US3865579A

US3865579A - Method and apparatus for the production of steel

Info

Publication number: US3865579A
Authority: US
Inventors: Olin E Williams
Original assignee: Koppers Co Inc
Current assignee: Raymond Kaiser Engineers Inc
Priority date: 1970-01-05
Filing date: 1972-05-01
Publication date: 1975-02-11
Anticipated expiration: 1992-02-11

Abstract

In an integrated steelmaking process the molten pig iron is withdrawn from a blast furnace and conveyed by gravity to a trough like furnace having a plurality of refining zones separated from each other by one or more inverted weirs. In the first refining zone molten iron is prerefined by reaction with high purity oxygen introduced into the iron as it flows by gravity over an inclined base portion of the furnace. In one embodiment the oxygen is introduced into the flowing molten iron from overhead lances in such a manner that the high velocity jets of oxygen oppose the flow of molten iron in the first refining zone and regulate the residence time of the molten iron in the first refining zone. In another embodiment oxygen is introduced into the first refining zone through the furnace inclined base portion in a direction against or opposite to the direction of flow of the molten iron to also regulate the residence time of the molten iron in the first refining zone. Prerefined, deslagged iron flows from the first refining zone to a second zone where additives such as basic slag formers, scrap, mill scale and the like are added. In the second refining zone the refining of the prerefined molten iron is completed by reaction with high purity oxygen passing into the iron to form steel of a desired composition. In one embodiment the steel thus formed in the second refining zone passes therefrom to a ladle for feeding molten steel to a continuous casting machine located in line with the trough like furnace. In another embodiment the steel is introduced into a third refining zone where the composition of the steel is further adjusted by reaction with high purity oxygen introduced into the molten steel and where desired other additives are introduced in pulverulent form. The refining zones have an elongated configuration to provide an enlarged interface between the molten metal and the layer of slag floating thereon to increase the contact time between the molten metal and the slag and increase the removal of phosphorus from the molten metal. The oxygen introduced into the molten iron in the refining zones both controls the flow and regulates the residence time of the molten iron in the respective refining zones and also regulates the slagging of the impurities in the molten iron. In one embodiment carbonaceous liquids are introduced into the furnace around the streams of oxygen to reduce refractory erosion.

Description

Williams METHOD AND APPARATUS FOR THE PRODUCTION OF STEEL [75] Inventor: Olin E. Williams, Pittsburgh, Pa. [73] Assignee: Koppers Company, Inc., Pittsburgh,

[22] Filed: May 1, 1972 [21] Appl. No.: 249,318

Related U.S. Application Data [63] Continuation'in-part of Ser. No. 00,679, Jan. 5,

1970, abandoned.

[52] U.S. Cl. 75/60, 75/46 [51] Int. Cl. C2lc 5/30 [58] Field of Search 75/60, 43, 46, 4O

[56] References Cited UNITED STATES PATENTS 2,915,380 12/1959 Hilty 75/60 3,275,432 9/1966 Alexandrousky 75/60 3,326,671 6/1967 Worner 75/40 3,326,672 6/1967 Worner 75/46 3,396,011 8/1968 Trentini 75/60 3,527,598 9/1970 Rouanet 75/46 3,556,775 1/1971 Kuratomi.... 75/60 3,556,775 1/1971 Kuratomi.... 75/46 3,617,257 11/1971 Rouanet 75/60 3,701,519 10/1972 Vayssiere.... 75/46 3,706,549 12/1972 Knuppel 75/60 Primary ExaminerC. Lovell Assistant Examiner-Peter D. Rosenberg Attorney, Agent, or Firm-Stanley J. Price, .lr.; Sherman H. Barber [57] ABSTRACT [4 1 Feb. 11,1975

introduced into the iron as it flows by gravity over an inclined base portion of the furnace. In one embodiment the oxygen is introduced into the flowing molten iron from overhead lances in such a manner that the high velocity jets of oxygen oppose the flow of molten iron in the first refining zone and regulate the residence time of the molten iron in the first refining zone. In another embodiment oxygen is introduced into the first refining zone through the furnace inclined base portion in a direction against or opposite to the direction of flow of the molten iron to also regulate the residence time of the molten iron in the first refining zone. Prerefined, deslagged iron flows from the first refining zone to a second zone where additives such as basic slag formers, scrap, mill scale and the like are added. In the second refining zone the refining of the prerefined molten iron is completed by reaction with high purity oxygen passing into the iron to form steel of a desired composition. In one embodiment the steel thus formed in the second refining zone passes therefrom to a ladle for feeding molten steel to a continuous casting machine located in line with the trough like furnace. ln another embodiment the steel is introduced into a third refining zone where the composition of the steel is further adjusted by reaction with high purity oxygen introduced into the molten steel and where desired other additives are introduced in pulverulent form. The refining zones have an elongated configuration to provide an enlarged interface between the molten metal and the layer of slag floating thereon to increase the contact time between the molten metal and the slag and increase the removal of phosphorus from the molten metal. The oxygen introduced into the molten iron in the refining zones both controls the flow and regulates the residence time of the molten iron in the respective refining zones and also regulates the slagging of the impurities in the molten iron. In one embodiment carbonaceous liquids are introduced into the furnace around the streams of oxygen to reduce refractory erosion.

11 Claims, 6 Drawing Figures mmnzuI-W .T 3,865,579

SHEET 10F 2 I4 50 r 1L 22 y 32 5:5 so Y /28 TOP GAS j? Z MELT IRON CHARGE SLAG OFF HOT METAL 88 OFF GAS r 9o PREREFINE BLOW OXYGEN 90 HOT METAL TREAT WITH oxYeEr uME, SPAR DECANT FnzsT SLAG 6A5 PREHEAT SCRAP REF-\NE METAL DECANT FINAL SLAG ADD FINAL AomTwEs ADJUST coMPosTTmH CONTlN UOUS CASTHJG METHOD AND APPARATUS FOR THE PRODUCTION OF STEEL CROSS-REFERENCE TO RELATED APPLICATION This application is a continuation-in-part of copending application, Ser. No., 00,679, entitled Method And Apparatus For The Continuous Production of Steel, filed Jan. 5, 1970, and now abandoned.

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a method and apparatus for the production of steel and more particularly to a method and apparatus for the continuous production of steel in a furnace having a plurality of refining zones.

2. Description of the Prior Art In the past several processes have been suggested for the continuous production of steel. For example, Australian Pat. No. 257,168, entitled Continuous Oxygen Steelmaking, discloses a process for making steel in which molten iron is introduced into a trough like furnace and high purity oxygen is impinged on the upper surface of the molten iron to convert the iron to steel. Various additives are also introduced into the refining zones.

Other processes for the continuous production of steel are disclosed in U.S. Pat. Nos. 2,962,277, 3,396,011, 3,275,432, 3,313,618 and 3,565,605. In U.S. Pat. No. 3,396,011, entitled Process And Apparatus For The Continuous Refining Of Ferrous Metal And Particularly Pig Iron, oxygen is introduced into the furnace through porous refractory elements that form a portion of the vessel base or floor. Pulverulent materials required for the refining process, such as lime, prereduced ore and the like, are introduced in a non-oxidizing gas carrier through downwardly extending lances. U.S. Pat. No. 3,330,645 discloses apparatus for introducing oxygen through the furnace base portion and reducing erosion of the refractory material by introducing a protective fluid as an annular stream around the stream of the high purity oxygen. U.S. Pat. Nos. 3,326,671 and 3,364,065 disclose processes for introducing high velocity oxygen into a furnace through lances extending downwardly through the roof portion of the furnace. The lances are arranged to impinge the high velocity stream of oxygen on the slag layer floating on the molten metal and move the layer of slag on the surface of the molten metal bath.

In the above disclosed processes the furnace base portions are level and the flow of the molten metal within the furnace is dependent solely on the rate at which the molten iron is introduced into the furnace and the rate at which the refined steel is withdrawn therefrom. The oxygen introduced in the above described processes, other than U.S. Pat. Nos. 3,326,671

and 3,364,065, functions solely to refine the molten metal. In the above two patents, as previously stated, the high velocity oxygen moves the slag layer on the upper surface of the molten metal.

In U.S. Pat. No. 3,556,775 there is disclosed apparatus for the production of steel in which the molten iron flows by gravity over a step like inclined base portion. Oxygen is introduced into the molten metal through openings in the vertical portions of the furnace base portion. With this arrangement the step like configuration of the furnace base portion and the manner in which oxygen is introduced into the molten metal cannot regulate the residence time of the molten metal in the refining zone. There is a need for a method and apparatus for producing steel in which oxygen introduced into the furnace in addition to reacting with the molten metal regulates the residence time of the molten metal in the refining zone and the residence time of the molten metal in one or more of the refining zones is not solely dependent upon the volume of molten metal present in the furnace.

SUMMARY OF THE INVENTION The present invention is directed primarily to improvements in the production of steel and includes introducing molten iron into a trough like furnace having a plurality of refining zones separated by one or more inverted weirs. At least one refining zone has an inclined base portion so that the molten metal flows downwardly by gravity over the inclined base portion. The molten metal flowing by gravity in the refining zone is subjected to a high velocity stream of high purity oxygen to refine the molten metal and form a layer of slag on the upper surface. The high velocity streams of high purity oxygen are introduced in such a manner as to oppose the gravity flow of the molten iron and regulate or control the residence time of the molten metal in the refining zone.

In one embodiment the high velocity streams of oxygen are introduced through lances extending downwardly through the roof of the furnace in a direction to oppose the gravity flow of the molten metal. In another embodiment the high velocity streams of oxygen are introduced through the base of the furnace in a direction to oppose the gravity flow of the molten metal. In still another embodiment oxygen is introduced both through lances extending downwardly through the roof of the furnace and through the base of the furnace in directions that oppose the flow of the molten metal.

The slag formed in the first refining zone is withdrawn therefrom and the partially refined molten iron flows from the first refining zone to a second refining zone where steel forming materials, such as steel scrap, lime and the like, are added to the prerefined molten iron. Oxygen is introduced into the second refining zone and reacted with the slag forming materials and the partially refined iron is further refined to steel. The steel may thereafter be withdrawn from the furnace or introduced into a third refining zone where the steel may be further refined to a specific steel composition.

Otherdetails and advantages of the invention will become apparent by reference to the following specification, claims and appended drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view of one embodiment of the invention, illustrating the manner in which high velocity oxygen is introduced into the furnace through lances in a direction opposing the flow of molten metal to regulate the residence time of the molten metal in the refining zone.

FIG. 2 is a flow diagram, illustrating a steelmaking process as shown schematically in FIG. 1.

FIG. 3 is a fragmentary schematic view of the furnace first refining zone, illustrating a plurality of oxygen lances extending through the furnace roof in the first refining zone. The oxygen lances are arranged to both introduce oxygen into the molten iron and also regulate the residence time of the molten metal in the furnace.

FIG/4 is a fragmentary schematic view similar to FIG. 3 in which the oxygen is introduced into the first refining zone through the inclined base portion of the furnace. The high velocity streams of oxygen are introduced into the furnace in a direction opposing the gravity flow of the molten iron to control the residence time of the molten iron in the first refining zone.

FIG. 5 is a fragmentary schematic view similar to FIGS. 3 and 4 in which oxygen is introduced into the molten iron through both lances extending through the furnace roof and through openings in the base of the furnace in a manner to control the residence time of the molten iron in the furnace.

FIG. 6 is a schematic view of the steelmaking process in which the furnace has three refining zones and the steelmaking additives are introduced into the second refining zone and the refined steel is conveyed from the second refining zone to a third refining zone for further refining.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to FIG. 1, iron ore, limestone and coke are continually fed to a blast furnace generally designated by the numeral 10. The blast furnace 10 may be of conventional design wherein raw materials are continuously charged into the top of the furnace and molten blast furnace iron or pig iron is withdrawn from the bottom portion of the furnace through a ceramic runner 12. The molten blast furnace iron may be withdrawn either intermittently or continually through runner 12. The runner 12 is preferably a closed inclined refractory tube through which the molten iron flows by gravity from the blast furnace 10 to a holding furnace 14.

The holding furnace 14 is lined with a suitable refractory material and is employed to hold or store molten iron as it is withdrawn from the blast furnace 10. There may be one or more holding furnaces 14 from which the molten iron is withdrawn for further processing according to my invention or from which the molten iron may be either withdrawn through outlet 16 and diverted to other steelmaking processes. The molten iron flows from holding furnace 14 through a second inclined runner 18 into an elongated trough like furnace generally designated by the numeral 20. Flow of molten iron from the holding furnace 14 through runner I8 is regulated by a suitable valve or other regulating device 22 positioned in runner l8.

Furnace has a generally elongated configuration with a base portion 24, a front wall 26, a rear wall 28 and a roof 30, all lined with a suitable refractory material. The furnace 20 illustrated in FIG. 1 has two refining zones designated by the

numerals

32 and 34 that are separated by an inverted weir 36. The base portion 24 in refining zone 32 has an upper inclined surface 38 for downward gravity flow of the molten iron from the front wall 26 to the second refining zone 34. As illus trated in FIG. 1, the inclined surface 38 includes steps or cascades to render somewhat turbulent the gravity flow of molten iron thereover to thereby expose a greater surface of the molten iron for refining as later described.

At least one lance 40 is provided in the furnace roof 30 and extends angularly therethrough in a direction opposite to the flow of the molten metal along the inclined surface 38. While only one lance is illustrated,

it should be understood that a plurality of lances may be provided as required to both regulate the residence time of the molten iron and provide sufficient oxygen to react with the molten iron. Oxygen, preferably high purity oxygen, i.e., 99.5+% purity, is supplied to lance 40 and ejected therefrom at high velocity downwardly onto the stream of molten iron flowing through the furnace 20. The angular relation of the lance 40 introduces the oxygen in a manner to oppose the flow of the molten metal and thus control the flow and residence time of the molten metal in the furnace. As the oxygen enters the flowing stream of molten iron a preliminary refining of the iron takes place, principally the oxidation of iron to iron oxide, of carbon to carbon monoxide, silicon to silicon oxides and phosphorus to phsophates etc. to form a first slag 42. Slag forming additives such as lime may be introduced into the first refining zone through the lance 40 with the stream of high purity oxygen. The slag 42 floats on the surface of the molten iron and flows concurrently therewith from left to right (as shown) over the inclined surface 38 in furnace 20. Preferably the stream of molten iron flowing through the furnace 20 is relatively shallow to facilitate the reaction of iron and impurities therein with the stream of oxygen flowing from the lance 40. The elongated configuration of the furnace further provides a relatively large interface between the surface of the molten iron and the slag floating thereon to maximize contact time between the slag and molten iron and increase phosphorous removal from the molten iron. lmpingement of the high velocity blast of oxygen on the shallow stream of molten iron breaks up at least a portion of the stream of flowing molten iron into droplets to increase the exposed surface area for reaction and thereby increase the efficiency of the refining reac tions.

The slag 42 formed in the first reaction zone 32 is withdrawn form the furnace through a notch or opening 44 adjacent the inverted weir 36. Opening 44 is provided at a level in furnace 20 substantially equal to the level of the slag flowing on the molten metal surface as it leaves the weir 36. The slag 42 is decanted and withdrawn from furnace 20 through opening 44 and may be removed in a slag car or cars 46 movable away from the furnace on rails 48.

A stream of partially refined, deslagged iron passes through an opening or channel 50 at the base of weir 36 into the second refining zone 34 of furnace 20. In refining zone 34 steel scrap, mill scale and other additives for making up the proper heat balance in the steelmaking process may be added. Likewise, in refining zone 34 slag forming agents, such as lime, limestone, fluorspar and the like, are added for reaction with the iron oxides and other compounds in the slag 42 formed in the refining zone 34.

A plurality of lances 52 which may be similar to the previously described lance 40 extend through the roof 30 of furnace 20 into the refining zone 34. The slag making additives may be injected with the oxygen as it is introduced through the lances 52 and ejected therefrom downwardly at a high velocity onto the molten metal flowing in refining zone 34. The slag formers may alternatively be charged to the furnace 20 through a chute or the like (not shown). One or more of the lances may also have a fuel burning function for providing any additional heat required in the steelmaking process.

The lances 52 are also arranged angularly to the flow of molten metal and the high velocity streams of oxygen flowing from the lances 52 also control or regulate the flow and residence time of the molten metal in refining zone 34. The refining zone 34 also has an elongated configuration to provide a maximum interface between the molten metal and the slag to facilitate the reaction of the phosphorous impurities at the interface between molten metal and the slag floating thereon.

A shaft furnace 54 is provided above the second refining zone 34. Steel scrap or other solids to be charged to the steelmaking process are fed into furnace 54 and injected into the second refining zone 34 of furnace through an opening 56 in the furnace roof 30. A suitable flow regulating device 58 for the solids is provided in the lower portion of shaft furnace 54 for feeding the solids into the furnace at a preselected desired rate. Hot off gases formed in the furnace 20 are employed to preheat the scrap or solids in the shaft furnace 54. An inlet port 60 is provided in the furnace roof and a conduit 62 connects the opening to the lower portion of the shaft furnace 54. A combustion chamber 64 is provided in conduit 62 and air in introduced into the combustion chamber 64 through conduit 66 and is admixed with the off gases which comprise a substantial amount of carbon monoxide. The off gases are burned with air in combustion chamber 64 and thereafter carried through conduit 62 into the shaft furnace 54 for preheating the solids therein.

Slag formed in the second refining zone 34 is withdrawn from the furnace through an outlet 68 which is provided in the rear wall 28 at the outlet end of the furnace 20.

Steel formed in furnace 20 is withdrawn from the fur nace through a discharge opening or orifice 70 in the floor 24 in which a suitable flow control device is positioned. Steel flowing through the orifice 70 flows into a receptacle or ladle 72 where it is held prior to being charged to a continuous casting machine or the like. Ladle 72 may serve as an alloying ladle where alloy materials or other additives, such as ferromanganese, may be added to the steel as formed in the process of this invention. For example, a hopper 74 with a feeder device 76 and conduit 78 is positioned adjacent to the vessel 72 and arranged to make such additions.

The ladle 72 has a bottom opening or orifice 80 therein through which the molten steel may flow. A stop rod 82 may be provided for regulating flow of steel from the ladle 72. Molten steel flows from the ladle 72 into a tundish 84 which may be of conventional construction and therefrom into a mold 86 of a continuous casting machine. A solid steel strand 88 is cast in mold 86 and withdrawn from the mold 86 by power pinch rolls 90. The solid steel strand 88 may be shaped and cut into billets or the like in the usual manner.

FIG. 2 illustrates the several process steps described hereinabove with reference to the apparatus illustrated in FIG. 1.

It should be noted that a vacuum degassing of the finished steel is fully contemplated by the invention. To that end the vessel 72 or alternatively tundish 84 may be entirely enclosed and have a vacuum port formed therein in which a negative pressure may be formed for vacuum degassing steel processed by the method of the invention.

Referring to FIG. 6 another embodiment of the invention is illustrated in which similar parts will be designated by similar numerals increased by one hundred.

The furnace has a first refining zone 132, a second refining zone 134 and a third refining zone 192. In the first refining zone oxygen is introduced through the furnace base or floor 124 in a direction that opposes the gravity flow of molten iron. The oxygen is intro duced through

conduits

194A, 1948, 194C and 194D that are positioned in a porous refractory portion 196 of the furnace base 124. A separate concentric conduit may be provided around the oxygen conduits 194 in lieu of the porous refractory material to supply an annular stream or envelope of protective fluid, such as a hydrocarbonaceous material, i.e. fuel oil or the like. The protective fluid forms an envelope around the stream of oxygen to minimize erosion of the refractory material forming the furnace floor 138 as will be described in greater detail in reference to FIG. 4.

The molten iron is prerefined in the first refining zone 132 in a manner similar to that previously discussed with reference to refining zone 32 in FIG. 1 and then flows to the second refining zone 134. Preheated scrap is charged to the second refining zone I34 and is melted in a second refining zone by the molten partially refined iron prior to passing into the third refining zone 192. Oxygen is introduced into the second refining zone 134 through a conduit 152 that is similar to the previously described conduits 194 positioned in first refining zone 132. Where desired, slag forming agents, such as lime, limestone, fluospar and the like, may be added for reaction with the slag 142 in the second refining zone I34. Preferably, however, the slag forming materials are added in the third refining zone 192 and may be admixed with the oxygen and fed through a conduit 198 extending through the furnace base portion 124. Alternatively, the slag forming materials may be introduced into the third refining zone 192 in a con ventional manner through a chute or the like. In addition, alloy materials or other final additives may be added to the steel in the third refining zone 192 in the same manner. With the arrangement illustrated in FIG. 6 a separate refining zone 134 may be provided for the addition and melting of the preheated scrap and the slag forming additives may be introduced into either the second refining zone 134 or the third refining zone 192 with the alloy materials or final additives.

In the embodiment illustrated in FIG. 3 similar numerals increased by 200 will designate similar parts and although the embodiment illustrates the first refining zone of the furnace, itshould be understood that the same lance arrangement and inclined floor may be utilized in other refining zones of the furnace. The oxygen is introduced into the furnace first refining zone 232 to both react with the molten metal and also regulate and control the flow of the molten metal in the furnace. The furnace 220 preferably has an elongated relatively narrow configuration adjacent the front wall 226 through which the runner 218 extends. A first series of lances 240A extend downwardly through the furnace roof 230 and transversely across the furnace 220. Although in FIG. 3 only one lance 240A is illustrated it should be understood that a series of lances may be positioned along the same transverse axis of the furnace. The lances 240A are preferably arranged at an acute angle to the direction of flow of the molten iron so that the oxygen flowing from the lances 240A will impinge or strike the molten metal in a direction opposite to the flow direction of molten metal. The oxygen from lances 240A will thus both react with the molten metal and also oppose the gravity flow of the molten metal along the inclined surface 238.

-A second series of lances 240B extend downwardly through the roof of furnace 220 downstream from the lances 240A. The lances 240B are arranged at a more acute angle than the lances 240A to the direction of flow of the molten metal so that the oxygen will impinge on the flowing molten metal at a more acute angle than the oxygen flowing from lances 240A. The oxygen flowing from lances 240B oppose the flow of the molten metal to a greater extent than the oxygen from lances 240A.

A third series of lances 240C extend downwardly through the roof of furnace 220 downstream of lances 240B. The lances 240C are at a more acute angle than either lances 240A or 2408 and thus oppose the gravity flow of the molten metal to a greater extent than the streams of oxygen from the other lances. The

lances

240A, 2403 and 240C are connected by suitable conduits 292 to a supply conduit 294. Valves 296, 298 and 300 are arranged to control the flow or velocity or both the flow and velocity of the oxygen through the

respective lances

240A, 240B and 240C. With this arrangement, the lances can be selectively utilized to introduce oxygen at different velocities into the molten metal to provide the desired amount of oxygen for reaction with the molten metal and also by selected velocities of oxygen through the respective lances control the gravity flow of the molten metal.

Where desired, all of the lances can be used simultaneously to refine the molten metal and control the molten metal flow. The embodiment illustrated in FIG. 3 provides an arrangement for introducing oxygen into the molten metal whereby the degree of refining in the first refining zone may be easily controlled by both the volume and velocity of the oxygen introduced through the various lances. By increasing the velocity and using the lances 240C the molten metal is subjected to the oxygen for a longer period of time and a greater degree of refining takes place in the first refining zone 232. The residence time of the molten metal in the first refining zone 232 and the time that the molten metal is being subjected to oxygen may be easily controlled by the plurality of lances illustrated in FIG. 3.

Although separate lances or series of

lances

240A, 2408 and 240C have been described in reference to FIG. 3, it should be understood, as is illustrated in FIGS. 4 and 5, that other means for introducing oxygen into the furnace and obtaining the above described and discussed advantages may be employed.

Referring to FIG. 4 another embodiment of my invention is illustrated and similar numerals increased by three hundred will designate similar parts and, as discussed in reference to FIG. 3, the arrangement illustrated in FIG. 4 may be utilized in refining zones other than the first refining zone.

The first refining zone 332 has a roof 330, a front wall 326 through which the runner 318 extends and supplies molten iron to the furnace 330. The furnace 330 has a base portion 324 with an upper surface or floor 338 that is generally inclined for the gravity flow of the molten metal away from the front wall 326 toward the weir 336. The furnace base portion 324 has a first series of oxygen conduits 394A extending upwardly through the furnace base portion 324' transversely across the furnace 330. Although in FIG. 4 only one conduit 394A is illustrated, it should be understood that a series of conduits may be positioned across the same transverse axis of the furnace. The conduits or lances 394A are arranged at an acute angle to the direction of flow of the molten metal so that oxygen flowing through the conduits 394A will impinge and strike the lower surface of the molten metal in a direction opposite to the direction of molten metal flow. The oxygen from the conduits 394A will thus react with the molten metal and also oppose the gravity flow of the molten metal along the inclined surface 338. Other similar series of

transverse conduits

394B, 394C and 394D extend upwardly through the furnace base portion 324 and transversely across the furnace 330. These

conduits

394B, 394C and 394D are arranged similar to conduits 394A at an acute angle to the direction of flow of the molten metal so that the oxygen flowing from the respective conduits will impinge and strike the molten metal in a direction opposite to the direction of flow and thus both react with the molten metal and also oppose the gravity flow of the molten metal along the inclined surface 338. A conduit arrangement and valve arrangement similar to that illustrated in FIG. 3 may be employed with the conduits 394A-394D to control the volume and velocity of the oxygen flowing through the respective conduits and thus obtain a preselected volume of oxygen to react with the molten metal and an optimum velocity of oxygen through the respective conduits to control both the flow and residence time of the molten metal in refining zone 332.

The conduits 394 are preferably concentrically positioned within a second conduit 396 to form an annular flow passageway around the conduit 394. A protective fluid, preferably a carbonaceous fluid such as fuel oil or the like, is introduced into the annular passageway around the conduit 394 supplying oxygen to the furnace 332. The protective fluid enters adjacent the furnace floor 338 and forms a protective gaseous envelope I around the stream of oxygen to protect the refractory surface 338. Where desired, other arrangements for introducing the protective fluid into the furnace may be employed, such as porous refractory tuyeres in the furnace base portion 324 or a series of concentrically positioned separate conduits for the flow of protective fluid therethrough. Suitable apparatus for introducing the protective fluid around the stream of oxygen to reduce erosion of the refractory floor 338 is illustrated and described in US. Pat. No. 3,330,645. With the arrangement illustrated in FIG. 4, the oxygen introduced through the furnace base portion 324 serves to both react with the molten metal and also to control the flow or residence time of the molten metal in the refining zone. Also, the arrangement in FIG. 4, where desired, provides a relatively quiescent interface between the upper surface of the molten metal and the layer of slag floating thereon to thereby enhance phosphorous removal from the molten metal by the extended surface contact between the molten metal and the slag.

In FIG. 5 another embodiment of the invention is illustrated and similar numerals increased by four hundred designate similar parts. The embodiment includes a series of

transverse lances

440A, 440B, 440C and 440D extending through the furnace roof 430 in a manner similar to the lances previously described in reference to FIG. 3. Extending upwardly through the furnace base portion 424 are a series of

conduits

494A, 4948, 494C and 494D that are arranged in a manner similar to the conduits 394 previously described with reference to FIG. 4. The lances 440 and conduits 494 may be connected through suitable conduits and valve devices to a common source of high purity oxygen and the flow through the various lances and conduits con trolled to provide optimum oxygen for both reaction with the molten metal and for controlling the flow or residence time of the molten metal in the refining zone 432. With the arrangement illustrated in FIG. either or both the lances 440 and/or conduits 494 may be employed primarily to supply oxygen for reaction with the molten metal and either or both the lances 440 and/or the conduits 494 may be employed primarily to control the residence time of the molten metal in the refining zone 432.

According to the provisions of the patent statutes the principle, preferred construction and mode of operation of my invention have been explained and what is now considered to represent its best embodiments have been illustrated and described. However, it should be understood that the invention may also be practiced otherwise than as specifically illustrated and described.

1 claim:

1. A method for the continuous production of steel comprising,

introducing molten metal into a trough-like furnace,

said furnace having an inclined base portion for the gravity flow of molten metal downwardly thereover,

contacting said molten metal flowing by gravity in said furnace with at least one stream of oxygen whereby said molten metal is at least partially refined and a slag is formed on the upper surface of said flowing molten metal,

opposing the gravity flow of said molten metal in said furnace with said stream of oxygen,

withdrawing said slag from said furnace, and

withdrawing said refined molten metal from said furnace.

2. A method for the continuous production of steel as set forth in claim 1 which includes,

feeding said oxygen into said furnace through at least one lance onto the upper surface of said molten metal in a manner to both react with the molten metal and oppose the gravity flow of said molten metal.

3. A method for the continuous production of steel as set forth in claim 1 which includes,

feeding said oxygen through at least one outlet in said furnace base portion onto the bottom surface of said molten metal flowing downwardly thereover in a manner to both react with the molten metal and oppose the gravity flow of said molten metal.

4. A method for the continuous production of steel as set forth in claim 1 which includes,

feeding said oxygen through a plurality of lances extending through the furnace roof at acute angles to the upper surface of said molten metal to both react with the molten metal and to control the gravity flow of said molten metal in said furnace.

5. A method for the continuous production of steel as set forth in claim 1 which includes,

feeding said oxygen through a plurality of conduits extending through said furnace base portion at an acute angle to' said furnace base portion to both react with the molten metal and to control the gravity flow of said molten metal in said furnace.

6. A method for the continuous production of steel as set forth in claim 1 which includes,

feeding said oxygen through a plurality of lances extending through the furnace roof at an acute angle to the flow of molten metal and through a plurality of conduits extending through said furnace base portion at an acute angle to said furnace base portion to both react with the molten metal and to control the gravity flow of said molten metal in said furnace. 7. A method for the continuous production of steel as set forth in claim 3 which includes,

introducing an annular stream of protective fluid around the stream of oxygen introduced into said furnace. 8. A method for the continuous production of steel as set forth in claim 7 in which,

said protective fluid includes a hydrocarbonaceous liquid. 9. A method for the continuous production of steel comprising,

introducing molten iron into a trough like furnace, said furnace having first and second refining zones separated by an inverted weir, said first refining zone having an inclined base portion for the gravity flow of molten iron downwardly thereover, contacting said molten iron flowing by gravity in said first refining zone with a stream of high purity oxygen whereby said molten iron is partially refined and a slag is formed on the upper surface of said flowing molten iron in said first refining zone, opposing the gravity flow of said molten iron in said first refining zone with said stream of high purity oxygen, withdrawing said slag from said furnace in said first refining zone, conveying said partially refined molten iron from said first refining zone to said second refining zone of said furnace, thereafter adding to said partially refined iron in said second reaction zone steel forming materials, introducing a stream of oxygen into said second re fining zone through a plurality of lances, thereafter contacting said partially refined iron hav ing said steel forming materials therein with said stream of oxygen whereby said partially refined iron is completely refined into steel and slag is formed on the upper surface of said steel, withdrawing said slag from said second reaction zone in said furnace, and withdrawing said steel from said furnace. 10. A method for the continuous production of steel as set forth in claim 9 in which,

hot gases formed in said furnace from the refining of said molten iron are withdrawn from said furnace, admixing said hot gases with air for further combustion of said hot gases, and admixing said hot gases after further combustion with said steel scrap for preheating said scrap. 11. A method for the continuous production of steel comprising,

introducing molten iron into a trough like furnace, said furnace having first, second and third refining zones separated from each other by inverted weirs,

said first refining zone having an inclined base portion for the gravity flow of molten iron downwardly thereover,

contacting said molten iron flowing by gravity in said first refining zone with a stream of high purity oxygen whereby said molten iron is partially refined and a slag is formed on the upper surface of said flowing molten iron in said first refining zone,

opposing the gravity flow of said molten iron in said first refining zone with said stream of high purity oxygen,

withdrawing said slag from said furnace in said first refining zone,

conveying said partially refined molten iron from said first refining zone to said second refining zone of said furnace,

withdrawing hot gases from said furnace,

admixing said hot gases with air for further combustion of hot gases,

admixing said hot gases after further combustion with steel scrap for preheating said steel scrap,

introducing said steel scrap into said second refining zone,

melting said scrap in said partially refined molten iron in said second refining zone,

introducing a stream of oxygen into said second refining zone for reaction with said partially refined molten iron and melted scrap,

conveying said partially refined molten iron and said melted scrap to said third refining zone of said furnace,

introducing steel forming additives to said partially refined molten iron and melted scrap in said third refining zone,

introducing steel forming additives to said partially refined molten iron and melted scrap in said third refining zone.

introducing a stream of oxygen into said third refining zone,

contacting said partially refined iron and molten scrap having said steel forming additives therein with a stream of oxygen whereby said partially refined iron and molten scrap is completely refined into steel and slag is formed on the upper surface of said steel,

withdrawing said slag from said third refining zone in said furnace, and

withdrawing said steel from said furnace.

* l l= l=

Claims

1. A METHOD FOR THE CONTINUOUS PRODUCTION OF STEEL COMPRISING, INTRODUCING MOLTEN METAL INTO A TROUGH-LIKE FURNACE, SAID FURNACE HAVING AN INCLINED BASE PORTION FOR THE GRAVITY FLOW OF MOLTEN METAL DOWNWARDLY THEREOVER, CONTACTING SAID MOLTEN METAL FLOWING BY GRAVITY IN SAID FURNACE WITH AT LEAST ONE STREAM OF OXYGEN WHEREBY SAID MOLTEN METAL IS AT LEAST PARTIALLY REFINED AND A SLAG IS FORMED ON THE UPPER SURFACE OF SAID FLOWING MOLTEN METAL, OPPOSING THE GRAVITY FLOW OF SAID MOLTEN METAL IN SAID FURNACE WITH SAID STREAM OF OXYGEN,

2. A method for the continuous production of steel as set forth in claim 1 which includes, feeding said oxygen into said furnace through at least one lance onto the upper surface of said molten metal in a manner to both react with the molten metal and oppose the gravity flow of said molten metal.

3. A method for the continuous production of steel as set forth in claim 1 which includes, feeding said oxygen through at least one outlet in said furnace base portion onto the bottom surface of said molten metal flowing downwardly thereover in a manner to both react with the molten metal and oppose the gravity flow of said molten metal.

4. A method for the continuous production of steel as set forth in claim 1 which includes, feeding said oxygen through a plurality of lances extending through the furnace roof at acute angles to the upper surface of said molten metal to both react with the molten metal and to control the gravity flow of said molten metal in said furnace.

5. A method for the continuous production of steel as set forth in claim 1 which includes, feeding said oxygen through a plurality of conduits extending through said furnace base portion at an acute angle to said furnace base portion to both react with the molten metal and to control the gravity flow of said molten metal in said furnace.

6. A method for the continuous production of steel as set forth in claim 1 which includes, feeding said oxygen through a plurality of lances extending through the furnace roof at an acute angle to the flow of molten metal and through a plurality of conduits extending through said furnace base portion at an acute angle to said furnace base portion to both react with the molten metal and to control the gravity flow of said molten metal in said furnace.

7. A method for the continuous production of steel as set forth in claim 3 which includes, introducing an annular stream of protective fluid around the stream of oxygen introduced into said furnace.

8. A method for the continuous production of steel as set forth in claim 7 in which, said protective fluid includes a hydrocarbonaceous liquid.

9. A method for the continuous production of steel comprising, introducing molten iron into a trough like furnace, said furnace having first and second refining zones separated by an inverted weir, said first refining zone having an inclined base portion for the gravity flow of molten iron downwardly thereover, contacting said molten iron flowing by gravity in said first refining zone with a stream of high purity oxygen whereby said molten iron is partially refined and a slag is formed on the upper surface of said flowing molten iron in said first refining zone, opposing the gravity flow of said molten iron in said first refining zone with said stream of high purity oxygen, withdrawing said slag from said furnace in said first refining zone, conveying said partially refined molten iron from said first refining zone to said second refining zone of said furnace, thereafter adding to saId partially refined iron in said second reaction zone steel forming materials, introducing a stream of oxygen into said second refining zone through a plurality of lances, thereafter contacting said partially refined iron having said steel forming materials therein with said stream of oxygen whereby said partially refined iron is completely refined into steel and slag is formed on the upper surface of said steel, withdrawing said slag from said second reaction zone in said furnace, and withdrawing said steel from said furnace.

10. A method for the continuous production of steel as set forth in claim 9 in which, hot gases formed in said furnace from the refining of said molten iron are withdrawn from said furnace, admixing said hot gases with air for further combustion of said hot gases, and admixing said hot gases after further combustion with said steel scrap for preheating said scrap.

11. A method for the continuous production of steel comprising, introducing molten iron into a trough like furnace, said furnace having first, second and third refining zones separated from each other by inverted weirs, said first refining zone having an inclined base portion for the gravity flow of molten iron downwardly thereover, contacting said molten iron flowing by gravity in said first refining zone with a stream of high purity oxygen whereby said molten iron is partially refined and a slag is formed on the upper surface of said flowing molten iron in said first refining zone, opposing the gravity flow of said molten iron in said first refining zone with said stream of high purity oxygen, withdrawing said slag from said furnace in said first refining zone, conveying said partially refined molten iron from said first refining zone to said second refining zone of said furnace, withdrawing hot gases from said furnace, admixing said hot gases with air for further combustion of hot gases, admixing said hot gases after further combustion with steel scrap for preheating said steel scrap, introducing said steel scrap into said second refining zone, melting said scrap in said partially refined molten iron in said second refining zone, introducing a stream of oxygen into said second refining zone for reaction with said partially refined molten iron and melted scrap, conveying said partially refined molten iron and said melted scrap to said third refining zone of said furnace, introducing steel forming additives to said partially refined molten iron and melted scrap in said third refining zone, introducing steel forming additives to said partially refined molten iron and melted scrap in said third refining zone, introducing a stream of oxygen into said third refining zone, contacting said partially refined iron and molten scrap having said steel forming additives therein with a stream of oxygen whereby said partially refined iron and molten scrap is completely refined into steel and slag is formed on the upper surface of said steel, withdrawing said slag from said third refining zone in said furnace, and withdrawing said steel from said furnace.