The invention provides an arrangement for steelmaking comprising a steel melt and initial reaction chamber arranged to receive source material in the form of scrap and/or pre-reduced iron, an overhead lance for the introduction of an oxidizing gas to the initial reaction chamber, means for introducing, below the level of the surface of the melt in the reaction chamber, a melt stirring fluid medium, means for introducing carbonaceous material into the melt; a secondary refining chamber connecting with the initial reaction chamber at the surface level of the melt and through which the metal is arranged to pass from the initial reaction chamber; and a melt holding vessel into which the metal is passed from the secondary refining chamber.

This invention relates to steelmaking, and more particularly processes and 
apparatus for continuous steel-making having an input source of solid 
ferrous bearing material and an output of refined or partially refined 
steel. 
Numerous proposals have been made for continuous steel-making processes; 
the premise essentially being that a continuous process should be capable 
in principle of greater cost effectiveness than batch processes for the 
production of steel. 
The majority of earlier proposals have been based upon a source material of 
blast furnace iron sometimes together with ferrous scrap although some 
processes proposed have avoided the need for blast furnace material and 
utilised a starting material of ore or prereduced ore together at times 
with ferrous scrap. 
It is an object of the present invention to provide an arrangement for 
continuous steelmaking capable of the efficient production of refined or 
partially refined steel. 
According to one aspect of the invention there is provided apparatus for 
steel-making comprising a steel melt and initial reaction chamber arranged 
to receive source material in the form of scrap and/or pre-reduced iron, 
an overhead lance for the introduction of an oxidising gas to the initial 
reaction chamber, means for introducing, below the level of the surface of 
the melt in the reaction chamber, a melt stirring fluid medium, means for 
introducing carbonaceous material into the melt; a secondary refining 
chamber connecting with the initial reaction chamber at the surface level 
of the melt and through which the metal is arranged to pass from the 
initial reaction chamber; and a melt holding vessel into which the metal 
is passed from the secondary refining chamber. 
The secondary refining chamber may be of limited depth compared to that of 
the initial reaction chamber, and may be constituted by a launder. 
Alternatively the secondary refining chamber may have a depth of the same 
order as the initial reaction chamber and may act as a recognisable 
reaction container, possibly incorporating means for injecting stirring 
gases or reagents into melt therein. 
Again the secondary refining chamber may comprise a launder followed by a 
reaction container. 
It will be understood that a slag or flux will be carried by the molten 
metal within the secondary refining chamber. 
According to another aspect of the invention there is provided a method of 
steelmaking comprising subjecting source material in the form of scrap 
and/or pre-reduced iron to melting and initial reaction in an initial 
chamber by the introduction from overhead of an oxidising gas, by the 
introduction below the level of the surface of the melt of a stirring 
fluid medium, and by the introduction of carbonaceous material; subjecting 
the melt to secondary refining in a secondary chamber connecting with the 
initial chamber at the surface level of the melt. 
The arrangement may be such that a slag or flux on the surface of the 
molten steel travels at a different speed or in counter-flow to the metal 
in passage through a launder consisting of or forming part of the 
secondary refining chamber. Such an arrangement assists slag/metal 
chemistry. 
It will be appreciated that in such an arrangement melting occurs in the 
initial reaction chamber, and metal continuously passes to and through the 
launder where full slag/metal separation and chemical equilibration occurs 
resulting in a reduction in the sulphur content of the melt via slag/metal 
reactions encouraged by the differing rate of flow of slag and metal. 
Where the secondary refining chamber comprises a reaction container 
incorporating means for injecting stirring gases and reagents, desired 
refining reactions can be attained therein to modify the slag and metal 
compositions. 
The output steel may be fed directly to a metal holding vessel, at which 
stage an essentially batch process is in effect, with the possibility of 
further refining and/or compositional control in the holding vessel. 
By this arrangement we believe it is possible to achieve the cost and 
energy benefits of continuous steel making, including energy generation 
and usage possibilities inherent therein, whilst avoiding the special 
problems of in line compositional control and casting of a stream of metal 
of initial crude composition. These problems include metal reoxidation and 
transportation and the need to ensure the provision of a stream of 
constant mass flow, composition, and temperature. 
The arrangement may be such that offtake gases from the initial reaction 
chamber and from the refining chamber pass above the refining chamber so 
that a proportion of the heat from the offtake gases is transferred to the 
metal and slag therein. 
Various refining fluxes and reagents may be introduced both into the 
initial reaction chamber and into the secondary refining chamber in order 
to effect, wholly or in part, the bath chemistry. 
A slag dam and weir may be provided adjacent the metal outflow position 
from the refining chamber, thereby allowing passage of slag free metal 
into the metal holding vessel and assisting counter-flow of slag which can 
be arranged for tapping on a side of the initial reaction vessel remote 
from the launder. 
The output molten steel holding vessel may be arranged for final 
compositional control of the steel. The vessel may be of a double chamber 
form of the kind covered by our copending United Kingdom Patent 
Application No. 82.18203. 
Means may be provided for introducing steam into the arrangement. Thus 
means may be provided for introducing steam into the offtake gas passage 
so as to enable the water gas shift reaction to occur i.e. the reaction of 
carbon monoxide present in the offtake gas with the steam to generate 
hydrogen. By this means the off-gas can be adjusted in composition, 
particularly with respect to the CO/H.sub.2 ratio which may be desirable 
for optimising gas usage. 
Steam may also be introduced into the melt within the reaction vessel so as 
to provide a control of heat liberation within the melt and/or control of 
off-gas composition. 
The offtake gases from the arrangement may be used for preheating and/or 
pre-reducing the source material for the initial reaction chamber. 
In one embodiment a direct reduction furnace may be arranged to feed direct 
reduced iron to the initial reaction chamber and in this case the offtake 
gases may be utilised as a reductant in the direct reduction furnace. 
The output from the direct reduction furnace may be fed directly to the 
initial reaction chamber in a hot condition, such as at approximately 
800.degree. C., thereby reducing the energy requirements for melting. 
With an arrangement of this kind it is possible to provide an output 
product from the direct reduction furnace having a lower metallisation 
than would be normally acceptable (normal metallisation requirements being 
of the order of 90% or more) because reduction can readily be completed in 
the initial reaction chamber. With a limited metallisation requirement of 
the kind envisaged, it is possible in practice to limit offtake gas usage 
in the reduction furnace to one pass, the output gas therefrom being 
usable as a fuel elsewhere in the plant. 
The initial reaction chamber and the secondary refining vessel may be 
operated at above atmospheric pressure, such as at between 3 and 6 
atmospheres. By this means propulsion for the offtake gas through the 
direct reduction furnace is provided, and slag foaming in the initial 
reaction chamber, with its associated control and melting rate limitation 
problems, is very significantly reduced.

Referring now to FIG. 1 it will be seen that the apparatus comprises in 
initial reaction chamber 1 for the initial melting and refining of molten 
steel. A refining and heating gas (usually oxygen) is directed onto the 
upper surface of the melt within the chamber by means of a lance 2. 
Feedstock is provided via a hopper 3 and a conveyor belt 4 and comprises a 
pre-reduced iron in granular or pelletised form. Alternatively the 
feedstock could be prepared scrap, granulated blast furnace iron, or other 
ferrous source material. 
Tuyeres 5 are provided in the base of the reaction chamber 1 through which 
carbonaceous material such as coal (for heating purposes) together with 
oxygen and/or an inert gas for melt stirring purposes may be injected. 
Appropriate refining fluxes may be added via an inlet pipe 6 located above 
the reaction chamber 1. 
A launder 7 (constituting a secondary refining chamber) is connected to one 
side of the reaction chamber through which output metal from the reaction 
chamber flows. A slag dam 8 and metal weir 9 is provided adjacent the 
output end of the launder 7, and a slag output port 10 is provided on the 
opposite side of the chamber 1 to the launder so that counter-flow between 
slag and molten metal is accomplished within the launder. Slag flowing 
from its outlet port 10 is collected in a slag ladle 11 of normal 
configuration. 
It is to be observed that an additional inlet 12 for fluxes above the 
launder is provided and that the gas offtake passage 13 extends above and 
along the launder before being directed upwardly away from the apparatus. 
Molten metal passing from the initial reaction chamber 1 through the 
launder 7 is subjected to refining and compositional control by means of 
the added fluxes and by means of slag/metal reactions. In some 
arrangements additional oxygen may be added to the slag/metal as it passes 
through the launder. 
On leaving the launder, the metal passes into a holding vessel 14 which is 
of the kind described and illustrated in detail in our copending United 
Kingdom Patent Application No. 82.18203. Essentially the vessel comprises 
two chambers 15 and 16 in one of which 15 the incoming steel is heated by 
arc electrodes 17. In the other chamber 16 compositional control by vacuum 
and/or purging processing (vacuum being provided via pipe 18) and by the 
addition of alloy materials and reagents (through pipe 19) can be carried 
out. It will be observed that the wall 20 separating the two chambers of 
the vessel is pierced by ports 21 and 23, and that gas is bubbled into 
both chambers via tuyeres 22. By this means movement of metal between the 
two chambers is assured. After completion of the necessary compositional 
control, the refined steel may be transferred to a casting station for 
casting in a normal manner. 
The variant of the invention illustrated in FIG. 2 is essentially similar 
to the apparatus of FIG. 1 except that the initial reaction chamber 1 is 
extended as shown at 24 into the final refining launder 7 so as to provide 
additional time, and metal volume, to achieve equilibrium of reaction. 
The arrangement of FIG. 2 also illustrates variation in the mode of 
addition of carbonaceous material to the reaction chamber 1. Thus powdered 
coal is injected via the overhead oxygen lance 2, the basal tuyeres 5 
being used for the injection of oxygen or oxygen containing gas and/or 
inert gas for melt stirring purposes. In yet another variant (not 
illustrated) coal may be added to the reaction chamber 1 in granular or 
lump form by means of an overhead chute in association with bath stirring. 
An alternative or additional variation (not illustrated) of the arrangement 
of FIG. 1 provides a weir located between the initial reaction chamber 1 
and the refining launder 7 so as to enable slag and metal droplets only to 
be carried into the refining launder. A slag output port will be provided 
from the refining launder. 
In yet another variant of the arrangement illustrated in FIG. 1 movement of 
molten steel through the refining launder can be by means of electro 
magnetic inductors up an inclined base of the launder. In this way slag 
will naturally flow counter to the metal travel direction, and the 
requirement for a slag dam at the exit from the launder is removed. 
The apparatus shown in FIG. 3 is basically in terms of operation very 
similar to that of FIG. 1 and similar parts have been allocated the same 
reference numbers. There are a number of physical variations however. 
Thus it will be seen that slag is tapped from a tap hole 25 part way along 
the launder 7. 
It will also be noted that the secondary refining chamber comprises not 
only the launder 7 but also a reaction container 26 within which is 
located the slag dam 8. A tuyere 27 is provided within container 26 for 
the provision of stirring and/or refining gases to the steel within the 
container. 
The apparatus illustrated in FIGS. 4 and 5 constitutes an extension of the 
arrangements hereinbefore described to include an inline direct reduction 
furnace. In this arrangement a continuous melting and refining unit 30 is 
connected to a direct reduction shaft 31 of a kind generally known for 
reducing pelletised and/or lump ore to iron. 
The continuous melting unit 30 may be fed with either hot DRI from the 
shaft furnace 31 or with cold DRI (direct reduced iron) from a storage 
hopper 32 together with coal from hopper 33 and oxygen via lance 34. The 
melting process produces gas at a pressure of up to five bar and this may 
either be passed directly to a waste gas duct 35 via pressure reducing 
valve 40 or to the direct reduction shaft via duct 60. In either case the 
gas would be cooled, via direct contact cooler/scrubbers 36 or 37 
respectively, although when feeding gas to the direct reduction shaft the 
gas would only be cooled to about 800.degree. C. The direct reduction 
shaft 31 has reducing gas fed in via a toroidal bustle (not shown), and 
passes in counter-current through a bed of pellets to emerge at the top of 
the shaft. The shaft is operated at elevated pressure comparable with the 
melter unit 30 operating pressure, and in this configuration pumping of 
the gas is not required. The top-gas leaving the d.r. shaft is cleaned and 
fully cooled to around ambient temperature by means of a direct contact 
cooler/scrubber 38 before discharging through a pressure reducing valve 39 
into waste gas duct 35. Alternatively the cooled/scrubbed gas can be 
connected at 42 for recycling into the duct 60 or use as a fuel elsewhere 
in the plant. 
The shaft is fed with either ore or DRI via a lock hopper arrangement 41 
the hot DRI product from the shaft being passed through a discharge valve 
into the melter unit 30. The purpose of feeding DRI to the shaft is to use 
it as a preheater to enable a higher feed rate of hot DRI to be melted 
than could be produced by the shaft working as a reduction unit. 
The system incorporates reception hoppers 43,44 to allow transport of the 
raw materials directly into the plant and storage facilities in bins 
32,33,45 and 46 for at least one day's requirements, and transport systems 
to transfer each of the raw materials to the point of use. 
The melting and refining unit 30 consisting of an initial reaction (or 
melting) chamber 47 and a secondary refining container 48 linked together 
by a short launder 49, as shown in FIG. 5. Operation of the unit relies on 
the continuous input of raw materials to produce a liquid melt and a 
continuous supply of gas which is passed from the unit through a gas 
treatment plant, to become the reducing gas for the Direct Reduction Shaft 
31. To provide the off-gas with sufficient driving force to pass through 
all the pipework and the direct reduction shaft it is necessary to operate 
the unit 30 at a relatively high pressure, up to a maximum of 5 
atmospheres. The unit 30 is therefore a pressure vessel operating with an 
internal temperature of at least 1600.degree. C. and as such its shell 
design, construction and choice of refractories is more critical than for 
conventional steelmaking. During continuous melting operations lasting 
over several days steady state heat loss from the vessel must be expected, 
therefore a composite refractory construction is provided comprising of a 
magnesite based working lining (for example) coupled with an insulating 
backing lining. Water cooled panels at strategic areas and in the roof 
section may be provided. 
Operating under pressure inside the melter unit also means that oxygen 
lance 50, materials addition chutes such as 51 and 53, and measurement 
ports 52, must all be sealed to prevent an egress of hot gas containing a 
high percentage of carbon monoxide, yet be capable of allowing a 
continuous supply of materials to be added, and in the case of the oxygen 
lance, allow relative movement inside the vessel. 
In operation the melting chamber 47 is charged with hot metal to provide a 
liquid heel. DRI from furnace 31 is added through the charging system 51 
located on the roof into the metal bath. Coal can be added as lump form 
through chute 53 in the roof, or injected in powder form from coal powder 
silo 61 through the central hole of a specially designed oxygen lance (not 
shown). The liquid bath is stirred by the injection of an inert gas e.g. 
nitrogen, through a tuyere 54 located in the base of the unit. The 
stirring action assists in the assimilation of the coal and in the melting 
of the DRI material. Oxygen is blown through a top lance 50 in a manner 
similar to conventional BOS steelmaking, and is used to combust the coal, 
the heat of combustion being used to melt the DRI charge. Additions of 
lime from bin 46 are also made via chute 55 to flux the gangue material 
from the coal and the DRI, which forms a slag in the melting chamber 47. 
When all the inputs are matched the rate of heat generation should balance 
the melting requirements and maintain the bath at a constant temperature, 
as well as providing an off-gas of constant composition and flow rate. The 
level of the liquid bath inside the melting unit is held constant, the 
depth being dictated by the height of the launder 49, and therefore a 
volume of liquid metal equal to the DRI input rate is constantly 
overflowing into the launder. The action of the oxygen jet causes the slag 
layer to foam, which together with particles of metal trapped inside the 
foam, moves into the launder 49. The launder permits the collapse of part 
of the slag foam as the metal and slag passes therethrough. 
The slag and metal overflow from the melting chamber 47 into the refining 
container 48, which initially acts as a decanting and settling chamber. 
The refining container is then allowed to fill up, which gives the 
opportunity to stir the melt using stirring gases passing through a basal 
tuyere 56. The liquid metal flowing into this container will be reasonably 
high in carbon concentration, but it will also be high in sulphur since 
the majority of the sulphur contained in the coal added in the melting 
chamber will pass into the metal. There are therefore several courses of 
action possible in the refining container. Firstly, the high carbon, high 
sulphur melt, after settling, can be tapped with no internal treatment, 
allowing decarburisation and desulphurisation to be performed externally; 
secondly, oxygen can be blown into the melt (possibly through the basal 
tuyere) to decarburise and allow a low carbon, high sulphur melt to be 
tapped; or thirdly, carry out a desulphurising treatment within the 
refining container and tap out a high carbon, low sulphur melt. With this 
third option, the stirring of the melt, together with top additions of 
deoxidants through chute 58 should form the slag into a state with a high 
sulphur partition value. Once desulphurisation has taken place, then the 
active contents of the refining unit can be tapped out in a controlled 
manner using a combination of a sliding gate valve situated in the base of 
the unit (not shown) and side top holes 57 operated similar to a blast 
furnace tapping procedure. During all of these operations fresh slag and 
metal will be entering the refining container from the melting chamber. 
Tapping of the refining container will take place once it approaches its 
capacity and the various refining steps have taken place. 
The integration of a coal based melting unit with a direct reduction plant 
offers the possibility of a self-contained production unit with no excess 
gas production. This could be achieved by taking hot gas from the melting 
unit 30 (through duct 60) and mixing it with recycled top-gas from the 
direct reduction shaft 31 after removal of oxidised species from the 
top-gas (as shown at 42). This configuration would allow the production of 
highly metallised sponge iron which would then form the metallic feedstock 
to the melter unit. A further energy economy is available when the direct 
reduction and melting units are closely integrated, by transferring the 
sponge iron in a hot condition to the melter unit and thus reducing the 
coal input requirement. 
An alternative configuration is possible in which the melting unit off-gas 
could be cooled to the required shaft inlet gas temperature 
(.about.800.degree.-900.degree. C.) and passed only once through the 
direct reduction shaft. The top-gas from the shaft would then be available 
as fuel for use in finishing processes and for steam raising to power 
machinery drives. In order to achieve a balance between the melting unit 
off-gas production and the direct reduction shaft requirement the sponge 
iron would be produced at less than full metallisation, and the residual 
oxide phases would be reduced in the melting unit by the addition of coal. 
Improved energy efficiency by hot charging of sponge iron is also possible 
in this method of operation. Whilst a `once through` gas flow circuit 
would require a higher energy input per output tonne than a recycle system 
there can be substantial capital cost savings by eliminating the gas 
treatment equipment needed for scrubbing oxidised species and 
recompression, and the energy surplus is available as fuel for associated 
processing stages. 
By way of example metallisation ratios of 70%, to even as low as 40% can be 
provided in the output from furnace 31. This compares most significantly 
with a normally required metallisation level of well over 90%.