Improvements in Apparatus for Generating Steam.
Year: 1893

page_text: Date of Application, 28th Oct., 1893-Accepted, 8th Sept., 1894
COMPLETE SPECIFICATION.
Improvements in Apparatus for Generating Steam.
We, BENJAMIN HOWARTH THWAITE of 95-97 Finsbury Pavement, in the
City of London, Civil Engineer, and JOHN BROKENSHIRE FURNEAUX of the
Victoria Works, Gateshead-on-Tyne, in the County of Durham, Mechanical
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:―
This invention relates to improvements in apparatus for generating steam
which we will proceed to describe with reference to the accompanying illustrative
drawings, and which will be set forth in the claiming clauses at the end of this our
Specification.
In the drawings the same letters of reference are used to denote like parts in
the several views in which they occur.
Fig. 1 (Sheet 1) shows a vertical section; and
Fig. 2 shews a longitudinal section, of steam generating apparatus constructed
according to this invention.
A is a water and steam vessel or drum; B B are longitudinal water vessels, one
at each side of the furnace; in these the mud is deposited from the water;
CC are straight outer tubes that connect the drum A with the water vessels B B,
these straight tubes being open at both ends and containing each an inner tube C
of greater length than the outer one: there is an annular space between each inner
tube and the corresponding outer tube; each inner tube terminates in the drum A
above the upper end of its containing outer tube and is there formed or provided
with a trumpet mouthed or other equivalent guide or deflector C2; the lower end
of each inner tube projects beyond the lower end of its containing outer tube into
the corresponding water vessel B. DD are curved tubes that also connect the
drum A with the water vessels B.
The tubes D are made each with a large special curve towards the centre of
the furnace, this curve extending to within a comparatively short distance of
the upper and lower ends of the tubes; but the end portions are curved in a
contrary direction, and the arrangement is such that portions of the curved tubes
between their extremities pass through the vertical spaces formed by and between
the straight tubes C.
By this construction, ample space is provided between every two of the curved
tubes D to allow of access for adjusting or tightening up their end connections
whilst at the same time the straight tubes C serve as baffles in the spaces between
the bent tubes D.
The nest of curved tubes D may be made of any suitable material, such as
copper or weldless steel, aluminium, or wrought iron. When using steel or
wrought iron tubes, in order to preserve the tubes from internal pitting action we
in some cases provide each curved tube with a zinc wire or strip threaded through
the tube and bent at the upper end so as to rest on the top of the tube in
suchwise that the zinc can easily be removed as will be readily understood and
whereby electrical action will be set up at the expense of the zine to protect the
metal of the tubes. In applying zinc for this purpose to the double tubes C C¹
we prefer to wrap or wind the zinc spirally around the inner tubes, and to make it
extend across the annular space, so as to cause the water to flow upward in a spiral
direction (see Fig. 2). The inner tubes C¹ may in some cases be of glass, and be
maintained in a central position by light feathers or clips of metal.
In order to prevent or mitigate priming in the drum A and to separate the water

page_text: from the steam, we in some cases employ a baffle plate X placed along the entire
length of the drum, and tending to break the high velocity flow of the water. Or
we may cause the water and steam projected from the curved tubes D and the
annular spaces between tubes C and C' to pass above the level of the water in the
steam and water drum, by the use of curved plates such as represented at C³
Fig. 1. so that the water is deposited from the steam.
The cycle of water circulation is as follows:-
Water is fed in to the apparatus at any convenient point, for example into one of
the water vessels B. When the boiler is charged with water owing to the action
of the heat upon the tubes, first the hotter water ascends and ultimately steam and
water ascend from the water vessels B by the tubes D and by the annular spaces
between tubes C and C¹ into the drum A, cooler water descending by the inner
tubes C¹ and so on. We may also provide additional externally placed descensional
flow tubes such as shown at L on Fig. 4 Sheet 2 of the drawings.
M is the combustion chamber containing the nests of tubes C and D ; its side
walls M are formed of light steel frames, filled in with firebrick tiles, or with
asbestos sheeting, and thus are readily removable. In order that the combustion
chamber may be accessible, for examination and for renewal of tubes, side doors
are provided at N. They may either be lined with asbestos or firebrick; or they
or the side walls may be water jacketted and a constant flow of water may be
Inaintained through them, in a manner that will be readily understood, such water
being employed for feed or other purposes.
The fuel combustion is preferably effected by artificially induced currents of air,
by which, with an appropriately designed form of grate almost any character of
solid fuel can be consumed.
We provide as hereinafter described for admission of a secondary supply of air
at the respective sides of the furnace in such a manner as to distribute the incoming
air over the fuel practically throughout the length of the furnace.
We may, and preferably, for land boilers, do use a perforated arch such as
represented in dotted lines at G Fig. 1 composed of refractory material such as
will become incandescent under the action of the heat, and which springs from
each side of the grate, and may advantageously have a height from its under
surface or soffit of say not more than two feet nor less than one foot.
The arch is built up of perforated arch bricks, formed of refractory clay of
such a character as to be durable and efficient under extreme ranges of temperature.
Lowwood's fire bricks are suitable.
H H are skew bricks or springing blocks forming part of the walls of the air
flues or channels F.
An arrangement whereby the secondary air supply is provided is shewn in
Fig. 1 and is as follows:-
Formed in the skew back, or springing wall of the arch already described, or
(where no such arch is employed) in the dwarf side walls formed along the length
of the firegrate, we provide air flues or channels F, the inlet ends of which may
be covered with wire gauze, and we provide simple means such as a bit and miss
valve, for regulating' the supply of air. E E are slots or apertures provided in
the furnace walls along both of the side channels and proportioned in size to the
positions they occupy as respects distance from the point of entrance of air at the
front end of the structure. In order to create the induction of air under the fire-
grate, we may employ an ordinary mechanical contrivance such as a Roots
blower, a Sturtevant or other fan, or (as we prefer) a steam jet forced blast
apparatus.
The double angle iron joints K respectively encircle each in one plane the
metallic structures respectively forming the steam and water drum A and water
vessels B.
00, represents the upper casing; it may be constructed as a framework, lined
with material that is a bad conductor of heat, such as asbestos; or the casing may
enclose an air space P. It is in either case so arranged as to provide a complete

page_text: flow space O for the passage of the gases of combustion around the steam and
water drum A. The products of combustion flow upward between the tubes C
and D and by O O, to the chimney.
It is to be understood that we do not limit ourselves to the exact details shewn
as these may be modified without departure from the characteristic features of the
invention.
We construct apparatus according to this in vention adapted to use as fuel the
organic matter constituting the refuse of towns for which purpose we combine a
tubulous boiler with a furnace of the kind known as a refuse destructor the arrange-
ment being substantially such as represented in Figures 3 and 4, on Sheet 2 of the
drawings where the disposition of parts is clearly shewn.
As in the preceding arrangement, A is the drum, B B are water vessels,
CC tubes connecting drum A with water vessels B B and containing iuner
tubes with trumpet mouthed or equivalently formed guides or deflectors (not
shewn). D D are curved tubes that also connect the drum A and vessels B and
which project inwardly between the tubes C. G is a perforated arch, that becomes
incandescent under the action of the heat; M a combustion chamber; M¹ M¹ side
walls.
The refuse is tipped by an automatic feed arrangement Q into the upper
receptacle and onto a movable firegrate R working on eccentric cams S that
gradually bring the material to the front end T of the firegrate, from which the
residue falls into a closed receptacle.
The flame and gases of combustion flow through the perforations in the arch
and through the spaces between the tubes C and D into the main side flues U that
form parts of combustion chamber M. These flues afford access to the nests of
tubes for examination and repair. The gases flow from U by the short flues U¹
into the side flues V. Access to U by means of the openings W.
Figs. 5 and 6 represent, respectively, a vertical section, and a sectional plan, of
an improved vertical arrangement of apparatus for generating steam in which the
steam generator proper is of a vertical tubulous type already known but the tubes DD
which are of small bore and connect the lower ring shaped water vessel B with the
upper, water and steam drum A are peculiarly curved as represented in the drawing.
As will be seen the tubes D are arranged with their axes in vertical planes radial
to the axis of the combustion chamber and are so curved and arranged in relation
to the perforated dome (G which is of refractory material) that the entire tubular
surface is exposed to flame issuing from the centrally arranged firegrate, but that
nevertheless the tubes do not interlace each other, and therefore any one of
them can be readily removed without interfering with its neighbours (see plan
Fig. 6).
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed we declare that what we
claim is: :-
1. Apparatus for generating steam constructed arranged and operating
substantially as described with reference to and shewn by Figures 1 and 2 of the
accompanying drawings whether the tubes C' have trumpet mouths as at C³ or a
guide plate as at C³.
2. In a steam generator the combination and arrangement substantially as
described of a water and steam drum such as A, water vessels such as B, B, straight
tubes such as C, C, connecting the said drum and water vessels, and furnished with
inner tubes, and curved tubes such as D D that also connect the drum A with the
vessels B B, the arrangement of the tubes C and D being such as to render their
upper and lower ends readily accessible.
3. In a steam generator such as referred to in the preceding claim, the relative
arrangement of the tubes C and D so that portions of the curved tubes extend
between the straight tubes as described and illustrated.
4. In apparatus of the kind referred to for generating steam providing

page_text: substantially in the manner described for a secondary air supply through openings
at the respective sides of the furnace adapted to distribute the incoming air over
the fuel practically throughout the length of the furnace.
5. In apparatus of the kind referred to for generating steam, the fuel combustion
arrangement including the perforated incandescent firebrick arch G and secondary
air supply substantially as described with reference to Figs. 1 and 2.
6. In apparatus of the kind referred to for generating steam, the combination
with the curved tubes D of the removable zinc strips or wires as and for the
purpose specified.
7. In apparatus of the kind referred to for generating steam the combination
with the inner and outer tubes C' and C of the spirally arranged zinc whereby the
water is caused to ascend in a spiral direction and the tubes are protected as
.described.
8. The combination of a tubulous boiler with a furnace of the kind known as a
refuse destructor the boiler being arranged directly over the furnace substantially
as described with reference to and illustrated in Figs. 3 and 4 on Sheet 2 of the
drawings.
9. In a steam generator of the type represented in Figs. 5 & 6 the peculiarly
curved water tubes D D shewn and described with reference to the said figures.
Dated this 28th day of October 1893.
W. LLOYD WISE,
46, Lincoln's Inn Fields, London, W.C., Agent for the Applicant.