IMPROVEMENTS IN OVENS OR KILNS FOR BURNING LIME, AND FOR FIRING BRICKS AND OTHER FICTILE ARTICLES
Year: 1878

page_text: PROVISIONAL SPECIFICATION left by Robert Thomson at the Office of the
Commissioners of Patents on the 23rd October 1878.
ROBERT THOMSON, of Glasgow, in the County of Lanark, North Britain,
Architect. "IMPROVEMENTS IN OVENS OR KILNS FOR BURNING LIME, AND FOR
FIRING BRICKS AND OTHER FICTILE ARTICLES."
This Invention has reference to a new or improved construction and arrangement
of ovens or kilns and their furnaces and flues, and mode of working the same for
the burning or calcining of lime, chalk, and other limestones, earths, or materials,
or for the burning or firing of bricks or carthenware articles, all in a more effectual
or efficient manner, with less waste of material and greater economy of fuel and
time of the attendants, than by such kilns as heretofore constructed and used.
And the nature and novelty of the Invention consist, first, in the construction of
each kiln and the arrangement of its fires, flues, and dampers singly and combined
in groups or sets of two or more kilns, for being filled, worked, or fired and
discharged either individually and intermittently, or continuously one after the
other in succession. Each oven or kiln is formed in plan or horizontal section with
a straight thick or double wall in front over the furnaces, which may be one, two,
three, or more in number and of a usual construction, fired from the front below
the level of the arched filling and discharging or emptying oven door, formed on a
level with the outer ground. The sides of this kiln are also formed with straight
rectangular corners and double walls running back from the front wall and back
end of the furnaces, converging in curved. or semicircular form at the back end to
an outlet, or it may be an inlet flue in the centre, controlled by a back damper,
and also formed with an arched roof or top across the whole oven in longitudinal
section springing from the top of the front furnace and door wall to the back flue
wall. The inside of these walls and arched top are lined or formed with fire-brick;
and the hollow spaces between the double walls are filled with sand, furnace ashes,
or other equivalent suitable non-conducting material; and a round or other shaped
hole fitted with a closing lid or door is formed in the upper part of the arch for
filling in the last of the lime or other material to be burned in this part of the kiln
chamber above the front filling and emptying door, which is formed of a thin

page_text: counterbalanced iron frame filled with fire-clay tiles or blocks, thoroughly closed or
luted with fire-clay outside, and raised and lowered in a grooved frame and slot
fitted or formed in the front thick wall over the furnaces, which are strengthened
by cast-iron plates and binders and long tie bolts, carried back inside or outside of
the side walls and secured to cross walls, to strengthen the lower-part-or-whole
brick structure, particularly when two or four of these are erected in a rectangular
group or set, as preferred for continuous and sequential use. In this case the stalk
-or-chimney-is-erected preferably in the centre equi-distant from all the kilns,
which are placed with their back curved and arched ends and back damper flue
towards.and.opposite.each other, so that the currents of heated gases enter and
pass out through a common transverse main flue leading to the chimney direct by
a separate damper or another flue to either of the other kilns by their back
damper and flue through below the chimney-or-past-the-side-of-it-when-these-are
worked by the heat from their furnaces in a sequence after each other, cooling,
emptying, and filling the kiln previously burned and shut off from the others by
its back damper. The floor of each kiln is preferred to rise in an incline from the
back end or bridge of their fuel burning and heating furnaces to the lower part of
their back outlet flue and damper, and the lime is built in large lumps in rows, so
as to leave open lower heat channels or flues back about two-thirds or so from the
furnaces towards a semicircular vertical wall and chamber or well formed also by the
lumps of lime in front of or near the back outlet or inlet flue, the lime being built
over these distributing heat channels up to the height of the doors, and then above
that, through the upper charging doors in the arch roof, to the top thereof; the
heat thus conveyed back through the channels from the furnaces passes up through
the whole mass of lime above, thence converging down and sideways by the arched
top and converging sides to the vertical semicircular back recess or well through
the outlet flue and damper, either direct to the chimney when working the kilns
singly, or direct into the kiln opposite it through its back flue and damper when
worked in succession, so as to cause the waste or escaping heated gases from the
first kiln to pass up from the back recess to the furnace end of this second kiln,
thence out through flues controlled by dampers in the front wall to the chimney by
upper longitudinal side flues between the kilns when there are four or more in the
set.
When the lime in the first kiln has been sufficiently burned or calcined its
back damper is let down, and the dampers in the front wall flues of the second kiln
also closed, then the furnaces in this kiln are lighted and set to work, so as to burn
the lime in this kiln, all as described in reference to the first kiln, leading the
heated gases through the unburned parts and in the reverse direction to that in
which the gases were directed in the first instance from the first or preceeding kiln;
the gases from this second kiln passing off by its back damper and under flue
below or past the chimney to one or other of the other kilns of the set, so as to be
utilized in heating and partially calcining the lime therein before lighting its
furnaces, all as described in reference; to the second kiln; and so on in succession
through the whole set or series of ovens or kilns in a sequential and continuous
manner; thus utilising the waste heated products of combustion from the one kiln
for heating or preparing the lime or materials to be burned in the next succeeding
kiln by the direct action of its fuel furnaces, thereby saving much fuel while
burning the whole uniformly; the first furnace being discharged and again filled
ready for being heated in sequence by the time the others are burned. Thus it
will be seen from the arched construction of the kiln that the flames and gases
from the front furnaces are converged and concentrated as they get weaker towards
the back and exit damper flue, passing quite in the opposite direction and current
course through the kiln from that in which the inlet heated gases or products of
combustion from the other or previously burned kiln, so as to pass equally through
and thoroughly burn the lime in all the parts, and leave no corners for the
collection of carbonic acid gas, where the lime is imperfectly burned in other
constructions of kilns. This arrangement enables one kiln to be emptied while
another is being fired, and a third receiving the waste beat, and a fourth being

page_text: filled and prepared for burning. The limestone or quick lime thus burned is of a
very pure and superior quality, being perfectly free from all coal, ash, or other
impurities usually resulting in the ordinary mode of burning limestone with the
coal or fuel mixed through it; great saving of time and labour being also effected
by this new or improved mode and means of burning limestone by not requiring to
break it up into small pieces as heretofore; while the attendant can as easily attend
to a whole set of furnaces as to one furnace, no time being lost in waiting on,
being constantly employed in filling and emptying the kilns when not required at
the furnaces. The upper part of the building or whole set of kilns may be formed
into one or more heating and drying chambers, for storing and keeping the burned
lime, or for drying purposes generally, such as for the drying of bricks or earthen-
ware previous to firing them, thus utilising much of the heat which would other-
wise be wasted or lost.