Improvements in Steam Generators.
Year: 1888

page_text: Date of Application, 14th Jan., 1888
Complete Specification Left, 15th Oct., 1888
Complete Specification Accepted, 14th Dec., 1888
Improvements in 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:-
"
My Invention consists in Improvements in steam generators, and partly relates to
an Invention entitled an Improved Steam Boiler," and for which letters patent have
been granted to me, numbered 1201 dated the first day of January 1885.
The application of my Invention to a steam generator of the Lancashire and Cornish
type consists as follows,-Concentrically and at properly proportioned distances from
the upward or outer sides of boiler flue, and the whole length thereof, and in the water
space I provide two segments of a tube or cylinder-radiating from the centre of flue
the two segments being disconnected at the top and bottom; so that the water can
flow ascensionally through the space between the segments and the flue.
The two segments which I form of zinc, but do not confine myself to the use of that
material, are kept in their concentric position, by means of light zinc angle or T pieces,
fixed around the flues or flue at convenient distances, along the length thereof."
The effect of this arrangement on the circulation of the water in a Lancashire
Boiler would be as follows, the heat from the sides of the flues would induce a rapid
ascensional flow or circulation of the water, around the flue sides removing by the
attrition on the flue sides of the molecules of the water, any deposited calcareous
material, which however is unlikely to fall or settle on the flue sides-owing to the
rapid circulation-The flow of water after its ascension around the flues-through
the space between the concentric segments and the sides of flue, descends on the out-
side of concentric segments, to the bottom or lower part of steam generator, where the
comparitive quiescent condition of the water induces a deposition of the calcareous
material, on the side of the boiler, where it is least likely to set in hard cakes.-The
molecules of the water in their ascensional and descensional currents, do not collide
with each other, owing to the division formed between the two currents by the
segmental cylinders.

page_text: .
The distance between the annular segments inducing circulation cylinder, and flue
sides, being so proportioned as to facilitate the flow of the water. Instead of cylinder
segments I may use a U shaped zinc trough ;-the upper side over the flue being
covered with a flat perforated plate-the invert of trough being also perforated to allow
the water to flow into the space between inducing circulation trough, and flue sides.
The zinc in contact with the flue sides forms a voltaic couple by which the iron plates
of flue are preserved by a. well known electro chemical action from corrosion or
oxidation. When the boiler flues are corrugated I use corrugated segments and
corrugated angles and T stay irons. The corrugated segments being placed concen-
trically to flue.
In a vertical generator of the type shewn in my patent specification No. 1201, dated
Jany. 1st 1885. In the centre of the central combustion chamber I place a circular
refractory flue or retort leaving an annular space between it and the flue sides. The
flow of combustion first ascends through the central-refractory flue and then descends
through the annular space between central flue and the lining of main flue-to an
annular cavity or flue under the nest of generator tubes-surrounding central flue-1
provide this annular flue with a series of air-inlet tubes-provided with air regulators,
by which combustion can be effectually conipleted.-The products of combustion pass
ascensionally through nest of generator tubes-and then pass through a series of
radially arranged air heating or recuperative tubes, by which the sensible heat of the
products of combustion is recovered the products of combustion (with their tempera-
ture lowered to the average degree, between the outside air temperature and that of
the gases of the products of combustion, on leaving generator tubes), now escape to
the chimney.
'
The air flowing through the recuperative air tubes meets the gas as it leaves the
upper end of central retort or flue-and the combustion flows as already described
downwards between the central flue and the main flue.
A similar central flue may be placed in the centre of Lancashire and Cornish or
other type of horizontal steam generators, with radial air heating tubes at the end
thereof, the combustion flowing in the annular space between the central flue-and
a concentric flue-to the front end of steam generator, and then returning in the
annular space between the second annular flue, and the flue plates.
Dated this 13th day of January 1888.

page_text: I, 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:—
My Invention consists in Improvements in Steam Generators and partly relates to
an invention entitled an Improved Steam Boiler and for which letters patent have been
granted to me dated the 1st day of January 1885.
Before referring to the two sheets of drawings that accompany this specification I
wish it to be distinctly understood that I do not desire to be confined to the exact
details shewn therein as these may be considerably modified without departing from
the nature of my said Invention.
Referring to Sheet 1 of drawings figure 1 is a vertical section shewing my Invention
as far as it relates to a former Invention for which Letters Patent, Numbered 1201
and dated Jany. 1st 1885 have already been granted to me..
I will now proceed to describe these improvements as illustrated by figure 1.
a is the chamber, in which solid carbonaceous fuel is converted into gas, and, built
immediately below the.steam generator.
The gases evolved from the solid fuel in this chamber ascend and pass through the
pipe or other tube b, preferably formed of some kind of refractory material,-and
placed in the centre of the central flue c in steam generator d.
The gaseous fuel flows to the upper end of pipe or tube b, and enters the ignition
chamber e where it meets with the air flowing through the radially arranged pipes f
The flame of combustion descends through the space between the central pipe and
the refractory perforated lining g of central flue c.
This descensional flow of the flame of combustion is initiated in the following
manner.
Over and above the centre of the central tube or pipe b, in the centre of the upper
side of combustion or ignition chamber e, I provide a mushroom valve / actuated by a
lever i and chain j by means of a handle in starting, the flow of combustion the
mushroom valve h is opened or lifted and the flame of combustion flows directly into
chimney I, and when the latter has become heated sufficiently to induce or produce a
draught, the mushroom valve h is lowered or closed and the flame is induced to flow
descensionally by the action of the chimney draught.
The flow of combustion descends to the lower end of steam generator, and the heated
products of combination are distributed into the space m, and ascend through nest of
tubes n in steam generator, to the annular air recuperator chamber o, where they flow
around the air inlet tubes f, by which part of the sensible heat is transmitted thereto,
the products of combustion then flow through generator tubes 9 of upper steam
generator ; into chimney chamber and from thence into chimney l.

page_text: The upper steam generator and superheater is connected to lower one by water
tube connections & and t¹.
The circulating arrangement is effected as follows, midway between the central
flue C,
and outer casing of boiler, I place a circulating plate or curtain u extending from
the top tube plate to near the bottom tube plate w, leaving a space a for the passage
of the water currents from one side to the other.
The circulating plate is continued in upper steam generator and superheater r, and
serves to divide the ascensional currents from the descensional ones, the latter currents or
the descensional ones, flow through the water tubes t and descend near the outside
boiler casing, passing under the lower edge of circulating plate, and ascending, and
sweeping in their flow, the sides of the central flue, passing to the water tubes t¹,
through which the currents flow into upper steam generator and superheater »—and,
again descending and ascending.
By means of my Invention, perfect combustion of the fuel, and the highest efficiency
of heat transmission is attainable.
Figures 2 and 3 represent respectively a cross section and part longitudinal section
of my invention in its application, to ordinary Lancashire or Cornish boilers.
Around the flues are fixed zinc or other thin metallic plates 1, curved concentrically
to the curve of the flue 2 and kept at an equi-distance from side of flue by means of
contact and stiffening plates or pieces 3.
To divert the two side currents a central deflector piece 4 is placed in the centre of
the flue.
The currents flow in the direction indicated by the arrows. The arrangement shewn
in figures 2 and 3 is intended for boilers in which the flues are at such a distance from
each other as to permit this application.
The arrangement shewn in figures 4 and 5 is intended for boilers in which the two
flues are placed in close juxtaposition to one another. Figure 4 is a cross section and
figure a part longitudinal section.
In this arrangement the circulating plates only partly surround the flues, and the
flow of water is only in one circumferential direction around the flues, as shewn by
the arrows.
The circulating plates over lap each other at the upper or top side of flue at 5
so that the flow or currents of water on each side are directed or diverted in one
direction.
The zinc distance pieces 3, see figure 5 are channel shaped, and the circulating
plates 6 are made in segments so as to be easily applied to existing steam generators.
By this arrangement the circulation of existing steam boilers is much increased and
the rapid flow of water in contact with the side of flue plates clears them free from
any deposited calcareous material, and prevents corrosion, and the flow or transmission
of heat through the flue plates is greatly increased.
In Sheet 2 of drawings-Figures illustrated thereon and numbered 6 7 8 9 and 10
shew my improvements applied to ordinary steam generators. Figures 6 and 7 shew
respectively a longitudinal and cross section of one arrangement by which the com-
bustible gases and flame are made to return in a central passage or flue and then reflow
to the chimney either directly or indirectly.
A is the flue, B the firegrate, C the bridge. A horizontal firebrick or other kind of
refractory partition D formed of specially moulded tiles, but it may be constructed of
arch bricks and adapted to the cross tubes, if these exist, is built in the flue, below
this, with, a space intervening between the upper side of arch partition D, is
another horizontal partition E,.both arches are continued along the flue as shewn-in
figures or in such a manner as to leave a space F between the Bridge-C and the
partition E.
The flow of gases proceeds as shewn by the arrows.
In the Bridge CI provide a series of perforations G to supply air to oxidise the
incandescent atoms of carbon and any unoxidised carbon monoxide, as they descend
into the space H and flow towards the chimney.
These refractory partitions become heated to such a degree as to maintain the

page_text: atoms of carbon in an incandescent condition until they are met by the secondary
supply of air issuing through the perforations G, or in other words the heated sides
of the partitions prevent the temperature of the carbon atoms from becoming too
seriously reduced for chemical action to take place. Any cooled or unoxidised carbon
atoms become highly heated in contact with the sides of the fireclay partitions and
meeting with a secondary supply of air are oxidised to CO,.
Figure 7 shews a section of the flue, and the fireclay arcli partitions, D and E and
the perforations G for supplying the secondary air supply.
Figure 8 shews another modification of my Invention. In this application the
return flue arrangement, is provided by the pipe I, over which is placed a curved
plate J by which the gases are made to traverse the flue to the end and then return to
front end of pipe I through which they ultimately pass, meeting however a secondary
supply of air at the mouth of the pipe I, which said air is blown through a pipe K-
placed over or between the grate bars--so that the supply of air becomes highly
heated in its passage through it, and so ensures a more perfect combustion. The
pipe K is provided with an archimedean screw for increasing the heated contact
surface during the passage of the air through it.
Figures 9 and 10 shew iny arrangement in its application to the ordinary type of
return flue marine boiler. In this application of my Invention, the flue L, that dis-
tributes the products of combustion to the steam generator nest of tubes M, has a
hollow central flue N built therein, through which the gases of combustion ascend and
descend between the two sides thereof and the tube plates.
The central hollow wall N may be made of chrome iron, or other highly refractory
quality of iron. Or I may use refractory siliceous material of specially formed
moulds so as to permit a rigid character of construction to be attained.
com-
At the base of the central hollow flue I provide a secondary air supply admission
arch O, through which the air, preferably heated, enters, and mixes with the con
bustible gases and oxidises any remaining unoxidised carbon atoms, the flame
ascends to the upper-end P of central wall and then descends on each side Q thereof, if
the steam generator is of the double type-but if it is a single generator, the flame
descends on one side in the space formed between the hollow wall and the tube plate,
and enters and flows through the tubes.
Having now particularly described and ascertained the nature of my said Inven-
tion and in what manner the same is to be performed I declare that what I
claim is as follows-
First. The fuel combustion arrangement in a vertical steam generator,—substantially
as shewn and described in figure 1, sheet 1 of drawings.
Second. The circulating arrangements of a vertical steam generator, substantially
as shewn and described in figure 1 sheet 1 of drawings.
Third. The arrangement for promoting circulation of water in horizontal steam
generators substantially as shown and described in figures 4 and 5, sheet 1 of
drawings.
Fourth. The fuel combustion arrangements as applied to flues of steam generators
substantially as shewn and described in figures 6 to 10-sheet 2 of drawings.
Dated this Thirteenth day of October 1888.