IMPROVEMENTS IN EFFECTING THE COMBUSTION OF FUEL AND IN THE CONSTRUCTION OF FURNACES THEREFOR
Year: 1875

page_text: PROVISIONAL SPECIFICATION left by Charles Frédéric Kuhlmann at
the Office of the Commissioners of Patents, with his Petition, on
the 7th April 1875.
I, CHARLES FRÉDÉRIC KUHLMANN, of Lille, France, Manufacturer,
do hereby declare the nature of the said Invention for "IMPROVEMENTS
IN EFFECTING THE COMBUSTION OF FUEL AND IN THE CONSTRUCTION OF FURNACES
THEREFOR," to be as follows:-
-
My Invention relates to improved methods of and apparatus for
effecting the combustion of close burning coal, anthracite, coke, and other
fuel without the use of a grate, the Invention being applicable to
furnaces for concentrating soda lyes, heating steam boilers and other
furnaces generally.
I have been led to remark in common with others the fact in
attempting to obtain the greatest possible consumption of smoke a
considerable excess of air is admitted in furnaces whereby the expenditure
of fuel is greatly increased.

page_text: of
salt in order to convert the same into sulphate of soda and hydrochloric
acid. Of these furnaces there are some so arranged as to cause the
heated air to react directly on the sulphate of soda for the purpose
completing its manufacture, so that the hydrochloric acid evolved
remains mixed with the gases of combustion produced in the furnace,
the condensation of which acid is rendered the more difficult the greater
is the proportion of air mixed with it.
In order to avoid the introduction of an excess of air in the fire-places
of these furnaces burning coke or close burning coal, I close the ash-pit
with a cast-iron door and allow the air to enter only through the fissures
around it, or one or two small holes drilled in the door, and in this
manner I have obtained considerable economy in fuel and much roadier
condensation of the acid vapors. One only objection to this method was
the liability of the fire-bars to melt, which necessitated the placing of
cast-iron vessels filled with water at the bottom of the ash-pit.
Following on these experiments I have been led to dispense with the
fire-grate and burn the fuel on a kind of platform formed of fire-brick
arches, or preferably of slabs of stone or pottery-ware capable of with-
standing a high temperature, the shelves or platforms being disposed onc
above the other, at from five to six inches apart.
Iron doors are provided at one side of the furnace at which to feed
the fuel on to the uppermost of these shelves, and to make it descend
from shelf to shelf by openings left alternately at opposite ends of the
slabs, whereby the gases are brought in contact with the whole surface
of fucl in combustion, the ashes being withdrawn from the bottom.
I
Air is admitted to the furnace by the fissures around the doors and
through a few holes made in the doors of the lower shelves if necessary;
say if necessary, because even without these holes the air entering at
the fissures around the doors is generally sufficient to prevent the
formation of oxide of carbon in the furnace. In using the furnace 1 first
heat the four or five combustion chambers by igniting therein either
wood or cokc.
•
The draught may be reversed and follow the same direction as the fuel
when the necessity for utilizing the heat renders it imperative, but only
then unless indeed caking coal be used.
In applying my Invention to furnaces for the manufacture of sulphate
of soda, the heated air is directed into that part of the furnace known as

page_text: 'the calciner, and thence goes to heat the evaporating vessel or boller in
which the salt is mixed with the sulphuric acid, and which I place by
preference over the crown of the calciner with the object of economizing
space in the works.
The acid vapors from the evaporator and calciner are condensed
separately as usual. The great objection attending furnaces constructed
with tiers of shelves as above described, is owing to the rapidity with
which the fire-clay slabs are worn out where great heat is employed, as
in the case of reverberatory furnaces; and to obviate this, I in some cases
replace the tiers of slabs by a single furnace chamber, like that of a
running kiln used for calcining limestone, or like that of a cupola
furnace used in metallurgical operations. In any case the furnace
chambers are surmounted by an arch of fire-brick, the hot air passing
out laterally, and being conducted beneath the substance to be heated,
or employed for heating a steam boiler or other apparatus. The above
furnaces may also be employed for roasting sulphurous ores. The fucl
most suited for both the above systems especially as regards economy
are close burning coal, anthracite coke, cinders, and even peat or small
coke agglomerated with clay. It is supplied through a lateral opening
beneath the arch. The ashes are extracted from the bottom of theso
furnaces in a similar manner to hime from limo kilns; the current of air
passes through these ashes, which air may be admitted by flues at
different levels in the sides of the furnace and governed by dampers, tho
said flues also affording facilities for clearing any obstruction to the
downward course of the fuel. These lateral flues should be so regulated
as to prevent the admission of too great an excess of air, although a
slight excess is needed in order to prevent the formation of carburetted
hydrogen or oxide of carbon. I have represented in the accompanying
Drawings soveral furnaces without grates as examples of the mode of
carrying out the Invention.
Figure 1 shows a longitudinal section of an evaporator for drying
salts of soda, provided with a furnace composed of slabs, Figure 2 is a
horizontal section taken on line 1, 2, 3, 4; Figure 3, a front view;
Figuro 4 a transverse section on line 5—6; and Figure 5 a similar section
on line 7-8. The same letters of reference indicate like parts in all the
Figures. a, brickwork setting; b, evaporator; c, fire-clay slabs on which
the fuel is placed, d, flue leading direct to the chimney, and also
serving as manhole; e, damper; f, partitions for causing the products of

page_text: combustion to impinge on every part of evaporator b; g, ash-pit door
perforated for the admission of air.
Figure 6, shows a longitudinal section of a furnace for treating
sulphates, with which is combined a fire chamber with shelves or slabs,
and adapted for consuming close burning coal; Figure 7 is a horizontal
section on line 1, 2, Figure 1; Figure 8, a transverse section on line 3, 4,
Figure 1; Figure 9, a front view; Figure 10, a horizontal section on
line 5, 6, Figure 1; and Figure 11, a part transverse section of the fire
chamber. a, brickwork setting; b, evaporator; c, slabs on which the
fuel is placed; d, ash-pit door perforated for the admission of air.
Figuro 12 shows a longitudinal section of another arrangement of
furnace for close burning coal, which is fed in at door a, the ashes being dis-
charged at an opening 6 into a pit, said opening being closed by a door
having small perforations for admitting air; c, working holes closed by
loose bricks. The perforations in door a and the openings & serve to:
admit an extra supply of air when required.