IMPROVEMENTS IN STEAM BOILERS
Year: 1879

page_text: LETTERS PATENT to Thomas Hirst Thwaites, William Henry Thwaites,
Alexander Stewart, and John Sturgeon, all of Bradford, in the County of
York, Engineers, for the Invention of "IMPROVEMENTS IN STEAM BOILERS,"
PROVISIONAL SPECIFICATION left by the said Thomas Hirst Thwaites,
William Henry Thwaites, Alexander Stewart, and John Sturgeon at the Office
of the Commissioners of Patents on the 25th September 1879.
THOMAS HIRST THWAITES, WILLIAM HENRY THWAITES, ALEXANDER STEWART,
and JOHN STURGEON, all of Bradford, in the County of York, Engineers. "IMPROVE-
MENTS IN STEAM BOILERS."
This Invention has for its object the construction of a steam boiler for the
purpose of burning various kinds of rubbish, such as street and market sweepings
and other refuse of towns, from ashpits, &c., various kinds of manufacturers' waste
such as can be burnt, diseasead meat, cattle market refuse, straw, &c., so as to avoid
or to greatly economise the use of coal for fuel.
For this purpose we construct a boiler with a short flue or passage at or near the
centre, and passing downwards from the top of the boiler direct into the fire box
above the grate, and we let down the rubbish or other fuel through this opening
into the fire place or furnace instead of feeding the fires through the ordinary doors
at front. We arrange the grate bars so as to incline down from the middle of the
boiler under the feeding flue or tube towards the ordinary doors, which are used
only for clearing out the clinkers. Over the feeding tube we place a platform to
to receive the rubbish or other fuel intended to be burnt. From the top of the fire
box we carry a flue tube or a series of flue tubes leading into the main flue or into
a common flue chamber communicating with the main flue, the air being admitted
through the grate bars or through openings in the clearing doors. Inside the
common flue-chamber we place a hopper, by preference of the shape of an inverted
cone or funnel, leading into the feeding tube of the boiler, and closed at the bottom
by means of a conical bell, such as is commonly used for a smelting furnace or
cupola, and connected by a rod and chain to a lever or pulley outside, so that it
can be raised or lowered at will, thereby opening or closing the bottom opening of
the hopper. The rubbish or other fuel to be burnt is placed in this hopper, where
Prine fidi

page_text: it gets thoroughly dried by the heat of the flue chamber surrounding it, and it can
be let down into the furnace when so dried in such quantities and at such times as
may be required by raising the conical bell and so opening the bottom of the
hopper. The sides of the funnel shaped hopper are either partly or entirely grated,
so as to allow the damp vapour given off from the rubbish to be carried away with
the draft by the chimney, and thus facilitate the drying process, and the top is closed
by a door or doors. By this means the waste heat in the flue is employed to dry
the fuel and bring it into better condition for use, and this also applies to other
kinds of fuel besides the refuse of towns, &c.
In applying our Invention to a vertical boiler the feeding tube occupies the place
where the chimney is usually placed, joining into the top of the fire box. To carry
off the gases of combustion we apply a number of flue tubes (serving also as stays)
leading from the top of the fire box into a common flue-chamber or smoke-box fixed
on the top of the boiler around the feeding tube and funnel shaped hopper, and
from this smoke box the gases pass away into the chimney. The upper surface of
the smoke box we in some cases utilize as a drying floor. The grate bars form a
circular cone raised in the centre, and we also apply an adjusting screw or other
equivalent contrivance, by which the inclination of the grates may be regulated by
raising or lowering the centre. Any convenient number of clearing doors might be
arranged round the boiler.
In applying our principle to a horizontal cylindrical internal flued boiler we place
a clearing door at each end, the fire bars slanting opposite ways from the middle
outwards to the doors. We carry two or more internal flues below the water line
and lengthways with the boiler so as clear the central feeding tube, and we connect
these flues by means of short tubes with the top of the main flue or fire box. One
or more openings are made through each side of the boiler into the longitudinal
internal flues, through which the gases pass from the latter into the outside side
flues, and thence in the ordinary way to the main flue and the chimney. A double
flued boiler may be thus applied, fired underneath, being fitted with a number of
short tubes forming a communication between the flues and the fire space, the
feeding tube passing between the two flues.
In the case of a single flued boiler fired underneath the flue is enlarged at the
middle of the boiler where the feeding tube passes through it.
All the arrangements above described for drying the fuel previous to its entering
the furnace are applicable to these cases of horizontal boilers.
These arrangements enable us to apply a very considerable amount of grate
surface to the boiler, well adapted for the burning of rubbish, and they also afford
a convenient mode of drying the latter and of feeding the fires. The same principles
can be applied in a slightly modified form to other forms of boilers besides those
described, and are applicable for burning coal and other fuels as well as rubbish.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Thomas Hirst Thwaites, William Henry Thwaites, Alexander Stewart,
and John Sturgeon in the Great Seal Patent Office on the 24th March 1880.
THOMAS HIRST THWAITES, WILLIAM HENRY THWAITES, ALEXANDER STEWART, and
JOHN STURGEON, all of Bradford, in the County of York, Engineers. " IMPROVE-
MENTS IN STEAM BOILERS."
This Invention has for its object the construction of a steam boiler for the
purpose of burning various kinds of rubbish, such as street and market sweepings
and other refuse of towns, from ashpits, &c., various kinds of manufacturers' waste,
such as can be burnt, diseased meat, cattle market refuse, straw, &c., so as to avoid,
or to greatly economise the use of coal for fuel.
For this purpose we construct a boiler with a short flue or passage, at or near
the centre, and passing downwards from the top of the boiler direct into the fire
box above the grate; and we let down the rubbish or other fuel through this opening
into the fire place or furnace, instead of feeding the fires through the ordinary doors
at front. We arrange the grate bars so as to incline down from the middle of the
boiler, under the feeding flue or tube, towards the ordinary doors which are used
only for cleaning out the clinkers. Over the feeding tube we place a platform to
receive the rubbish or other fuel intended to be burnt. From the top of the fire
box we carry a flue tube or a series of flue tubes leading into the main flue or into
a common flue chamber communicating with the main flue, the air being admitted
through the grate bars or through openings in the cleaning doors. Inside the
common flue chamber we place a hopper, by preference of the shape of an inverted
cone or funnel leading into the feeding tube of the boiler, and closed at the bottom
by means of a conical bell such as is commonly used for a smelting furnace or cupola
and connected by a rod and chain to a lever or pulley outside, so that it can be
raised or lowered at will, thereby opening or closing the bottom opening of the
hopper. The rubbish or fuel to be burnt is placed in this hopper, where it
gets thoroughly dried by the heat of the flue chamber surrounding it, and it can be
let down into the furnace when so dried, in such quantities, and at such times, as
may be required, by raising the conical bell, and so opening the bottom of the
hopper. The sides of the funnel shaped hopper may be either partly or entirely
grated, so as to allow the damp vapour given off from the rubbish to be carried
away with the draft by the chimney, and thus facilitate the drying process, or the
hopper can be made without perforations, and the vapour exhausted therefrom, the
top is closed by a door or doors. By this means the waste heat in the flue is
employed to dry the fuel and bring it into better condition for use, and this also
applies to other kinds of fuel besides the refuse of towns, &c.
In applying our Invention to a vertical boiler, the feeding tube occupies the
place where the chimney is usually placed, joining into the top of the fire box.. To
carry off the gases of combustion, we employ a number of flue tubes (serving also
as stays), leading from the top of the fire box into a common flue chamber or smoke
box fixed on the top of the boiler around the feeding tube and funnel shaped hopper;
and from this smoke box the gases pass away into the chimney. The upper surface
of the smoke box we, in some cases, utilize as a drying floor,
The grate bars form a circular cone raised in the centre, and we also apply an
adjusting screw, or other equivalent contrivance, by which the inclination of the
grates may be regulated by raising or lowering the centre. Any convenient number
of cleaning doors might be arranged round the boiler.
In applying our principle to a horizontal cylindrical internal flued boiler, we
place a cleaning door at each end, the fire bars slanting opposite ways from the
middle outward to the doors. We carry two or more internal flues below the
water line and lengthways with the boiler,.so as to clear the central feeding tube;

page_text: and we connect these flues by means of short tubes with the top of the main tube or
fire box. One or more openings are made through each side of the boiler into the
longitudinal or internal flues, through which the gases pass from the latter into the
outside side flues, and thence in the ordinary way to the main flue and the
chimney. A double-flued boiler may be thus applied, fired underneath, being fitted
with a number of short tubes forming a communication between the flues and the
fire space, the feeding tube passing between the two flues.
In the case of a single-flued boiler, fired underneath, the flue is enlarged at the
middle of the boiler, where the feeding tube passes through it.
All the arrangements above described for drying the fuel previous to its entering
the furnace, are applicable to these cases of horizontal boilers.
These arrangements enable us to apply a very considerable amount of grate
surface to the boiler well adapted for the burning of rubbish, and they also afford
a convenient mode of drying the latter and of feeding the fires. The same
principles can be applied in slightly modified form, to other forms of boilers
besides those described, and are applicable for burning coal and other fuels as well
as rubbish.
Such being the nature and object of our Invention, we will now describe
the particulars thereof, which will be fully understood by the following description,
aided by the annexed Drawings. In all the Figures similar letters represent
similar parts.
The boiler is indicated by the letters A, A; the furnace by B; C, the feed
hopper; D, the smoke box surrounding the hopper; E, the central feeding shaft
through which the fuel passes from the hopper into the furnace B; F, balanced
conical bell valve by which the mouth of the feeding shaft E is closed or opened;
G, fire bars; H, H, flue tubes leading from the fire box B to smoke box D; R is
branch or flue leading from the smoke box to the chimney flue; J, lever arm for
working conical valve F; T and S, balance weights for the said lever J; L, lid or
door by which the fuel is fed into the hopper; M, M, doors placed at intervals
round the boiler for clearing out ashes and clinkers; N, central support for fire bars
provided with cam teeth on top; O, worm and worm wheel for revolving central
support so as to tilt the bars G by means of the cam teeth on top of the support N
and thereby agitate the fuel and prevent clinkering; P, upper platform for
reception of the refuse fuel and for feeding hopper. The flue to chimney passes
under the floor of the platform P, which is thus heated by the hot air on its way to
the chimney, and thus the heat is utilized to assist in drying the rubbish before
entering the feed hopper; Q, pillars supporting the upper platform P. From the
upper surface of the refuse in the hopper and on the drying floor any ammonia in
the refuse would be evaporated at a low temperature, and may be drawn off
through a suitable outlet, as for instance at U, by means of an exhauster or fan,
and if required such ammoniacal gases may be condensed and the ammonia
recovered therefrom; this will prevent any injury being done to the boiler proper
by the ammonia. As the refuse descends lower in the hopper it attains a greater
degree of heat, and the lighter hydro-carbons will then be liberated. These being
combustable gases we allow to pass through perforations in the bell valve F', down-
wards through the feed shaft E, and through the red fire on the way to the chimney
in the direction of the arrows, whereby a thorough combustion is obtained and
smoke prevented; any noxious organic matter will be destroyed, and the danger of
contaminating the atmosphere prevented.
Instead of the large flue tubes H, as shewn in Figure 1, a larger number of
smaller tubes may be employed containing a number of smaller cross tubes. Cross
tubes may also be applied to the fire box in the ordinary way, but a little off the
centre, so as to leave a clear way for the refuse to descend into the furnace.
Figure 2 is a modification shewing the boiler shell made parallel with the flue
tubes H, H, bent at the top and attached to vertical shell.
Figure 3 is another modification, the boiler being made parallel independent of
the fire box, and surrounded or encased in brickwork; the flue tubes H, H, are

page_text: bent at the top through which the heated gases pass from the furnace to the flue
formed in the brickwork surrounding the boiler, thence to the smoke box D and
chimney.
Figure 4 is a horizontal section, and Figure 5, a cross section of a horizontal
boiler arranged on our principle. The feed hopper is placed in the centre, and the
feed shaft E passes through the boiler leading to the fire bars G, G, which slant
from the centre downwards towards the cleaning doors M, M. The flame passes
under the boiler to flue openings right and left at X and X¹, thence in the direction
of the arrows along the sides of the boiler to the smoke box D, through the flue R
to the chimney.
Figure 6 is a cross section shewing a modification in which the refuse fuel is
passed down openings formed in the brickwork setting at the middle of the boiler,
and on each side thereof on to the fire bars which are sloped as in Figure 4; the
flame passes through short flues in the boiler, as shewn at Z into a main flue Y,
where the flame from the opposite ends of the boiler will meet and pass out through
the chimney flue R in the middle of the boiler.
We wish it to be understood that although this class of boiler is designed for the
combustion of rubbish, it is nevertheless equally adapted for burning low quality or
ordinary fuel.
Having thus fully described the nature and particulars of this our Invention
together with the manner in which the same may be performed or carried into
effect, we would have it understood that what we claim as our Invention is,-
The general arrangement and combination of the various parts of steam boilers,
substantially in the manner and for the purposes hereinbefore described and
illustrated by the accompanying Drawings, more especially as regards the central
feed, the arrangement of the flue tubes providing numerous outlets, the hopper
or drying chamber, the conical or slanting fire bars, the mode of agitating same,
extracting of the amoniacal gases, the burning of combustable gases given off in
drying the fuel, and consumption of smoke.
In witness whereof, I, the said Alexander Stewart, for and on behalf of myself
and the said Thomas Hirst Thwaites, William Henry Thwaites, and John
Sturgeon, have set my hand and seal, this Twenty third day of March,
in the year of our Lord One thousand eight hundred and eighty.
Witness,
JOHN WAUGH,
Engineer & Patent Agent,
Bradford,
Yorks.
ALEXANDER STEWART. (L.S.)