Improvements in the Manufacture of Steel, and in Plant therefor.
Year: 1887

page_text: Date of Application, 1st Dec., 1887
Specification Accepted, 20th Jan., 1888
Improvements in the Manufacture of Steel, and in Plant
therefor.
We BENJAMIN HOWARTH THWAITE of 37 Victoria Street Liverpool Civil Engineer
and JAMES NOBLE of Grosvenor Terrace Linthorpe Road Middlesboro, Manager of
Steel Works, 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 :-
Our Invention relates to Improvements in the manufacture of Steel and in plant
therefor and partly relates to a previous invention No. 11972 1886 and for which
letters patent have already been granted to Benjamin Howarth Thwaite.
We will now proceed to describe our said Invention and in what manner the same
may be performed.
When we require an accelerated or rapid output per furnace, we either carry the
molten metal direct from Blast Furnace to a receiver or melt the pig metal in cupola of
the Ireland, Stewart, or any other type, having a receiver, into which the melted metal
from Cupola can be accumulated, we may however run the metal direct from Cupola
into Ladle, but prefer the preliminary accumulation of the metal in the receiver-and
from this we tap it into the Ladle. The Ladle runs on rails fixed on a separate and
upper floor which said floor we construct over the open hearth furnace. This upper
floor is of such a beight above said open hearth furnace, as to be level with upper end
of a Thwaite vertical pneumatic converter,-placed on the centre of furnace
roof.
On this upper floor we place the openhearth recuperator vessels or chambers connected
by vertical and preferably refractory lined tubular connections to gas and air ports of
furnace.
The pig metal having been melted in Cupola, accumulated or stored in receiver and
tapped into Ladle, is then brought forward in the latter and tapped into the Thwaite
vertical cylindrical pneumatic converter and is gradually tapped therein, the air blast
being applied to it in its descent through converter, in order to partially convert
the metal, reducing its carbon down to say one per cent. or less-We prefer to use
water gas for second furnace or for final conversion process.
The bath of the openhearth furnace is made very shallow so that the metal occupies

page_text: in proportion to its weight, a very large superficial area exposed to the action
of combustion, and oxidation either by the oxidising gases, or by the iron ore
added thereto.
When we use pig metal of a phosphoric character, we may employ instead of a basic
lined cupola, a preliminary treating basic lined combined open hearth and inclined
furnace, this latter or inclined hearth furnace, has several levels by which the pig
metal can be rapidly charged thereon, and is rapidly melted, and gravitates to the lower
end, where it accumulates, in the bath of open hearth furnace, in order to increase the
basic character of slag, we add finely ground limestone to the pig metal, as it flows
down the inclined hearth of furnace.
•
We provide this open hearth and inclined furnace, which we term the phosphorous
removing furnace, with an alternative or continuous recuperative arrangement, in
order that if necessary, a steel melting temperature may be attained, but we prefer
(in order to effectually remove the phosphorous) to maintain the phosphorous removing
furnace, at a moderate temperature, or just sufficiently high to maintain the pig iron,
at a necessary degree of fluidity,--to allow it to separate its metalloids or its slag, which
slag, at a comparatively low temperature, and of a highly basic character-(as we
provide a lime and iron oxide bottom), contains the phosphorous in combination with
the lime, before tapping the metal (which is now a more or less pure carbide of iron)
from the phosphorous removal furnace, we may run off the slag or remove it by a
mechanical rabble or other arrangement, or we may separate it from the pure carbide
of iron during the tapping of the metal into the ladle, or direct into the Thwaite
vertical cylindrical pneumatic converter or Bessemer converter, or if we do not desire
to partially convert the metal during its flow into the second open hearth furnace, we
may tap the metal into second furnace by means of an ordinary runner.
We prefer to make the second furnace of siliceous refractory materials; and in order
to provide a small quantity of non-phosphoric slag, sufficient to cover the upper surface
of complete charge of metal before we tap the metal from cupola therein, we provide
a small bath of hematite pig metal and siliceous slag.
By means of our arrangement of plant, and modus operandi described, for phosphoric
pig, we more effectually remove the phosphorous from the metal and with a less cost
in repairs of lining.
With our arrangement of recuperator vessels in upper floor, the action of recupera-
tion is less likely to be disturbed by the accumulation of slag carried into recuperators
blocking up the passages through checker brick work. The working of the plant
would be much healthier and cooler for the workmen than the present system, and
not be so liable to derrangement by damp foundations, and there is also less ground
space required.
Our general and detailed arrangement of plant and modus operandi, or method of
manufacturing steel, enables the maximum practical heat efficiency of the fuel to be
obtained, along with the greatest out put and with the least cost in labour and repairs,
compatible with a homogeneous and reliable character of open hearth mild steel,
whether produced from siliceous or Hematite or from a phosphoric quality of
pig iron.
Before referring to the 6 Sheets of Drawings which we intend shall accompany and
form part of this Specification, we wish it to he clearly understood that we do not
desire to be confined to the exact details shewn therein, as they may be considerably
modified without departing from the nature of our Invention.
Wherever the reference letters or numerals are repeated they refer to the same or
similar respective parts.
Referring to sheet 1 of drawings, the figure illustrated thereon, represent a front
elevation of our arrangement of open hearth and rectangular furnace A, with a centrally
fixed Thwaite converter B and feed ladle C and with a pair of recuperator vessels or
chambers D and E, constructed on a separate and upper floor F of furnace-such
floor being supported by columns G. The recuperator vessels or chambers are
connected to furnace ports by cylindrical or other form of flue connections H
and I

page_text: We prefer to make the furnace bottom, as shewn by dotted lines J in elevation and
of such a form as to ensure that the molten metal, in process of conversion, shall be as
fully exposed to the chemical nature of combustion as possible, and we effect this by
providing the very shallow section of hearth shewn.
We arrange the gas ports K and air ports L, as shewn in dotted lines, the vertical
sides of ports being so arranged with regard to each other that the lines drawn
through the centre of each port shall intersect each other in the centre of furnace
hearth.
We may use two air and one gas, or three air and two gas ports, but do not confine
ourselves to any specific number of ports, but we prefer the geometrical plane arrange-
ment referred to in preceding paragraph.
We provide the usual catch pit or pockets for waste oxides to each gas and air port,
provided with cleaning out cross barred doors M as shewn, but as the recuperators are
constructed above the furnace the proportion of slag or oxide carried over into ports
and recuperator chambers is very much reduced.
In order to enable the recuperator chambers to be easily examined and repaired we
provide numerous side doors provided with cross bars and screws.
To allow the roof of furnace sufficient play to rise in centre an action usually
following prolonged working we provide an arrangement of lifting screw N by which
the converter can be raised.
We continue the overhead girders O carrying ladle carriage rails sufficiently
over lander P to enable the ladle skull or slag to be tipped into slag pool under
lander.
The hearth of furnace is supported on cast iron girders or rolled joists Q carrying
buckle plates R.
Referring to sheet 2 of drawings shewing a general section of plant required to
carry out one modification of our Invention-S is a cupola lined with a basic lining, for
melting highly phosphoric iron, and having a water jacket or lining T through which
we provide tubes for air blast tuyeres U. fed with air from the annular air belt V.
The entire structure of hearth and bosh which is separate from superstructure of
cupola, is supported by rolled joists W but we may provide an arrangement for lowering
the hearth of cupola for renewals.
The cupola superstructure X, we support on a square frame of rolled joists Y supported
on side piers of iron, masonry or brickwork Z.
The cupola Receiver 2 we provide with a supply of gaseous fuel to raise its
temperature prior to tapping the metal into it and we maintain the combustion of the
gaseous fuel in Receiver until the latter is ready for tapping.
The metal having been tapped from Receiver into ladle the latter is moved forward
until its nozzle is directly over the mouth of the Thwaite Converter B, when it is
gradually fed into the latter, the regulation of its flow being effected by means of the
usual plug stopper 3--The metal as it falls through converter is subjected to an
annular blast of air from air blast supply pipe 4 feeding annular air helt 5 and
perforations 6.
The partially converted metal along with its oxidised elements, fall into bath 7 of
open hearth furnace, which has already been provided with a small bath of hematite
or other pure or high class pig iron, and with this initial charge the partially
converted metal commingles, and when the metal is entirely charged therein its
conversion into the desired grade of carbon steel is proceeded with by the usual and
well known methods.
If the metal is still of a phosphoric character we may line the hearth 8 with basic
material on a substratum 9 formed of refractory siliceous bricks carried by buckle
plates R supported on cast iron girders Q.
The recuperator vessels E we connect by down casts 12 with flues 13 below the
ground and leading to the reversing valves 13 and 14; the vertical down casts 12 can
be easily removed for repairs.
The reversing valves which may be of the slide valve, butterfly or lift type,
D

page_text: we prefer to place at a convenient distance Trom urnace, anа under a somary
constructed arch 15 of brickwork, which supports the cupola and its Receiver.
The valve connecting flues to recuperator chambers, we may fix below the upper
floor instead of below the ground floor as shewn.
The gas supply main 16 we may also construct above or below ground as circumstances
appear to be best desirable.
The chimney 17 we prefer to construct of the tubular type internally lined with
refractory material 18, and provided with a solidly constructed foundation 19 and
chimney slide valve or damper 20.
Referring to sheet 3 of drawings, Figure 3 shews a plan of open hearth furnace with
alternate arrangements of gas and air ports, and their connections.
The right side of furnace plan shews two gas ports 21 and three air ports 22 placed
in two casings; on the left side there are provided, two air ports 23 and only one gas
port 24 in cylindrical connection casings, and we may make the casings in halves, so
as to, enable them to be easily opened, and repaired; for the refractory linings we
prefer to use tubular segments with rebated joints 25 and 26.
B shews a plan in section of the Thwaite converter.
The dotted lines on plan of furnace shew the general arrangement of side walls and
form of furnace ports.
1
Figure shews a plan of upper floor, and a plan in section of recuperator vessels;
E being the air recuperator, and D that of the gas.
The plan in section of left recuperators is through the lower inlet chambers-the
position of connections to furnace ports 23 and 24 is also shewn.
The products of combustion pass under arches turned at a height of about 2 feet,
between walls 27 and 28, to the end at 29 where they ascend through checker brick-
work, giving up their sensible heat thereto; and then pass over wall 30 descending
through checker brickwork 31, into escape flues 32 and 33.
The upper floor is strongly constructed with main and cross girders 34 and 35
supported on built up columns or standards of the Gorman-Long type 36.
The surface floor is provided by perforated plates 37.
Referring to sheet 4 of drawings the figure 5 illustrated thereon shews the modifica-
tion of the plant used by us, for carrying out the programme of operations, when we
have to deal with pig iron of a phosphoric nature.
The figure 5 illustrates a section through an inclined pig melting or ore reducing
hearth 38, a preliminary dephosphorising furnace 89 a ladle 40 a Thwaite converter 41
and final treatment open hearth furnace 42 the latter of the type of construction
illustrated in figure 1 on sheet of drawings.
The inclined furnace is provided with a continuous recuperative chamber arrange-
ment as shewn, or with an alternate system of recuperators. In the arrangement of
recuperation shewn, the products of combustion escape from inclined furnace by means
of the two escape flues 43, which lead the products of combustion to each side of
recuperator chambers 44, these chambers being filled with checker work walls, and
covered with an arch 45 which said arch supports a basic lined inclined floor 46 of
inclined furnace.
The products of combustion flow to the end of chamber and descend by flue 47 into
lower chamber 48, and then return to chimney 49; between these two entering and
escaping chambers there is an intermediate one 50, also filled with checkerwork and
divided from the other chambers by means of rebated tiled floors 51, through this
intermediate chamber, the air flows to support the combustion of gaseous fuel, the air
entering to this chamber by means of hit and miss valves 52.
The flow of the gases to chimney is regulated by means of valve 53.
The pig iron is fed into furnace by means of side doors 54.
The melted metal runs into hearth 55 of furnace 39 which said furnace is also
lined with basic material 60, built on a substratum of siliceous bricks, or they (the bricks)
may be of magnesian limestone calcined in situ ; the hearth of furnace is supported on
buckle plates resting on rolled joists or on cast iron girders.

page_text: The air and gas enter each end of furnace simultaneously, the air by means of
connections to recuperator 61 and the gas by ports 62.
In order to increase the basic character of the slag during the flow of the metal into
final conversion furnace, we may provide a lime feeding vessel 63 and we may also
provide an arrangement for feeding finely powdered line into the metal as it flows
descensionally through inclined furnace.
The temperature of the first or phosphorous removing open hearth furnace is kept
just sufficiently high, to maintain the pig in a fluid condition, and not at too high a
temperature as to prevent the phosphorous from joining the slag.
As soon as the phosphorous has joined the slag, the metal is then tapped into the
ladle and from thence is poured into the Thwaite Converter B and falls into the open
hearth furnace, in which there is already a small bath of pure hematite pig and
siliceous slag, so as to provide a layer of slag on the full charge of metal during its
complete conversion.
Referring to sheet 5 of drawings figure is a cross section on line A B of
figure 5, 38 is a section of inclined furnace. 44 and 48 are the combustion recuperative
chambers; between these chambers is the air recuperator chamber 50; over the
recuperator chambers is turned the arch 45 supporting floor 46. The air connections
between recuperators and furnace are shewn at 64. Gas ports 65 are provided at each
end of furnace, supplied from centrally fixed gas supply main 66.
Figure 7 is a plan in section taken through continuous air recuperator chambers on
line CD of figure 5.
Figure 8 is a plan in section of inclined furnace 38 and phosphorous removal
furnace 39.
The air enters by the regulating valves 67 and flowing through the checker
work becomes highly heated finally escaping by the two side connections 64 to
furnace.
In sheet 6 of drawings figure 9 shews a modified furnace arrangement which we may
employ for small weight charges-in this type we make the furnace circular in plan,
the underside of furnace is surrounded with a casing 65, enclosing an air space 66,
this air space we connect to another space 67 formed above roof of furnace, by means
of a light sheet iron cover 68, this space we connect to the air reversing valve 69, so
that the heat radiated from side of furnace is utilised by its readdition to the internal
heat of furnace.
Figure 10 is a section of the furnace taken through lander or tapping spout 70, and
through a Thwaite converter 71, in this instance the converter is placed at the side of
the furnace and inclined from the vertical, the air jet perforations being placed
directly under the metal, as it flows through Converter from Cupola 72 and its
Receiver 73.
The roof of furnace is suspended and is removable, and is turned on a ring (suspended
or carried by buckstays) formed of rolled joists, by this arrangement the side walls are
relieved from any lateral thrust.
We form a neutral layer between siliceous and basic material of walls, composed of
powdered carbon compressed by immense pressure into building blocks.
Referring to inclined Thwaite converter-we connect the upper part of this, see
figure 10 with the gas supply flue 74 so that the converter can be heated up to a high
temperature before the metal is tapped from Cupola Receiver.
The air to support combustion of the gaseous fuel in converter passes through metal
ingress opening 75, which can be entirely or only partially covered with a fire clay
plug 76.
Referring to figures 9 and 10, the reversing valve arrangement is placed on upper
floor; 78 is the air valve connected to air recuperator vessel 79-80 is the gas valve
connected to gas recuperator vessel 81, both valves can be simultaneously actuated by
the mechanical arrangement shewn; The valves are connected to chimney flue junc-
tion 82, by means of refractory lined flues 83; 'Figure 11 illustrates a half sectional
plan of circular furnace shewing a hinged frame arrangement for supporting the basic
furnace side walls-The frames turn horizontally on their axes or they may slide

page_text: ly between the buckstays so that the basic material can easily be renewed.
and air enter into furnace by radial and side by side ports, numbered
vely 85 and 86, each port being provided with cleaning out and renovating
7.
vish it be distinctly understood, that we disclaim the use of a lime and oxide
bottom or the addition of the powdered lime-to form or to increase the
aracter of the slag-except so far as they relate to the programme of opera-
ecifically set forth.
g now particularly described and ascertained the nature of our said
on, and in what manner the same is to be performed; we declare that what
nis-
The manufacture of steel from phosphoric pig with the arrangement of plant
lly described, and according to the following programme of operations :-
The melting of the pig in a cupola preferably with a basic and water lined
hearth and receiver.
Or proferably in an inclined, continuous or alternatively recuperative furnace,
with a basic character of hearth.
The gravitation of such melted pig down the inclined hearth during which
it is subjected to the influence of the fractional addition of finely powdered
lime-stone.
The accumulation and settlement of such melted pig iron in open hearth
furnace working in conjunction with said inclined furnace, and having a
basic lining formed of lime and oxide of iron.
The maintenance of a temperature in this furnace, below that necessary
for steel melting or removal of last traces of carbon, by which the
phosphorous joins the slag, which slag can be removed either before, or after
the tapping of metal.
The tapping of partially purified and dephosphorized but not yet decarbonized
metal, into a ladle, then or it may be directly tapped into a Bessemer
converter, where it is completely converted, or preferably into a Thwaite
vertical or other converter, where it is partially decarbonized, and falls into
a second and high temperature open hearth furnace, provided with overhead
recuperators or regenerators.
The completion of conversion in second open hearth furnace, in which a small
preliminary charge of Hematite pig iron has been melted.
The addition to second open hearth furnace, when dealing with phosphoric pig
t has been partially purified and dephosphorized, of a sufficient weight of
te pig as will provide a film of slag on the surface of metal during its conversion.
The arrangement of recuperator vessels, of the alternate acting or reversible
nstructed above the open hearth furnace, on an independent floor substantially
n and described.
The arrangement of flue connection, between open hearth furnace recuperators
ersing valves, shewn in Figures 9 and 10.
The inclined arrangement of Thwaite converter in conjunction with open hearth
as shewn in Figure 10.
ted this 23rd day of November 1887.
B. H. THWAITE.
J. NOBLE.