Note: Descriptions are shown in the official language in which they were submitted.
~)
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BACKGROUND OF THE INVENTION
This invention relates to pneumatic steel making processes
of the type wherein oxygen is blown beneath the level of
molten metal in a metallurgical vessel.
Converter vessels have been developed for treating
molten metal by the injection of oxygen or other gases directly
into the metal bath by means of tuyeres located in the bottoms
or sides of the vessels. In order to prolong the life of the
vessel's refractory and the tuyeres themselves, each of the
oxygen tuyeres are normally surrounded by a second tuyere for
injecting a shielding fluid such as propane, manufactured gas,
natural gas, hydrocarbon gases or light oils. Depending upon
the composition of the shielding fluid, the volumetric percentage
of the shielding fluid to oxygen is normally about 2-10%. As
an example, for an oxygen volume of about 200,000 standard
~ :~7~8~
cubic feet per hour, a propane shielding gas volume of about
6,000 standard cubic feet per hour is preferred, One problem
in such gas delivery systems is to insure that the requisi~e
proportions of oxygen and shielding fluids is maintained.
The use of a hydrocarbon fluid and oxygen in a parallel
gas system also creates serious safety problems in this type of
metallurgical system. Another problem is to insure sufficient
gas pressure at all time to the tuyeres in order to insure that
molten metal does not flow into the tuyeres and gas system.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a method and
apparatus for controlling the delivery of pressurized fluids -to
tuyeres of a metallurgical vessel.
It is a further object of the invention to provide a fluid
15 supply method and apparatus for submerged tuyeres of a metallurgi-
cal vessel which prevents the release of potentially dangero~s
gases in the event of a system fail~lre.
It is still another object of the invention -to provide
a method and apparatus for delivexing gases to submerged tuyeres
20 in a metallurgical vessel wherein the proportions of gases
delivered may be controlled.
A further object of the invention is to provide a gas
supply method and apparatus for the submerged tuyeres of
metallurgical vessel which maintains pressure during gas
25 switching operations.
Yet another object of the invention is to provide a gas
supply method and apparatus for the tuyeres of a metallurgical
vessel wherein prior to a gas switching operation, the system
is purged of gases which would create potentially dangerous
30 mixtures.
2~ ~
How the ~oregoing and other more speciic objects are
achieved will appear in the more detailed description of the
new method and apparatus for practic~gthe method which will
be set forth shortly hereinafter in reference to the drawings.
An apparatus is provided for c~ntrolling the flow of
fluids to at least one tuyere disposed below the level of
molten metal in a metallurgical vessel, the tuyere having
a first flow passage disposed in the surrounding relation of
a second flow passage; a source of reactive gas, a non-
reactive gas and a hydrocarbon shieldlng fluid; first del-
ivery means being provided for selective~y delivering the
reactive gas to the second flow passage, with second delivery
means for selectively delivering the hydrocarbon shiélding
fluid to the first flow passage: third delivery means is pro-
vided for selectively delivering the non-reactive gas to the
firs-t and second flow passages, control means being coupled
to each delivery means for initiating the flow of one o
the gases or shielding fluid to the respective tu~ere pas-
sages for terminating the same; with delay means provided for
maintaining the flow of the gases or hydrocarbon fluid for
a predetermined period after the initiation of the flow of
another gas or shielding fluid.
In accordance with a further aspect of the present
teachings, a method is pro~ided of controlling the flow of
pressurized fluid to at least one tuyere in a metallurgical
vessel with the tuyere having its discharge disposed below
the level of molten metal and having a first ~low passage
disposed in surrounding relation to a second flow passage.
The method comprises the steps of maintaining a bath of metal
in the vessel, deliveri.ng a first pressurized fluid to a
first one of the ~low passages, simul-taneously delivering a
second pressurized fluid to a second one of the flow passages
& AC ~
delivering a third pressurized fluid to one of the flow pas-
sages after the first or second pressurized fluid as ~lowed
therein for predetermined time, continuing the simultaneous
flow of the third pressurized gas and one of the first and
second pressurized gassed in the one 10w passage or a
second predetermined time and then discontinuing the flow of
the first or second predetermined gas.
In accordance with the invention, a method and apparatus
isp~vided for controlling the delivery of various process
gases to the submerged tuyeres of a metallurgical vessel.
Flow controls are provided for selectively controlling the
proportions of gases which are simultaneously injected through
the submerged tuyeres and for controlling the sequencing
thereof. Pressure sensors may be provided for detecting
malfunctions in the gas supply to the tuyeres and for ini-
tiating an automatic switch-over to alternative gas sources.
BRIEF DESCRIPTION OF THE DRAWINGS
. .
FIGURE 1 schematically illustrates a furnace with which
the invention may be employed;
FIGURE 2 i~ a schematic diagram of the gas flow piping
and controls according to the invention;
FIGURE 3 schematically illustrates the electrical cir-
cuitry according with the invention; and
FIGIJRE 4, appearing on the page containing Fig~ 1,
schematically illustrates an alternate gas flow piping and
control arrangement.
DESCRIPTION OF A PREFERRED EMBODIMENT
FIGURE 1 schematically illustrates a metallurgical
vessel 10 with which the gas distribution system according
to the invention may be employed. In the illustrated ex-
ample, vessel 10 comprises an open-h~arth furnace, although
it will be appreciated t~at the invention has application
- 3a -
~ 7 ~ . a ~
¦ ~ other type~ of pneum~tic metallurgical ~eesel~ as well.
¦ Ve~sel 10 includes a réfractory shell ll surrounded by a sup-
! po~ing framework generally designated by the reference numeral 12.
The refractory lining 11 defines a vessel having a shallow hearth 14 for
i containir}g a bath of molten metal 15. A plurality of charging openings
17 may be formed along one side of the vessel 10 and each is provided with
li charging dol~r 18 which may suitably be raised and lowered when desired, ¦
- ! in any manner well known in the art. The furnace 10 may be moun~ed in
Il any suitable manner such as on stationary concrete or steel supports 20,
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A plurality of tuyeres 23 may extend through at least one side o
the furnace 10 with their inner eIlds disposed below the level of the bath
15, Tuyeres 23 may include an inner pipe 23a and a spaced outer pipe 23b.
A irst process gas may be provided to the inner tuyere pipe 23a by a
;, ~' .
' delivery pipe 24a and a second gas or fluid may be provided by a pipe 24b
to the gap between the inner pipe 23a and the outer pipe 23b. A vent
opening 25 and burner 28 may be pro~ided in one or both ends of furnace
, lO. In addition, a pouring spout 29 may be disposed on the side of the
,i ~essel lO opposite the charging doors for removing slag from the molten
I¦ metal 15 and for pouring the molten metal after processing.
;' Vessel 10 will typically be charged with scrap, hot metal or a
com~ination of the two which may then be melted or preheated as required
by the burner 28. In addi~ion, the tuyeres 23 may be employed in the pre- !
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heating operation in which event a fuel, such as propane, light oil or
natural gas is blown through the outer tuyere 23b while air or oxygen is
simultaneously blown through inner tuyere 23a to support combustion of
'¦ ` the fuel within the vessel lO for preheating the charge. Further processing
of the molten metal wîthin vessel lO is accomplished lby injection of various
combinations of gases in which additive materials may be entrained. The
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¦ .~dditive materiais may be entrained in the ga9e9 in powdered form by CoF-
¦ Yentional means and injected through the tuyeres 23. For example, if
¦ desul~urization is required, a hydrocarbon gas, nitrogen or argon may .
¦ be blown through the irmer tuyere 23b while nitrogen or argon and entrained
powdered lime may be blown through the outer tuyere 23a. During the
I¦ main oxygen blow, oxygen, either alone or with entrained lime, n~ay be
1~ blown through the inner tuyere Z3a andthe hydrocarbon shi~lding through
!! the gap between the tuyere pipes 23a and 23b. For phosphorous removal,
1! a similar oxygen.hydroearbon combination may be employed along with
, lime In the event removal of dissolved hydrogen ~s indicated, inert
gases such as nitrogen or argon may ~e blown through both tuyere pipes.
For recarburization, hydrocarbon is provided through the.outer tuyere
while the inner tuyere receives an inert gas such as aI;gon or nitrogen,
During tapping, charging or deslaggingJ preferably inert gases such as
nitrogen or.argon may be blown through both tuyeres but oxygen may be
il blo~vn through the inner tuyere in which case, a hydrocarbon must then
.I be delivered through the outer tUyere- During prolonged wa~ting periods, I
li it may be desirable to maintain ~essel temperature by delivering air
jl through the inner tuyeres a.nd nitrogen or ar~on through the outer tuyeres
., while during sht~rt waiting periods either air or nitrogen or combinations
of the two may be delivered to ~,oth tuyeres.
The supply system for supplying oxygen and hydrocarbon shielding i
- I fluid argon or nitrogen or air to the system at the requisite times and in
the appropriate amounts is illustrated in FIGUR:E 2. The system 29 is
shown to be coupled to a pair of tuyeres 2~ although it will be appreciated
.¦ by those skilled in the art that the number of tuyeres depends upon the
. . vessel and the various process rcquirements.
. In general, the gas .,upply system according to the invention in-
.1 . .
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cludeg a first flow control a9sembly 41 ~or gelectively connecting and dis- ¦
connecting an oxygen source 36 to a manifold or distributor 30 and for
controlllng the oxygen flow rate. 5imilarly, a second flow control assembly
42 is provided or selectively connecting and disconnecting a hydrocarbon
8hielding fluid source 37 to a manifold or distributor 34 and for controlling
the flow rate thereof. It will be understood that the shielding fluid may be
any type known in the art such as propane, natural gas, manufactured gas,
- L
i, light oil and the like, In addition> a ratio controller 43 is coupled to éach
of the nOw control assemblies 41 and 42 for maintaining the hydrocarbon
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shielding fluid and oxygen flow rates at a preselected ratio. An alternate
.. gas supply system 44 is operative to couple either a nitrogen source 38
. , . I
. or an air source 40 to one or both of the manifolds 30 and 34 and for
s:ontrolling the flow rates thereto. The ~Llternate gas sources are emplo~ed
when either or both of the oxygen or hydrocarbon shielding fiuid is turned
off either intentionally as process requirements dlctate or as the result
of a failure.
The first flow control assembly 41 includes a pipe 46 which ex-
I . .
tends between the oxygen source 36 and the manifold 30 and has interposed
- l~ therein a shutof~ valve 48 and a flow controller 50 located between the
' 9hutoff valve 48 and the oxygen source 36. Flow controller 50 may include
any suitable means for controlling gas flow rate such as a flow meter Sl
~ interposed in conduit 46 and connected to a flow çontroller 53 for controlling
a nOw control valve 55 disposed in conduit 46.- Flow meter 51 may be in
any well known type of device which is operative to produce an electrical
output signal functionally related to the gas flow rate in conduit 46. The
controller 53 is coupled to flow meter 51 by conductor 52 and is operative
¦ . to provide an output control signal to flow control valve 55 through conduc-
tor 54 which is functionally related to its receiv~d input signal and valve 55
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:~. 172~
is operative to control the flow rate of gas in conduit 46 in
relation to the received control signal.
The hydrocarbon shielding fluid flow control assembly 42
similarly includes a conduit 60 connected between the source 37
and the shielding fluid manifold 34. A shutoff valve 61 and a
flow controller 62 are located in conduit 60 with the shutoff
valve 61 being located between the controller 62 and manifold
34. The flow controller 62 includes a flow meter 63, a controller
65 and a flow control valve 67 which are interconnected to each
other and operative in a manner similar to that discussed with
respect to the control assembly 50 and accordingl~ the assembly
62 will not be discussed in detail. The controllers 53 and 65
are generally preset for a desired flow rate and are coupled
to their respective flow meters 51 and 63 for receiving signals
functionally related to the actual flow rate. The Controllers
53 and 65 are then operative to provide a corrective signal to
their respective flow control valves 55 and 67 to correct for
deviations in the flow rate from the preselected values. A flow
controller which may be employed for this purpose is Model 53EL
3311BElB manufactured by Fisher Porterj Control Corp.
The gas ratio controller 43 is coupled to controller 65
by conductor 68 for receiving a signal functionally related to
the rate of hydrocar~on shielding fluid flow and is operative
to provide an output signal to controller 53 through conductor
70. The output sign~l from ratio controller 43 adjusts the
oxygen flow rate such that it will be a preselected percentage
of the hydrocarbon shielding fluid flow rate. As indicated
hereinabove, for economy consistent with effective results, the
volumetric percentage of the hydrocarbon shielding fluid to
oxygen should be normally about 2-10~ For example, when propane
is used as a shielding fluid, a three percent by volume of
propane to oxygen has been found to be effective.
1~2~
The ratio controller 43 permits the selective adjustment of
the ratio of oxygen to shielding fluid and also permits
modification of this ratio in the event a different hydrocarbon
shielding fluid is employed. The ratio controller 43 may be of
any well known type such as for example Fisher Porter Control
Corporation Model No. M-53ER371lBB.
The alternate gas supply system 44 includes a first
delivery pipe 74a connected to the oxygen pipe 46 downstream
of shutoff valve 48 and a second supply pipe 74b connected to
propane pipe 60 downstream of cutoff valve 61. A flow control
assembly 75a is connected in pipe 74a for controlling the flow
rate of gas therethrough and a bleed valve assembly 76a is
connected in pipe 74a downstream of the controller 75a. The
controller assembly 75a includes a flow meter 80a, a controller
81a and a flow control valve 82a which are interrelated and
operate in a ~anner similar to the componen~s of the controller
assembly 50 and accordingly the details oE control assembly 75a
will not be discussed in detail. The bleed valve assembly 76a
includes a pair of spaced apart shutoff valves 84a and 85a
which are disposed on the opposite sides of a bleed pipe 87a
which is coupled to pipe 74a. In addition, a shutoff valve 88a
is disposed in bleed pipe 87a. Valves 84a, 85a and 88a may be
controlled in any suitable manner such as by solenoids which are
electrically interconnected by conductor 89a such that whenever
25 valves 84a and 85a are closed the valve 88a is open and when
valves 84a and 85a are open, valve 88a is closed. In this
manner, should either of the valves 84a or 85a fail or leak,
the pressurized gas which is intended to be blocked will vent
to the atmosphere rather than passing into one of the other gas
systems. A flow control assembly 75b and a vent valve assembly
76b are similarly ~onnected in supply pipe 74b and each of the
parts has been numbered the same as those portions coupled to
pipe 74a except that the former is distinguished by means of
: ~ 72~18 ~
. ~he letter "b"~ Accordingly, the flow control assembly 75b andthe :
Yent valve assembly 76b will not be discusscd in détail~
The air supply source 40 is coupled to pipe ?4a by pipe 90a and
~h~offvalve 91a and to pipe 74b by pipe 90b and shu~offvalve 91b~ Sim-
ilarly, the rlitrogen source 38 is coupled to pipe 74a by pipe 92a and shut-
off valve 94a and to pipe 74b by pipe 92b and shutoff valve 94b.
Il The standby nitrogen source 39 is coupled to nitrogen supply pipe
¦I! g2 through shutoff valve 98 and conduit 99. A pressure sensor 100 is
connected to nitrogen supply conduit 92 for sensing the pressure therçin
and is electrically coupled to shutoff valve 98 for monitor1ng the pressure
~! in conduit 92. When the pressure of the nitrogen source 38 drops below
. a predetermined level, the pressure sensor 100 will provide a signal
through conductor 101 to ol~en shutoff valve 9B and connect the standby '
nitrogen source to hydrogen supply pipe 92. The various shutoff valves 48,
61, 84a, 85a, 84b, 85b, 88a, ~8b, 91a, glb, 94a, 9~b and ~8 may be con-
I/ . . ' . .
,i trolled in any suitable manner by electxic or pneumatic signals. In thepreferred embodiment illustrated in FIGURE 2, the shutoff valves may be
solenoid controlled and operable to open or close their as80ciated valve
l in response to the receipt OI an energizing signal in the~ rnanner well known
in the art. .
A~ first pair of pressure sensors llOa and 112a are connected to
the oxygen manifold 30 and a second pair of pressure sensors 110b and
i 112b are coupled to the shielding fluid manifold 34. Pressure sensor llOa -
is coupled to shutoff valves 48, 84a 85a 88a and 94a such that when a
predetermined pressure exists in mani~old 30 the ener~izing cir~uits are
: . . !
maintained to normally closed valves 48 and 88a and normally closed valves
84a, 85a and 94a. Normally, when valve 48 is open to provide oxygen to
mani~old 30, pressure sensor 110 will maintain valves 84a, 8Sa and 94a
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closed to block th~ flow of nitrogen and to prevent th0 reveI ~e nOw of
oxygen into the nitrogen system and valve 88a is maintained in an open
condition to bleed any oxygen which may leak past valve 85a. Should the
xygen supply 36 fail so that sensor llOa senses a loss of pressure,
valves 48 and 88a will be closed to interrupt the ox~Ygen flow and val~es
84a, 85a and 94a will be opened to provide nitrogen to the. manifold 30 and
thereby prevent molten metal from flowing back into the tuyere pipe 23a.
Pressure sensor 112a which is also coupled to man;lfold 30 is
operative to corltrol the energization of valves 84a, 85a, 88a, 91a and 94a.
Pre3sure sensor 112a will normally be set at a lower pressure than pressure
' ~ sensor llOa so that in the event of a loss of oxygen pressure, pressure
sensor llOa will be actuated first. However, if there is also a failure of
~itrogen pressure such that the pressure in manifold 30 is not maintained i .
at the preset level of sensor 112a, the latter will operate to maintain
normally open valves 84a and 85a in an open condition, no~mally open
valve 91a will be de-energized to.open and normally closed valve 8~a
.
will be de-energized to remain in a closed condition. Thi.s will supply air
to the manifold 30. In addition, norrnally open valve 94a will be ener-
gized to close and shut off nitrogen nOw- ~
.¦ FIGURE 3 schematically illustrates the energizing circuit 120
for the solenoid control valve.s 48, 61, 84a, 84b, 85a, 85b, 88a, B~b, 9~a,
9Ib, 94a, 94b and 98 for achieving various modes of operation. I~or
., example, these modes may include a first preheat mode wherein hydro-
. carbon shielding fluid is delivered to manifold 34 and combustion air is
- deli~ered to manifold 30; a second preheat mode wherein air is delivered
to both manifolds while the vessel is preheated by burncr 28; a main
oxygen blow mode wherein oxygen is delivered to manifold 30 and hydro-
carbOn shielding fluid is delivered to manifold 34; a desulfurization mode
! -lo~
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7 2 8 ~ ~
wherein shi~lding fluid 19 delivered to manifold 34 and nitrogen is d~livered
to manifold 30; a normal mode for analysis and final adjustmént to bath
chemistry wherein nitrogen is delivered to both manifolds; 'and a proloslged
delayed mode whereln air i deli~ered to manifold 30 and nitrogen to mani-
rold 34.
. . .
As indicated above, valves 4~, 61, 88a and 84b are normally
closed or closed when in a de-energized state and ~ralves B4a, 85a, 84b,
85b, 91a, 91b, 94a, 94b, and 98 are normally open or opened in a ~e-ener-
,, . ., , j,.
gized state. Energizing circuit 120 includes a switching circuit 121 and a
logic circuit 1~2 for coupling appropriate ones of the solenoid ~alves to
an energy source 123 to achieve the desired mode of operationO The logic
circuit 122 includes banks of terminals for each of the operating modes in
addition to a switching mode and an off-mode. Each of the mode terminals~
are identified by a number which corresponds to an appropriate one of the
-!
solenoid valves so that wh, n the terminal bank of a particular mode is
.
energized, each of the indicated solenoid valves will be energized for being
moved to an open or closed position depehding upon'whether or not the
individual valve is normally opened or normally closed.
', The switching circuit 121 ~ncludes a plurality of relays i30, 131a,
' 131b, 132a, 132b, 133a, 133b, 134'a, 134b, 135, 1369 136a and 137, each of
which is connected to one of the terminal banks oî the logic circuit 122.
Switching circuit 121 also includes a timing circuit 1'40 having a selector
switch 141 ~vhich includes terminals labeled 13û-137. The timing circuit
138 is coupled to each of the relays 130-137 such that when the selector
switch is moved from one terminal to another, the appropriate relay will
be energized so that there is no loss of pressure in the tuyeres 23 between I
Switching operations, and no mixing of gases which would cause a poten- !
tially explosive mixture. Toward this end thé timing circuit is operative
. ' . .
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8 ~. ~
to maintain each of the relay.s 130-137 in its energized closed
position for a short period, two or five seconds for example,
after the selector switch 140 has been moved to an alternate
position. This insures that the gas flowing in the tuyeres 23
when a switch is made, will continue after the new gas begins
flowing to insure continuity of gas flow. In addition, timing
circuit 140 is constructed and arranged such that after the
selector switch 141 is moved to a new position, the relay 137
is closed for a predetermined period, twenty seconds, for example,
prior to the closing of the particular relay contact of the new
mode. As a result, nitrogen will flow through all of the tuyere
pipes for a twenty second period to flush any residual gases
prior to the introduction of the gases of the new switched mode.
The timer circuit will also initiate the new mode gas flow for
a predetermined time, five seconds, for example, before the end
of the nitrogen gas purge.
Assume for example that the system is in an off mode
wherein selector 141 is on contact 130 whereby relay 130 is
closed to energize valves 98, 91b, 94b, 9~a, 91a, 81a, 84a, 84b, 85a,
85b, 88a and 88b, so that all of the valves are closed except
the vent valves 88a and 88b. If it is then desired to switch
to the preheat position, selector 141 will move to contact 131
which initially closes contact 131a for a twenty second period
to energize valves 98, 91b and 91a. As a result, valves 48, 61,
91a, 91b and 98 remain closed, valves 84a, 84b, 85a, 85b, 94a and 94b
are open and valves 88a and 88b close. Nitrogen is thereby
delivered to both of the manifolds 30 and 34. After a time
delay, fifteen seconds for example, sufficient to allow any
residual gases to be purged, timing circuit 138 closes to
energize valves 61, 98 and 91b so that hydrocarbon shieldlng
fluid begins flowing to manifold 34 and air begins flowing
through manifold 30 while the nitrogen flow continues. After
a second predetermined time, five seconds, for ex-
- ~2 -
72~
ample, timin,g circuit 140 will clo~e relsy ~31b and open rela~r l37 wher~by
the nitrogen flow will tqrminate while the flow of hydrocarbon 8h~elding
fluid and air will continue. I~ will b~ understood that 8uitable check valves
will prevent the flow of air through nitrogen valves 94a or 94b and ;nto
the hydrocarbon shielding fluid.
, I A~8ume again that the first preheat mode is to be terminated and
'I - the main blow is to be initiated. Se~ector s~vitch 141 is then ~laced on
~j contact 133 which closes rela~ 137 for a twenty ~econd time delay to .
i! inltiate the nitrogen purge an~ then Opens contacts 131a and 131~ after a
two t'o five second delay to terminate the flow of air and shielding fluid.
l! After about a fifteen second delay, relay 133a closes to initiate the flow
l~ of hydrocarbon shielding fluid to manifold 34 and o~ygen to manifold 30
while the nitrogen flow continues for a further ~ive second delay after
which relay 130b closes and relay 137 open,s to terminate the nitrogen flow.
In the event of a power failureJ the various normally closed valves;
~ . . .
will close and the various normaily Open valves will open. This will dis- .
.¦ c~nnect the hydrocarbon shielding flUid source 37 and the oxygen source 36
'¦ from the manifolds 34 and 30 while a~r and nitrogen will be delivered to
,¦ both manifolds to insure no bac~cup Qf molten metal into the gas stream.
,1 It will be understood that during various stage9 of the operationJ
,I materials may be fed through ~he furnace charging doors or entrained as .
a powdered material in an appropriate one of the gas streams,
¦ An alternate embodiment of the invention is schematically.illus-
trated in FIGURE 4. Portions of the apparatus shown in F~GURE 4 which
are the same as those discussed with respect to the em~odiment of
¦ FIGURE 2 bear the same reference numerals with the addition of a prime
~¦ 1' ). For the sake of simplicity, the embodiment of FIGURE 4 shows the
controls and conduits for delivering O~;ygen and the hydrocarbon shlelding
il . , '' ~ ' ' "' ' ' .
.
¦ fluid hlthough it will bc understood that apparatus 9irnl1ar to that shown
j ~ FIGU~E 2 will be provided for delivering nltrQgen and/or air,
IThe flow of oxygen and hydrocarbon shielding fluid in the embodi-
¦ menS of FIGURE 4 from sources 36~ and 37' are respectively rnonltored
1I and controlled by nOw controllers 50' ansl 62' aald an appropriate ratio
of total oxygen flow to hydrocarbon shielding $1uid flow is maintained by
ratio controller 43' as discussed in relation to FIGURE 2~ In addition,
, separate flow controliers i60 and 161 are respectively pro~ded m each of
the conduits 162 and 163 which extend between manifold 34' ~nd each of
the o'uter tuyere pipes 23b'. Flow controllers 160 and 161 may be sub- i
stantially identical to flow controllers 50l, and 62' and accordingly will not !
.
be discussed in detail.
;~AAS those skilled in the art will appreciate, in the operation of
metallurgical vessels having tuyeres for delivering gases beneath the level
of molten rnétal, metallic formations oiten appear at thc inner end of the
$uyeres and which consist of a small porous mound of metal, commonly
l calied mushrooms because of their shape. This build up, restricts gas
i flow and causes an increase in pressure at the delivery point. ~s a result,
if the hydrocarbon shielding fluid is delivered to each of the tuyeres at the
same pressure, the amount of fluid actually delivered wou1d vary between
the variOus tuyeres. This condition, if uncorrected, would cause uneven
tuyere consumption. The fl~ow controliers 160 and 161 are adjusted such
that the flow rate of hydrocarbon shielding fluid to each of the tuyeres 23
will be substantially equal regardless of formation of flow inhibiting for~na-
tion at the discharge end of the tuyeres.
While the invention has been illustrated with regard to a particular
type of rnetallurgical vessel, it wiil be appreciated that the inven~ion has
.lpplication to other types of vessels having tuyeres for delivering gases
~clow the level of molten metal. In addition, while tuyeres having a single
-14- ;~ 1728~
_ ~ o
:; l ; : ~
. outor pipe for deiivery of hydroearbon shielding fluid ha~ be~n shown and
¦ describedJ it will be appreciated that the shielding fluid may be delivered
! through one or more pipes surrounding the. oxygen pipe. In the latter
¦ event~ the ~hielding fluid flow rates may be i~dividually regulated and the
ir 1 other could deliver fluid at a substantially constant rate. Also, while
1~ j par~icular flow modes are described, these are merely illustrative, and
'I ~ny flow mode required by a particular metallurgic,al process may be
'~ employed as well. Accordingly, it is not intended that the invention be
i limited by the foregoing descriptio~ but or~ly by the scope of the appended
. .. claims.
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