IMPROVEMENTS IN THE FURNACES USED " PROVISIONAL SPECIFICATION
Year: 1874

page_text: LETTERS PATENT to Isaac Shimwell McDougall, of the Firm of
McDougall Brothers, of Manchester and London, Manufacturing
Chemists, for the Invention of "IMPROVEMENTS IN THE FURNACES USED
"
PROVISIONAL SPECIFICATION left by the said Isaac Shimwell
McDougall at the Office of the Commissioners of Patents, with his
Petition, on the 16th April 1874.
-
I, ISAAC SHIMWELL MCDOUGALL, of the Firm of McDougall Brothers,
of Manchester and London, Manufacturing Chemists, do hereby declare
the nature of my said Invention for "IMPROVEMENTS IN THE FURNACES -
USED IN THE MANUFACTURE OF ALKALI AND OTHER PRODUCTs," to be as
follows:-
•
This Invention is for applying the fuel or heat necessary for the
manufacture of alkali and for the roasting of salt cake, nitre cake,
sulphate of potash, and other products, and for the finishing of soda ash
immediately under the bed of the furnace, and then through or over

page_text: the surface of the latter, a method hitherto impracticable, except by the
gas process, owing to the rapid destruction of the said furnace bed. It
consists in forming the fire-place in a chamber situated at one end of
the brickwork containing the furnace, the length of the fire-place being
crosswise to the breadth of the said furnace. The fire-bars are placed
deep enough in this chamber to allow of sufficient room above the same
for air to mix freely with the gases of the fuel before passing onward,
the air being admitted to the fire-place chamber by 2 small holes in its
side walls at some like distance above the fire-bars.
Extending longitudinally from the upper side portion of the fire-place
chamber and backwards therefrom, immediately underneath the furnace,
is a flue inclining upwards to the end of the furnace, and divided
transversely into a number of smaller upright flues by substantial
division walls, which are built the full length of the furnace bed. The
crown of the fire-place chamber is formed of a strong double-ringed
brick arch, over which is laid a tile of 3 inches thick, forming a portion
of the furnace bed. This arch spans from the outside walls of the fire-
place chamber (or those walls in proximity to the flues of the decom-
posing pot) to the top ends of the said division walls, connecting which
to a distance of about four feet back from the fire-place chamber is a
series of small one-brick arches. Over these arches are laid tiles 3
inches thick, forming another portion of the furnace bed, the remaining
portion of the latter being formed by placing along its entire length a
double layer of 3 inch tiles covering the upright spaces or flues between
the said division walls. At the back end of and resting transversely on
the furnace bed is a bridge wall to prevent the contents of the furnace
falling into the flues and fire underneath. The gases formed in the fire-
place chamber pass thence through the smaller longitudinal upright
flues over the end of the furnace bed, and over the bridge wall thereon,
through or over the body of the furnace, and coming in contact with the
materials therein are then conveyed by a suitable flue or flues to the
condensing towers or chimney in the usual manner.
If the gases from the fire and the material contained in the furnace,
and the gases from the decomposing pot in the immediate neighbourhood
of the latter can be allowed to combine or mix, economy of fuel will
result by causing the former to pass over and across the decomposing
pot. The heat evolved will accelerate the working of the charge.

page_text: By a suitable arrangement of dampers formed in the end wall of the
brickwork containing the furnace, and opposite to the ends of the
smaller longitudinal upright flues underneath the bridge wall, an equal
distribution of heat can be maintained beneath the furnace bed, and
additional air admitted and regulated as required.
Whilst this method of placing the fire-place chamber and arrangement
of flues is recommended for what is termed "an open roasting furnace,"
it is also claimed as a great improvement in the construction of what is
termed a "blind roasting furnace."
SPECIFICATION in pursuance of the conditions of the Letters Patent
filed by the said Isaac Shimwell McDougall in the Great Seal Patent
Office on the 14th October 1874.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, ISAAC
SHIMWELL MCDOUGALL, of the Firm of McDougall Brothers, of Man-
chester and London, Manufacturing Chemists, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patcut, bearing date the Sixteenth day of April, in the year
of our Lord One thousand eight hundred and seventy-four, in the 37th
year of Her reign, did, for Herself, Her heirs and successors, give and
grant unto me, the said Isaac Shimwell McDougall, Her special license
that I, the said Isaac Shimwell McDougall, my executors, administrators,
and assigns, or such others as I, the said Isaac Shimwell McDougall, my
executors, administrators, or assigns, should at any time agree with, and
no others, from time to time and at all times thereafter during the term
therein expressed, should and lawfully might make, usc, cxcrcise, and
vend, within the United Kingdom of Great Britain and Ireland, the
Channel Islands, and Isle of Man, an Invention for "IMPROVEMENTS IN
THE FURNACES USED IN THE MANUFACTURE OF ALKALI AND OTHER PRODUCTS,"
upon the condition (amongst others) that I, the said Isaac Shimwell
McDougall, my executors or administrators, by an instrument in writing
under my hand and seal, should particularly describe and ascertain the
nature of the said Invention, and in what manner the same was to
be performed, and cause the same to be filed in the Great Seal Patent

page_text: Office within six calendar months next and immediately after the date
of the said Letters Patent.
NOW KNOW YE, that I, the said Isaac Shimwell McDougall, do hereby
declare the nature of my said Invention, and in what manner the same
is to be performed, to be particularly described and ascertained in and
by the following statement, reference being had to the accompanying
Drawings, and to the letters and figures marked thereon, that is to
say:―
This Invention is for applying the fuel or heat necessary for the
manufacture of alkali and for the roasting of salt cake, nitro cake,
sulphate of potash, and other products, and for the finishing of soda ash
immediately under the bed of the furnace, and then through or over the
surface of the latter, a method hitherto impracticable, except by the gas.
process, owing to the rapid destruction of the furnace bed. It consists
in forming the fire-place in a chamber formed at one end of the brick-
work containing the furnace, the fire-bars being placed deep enough
therein to allow of sufficient room above them for air to mix freely with
the gases of the fuel before passing onwards.
Extending longitudinally from the upper side portion of the fire-place
chamber and backwards therefrom immediately underneath the furnace
is a flue inclining upwards to the end of the furnace, and divided
transversely into a number of smaller upright flues by substantial
division walls, which are built the entire length of the furnace bed.
The crown of the fire-place chamber is a strong double-ringed brick arch,
over which are laid tiles three inches thick, forming a portion of the
furnace bed. Connecting the division walls of the flue to a distance of
about four feet back from the fire-place chamber is a series of small
one-brick arches, over which are laid tiles three inches thick, forming
another portion of the furnace bed, the remaining portion of the latter
being formed by placing along its centro length a double layer of three
inch tiles, covering the upright spaces or flues between the said division
walls. At the back end of and resting transversely on the furnace bed
is a bridge wall to prevent the contents of the furnace falling into the
flues and fire underneath. The gases formed in the fire-place chamber
pass thence through the smaller upright flucs over the end of the furnace
bed and over the bridge wall thereon, through or over the top of the
furnace, and coming in contact with the materials thereon are then

page_text: conveyed with the gases from the latter by a suitable flue to the con-
densing towers or chimney in the usual manner.
purpose.
And in order that my said Invention may be fully understood I shall
now proceed more particularly to describe the same, and for that.
shall refer to the several Figures on the annexed Shoot of Drawings, the.
same letters of reference indicating corresponding parts in all the
Figures.
Figure 1 is a sectional plan of the furnace in connection with the
decomposing pot; Figure 2, a horizontal section of the same; Figure 3,
a transverse section on line 1-2 in Figure 2; Figure 4, a transverse
section on line 3-4 in Figure 2; and Figure 5, a transverse section on
line 5-6 in Figure 2.
:
A represents the fire-place chamber formed below the furnace B, and
at one end of the brickwork carrying the same, its length being
crosswise to that of the furnace B. a, a, are the fire-bars placed deep
enough in the chamber A to allow of sufficient room above them for air
to mix freely with the gases of the fuel placed thercon before passing
away. For this purpose two small holes x, x, are formed in the side
walls of the chamber A, through which air enters the interior of the
latter above the fire-bars a, a. Extending longitudinally from the upper"
and inner side portion of the chamber A and backwards therefrom
immediately underneath. the. furnace B is a flue. C inclining upwards to
the end of the latter, and divided transversely into a series of smaller.
upright flues D, D, by substantial division walls E, E, which are built.
the entire length of the furnace bed F, as shown. Over the chamber A
and forming the crown thereof is a strong double-ringed brick arch G,
which spans from the outside wall of the chamber A (or in this case the
wall in proximity to the decomposing pot) to the top end corners of the.
division walls E, E, as shown. Over this arch are laid tiles three inches
thick, forming a portion of the furnace bed F, and connecting the tops
of the division walls E, E, to a distance of, say, four feet. From the-
chamber A towards the back end of the furnace B are small onc-brick
arches H, H, over which are laid tiles three-inches thick so as to form
another portion of the furnace bed F, the remainder of the latter
consisting of a double layer of three-inch tiles simply laid across the
open spaces of the smaller upright flues D, D, between the division
walls E, E. At the back end of and resting transversely on and entirely

page_text: across the furnace bed F is a bridge wall I for the purpose of preventing
the contents of the furnace B from falling into the flues and fire under-
neath. In the end wall K of the brickwork carrying the furnace B
dampers L, L, are formed, one opposite to the back end of each of the
smaller upright flues D, D, whereby at any time a few loose bricks can
be placed in the end of either of the latter for the purpose of equalising
the distribution of the heat beneath the furnace bed F. Additional air
may also be admitted to the flues and furnace through the dampers L, L,
as hereafter described. M and N are flues leading respectively from the
roof of the furnace B and that of the chamber carrying the decomposing
pot O (which in the case under description is used in conjunction with
the furnace B and in proximity thereto, as shewn) to the condensing
towers or chimney in the usual manner.
Supposing the fuel placed on the fire-bars a, a, to be in a state of
combustion tho gases evolved will rise upwards therefrom, and impinging
on the under side of the roof or crown to the chamber A will be diverted
thereby, and pass through the smaller upright flues D, D, over the end
of the furnace bed F and the bridge wall I over and through the body
of the furnace B, where they come in contact with the materials
therein, and are conveyed with the gases or products from such
materials through the flue M to the condensing tower or chimney before
named.
If it is desirable that the gases from the chamber A and the materials
contained in the furnace B should mix or combine with the gases evolved
from the decomposing pot O, economy of fuel will result, for in so doing 2
the heat produced will accelerate the working of the charge. In this
case the resulting gases or products after passing across the decomposing
pot O will pass through the flue N to the condensing tower or chimney
instead of through the flue M as previously described.
Should additional air be required in the flues and furnaces during the 3
passage of the gases the dampers L, L, are opened, and the necessary
supply thereby admitted and regulated.
Whilst this method of placing the fire-place chamber and arrangement
of flues, &c. is recommended for what is termed an t
open roasting
furnace," it is also considered a great improvement in the construction 3
of what is termed a "blind roasting furnace."

page_text: -
Having now described and particularly ascertained the nature of my
said Invention, and the manner in which the same is or may be used
or carried into effect, I would observe in conclusion, that what
I consider to be novel and original, and therefore claim as the Invention
secured to me by the herein-before in part recited Letters Patent is,
the arrangement and construction of the fire-place and flues so as to
admit of the fire being placed immediately beneath the bed of the
furnace used in the roasting of salt cake, nitre cake, sulphate of potash,
and other substances, and for the finishing of soda ash, substantially as
herein-before described and illustrated by the accompanying Drawings.
In witness whereof, I, the said Isaac Shimwell McDougall, have
to this my Specification set my hand and seal, the
day of October One thousand eight hundred and seventy-four.
ISAAC SHIMWELL MCDOUGALL. (L.S.)