Title of Invention	"A PROCESS FOR CONTINUOUS MELTING A CHARGE OF SOLID METALLIC MATERIALS"
Abstract	A continuous process is provided for rapid melting of a variety of virgin and recycled ferrous and non-ferrous metals. This is accomplished by distributing the introduction of the unmelted charge materials and hence the melting heat requirements along an elongate gas-solid-liquid reaction zone within a rotary furnace, according to the distribution of heat available to effect melting. In the case of fine-sized metal charge materials, fluxes and additive reagents, this charge distribution is implemented by traversing of the nozzle jet, as directed to penetrate into the metal and slag bath from a solids injection lance, successively backwards and forwards and, in the case of coarse-sized materials, by traversing of the dischage from an oscillating conveyor.

Title of Invention

"A PROCESS FOR CONTINUOUS MELTING A CHARGE OF SOLID METALLIC MATERIALS"

Abstract

A continuous process is provided for rapid melting of a variety of virgin and recycled ferrous and non-ferrous metals. This is accomplished by distributing the introduction of the unmelted charge materials and hence the melting heat requirements along an elongate gas-solid-liquid reaction zone within a rotary furnace, according to the distribution of heat available to effect melting. In the case of fine-sized metal charge materials, fluxes and additive reagents, this charge distribution is implemented by traversing of the nozzle jet, as directed to penetrate into the metal and slag bath from a solids injection lance, successively backwards and forwards and, in the case of coarse-sized materials, by traversing of the dischage from an oscillating conveyor.

Full Text	The present invention relates to a process for continuous melting a charge of solid metallic materials and a process for the same. The invention relates to melting of metals and, more particularly, to a rotary furnace process and apparatus applicable to continuous melting of predominantly metallic charge materials. Known commercial melting processes have inherent processing difficulties and disadvantages only partly overcome by improvement to design and operating practice. As a ferrous melting example, in electric-arc furnace (EAF) melting of iron and steel scrap, unmelted charge materials are heated to melting temperature with solid surfaces contacting ambient air or hot oxidizing gases, thereby generating oxide particulates and lowering yield. The heat input is focused on a small area within the furnace relative to the total area occupie J by the charge materials. Furthermore, carbon monoxide generated by oxygen injection into the metal bath is only partially burned to carbon dioxide by post-combustion before exit iron the EAF, and only a fraction of the heat so released is transferred back into the charge, Cupola melh, sas like disadvantages, as well as limitation to production of cast iron, ralhei than steel. As a nonferrous example, reverberatory aluminum melting furnaces arc widely applied commet. '"'ly and focus the location of unmelted charge in a small area in relation tc the sources and broad distribution of available heat in the furnace. Elongated rotary melting furnaces employing a partially melted bath into which a solid charge is fed overcome some of the above deficiencies by means of continuous bath stirring and advancing action, in combination with efficient flame.-to-wall, followed by wall-to-charge heat transfer during each furnace rotation. Access for introduction of the metallic charge materials, fluxes and reagents into the process, however, is only via annular furnace end openings, whereas the process mass transfer, heat transfer and process chemical reaction requirements vary and are distributed along the length of the reaction zones. As an example, when cold charge materials are introduced into a partially melted metal bath only adjaceni: to the entry opening, unmelted material may aggregate, creating islands of partially melted material and the like when, at the same time, charge further along the furnace is fully melled and becoming overheated. Unmelted islands of metal exposed to hot-furnace gases are also subject to increased oxidation and loss as oxide particulates. Such problems obviously represent deficiencies in the control of process chemical reactions, mass transfer and heat transfer, and can also be- estriction on the maximum charging and production rat obtainable. It is therefore a principal object of the invention to distribute the melting heal reguirement of unmelted charge materials along the elongated reaction zones according to the distribution of heat available to effect melting, with the corollary object of fast melting of tin; metallic charge materials. Metallic charge materials characteristically carry varying percentages of metal oxide: and other impurities as metal oxides, other metals, other compounds, dissolved gases, other elements such as phosphorous, sulphur and the like. Fluxes and additive reagents arc required as components of the charge materials for reaction with these impurities, along with the metallic charge during processing, tc obtain effective process parameters and desired ane product composition following melting. Perhaps the most common example of an additive reagent is carbon for reduction of metal oxides to increase the yield of metal and/or for alloying the metal to obtain a specific range of dissolved carbon in the melt. It is naturally desirable that the carbon be introduced at the most effective locations to obtain the desired process reactions, such as reaction with metal oxides or oxygen, evolving carbon monoxide (CO) into the furnace gases, and then effecting a high degree of CO post-combustion (PCD). with a good heat transfer efficiency (HTE) into the furnace charge of the heat so liberated prior to the furnace gases exiting the furnace, and for control of the product composition, it s thus another principal object of the invention to distribute the introduction of fluxes and reagents along elongated process reaction zones according to the distribution of process chemical reaction requirements. The invention provides a process and apparatus for continuous metal melting in a horizontally-disposed elongate rotary furnace comprising maintaining a partially melted hath of metal carrying a floating layer of slag in an elongate gas-solid-liquid reaction zone heat.ed by a hot gas stream passing over the metal and slag within the furnace; conveying solid charge materials comprising metallic materials, fluxes and additive reagents through an annular furnace end opening and along the gas-solid-liquid reaction zone and downwardly projecting them into the bath; traversing the position of said downwardly projecting successively backwards and forwards thereby distributing the entry location of charge materials into the bath along a longitudinal traverse span, and allowing liquid metal to (low out of the gas-solid-liquid reaction zone thereby providing for replenishing the hath with fresh solid materials. Said traverse span preferably comprises a major portion of the length of the gas-solid-liquid reaction zone. When applied to granular or pelletized charge materials less than about 3 cm. in size, for example, DRI pellets, granular iron carbide, pulverized coal, lime, crushed and screen limescone and ferroalloy additives, said conveying suitably comprises entraining the charge materials and propelling them by pressurized carrier gases through a solids injection lance cantilevered longitudinally within the hot gas stream in the gas-solid-liquid reaction zone and said downwardly projecting comprises issuing a jet of charge materials and carrier gases downwards from a lance nozzle into the partially melted metal bath whilst stroking the lance successively backwards and forwards distributing the entry location of charge material longitudinally along said traverse span. When applied to larger-sized charge materials, such as recycled scrap metals, pig iron, hot briquetted iron (HBI). lump coal or coke, lump fluxes-and the like, said conveying suitably comprises propelling the charge mau.ials by oscillatio of an oscillating conveyor, also cantilevered along the gas-solid-liquid reaction ?.one. and sa c! downward projecting comprises dropping the charge materials downwards from a discha-ge lip of the conveyor into the bath whilst stroking the conveyor backwards and forwards. Process requirements usually favor charging by a combination of oscillating conveyor and solids injection lance, in which case some overlapping of the lance and conveyor traverst spans is usually desirable, in which case the invention includes controlling the travel eye e time intervals and relative positions of the lance nozzle and conveyor discharge lip to avoid interference during entry between charge materials issuing from the lance nozzle and those dropping from the conveyor discharge lip at any time of passage across the common span oi travel. Further, the rate of charge material flow can also be varied at different positions alorg the traverse span, even including interruptions, in order to realize longitudinal distribution of charge material entry according to desired process parameters. This can be effected either DV varying the velocity of stroking on in the case of lancing, varying the lance inlet feed rate Metals usually carry surface oxides, for example, iron rust. DRI or other pre-reduced virgin materials may also contain substantial content of unreduced residual metal oxides. Metals are also subject to high-temperature oxidation in-process. Also, dissolved carbon is often desired as a product constituent, such as with iron and steel melting. The charge materials therefore typically include carbonaceous materials carrying carbon as an additive reagent ror reduction of the oxides within the metal and slag bath, releasing carbon monoxide (CO) into the hot gas stream, which represents an unburned combustible or fuel. Selectively injecting oxygen into the hot gas stream facilitates the post-combustion of most of this CC within the process elongate reaction zones, and also ecovcry of the heat so released by diicct in-process heat transfer back into the partially meltej bath, with a PCD and HTE higher than that attainable by prior an processes. The process and apparatus of the invention is most suitably applied with the rotary furnace length further elongated to incorporate a gas-liquid reaction zone adjoining the gas-solid-liquid reaction zone into which the liquid metal flows and accumulates for refining reactions and temperature adjustment prior to discharging from the furnace. This zone is heated by a burner from which the products of combustion form, the hot gns stream Ho'-virg on into the gas-sohd-liquid reaction zone countercurrent io the general movcuicnt of rratenals and exhausting through the annular end opening adjacent to the gas-solid-liquid re icuon zone The liquid metal may be discharged by periodical stopping the furnace rotation and opening a tap-hole discharging into a ladle or. alternatively . siphoning the metal continuo asly or semi-continuously via a refractory tube inserted into the metal through the furnace cam ilar end opening entering an adjacent vacuum vessel external to the furnace, from which the metal is withdrawn for casting or further processing Slag may be discharged by overflowing the lip of an annular end opening, including skimming as required or optionally assisted rny endwise furnace tilting through a small angle or. alternatively by a vacuum slag removal system such as described in my U.S. Patent No 5.305,990. The process and apparatus is applicable to melting of various metals, for example, ferrous metals comprising iron and steel scrap, pig iron, DR1 pellets. HB1. and also various virgin or recycled forms of non-ferrous metals such as copper, aluminum, lead, zinc, chromium, nickel, tin and manganese. Mixtures of metals and metal oxides can he processed and it is adaptable to acidic or basic slag and refractory practice. It accommodates a wide range of charge material sizes, ranging from fine granular particles charge by pneumatic injection up to conveyor-sized pieces of recycled scrap metals. It facilitates continuous melting whilst retaining the options of discharging product either continuously, intermittent y or batch-wise It also facilitates high heat transfer rates throughout the process reaction zones and avoids localized overheating or undercooling, as well as provides goud metal-slag interaction towards composition approaching chemical equilibrium 10 realize high product yields and consistent chemtca composition. The invention therefore represents a fast, lear. quiet, thermally efficient and versatile technology for metal melting requirements. Various other objects, features and advantages of the process and apparatus of this invention will become apparent from the following detailed description and claims, and by referring to the accompanying drawings in which: Fig. 1 is a diagrammatic side view, partly in section, illustrating typical features of the process and apparatus of this invention; Fig. 2 is a section view along plan 2-2 of Fig. 1. Fig 3 is a graph showing example traverse cycles for a case in which charge materials are introduced hy a combination of an oscillating conveyor and a solids iniection lance. Fig. 4 presents illustrative diagrams of exemplary general longitudinal distribution of charge material entry and other process inputs for three example cases; Fig. 5 presents diagrams for another two example cases; Fig. 6 is a partial sectional side view illustration of a gas stream oxygen lance injection roz. le adapted to distribute oxygen for post combustion across the gas stream. Fig. 7 illustrates an alternative embodiment of a nozzle as in Fig. 8. Fig. 8 is a diagrammatic side view, partly in section, illustrating additional and alternative features of the process and apparatus of this invention; Fig. 9 is a section view along plane 9-9 of Fig. 8; Fig. 10 is a section view along plane 10-10 of Fig. 9, with the portion of the plane below the central furnace axis seen as rotated approximately 45 degrees when the entrances into submerged channel 65 coincide with the slag layer; and Fig. 11 is a diagrammatic side view, partly in section, illustrating off-gas rcurculation into the ho', gas stream comprising part of the process heat requirements. Referring to Fig. 1, the elongate rotary furnace I with a refractory lining 6 and incorporating restricted annular end openings 4,5 is supported horizontally or with a slight incline within riding rings 2 which are carried by and rotated on rollers 3 in known manner A partially melted metai bath 7 is maintained in a gas-solid-liquid reaction zone 8and also i liquid metal bath 9 in a gas-liquid reaction zone 10 in the embodiment illustrated, with the baths carrying a floating layer of slag 11. The furnace is heated by burner 12 with the products of combustion from burning fuel 13 and oxygen and/or air 14 forming hot gas stream 15 passing countercurrent to the general charge movement exhausting through annular end opening 4 into conditioning chamber 16 entering exhaust duct 42 preceding a gas cleaning system and exhaustion to atmosphere. The process product liquid metal may be dis-hareed by periodic'!!y interrupting the furnace rotation tapning via tap-hole ! 1 miu ladle 18 or the like or. alternatively, siphoning during rotation via refractory siphon tube l(> into 3n adjacent vacuum vessel 20. This vessel optionally may be heated, equipped for uas injection, alloy and flux addition 21 and regulated discharge via a slide-gate 22 according to the ats 8 ladle and vacuum metallurgy Large and irregularly-shaped charge materials such as recycled scrap metals or hriquerted reduced metai oxides are introduced by conveying along oscillating conveyer 2-which is cantilevered through end opening 4 and alone the gas-solid-liquid reaction zone. dropping them downwards from conveyor discharge lip 25 into the partially melted meial bath 7 The feed rate can be controlled by various means, such as a weighblock 58 as illustrated carrying a lifting magnet 57 for ferrous metals, or by other means of charging known quantities at controlled intervals. Various types of weighfeeders apply also to non-magnetic materials for loading conveyor 24, particularly for fluxes and additive reagents A preferred embodiment of conveyor 24 is a horizontally oscillating type in which oscillator drive 26 oscillates conveyor deck 27 back and forth in short strokes relative to base 28 at high frequency and a controlled cycle, according to known practice in the art of conveying. The cantilevered portion of the conveyor deck is double-walled and baffled applying internal forced water cooling. Conveyor 24 also rides on rollers 29 running on tracks 30 which are substantially parallel to the axis of furnace 6. By stroking a hydraulic conveyor traversing cylinder 31 or equivalent, the position of charge material entry 32 is longitudinally distributed along traverse span 33 of gas-solid-liquid reaction zone 8. Finer-sized materials consistently smaller than about 3 cm. are preferably introduced by entraining them in a carrier gas and conveying them pneumatically through a solids injec'ion lance 34 injecting the charge materials downwards from lance nozzle 35 into bath at a sufficient velocity to effect immersion in the metal and slag bath. In the embodiment, illustrated, lance 34 is clamped to a carriage 36 which rides on rollers 37 running on track 31: which is also substantially parallel to the axis of furnace 6 By stroking hydraulic lance traversing drive cylinder 39, the position of charge material entry 40 is longitudinally distribu^d along traverse span 41 of gas-solid-l;quid reaction zone 8 The lance 34 is usually water-cooled, but can also comprise heat resistant materials, as particularly adaptable to low melting-point alloys, such as those of aluminum or lead, or can even include the consumable type, as known in the art of injection lances Frontal support 87 includes a pivot 88 about which the inclination of lance 34 is adjustab!: by cylinder 89 camed on a rear support 90, enabling adjustment of the height of nozzle 33 in relation to the slag and bath, including immersion of the nozzle in the slag, or the slac and bath, as may be preferred for certain process conditions, such as slag foaming practice Supports 87. 90 can each be c irmd on a fixed jib or A-frame, or alternatively, connected on. a common carriage frame, whici may also be equipped to ride on wheels or tracks, adapted to provide longitudinal movener t of the entire assembly into and away from furnace end opening 4. Zone 8 also is preferably heated directly by a burner 44, illustrated in Fig 2 as juxtaposed to solids injection lance 34, which can also be mounted for adjustable longitudir al positioning. Supplementary oxygen for post-combustion may be introduced via burners 44. or also by way of a separate post-combustion lance 45, optionally also adjustably positioned. Since the hot gases within exhaust exit duct 43 are close to atmospheric pressure, dynamic sealing means such as gas-curtains are appropriate for sealing of the conveyor, lance and burner duct openings, as well as interface with end opening 4. In the embodiment illustrated, liquid metal is passed on from the gas-solid-liquid reaction zone 8 by allowing it to flow out through the restricted passage effected by annular refractory dam 23 into the gas-liquid reaction zone 10. The dam 23 also serves to obstruct unmeited pieces of charge materials and the increased flow velocity over the channel restricted by dam 23 also substantially prevents any reverse flow of metal from zone 10 back into zone 8. In processing cases where close temperature control, refining time to obtain chemical equilibrium within bath and slag is not needed and/or processing in a supplcmcn ary ves;el is needed anyway, furnace 6 could be shortened substantially eliminating zone 10 aid intermediate dam 23. maintaining a partially melted bath extending from annular restricted opening 4 to opening 5. discharging metal and slag directly from gas-solid-liquid reaction zone 8. Slag 11 may be removed by skimming or overflow over the iip of restricted opening 5. or even opening 4 in a case where slag flow countercurrent to the metal is beneficial to he process. Lengthwise tilting of fumace 6 through small vertical angles is an optional feitu c which is useful L-r the lip discharge ^f slag. Vacuum shg removal such as 'he removal system described in my U.S patent No. 5,305,990 can also he applied Reference to Fig. 3 together with Fig. I illustrates example traverse cycles in which charge materials are introduced by the combination of an oscillating conveyor and a solid ; injection lance. Conveyor discharge lip 25 is traversed forward at a speed of ! ft./sec until it reaches LCmax. where it reverses and returns to LCmin at 3 ft./scc.. when the cycle is repeated. During the same time interval, lance nozzle 35 traverses forward to LI.max at a speed of 4 ft./sec., reverses and returns to LLmin at 1.33 ft./sec. In this example, the lane : and conveyor travel directionally in unison, but at different speeds over different spans. These spans also overlap, to include a common traverse span for entry of charge material: from both conveyor and lance into the bath. This cycle example employs a relative speec increase in the forwards direction to reduce the transitional effects of "double-dosing" near traverse reversal points. A wide range of traverse cycle variations are available, such as concentrating feed entry along selected areas by stroke acceleration and deceleration, step-wise speed changes, or feeding during travel in one direction only, interrupting the Iced during travel in the other direction. Although the melting time in liquid metal and slag is very short for individual pellets or particles injected by lance, for example, less than a minulc for DRI pellets and 10 seconds for fines, the heat so absorbed when the jet of solid charge materials is focused in one location can rapidly reduce the liquid temperature below the melting point, creating a frozen island of solid metal which interferes with process operahor Cyclical lance traversing as a feature of this invention not only eliminates this problem, but assures the maintaining of melting ar d process reaction rates, at any given average metal an 1 slag bath temperature. In addition to solids injection lance 34, gas-solid-liquid reaction zone 8 is typicaliy heated by a burner (not shown) supplying concentrated heat for melting, and also utilizes a lance supplying post-combustion oxygen at relatively low pressure, preferably such as described in my co-pending patent application No 08/916.395 (illustrated in Figs 2. 8 &. 91 Given the typically numerous interacting process variables involved, the optimum distance of insertion of these lances into the gas-solid-liquid reaction zone is initially unknown and can vary during processing, and is therefore most suitably established by trial and error dunng operation. These lances therefore are preferablv mounted on a variably - positioned carriag similarly to lance 34, aligned in parallel as illustrated by example cross-section Fig 5 showing a solids injection lance 34, burner 44 and post-combustion oxygen lance 45 caned in parallel above an oscillating conveyor 27 A high-velocity bath oxygen injection lance c in also be introduced separately, or as a combination with lance 45 as a variation of known combined oxygen injection lance technology In addition to variations in the speed of traversing, span of traversing stroke and longitudinal position of the span, the process and apparatus also provides for charging the makeup of the solids injected along different sections of the traverse span For example. additive carbon could be programmed for injection only during the last 50 per cent of the forwards and first 50 per cent of the backwards lance stroke, as regulated by opening and closing a remotely-operated valve on the injected carbon supply line. This can obviate the need for another separate carbon injection lance whilst obtaining the desired distribution ol carbon entry into the bath for a high degree of post-combustion The mode of operation and equipment configuration may be varied according to the makeup of the charge materials and the processing functions to be performed This is illustrated by the diagram Figs. 4 and 5 showing example distributions of the charge material entry and other inputs into the melting process. In Case A. Fig. 4, recycled ferrous scrap along with fluxes and additive reagents is distributed along the first 50 per cent of the gas-solid-liquid reaction zone by cyclical stroking of th: oscillating charge material feed conveyor, relying upon the furnace rotation and inclination to distribute the unmclted materials into the balance of the zone. Carbon is shown as separately injected near the 7.or e entry, thereby lowering the bath temperature and increasing heat transfer rate, such as described in my U.S. Patent No. 5,163,997. Although a metallic charge normally carries some surface oxides, separately injecting post-combustioi. oxygen usually weald only ae warranted in the case of supplementary bath oxygen injection, as an optional practice in this case Otherwise, the relatively small amounts of CO and H2 generated can be reacted wiht supplementary burner oxygen. In Case B, DRI and'or iron carbide as the principal charce materials arc preferably fed by a pneumatic solids injection lance, along with carbon for reducing residual iron oxides with the traverse span extending along a major portion of the gas-sohd-liquid reaction zore Case C illustrates a combination of recycled scrap charged by conveyor with granular materials charged pneumatically by solids injection lance, including overlapping span? of traverse travel. Case D, Fig, 5 illustrates the addition of supplementary hath oxygen injection, as well as separate injection of oxygen for post-combustion into the hot gas stream Monitoring of exhaust gas temperature and composition, as well as product composition, temperature and production rate during operation facilitates selecting the most suitable inputs and their distribution. In any one of example cases A to D. the charge materials can also include metal oxides, for example, in ferrous melting, mill scale, BOF slag, raw or preprocessed EAF dust, along with additional carbon as an additive reagent for reducing (he oxides to metal. Example Case E illustrates the melting of recycled aluminum and/or primary aluminum ingot and the like which usually are of a size suitably charged by an oscillating conveyor. Exposed surfaces of either unrnelted or molten aluminum oxidize rapidly ai elevated temperature forming aluminum oxide dross. Fluxing agents are required to retard oxidation and also to accelerate inclusion removal, recover metallic aluminum from dross aid clear, oxide buildup from furnace walls. Distributing charge material entry as in the diagran example to obtain essentially immediate immersion minimizes the oxidation of unmelted aluminum. Cover fluxes to prevent oxidation of molten aluminum b7 the hot furnace liases typically comprise a near-eutectic KCI/NaCl mixturs. often also including additive fluoride, chloride or carbonate compounds. Various fluxes are also employed as dressing fluxes, cleaning fluxes and degassing fluxes in the art of aluminum melting, for example. MgCl2,. various alkali fluoride and chloride salts, as well as oxygen-containing compounds for exoihermic reaction It is known that these fluxes are usually more effective when delivered by flux injection whereby they melt into small droplets within the bain offering a large specific surface area in contact with the melt as they float to the surface Distributing the-injected fluxes longitudinally along the continuous reaction zones, as in the diagram of (his invention, substantially increases the propoiuon of the melt surfaces directly contacted by the flux droplets. The lowering of magnesium content commonly referred to as "demageing1. also is a common requirement of secondarv aluminum melting, usually accomplished b. si b-surface injection of chlorine -containing gases or a combination of fluxes and case^ usin ; simple gas-injection lances, or including spinning nozzles and submerged porous plugs to obtain smaller bubbles which are more evenly and widely distributed in the melt The ('as : P. illustration depicts how the slag covering and at least part of the degassing, cleaning and demagging functions may be conducted by distributing the injection of solids and gases longitudinally along the elongate continuous reaction zones within the rotary furnace according to the invention. Fig. 6 illustrates a preferred embodiment of a lance nozzle 45 for issuing post-combustion oxygen into the hot gas stream 15. Oxygen is introduced via annulus 46 between water-cooled cylindrical outer pipe 47 and water-cooled inner pipe 48 carrying an oxygen ;el flow rate, direction and distribution control disc 49. Annular slit nozzle opening 50 is tiier :by defined between the end of outer pipe 47 and the back face of disc 49. through which oxygen jet 51 fans radially outwards in a continuous curtain of oxygen transversely spanning across the axially flowing gas stream. Disc 49 is preferably water-cooled, such as by cooling vvat:r supplied by internal water pipe 52 and returned via inner pipe annulus 53. Opening 50 car be shaped to enhance effectiveness of mixing with the gas stream to increase reaction with combustibles. For example, in the illustration, slit opening 50 is angled upstream at about 30° to the perpendicular, emitting a cone-shaped curtain radially outwards which is also countercurrent to the gene al gas stream flow 15. Also, the sector of opening 50 dirccting oxygen jet 51 downwards towards bath 7 is made wider than the sector directing the jet upwards, thereby delivering a higher volume of oxygen to directly intercept the CO evolving from the bath surface. The width of opening 50 and thereby the oxygen flow rate al a selected pressure and velocity, can be varied by axia! location adjustment of pipe 48 by axial sliding of inner pipe locating guide 54 to diffe-ant locations within outer pipe 47. for example, by applying different thicknesses of spacer washers against aji entry-end flange of inner pipe 48. Fig 7 illustrates a gas stream oxygen lance infection nozzle embodiment variation, in which a similarlv-mounted disc acts only as a deflector disc 55. adapted tc deflect oxygen jet 56 outwards projecting an annular oxygen curtain across the furnace ga; stream cross-section Such gas stream oxygen injection provides for the post-combustion oxygen intersecting the bath surface transversely to the direction of metal flow, as well as the complete gas stream cross section. The hot reacted gas mixture then flows for a signtf cant distance simultaneously in contact and heating the partly melted bath and the furnace wal s which, in turn, continuously agitate the bath and pass on this wall heat from post-combusiion into the bath when rotating under it. The invention thus provides the clear advantage of increasing PCD and HTE over pnor art processes, for example, electric-arc furnace and oxygen converter process technologies. Various features previously described with reference to Fig. 1 are repeated in Fig. 8, which also illustrates various additional or alternative optional features. In order to facilitate slag skimming and discharge over the lip of either end opening 4 or 5. such as into slag pot 60, as well as facilitate general access to the interior of furnace 1, it can be tillable longitudinally about a pivotal support 61, such as by a hydraulic cylinder 62. linear actuator or the like. Alternatively, support 61 can be positioned directly under cither set of rollers 3. with actuator 62 supporting the other set. Some processing requirements favor using a slag n zone 10 having a different layer thickness and composition than the slag in zone 8. The transfer of slag between zones 8 and 10 can be restricted by the crest of an annular dam 63 sized to project above the hig'iest level of the slag surface. One or more channels 65 throug darn 63 can allow the substantially free passage ofliquid metal from dam channel entrance opening 81 to dam channel exit opening 82, whilst restricting the passage of slag Referring to Figs. 9 and 10, in order to avoid substantial transferring of slag through channel(s) 55 car be openings 81. 82 pass through the slag layer, during rotation of furnace 1. the channel '55 can be sloped upwards in the general direction radially towards the furnace axis of rotation from openings 81. 82 up to a channel interior crest 85 (not so illustrated in Figs 8.ID At the two positions during each fumace revolution lha' the openings 81.82 pass through the slag layer, it is seen that the channel interior crest invert 86 should be higher than the tops 83 and 84 of openings 81 and 82 respectively, preferably by a distance at least equal to the maximum thickness of the slag layer, as illustrated, invert 86 thereby actine as a barrier adapted to limit the interchange of slag '^etvveen zones 8 and 10 in either direction durini; operalion Fluxes, alloys and gases, such as required for metal composition adjustment and refining in zone 10. can also be injected using a longitudinally traversing lance assembly 6(. as essentially analogous to lance 34 A coherent jet lance for injection of oxygen or othrr treatment gas, as known to maintain a narrow gas stream at high velocity for distances of 2 meters or more from the nozzle can also be employed to increase longitudinal coverage using a less extensive mechanical assembly for lance manipulation Optional post-treatment processing steps can be included since the objects include yielding a broad range of products having controlled and specific composition and properties. For example, the lower portion of liquid metal column 68 having its top surface 69 at a leve above bath 9 governed by regulated vacuum pressure maintained within vessel 20. can be extended laterally to include a metallurgical post-treatment pool 70 confined within a latcra1 channel enclosure 71 through which the metal flows preceding discharge, havinii a pool surface 72 maintained at a lower elevation and higher pressure than surface 69. When at or near atmospheric pressure, surface 72 is typically also proximate the surface level of metal and slag 9, 11, as governed by the principles of Bernoulli's theorem. The metal may be discharged through a submerged nozzle 73 Adjustable flow rate control of a nozzle throttling slide-gate 74, metering pin or stopper rod then also controls the furnace discharge flow through siphon lube 19, at the same average rate as the metal discharge through the nozzle. Alternatively, the metal can be lip-discharged from pool 70 by overflow, in which case the furnace discharge rate requires control by other means, such as by varying the vacuum pressure within enclosure 20 or tilt control of the post-treatment assembly. Also, high vacuum pressures within enclosure 20 can remove substantial quantities of uases dissolved in the metal prior to passage into pool 70. In another variation, siphon tube lfl can be discharged directly into the evacuated space 16 over top surface 69. reaii/.ing a degree o spray degassing, but also requiring direct regulation of the discharge flow rate through fibc 19 by varying vacuum pressure, or other means Sealing of channel enclosure 71 and closing throttling valve 74 and other outlet openings facilitates the initial evacuation of vessel 20 tc start metal flow. Vessel 20 can also be equipped with an entry valve 67 which is maintained closed during evacuation, then opened to allow starting flow As an example (see Fig. 8), aluminum processing commonly involves employing a mixture of inert gases and reactive gases for degassing and demaggme the molten rncta! following melting, which may be introduced by way of porous plugs or from a treatment g.,s chamber 75 through porous refractory 76 as the metal courses through a sencs of baffles 71 to increase the effective length of the post-treatment channel The metal then passes upwards through a filter 78 for removal of non-metallics and the like, then downwards discharging through a nozzle 73 having a discharge rate controlled by a flow control pin. stopper rod ot throttling slide-gate valve 74. The metal being processed can be heated, such as by electric resistance heating elements 79 and the surface 72 protected from oxidation by introducing a supplementary blanket gas 80, also providing for evacuation of these gases into the exhaust gas handling and treatment system. Numerous variations of this metal-treatment system ire feasible, for example, rotary gas diffusers for shearing injected treatment gases into small bubbles could be employed in addition to, or in place of, the gases introduced through porous refractory 76. Various treatment gases can be employed, for example, aluminum treatment gases typically are blends of inert nitrogen and argon with reactive chlorine and fluorine compounds, according to the art of degassing and filtration refining systems preceding pouring for casting. The very high temperatures characteristic of oxy-fuel flames can be excessive when melting metals having relatively low melting points, such as aluminum and lead. Off-gas recirculation, such as illustrated in Fig. 11, can mitigate this problem. A substantial and controlled portion of the off-gases can be recirculated through off-gas recirculation duct 92, usually lined with refractory', by an off-gas recirculation blower 93. usually equipped with a water-cooled impeller. Blower 93 may be operated at a controlled variable speed, or the volume flowing may also be controlled by a damper 94. also water-cooled The exhaust gases 99 comprising the non-rectrculated off-gases pass directly through exhaust duct v:.. a so preferably equipped with a damper 96. Duct 92 may exit directly into the furnace, as ab.o equipped with a separate oxy-fuel burner or. as illustrated, into a prc-combustion chamber 97 which is also fired by an oxy-fuel burner 98. with the product: of combustion, in 'urn. discharging into the furnace reaction zones and forming the hot gas stream The overall rcnilt is generally to decrease the average furnace and exhaust gas temperature improving process thermal efficiency, also avoiding localized overheating and unnecessary nitrogen oxide formation. Exhaust gases 99 can also be utilized to preheat the charge materials, fuel or oxygen by recuperation, further improving the process heat economy. WE CLAIM: 1. A process for continuous melting a charge of solid metallic materials comprising metals selected from the group consisting of recycled scrap iron and steel, pig iron, copper, aluminum, lead, zinc, chromium, nickel, tin, manganese, and direct-reduced iron which has previously been produced by a separate processing facility carrying out solid-state: direct reduction of iron oxides and which has been discharged and cooled to ambient temperature and exposed to the outside atmosphere for transportation and storage in an elongate rotary furnace (1) having horizontal longitudinal disposition arid annular end openings (4,5) maintaining a partially melted bath of metal (7) carrying a floating layer of slag (11) in an elongate gas-solid-liquid reaction zone (8) with a hot gas stream (15) passing over said metal (7) and slag (11) within said furnace (1), characterized by: conveying said metallic charge materials through atleast one of said end openings (4,5) into said hot gas stream (15) and along said gas-solid-liquid reaction zone (8); downwardly projecting said metallic charge materials into said bath; traversing the location of said downwardly projecting successively backwards and forwards along a longitudinal traverse span of said gas -solid-liquid reaction zone (8) and thereby distributing the position of charge materials entry (32, 40) of said charge material into said bath (7) longitudinally along said gas-solid-liquid reaction zone (8); and along liquid metal flow out of said gas-solid-liquid reaction zone (8) to provide fro replenishing said bath (7) by said conveying and downwardly projecting of said metallic charge materials. 2. A process as claimed in claim 1 wherein said conveying includes entraining and propelling by pressurized carrier gases atleast a portion of said charge materials through a solids injection lance (34) cantilevered longitudinally within said hot gas stream (15); said downwardly projecting comprises issuing a jet of said charge materials and carrier gases from a nozzle (35) of said lance into said bath (7); and said traversing comprises stroking said lance (34) successively backwards and forwards longitudinally distributing the position of said nozzle (35) and thereby said position of charge material entry (40) along said traverse span. 3. A process as claimed in claim 1 wherein said conveying includes propelling at least a portion comprising a conveyor-fed portion of said solid charge materials by longitudinal oscillation of an oscillating conveyor (24) cantilevered longitudinally within said hot gas stream( 15); said downwardly projecting comprises dropping said charge materials from a distributing the position of said discharge lip (25) of said conveyor (24) into said bath (7); and said traversing comprises stroking said conveyor (24) successively backwards and forwards longitudinally distributing the position of said discharge (25) and thereby said position of charge material entry (32) along said traverse span. 4. A process as claimed in claim 3 wherein said said position of charge material entry (32) of said portion of charge materials along a conveyor-fed portion of said traverse span and also includes entraining and propelling by pressurized carrier gases another portion of said solid charge materials through a solids injection lance (34) cantilevered longitudinally within said hot gas stream (15); said downwardly projecting comprises issuing a jet of said another portion of charge materials and carrier gases from a nozzle (35) of said lance (34) into said bath (7); and said traversing comprises stroking said lance (34) successively backwards and forwards longitudinally distributing the position of said nozzle (35) and thereby said entry (40) location of said another portion of said charge materials along a lance-fed portion of said traverse span. 5. A process as claimed in claim 4 wherein said lance-fed portion overlaps said conveyor-fed portion of said traverse span across a common traverse span portion of said longitudinal traverse span, including coordinating the travel cycle time intervals and positions of said lance nozzle (35) relative to said discharge lip (25) thereby avoiding crossing over between charge materials issuing from said lance nozzle (35) and those dropping from said discharge lip (25), across said common traverse span during traversing. 6. A process as claimed in claim any of the preceeding claims having distributing the feed rate of charge materials issuing from said jet unequally along said lance-fed portion of said traverse span by varying the flow rate of entrained charge materials during stroking of said lance (34), whilst maintaining a substantially constant average total feed rate of charge material across the total length of said lance-fed portion. 7. A process as claimed in any of the preceeding claims comprising distributing the feed rate of charge materials issuing from said jet unequally along said lance-fed portion of said traverse span by varying the velocity of said stoking of said lance (34), whilst maintaining a substantially constant average total feed rate of charge material across the total length of said lance-fed portion. 8. A process as claimed in claim 1 wherein said metallic materials contain metal oxides and said additive reagents include carbonaceous material, including effecting reduction of said metal oxides in said bath (7) and slag (11) by carbon contained in said carbonaceous material, thereby forming liquid metal in said gas-solid-liquid reaction zone and releasing carbon monoxide into said hot gas stream. injecting oxygen into said hot gas stream effecting post-combustion of a major portion said carbon monoxide forming carbon dioxide prior to the exit of said hot gas stream from said gas-solid-liquid reaction zone. 9. A process as claimed in any of the preceeding claims including maintaining a gas-liquid reaction zone adjoining said gas-solid-liquid reaction zone (8); maintaining a general movement of materials within said partially melted metal bath (7) in a direction towards said gas-liquid reaction zone (10) allowing said liquid metal to flow on into said gas-liquid reaction zone (10); heating said gas-liquid reaction zone (10) by combustion of fuel and oxygen to regulate the liquid metal temperature and also form said hot gas stream (15); effecting general flow of said hot gas stream (15) countercurrent to said general movement of materials for exhaustion through the annular end opening (4) adjacent to said gas-solid-liquid reaction zone (8); and discharging hot liquid metal from said gas-liquid reaction zone. 10. A process as claimed in claim 1, 2, 3, 4, 7, or 8 wherein the total distance across said longitudinal traverse span comprises more than 50 percent of the length of said gas-solid-liquid reaction zone. 11. A process as claimed in claim 1, 2, 3, 4, 7, or 8 including discharging of said liquid metal (9) by siphoning through a suction tube (19) into a vacuum chamber (20) containing a liquid metal column under (18) a controlled vacuum pressure; allowing said hot liquid metal to flow from said vacuum chamber (20) into a post-treatment pool (70) within a lateral channel enclosure (71) under a pressure higher than said controlled vacuum pressure; introducing metallurgical treatment gases into the metal comprising said pool (70); and discharging said liquid metal from said pool. 12. A process as claimed in claim 11 including maintaining a continual flow of said liquid metal through said pool (70) and discharging said metal through a submerged nozzle (73), also including regulating the discharge flow rate through said nozzle by throttling the nozzle opening, thereby also controlling the average metal flow rate through said siphon tube (19). 13. A process as claimed in claim 11 or claim 12 wherein said pressure higher than said controlled vacuum pressure comprises substantially atmospheric pressure. 14. A process as claimed in claim 11, 12 or 13 including the step of filtering out non-metallic inclusions and impurities in the metal flowing through said pool by passage of said metal through a porous filter prior to said discharging. 15. A process as claimed in claim 1, 2, 3, 4, 7 or 8 including maintaining a gas-liquid reaction zone adjoining said gas-solid-liquid reaction zone (8); heating said gas-liquid reaction zone (10) by combustion of fuel and oxygen to regulate the liquid metal temperature and also form said hot gas stream (15); effecting general flow of said hot gas (15) stream countercurrent to said general movement of materials for exhaustion through the annular end opening adjacent to said gas-solid-liquid reaction zone (8); obstructing the flow of said slag between said gas-solid-liquid and said gas-liquid reaction zone by maintaining the inner perimeter of an annular dam above the top surface of said layer of slag (11); allowing said liquid metal to flow on into said gas-liquid reaction zone by way of at least one channel (65) through said dam which is submerged within said bath during a portion of each revolution; discharging slag as required through said annular end opening (4) adjacent to said gas-solid-liquid reaction zone; and discharging hot liquid metal from said gas-liquid reaction zone (10). 16. A process as claimed in claim 15 also including introducing materials selected from the group comprising fluxes and additive reagents into said gas-liquid reaction zone (10) forming a layer of slag within said gas-liquid reaction zone (10) having a different composition than said slag contained in said gas-solid-liquid reaction zone (8). 17. A process as claimed inn claim 1,2,3,4,7,8,10,16 or 17 including recirculating a potion of the hot furnace gases exhausted from one annular end opening (4) of furnace (1) into the other annular end opening (5) to mix with and comprises a portion of said hot gas stream (15) within furnace (1). 18. An apparatus for conducting the process of continuous melting of metallic charge materials comprising metals selected from the group consisting of recycled scrap iron and steel, pig iron copper, aluminum, lead, zinc, chromium, nickel, tin, manganese, and direct-reduced iron which has previously been produced by a separate processing facility carrying out solid-state direct reduction or iron oxides and which has been discharged and cooled to ambient temperature and exposed to the outside atmosphere for transportation and storage, in an elongate rotary furnace (1) having horizontal longitudinal disposition and annular end openings (4,5) maintaining a gas-solid-liquid reaction zone (8) within said furnace (1) adapted for containing a partially melted bath of metal (7) carrying a floating layer of slag (11) heated by a hot gas stream (15) passing over said bath (7); means for conveying solid charge materials through at least one of said end openings (4,5) into said hot gas stream (15) and along said gas-solid-liquid reaction zone (8) and downwardly projecting said charge materials into said bath (7); means for traversing said means for said conveying and downwardly projecting said charge materials successively backwards and forwards adapted for longitudinally distributing the entry location of said charge material entry (40) along a longitudinal traverse span of said gas-solid liquid reaction zone (8); and means for liquid metal exit allowing liquid metal to flow out of said gas-solid-liquid-reaction zone (8) adapted to provide for replenishing said bath by said solid charge materials. 19. An apparatus as claimed in claim 18 wherein said means for conveying and downwardly projecting said charge materials includes a pneumatic solids injection lance (34) cantilevered longitudinally into said hot gas stream along said gas-solid-liquid reaction zone with an exit nozzle (35) of said lance (34) directed downwardly adapted for injecting said solid charge materials into said partially melted metal bath (7); and means for said traversing comprises a reversing lance drive (39) adapted for stroking said lance (34) successively backwards and forwards along said traverse span. 20. An apparatus as claimed in claim 18 wherein said means for conveying and downwardly projecting said charge materials includes an oscillating conveyor (24) cantilevered longitudinally into said hot gas stream (15) along said gas-solid-liquid reaction zone with a discharge lip (25) of said conveyor (24) adapted for dropping said solid charge materials downwards into said partially melted metal bath(7). 21. An apparatus as claimed in claim 18 wherein said means for traversing comprises a reversing lance drive (39) adapted for stroking said lance successively backwards and forwards along a lance-fed portion of said traverse span; also includes an oscillating conveyor (24) cantilevered longitudinally into said hot gas stream (15) along said gas- solid-liquid reaction zone (8) with a discharge lip (25) of said conveyor (24) adapted for dropping said solid charge materials downwards into said partially melted metal bath (7), and said traversing comprises a reversing conveyor drive (31) adapted for stroking said oscillating conveyor successively backwards and forwards along a conveyor-fed portion of said traverse span. 22. An apparatus as claimed in claim 21 wherein said lance-fed portion overlaps said conveyor-fed portion of said traverse span across a common traverse span portion of said longitudinal traverse span, including traverse coordinating means adapted to control the travel cycle time intervals and position of said lance nozzle relative to said discharge lip during traversing thereby avoiding crossing over between charge materials issuing from said lance nozzle and those issuing from said discharge lip across said common traverse span during traversing. 23. An apparatus as claimed in claim 18,19,20 or 21 including means for maintaining a gas-liquid reaction zone (10) carrying substantially only hot liquid metal and slag adjoining said gas-solid-liquid reaction zone (8) within said furnace (1); means for introducing fuel and oxygen adapted for heating and regulating the metal temperature in said gas-liquid reaction zone (10) by combustion and forming said hot gas stream (15); means for effecting general flow of said hot gas stream (15) countercurrent to the general movement of materials into and through said gas-solid-liquid reaction zone (8) and exhausting said hot gas stream (15) through an adjoining annular end opening (4) of said furnace, and means for discharging hot liquid metal (9) from said gas-liquid reaction zone (10). 24. An apparatus as claimed in claim 18 comprising: a vacuum vessel (20) carried adjacent to one of said annular end openings (5) having a siphon-tube (19) with its outlet connected into said vessel (20) and its inlet adapted for insertion through said end opening (5) into the liquid metal (9) within said furnace (1); means for evacuation and for maintaining a controlled vacuum pressure within said vessel causing liquid metal flow through said suction tube (18) adapted for forming and maintaining a liquid metal column (68) within said vessel; a lateral channel enclosure (71) communicating with said metal column (68) adapted to carry a post treatment pool of metal (70) flowing out from said column (68) under a pressure higher than said controlled vacuum pressure; and means for discharging said liquid metal from said post-treatment pool (70) having a submerged nozzle (73) equipped with a throttling valve (74) for regulating the rate of discharging of said metal; and an overflow lip from said channel enclosure (71), which also includes means for throttling of said flow through said suction tube (19). 25. An apparatus as claimed in claim 24 including means for post- treatment gas supply (75, 75) adapted to introduce treatment gases into the metal flowing within said pool (70). 26. An apparatus as claimed in claim 24 wherein said channel enclosure (71) includes baffles (77) adapted to increase the total distance traveled by liquid metal between entry from said column (68) and the exit of said discharging. 27. An apparatus as claimed in claim 24, 25 and 26 wherein said pressure higher than said controlled vacuum pressure comprises substantially atmospheric pressure. 28. An apparatus as claimed in claim 24,25 26 and 27having means for sealing of said lateral channel enclosure (71) adapted for excluding access of air to the surface (72) of said post treatment pool (70). 29. An apparatus as claimed in claim 23 having an annular dam (63) proximate the junction between said gas-solid-liquid (8) and gas-liquid (10) reaction zones which extends radially inwards from the inner side walls of rotary furnace (1) to an annular dam crest (91) with an invert at a level higher than the surface of the layer of slag (11) during the full rotation of the furnace, thereby being adapted to obstruct the longitudinal transfer of slag (11) between said two zones (8,10). 30. An apparatus as claimed in claim 29 wherein said dam (63) includes at least one channel (65) communicating longitudinally through said dam (63) with a dam channel entrance opening (81) out of said gas- solid-liquid reaction zone and a dam channel exit opening (82) into said gas-liquid reaction zone (10), adapted to allow said liquid metal exit from said gas-solid-liquid reaction zone (8). 31. An apparatus as claimed in claim 30 wherein said channel (65) is sloped upwards in the general direction radially towards the furnace axis of rotation of furnace (1), reaching a crest (86) within said channel (65) wherein the invert of said crest (86) is at a higher elevation than the elevation of the top of said dasm channel entrance opening (81) during the portions of each revolution of said furnace when said top is passing through said layer of slag (11), said crest (86) thereby being adapted to substantially block transfer of slag from said gas-solid-liquid reaction zone (8) into said gas-liquid reaction zone (10) through said channel (65) during operation. 32. An apparatus as claimed in claim 31 wherein said crest (86) is intermediate between said entrance opening (81) and said exit opening (82), thereby being adapted to block transfer of slag in either direction between said gas-solid-liquid (8) and gas-liquid reaction zone (10). 33. An apparatus as claimed in claim 18 having an exhaust gas recirculation duct (92) adapted for transferring a portion of the hot furnace gases exhausted from annular end opening (4) and re- introducing them into furnace (1) through the other end opening (5), thereby recirculating said portion of the exhaust gases to mix with and comprise a portion of said hot gas stream (15) and discharging only the remaining exhaust gases (99).

Full Text

The present invention relates to a process for continuous melting a charge of solid metallic materials and a process for the same.
The invention relates to melting of metals and, more particularly, to a rotary furnace process and apparatus applicable to continuous melting of predominantly metallic charge materials.
Known commercial melting processes have inherent processing difficulties and disadvantages only partly overcome by improvement to design and operating practice. As a ferrous melting example, in electric-arc furnace (EAF) melting of iron and steel scrap, unmelted charge materials are heated to melting temperature with solid surfaces contacting ambient air or hot oxidizing gases, thereby generating oxide particulates and lowering yield. The heat input is focused on a small area within the furnace relative to the total area occupie J by the charge materials. Furthermore, carbon monoxide generated by oxygen injection into the metal bath is only partially burned to carbon dioxide by post-combustion before exit iron the EAF, and only a fraction of the heat so released is transferred back into the charge, Cupola melh, sas like disadvantages, as well as limitation to production of cast iron, ralhei than steel. As a nonferrous example, reverberatory aluminum melting furnaces arc widely applied commet. '"'ly and focus the location of unmelted charge in a small area in relation tc the sources and broad distribution of available heat in the furnace.
Elongated rotary melting furnaces employing a partially melted bath into which a solid charge is fed overcome some of the above deficiencies by means of continuous bath
stirring and advancing action, in combination with efficient flame.-to-wall, followed by wall-to-charge heat transfer during each furnace rotation. Access for introduction of the metallic charge materials, fluxes and reagents into the process, however, is only via annular furnace end openings, whereas the process mass transfer, heat transfer and process chemical reaction requirements vary and are distributed along the length of the reaction zones. As an example, when cold charge materials are introduced into a partially melted metal bath only adjaceni: to the entry opening, unmelted material may aggregate, creating islands of partially melted material and the like when, at the same time, charge further along the furnace is fully melled and becoming overheated. Unmelted islands of metal exposed to hot-furnace gases are also
subject to increased oxidation and loss as oxide particulates. Such problems obviously represent deficiencies in the control of process chemical reactions, mass transfer and heat
transfer, and can also be- estriction on the maximum charging and production rat
obtainable. It is therefore a principal object of the invention to distribute the melting heal
reguirement of unmelted charge materials along the elongated reaction zones according to the
distribution of heat available to effect melting, with the corollary object of fast melting of tin;
metallic charge materials.
Metallic charge materials characteristically carry varying percentages of metal oxide: and other impurities as metal oxides, other metals, other compounds, dissolved gases, other elements such as phosphorous, sulphur and the like. Fluxes and additive reagents arc
required as components of the charge materials for reaction with these impurities, along with
the metallic charge during processing, tc obtain effective process parameters and desired ane product composition following melting. Perhaps the most common example of an additive reagent is carbon for reduction of metal oxides to increase the yield of metal and/or for alloying the metal to obtain a specific range of dissolved carbon in the melt. It is naturally desirable that the carbon be introduced at the most effective locations to obtain the desired process reactions, such as reaction with metal oxides or oxygen, evolving carbon monoxide (CO) into the furnace gases, and then effecting a high degree of CO post-combustion (PCD). with a good heat transfer efficiency (HTE) into the furnace charge of the heat so liberated prior to the furnace gases exiting the furnace, and for control of the product composition, it s thus another principal object of the invention to distribute the introduction of fluxes and reagents along elongated process reaction zones according to the distribution of process chemical reaction requirements.
The invention provides a process and apparatus for continuous metal melting in a horizontally-disposed elongate rotary furnace comprising maintaining a partially melted hath of metal carrying a floating layer of slag in an elongate gas-solid-liquid reaction zone heat.ed by a hot gas stream passing over the metal and slag within the furnace; conveying solid charge materials comprising metallic materials, fluxes and additive reagents through an annular furnace end opening and along the gas-solid-liquid reaction zone and downwardly
projecting them into the bath; traversing the position of said downwardly projecting successively backwards and forwards thereby distributing the entry location of charge materials into the bath along a longitudinal traverse span, and allowing liquid metal to (low out of the gas-solid-liquid reaction zone thereby providing for replenishing the hath with fresh solid materials. Said traverse span preferably comprises a major portion of the length of the gas-solid-liquid reaction zone.
When applied to granular or pelletized charge materials less than about 3 cm. in size, for example, DRI pellets, granular iron carbide, pulverized coal, lime, crushed and screen limescone and ferroalloy additives, said conveying suitably comprises entraining the charge materials and propelling them by pressurized carrier gases through a solids injection lance cantilevered longitudinally within the hot gas stream in the gas-solid-liquid reaction zone and said downwardly projecting comprises issuing a jet of charge materials and carrier gases downwards from a lance nozzle into the partially melted metal bath whilst stroking the lance successively backwards and forwards distributing the entry location of charge material longitudinally along said traverse span. When applied to larger-sized charge materials, such as recycled scrap metals, pig iron, hot briquetted iron (HBI). lump coal or coke, lump fluxes-and the like, said conveying suitably comprises propelling the charge mau.ials by oscillatio of an oscillating conveyor, also cantilevered along the gas-solid-liquid reaction ?.one. and sa c! downward projecting comprises dropping the charge materials downwards from a discha-ge lip of the conveyor into the bath whilst stroking the conveyor backwards and forwards. Process requirements usually favor charging by a combination of oscillating conveyor and solids injection lance, in which case some overlapping of the lance and conveyor traverst spans is usually desirable, in which case the invention includes controlling the travel eye e time intervals and relative positions of the lance nozzle and conveyor discharge lip to avoid interference during entry between charge materials issuing from the lance nozzle and those dropping from the conveyor discharge lip at any time of passage across the common span oi travel.
Further, the rate of charge material flow can also be varied at different positions alorg the traverse span, even including interruptions, in order to realize longitudinal distribution of
charge material entry according to desired process parameters. This can be effected either DV varying the velocity of stroking on in the case of lancing, varying the lance inlet feed rate
Metals usually carry surface oxides, for example, iron rust. DRI or other pre-reduced virgin materials may also contain substantial content of unreduced residual metal oxides. Metals are also subject to high-temperature oxidation in-process. Also, dissolved carbon is often desired as a product constituent, such as with iron and steel melting. The charge materials therefore typically include carbonaceous materials carrying carbon as an additive reagent ror reduction of the oxides within the metal and slag bath, releasing carbon monoxide (CO) into the hot gas stream, which represents an unburned combustible or fuel. Selectively injecting oxygen into the hot gas stream facilitates the post-combustion of most of this CC within the process elongate reaction zones, and also ecovcry of the heat so released by diicct in-process heat transfer back into the partially meltej bath, with a PCD and HTE higher than that attainable by prior an processes.
The process and apparatus of the invention is most suitably applied with the rotary furnace length further elongated to incorporate a gas-liquid reaction zone adjoining the gas-solid-liquid reaction zone into which the liquid metal flows and accumulates for refining reactions and temperature adjustment prior to discharging from the furnace. This zone is heated by a burner from which the products of combustion form, the hot gns stream Ho'-virg on into the gas-sohd-liquid reaction zone countercurrent io the general movcuicnt of rratenals and exhausting through the annular end opening adjacent to the gas-solid-liquid re icuon zone The liquid metal may be discharged by periodical stopping the furnace rotation and opening a tap-hole discharging into a ladle or. alternatively . siphoning the metal continuo asly or semi-continuously via a refractory tube inserted into the metal through the furnace cam ilar end opening entering an adjacent vacuum vessel external to the furnace, from which the metal is withdrawn for casting or further processing Slag may be discharged by overflowing the lip of an annular end opening, including skimming as required or optionally assisted rny endwise furnace tilting through a small angle or. alternatively by a vacuum slag removal system such as described in my U.S. Patent No 5.305,990.

The process and apparatus is applicable to melting of various metals, for example, ferrous metals comprising iron and steel scrap, pig iron, DR1 pellets. HB1. and also various virgin or recycled forms of non-ferrous metals such as copper, aluminum, lead, zinc, chromium, nickel, tin and manganese. Mixtures of metals and metal oxides can he processed and it is adaptable to acidic or basic slag and refractory practice. It accommodates a wide range of charge material sizes, ranging from fine granular particles charge by pneumatic injection up to conveyor-sized pieces of recycled scrap metals. It facilitates continuous melting whilst retaining the options of discharging product either continuously, intermittent y or batch-wise It also facilitates high heat transfer rates throughout the process reaction zones and avoids localized overheating or undercooling, as well as provides goud metal-slag interaction towards composition approaching chemical equilibrium 10 realize high product yields and consistent chemtca composition. The invention therefore represents a fast, lear. quiet, thermally efficient and versatile technology for metal melting requirements.
Various other objects, features and advantages of the process and apparatus of this invention will become apparent from the following detailed description and claims, and by referring to the accompanying drawings in which:
Fig. 1 is a diagrammatic side view, partly in section, illustrating typical features of the process and apparatus of this invention; Fig. 2 is a section view along plan 2-2 of Fig. 1.
Fig 3 is a graph showing example traverse cycles for a case in which charge materials are introduced hy a combination of an oscillating conveyor and a solids iniection lance. Fig. 4 presents illustrative diagrams of exemplary general longitudinal distribution of charge material entry and other process inputs for three example cases; Fig. 5 presents diagrams for another two example cases;
Fig. 6 is a partial sectional side view illustration of a gas stream oxygen lance injection roz. le adapted to distribute oxygen for post combustion across the gas stream. Fig. 7 illustrates an alternative embodiment of a nozzle as in Fig. 8. Fig. 8 is a diagrammatic side view, partly in section, illustrating additional and alternative features of the process and apparatus of this invention; Fig. 9 is a section view along plane 9-9 of Fig. 8;
Fig. 10 is a section view along plane 10-10 of Fig. 9, with the portion of the plane below the central furnace axis seen as rotated approximately 45 degrees when the entrances into submerged channel 65 coincide with the slag layer; and
Fig. 11 is a diagrammatic side view, partly in section, illustrating off-gas rcurculation into the ho', gas stream comprising part of the process heat requirements.
Referring to Fig. 1, the elongate rotary furnace I with a refractory lining 6 and incorporating restricted annular end openings 4,5 is supported horizontally or with a slight incline within riding rings 2 which are carried by and rotated on rollers 3 in known manner A partially melted metai bath 7 is maintained in a gas-solid-liquid reaction zone 8and also i liquid metal bath 9 in a gas-liquid reaction zone 10 in the embodiment illustrated, with the baths carrying a floating layer of slag 11. The furnace is heated by burner 12 with the products of combustion from burning fuel 13 and oxygen and/or air 14 forming hot gas stream 15 passing countercurrent to the general charge movement exhausting through annular end opening 4 into conditioning chamber 16 entering exhaust duct 42 preceding a gas cleaning system and exhaustion to atmosphere. The process product liquid metal may be dis-hareed by periodic'!!y interrupting the furnace rotation tapning via tap-hole ! 1 miu ladle 18 or the like or. alternatively, siphoning during rotation via refractory siphon tube l(> into 3n adjacent vacuum vessel 20. This vessel optionally may be heated, equipped for uas injection, alloy and flux addition 21 and regulated discharge via a slide-gate 22 according to the ats 8 ladle and vacuum metallurgy
Large and irregularly-shaped charge materials such as recycled scrap metals or hriquerted reduced metai oxides are introduced by conveying along oscillating conveyer 2-which is cantilevered through end opening 4 and alone the gas-solid-liquid reaction zone. dropping them downwards from conveyor discharge lip 25 into the partially melted meial bath 7 The feed rate can be controlled by various means, such as a weighblock 58 as illustrated carrying a lifting magnet 57 for ferrous metals, or by other means of charging known quantities at controlled intervals. Various types of weighfeeders apply also to non-magnetic materials for loading conveyor 24, particularly for fluxes and additive reagents
A preferred embodiment of conveyor 24 is a horizontally oscillating type in which oscillator drive 26 oscillates conveyor deck 27 back and forth in short strokes relative to base 28 at high frequency and a controlled cycle, according to known practice in the art of conveying. The cantilevered portion of the conveyor deck is double-walled and baffled applying internal forced water cooling. Conveyor 24 also rides on rollers 29 running on tracks 30 which are substantially parallel to the axis of furnace 6. By stroking a hydraulic conveyor traversing cylinder 31 or equivalent, the position of charge material entry 32 is longitudinally distributed along traverse span 33 of gas-solid-liquid reaction zone 8.
Finer-sized materials consistently smaller than about 3 cm. are preferably introduced by entraining them in a carrier gas and conveying them pneumatically through a solids injec'ion lance 34 injecting the charge materials downwards from lance nozzle 35 into bath at a sufficient velocity to effect immersion in the metal and slag bath. In the embodiment, illustrated, lance 34 is clamped to a carriage 36 which rides on rollers 37 running on track 31: which is also substantially parallel to the axis of furnace 6 By stroking hydraulic lance traversing drive cylinder 39, the position of charge material entry 40 is longitudinally distribu^d along traverse span 41 of gas-solid-l;quid reaction zone 8 The lance 34 is usually water-cooled, but can also comprise heat resistant materials, as particularly adaptable to low melting-point alloys, such as those of aluminum or lead, or can even include the consumable type, as known in the art of injection lances Frontal support 87 includes a pivot 88 about which the inclination of lance 34 is adjustab!: by cylinder 89 camed on a rear support 90, enabling adjustment of the height of nozzle 33 in relation to the slag and bath, including immersion of the nozzle in the slag, or the slac and bath, as may be preferred for certain process conditions, such as slag foaming practice Supports 87. 90 can each be c irmd on a fixed jib or A-frame, or alternatively, connected on. a common carriage frame, whici may also be equipped to ride on wheels or tracks, adapted to provide longitudinal movener t of the entire assembly into and away from furnace end opening 4.
Zone 8 also is preferably heated directly by a burner 44, illustrated in Fig 2 as juxtaposed to solids injection lance 34, which can also be mounted for adjustable longitudir al positioning. Supplementary oxygen for post-combustion may be introduced via burners 44.
or also by way of a separate post-combustion lance 45, optionally also adjustably positioned. Since the hot gases within exhaust exit duct 43 are close to atmospheric pressure, dynamic sealing means such as gas-curtains are appropriate for sealing of the conveyor, lance and burner duct openings, as well as interface with end opening 4.
In the embodiment illustrated, liquid metal is passed on from the gas-solid-liquid reaction zone 8 by allowing it to flow out through the restricted passage effected by annular refractory dam 23 into the gas-liquid reaction zone 10. The dam 23 also serves to obstruct unmeited pieces of charge materials and the increased flow velocity over the channel restricted by dam 23 also substantially prevents any reverse flow of metal from zone 10 back into zone 8. In processing cases where close temperature control, refining time to obtain chemical equilibrium within bath and slag is not needed and/or processing in a supplcmcn ary ves;el is needed anyway, furnace 6 could be shortened substantially eliminating zone 10 aid intermediate dam 23. maintaining a partially melted bath extending from annular restricted opening 4 to opening 5. discharging metal and slag directly from gas-solid-liquid reaction zone 8.
Slag 11 may be removed by skimming or overflow over the iip of restricted opening 5. or even opening 4 in a case where slag flow countercurrent to the metal is beneficial to he process. Lengthwise tilting of fumace 6 through small vertical angles is an optional feitu c which is useful L-r the lip discharge ^f slag. Vacuum shg removal such as 'he removal system described in my U.S patent No. 5,305,990 can also he applied
Reference to Fig. 3 together with Fig. I illustrates example traverse cycles in which charge materials are introduced by the combination of an oscillating conveyor and a solid ; injection lance. Conveyor discharge lip 25 is traversed forward at a speed of ! ft./sec until it reaches LCmax. where it reverses and returns to LCmin at 3 ft./scc.. when the cycle is repeated. During the same time interval, lance nozzle 35 traverses forward to LI.max at a speed of 4 ft./sec., reverses and returns to LLmin at 1.33 ft./sec. In this example, the lane : and conveyor travel directionally in unison, but at different speeds over different spans. These spans also overlap, to include a common traverse span for entry of charge material:
from both conveyor and lance into the bath. This cycle example employs a relative speec increase in the forwards direction to reduce the transitional effects of "double-dosing" near traverse reversal points. A wide range of traverse cycle variations are available, such as concentrating feed entry along selected areas by stroke acceleration and deceleration, step-wise speed changes, or feeding during travel in one direction only, interrupting the Iced during travel in the other direction. Although the melting time in liquid metal and slag is very short for individual pellets or particles injected by lance, for example, less than a minulc for DRI pellets and 10 seconds for fines, the heat so absorbed when the jet of solid charge materials is focused in one location can rapidly reduce the liquid temperature below the melting point, creating a frozen island of solid metal which interferes with process operahor Cyclical lance traversing as a feature of this invention not only eliminates this problem, but assures the maintaining of melting ar d process reaction rates, at any given average metal an 1 slag bath temperature.
In addition to solids injection lance 34, gas-solid-liquid reaction zone 8 is typicaliy heated by a burner (not shown) supplying concentrated heat for melting, and also utilizes a lance supplying post-combustion oxygen at relatively low pressure, preferably such as described in my co-pending patent application No 08/916.395 (illustrated in Figs 2. 8 &. 91 Given the typically numerous interacting process variables involved, the optimum distance of insertion of these lances into the gas-solid-liquid reaction zone is initially unknown and can vary during processing, and is therefore most suitably established by trial and error dunng operation. These lances therefore are preferablv mounted on a variably - positioned carriag similarly to lance 34, aligned in parallel as illustrated by example cross-section Fig 5 showing a solids injection lance 34, burner 44 and post-combustion oxygen lance 45 caned in parallel above an oscillating conveyor 27 A high-velocity bath oxygen injection lance c in also be introduced separately, or as a combination with lance 45 as a variation of known combined oxygen injection lance technology
In addition to variations in the speed of traversing, span of traversing stroke and longitudinal position of the span, the process and apparatus also provides for charging the makeup of the solids injected along different sections of the traverse span For example.
additive carbon could be programmed for injection only during the last 50 per cent of the forwards and first 50 per cent of the backwards lance stroke, as regulated by opening and closing a remotely-operated valve on the injected carbon supply line. This can obviate the need for another separate carbon injection lance whilst obtaining the desired distribution ol carbon entry into the bath for a high degree of post-combustion
The mode of operation and equipment configuration may be varied according to the makeup of the charge materials and the processing functions to be performed This is illustrated by the diagram Figs. 4 and 5 showing example distributions of the charge material entry and other inputs into the melting process. In Case A. Fig. 4, recycled ferrous scrap along with fluxes and additive reagents is distributed along the first 50 per cent of the gas-solid-liquid reaction zone by cyclical stroking of th: oscillating charge material feed conveyor, relying upon the furnace rotation and inclination to distribute the unmclted materials into the balance of the zone. Carbon is shown as separately injected near the 7.or e entry, thereby lowering the bath temperature and increasing heat transfer rate, such as described in my U.S. Patent No. 5,163,997. Although a metallic charge normally carries some surface oxides, separately injecting post-combustioi. oxygen usually weald only ae warranted in the case of supplementary bath oxygen injection, as an optional practice in this case Otherwise, the relatively small amounts of CO and H2 generated can be reacted wiht supplementary burner oxygen.
In Case B, DRI and'or iron carbide as the principal charce materials arc preferably fed by a pneumatic solids injection lance, along with carbon for reducing residual iron oxides with the traverse span extending along a major portion of the gas-sohd-liquid reaction zore Case C illustrates a combination of recycled scrap charged by conveyor with granular materials charged pneumatically by solids injection lance, including overlapping span? of traverse travel. Case D, Fig, 5 illustrates the addition of supplementary hath oxygen injection, as well as separate injection of oxygen for post-combustion into the hot gas stream Monitoring of exhaust gas temperature and composition, as well as product composition, temperature and production rate during operation facilitates selecting the most suitable inputs and their distribution. In any one of example cases A to D. the charge materials can also
include metal oxides, for example, in ferrous melting, mill scale, BOF slag, raw or preprocessed EAF dust, along with additional carbon as an additive reagent for reducing (he oxides to metal.
Example Case E illustrates the melting of recycled aluminum and/or primary aluminum ingot and the like which usually are of a size suitably charged by an oscillating conveyor. Exposed surfaces of either unrnelted or molten aluminum oxidize rapidly ai elevated temperature forming aluminum oxide dross. Fluxing agents are required to retard oxidation and also to accelerate inclusion removal, recover metallic aluminum from dross aid clear, oxide buildup from furnace walls. Distributing charge material entry as in the diagran example to obtain essentially immediate immersion minimizes the oxidation of unmelted aluminum. Cover fluxes to prevent oxidation of molten aluminum b7 the hot furnace liases typically comprise a near-eutectic KCI/NaCl mixturs. often also including additive fluoride, chloride or carbonate compounds. Various fluxes are also employed as dressing fluxes, cleaning fluxes and degassing fluxes in the art of aluminum melting, for example. MgCl2,. various alkali fluoride and chloride salts, as well as oxygen-containing compounds for exoihermic reaction It is known that these fluxes are usually more effective when delivered by flux injection whereby they melt into small droplets within the bain offering a large specific surface area in contact with the melt as they float to the surface Distributing the-injected fluxes longitudinally along the continuous reaction zones, as in the diagram of (his invention, substantially increases the propoiuon of the melt surfaces directly contacted by the flux droplets. The lowering of magnesium content commonly referred to as "demageing1. also is a common requirement of secondarv aluminum melting, usually accomplished b. si b-surface injection of chlorine -containing gases or a combination of fluxes and case^ usin ; simple gas-injection lances, or including spinning nozzles and submerged porous plugs to obtain smaller bubbles which are more evenly and widely distributed in the melt The ('as : P. illustration depicts how the slag covering and at least part of the degassing, cleaning and demagging functions may be conducted by distributing the injection of solids and gases longitudinally along the elongate continuous reaction zones within the rotary furnace according to the invention.
Fig. 6 illustrates a preferred embodiment of a lance nozzle 45 for issuing post-combustion oxygen into the hot gas stream 15. Oxygen is introduced via annulus 46 between water-cooled cylindrical outer pipe 47 and water-cooled inner pipe 48 carrying an oxygen ;el flow rate, direction and distribution control disc 49. Annular slit nozzle opening 50 is tiier :by defined between the end of outer pipe 47 and the back face of disc 49. through which oxygen jet 51 fans radially outwards in a continuous curtain of oxygen transversely spanning across the axially flowing gas stream. Disc 49 is preferably water-cooled, such as by cooling vvat:r supplied by internal water pipe 52 and returned via inner pipe annulus 53. Opening 50 car be shaped to enhance effectiveness of mixing with the gas stream to increase reaction with combustibles. For example, in the illustration, slit opening 50 is angled upstream at about 30° to the perpendicular, emitting a cone-shaped curtain radially outwards which is also countercurrent to the gene al gas stream flow 15. Also, the sector of opening 50 dirccting oxygen jet 51 downwards towards bath 7 is made wider than the sector directing the jet upwards, thereby delivering a higher volume of oxygen to directly intercept the CO evolving from the bath surface. The width of opening 50 and thereby the oxygen flow rate al a selected pressure and velocity, can be varied by axia! location adjustment of pipe 48 by axial sliding of inner pipe locating guide 54 to diffe-ant locations within outer pipe 47. for example, by applying different thicknesses of spacer washers against aji entry-end flange of inner pipe 48. Fig 7 illustrates a gas stream oxygen lance infection nozzle embodiment variation, in which a similarlv-mounted disc acts only as a deflector disc 55. adapted tc deflect oxygen jet 56 outwards projecting an annular oxygen curtain across the furnace ga; stream cross-section
Such gas stream oxygen injection provides for the post-combustion oxygen intersecting the bath surface transversely to the direction of metal flow, as well as the complete gas stream cross section. The hot reacted gas mixture then flows for a signtf cant distance simultaneously in contact and heating the partly melted bath and the furnace wal s which, in turn, continuously agitate the bath and pass on this wall heat from post-combusiion into the bath when rotating under it. The invention thus provides the clear advantage of increasing PCD and HTE over pnor art processes, for example, electric-arc furnace and oxygen converter process technologies.
Various features previously described with reference to Fig. 1 are repeated in Fig. 8, which also illustrates various additional or alternative optional features. In order to facilitate slag skimming and discharge over the lip of either end opening 4 or 5. such as into slag pot 60, as well as facilitate general access to the interior of furnace 1, it can be tillable longitudinally about a pivotal support 61, such as by a hydraulic cylinder 62. linear actuator or the like. Alternatively, support 61 can be positioned directly under cither set of rollers 3. with actuator 62 supporting the other set. Some processing requirements favor using a slag n zone 10 having a different layer thickness and composition than the slag in zone 8. The transfer of slag between zones 8 and 10 can be restricted by the crest of an annular dam 63 sized to project above the hig'iest level of the slag surface. One or more channels 65 throug darn 63 can allow the substantially free passage ofliquid metal from dam channel entrance opening 81 to dam channel exit opening 82, whilst restricting the passage of slag Referring to Figs. 9 and 10, in order to avoid substantial transferring of slag through channel(s) 55 car be openings 81. 82 pass through the slag layer, during rotation of furnace 1. the channel '55 can be sloped upwards in the general direction radially towards the furnace axis of rotation from openings 81. 82 up to a channel interior crest 85 (not so illustrated in Figs 8.ID At the two positions during each fumace revolution lha' the openings 81.82 pass through the slag layer, it is seen that the channel interior crest invert 86 should be higher than the tops 83 and 84 of openings 81 and 82 respectively, preferably by a distance at least equal to the maximum thickness of the slag layer, as illustrated, invert 86 thereby actine as a barrier adapted to limit the interchange of slag '^etvveen zones 8 and 10 in either direction durini; operalion
Fluxes, alloys and gases, such as required for metal composition adjustment and refining in zone 10. can also be injected using a longitudinally traversing lance assembly 6(. as essentially analogous to lance 34 A coherent jet lance for injection of oxygen or othrr treatment gas, as known to maintain a narrow gas stream at high velocity for distances of 2 meters or more from the nozzle can also be employed to increase longitudinal coverage using a less extensive mechanical assembly for lance manipulation
Optional post-treatment processing steps can be included since the objects include
yielding a broad range of products having controlled and specific composition and properties. For example, the lower portion of liquid metal column 68 having its top surface 69 at a leve above bath 9 governed by regulated vacuum pressure maintained within vessel 20. can be extended laterally to include a metallurgical post-treatment pool 70 confined within a latcra1 channel enclosure 71 through which the metal flows preceding discharge, havinii a pool surface 72 maintained at a lower elevation and higher pressure than surface 69. When at or near atmospheric pressure, surface 72 is typically also proximate the surface level of metal and slag 9, 11, as governed by the principles of Bernoulli's theorem. The metal may be discharged through a submerged nozzle 73 Adjustable flow rate control of a nozzle throttling slide-gate 74, metering pin or stopper rod then also controls the furnace discharge flow through siphon lube 19, at the same average rate as the metal discharge through the nozzle. Alternatively, the metal can be lip-discharged from pool 70 by overflow, in which case the furnace discharge rate requires control by other means, such as by varying the vacuum pressure within enclosure 20 or tilt control of the post-treatment assembly. Also, high vacuum pressures within enclosure 20 can remove substantial quantities of uases dissolved in the metal prior to passage into pool 70. In another variation, siphon tube lfl can be discharged directly into the evacuated space 16 over top surface 69. reaii/.ing a degree o spray degassing, but also requiring direct regulation of the discharge flow rate through fibc 19 by varying vacuum pressure, or other means Sealing of channel enclosure 71 and closing throttling valve 74 and other outlet openings facilitates the initial evacuation of vessel 20 tc start metal flow. Vessel 20 can also be equipped with an entry valve 67 which is maintained closed during evacuation, then opened to allow starting flow
As an example (see Fig. 8), aluminum processing commonly involves employing a mixture of inert gases and reactive gases for degassing and demaggme the molten rncta! following melting, which may be introduced by way of porous plugs or from a treatment g.,s chamber 75 through porous refractory 76 as the metal courses through a sencs of baffles 71 to increase the effective length of the post-treatment channel The metal then passes upwards through a filter 78 for removal of non-metallics and the like, then downwards discharging through a nozzle 73 having a discharge rate controlled by a flow control pin. stopper rod ot throttling slide-gate valve 74. The metal being processed can be heated, such as by electric
resistance heating elements 79 and the surface 72 protected from oxidation by introducing a supplementary blanket gas 80, also providing for evacuation of these gases into the exhaust gas handling and treatment system. Numerous variations of this metal-treatment system ire feasible, for example, rotary gas diffusers for shearing injected treatment gases into small bubbles could be employed in addition to, or in place of, the gases introduced through porous refractory 76. Various treatment gases can be employed, for example, aluminum treatment gases typically are blends of inert nitrogen and argon with reactive chlorine and fluorine compounds, according to the art of degassing and filtration refining systems preceding pouring for casting.
The very high temperatures characteristic of oxy-fuel flames can be excessive when melting metals having relatively low melting points, such as aluminum and lead. Off-gas recirculation, such as illustrated in Fig. 11, can mitigate this problem. A substantial and controlled portion of the off-gases can be recirculated through off-gas recirculation duct 92, usually lined with refractory', by an off-gas recirculation blower 93. usually equipped with a water-cooled impeller. Blower 93 may be operated at a controlled variable speed, or the volume flowing may also be controlled by a damper 94. also water-cooled The exhaust gases 99 comprising the non-rectrculated off-gases pass directly through exhaust duct v:.. a so preferably equipped with a damper 96. Duct 92 may exit directly into the furnace, as ab.o equipped with a separate oxy-fuel burner or. as illustrated, into a prc-combustion chamber 97 which is also fired by an oxy-fuel burner 98. with the product: of combustion, in 'urn. discharging into the furnace reaction zones and forming the hot gas stream The overall rcnilt is generally to decrease the average furnace and exhaust gas temperature improving process thermal efficiency, also avoiding localized overheating and unnecessary nitrogen oxide formation. Exhaust gases 99 can also be utilized to preheat the charge materials, fuel or oxygen by recuperation, further improving the process heat economy.

WE CLAIM:
1. A process for continuous melting a charge of solid metallic materials comprising metals selected from the group consisting of recycled scrap iron and steel, pig iron, copper, aluminum, lead, zinc, chromium, nickel, tin, manganese, and direct-reduced iron which has previously been produced by a separate processing facility carrying out solid-state:
direct reduction of iron oxides and which has been discharged and cooled to ambient temperature and exposed to the outside atmosphere for transportation and storage in an elongate rotary furnace (1) having horizontal longitudinal disposition arid annular end openings (4,5) maintaining a partially melted bath of metal (7) carrying a floating layer of slag (11) in an elongate gas-solid-liquid reaction zone (8) with a hot gas stream (15) passing over said metal (7) and slag (11) within said furnace (1), characterized by:
conveying said metallic charge materials through atleast one of said end openings (4,5) into said hot gas stream (15) and along said gas-solid-liquid reaction zone (8);
downwardly projecting said metallic charge materials into said bath;
traversing the location of said downwardly projecting successively backwards and forwards along a longitudinal traverse span of said gas -solid-liquid reaction zone (8) and thereby distributing the position of charge materials entry (32, 40) of said charge material into said bath (7) longitudinally along said gas-solid-liquid reaction zone (8); and
along liquid metal flow out of said gas-solid-liquid reaction zone (8) to provide fro replenishing said bath (7) by said conveying and downwardly projecting of said metallic charge materials.
2. A process as claimed in claim 1 wherein said conveying includes
entraining and propelling by pressurized carrier gases atleast a portion of
said charge materials through a solids injection lance (34) cantilevered
longitudinally within said hot gas stream (15); said downwardly
projecting comprises issuing a jet of said charge materials and carrier
gases from a nozzle (35) of said lance into said bath (7); and said
traversing comprises stroking said lance (34) successively backwards and
forwards longitudinally distributing the position of said nozzle (35) and
thereby said position of charge material entry (40) along said traverse
span.
3. A process as claimed in claim 1 wherein said conveying includes
propelling at least a portion comprising a conveyor-fed portion of said
solid charge materials by longitudinal oscillation of an oscillating
conveyor (24) cantilevered longitudinally within said hot gas stream( 15);
said downwardly projecting comprises dropping said charge materials
from a distributing the position of said discharge lip (25) of said conveyor
(24) into said bath (7); and
said traversing comprises stroking said conveyor (24) successively backwards and forwards longitudinally distributing the position of said discharge (25) and thereby said position of charge material entry (32) along said traverse span.
4. A process as claimed in claim 3 wherein said said position of
charge material entry (32) of said portion of charge materials along a
conveyor-fed portion of said traverse span and also includes entraining
and propelling by pressurized carrier gases another portion of said solid
charge materials through a solids injection lance (34) cantilevered
longitudinally within said hot gas stream (15);
said downwardly projecting comprises issuing a jet of said another portion of charge materials and carrier gases from a nozzle (35) of said lance (34) into said bath (7); and said traversing comprises stroking said lance (34) successively backwards and forwards longitudinally distributing the position of said nozzle (35) and thereby said entry (40) location of said another portion of said charge materials along a lance-fed portion of said traverse span.
5. A process as claimed in claim 4 wherein said lance-fed portion
overlaps said conveyor-fed portion of said traverse span across a
common traverse span portion of said longitudinal traverse span,
including coordinating the travel cycle time intervals and positions of
said lance nozzle (35) relative to said discharge lip (25) thereby avoiding
crossing over between charge materials issuing from said lance nozzle
(35) and those dropping from said discharge lip (25), across said common
traverse span during traversing.
6. A process as claimed in claim any of the preceeding claims having
distributing the feed rate of charge materials issuing from said jet
unequally along said lance-fed portion of said traverse span by varying
the flow rate of entrained charge materials during stroking of said lance
(34), whilst maintaining a substantially constant average total feed rate
of charge material across the total length of said lance-fed portion.
7. A process as claimed in any of the preceeding claims comprising
distributing the feed rate of charge materials issuing from said jet
unequally along said lance-fed portion of said traverse span by varying
the velocity of said stoking of said lance (34), whilst maintaining a
substantially constant average total feed rate of charge material across
the total length of said lance-fed portion.
8. A process as claimed in claim 1 wherein said metallic materials
contain metal oxides and said additive reagents include carbonaceous
material, including effecting reduction of said metal oxides in said bath
(7) and slag (11) by carbon contained in said carbonaceous material,
thereby forming liquid metal in said gas-solid-liquid reaction zone and
releasing carbon monoxide into said hot gas stream.
injecting oxygen into said hot gas stream effecting post-combustion of a major portion said carbon monoxide forming carbon dioxide prior to the exit of said hot gas stream from said gas-solid-liquid reaction zone.
9. A process as claimed in any of the preceeding claims including
maintaining a gas-liquid reaction zone adjoining said gas-solid-liquid
reaction zone (8);
maintaining a general movement of materials within said partially melted metal bath (7) in a direction towards said gas-liquid reaction zone (10) allowing said liquid metal to flow on into said gas-liquid reaction zone
(10);
heating said gas-liquid reaction zone (10) by combustion of fuel and oxygen to regulate the liquid metal temperature and also form said hot gas stream (15);
effecting general flow of said hot gas stream (15) countercurrent to said general movement of materials for exhaustion through the annular end opening (4) adjacent to said gas-solid-liquid reaction zone (8); and
discharging hot liquid metal from said gas-liquid reaction zone.
10. A process as claimed in claim 1, 2, 3, 4, 7, or 8 wherein the total
distance across said longitudinal traverse span comprises more than 50
percent of the length of said gas-solid-liquid reaction zone.
11. A process as claimed in claim 1, 2, 3, 4, 7, or 8 including
discharging of said liquid metal (9) by siphoning through a suction tube
(19) into a vacuum chamber (20) containing a liquid metal column under
(18) a controlled vacuum pressure;
allowing said hot liquid metal to flow from said vacuum chamber (20) into a post-treatment pool (70) within a lateral channel enclosure (71) under a pressure higher than said controlled vacuum pressure;
introducing metallurgical treatment gases into the metal comprising said pool (70); and discharging said liquid metal from said pool.
12. A process as claimed in claim 11 including maintaining a continual
flow of said liquid metal through said pool (70) and discharging said
metal through a submerged nozzle (73), also including regulating the
discharge flow rate through said nozzle by throttling the nozzle opening,
thereby also controlling the average metal flow rate through said siphon
tube (19).
13. A process as claimed in claim 11 or claim 12 wherein said pressure
higher than said controlled vacuum pressure comprises substantially
atmospheric pressure.
14. A process as claimed in claim 11, 12 or 13 including the step of
filtering out non-metallic inclusions and impurities in the metal flowing
through said pool by passage of said metal through a porous filter prior
to said discharging.
15. A process as claimed in claim 1, 2, 3, 4, 7 or 8 including
maintaining a gas-liquid reaction zone adjoining said gas-solid-liquid
reaction zone (8);
heating said gas-liquid reaction zone (10) by combustion of fuel and oxygen to regulate the liquid metal temperature and also form said hot gas stream (15);
effecting general flow of said hot gas (15) stream countercurrent to said general movement of materials for exhaustion through the annular end opening adjacent to said gas-solid-liquid reaction zone (8);
obstructing the flow of said slag between said gas-solid-liquid and said gas-liquid reaction zone by maintaining the inner perimeter of an annular dam above the top surface of said layer of slag (11);
allowing said liquid metal to flow on into said gas-liquid reaction zone by way of at least one channel (65) through said dam which is submerged within said bath during a portion of each revolution;
discharging slag as required through said annular end opening (4) adjacent to said gas-solid-liquid reaction zone; and
discharging hot liquid metal from said gas-liquid reaction zone (10).
16. A process as claimed in claim 15 also including introducing
materials selected from the group comprising fluxes and additive
reagents into said gas-liquid reaction zone (10) forming a layer of slag
within said gas-liquid reaction zone (10) having a different composition
than said slag contained in said gas-solid-liquid reaction zone (8).
17. A process as claimed inn claim 1,2,3,4,7,8,10,16 or 17 including
recirculating a potion of the hot furnace gases exhausted from one
annular end opening (4) of furnace (1) into the other annular end
opening (5) to mix with and comprises a portion of said hot gas stream
(15) within furnace (1).
18. An apparatus for conducting the process of continuous melting of
metallic charge materials comprising metals selected from the group
consisting of recycled scrap iron and steel, pig iron copper, aluminum,
lead, zinc, chromium, nickel, tin, manganese, and direct-reduced iron
which has previously been produced by a separate processing facility
carrying out solid-state direct reduction or iron oxides and which has
been discharged and cooled to ambient temperature and exposed to the
outside atmosphere for transportation and storage, in an elongate rotary
furnace (1) having horizontal longitudinal disposition and annular end
openings (4,5) maintaining a gas-solid-liquid reaction zone (8) within said
furnace (1) adapted for containing a partially melted bath of metal (7)
carrying a floating layer of slag (11) heated by a hot gas stream (15)
passing over said bath (7);
means for conveying solid charge materials through at least one of said end openings (4,5) into said hot gas stream (15) and along said gas-solid-liquid reaction zone (8) and downwardly projecting said charge materials into said bath (7);
means for traversing said means for said conveying and downwardly projecting said charge materials successively backwards and forwards adapted for longitudinally distributing the entry location of said charge material entry (40) along a longitudinal traverse span of said gas-solid liquid reaction zone (8); and
means for liquid metal exit allowing liquid metal to flow out of said gas-solid-liquid-reaction zone (8) adapted to provide for replenishing said bath by said solid charge materials.
19. An apparatus as claimed in claim 18 wherein said means for
conveying and downwardly projecting said charge materials includes a
pneumatic solids injection lance (34) cantilevered longitudinally into said
hot gas stream along said gas-solid-liquid reaction zone with an exit nozzle (35) of said lance (34) directed downwardly adapted for injecting said solid charge materials into said partially melted metal bath (7); and
means for said traversing comprises a reversing lance drive (39) adapted for stroking said lance (34) successively backwards and forwards along said traverse span.
20. An apparatus as claimed in claim 18 wherein said means for
conveying and downwardly projecting said charge materials includes an
oscillating conveyor (24) cantilevered longitudinally into said hot gas
stream (15) along said gas-solid-liquid reaction zone with a discharge lip
(25) of said conveyor (24) adapted for dropping said solid charge
materials downwards into said partially melted metal bath(7).
21. An apparatus as claimed in claim 18 wherein said means for
traversing comprises a reversing lance drive (39) adapted for stroking
said lance successively backwards and forwards along a lance-fed
portion of said traverse span; also includes an oscillating conveyor (24)
cantilevered longitudinally into said hot gas stream (15) along said gas-
solid-liquid reaction zone (8) with a discharge lip (25) of said conveyor
(24) adapted for dropping said solid charge materials downwards into
said partially melted metal bath (7), and
said traversing comprises a reversing conveyor drive (31) adapted for stroking said oscillating conveyor successively backwards and forwards along a conveyor-fed portion of said traverse span.
22. An apparatus as claimed in claim 21 wherein said lance-fed
portion overlaps said conveyor-fed portion of said traverse span across a
common traverse span portion of said longitudinal traverse span,
including traverse coordinating means adapted to control the travel cycle
time intervals and position of said lance nozzle relative to said discharge lip during traversing thereby avoiding crossing over between charge materials issuing from said lance nozzle and those issuing from said discharge lip across said common traverse span during traversing.
23. An apparatus as claimed in claim 18,19,20 or 21 including means
for maintaining a gas-liquid reaction zone (10) carrying substantially only
hot liquid metal and slag adjoining said gas-solid-liquid reaction zone (8)
within said furnace (1);
means for introducing fuel and oxygen adapted for heating and regulating the metal temperature in said gas-liquid reaction zone (10) by combustion and forming said hot gas stream (15);
means for effecting general flow of said hot gas stream (15) countercurrent to the general movement of materials into and through said gas-solid-liquid reaction zone (8) and exhausting said hot gas stream (15) through an adjoining annular end opening (4) of said furnace, and
means for discharging hot liquid metal (9) from said gas-liquid reaction zone (10).
24. An apparatus as claimed in claim 18 comprising:
a vacuum vessel (20) carried adjacent to one of said annular end openings (5) having a siphon-tube (19) with its outlet connected into said vessel (20) and its inlet adapted for insertion through said end opening (5) into the liquid metal (9) within said furnace (1);
means for evacuation and for maintaining a controlled vacuum pressure within said vessel causing liquid metal flow through said suction tube (18) adapted for forming and maintaining a liquid metal column (68) within said vessel;
a lateral channel enclosure (71) communicating with said metal column (68) adapted to carry a post treatment pool of metal (70) flowing out from said column (68) under a pressure higher than said controlled vacuum pressure; and
means for discharging said liquid metal from said post-treatment pool (70) having a submerged nozzle (73) equipped with a throttling valve (74) for regulating the rate of discharging of said metal; and
an overflow lip from said channel enclosure (71), which also includes means for throttling of said flow through said suction tube (19).
25. An apparatus as claimed in claim 24 including means for post-
treatment gas supply (75, 75) adapted to introduce treatment gases into
the metal flowing within said pool (70).
26. An apparatus as claimed in claim 24 wherein said channel
enclosure (71) includes baffles (77) adapted to increase the total distance
traveled by liquid metal between entry from said column (68) and the exit
of said discharging.
27. An apparatus as claimed in claim 24, 25 and 26 wherein said
pressure higher than said controlled vacuum pressure comprises
substantially atmospheric pressure.
28. An apparatus as claimed in claim 24,25 26 and 27having means
for sealing of said lateral channel enclosure (71) adapted for excluding
access of air to the surface (72) of said post treatment pool (70).
29. An apparatus as claimed in claim 23 having an annular dam (63)
proximate the junction between said gas-solid-liquid (8) and gas-liquid
(10) reaction zones which extends radially inwards from the inner side
walls of rotary furnace (1) to an annular dam crest (91) with an invert at
a level higher than the surface of the layer of slag (11) during the full rotation of the furnace, thereby being adapted to obstruct the longitudinal transfer of slag (11) between said two zones (8,10).
30. An apparatus as claimed in claim 29 wherein said dam (63)
includes at least one channel (65) communicating longitudinally through
said dam (63) with a dam channel entrance opening (81) out of said gas-
solid-liquid reaction zone and a dam channel exit opening (82) into said
gas-liquid reaction zone (10), adapted to allow said liquid metal exit from
said gas-solid-liquid reaction zone (8).
31. An apparatus as claimed in claim 30 wherein said channel (65) is
sloped upwards in the general direction radially towards the furnace axis
of rotation of furnace (1), reaching a crest (86) within said channel (65)
wherein the invert of said crest (86) is at a higher elevation than the
elevation of the top of said dasm channel entrance opening (81) during
the portions of each revolution of said furnace when said top is passing
through said layer of slag (11), said crest (86) thereby being adapted to
substantially block transfer of slag from said gas-solid-liquid reaction
zone (8) into said gas-liquid reaction zone (10) through said channel (65)
during operation.
32. An apparatus as claimed in claim 31 wherein said crest (86) is
intermediate between said entrance opening (81) and said exit opening
(82), thereby being adapted to block transfer of slag in either direction
between said gas-solid-liquid (8) and gas-liquid reaction zone (10).
33. An apparatus as claimed in claim 18 having an exhaust gas
recirculation duct (92) adapted for transferring a portion of the hot
furnace gases exhausted from annular end opening (4) and re-
introducing them into furnace (1) through the other end opening (5),
thereby recirculating said portion of the exhaust gases to mix with and comprise a portion of said hot gas stream (15) and discharging only the remaining exhaust gases (99).

Documents:

in-pct-2000-436-del-abstract.pdf

in-pct-2000-436-del-claims.pdf

in-pct-2000-436-del-correspondence-others.pdf

in-pct-2000-436-del-correspondence-po.pdf

in-pct-2000-436-del-description (complete).pdf

in-pct-2000-436-del-drawings.pdf

in-pct-2000-436-del-form-1.pdf

in-pct-2000-436-del-form-13.pdf

in-pct-2000-436-del-form-19.pdf

in-pct-2000-436-del-form-2.pdf

in-pct-2000-436-del-form-3.pdf

in-pct-2000-436-del-form-5.pdf

in-pct-2000-436-del-gpa.pdf

in-pct-2000-436-del-pct-210.pdf

in-pct-2000-436-del-pct-304.pdf

in-pct-2000-436-del-pct-331.pdf

in-pct-2000-436-del-pct-409.pdf

« Previous Patent

Next Patent »

Patent Number

227626

Indian Patent Application Number

IN/PCT/2000/00436/DEL

PG Journal Number

05/2009

Publication Date

30-Jan-2009

Grant Date

14-Jan-2009

Date of Filing

18-Dec-2000

Name of Patentee

WILLIAM LYON SHERWOOD

Applicant Address

2 TAMATH CRESCENT, VANCOUVER, BRITISH COLUMBIA V6N 2C9, CANADA.

Inventors:

#	Inventor's Name	Inventor's Address
1	WILLIAM LYON SHERWOOD	2 TAMATH CRESCENT, VANCOUVER, BRITISH COLUMBIA V6N 2C9, CANADA.

PCT International Classification Number

C21B 13/08

PCT International Application Number

PCT/CA99/00456

PCT International Filing date

1999-05-19

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	60/085,934	1998-05-19	U.S.A.