CA1172848A - Gas flow control method and apparatus for metallurgical vessels - Google Patents
Gas flow control method and apparatus for metallurgical vesselsInfo
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- CA1172848A CA1172848A CA000203268A CA203268A CA1172848A CA 1172848 A CA1172848 A CA 1172848A CA 000203268 A CA000203268 A CA 000203268A CA 203268 A CA203268 A CA 203268A CA 1172848 A CA1172848 A CA 1172848A
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Abstract
GAS FLOW CONTROL METHOD AND APPARATUS FOR
METALLURGICAL VESSELS
ABSTRACT OF THE DISCLOSURE
A method and apparatus for controlling the flow of process gases to the tuyeres of a metallurgical vessel provides for simultaneous injection of various gases through multiple tuyere passages. Gas flow controls are provided for controlling the proportions of gases simultaneously injected into the vessel and for controlling gas sequencing and switching operations.
Pressure sensors are provided for monitoring the pressures of the gases delivered through the tuyeres for automatically initiating a switch-over to alternate pressurized gas sources in the event that the currently operating pressurized gas supply fails.
METALLURGICAL VESSELS
ABSTRACT OF THE DISCLOSURE
A method and apparatus for controlling the flow of process gases to the tuyeres of a metallurgical vessel provides for simultaneous injection of various gases through multiple tuyere passages. Gas flow controls are provided for controlling the proportions of gases simultaneously injected into the vessel and for controlling gas sequencing and switching operations.
Pressure sensors are provided for monitoring the pressures of the gases delivered through the tuyeres for automatically initiating a switch-over to alternate pressurized gas sources in the event that the currently operating pressurized gas supply fails.
Description
~) ~, 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.
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.
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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
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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, ., , . , ~
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 .. . ' 'i 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 !1 -6-.,1 ' ' ., , . I
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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.
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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 ;i ' . .
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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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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.
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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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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;
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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 !
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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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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
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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, ., , . , ~
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 .. . ' 'i 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 !1 -6-.,1 ' ' ., , . I
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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.
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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 ;i ' . .
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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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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.
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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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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;
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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 . , '' ~ ' ' "' ' ' .
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¦ 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 !
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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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Claims (28)
1. Apparatus for controlling the flow of fluids to at least one tuyere disposed below the normal level of molten metal in a metallurgical vessel, said tuyere having at least a pair of fluid flow passages, said apparatus comprising:
a source of a reactive gas, a nonreactive gas and a hydrocarbon shielding fluid, first delivery means for selectively delivering said reactive gas to a second of said flow passages, second delivery means for selectively delivering said hydrocarbon shielding fluid to a first of said flow passages, third gas delivery means for selectively delivering said nonreactive gas to said first and second flow passages, first control means coupled to each delivery means for initiating the flow of one of said gases or shielding fluid to said respective tuyere passages and for terminating the same, delay means for maintaining the flow of said gases or hydrocarbon fluid for a predetermined period after the initia-tion of the flow of another gas or shielding fluid and second control means coupled to each of said first and second delivery means for selectively maintaining the rate of flow of one of said fluids as a substantially preselected percentage of the flow rate of the other of said fluids independently of variations in the pressure of said fluids within said delivery means.
a source of a reactive gas, a nonreactive gas and a hydrocarbon shielding fluid, first delivery means for selectively delivering said reactive gas to a second of said flow passages, second delivery means for selectively delivering said hydrocarbon shielding fluid to a first of said flow passages, third gas delivery means for selectively delivering said nonreactive gas to said first and second flow passages, first control means coupled to each delivery means for initiating the flow of one of said gases or shielding fluid to said respective tuyere passages and for terminating the same, delay means for maintaining the flow of said gases or hydrocarbon fluid for a predetermined period after the initia-tion of the flow of another gas or shielding fluid and second control means coupled to each of said first and second delivery means for selectively maintaining the rate of flow of one of said fluids as a substantially preselected percentage of the flow rate of the other of said fluids independently of variations in the pressure of said fluids within said delivery means.
2. The apparatus set forth in claim 1 wherein said control means includes first and second means respectively coupled to said first and second delivery means and each being responsive to the respective flow rates of fluid therein and for providing a signal functionally related to said flow rates, said control means also including third and fourth means respectively coupled to said first and second delivery means and to said first and second means for adjusting the flow rate of said fluids to within preselected limits.
3. The apparatus set forth in claim 2 wherein said control means includes fifth means coupled to each of said first and second means and to at least one of said third and fourth means for adjusting the flow rate in one of said first and second delivery means as a substantially preselected percentage of the flow rate in the other of said delivery means.
4. The apparatus set forth in claim 3 wherein each of said first and second means each comprises flow meters and said third and fourth means each comprise controller means and a metering valve.
5. The apparatus set forth in claim 1 and including third control means coupled to said third delivery means for con-trolling the flow of fluids therein, and pressure responsive means coupled to each of said first and second delivery means and to said first and third control means for monitoring the pressure of fluid in said first and second flow passages and for terminating the flow of fluid in either of said passages when the pressure of the fluid therein falls below a predeter-mined value and for coupling said respective flow passage to said source of nonreactive gas.
6. The apparatus set forth in claim 1 and including a source of a fourth gas, said reactive gas including oxygen, fourth delivery means for selectively delivering said fourth gas to said first and second flow passages, said first control means including means for effecting the flow of said nonreactive gas to either of said flow pas-sages upon the termination of the flow of any of said gases or said hydrocarbon shielding fluid and for a predetermined time prior to the further delivery of any of said gases or hydrocarbon shielding fluid thereto.
7. The apparatus set forth in claim 6 and including valve means disposed in each of said delivery means, switching means having a plurality of positions, said switching means being operative in each of its positions for opening and closing predetermined ones of said valves to provide predetermined ones of said gases and shielding fluid to said flow passages.
8. The apparatus set forth in claim 7 and including second control means coupled to said third delivery means for controlling the flow of fluid therein, and pressure responsive means coupled to each of said first and second delivery means and to said first and second control means for monitoring the pressure of fluid in said first and second flow passages and for terminating the flow of fluid in either of said first or second delivery means when the pressure of the fluid therein falls below a predetermined value and for coupling fourth delivery means to said respective flow passages.
9. The apparatus set forth in claim 8 and including:
a primary source of a nonreactive gas, coupled to said third delivery means for selectively connecting and discon-necting said nonreactive gas source to said tuyere passages, a second source of said nonreactive gas, first pressure responsive means coupled to said primary and second sources of nonreactive gas and being operative to monitor the pressure of said primary source and for coupling said alternate source to said third delivery means when pres-sure of said primary source falls below a predetermined value.
a primary source of a nonreactive gas, coupled to said third delivery means for selectively connecting and discon-necting said nonreactive gas source to said tuyere passages, a second source of said nonreactive gas, first pressure responsive means coupled to said primary and second sources of nonreactive gas and being operative to monitor the pressure of said primary source and for coupling said alternate source to said third delivery means when pres-sure of said primary source falls below a predetermined value.
10. The apparatus set forth in claim 9 wherein said second control means includes first and second flow responsive means respectively coupled to said first and second delivery means and each being responsive to the respective flow rates of fluid therein and for providing a signal functionally related to said flow rate, said control means also including third and fourth means respectively coupled to said first and second delivery means and to said first and second means for adjusting the flow rate of said fluids to within preselected limits.
11. The apparatus set forth in claim 10 wherein said control means includes fifth means coupled to each of said first and second flow responsive means and to at least one of said third and fourth means for adjusting the flow rate in one of said first and second delivery means as a substantially preselected per-centage of the flow rate in the other of said delivery means.
12. The apparatus set forth in claim 11 wherein each of said first and second flow responsive means each comprises flow meters and said third and fourth means each comprise controller means and a metering valve.
13. Apparatus for controlling the flow of fluids to at least one tuyere disposed below the level of molten metal in a metallurgical vessel, said tuyere having a first flow passage disposed in the surrounding relation to a second flow passage, a source of a reactive gas, a nonreactive gas and a hyro-carbon shielding fluid, first delivery means for selectively delivering said reactive gas to said second flow passage, second delivery means for selectively delivering said hydrocarbon shielding fluid to said first flow passage, third delivery means for selectively delivering said non-reactive gas to said first and second flow passages, control means coupled to each delivery means for initiating the flow of one of said gases or shielding fluid to said respective tuyere passages and for terminating the same, and delay means for maintaining the flow of said gases or hydrocarbon fluid for a predetermined period after the initiation of the flow of another gas or shielding fluid.
14. The apparatus set forth in claim 13 and including valve means disposed in each of said delivery means, switching means having a plurality of positions, said switching means being coupled to said delay means and operative in each of its posi-tions for opening and closing predetermined ones of said valves to provide predetermined ones of said gases and shielding fluid to said flow passages.
15. The apparatus set forth In claim 13 wherein there are at .
least two submerged tuyeres in said metallurgical vessel, said tuyeres each having a first flow passage disposed in surrounding relation to a second flow passage, said first delivery means for directing said oxidizing gas to the second flow passage of each tuyere, said second delivery means each being coupled to the first flow passages of different ones of said tuyeres and to said shielding fluid source for directing said shielding fluid to the said second passages in each tuyere, control means coupled to each of said second and further delivery means for selectively controlling the rate of flow of said shielding fluid to each tuyere, said control means being constructed and arranged to main-tain the flow rates of the shielding fluid to each tuyere sub-stantially equal regardless of variations in flow resistance in said flow passages.
least two submerged tuyeres in said metallurgical vessel, said tuyeres each having a first flow passage disposed in surrounding relation to a second flow passage, said first delivery means for directing said oxidizing gas to the second flow passage of each tuyere, said second delivery means each being coupled to the first flow passages of different ones of said tuyeres and to said shielding fluid source for directing said shielding fluid to the said second passages in each tuyere, control means coupled to each of said second and further delivery means for selectively controlling the rate of flow of said shielding fluid to each tuyere, said control means being constructed and arranged to main-tain the flow rates of the shielding fluid to each tuyere sub-stantially equal regardless of variations in flow resistance in said flow passages.
16. The apparatus set forth in claim 15 wherein said control means also includes means coupled to each of said first and third delivery means for selectively controlling the flow rate of one of said oxidizing gas and hydrocarbon shielding fluid in relation to the flow rate of the other.
17. The method of controlling the flow of pressurized fluid to at least one tuyere in a metallurgical vessel, said tuyere having its discharge end disposed below the level of molten metal and having a first flow passage disposed in surrounding relation to a second flow passage, the steps of:
maintaining a bath of metal in said vessel, delivering the first pressurized fluid to a first one of said flow passages, simultaneously delivering a second pressurized fluid to a second one of said flow passages, delivering a third pressurized fluid to one of said flow passages after the first or second pressurized fluid has flowed therein for a predetermined time, continuing the simultaneous flow of said third pressurized gas and one of said first and second pressurized gases in said one flow passage for a second predetermined time and then dis-continuing the flow of said first or second predetermined gas.
maintaining a bath of metal in said vessel, delivering the first pressurized fluid to a first one of said flow passages, simultaneously delivering a second pressurized fluid to a second one of said flow passages, delivering a third pressurized fluid to one of said flow passages after the first or second pressurized fluid has flowed therein for a predetermined time, continuing the simultaneous flow of said third pressurized gas and one of said first and second pressurized gases in said one flow passage for a second predetermined time and then dis-continuing the flow of said first or second predetermined gas.
18. The method set forth in claim 17 including the steps of:
delivering an oxidizing gas to each of said second flow passage, simultaneously delivering a hydrocarbon shielding fluid to each of said second flow passages through individual flow paths, monitoring the flow rates of the hydrocarbon shielding fluid in each of said flow paths, controlling the flow rate of said hydrocarbon shielding fluid in each flow path, and continuously adjusting said monitored hydrocarbon shielding fluid in each path to maintain the flow rates in each substan-tially equal regardless of flow restrictions in said flow pas-sages.
delivering an oxidizing gas to each of said second flow passage, simultaneously delivering a hydrocarbon shielding fluid to each of said second flow passages through individual flow paths, monitoring the flow rates of the hydrocarbon shielding fluid in each of said flow paths, controlling the flow rate of said hydrocarbon shielding fluid in each flow path, and continuously adjusting said monitored hydrocarbon shielding fluid in each path to maintain the flow rates in each substan-tially equal regardless of flow restrictions in said flow pas-sages.
19. The method set forth in claim 18 and including the step of controlling the flow rate of at least one of said oxidizing gas and hydrocarbon shielding fluid as a substantially constant percentage of the other and continuously adjusting said moni-tored hydrocarbon shielding fluid or oxidizing gas so as to maintain said substantially constant ratio.
20. The method set forth in claim 17 and including the steps of:
delivering a third pressurized fluid to at least one of said flow passages after the first or second pressurized fluid has flowed therein for a predetermined time, delivering a nonreactive gas to at least one flow passage prior to the commencement of said third pressurized fluid.
delivering a third pressurized fluid to at least one of said flow passages after the first or second pressurized fluid has flowed therein for a predetermined time, delivering a nonreactive gas to at least one flow passage prior to the commencement of said third pressurized fluid.
21. The method set forth in claim 20 wherein said first pressurized fluid is oxygen, said second pressurized fluid is a hydrocarbon shielding fluid and said nonreactive gas is taken from a group consisting of nitrogen and argon.
22. The method set forth in claim 21 and including the step of:
continuing the simultaneous flow of said nonreactive gas and one of said first and second pressurized oxygen and hydrocargon shielding fluid in said one flow passage for a predetermined time and then discontinuing the flow of the said one of said oxygen and hydrocarbon shielding fluid while con-tinuing the flow of said nonreactive gas.
continuing the simultaneous flow of said nonreactive gas and one of said first and second pressurized oxygen and hydrocargon shielding fluid in said one flow passage for a predetermined time and then discontinuing the flow of the said one of said oxygen and hydrocarbon shielding fluid while con-tinuing the flow of said nonreactive gas.
23. The method set forth in claim 22 and including the step of continuing the simultaneous flow of said nonreactive gas and said third gas for a second predetermined time and terminating the flow of said reactive gas while continuing the flow of said third gas.
24. The method set forth in claim 23 and including the step of:
monitoring the pressure in said first and second flow passages for determining when the pressure thereof falls below predetermined value, maintaining a source of a nonreactive gas, delivering said nonreactive gas to at least one of the flow passages in which the pressure falls below a predetermined value.
monitoring the pressure in said first and second flow passages for determining when the pressure thereof falls below predetermined value, maintaining a source of a nonreactive gas, delivering said nonreactive gas to at least one of the flow passages in which the pressure falls below a predetermined value.
25. The method set forth in claim 24 and including the step of:
monitoring the pressure of the nonreactive gas, maintaining a standby source of said nonreactive gas, coupling said standby source of nonreactive gas to the said one flow passage when the monitored pressure falls below a predetermined value.
monitoring the pressure of the nonreactive gas, maintaining a standby source of said nonreactive gas, coupling said standby source of nonreactive gas to the said one flow passage when the monitored pressure falls below a predetermined value.
26. The method set forth in claim 17 including the steps of:
delivering an oxidizing gas to said second flow passage, simultaneously delivering a hydrocarbon shielding fluid to said first flow passage, selectively terminating the flow of at least one of said oxygen and hydrocarbon shielding fluid to one of said respective flow passages, maintaining a first source of a nonreactive gas, delivering said nonreactive gas to the flow passage in which the flow of one of said oxygen or hydrocarbon shielding fluid has been terminated, monitoring the pressure of said source of nonreactive gas, maintaining a standby source of said nonreactive gas, coupling said standby source of nonreactive gas to said one flow passage when the monitored pressure falls below a predetermined value.
delivering an oxidizing gas to said second flow passage, simultaneously delivering a hydrocarbon shielding fluid to said first flow passage, selectively terminating the flow of at least one of said oxygen and hydrocarbon shielding fluid to one of said respective flow passages, maintaining a first source of a nonreactive gas, delivering said nonreactive gas to the flow passage in which the flow of one of said oxygen or hydrocarbon shielding fluid has been terminated, monitoring the pressure of said source of nonreactive gas, maintaining a standby source of said nonreactive gas, coupling said standby source of nonreactive gas to said one flow passage when the monitored pressure falls below a predetermined value.
27. The method set forth in claim 26 and including the stpes of:
monitoring the flow rates of each of said oxidizing gas and hydrocarbon shielding fluid, controlling the flow rate of at least one of said hydro-carbon shielding fluid and oxidizing gas as a substantially volumetric percentage of the other and continuously adjusting said monitored hydrocarbon shielding fluid or oxidizing gas so as to maintain said substantially constant percentage.
monitoring the flow rates of each of said oxidizing gas and hydrocarbon shielding fluid, controlling the flow rate of at least one of said hydro-carbon shielding fluid and oxidizing gas as a substantially volumetric percentage of the other and continuously adjusting said monitored hydrocarbon shielding fluid or oxidizing gas so as to maintain said substantially constant percentage.
28. The method set forth in claim 17 and including the steps of:
monitoring the pressure in said first and second flow passages for determining when the pressure thereof falls below predetermined value, maintaining a source of a nonreactive gas, delivering said nonreactive gas to at least the one of the flow passages in which the pressure falls below a predetermined value.
monitoring the pressure in said first and second flow passages for determining when the pressure thereof falls below predetermined value, maintaining a source of a nonreactive gas, delivering said nonreactive gas to at least the one of the flow passages in which the pressure falls below a predetermined value.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US37336673A | 1973-06-25 | 1973-06-25 | |
| US373,366 | 1973-06-25 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1172848A true CA1172848A (en) | 1984-08-21 |
Family
ID=23472115
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000203268A Expired CA1172848A (en) | 1973-06-25 | 1974-06-24 | Gas flow control method and apparatus for metallurgical vessels |
Country Status (3)
| Country | Link |
|---|---|
| BR (1) | BR7405262D0 (en) |
| CA (1) | CA1172848A (en) |
| HU (1) | HU167945B (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110387454A (en) * | 2018-04-20 | 2019-10-29 | 沈阳人和机械制造有限公司 | The control system and method for steel ladle bottom argon blowing |
-
1974
- 1974-06-24 CA CA000203268A patent/CA1172848A/en not_active Expired
- 1974-06-24 HU HUPE000922 patent/HU167945B/hu unknown
- 1974-06-25 BR BR526274A patent/BR7405262D0/en unknown
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110387454A (en) * | 2018-04-20 | 2019-10-29 | 沈阳人和机械制造有限公司 | The control system and method for steel ladle bottom argon blowing |
Also Published As
| Publication number | Publication date |
|---|---|
| BR7405262D0 (en) | 1975-10-07 |
| HU167945B (en) | 1976-01-28 |
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