulated according to the temperature required.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is :-
(1) A furnace for heating pots, crucibles and the like having a central pier
surrounded by a grate below the level of the said pier; and a domed or inclined top
for reflecting the heat of the fire onto the pot, crucible or retort, substantially as, and
for the purposes, described.
(2) In a furnace of the kind hereinbefore described, adjustably suspending the pots
or crucibles therein, substantially in the manner, and for the purpose, specified.
(3) The improvements in furnaces for heating pots and crucibles, substantially as
herein before described and illustrated in the accompanying drawing.
Dated this 6th day of Ini.. 1000
G. F. REDFERN & Co.,
4, South Street, Finsbury, London, Agents for the Applicant.