IMPROVEMENTS IN FURNACES AND APPARATUS FOR EVAPORATING
Year: 1879

page_text: PROVISIONAL SPECIFICATION left by Alexander Melville Clark at the
Office of the Commissioners of Patents on the 4th October 1879. [A com-
munication from abroad by Felipe Perez de la Tega, of Havana, in the Island
of Cuba.]
ALEXANDER MELVILLE CLARK, of 53, Chancery Lane, in the County of Middlesex,
Patent Agent.
"IMPROVEMENTS IN FURNACES AND APPARATUS FOR EVAPORATING."
[A communication from abroad by Felipe' Perez de la Tega, of Havana, in the
Island of Cuba.]
These improvements relate especially to furnaces for burning bagasse or bagasse
with other fuel for evaporating purposes, but are applicable to furnaces generally.
The object of the Invention is to consume the smoke and gases thoroughly; to
aid the combustion of slow burning fuel, such as wet bagasse, by using with it a
quick burning fuel; to permit the keeping of a small fire when active operations are
suspended; and to prevent the accumulation of carbonised fuel in the ash pit of the
furnace.
In the improved furnace there are three grates, a central grate with a smaller
one at each side and on a lower level. Above the side grates the fire chamber is
formed with arches, which being intensely heated by a quick fire on the side grates
the smoke and gases are quickened to a rapid combustion. The grate surfaces are
formed with a solid or blind portion at the back, on which the carbonized bagasse
or other fuel collects and is consumed; and beneath the furnace is an arched
passage connecting with the ash pit and outer air at the side of the furnace,
whereby the ash pit space is kept cool, and danger from fire being driven out by
back pressure is prevented.
The Invention also relates to an evaporating pan, having a rounded bottom and
tubular flues, specially adapted for sugar manufacture as hereafter described. The
furnace will be built of brick, in suitable proportions of length and width; it is
formed with the fire chamber and ash pit at the front and escape flue at the rear.
The fire chamber as above mentioned is arched above the side grates, and drawn in
at the back to the bridge wall, so that the space for escape of the products of
combustion is about the width of the central grate. The pan or boiler extends from

page_text: the front wall of the furnace to near the rear wall, and the space between the
latter and the rear of the boiler is divided by a horizontal partition, which causes
the products of combustion to return to the front and back again by the tubular
flues of the pan before their final exit. The front wall is formed with a space into
which the tubes open, a door permitting access thereto. The front wall is also
provided with openings and doors for giving access separately to the grates in
firing. The ash pit divided by walls running lengthwise, so that there is a space
for each grate, which spaces open at the rear to an arched passage beyond the
grate, into which the ashes from beneath each grate can be raked.
At the rear side of this passage is another arched space or passage, opening from
one side of the furnace, and connecting at the opposite side with an upwardly opening
flue. The latter space or cross passage gives access beneath the furnace, furnishes
the air for draft, and maintains a current of air which cools the ashes; doors may ho
fitted for closing the openings to cross passage space when required. Hitherto in
burning bagasse the fuel becomes carbonized from an insufficient supply of air, and
falling into the ash pit is there ignited, so that the grates and bearers are rapidly
burned out. Another difficulty has been (especially where high winds prevail)
that the fire is forced backward through the draft openings in long sheets of flame,
which ignite the accumulations of bagasse, and cause a general conflagration. The
construction above described obviates these difficulties. The carbonized fuel can
be pushed upon the blind surfaces, and will be there gradually consumed; the
space beneath the grates may be kept clear of refuse and the refuse cooled. The
furnace has an ample supply of air, and in case of back drafts the pressure is
equalised by the arched cross passage being open at both ends.
Heretofore if the bagasse fuel was too wet to burn, a more expensive fuel, such as
coal, had to be used. By the use of the triple grates a fire of wood or coal can be
kindled upon the smaller side grates and the wet bagasse placed on the centre grate,
where it will be dried and consumed. The arches above the side grates will become
highly heated, and the smoke coming in contact therewith will be ignited and pass
in hot flames over the bridge wall. The triple grates are also advantageous for
keeping up a limited amount of heat and small pressure of steam by a fire of slow
burning fuel on the smaller grates during the night, so that in the morning active
work may be quickly resumed by placing the lighter fuel on the main grate. This
furnace is especially useful for sugar evaporating, and can be used with open or
vacuum pans. By using pans or boilers with the return flues, as hereafter described,
the heat is utilized to the greatest extent, and at least half less fuel required than
heretofore to perform the same work. The pan is formed with a curved or semi-
circular bottom, inclined sides and ends, the sides and ends being fitted at their
upper edges with a ledge or flange, by which the pan is supported on the furnace.
The tubular flues extend through the central space of the pan lengthwise thereof,
and open through the ends, to which the flues are attached in any desired manner.
The supporting ledge of the pan is turned upward at its outer edge, and at the inner
edge there is also a flange, so that a trough is formed around the pan. The inner
side of the trough may be formed by a continuation of the sides, and at the front of
the pan for about one third the length, where the ebullition is greatest this edge is
made higher to retain the scum that boils over into the trough. At the back of
the pan is a pipe for conveying away the liquid thrown out with the scum and a
pipe for emptying the pan.
The pan is to be fitted in connection with the furnace, so that the products of
combustion first pass beneath the pan to the rear, then forward through the lower
tubes, and back again through the upper tubes to the escape flue. The heated air
and gases pass beneath pan to the chamber at the rear end of the pan, which
chamber is divided by the horizontal plate separating the lower flues from the
escape flue; the tubes open into the space in the front wall of the furnace, and by
this construction the circulation described is obtained. The pan is set into the

page_text: furnace, so that its bottom and a considerable portion of its sides are exposed to the
direct heat from the fire chamber. This is more readily accomplished by the round
bottom pan, and a large extent of heating surface thereby obtained. In operation
the syrup will be highly heated, and a rapid circulation is set up, which prevents
incrustation, and throws off the foreign matters into the scum trough, and the pan
is adapted for use for evaporating purposes generally where a rapid operation is
desired.