Method of Decarbonising, Desiliconising, Dephosphorising, and Desulphurising Fluid Iron Metal from Blast Furnaces or from Cupolas, and Apparatus therefor.
Year: 1885

page_text: Method of Decarbonising, Desiliconising, Dephosphorising, and
Desulphurising Fluid Iron Metal from Blast Furnaces or
from Cupolas, and Apparatus therefor.
I BENJAMIN HOWARTH THWAITE FCS Civil Engineer of Dartmouth Villas
Fountain St Tranmere Cheshire do hereby declare the nature of my invention
for A METHOD OF DECARBONISING DESILICONISING DEPHOSPHORISING AND DESUL-
PHURISING FLUID IRON METAL FROM BLAST FURNACES OR FROM CUPOLAS AND
APPARATUS THEREFOR to be as follows:-
My invention consists in the method and apparatus for treating fluid iron issuing
from the ordinary or other blast furnaces and cupolas prior to charging it into the
open hearth or other steel converting furnace or apparatus for the conversion of
the iron into steel or to the condition of a low carbide of iron. Instead of running
the metal into pig beds direct or directly into a convertor I conduct it, the metal,
into what I term a carbonising cylinder This cylinder which I place in an
inclined position or sloping downwards from the taphole channel I construct as
follows
"
"
The channel for the flow of the metal through the decarbonising cylinder may
be perfectly straight but I prefer to make it zig zag or irregular so that the fluid
metal in its passage along the channel is diverted right and left and bringing all
the molecules of the iron at some period of its flow through the decarbonising
cylinder to the surface. The depth of the channel may vary but I prefer to make
it about 3 inches and of an eliptical sectional form, but I do not confine myself to
this particular configuration.
The channel blocks I may make of basic or of siliceous or other refractory
material but when treating metal which has been reduced from phosphoric ore
I use either dolomitic lime bauxite or magnesite preferring this latter material
which I burn into hard blocks-before fixing in decarbonising cylinder.
I form parallel to this channel and on each side thereof-passages or side flues
for the supply and distribution of air under pressure so arranged that the air
plays on the surface of the metal-in its discursional course through the decar-
bonising cylinder.

page_text: Over the channel flue there is another flue divided from the two side air flues-
and central channel flue, by partitions of refractory material.-The central channel
is connected with the upper-and waste gas of products of combuston flue, by
means of numerous perforations of varying sizes and at graduated distances, the
perforations being larger in size but further apart at the lower end of the cylinder,
but spaced nearer and nearer to each other from the lower to the higher end of the
cylinder the size of the perforations decreasing in size in the same ratio as the
spaces between the perforations or holes decrease through these perforations or
holes the carbon dioxide carbonmonoxide hydrogen nitrogen and other "products
of combustion resulting from the chemical action of decarbonisation et cet "-escape
to the chimney which is fixed at the highest end of the escape flue.
The holes or perforations on each side of the central channel flue are numerously
placed at graduated distances in such a way that the air blast or air under pressure
issues from them directly on to the surface of the metal. I may use such a
pressure of air as will cause it to penetrate through the depth of the flowing
metal-but generally I use such a pressure as will keep the surface of the metal in
a state of ebullition or disturbance as it gradually descends the channel through¯
the decarbonising cylinder.
I connect air blast pipes to each of the air passages at the lower end of the
cylinder.
I also attach to the air passages at their lower termination a connection, with
the flues from the gas producers and also provide an air connection with the outer
air each gas and air connection being provided with a lift valve of the mushroom
type but I may use the forced air blast supply for the combustion of the gas in
the decarbonising cylinder.
Before I open the valve at the upper end of the channel to allow the fluid metal
to pass through the decarbonising cylinder, I burn the gas until the sides of the air
passages, central and waste gas flue, are heated to almost a steel melting point,
when this temperature is attained-I turn of the gas and air and open the upper
valve which allows the metal to enter the decarbonising cylinder-I then turn on
the air blast and as it passes along the highly heated passages and flues it becomes
also highly heated and does not cool the metal with which it is brought into
intimate contact, afterwards the oxidation of the carbon and silicon produces
sufficient heat to maintain the high temperature of the decarbonising cylinder-
which is lined around the basic material forming the passages and flues, with some
highly and neutral refractory material-The decarbonising cylinder is encased with
wrought or with sheet iron made sufficiently tight to withstand the maximum blast
pressure the blocks forming the passages channel and flues of the decarbonising
cylinder are made in segments and so is the casing,--so that repairs can easily be
accomplished.
The metal after leaving the decarbonising cylinder I may run directly into ingot
or other moulds or into pig beds or directly into a convertor or into a Siemens
openhearth furnace, but I prefer to run the metal direct into a ladle-which is
lowered into a specially devised pit to the mouth of the decarbonising cylinder, by
means of hydraulic rams singly or in multiple-the whole action of the decar-
bonising cylinder can be controlled from the ground or shop floor, after the ladle,
which is mounted on trunnions fixed on a carriage, is filled with metal from the
decarbonising cylinder, it, the ladle, is elevated to the level of an over-head railway
from which it is run or propelled by hydraulic, mechanical, or manual labour over
the roof of a Siemens furnace, or other description of steel converting furnace or
vessel, into which the contents of the ladle are tapped-excepting of course the slag
which is allowed to float on the upper surface of the metal to prevent the latter
from cooling in its transmission to the openhearth or other furnaces but I may use
an arrangement at the lower end of the decarbonising cylinder by which I collect
the slag from the surface of the metal in a separate vessel.

page_text: I may tap the metal from the ladle into the Siemens furnace by special loam
lined runners.
By the utilisation of my invention each molecule of the iron along with its
impurities is brought to the surface, and exposed to the free action of the air blast,
hence by this arrangement the sulphur, carbon, and silicon are freely oxidised, and
as each molecule of the phosphorus is brought into contact with the basic surface
of the runner-this impurity freely passes off with the slag-It will be seen that
by turning on the carbonmonoxide or water gas under pressure, and alone-or
without the air-I can recarbonise the metal.
2

page_text: Method of Decarbonising, Desiliconising, Dephosphorising, and
Desulphurising Fluid Iron Metal from Blast Furnaces or
from Cupolas, and Apparatus therefor.
I, BENJAMIN HOWARTH THWAITE F.C.S Civil Engineer Dartmouth Villas
Fountain St Tranmere Cheshire do hereby declare the nature of my invention
for METHOD OF DECARBONISING DESILICONISING DEPHOSPHORISING DESULPHURISING
FLUID IRON METAL FROM BLAST FURNACES OR FROM CUPOLAS AND APPARATUS
THEREFOR, and in what manner the same is to be performed, to be particularly
described and ascertained in and by the following statement :-
The object of my invention is the treatment " of fluid iron issuing from blast
furnaces or cupolas prior to charging it into the open hearth or other steel
converting apparatus for the conversion of the iron into steel or to the condition
of a low carbide of iron. Furnaces and parts connected therewith as made
according to my invention are shown upon 4 accompanying sheets of explanatory
drawings in the drawings the same reference numerals are employed to symbolise
similar or like parts whenever they are repeated.
The accompanying drawings are intended to form part of this specification and
to illustrate practical methods of carrying my invention into effect; but I wish it
to be clearly understood that I do not limit myself to the precise forms and details
therein as they may be varied without deviating from the nature of my invention.
On Sheet A of the accompanying drawings figure 1 is a plan in section, figure 2
is a longitudinal section, figure 3 is a cross section of furnace, figure 4 is an end
elevation of decarbonising cylinder, these figures show the arrangement of my
invention when adapted to a cupola preferably of the Stewart Rapid type and
having a slag separating chamber or furnace at the lower end of the decarbonising
cylinder or converter.
On Sheet of Drawings B figure 1 represents a side elevation of decarbonising
cylinder and its accessories Figure 2 is a plan in section through decarbonising
cylinder or furnace or slag separating chamber. Figure 3 is an elevation of slag
separating chamber of furnace. Figure 4 is a cross section through decarbonising
cylinders and recuperators. Figure 5 is an enlarged detailed section of decar-
bonising cylinder with its air blast mains and jet pipes and valves, and showing
moveable part for the purpose of renewal of basic lining. On Sheet of Drawings C
figures 1 and 2 represent respectively a longitudinal section and plan of my
invention applied in multiple to a blast furnace. In the same sheet of drawings C
figures 3 and 4 represent a longitudinal section of the revolving arrangement of
decarbonising cylinder, and figures 5 and 6 represent cross section and part
side elevation of rocking arrangement of decarbonising cylinder. On Sheet of
Drawings B figures 1 and 2 represent longitudinal section and plan of my
invention applied to blast furnace and showing one arrangement of tapping into
a ladle for transmission of the metal to a Siemens open hearth or other steel
converting furnace, referring to figures on Sheets of Drawings marked A and B.

page_text: A cupola of the Steward Rapid type 7 with its collector 8 (which when treating
phosphoric pig metal) is lined with basic materials 9 and provided with a lime
dust receptacle 10 and when using certain metals I provide with an air jet pipe 11;
the runner 12 connects the collector to the decarbonising cylinder or converter 13
the runner 12 has an arrangement shown at 14 for tapping slag from cupola into
slag waggons running beneath it. The metal falls at the mouth of decarbonising
cylinder into a lip shaped vessel 15 in which slides and closes when required a
refractory plug 16. The metal when running into lip 15 practically forms a
metallic seal and prevents the air blast pressure on the inside from escaping, as the
depth of metallic seal is greater than that of the flow of the metal through
decarbonising cylinder.
The decarbonising cylinder is lined with refractory basic or siliceous material
depending on the nature of the metal to be treated and the lining 17 is dried in
the cylinder in situ, a channel or canal 18 being formed when the decarbonising
cylinder is a fixed one with wavy or zigzag configurations so as to compel the
molecules of the metal to come to the surface to be exposed to the air from air jet-
pipes 19, which for basic linings are formed either through lumps 20 of calcined
magnesite, pieces of chrome ore or other material of an equally neutral character.
The air jet pipes may be kept cool by water circulating through them by ordinary
and well known methods.
The air is distributed through the air jet pipes which divert the air partially
under and partially over the surface of the flowing metal either by means of air
passages, mains or pipes 21. Each jet pipe is provided with a regulating valve 22
and the air mains are provided with a lime dust receptacle 23 by which, when the
metal is highly phosphoric, sulphurous or siliceous, the fluidity of the slag may be
increased by supplying the lime dust to the mains from which it is injected into
the flowing metal, the lower part of decarbonising cylinder 24 is made in such a
manner as to be easily removeable for the purpose of renewal of lining.
The decarbonising cylinder and its permanently fixed accessories are supported
either by a standard 25 or from overhead, in such a way as to permit the lower
part of decarbonising cylinder to be removed, the lower end of decarbonising
cylinder, which is inclined at such an angle found suitable to the character of the
metal, is connected to a furnace or slag separating or finishing chamber 26, the
hearth of which is lined with the same class of acid or basic material as is used for
lining decarbonising cylinder. The hearth of basic may be separated from roof if
of acid or siliceous material by any well known neutral agent.
The gas port 27 is planned so as to divert the pressure of gas on to that of the
air flowing from air port 28. The gas and air enter into their respective ports at
each end of the furnace by tuyeres 29 and 30 the gas uptake 31 being provided
with a mushroom valve 32, the gas is led from a Thwaite gas producer 33 placed
as near as practicable to furnace in order to prevent loss of sensible heat of gas.
The air supply for the combustion of the gas may be taken from the same main
as that supplying air for the decarbonisation by means of the arrangement shown
on figure 4 of Drawings A and B where the air main 34 leading from Roots blower
is led by a stand pipe 35 to a valve 36 by which its supply for decarbonising
cylinder is regulated, unto another valve 37 which regulates the supply for.
supporting gaseous combustion, the air supply enters the reversing valve 38 placed
in this instance at the upper end of and over the decarbonising cylinder from
which by a pipe connections 39 lined with refractory material, it is led through
one of the recuperator cylinders 40 filled with refractory brickwork, the air
passing through recuperator cylinder 40, becomes highly heated, owing to the fact
that prior to the reversal of the valves 39 and 41 the waste heat from decarbonising
cylinder has passed through the identical valves and recuperators on its way to the
chimney, the air after passing through reversing valve 41 at the other end of
recuperator cylinder enters into a main leading right and left to each of the air
tuyeres 30 and may be controlled either by a lift or slide valve as required. The
application of my invention in multiple as shown by figures 1 and 2 Sheet of

page_text: Drawings C the same numerals referring to the respective parts hereinbefore
defined with the following additions 43 is the blast furnace of any known type,
the canal from tap hole is connected by other canals provided with valves to a pair.
of decarbonising cylinders and their accessories as well as to the main runners of
the pig bed. The metal from the two furnaces and their decarbonising cylinders
after having been converted into steel may be tapped into a single ladle 46 and
from thence be run into ingot moulds revolving on a circular turn table working.
in a covered pit 47, provided with crane 48. Figures 3 and 4 Sheet C show the
decarbonising cylinder 13 arranged so as to revolve during passage of metal
through it, and provided with a refractory acid or basic lining and projecting
ledges or shelves 49 so that all the molecules of iron are throroughly exposed to
the action of the air blast or to an oxidising flame which may be passed through
it. The decarbonising cylinder or converter 13 is mounted on friction rollers 50,
motion being imparted by worm wheel 51 the fluid metal from cupola or blast
furnace is led into interior of cylinder by refractory pipe 52.
Figures 5 and 6 on the same Sheet of Drawings show the rocking arrangement
of decarbonising cylinder 13 the air supply for oxidation or decarbonisation is led
by overhead pipe 52, branches therefrom are connected to air jet pipes or tuyeres
by means of curved hollow pistons 53 working circumferentially into the connecting
branches 54 provided with glands by which continual connection is kept between
air supply pipe and decarbonising cylinder; the rocking motion is imparted
either by a crank or as shown by an eccentric 55 on shaft 56. The cylinder
revolves on friction rollers similar to an arrangement shown on figure 3 on the
same Sheet of Drawings.
In figures 1, 2 and 3 on Sheet of Drawings D, instead of the decarbonising
cylinder 13 being above the level of the ground it is placed below it in an inclined
pit; the metal runs into a ladle 57, elevatable by hydraulic telescopic rams 58 to
a level above that of a Siemens or other steel converting furnace, over which it is
run by means of overhead girder 60 and the metal either tapped direct into the
furnace by drop mould 61 or into a runner placed through one of the furnace doors.
The decarbonising cylinder is heated by a gas lip to its lower end by a vertical
flue 62 controlled by valve 63 which is actuated from shop floor by wheel 64 the
air enters from below through valve 65 which is also controlled from shop floor by
wheel 66.
The decarbonising cylinder 13 is provided with side air passages 67 and flue 68
for the escape of products of oxidation. The sides are formed of refractory basic
or siliceous material moulded to special shape, the air jet supply pipes 69 deliver
air into side passages as shown from which it is distributed by numerous openings
through walls of side passages directly on to and under the surface of metal,
the central escape flue 68 leading the gaseous products of oxidation into the
chimney 69.
The upper part of casing of decarbonising cylinder is moveable to facilitate
repairs and renewals, the air supply jet pipes are provided with the regulating air
valves 70 and the air jets or tuyeres are formed of water coil tubes 71.
The modus operandi of the modification shown by figures on Sheets of
Drawings A and B is as follows:-the metal is run from a Stewart cupola
collector vessel which may be lined with siliceous or basic material (depending on
the character of the pig metal used).
The lime dust feeder attached to the top or side of the collector vessel permits
the lime dust to be added to increase the basic character of the slag. Instead of
lime dust I may use fluor spar.
Prior to charging the metal into the decarbonising cylinder or converter I heat
the latter up to a steel melting temperature by the combustion of gas under a
forced blast of heated air-the initial combustion taking place in the slag separating
chamber or furnace placed at and attached to lower end of decarbonising cylinder.
In order to attain a very elevated temperature in decarbonising cylinder, I lead the
products of combustion through recuperator chambers placed above or below but

page_text: preferably above and on each side of decarbonising cylinder. The waste heat from
decarbonising cylinder passes through reversing valves, by which air preferably
under forced pressure is diverted into one recuperator and then the other the
direction of flow of waste heat being diverted simultaneously into the alternate
recuperators and to the chimney.
The high temperature in decarbonising cylinder having been attained the metal
is tapped from cupola collector vessel, and the plug working in special lip at
entrance of decarbonising cylinder is lifted and the metal enters decarbonising
cylinder; the air blast pressure is now turned on to the air jet pipes or tuyeres
which I may water line or form of some highly refractory and neutral material
such as chrome ore-magnesite-bauxite or soap-stone- the outlet air jet pipes being
so fixed as to conduct the air just under the surface of the flowing metal. The
air pressure being regulated to displace the given weight of metal over the air jet
holes part of the air jet holes also distribute the air immediately on to the
surface of the flowing metal.
If the metal is highly charged with phosphoric or other foreign impurities
I increase the basic character of the slag by injecting powdered lime dust along
with the air.
The impurities and carbon in the metal is to be wholly or partially oxidised in
its passage through decarbonising cylinder, if the latter, the impurities of the
metal are further oxidised to the degree required in the reverberatory furnace or
slag separating vessel at the lower end of the decarbonising vessel, by means of
an oxidising flame or by the addition of ore when an increased output is desired,
the metal can be tapped from end of decarbonising cylinder into two or more
finishing furnaces and slag separating vessels and two or more cupolas can be.
attached to one decarbonising cylinder.
usual
When the slag is completely separated from the metal in the reverberatory
furnace or slag separating vessel the metal may then be tapped after
addition of ferro manganese has been made.
If the refractory material forming the lining of the decarbonising cylinder is of
a basic character I prepare and renew it in the following manner-The lower or
that part of casing carrying the channel or canal through the decarbonising
cylinder is moveable, and this I line with the basic material such as magnesite or
dolomitic limestone mixed with anhydrous tar. The peculiar zigzag configuration
of the channel is made by means of a wooden or other mould-around this the
basic material is rammed-after this is done the moveable part is re-attached to the
decarbonising cylinder and the lining is calcined in situ by the heat of combustion,
when all the combined water has been driven out and the lining has shrunk, a
powdered mixture of the identical material used for the lining and mixed with
anhydrous tar should be run into the cracks which may have formed during
expulsion of combined water. The lining after being heated up to steel melting
temperature is ready for receiving the molten metal-During the time the metal
passes through decarbonising cylinder and is exposed to the air blast, the nature of
gaseous combustion is with an excess of gas and therefore a deoxidising one but
if air decarbonising blast is not used, combustion is of an oxidising nature. The
modus operandi of my invention as shown in multiple applications on Sheet C
of Drawings, figures 1 and 2 is as follows:-The metal from blast furnace passes
into distributing channels or beds and is fed into different decarbonising cylinders
or converters placed either radially or parallel with one another as shown. Each
distributing channel is provided with a gate for regulating the flow. The modus
operandi of decarbonising cylinder or converter is similar to that already described.
The metal may be tapped from two or more steel melting furnaces connected with
decarbonising cylinder into one ladle from which the metal is run into ingot
moulds placed on a turn table revolving in a circular pit covered with girders or
brick arches or with brick lined iron cover plates to insure slow cooling of the
ingots.
..

page_text: The modus operandi in modification of my invention shown on Sheet D is as
follows: Producer gas enters the mouth of decarbonising cylinder placed at a
much greater incline than shown in my other modifications, by a vertical flue, its
valve controlled by handle at shop floor. The air for combustion enters by a valve
placed at the lower end of decarbonizing cylinder under a plenum or vacuum
pressure as desired, and combustion ensues at the mouth of decarbonising cylinder-
the flame traverses all the passages therein until the refractory material forming
lining of cylinder and walls of passages is heated to a steel melting temperature,
the metal may then be tapped from blast furnace, and it falls into a lip receptacle
at the inlet to decarboniser by which a molten metallic seal is formed and the gas
or air pressure on the inside of decarbonising cylinder is thus prevented from
escaping; the air pressure for decarbonising the metal is now turned on to the
distributing air mains, escaping in this instance into the heated side passages from
which it passes on to or under the surface of the metal by means of numerous
perforations through side walls of passages. The gases resulting from the action
of oxidation pass through perforations in wall of arch or the central channel into
gas escape flue through which they pass up to the chimney, the metal runs into a
ladle from which it is elevated to a height above the level of a Siemens furnace
into which it is tapped on completion of process of conversion.
The following are some of the advantages which will accrue from the use of
my invention :-
1. The fractional oxidation system will conduce to the production of a steel of a
more homogeneous, character.
2. The production of steel by the Siemens-Martin or the Siemens open hearth
process will be considerably accelerated.
3. There will be less difficulty in renewing the basic lining than in the Bessemer
converter.
4. The plant for the production of a given output of steel in a given time will
be less costly than by the use of either Bessemer's or Siemens' process.
5. The air blast pressure of the various jets is to be regulated according to
the action of decarbonisation required at the various stages in the progress of the
metal through decarbonising cylinder. It is not intended to entirely oxidise the
carbon in the passage of the metal through decarbonising cylinder but to reduce it
to say 1 per cent., and then during the time the slag separates from the metal in
the bath of the reverberatory or open hearth furnace to oxidise the remainder by
an oxidising flame or by the addition of ore, ferro can be added in the usual way
if required prior to tapping. The recuperative arrangement is not liable to be
affected through dampness of subsoil, the recuperators are portable and the
refractory material can be easily removed and examined. The valves are simple
and not liable to be put out of order and there is no danger of explosions due to
complications of reversing arrangements; the furnace and its accessories can at
small cost be removed from one place to another. The sensible heat of producer
gas is utilised and combustion is under pressure. Recuperation is applied only to
beating air.
6. The basic lining is intended to be calcined in situ, thus rendering expensive
kilns unnecessary, and as soon as the combined water has been expelled and the
lining heated to steel melting heat, it is ready for the reception of the metal.
7. By a thorough exposure of the molecules of the metal it is expected that the
sulphur will be entirely eliminated.
8. The basic action of the slag will be considerably increased by the system of
lime dust injection with air, and prove more effective in eliminating impurities.
When the pig metal has a low percentage of carbon I may confine myself to the
use of an oxidising nature of combustion in decarbonising cylinder for effecting the
necessary decarbonisation and oxidation of the other foreign impurities of the metal
in the decarbonising cylinder.

page_text: Having now particularly described and ascertained the nature of my inven-
tion and in what manner, the same is to be performed I wish it to be clearly
understood that I do not claim the method of decarbonising metal flowing through
a cylinder by blasts of air as this is not new, but what I do claim is this:-
1. The combination of a decarbonising cylinder to effect an intermediary
conversion process between a blast furnace or cupola and an open hearth furnace
for the conversion of the metal into the condition of a low carbide of iron known
as steel, substantially as herein shown and described.
2. The use of such decarbonising cylinder to effect decarbonisation and the
oxidation of impurities in the metal by the use of an oxidising flame passing
through decarbonising cylinder in close contact with surface of metal, substantially
as herein shown described.
3. The system of lining decarbonising cylinder with basic material and method
of renewing such lining.
4. The system of inducing the transmission of the molecules of the metal and
its impurities to the surface by a configuration of channel or by revolution or
Oscillation of decarbonising cylinder, substantially as herein shown described.
5. The combination of decarbonising cylinder with a cupola and collector of the
Stewart Rapid type.
6. The arrangement of cylindrical recuperative chambers in combination with
decarbonising cylinder and open hearth furnace or slag separating vessel, sub-
stantially as herein shown described.
7. The method of increasing the basic character of slag in decarbonising
cylinder by the injection of lime dust along with the air, substantially as herein
shown described.
8. The general and detailed arrangement of my invention in its various
modifications, substantially as herein shown described.