An Improved Form of High Temperature Furnace, especially adapted for the Conversion of a High Carbide of Iron into the Low Carbide condition known as Steel.
Year: 1891

page_text: Date of Application, 22nd Jan., 1891
Complete Specification Left, 20th Nov., 1891-Accepted, 9th Jan., 1892
PROVISIONAL SPECIFICATION.
An Improved Form of High Temperature Furnace, especially
adapted for the Conversion of a High Carbide of Iron into the
Low Carbide condition known as Steel.
I 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:-
This invention is for an improved form of high temperature furnace especially
adapted for the conversion of a high carbide of iron into the low carbide condition
known as steel.
By the use of this invention the following defects, common to ordinary high
temperature alternative recuperative furnaces-known as open hearth regenerative
furnaces are entirely removed or considerably reduced.
I will now enumerate the defects referred to and which are overcome by the use
of my invention.
A. Loss of or reduction of the hydrocarbons of the CH, and CH, and other
like series, by thermolytic action resulting from the passage of the generator
gascous fuel through high temperature chambers known as recuperators.
B. Reduction of the thermo chemical-value of the gas, per volumetric unit, by
its dilation resulting from the addition to its sensible heat by the passage of the
gaseous fuel through highly heated chambers known as recuperators or regenerators
before it enters the furnace.
C. Loss of combustible gas by its passage or escape direct to the chimney
through defective gas reversal valve.
of
D. Loss of the accumulated gas, stored in chambers aforesaid before the reversal
gas valve takes place.
E. Irregular production of thermic energy in furnace-due to the irregular
manner in which the valves are reversed.
F. Blocking up and inefficiency of recuperator's action by the introduction of
slag iron oxide or particles of siliceous material.
G. Loss of external heat radiated from recuperator vessel sides-and furnace
roof.
H. Loss of combustible gas and dilution of latter by interdiffusion of gas and air
through porous division walls.
I. Loss of heat by extravagant use thereof in effecting the removal of gases by
use of high chimney temperatures.
J. Great wear and tear of gas reversal valves.
I effect the removal or reduction of all these defects by the use of my invention
constituted of the following features or characteristics.
First. I abandon the use of a gas recuperator chamber.
Second. In its place I provide a gas and air mixing chamber displacing the
present port blocks.
This gas and air mixing chamber, one of which I place at each end of furnace,
I fill with checker or baffler brickwork that can be easily removed, repaired
and renewed by means of a built up opening formed in the two ends walls of
furnace.
Third. The vertical centre of the gas and air mixing chamber is identical with
that of the air recuperator vessels.
Fourth. I employ two air recuperator chambers of adequate capacity and equal
to the combined internal cubic proportions of the ordinary combined air and gas
chambers.

page_text: Fifth. I place these air recuperator chambers bodily over the end blocks of
furnace supporting them by heavily proportioned side furnace buckstays.
I externally encase the brickwork of recuperators by means of rivetted iron
plates, providing special openings by which ingress into chamber can be effected
for the rapid removal and renewal of the baffler and checker bricks.
I connect the two air recuperator chambers at their upper ends, by the
central reversal valve through the aid of which the air is alternately directed
to one or the other of the two chambers. This valve also connects the chimney
to one or the other of the two air recuperator vessels as the case may be.
I make the valve connecting passages as short as possible and I provide clearing
out arrangements.
For the central reversal valve I use by preference the type of valve known as
the butterfly valve, built up of steel plates.
Sixth. I connect the chimney to the upper branch or end of the air reversal
valve, I may surround the chimney with a continuous flow of water, or I may force
the flow of the residual gases from combustion, through a head of water to abstract
the necessary sensible heat, or I may employ, in order to facilitate the removal
of the gases, an exhaust fan, or a steam jet aspirator.
Seventh. In order to reduce the thermic radiation from sides of air recuperator
chambers and from roof furnace to as low a measure as possible, I provide an
external air jacket or annular space around both vessels; to this I connect the air
supply to support combustion.
I force the air by means of a fan or other contrivance through the annular space
around the air recuperator vessels, so that the radiant heat is added, as sensible
heat to the air, and is thus recovered. I also suspend just over the roof of furnace
a sheet iron plate which I connect up to the sheet iron tube or pipe through and by
which the air flows to furnace; in the latter I may arrange iron plated fins or spiral
bars by which the heat accumulated from the plate over roof is rapidly transferred to
the air.
Eighth. I may connect the air inlet pipe to fan, to the underside of the
furnace, so that the heat radiated therefrom is also reutilized, and the arduousness
of the work of control and management of furnace is considerably reduced.
Ninth. I connect the gas generator plant to furnace in as direct and convenient
a manner as possible.
1 may, indeed, combine the two plants, building a gas generator at each end of
furnace, but usually I prefer to keep the two plants distinct, providing each end
of furnace with a gas uptake or uptakes by which the gas is delivered into the air
and gas-mixing chambers.
At the base of the gas uptakes I provide arrangements for cleaning them out, as
well as for clearing the flues.
As near as possible to the base of the uptakes, I provide a mushroom valve of the
vertical lifting and regulatable type.
Tenth. I provide a gas reversal valve either at each end of furnace, or I combine
the arrangements, using the ordinary butterfly or pot-type of valve, for directing
the flow of gas either to one or the other end of the furnace.
Eleventh. I connect up the air reversal and the gas valve together, so that the
movement of one lever reverses both valves.
Twelfth. In order to effect regularity of reversal movement, and ensure equable
periods between reversals, I employ an automatic arrangement, similar to the
principle shewn in Figures 5 and 6 on Sheet 3 of drawings, of my invention,
numbered 971, 1891.
Thirteenth. The automatic arrangement I couple up to an overhead shaft, placed
in such a manner as not to interfere with the working of the furnace, and connected
up at one end to the lever that actuates the reversal valve.
Fourteenth. When I apply my invention to an existing furnace of the general
type, I proceed as follows:-
open or remove part of the division walls, that divide the gas from the air

page_text: chambers, converting both chambers for the use of air, I entirely disconnect the
gas reversal valve from the chimney.
In the upper end of the existing gas chamber, I provide a shallow passage
under the soffit of existing arch that covers gas chamber; I effect this alteration
or the formation of the passage by turning a second arch some twelve inches
below the existing one. To this passage I connect the gas supply flues between
gas reversal valve and furnace, by vertical refractory lined uptakes: The gas
enters the space between the two arches, and enters into the usual vertical port.
The space under the new arch is appropriated for air heating purposes by
recuperation. I alter the upper part of gas and air port blocks, replacing a great
part of the latter by a gas and air mixing chamber, which I fill with baffler bricks
easily removeable when required to be renewed.
I disconnect the gas flues or passages from lower part of gas chambers, and also
disconnect the reversal valve from the chimney.
I prefer to connect the air reversal valve to a fan, but I wish it to be under-
stood that I can use natural draft methods for both the modifications of my
invention.
Fifteenth. I provide a special form of construction for furnace doors, similar to
the principle adopted for gas retorts, by which they can be quickly opened and
tightly closed.
Sixteenth. Instead of an air supply I may use a supply of oxygen continuously
or intermittently, or may use part oxygen and part air, as best found practicable
and advantageous.
Dated this 21st day of January 1891.
B. H. THWAITE.
COMPLETE SPECIFICATION.
An Improved Form of High Temperature Furnace, especially
adapted for the Conversion of a High Carbide of Iron into the
Low Carbide condition known as Steel.
I BENJAMIN HOWARTH THWAITE of 37 Victoria Street Liverpool in the
County of Lancaster Civil Engineer do hereby declare the nature of this inven-
tion and in what manner the same is to be performed, to be particularly described
and ascertained in and by the following statement:―
My invention relates to an improved high temperature recuperative gas furnace
and is described in the following pages.
Before describing in detail the annexed illustrations, which shew the combination
of the various structural elements constituting my invention, I wish it to be
distinctly understood, that I do not intend to be confined in the scope of my claims,
to the employment of the exact details shewn therein, as numerous modifications
may be designed, without departing from the nature of my invention, or constituting
an evasion thereof.
The justification of my invention may be summarised in the following sentences.
The ordinary high temperature open hearth gas furnace, combining a gas and air
recuperator chamber, and 4-way gas reversal valve, and with the recuperator
chamber below the hearth, and worked with natural draft-is responsible for a very
serious thermic waste by loss of unconsumed gas and by the reduction of the
hydrocarbons by thermolysis.
By waste of heat units, through side radiation from recuperator chamber side
walls.
By the relative position of the recuperator chambers to the hearth.
The oxidised metalloids, the oxidised iron and lime and fusible slag, are carried
into the checker brickwork of chambers, and fluxes it, and eventually, obstruct the
flow of gas or air through it.
Further, if the metal breaks through the bath it often runs into the recuperator
chambers placed beneath the hearth.

page_text: Another defect is the difficulty in maintaining the leaklessness of the gas
reversal valve, the combustion of the residual gas after the reversals, soon induces
such a serious degree of warping that the valves cannot be properly closed.
All these objections and disadvantages are removed by my invention, which
permits the attainment of the highest temperatures in a most thermically economic
manner and permits a control over the chemical nature of combustion hitherto
unattainable.
The salient structural characteristics of my invention may be described as
follows-
First—I provide two separate, and distinctive air recuperator chambers for
transferring the sensible heat of the products of gaseous combustion to the air.
Second Gas recuperator chambers are not provided, but in their place, two
heat accumulating chambers are supplied: by which part of the heat of combustion
is transferred to the inflowing gaseous fuel.
Third The air recuperator chambers are placed above the level of roof of
furnace, and immediately over port blocks, in such a way that the hearth and ports
can be repaired without disturbing the recuperator chambers.
Fourth The outer ports from air recuperator chambers debouch into an initial
mixing chamber, in which the gas, and air are intermixed before flowing over
hearth of furnace.
Fifth A mechanically forced on induced pressure of air is preferred and for this
purpose a positive Roots blower is preferably employed.
The air may be introduced directly into the upper part of air recuperators,
through the checker brickwork of which it is compelled to flow; and there being
always a slight plenum established, all the heating surface parts of the recuperator
are usefully effective.
Sixth-Instead of the air supply for combustion being introduced direct into the
air recuperator chambers, it may be supplied intermediately to the air jackets
surrounding the air chambers-from which it enters the upper part of the
recuperator.
By this means the side radiated heat is recovered to a very considerable extent.
The port blocks and heat accumulating gas chambers at the ends of the furnace
are supported by steel plates carried from side buckstays, and a free air passage is
provided under the hearth and port blocks-by which repairs can be rapidly
accomplished.
Referring to Sheet 1. of drawings:-
Figure 1. represents a vertical and longitudinal section of the high temperature
furnace, constructed according to my invention.
Figure 2. is a vertical cross section through the centre of the hearth.
Figure 3. represents a front elevation of the furnace.
Figure 4. is a plan in section, at the level of the recuperators.
Figure 5. a plan of hearth of furnace.
Figure 6. a section shewing an alternate arrangement of accumulating chambers.
Figure 7. is a plan of the latter.
The gaseous fuel enters by gas uptake flues A, provided at each end of furnace,
alternately through one flue and then through the other.
The direction of flow being controlled by vertical lift, mushroom valves B.
The gas enters into the refractory lined and checker work heat accumulating
chamber C, a similar chamber being provided at each end of furnace.
The gas meets the air, and the two are thoroughly mixed-at the part D.-
. previous to their flow into the furnace.
The flame passes over the metal in the bath, and being under pressure, fills the
heat accumulating chamber at the opposite end of the furnace to which the gaseous
fuel, enters. The heat accumulating chambers thus become highly heated.
The sensible temperature of the gaseous fuel on passing through the heat
accumulating chamber is raised to a high degree.
The products of combustion flow ascensionally by ports E. into the overhead air

page_text: recuperator chamber F, which is, fitted with compactly arranged checker brick-
work, so that the heated gases relinquish a great portion of their sensible heat.
The gaseous products then finally escape from the upper end of furnace, into the
air reversal valve G, direct to the chimney, which may form part of a water heater
or steam generator.
The currents of gas and air are alternately directed from one end and then
the other of the furnace, the reversal being effected by the rocking lever H, by
which the gas valves are either lowered or lifted as required.
simultaneously reversing the air valve G.
The action
When oil is used for fuel, the reversal action also reverses the oil and
steam or compressed air cock 1 and J, by which the oil and steam are directed
to one or the other of the injectors placed at the ends of the furnace, and which
deliver their spray jets into a cone shaped orifice K, that terminates or opens
into the mixing chamber L, where the oil-spray or vapour meets its equivalent
air-spray.
The air supply may be simply aspired through the valve G, but I prefer to
supply the air by mechanical induction and pressure, and for this purpose I provide
the air pipe M, which connects the central air upcast pipe N, with the Roots or
other positive character of blower.
The air may be led into annular narrow jackets O, surrounding the air
recuperators through which the air is forced, and in its passage-absorbs part
of the heat radiated from the side plates.
The air after passing through the jacket escapes by the side connections into the
central upcast N, where it is distributed to the air recuperator chambers F.
I provide a valve in the pipe line of air supply, by which the air supply can be
exactly regulated.
It will also be noticed that the air recuperator chambers are, carried by steel
channel bars-supported by side buckstays P.
The heat accumulating chambers C are accessible from the two sides and end of
furnace movable plates and brickwork being provided to enable facile access to
the checker brickwork of heat accumulating chambers.
Instead of the arrangement of heat accumulating chambers-as shewn in
Figures 1 to 5-I may provide an external heat accumulating chamber C C as
shewn in Figures 6 & 7, connected directly to the gas flue Q, thus avoiding the
nécessity of the use of an upcast gas flue.
I prefer to entirely encase the brickwork of recuperators with sheet iron casings,
providing an intermediate layer of ashes or sand between the brickwork and casing,
so as to provide movement accommodation for the brickwork under varying
conditions of temperature.
The reversal of the flow of gas and air is effected by the movement of one
lever H, that reverses the air reversal valve G on the overhead flue connections,.
and reverses also the direction of the flow of gaseous fuel.
The weighted horizontal lever H placed in an accessible position-is connected
at its ends to both gas and air valves. The reversal of these valves may also, and
simultaneously reverse the flow of oil and steam supplied to the injectors placed at
the ends of furnace.
I either inject the oil by means of compressed air or steam, or by pressure,
providing reversal valves, in such a way that they are actuated by the movement
of the controlling lever that actuates the other gas and air valves.
In using oil I generally employ a small gaseous fuel flame as well, so as to obtain
uniformity of heating effect.
The chimney S, I place immediately over the upper reversal valve G. pre-
ferably construct the chimney of steel."
I may for economic purposes surround the chimney with water, or convert it
into a steam generator, in a similar manner adopted for puddling furnaces.
When I automatically reverse the reversal valves, I adopt the arrangement
shewn in Figures 8, 9 and 10 on Sheet 2. of drawings of which Figure 8 is an

page_text: elevation of the general arrangement of furnace and Figures 9 and 10 shew details
of the mechanism of automatic gear.
In the arrangement shewn by Figure 9. the reversal of valves is effected by the
reciprocatory movement of a piston 1. moving in a cylinder 2. by the impelling
force of water introduced alternately, to one and then to the other side of piston 1,
by the four way reversal valve 3.
The piston rod has, at each of its terminations a stiff arm 4, attached to a
connecting link 5, in its turn coupled to a rocking picce 6, fixed behind the tilting
piece 7, or forming part thereof.
The rocking piece is thrown by the movement of the piston rod over the vertical
centre, and the rolling counterbalance weight 8, then runs or rolls to the end of the
rolling surface 9, and by its momentum, and the leverage, the tilting piece falls
down to the full extent of its movement, reversing all the valves, the quadrant slot,
by which the connection to the connecting links 5 and arms 4 is effected-is
adequate in length to allow of the falling movement of the tilting piece by which
the reversal is effected.
The same reversal movement also reverses the flow of the pressure through
the four way valve 3, to one or the other side of the piston alternately.
The piston 1, travels free until the links, moving on the quadrant, arrive at the
end of the latter, then the tilting piece is drawn over the vertical centre in an
opposite direction, and the falling weight again reverses the valve.
Figure 10 represents an elevation of another arrangement for effecting the
reversal of the valves.
In this figure the weight of water at the end of the balanced lever tilts the
latter, as well as a weighted lever attached thereto, and reverses the valves.
12, marks the balanced lever and attached balance weight 13; at each end of
the lever 12, there is a bucket 14; as soon as the bucket is filled with water,
which latter falls from the pipe 15, its weight pulls over the centre the weighted
lever projection 13; and the bucket and balance weight fall to the full extent
reversing all the valves, including that marked 16, for supplying water first to
one bucket and then to the other.
By the rapid descent of the bucket, the water is thrown out, and the bucket
at the opposite end of the balanced lever is gradually filled.
This latter automatic arrangement is shewn on the elevation of furnace Figure 8,
surmounting a column 17 which serves for the removal of the waste water.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same may be performed I declare that what I
claim is summarised in the following clauses-
First The general arrangement of furnace substantially as herein described
and `shewn.
Second-The employment of heat accumulating chambers in combination with
air recuperators of reversible type-substantially and for the purpose described.
Third The arrangement of separate air recuperator chambers-fixed overhead
of port blocks in the manner-for and in combination with the furnace described.
Fourth-The arrangement of mechanically inducted air supply-for the furnace
specifically described.
Fifth The jacketting of recuperator chambers-for the purpose of heating
the air required for combustion of the gaseous fuel.
Sixth The gas and air reversal arrangement applied to the specific furnace
described and claimed.
Seventh-The automatic reversal arrangements applied to the specific furnace
described and claimed.
Dated this 20th day of October 1891.
B. W. THWAITE.