IMPROVEMENTS IN FURNACES FOR CHEMICAL PROCESSES
Year: 1884

page_text: "
I, JAMES MACTEAR, of 16 Burnbank Gardens, Glasgow, in the County of
Lanark, North Britain, Manufacturing Chemist, do hereby declare the nature of my
said invention for "IMPROVEMENTS IN FURNACES FOR CHEMICAL PROCESSES" to be
as follows:-
My said Invention relates to chemical furnaces partly of the kind described in
the Specifications of Patents granted to me, No 4870 of 1879 and N° 4511 of 1880,
and has for its objects to improve and simplify the construction of some of the
parts, and to modify the arrangements for applying the heat so that the gases or
vapors evolved from the matters which are being furnaced or heated may be
conveyed away without being mixed with the fire gases.
The rotating hearth or bed of my improved furnace is constructed of firebricks
or slabs so as to be of a slightly spherical form on its upper side and concave with
radial strengthening ribs on its underside, and it is bound by a ring or annular
frame of iron or steel, by which it is supported on conical rollers running on a
circular track. A low concave roof is formed over the hearth or bed, and
immediately above this roof there is formed a flue space for the fire gases the heat
from which is transmitted down through the roof to the materials on the hearth.
Another flue space for the fire gases is formed beneath the hearth; and the upper
flue space is by preference divided by partitions so as to lead the fire gases first
across through a middle space and then back through two side spaces. From these
side spaces the fire gases may be led by descending flues to horizontal flues
communicating with the centre of the space below the hearth, the gases being led
away from this lower space by an annular flue into which there are a number of
openings.
The rotating hearth is formed with a slightly raised rim over which the materials
operated on gradually overflow, the fresh materials being introduced at or near the
middle. The materials overflow upon an annular plate fixed to a girder which
supports the roof, the plate forming the bottom of an annular channel and having
at its inner edge a groove or smaller channel into which dips a cylindrical flango
fixed to the rim of the hearth. A portion of the overflowing materials fills the
smaller channel and with the dipping Hange forms a sufficiently close joint. The
materials in the larger channel are carried round by blades projecting from the
rotating hearth to a discharge hopper at one point where the materials fall through
the hopper to a truck placed below to receive them, the hopper being fitted with
double doors which are opened at suitable intervals. A sufficiently tight joint is
made round the lower flue space by a cylindrical flange fixed to the underside of
the rotating hearth and dipping into an annular channel filled with sand or other
luting material.
1'

page_text: Stirring or agitating apparatus of the kind described in my earlier Specifications
hereinbefore referred to may be fitted to my improved furnace; or instead of
rotating stirrers either stationary oblique blades or ploughs may be used, or such
oblique blades or ploughs fitted on rocking spindles and having a slow oscillating
movement imparted to them to make them guide the materials towards and from
the centre alternately. The feeding arrangements will vary according to the
particular chemical materials to be furnaced in each case. Tf the furnace is used
for decomposing common salt with sulphuric acid a central dish may be formed or
placed upon the hearth as and for the purpose described in my earlier Specifications
herein before referred to. Or instead of having the first stage of the decomposition
effected in such central dish, it may be effected as described in my Specification
N° 2102 of 1876, in one or more separate pans or vessels from which the partially
decomposed materials may be transferred to the main furnace. If the furnace is
used in some processes as for example in that for heating or calcining bicarbonate
of soda obtained in the ammonia-soda process in order to drive off one equivalent
of carbonic acid and any remaining ammonia the central dish will not be required;
and the materials may be put into the furnace in separate charges at intervals,
whilst for decomposing common salt and for some other processes the supply or
feed and the discharge may be made practically continuous.
In all cases my improved furnace is provided with a flue or duct for leading off
gases or vapors evolved from the materials which are being furnaced and when
required such gases or vapors are led to condensing or absorbing apparatus of the
kinds usually employed.
COMPLETE SPECIFICATION.
I, JAMES MACTEAR, of 16 Burnbank Gardens, Glasgow, in the County of Lanark
North Britain, Manufacturing Chemist, do hereby declare the nature of my said
invention for 1MPROVEMENTS IN "FURNACES FOR CHEMICAL PROCESSES" and in
what manner the same is to be performed, to be particularly described and
ascertained in and by the following statement, that is to say :-
My said Invention relates to chemical furnaces of the kind described in the
Specifications of Patents granted to me No 4870 of 1879 and N° 4511 of 1880, and
has for its objects to improve and simplify the construction of some of the parts,
and to modify the arrangements for applying the heat, so that the gases or vapors
evolved from the matters which are being furnaced or heated may be conveyed
away without being mixed with the fire gases.

page_text: My improved furnace is delineated on two sheets of explanatory drawings which
are hereunto appended, figure, 1, on sheet, 1, being a plan with some internal parts
indicated by dotted lines; whilst figure, 2, on sheet, 2, is a vertical section. In
these drawings the same reference numerals are used to mark the same or like
parts wherever they are repeated.
The rotating hearth on bed, 3, of my improved furnace is constructed of fire
bricks or slabs so as to be of a slightly spherical form on its upper surface, and
concave with radial strengthening ribs on its underside; and it is bound by a ring
or annular frame, 4, of iron or steel, by which it is supported on conical rollers, 5,
running on a circular track, 6. The rollers, 5, are connected and held together by
two rings, 7, one inside and the other outside of them, the spindles on which the
rollers revolve, connecting the two rings. A low concave roof, 8, is formed over the
hearth or bed, 3; and immediately above this roof there is formed a flue space, 9,
for the fire gases the heat from which is transmitted down through the roof, 8, to
the materials on the hearth,.3. Another flue space, 10, for the fire gases is formed
beneath the hearth, 3; and the upper flue space, 9, is, by preference divided by
partitions, 11, (figure 1) so as to lead the fire gases which enter, at, 12, from the
fire place, 13, first across through the middle space between the partitions, 11, and
then back through the spaces on the outer sides of these partitions. From these
side spaces the fire gases are led by descending flues, 14, to horizontal flues, 15,
communicating by a short vertical flue, 16, with the centre of the space, 10, below
the hearth, 3, the gases being led away from this lower space, 10, by an annular
flue, 17, into which there are a number of openings, 18.
The rotating hearth, 3, is formed with a slightly raised rim, 19, over which the
materials operated on gradually overflow, the fresh materials being introduced at
or near the middle. The materials overflow upon an annular plate, 20, fixed to
the girder, 21, which supports the roof, the plate, 20, forming the bottom of an
annular channel and having at its inner edge a groove or smaller channel, 22, into
which dips a cylindrical flange, 23, fixed to the rim, 19, of the hearth, 3. A portion
of the overflowing materials fills the smaller channel, 22, and with the dipping
flange, 23, forms a sufficiently close joint. The materials in the larger channel are
carried round by blades projecting from the rotating bearth to a discharge
hopper, 24, at one point (not however, necessarily in the position where for con-
venience it has been shown in figure, 2). This discharge hopper may be arranged
to discharge directly down into a truck the hopper being in that case provided
with two doors or valves either of which is only opened when the other is shut.
I however prefer to connect the discharge hopper or duct, 24, to a long horizontal
covered trough, 25, shown in cross section in figure, 2, and having working in it a
screw, 26, for conveying the materials away. This trough, 25, or at least the part
of it close to the discharge duct or hopper, 24, and this duct itself remain sufficiently
full of materials to prevent any objectionable escape of gas through the trough.
A sufficiently tight joint is made round the lower flue space, 10, by a cylindrical
flange, 27, fixed to the underside of the edge of the rotating hearth, 3, and dipping
into an annular channel, 28, filled with sand or other luting material.
Stirring or agitating apparatus of the kind described in my earlier Specifications
herein before referred to may be fitted to my improved furnace, this apparatus
comprising rotating stirrers, 29, such as are shown in figure, 2. Or instead of such
rotating stirrers, either stationary oblique blades or ploughs may be used, or such
oblique blades or ploughs fitted on vertical rocking spindles, and having a slow
oscillating movement imparted to them to make them guide the materials towards
and from the centre alternately.
The feeding arrangements will vary according to the particular chemical materials
to be furnaced in each case. If the furnace is used for decomposing common salt
with sulphuric acid, a central dish, 30, may be formed (or placed) on the hearth, 3,
as and for the purpose described in my earlier Specifications hereinbefore referred
to. A stationary plough, 31, placed in the central dish, 30, so as with the rotation of
the hearth to stir the materials in the dish, and this plough is formed with a spur

page_text: bearing on the edge of the dish to aid in transferring the overflowing materials
from the dish to the hearth, 3. Or instead of having the first stage of the decom-
position of the salt effected in such central dish, 30, it may be effected as described
in my Specification N° 2102 of 1876, in one or more separate pans or vessels, from
which the partially decomposed materials may be transferred to the main furnace.
If the furnace is used in some processes,-as for example in that for heating or
calcining bicarbonate of soda obtained in the ammonia-soda process in order to
drive off one equivalent of carbonic acid, and any remaining ammonia,--the central
dish, 30, will not be required; and the materials may be put into the furnace in
separate charges at intervals, whilst for decomposing common salt, and for some
other processes the supply or feed and the discharge may be made practically
continuous.
In all cases my improved furnace is provided with a flue or duct, 32, for leading
off gases or vapors evolved from the materials which are being furnaced, and, when
required, such gases or vapors are led to condensing or absorbing apparatus of the
kinds usually employed.
The hearth, 3, is entirely supported on the rollers, 5, and is made to rotate by
means of a ring of teeth, 33, fixed to the underside of the annular frame, 4, of the
hearth, this ring of teeth, 33, having in gear with it a pinion, 34, upon a shaft, 35,
driven by any suitable motor. In some cases either the upper flue space, 9, or the
lower one, 10, may be dispensed with.
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
t
The improved construction of rotating-hearth furnace for chemical processes, such
furnace having flues or flue spaces for the passage of the heating or fire gases either
above the hearth space or below the hearth, or both above and below, substantially
as and for the purposes herein before described.
Dated this thirteenth day of Anril 1985