IMPROVEMENTS IN STEAM BOILERS AND BOILER FURNACES
Year: 1885

page_text: We, CHARLES ALBERT KNIGHT and GEORGE WILLIAM THODE, both of the
Babcock and Wilcox Company, Glasgow, in the county of Lanark, Engineers, do
hereby declare the nature of our said invention for "IMPROVEMENTS IN STEAM
BOILERS AND BOILER FURNACES," and in what manner the same is to be performed,
to be particularly described and ascertained in and by the following statement :-
The object of our invention is to obtain more perfect or complete combustion of
the fuel consumed in boiler furnaces, and to utilise in the highest degree possible
the heat evolved in such combustion. To this end we so construct the furnaces of
steam boilers that the gases evolved from bituminous fuel may, by properly uniting
with air, be raised to the high temperature due to chemical combination of the
gas and air within the furnace and before contact with the heating surfaces of the
boiler, and so that the intense heat thus obtained from perfect combustion may be
utilised, firstly, by radiation against the heating surfaces during the process of
combustion of the gases, and, secondly, by impact of the hot products of com-
bustion with such heating surfaces resulting in absorption of the heat by conduction
and convection.
We also arrange the heating surfaces of water-tube boilers fitted with such
furnaces, in such manner that a large proportion of the water tubes will be exposed
to the radiant energy of the gases consumed within the furnace, and that the
surfaces of the whole of the tubes may be exposed to the impact of the gases
flowing towards the chimney.
The accompanying Drawings illustrate our invention as applied in a furnace
adapted to a modification of the well known Babcock and Wilcox water tube
boiler. Figure 1 is a longitudinal_section showing our improvements both in the
boiler and in the boiler furnace. Figure 2 is a section through the boiler at the
line XX, and Figure 3 is a section through the furnace at the line Y--Y.
The furnace comprises a fire grate A, which may be of the ordinary form for
burning solid fuel, of which may be constructed as a gas-producer, the fuel being
retained by a bridge B over and beyond which is the combustion chamber C of
unusually large size in proportion to that of the fire-grate, the object being to
provide ample space and time for complete combustion of the gases rising from the
fuel on the fire-grate. The water tubes D which form the heating surfaces of the
boiler are fitted near the bottom of the combustion chamber, and they are connected
to end pieces communicating with a steam and water drum as in the ordinary,

page_text: type of Babcock and Wilcox boiler. The outlet E from the combustion chamber
is at the back end and below the boiler tubes. The crown of the combustion
chamber of the furnace is in the form of an arch, and is constructed of fire brick
or other refractory and heat-retaining material, as are also the side walls, in order
that when they become heated to incandescence they may serve as a regenerator
to intensify the heat of the gases evolved when fresh fuel is placed on the firegrate
and thereby promote their complete combustion, the heat of the crown and walls
being also radiated on the heating surfaces D of the boiler. The gases rising from
the firegrate mingle with air which enters by ports or openings G, conveniently
formed in the front or sides or in the top part of the furnace, the air being, by
preference, previously heated, by traversing conduits or passages formed over, or in
the crown or arch or in the side walls, and being either forced in by pressure or
drawn in by the furnace draught alone. The union of the hot gases and the air
results in the production of the intense heat due to chemical combination and
perfect combustion, and owing to the large size of the combustion chamber which
permits of the accumulation of the gaseous mixture, and to the position of the
chamber over the heating surfaces, such heat is transmitted to the heating surfaces
in the two stages before mentioned, namely, 1st by radiation and 2nd by actua!
contact with the heating surfaces of the boiler of the hot products of combustion
which flow through between the tubes D interposed between the combustion
chamber and the outlet E. The upper, series of the tubes D are disposed more
widely apart than the lower series which are fitted close together, the object of this
disposition being that the heat radiating from the incandescent gases in the
combustion chamber may have free access to the surfaces of a larger proportion of
the tubes, while the hot products of combustion in their descent and outflow may
come into close contact with all the tubes and more particularly with those which
are least subject to the influence of the radiant heat transmitted from the gases.
In lieu of using solid fuel within the furnace, gas may be admitted thereto to be
consumed in the furnace, or it may be produced within the furnace by converting
the fire grate into a gas producer of any well known form.
Figure 4 is a longitudinal section illustrating a modified arrangement of the
furnace and heating surfaces of a boiler of the Babcock and Wilcox type. In this
example a hanging bridge H depends from the arch or crown of the combustion
chamber C to the water tubes D. The outflowing products of combustion are
then carried through between the water tubes below the combustion chamber,
round a division plate H below the hanging bridge H, and up through the rear
part of the length of the tubes to the outlet E, which is in this case above and
beyon the tubes. The arrangement of the furnace is in other respects generally
similar to that of the furnace illustrated in figures 1, 2, and 3.
Having now particularly described and ascertained the nature of our said
invention, and in what manner the same is to be performed, we declare that what
we claim is
1. The improved construction and arrangement of boiler furnaces herein
described and illustrated.
2. That improvement in boiler furnaces which consists in locating the combustion
chamber over the heating surfaces of the boiler and the outlet for the spent gases.
below or beyond such heating surfaces in the manner herein set forth.
3. That improvement in the construction of boiler furnaces which consists in
forming over and beyond the fuel chamber, a combustion chamber of large
dimensions wherein the gases may freely mingle with heated air and may attain
the high temperature due to perfect combustion, and in forming the outlet from
such chamber below and beyond the water tubes or heating surfaces of the boiler
in order that such surfaces may be subjected to the influence of the heat transmitted
to them by radiation and of that due to actual contact of the outflowing gases as
herein set forth.
4. The construction of a boiler furnace and the disposition therein of the heating
surfaces of the boiler in such wise that the heat generated by combustion of the

page_text: fuel is transmitted to the heating surfaces in two stages, firstly, by radiation during
the process of combustion of the gases, and secondly, by conduction resulting from
contact with the products of combustion.
5. The arrangement or disposition of the heating surfaces of a boiler in combi-
nation with a boiler furnace in such a manner that the heating surfaces may be
subjected to the influence of the heat emitted by radiation during the process of
combustion of the gases within the furnace, and to that of contact of the products
of combustion in their outward course towards the chimney as herein set forth.
6. That improvement in the construction of water-tube boilers which consists in
disposing the water tubes at comparatively wide intervals apart in the upper series,
and more closely together in the lower series, substantially as herein described and
illustrated.