Improvements in Tubulous Steam Generators.
Year: 1891

page_text: Date of Application, 5th Oct., 1891
Complete Specification Left, 5th July, 1892-Accepted, 24th Sept., 1892
PROVISIONAL SPECIFICATION.
Improvements in Tubulous Steam Generators.
[ BENJAMIN HOWARTH THWAITE of 37 Victoria Street Liverpool in the
County of Lancaster, Civil Engineer do hereby declare the nature of this invention
to be as follows:-
The essential features of my invention are as follows, the elements constitute a
vertical type of tubulous steam generator.
In the upper part of such generator I provide a cylindrical steam and water
vessel or drum, through which and vertically, 1 pass a tube or tubes preferably of a
diameter of 24 ins. but any usual size or diameter of tube may be employed. Attached
to the vertical side of this vessel, and partly above and partly below the water
level, I provide small water tubes of an internal diameter preferably not exceeding
one inch. Part of these small tubes are attached at a level above the water in
the drum and the remainder of the small tubes join the drum at a level below the
water.
The lower ends or terminations of these tubes, I connect to a circular water
cylinder or circular pipe, which acts as a collector and distributor, and encircles or
embraces the lower structure of steam generator constituting the heat production
part or furnace.
The small water tubes connecting the upper steam and water drum with the
lower circular pipe collector are not by preference, connected in a straight line,
although in some applications I may use a straight line system or an approach
thereto, but I usually curve' each small tube around, in a horizontal plane once
or twice or even oftener so as to fully expose its heating surface to the flame of
combustion.
The horizontal curved part of each small tube is so arranged that it superposes
another forming a vertical nest of small circular tubes through which the flame of
combustion flows. The water flows (ascensionally and with an enormous rate of
velocity, through the small tubes, descending through a larger side and vertical
main, which is of such a diameter as to permit the descensional flow to be com-
paratively very slow.
This downward flow main constitutes a depositing tube or chamber in which
all the suspended matter settles in a pocket at the foot and can be readily
blown off.
The upper part of this vertical downflow main is continued up above the water
level, and forms a steam dome, and in this upper part of the downflow main I fix
the safety mountings.
Surrounding the steam dome I provide a jacket for the passage of the waste
gases to the chimney, which latter I prefer to form in the shape of an inverted
cone in the interior of which I provide a steam jet to induce a flow or powerful
aspiration effect.
I may provide the top or terminal of this aspiratory chimney with a water seal,
through which I may force the products of combustion, providing a bell cover
arrangement that on being lifted allows the waste gases to freely escape.
The heat producing part of steam generator I construct as follows:-
I provide a refractory lined chamber preferably of a larger diameter than the upper
cylindrical steam dome and of such internal proportions as to enable a considerable
depth of fuel to be maintained. I also provide a closed-in ash-pit, having special
cross-bar clinker doors, and provided with a steam jet air injector by which a blast
of air and steam is established under the grate.
Over the level of the fuel I provide a series of air tubes connected to an

page_text: annular air jacket which I form all round the small or water tube part of
generator.
The aspirator chimney previously described, draws or aspires the air in an
ascensional direction through the outer lining or air jacket into the air tubes where
it is distributed to the gas, generated and existing over the fuel, in what is
practically a gas generator.
By regulating the steam jet air blast under the grate and the aspiratory
effect of the steam jet in the chimney, absolutely perfect combustion can be
secured.
The flow of air through the air jacket reduces the loss by side radiation and cools
the atmosphere around the generator.
The upper steam and water cylinder is partly supported by the vertical downtake
pipe and a column support fixed opposite this downtake so that the air jacket, and
an inner iron cased and refractory lining can be removed to enable a stopped up or
otherwise defective tube to be cut out or be replaced.
The connecting joints at both ends of small tubes that is where they join the
steam and water cylinder at one end and the water collection pipes at the other are
all externally exposed and accessible.
The method of attachment is similar to that shown in my Patent No. 12093,
dated September 7th 1887.
Part of connections to upper steam and water drum are made as already described,
below the working water level so that the circulatory flow commences immediately
heat is applied.
In order to prevent priming I provide a diverting plate by which the ascen-
sional flow of the bubbles is confined to the sides and does not promote general
priming.
The remainder of the small water tubes deliver their water above the water
in the steam and water cylinder, and the steam separates from the water in its
cascade descent from its tube inlet level to the water level in the steam and water
drum.
Dated 26th day of September 1891.
B. H. THWAITE.
COMPLETE SPECIFICATION.
Improvements in Tubulous Steam Generators.
1 BENJAMIN HOWARTH THWAITE of 37 Victoria Street Liverpool in the
County of Lancaster Civil 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:-
The essential features of my invention are as follows. The elements constitute
a vertical type of tubulous steam generation.
In the upper part of such generator, I provide cylindrical steam and water
vessel, or drum, through which, and vertically, I pass a tube or tubes, preferably,
of a diameter of 21 inches, but any usual size or diameter may be employed.
Attached to the vertical side of this vessel, and partly above and partly below
the water level, I provide small water tubes, of an external diameter not exceeding
one inch. Part of these small tubes are attached at a level above the water in
the drum, and the remainder of the small tubes join the drum at a level below the
water.
The lower ends or terminations of these tubes, I connect to a circular water
cylinder, or circular pipe, which acts as a collector and distributor, and encircles or
embraces the lower structure of steam generator, constituting the heat production
part or furnace.
The small water tubes connecting the upper steam and water drum, with the
lower circular pipe collector, are not, by preference, connected in a straight line,

page_text: although, in some applications, I may use a straight line system, or approach
thereto, but I usually curve each small tube around, in a horizontal plane, once or
twice, or even oftener, so as to fully expose its heating surface to the flame of
combustion.
The horizontal curved part of each small tube is so arranged, that it superposes
another, forming a vertical nest of small circular tubes, through which the flame
of combustion flows. The water flows ascensionally, and with an enormous rate
of velocity, through the small tubes, descending through a larger side and vertical
main, which is of such diameter, as to permit the descensional flow to be com-
paratively, very slow.
This downward flow main constitutes a depositing tube, or chamber, in which
all the suspended matter settles in a pocket at the foot, and can be readily
blown off.
The upper part of this vertical downflow main, is continued up above the water
level, and forms a steam dome, and, in this upper part of the downflow main, I fix
the safety mountings.
Surrounding the steam dome I provide a jacket for the passage of the waste
gases to the chimney, which latter I prefer to form in the shape of an inverted
cone, in the interior of which, I provide a steam jet, to induce a flow or powerful
aspiration effect.
I may provide the top or terminal of this aspiratory chimney, with a water
seal, through which I may force the products of combustion, providing a
bell cover arrangement, that on being lifted, allows the waste gases to freely
escape.
The heat producing part of steam generator I construct as follows:-
I provide a refractory lined chamber, and preferably of a larger diameter, than
the upper cylindrical dome, and of such internal proportions, as to enable a
considerable depth of fuel to be maintained. I also provide a closed-in ash-pit,
having special cross-bar clinker doors, and provided with a steam jet air-injector,
by which a blast of air and steam is established under the grate.
Over the level of the fuel, I provide a series of air tubes, connected to an
annular air jacket, which I form all round the small or water-tube part of
generator.
The aspiratory chimney, previously described, draws or aspires the air in an
ascensional direction through the outer lining, or air jacket, into the tubes, where
it is distributed to the gas, generated and existing over the fuel, in what is
practically a gas generator.
By regulating the steam jet air-blast, under the grate, and the aspiratory
effect of the steam-jet in the chimney, absolutely perfect combustion can be
secured.
The flow of air through the air jacket, reduces the loss by side radiation, and
cools the atmosphere around the generator.
The upper steam and water cylinder, is partly, supported by the vertical
down-take pipe and column support, fixed opposite this downtake, so that the air
jacket and an inner iron-cased and refractory lining, can be removed, to enable
a stopped up, or otherwise defective tube, to be cut out, or be replaced.
The connecting joints at both ends of small tubes, that is, where they join the
steam and water cylinder at one end, and the water collecting pipes at the other,
are all externally, exposed and accessible.
The method of attachment is similar to that shown in my Patent, No. 12093,
dated September 7th, 1887.
Part of connections to upper steam and water drum, are made as already
described, below the working water level, so that the circulating flow commences
immediately heat is applied.
In order to prevent priming, I provide a diverting plate, by which the
ascensional flow of the bubbles is confined to the sides and does not promote general
priming.

page_text: The remainder of the small water tubes deliver their water above the water
in the steam and water cylinder, and the steam separates from the water in its
cascade descent from its tube inlet level, to the water level in the steam and
.water drum.
Before referring to the sheets of drawings that accompany and form part of
this Specification, I wish it to be distinctly understood, that I do not intend to be
confined to the exact details shown therein, as these may be modified, without
departing from the nature of my said invention.
Figure 1. on Sheet 1. of drawings, shews a complete vertical section of a steam
generator constructed according to my invention.
Figure 2. shews a plan of top of generator, &
Figure 3. is a plan in section through coil chamber.
Figure 4. shews an alternate arrangement of steam and water drum and chimney
connections.
The following are the characteristic elements of a steam generator constructed
according to my invention and as elucidated by the figures numbered from 1. to 8:-
First. A vertical fuel combustion chamber A. provided, having all the structural
attributes of a gas generator, or in which only the partial oxidation of the fuel is
effected, by which carbonmonoxide is produced instead of carbondioxide, and the
volatile hydrocarbons evolved are more fixed or stable.
The initial or partial combustion of the fuel on the grate is, preferably, produced
by merely the induction influence of an air aspirator, but, for this invention, 1
prefer to use a combination of a steam jet fixed in the chimney, and induction or
forced blast under the grate.
Second. A complete combustion zone B. is provided, supplied with air induced
to flow around or through an annular cavity or jacket surrounding a pipe coil
chamber C. in the flow of the air through this jacket, it abstracts the heat from
the sides, which would otherwise be wastefully radiated.
Third. A coil chamber C. in which a great part of the heat of combustion is
transferred to the water, flowing at enormous velocities through coils of pipes D.
of small internal diameter.
Fourth. An upper water and steam drum E. into which the water from the
coils is precipitated or fed, and which by its internal and central flue supplies the
surface for the transmission of the residual heat of the gases of combustion partly
to the water and partly to the steam.
Fifth. A downflow circulating water tube or vessel F. and suspended salt (or
calcareous and siliceous material) depositing pipe, through which the water slowly
descends from the water and steam drum E. into a circular formed main G. which
feeds the coil pipes D.
Continuous to the downflow circulating water tube or vessel F. there is a
lower limb, into which the suspended matters fall and accumulate, and can be
easily drawn off.
Sixth. An incandescent refractory flame distributor H. is formed above the
zone of initial or complete combustion, or above the level where the second air
supply meets the gas.
The direction of flow of the combustion is indicated by dotted arrows. The
direction of flow of air by dot and stroke arrows and the direction of the flow or
circulation of water, is shewn in full lines.
In the design delineated by Figure 1. forced air pressure is established under
the grate by means of a steam-jet air-inducer trunk K. having a steam-jet nozzle L.
The pressure of air and steam is established under the grate M. The clinker
doors N. are made absolutely tight fitting by cross-bars and screw O.
Special clinker bearers and bars, are provided by which the grate area is very
effectually increased.
J
The fuel is fed into fuel chamber through doors Q. the fuel being maintained at
the level R. The air to support complete combustion, flows through radially
arranged tubes S. crossing the circular formed main G. The air aspired in a

page_text: descensional direction through a hollow space formed round the combustion chamber
outer casing. The direction is shewn by arrows.
The air becomes heated, and flows into the combustion zone over the fuel, the
proper admixture of gas and air being aided by the refractory frame-work H.
The air for supporting combustion is aspired either by natural chimney draught,.
or by an aspiratory arrangement T. placed at the base of inverted cone shaped
chimney U. The exact balance between the aspiration of the volume of air and
the plenum of combustible gas, can be established at will, and absolutely, so that.
with this arrangement smokeless combustion can be always maintained.
The flame action of combustion is limited to the combustion zone, in coil chamber,.
the flame itself not being allowed to reach the steam and water drum.
The gases from combustion flow through central flue V. and then through the
cross flue W. into air annular jacket X. surrounding the superheater steam part Y.
surmounting the down flow pipe F. so that the steam in the latter becomes highly
superheated.
The steam connection between the superheater and the arum is effected by a
side pipe connection.
I will now more particularly denote the direction of the circulation of the water.
Starting from the downflow tube the water flows through a connection 3. into
the annular water main G. and from thence into the coil pipes, from which it flows.
once or twice round the combustion chamber, and then ascends to the steam and
water drum E. where one half of the volume of water and steam is delivered
above the water level, and the other half below the water level, so that immediately
heat is generated, circulation is at once produced.
The water flows from the steam drum through connection 4. into vertical down
flow pipe F. and slowly descends to the lower connection. The salts in suspension
gradually become deposited in the lowest limb 5. from which they can be blown
off by the cock 6.
In order to allow for any variation of expansive effect, the down flow pipe F. is.
provided with expansion rings 7.
The method of attachment of the coil pipes to the drum E. and circular main G.
is the cone and screw ferrule arrangement by which the coil pipes can be rapidly
disconnected and replaced. The connections are easily accessible or approached
by opening and moving the refractory lined doors 8. of which there are at least two
in number. The upper drum E. is supported by strong frame supports 9. which
are bolted or rivetted to the gas generator casing. These frames enable the
side doors to be completely removed, so that the coils can be examined, removed
and renewed.
In the modification shewn in Figure 4. instead of there being a single central
flue through the steam drum E. there are a series of tubes 10. through which the
gases pass to the steam-jet aspirator chimney 11. which immediately surmounts the
generator. In other respects the arrangement is similar to that described.
Referring again to Figure 1. it will be seen that over the central flue in
the steam generator there is a man-hole lid by which the flue and coil chamber can
be examined.
Referring to Figures 5. to 8. on Sheet 2. of drawings, shewing a modified
arrangement of my invention applied to a donkey or other type of steam boiler-
Figure 5. is a vertical section,
Figure 6. is a side elevation,
Figure 7. is a cross-section through combustion chamber, and
Figure 8. is a plan of top.
Inside the combustion chamber 20. there are arranged a series of coil pipes 22.
attached to the flue plates as shewn, the combustion chamber 20. being made
sufficiently large to permit the attachment of the tubes from the inside.
The water flows from the annular space 23. through the coils, and is injected into
the steam space 24. The water and steam easily separating, the water descends
very slowly to the lower part of boiler through a down flow vessel 25. in which

page_text: the suspended matter is deposited and can be blown off. An aspirator 26. is
preferably fixed inside chimney 27.
Having now particularly ascertained and described the nature of my said inven-
tion and in what manner the same may be performed, I declare that what I claim is
included in the following:-
--
1st. The vertical tubulous steam generator substantially as shewn and described
in Figures 1. to 4.
2nd. The combustion arrangement in a vertical steam generator substantially
as shewn and for the purpose described.
3rd. The method of drawing or aspiring the air around the outside casing of
steam generator in water to reduce radiation substantially as shewn and described.
4th. The method of effecting the mixture of air and combustible gas in a vertical
steam generator substantially as shewn and described.
5th. The general arrangement of water circulating pipes for the purpose
described.
6th. The method of superheating steam substantially as shewn and described.
7th. The method of inducing the deposition of the suspended salts in a boiler
of the vertical class substantially as shewn and described.
8th. The structural form of combustion chamber in a boiler of the type shewn
in Figures 5. to 8.
9th. The manner of applying small coil pipes substantially as shewn and for
the purpose described in Figure 5.
10th. The method of construction shewn in Figure 1. and described, by which
the coils can be rapidly removed and replaced.
11th. The general arrangement of steam drum shewn in Figures 1. to 4.
12th. The improved form of tubulous drum generators substantially as
specified.
Dated this 2nd day of Inl 1809
B. H. THWAITE.