Fuel and oxygen addition for metal smelting or refining process

A furnace 10 for smelting iron ore and/or refining molten iron 20 is equipped with an overhead pneumatic lance 40, through which a center stream of particulate coal 53 is ejected at high velocity into a slag layer 30. An annular stream of nitrogen or argon 51 enshrouds the coal stream. Oxygen 52 is simultaneously ejected in an annular stream encircling the inert gas stream 51. The interposition of the inert gas stream between the coal and oxygen streams prevents the volatile matter in the coal from combusting before it reaches the slag layer. Heat of combustion is thus more efficiently delivered to the slag, where it is needed to sustain the desired reactions occurring there. A second stream of lower velocity oxygen can be delivered through an outermost annulus 84 to react with carbon monoxide gas rising from slag layer 30, thereby adding still more heat to the furnace.

FIELD OF THE INVENTION 
This invention concerns a process and an apparatus for introducing oxygen 
and a carbonaceous fuel into a smelting and/or metal refining furnace. In 
particular, the invention concerns the introduction of oxygen and 
carbonaceous fuel into the furnace through a lance in such a manner that 
the volatile matter content of the fuel is combusted in a fashion 
permitting optimum utilization of the heat of combustion in the smelting 
or refining operation. 
DESCRIPTION OF THE PRIOR ART 
It is known that a pneumatic lance device may be used to introduce oxygen 
and solid materials into a furnace for refining molten metals. The lance 
may be used to introduce oxygen alone or to introduce both oxygen and 
solid fuel concurrently. This is common in the refining of ferrous 
materials such as iron melts to produce steel. 
During a typical iron refining process, oxygen alone is delivered to the 
iron melt, utilizing a pneumatic lance, in order to partially oxidize the 
carbon in the melt, thereby reducing the carbon content of the iron. The 
incompletely oxidized carbon rises and escapes from the melt as carbon 
monoxide. Additional heat of combustion is available if the carbon 
monoxide is further oxidized to carbon dioxide before the CO escapes from 
the furnace. It is known to utilize a second stream of oxygen above the 
melt to oxidize the CO in the vicinity immediately above the melt, thereby 
capturing the energy released by this reaction. 
Typically, in the refining of molten iron, quantities of steel scrap are 
added to the process. In order to prevent cooling and solidification of 
the molten bath from the addition of the scrap, it is known to add 
quantities of solid fuel, commonly carbonaceous material, to the process 
to create heat. This has been accomplished by utilizing a lance to deliver 
both oxygen and carbonaceous material to the melt. The carbonaceous 
material is injected into the molten bath to recarburize the melt, and 
oxygen is simultaneously injected into the molten bath. The oxidation of 
the additional carbon and the subsequent secondary oxidation of the 
resulting carbon monoxide result in the release of sufficient additional 
energy to maintain the temperature of the melt and to melt the cold scrap 
additions. 
Top-blowing systems have been described for introducing both solid fuel and 
oxygen to the melt of a metal refining operation. Metz et al., U.S. Pat. 
No. 4,434,005, issued Feb. 28, 1984, describe a method of introducing 
carbon and oxygen into the melt of a refining operation by means of a 
blowing device. Mercatoris, U.S. Pat. No. 4,533,124, issued Aug. 6, 1985, 
uses a blowing apparatus containing a chamber filled with inert gas to 
separate the oxygen and the solid material during transport through the 
apparatus. With these devices and methods, the carbon and the oxygen are 
not separated after they exit the blowing apparatus. This can lead to 
premature combustion of the fuel, unless the fuel and oxygen are injected 
into the melt at very high velocities. Moreover, these devices and methods 
do not permit the utilization of the carbon or the oxygen for processes or 
reactions that may be desired in a slag layer on top of the melt. Further, 
volatile matter in the carbon may be permitted to escape before reaching a 
location where it can be combusted and the heat of combustion utilized. 
SUMMARY OF THE INVENTION 
The present invention is a process for combusting carbonaceous material and 
oxygen in a smelting and/or refining operation, and an apparatus for 
delivering the carbonaceous material and oxygen to the furnace in which 
the operation is being performed, that have certain advantages over the 
prior art processes and apparatus. In the process, the carbonaceous 
material and the oxygen are introduced from overhead in the form of nearby 
streams, and a stream of inert gas is interposed between the carbonaceous 
material and the oxygen streams, thereby preventing commingling of the 
fuel and oxygen during transport. By keeping the carbonaceous material and 
oxygen separated, premature combustion of the carbonaceous material can be 
prevented, without having to use such high stream velocities that the 
carbonaceous material is propelled deep into the melt. By using the lower 
injection velocity, the carbonaceous material can be made available for 
smelting reactions such as reducing iron ore to elemental iron, using the 
carbonaceous material as a reducing agent, or other types of reactions 
that are desired within the slag layer. By separating the carbonaceous 
material and oxygen until the carbonaceous material stream is well within 
the slag layer, but not through it, that is, not reaching the underlying 
melt, combustible volatile matter in the carbonaceous material can be made 
to combust in the slag layer, so that the heat of that combustion is 
better utilized to sustain the reactions occurring in the slag layer 
and/or the melt. 
Carbonaceous material used as fuel generally contains combustible volatile 
matter. For example, coal used in the reduction of iron ore may contain 
volatile matter such as hydrogen, which is utilized as a fuel source to 
generate the necessary heat for the reaction. Examples of other suitable 
sources of carbonaceous material are coke, graphite, char, and hydrocarbon 
gases or liquids, (e.g., petroleum products). The carbonaceous material is 
propelled toward the slag layer with sufficient velocity to prevent 
substantial devolatilization until the carbonaceous material has 
penetrated the slag layer. Concurrently, oxygen is also propelled toward 
the slag layer, and the carbonaceous material and oxygen streams are kept 
separate during transport to the slag layer by means of the inert gas 
stream interposed between the oxygen and the carbonaceous material, thus 
preventing premature oxidation or combustion of the carbonaceous material. 
By "inert gas" is here meant a gas that, under the conditions of the 
process, is essentially nonreactive with both the carbonaceous material 
and the oxygen. Examples of suitable inert gases include nitrogen, argon, 
carbon dioxide, steam, and off-gas combustion products. 
The velocities of the carbonaceous material stream and the oxygen stream, 
and the distance of separation of the two streams are preferably selected 
so that the volatile matter in the carbonaceous material is combusted at 
some point below the surface of the slag layer, but above the surface of 
the melt. Usually the velocity of each stream will be about Mach 0.75 or 
higher. As a result of the combustion in the slag layer, at least a 
portion of the energy released as heat of combustion of the volatile 
matter is utilized by the smelting or refining operation in the slag 
layer. 
In one embodiment of the invention, the carbonaceous material is introduced 
in a center stream which is shrouded by the inert gas stream and is 
thereby separated from the oxygen, which is introduced in the form of at 
least one outer stream. 
A preferred embodiment of the invention utilizes the process in the 
combined smelting of iron ore and refining of molten iron utilizing 
particulate coal as the carbonaceous material and argon or nitrogen as the 
inert gas. The coal is preferably delivered in a stream at a speed of 
between about Mach 0.75 and about Mach 2, surrounded by the nitrogen or 
argon stream delivered at about Mach 0.5 to Mach 1.5, and the oxygen outer 
stream is preferably delivered at a speed of about Mach 0.75 to Mach 2.0. 
The three streams are injected into a slag layer which is a minimum of 
about 0.5 meter in thickness, the slag layer resting on top of the molten 
iron bath. 
An especially preferred embodiment of the invention uses a lance to deliver 
the three streams, with the protective inert gas stream being an annular 
stream (i.e., in the form of a hollow cylinder) having a thickness of 
about 0.75 to 3.0 millimeters at the point where it exits the lance. The 
coal and the inert gas are kept separate during the transport to the slag 
and until the coal has penetrated deep within the slag layer. It is an 
objective of this process to prevent the volatile matter of the coal from 
escaping to the furnace atmosphere. It is a further object to combust the 
volatile matter and to thereby utilize the heat of combustion of the 
volatile matter to advance the desired chemical reaction or reactions 
occurring in the slag layer and/or the melt. 
Another aspect of the invention concerns a pneumatic lance for delivering 
the carbonaceous material and oxygen to a furnace in which reactants are 
heated, in such a manner that the two streams are separated by an inert 
gas stream, thereby delaying contact of the carbonaceous material and 
oxygen streams. The lance comprises a central core surrounded by a first 
annular opening through which the inert gas is ejected and a second 
annular opening surrounding the first annular opening. Either the oxygen 
or carbonaceous material can be propelled through the central core and the 
other through the second annular opening. The central core can be 
constructed, or example, of pipe having a wall thickness of about 4 to 7 
millimeters. Preferably, the carbonaceous material is ejected from the 
central core, while the oxygen is ejected from the second annular opening 
at an angle of about 10 to 45 degrees, more preferably about 15 to 20 
degrees, from the axis of the carbonaceous material stream. It is 
preferred that the diameter of the central core be about 20 to 40 
millimeters, more preferably about 20 to 30 millimeters; that the width of 
the first annular opening be about 0.75 to 3 millimeters, more preferably 
about 0.75 to 1.25, or even 0.9 to 1.1, millimeters; and that the width of 
the second annular opening be about 19 to 50 millimeters, more preferably 
about 19 to 25 millimeters. 
The lance preferably is comprised of an elongated body member containing 
inlet and discharge ends for the carbonaceous material, inert gas and 
oxygen streams. It is preferred that the flow of the carbonaceous material 
be through the central core, surrounded by the simultaneous flow of the 
inert gas through the first annular chamber, and the simultaneous flow of 
the oxygen through the second annular chamber. However, it is possible for 
the flow of the oxygen to be directed through the central core and the 
flow of the carbonaceous material to be directed through the second 
annular chamber. The lance incorporates means for delivering the 
carbonaceous material to the, inlet end of the central core or the second 
annular chamber, means for delivering the inert gas to the inlet end of 
the first annular chamber and means for delivering the oxygen to the inlet 
end of the central core or the second annular chamber, whichever is not 
connected to the carbonaceous material feed line. 
Preferably the lance is equipped with a detachable injection nozzle for the 
discharge ends of the tubular core, the first annular chamber, and the 
second annular chamber. The nozzle preferably has a central opening that 
is of the same approximate size as, and is lined up with, the central 
core, a ring-shaped opening that is of the same approximate size as, and 
is lined up with, the first annular opening, and a series of about 6 to 16 
dispenser openings lined up with the second annular opening, the openings 
preferably having a total cross-sectional area of at least about 1,000 
square millimeters. The dispenser openings can be cylindrical bores evenly 
spaced around the second annular opening, each at an angle of about 10 to 
45 degrees outward from the central core's axis. The bores have sufficient 
length to impart direction to the flow of the material, preferably oxygen, 
being discharged from the second annular opening. It is preferred that the 
central core be constructed of a removable pipe to permit changing of the 
core in the event of solids plugging. The nozzle may be designed so that 
the discharge speed of each of the three streams is subsonic or 
supersonic. 
The lance may optionally be equipped with a third annular chamber 
surrounding the second annular chamber, the third chamber also having 
inlet and discharge ends. In this embodiment the lance includes means for 
delivering oxygen to the third chamber, and preferably it includes means 
for directing the oxygen flowing out of the third chamber in an outward 
direction at an angle of about 10 to 30 or 35 degrees from the direction 
of flow of the other stream of oxygen as it leaves the lance. By use of 
this version of the lance, a primary stream (or "hard blow") of oxygen can 
be ejected through the second annulus at a velocity sufficient to 
penetrate the slag layer to combust incompletely therein volatile matter 
from the carbonaceous material, while a secondary stream (or "soft blow") 
of oxygen can be ejected through the third annulus. Carbon monoxide formed 
from the incomplete combustion in the slag rises, and the secondary oxygen 
stream provides combustion above or just below the surface of the slag of 
at least a portion of the released carbon monoxide, thus supplying 
additional heat to the process. The velocity of the secondary oxygen 
stream will often be from about Mach 0.70 or 0.75 to about Mach 1.8. 
These and other features, aspects, and advantages of the present invention 
will become better understood with reference to the following description, 
appended claims, and drawings.

DETAILED DESCRIPTION AND PREFERRED EMBODIMENT OF THE INVENTION 
Referring to FIG. 1 of the drawings, a general schematic section of a 
furnace 10 in which the process of the invention is to occur is shown. 
This can be any of a number of types of furnaces commonly known to those 
skilled in the art and used for the refining or smelting of metals and 
their ores. In the preferred embodiment depicted in FIG. 1, iron ore is 
being reduced to iron and the resulting iron is being refined. 
As shown schematically in FIG. 1, in furnace 10 molten iron 20 is being 
refined and iron ore is being reduced. A molten foamy slag layer 30 
containing the iron ore is resting on the molten iron. Particulate coal 
53, containing volatile matter, is propelled toward slag layer 30 as the 
central stream of a pneumatic lance 40, while oxygen 52 is introduced in 
the form of an outer annular stream from the lance. The coal 53 and oxygen 
52 are kept separate after they exit the lance by means of an annular 
stream of nitrogen 51. The coal 53 is discharged from the lance at a speed 
of about Mach 0.75 to Mach 1.2. The oxygen 52 is discharged from the lance 
at a speed of about Mach 0.5 to Mach 1.5. The nitrogen 51 is discharged 
from the lance at a speed of about Mach 0.75 to Mach 1.2. 
The coal 53, oxygen 52, and nitrogen 51 are injected into the foamy slag 
layer 30 resting on top of the molten iron 20. The thickness of the slag 
layer is maintained at least about 0.5 meter, preferably at least about 
1.0 meter. 
To maintain the separation of the carbon 53 and oxygen 52, the thickness of 
the annular nitrogen stream 51 is maintained at about 0.7 to 1.2 
millimeters, at the point where it exits lance 40. 
The slag layer 30 thickness, the velocities of the coal 53, oxygen 52, and 
nitrogen 51, and the thickness of the annular nitrogen shroud 51, are 
maintained so that at least a portion of the volatile matter in the coal 
remains in the coal stream until it has penetrated into the slag layer. 
Similarly, contact between a substantial portion of the coal 53 and the 
oxygen 52 is delayed until the coal 53 has penetrated into the slag layer. 
As a result, the volatile matter 55 separates from the coal at some point 
in the slag layer 30 and begins to rise. It is intercepted by the oxygen 
stream 52 and is combusted before reaching the surface of the slag layer 
30. The resulting energy, as heat of combustion 54 of the volatile matter, 
is available to the reaction or reactions occurring in the slag layer 30, 
or for use in maintaining the temperature of the overall process. 
Referring now to FIGS. 2, 3, and 4, lance 60 is designed to be used to 
deliver the carbonaceous material, oxygen, and inert gas to the slag 
layer. The lance consists of an elongated body with a central core 61, 
which is surrounded by a first annular chamber 62 and a second annular 
chamber 63. The central core 61 is used for the delivery of the 
carbonaceous material and the second annular chamber 63 is used to deliver 
the oxygen. The oxygen stream is delivered at an angle of about 15 to 20 
degrees from the axis of the carbonaceous material stream. The first 
annular chamber 62 is used to deliver the inert gas, which serves to 
separate the carbonaceous material and oxygen during transport through the 
lance. 
The central core 61 is tubular and can be made of steel pipe with an inside 
diameter of about 25 to 30 millimeters, and a wall thickness of about 4 to 
7 millimeters. The central tubular core 61 is made removable, permitting 
the tube to be changed in the event of solids plugging. The width of the 
first annular chamber 62 is about 0.9 to 1.1 millimeters. The second 
annular chamber 63 is about 19 to 25 millimeters in width. The spatial 
arrangements of the chambers can be viewed in FIG. 4, which is a 
cross-sectional view of the elongated body taken along the line 4--4 in 
FIG. 2B. The lance 60 is provided with a water cooling chamber 64 
surrounding the second annular opening 63. 
The lance 60 incorporates inlet means for the carbonaceous material, the 
oxygen, the inert gas, and the water. In the preferred embodiment shown in 
FIG. 2, the coal inlet means 70 is to the central core, the nitrogen inlet 
means 71 is to the first annular chamber, the oxygen inlet means 72 is to 
the second annular chamber, and the water inlet means 73 is to the 
enclosed chamber 64 surrounding the second annular chamber. Water cooling 
chamber 64 is equipped with a water discharge means 74. 
The discharge ends of the tubular central core 61, the first annular 
chamber 62, and the second annular chamber 63 are located in a detachable 
and replaceable nozzle 65. The nozzle is welded to the lance body 60. It 
can be replaced by cutting radially through the lance 60 at or slightly 
above the weld 87 and then welding the new nozzle to the resulting cut end 
of the lance. 
An end view of the nozzle is shown in FIG. 3. In this arrangement, the 
nozzle contains a central opening 66 that corresponds with and 
communicates with the central tubular core 61. A ring-shaped opening 67 
corresponds with and communicates with the first annular chamber 62. The 
discharge of the contents of the second annular chamber 63 is to a series 
of dispenser openings 68 that communicate with the second annular chamber 
63. These dispenser openings 68, numbering about 8, are evenly spaced 
around the second annular chamber 63 and provide a total open area of at 
least about 1000 square millimeters. Preferably, the dispenser openings 68 
are cylindrical bores through the nozzle with sufficient length to provide 
direction to the flow of oxygen from the openings. More preferably, the 
cylindrical bores serving as the dispenser openings 68 are about 32 to 65 
millimeters in length and have an axis that is angled from about 15 to 20 
degrees outwardly from the core's axis. They have diameters of about 15 to 
17 millimeters. 
In FIGS. 5 and 6 is depicted the replaceable tip of a modified version of 
the lance of FIGS. 2-4, designed to permit the simultaneous introduction 
of both hard blow and soft blow oxygen, together with the particulate 
coal. The coal is delivered through central passage 80, for example at a 
velocity of about Mach 0.75 to 2.0. A thin shroud of inert gas, preferably 
nitrogen or argon, is forced out of annular chamber 81, for example at a 
velocity of about Mach 0.5 to 1.5. A hard blow of oxygen, for example 
having a velocity of about Mach 0.75 to about 1.8 or 2.0, is discharged 
from annular chamber 82. Dispenser holes 83 angle the hard blow oxygen 
away from the center axis by about 15 degrees. Soft blow oxygen, for 
example at a velocity of about Mach 0.5 to 1.0, is delivered through 
annular chamber 84. Dispenser openings 85 direct the secondary oxygen 
outwardly from the hard blow oxygen at an angle of about 25 degrees 
(measured from the direction of flow of the hard blow oxygen). Cooling 
water is circulated through U-shaped annular chamber 86, for example at a 
flow rate of about 150 to 180 NM.sup.3 /hr. 
The lance may be poised above the surface of the slag layer a distance of, 
say, about 0.20 to 0.50 meters, measured from the bottom tip. The higher 
velocity oxygen ejected through nozzles 83 primarily serves to penetrate 
into the slag layer, in which it then reacts with volatile matter released 
from the coal. The lower velocity oxygen ejected through nozzles 85 serves 
primarily to react with carbon monoxide gas rising from the slag. 
Generally, more soft blow oxygen is needed than hard blow; e.g., the 
volume ratio of soft to hard will be in the range of about 1/1 to 1.2/1. 
The ratio of the total area of nozzle openings for the hard blow oxygen to 
the total area of nozzle openings for the soft blow oxygen may, for 
example, be within the range of about 1/1 to 0.9/1. 
Other embodiments of the invention will be apparent to those skilled in the 
art from consideration of the specification and practice of the invention 
disclosed herein. It is intended that the specification and examples be 
considered as exemplary only, with the true scope and spirit of the 
invention being indicated by the following claims.