Improvements in Steam Boilers and their Furnaces.
Year: 1890

page_text: Date of Application, 11th Apr., 1890-Accepted, 17th May 1890
Improvements in Steam Boilers and their Furnaces.
I, EDWARD JAMES DUFF, 118 Ingleby Drive, Glasgow, in the County of Lanark,
North Britain, Engineer, do hereby declare the nature of this invention and in what
manner the same is to be performed, to be particularly described and ascertained in
and by the following statement, that is to say :-
This Invention has for its object to obtain increased efficiency with absence of
smoke in connection with steam boilers and their furnaces..
The Invention is applicable to various kinds of steam boilers, it is however shown
on an accompanying sheet of explanatory drawings as applied to a common type of
land boiler. comprising a horizontal cylindrical shell with two furnaces in flues
extending from end to end of the boiler. Figure, 1, is a front end elevation (but
with fire doors and some other parts removed) and figures, 2, and 3, are longitudinal
vertical and horizontal sections. In these drawings the same reference numerals are
used to mark the same or like parts wherever they are repeated.
The grate of each furnace of the boiler consists of a series of longitudinal tubes, 5,
of steel or other suitable metal, these tubes being inclined so as to be higher at their
inner ends and being fixed in outer and inner end castings, 6, 7, of steel or iron.
Access to the grate tubes, 5, for cleaning out or withdrawing them is given through
apertures in the end castings, 6, 7, at the sides opposite to the ends of the tubes, those
of the inner end casting, 7, being closed by screw plugs, 8, whilst those of the outer
or front end casting, 6, are closed by caps, 9, (not shown in figure, 1) fixed by bolts
securing them to internal cross pieces. Either the screw plugs, 8, or the caps, 9,
may be used for both end castings, 6, 7. Each inner end casting, 7, is connected
by a central vertical pipe, 1", to the interior of the boiler through the top of
the flue. tube, 11; and a hanging or depending bridge or wall, 12, of firebrick
The
(not shown in figure 1,) is fixed across the upper part of the flue tube.
outer or front end castings, 6, of the two furnaces are connected to curved
branches, 13, of a pipe, 14, communicating through the front end plate, 15, of
the boiler with the interior. The branch pipes, 13, are provided with downward
continuations, 16, which are fitted with stopcocks, (not shown) and are to be used for
blowing-off so as to, wash out the grate tubes, 5, whenever it may be thought desirable.
The arrangement of the pipes, 13, 14, is such as to allow of slight movements of the
parts of the grate which may be caused by variations of temperature without any part
being injuriously strained. In consequence of the front and back ends of the grate
tubes, 5, being connected respectively to lower and higher parts of the interior of the
boiler, a vigorous circulation of the water takes place through the grate tubes towards
their inner ends; and this circulation is further promoted by the inclination of the
grate tubes.
Beneath the grate tubes, 5, there is in each case a transverse partition, 17, and in
the space, 18, from this partition to the front end of the grate tubes air passes up
between the grate tubes and through the fuel lying upon them; but in the space, 19, at
the inner side of the partition, 17, the gases pass downwards between the grate tubes
and thence onwards along the flue. The fuel is placed on the grate tubes, 5, so as to
extend from their front ends inwards beyond the partition, 17, but not close up to the
hanging bridge, 12, a firebrick bar, 20, being placed across the grate tubes, 5, so as to
keep a space, 21, at their inner ends clear of fuel and so that a portion of the gases
may pass downwards between them without being obstructed by the fuel. With the
arrangements which have been described the gases from the fuel at the outer
part of the furnace are compelled to take a downward course at the inner part,
partly through some fuel, but chiefly through the space, 21, at the inner ends of the
grate tubes; and in consequence of this downward course of the fuel gases they pass
in close contact with the incandescent fuel (at the inner part of the furnace, and
1

page_text: their combustible constituents are thoroughly ignited and the production of smoke
prevented. By providing the comparatively free space, 21, at the extreme inner en
of the furnace for the downward passage of a portion of the ifuel gases, there
avoided the great resistance to the flow of the gases which has been the cause of
inefficiency .in .attempts to .make the whole of the fuel gases pass downwards
through fuel.
*The transverse partition, 17, beneath the grate tubes, 5, between the spaces, 118, 19,
is provided with a a door, 22, through which ashes may be withdrawn ; and if found
advantageous a regulated supply of air may be admitted through the partition.
Ordinary fire doors, 23, (not shown in figure, 1;) are fitted at the front ends of the
furnaces above the grate tubes, .5; and air may be admitted through regulated
openings in these doors.
The apparatus may be modified by arranging the space (21) at the inner end of
the furnace for the free passage of a portion of the fire gases, beyond the extreme ends
of the grate tubes (5) and in that case the said space having no tubes across it may be
reduced in size.
The air may be supplied by ordinary draught or by what is known as forced
draught.
Having now particularly described and ascertained the nature of the said Inven-
tion and in what manner the same is to be performed, I declare that what I
claim is :-
1. The combination of parts constituting the improved furnace and water-circulating
apparatus for steam boilers, the same being arranged and operating substantially
as herein before described.
2. In a steam-boiler furnace having a water tube grate, a hanging bridge or partition
closing the inner end of the space above the grate, a partition separating an outer part
of the space under the grate from an inner part communicating with the continuation
of the flue, and a space at or beyond the inner end of the grate for the free passage of a
portion of the fire gases, all in combination and arranged substantially as and.for the
"purposes herein before described.
Dated this Tenth day of April 1890.