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(11) | EP 0 071 359 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Methods and apparatus for molten metal fume supression |
| (57) Methods and apparatus for the suppression of fume from a body of molten metal is
described. One method involves blanketing the molten metal bath with a mixture of
pressurized inert gas and finely divided or atomized particles of water. The inert
gas may be argon, nitrogen or steam. An apparatus for carrying out this method comprises
an array of nozzles supported adjacent the mouth of a receiver vessel and connected
to sources of the inert gas and water. Another method entails burning fuel in the immediate vicinity of the molten metal surface to consume and/or displace ambient air thereby to starve the bath of oxygen and, concomitantly, to suppress the formation of the fume-producing metallic oxide. An apparatus for carrying out this method, particularly adapted for suppressing fume generated in the flow of molten metal through the runner system of a blast furnace cast house, includes a burner from which fuel and air in predetermined amounts are discharged to create flame and disperse it along the axis of the runners. The flame operates to consume ambient air in the combustion process thereby to starve the region over the metal streams of oxygen that would otherwise combine with metal vapors to create fume-producing metallic oxides. |
[0002] When molten metals are poured from one container to another in various metal production processes, the pouring is accompanied by the emission from the receiving container of large amounts of fume. One typical example is the transfer of refined steel into a receiving ladle upon tapping of the converter or steelmaking furnace.
[0003] The generation of such fugitive emissions constitutes a serious atmospheric pollution problem associated with many metallurgical processes, the abatement of which represents a significant part of the cost of performing these processes. Much effort and expense has been expended in the development of emission control systems that are effective to maintain the volume of fugitive emissions within acceptable limits. These efforts are exemplified by the arrangement of various forms of air or gas curtains and fume exhaust equipment to isolate the affected region of the plant and to conduct the undesirable effluent to treating apparatus prior to its discharge into the atmosphere. Such systems are exemplified by United States Patents Nos. 3,396,954, 3,834,293 and 3,994,210. These systems all rely on the capture and disposal of the fugitive fume and, while being effective to a limited degree in solving the concerned problem, entail significant capital expenditure to install and are costly to operate.
[0004] In Japanese Patent No. 53-6602, granted March 9, 1978 to Nippon Steel Corporation, on the other hand, is described an emission control system by means of which fugitive fume is controlled by spraying an inert gas, typically steam or nitrogen, into the molten metal receiver. Spraying is achieved by an ejector ring that is suspended into the vessel to position it closely above the level of the molten bath. The ring is suspended by a hoist that enables the ring to be raised as the bath level rises thereby to maintain a relatively constant spacing between the ejector ring and the bath surface.
[0005] Although this gas ejector of the Japanese patent is an improvement over prior art devices of the aforementioned type in that it is effective to suppress to a limited extent the formation of fume, its use is not totally dispositive of the problem. Firstly, the ejection of steam or nitrogen onto a molten bath has been found to be not, by itself, capable of suppressing the generation of fume to an acceptable level. Tests conducted by applicants indicate that fume suppression in this manner is only about seventy percent effective. Secondly, the need to maintain the ejector ring closely adjacent the level of the bath subjects the equipment to the possibility of damage due to the extremely high temperature environment in which it is used and to the danger of contacting the bath itself or being impinged upon by splashing metal which plugs the gas ejection ports thereby to rapidly render the ring inoperative.
[0006] Belgian Patent No. 889,880 issued December 1, 1981 describes a fume suppression system suitable for use on the pouring trough and runner system of a blast furnace cast house. According to the teachings of this patent, the pouring trough and the iron and slag runners are covered by various devices including mechanical covers, blankets of inert gas, and other elements in order to isolate the molten streams flowing therein from ambient air. The use of such devices, however, are not completely desirable for various reasons. Mechanical covers suitable for this use are large, heavy members that require frequent removal and replacement. This need to frequently move the covers is costly in the time and effort involved. The need to frequently repair and/or replace the covers represents a significant operating expense. Moreover, such movement of the covers disturbs the seal required between the cover edges and the runners thereby creating a danger of air leakage at the respective interfaces between the covers and the runners which renders the system ineffective. Additionally, the provision of inert gas ejector manifolds over the length of the runners, besides being subject to damage caused by excessive heating, are also prone to failure due to molten metal splattering that, over time, causes the ejector opening to plug.
[0007] It is to the amelioration of the above problems and toward the provision of a more suitable molten metal fume suppression apparatus that the present invention is directed.
[0008] According to the present invention, there is provided a method of suppressing the emission of fume from a vessel containing a molten metal bath exposed to the atmosphere, wherein an inert gas is supplied to the vessel above the surface of the bath, characterised in that a mixture of the inert gas and atomised water is ejected into the vessel to form a blanket above the surface of the bath therein sufficient substantially to prevent atmospheric air from combining with the metal of the bath.
[0009] The invention also provides an apparatus for suppressing the emission of fugitive fume from a vessel for receiving a stream of molten metal, comprising a frame, means for supporting said frame, and fluid ejector means affixed to said frame, characterised in that the support means is adapted to support the frame adjacent the mouth of the vessel, and the ejector means is adapted to eject a mixture of inert gas and atomized water into said vessel to form a blanket above the surface of the body of molten metal therein.
[0010] The invention further provides a method of suppressing the emission of fume from a receiver into or along which molten metal is transferred, characterised in that fuel is injected into the receiver and burned in the vicinity of the surface of the molten metal therein.
[0011] The invention still further provides an apparatus for suppressing the emission of fume from an open receiver into or along which molten metal is transferred, characterised by a fluid fuel burner for positioning in close superposed relation to the surface of the metal in said receiver, said burner including means for discharging fluid fuel into said receiver against the surface of the molten metal therein and in amounts sufficient to combine with ambient air in the region of said surface for combustion.
[0012] The invention is further described, by way of example, with reference to the accompanying drawings, in which:-
Figure 1 is an arrangement drawing illustrating one form of fume suppression device according to the present invention operatively disposed with respect to a molten metal receiving vessel;
Figure 2 is a side elevational view in enlarged scale of the fume suppression device illustrated in Figure 1;
Figure 3 is a plan view of the device of Figure 2;
Figure 4 is a front elevational view of the device of Figure 2;
Figure 5 is a sectional view taken at the nexus between the water line and one gas line in the device of Figure 2;
Figure 6 is an enlarged view taken along line 6-6 of Figure 4;
Figure 7 is a plan view of another form of fume suppression apparatus according to the present invention;
Figure 8 is an elevational view, partly in section of the device of Figure 7;
Figure 9 is a view taken along line 9-9 of Figure 8;
Figure 10 is a front elevational view of yet another form of fume suppression apparatus according to the invention;
Figure 11 is a side view partly in section of the apparatus of Figure 10;
Figure 12 is a somewhat schematic arrangement drawing illustrating another apparatus according to the present invention for suppressing fume in a molten metal receiving vessel;
Figure 13 is an enlarged partial plan view of the arrangement shown in Figure 12;
Figure 14 is an elevational view of the arrangement of Figure 13;
Figure 15 is a sectional view taken along line 15-15 of Figure 14;
Figure 16 is a sectional view similar to Figure 15 illustrating alternative apparatus for use in the practice of the invention;
Figure 17 is a sectional view taken along line 17-17 of Figure 16;
Figure 18 is a schematic representation of a blast furnace runner system incorporating fume suppression apparatus of the present invention;
Figure 19 is an elevational section taken along line 19-19 of Figure 18;
Figure 20 is an enlarged view of a burner taken along line 20-20 of Figure 19; and
Figure 21 is an end view of the burner of Figure 20.
[0013] Referring to figure 1, a vessel 10, commonly referred to as a tapping ladle, receives molten metal from the discharge spout 11 of an open hearth furnace, indicated schematically at 12. It should be understood, however, that the invention is equally applicable to other metal-pouring applications.
[0014] As is well known, the pouring of metal into tapping ladles in steel- and other metal-pouring operations is normally accompanied by the generation of excessive amounts of fume that essentially comprise finely divided iron oxide and dust particles mixed with gaseous contaminants, which, if discharged to the atmosphere, present a serious pollution problem.
[0015] In order to abate this problem, in the arrangement of Figure 1 there is provided fume suppression apparatus 14 suspended from an overhead support 15 in overlying relation to the mouth 16 of the vessel 10. The apparatus 14, as shown in Figure 2, includes a frame structure 18 comprising welded tubular members defining an annular manifold 20 and a pair of gas inlet lines 22, here shown as steam lines, the inlet ends 24 of each of which connect with a source of steam at an elevated pressure and the outlet ends 26 of which communicate with the manifold at diametrically spaced points thereabout. The lines 22 may be laterally stiffened by a brace 28 that also serves to mount one of a plurality of mutually spaced lifting lugs 29 for suspending the apparatus. The other lugs 29 may be as shown weldedly attached to the manifold 20. Pressurized water is delivered to each of the lines 22 from a supply line 30 that connects at its inlet end 32 to a source. The outlet end of the line 30 is formed as a T-member 34, the discharge ends 36 of which communicate with each of the steam lines 22.
[0016] Communication between the ends 36 of the T-member 34 and the steam lines 22 is effected as shown in Figure 5 by short lenghts of tubing 38 that penetrate the wall of the respective steam lines at an angle acute in the direction of steam flow. In this way pressurized water emerging from the tubes 38 is atomized by the steam into finely divided particles and the mixture delivered to the manifold 20 for ejection from a plurality of ejector nozzles 40 whose discharge openings are directed into the interior of the vessel 10.
[0017] Nozzles 40 are disposed in circumferentially spaced array about the manifold 20 and connect thereto by means of depending extensions 42. An additional pair of nozzles 40 may be provided at spaced locations along a line extending diametrically across the mouth of the vessel 10 defined by a crossover tube 44.
[0018] It has been found that flat fan nozzles similar to those identified as Sprayco Model No. 25101526 are functionally effective for use as the nozzles 40. These apparatus have a discharge opening 46 enclosed within an oval recess 47 that serves as a baffle to produce a divergent spray pattern in the ejected mixture that effectively blankets the full surface of the metal bath within,the vessel 10 that may reside anywhere from 14 to 0 feet (4.3 to 0 metres) below the vessel mouth.
[0019] In a typical installation for suppressing fume from an open hearth tapping ladle of 350-ton(320-tonne) (4 metres) capacity whose mouth is approximately 13 feetLin diameter apparatus 14 of the described type having an effective (0.9 metres) manifold diameter of about three feetLis suspended about (0.6 metres) 2 feet/above the ladle mouth in substantial concentric relation with the vertical axis thereof. In this position the apparatus 14 is about the furnace trough 11 so as to be removed from danger of contact with the molten metal pour stream from the trough to the ladle 10. At, or just prior to, the commencement of the furnace tap steam at a temperature of between 470°F to (243°C to 260°C) (1.10 to 1.24MPa) 500°F (243°C to 260°C) and a pressure of between 160 psig and 180 psig (1.10 to 1.24MPa) is admitted to the lines 22 at a rate of about 10,000 (4,500 to 5,400 kg) to 12,000 pounds/per hour. Simultaneously therewith water at about 150 psig (1.04 MPAa) at the rate of 40 to 60 gallons (152 to 228 litres) per minute is supplied to the water line 30 from whence it is ejected via tubes 38 into the respective steam lines to be atomized and directed from the discharge openings 46 of nozzles 40 in a divergent pattern to blanket the surface of the molten metal bath.
[0020] It has been found that by blanketing the bath by means of an ejected mixture of steam and atomized water particles fume suppression between 99% and 100% effectiveness can be obtained. The physical characteristics of the steam and water components of the mixture may be altered depending on the size and capacity of the vessel containing the bath to be blanketed. Also, other non-oxidizing gases such as nitrogen or argon may be employed as the atomizing medium.
[0021] Figures 7 through 9 of the drawing illustrate another operative, though somewhat less desirable, embodiment of the invention. In this embodiment fume suppression apparatus, indicated generally as 14', comprises a frame structure 50 including a centrally disposed closed manifold 52 whose interior is divided by a horizontal partition 54 into vertically spaced water and steam compartments, 56 and 58 respectively. A pair of parallelly extending tubular supply lines comprising water supply line 60 and steam supply line 62 serve to deliver the fluid mixture components to the respective compartments 56 and 58, line 60 having its inlet end 64 connecting with a source of pressurized water and its discharge end 66 communicating with the manifold water compartment 56 while line 62 has its inlet end 68 similarly connected to a source of pressurized steam and its discharge end 70 in communication with the manifold steam compartment 58. Lines 60 and 62 are appropriately braced by support bars 72, one or more of which may mount a suspension lug 74 for suspending the. apparatus above the receiving vessel 10.
[0022] Emanating from the manifold 52 are radially extending legs 76, each comprising a water tube 78 and a steam tube 80, the inlet ends of each communicate with the appropriate compartment 56 or 58 of the manifold and the free ends of which are closed. Extending be- . tween and connecting the tubes 78 and 80 adjacent their free ends are feeder lines 82 and 84 that connect with opposite sides of an ejector nozzle 86. Unions 88 are provided in the feeder lines to facilitate replacement of the nozzles should such become necessary. Chordal braces 90 are advantageously welded between adjacent legs in order to stiffen the structure while an additional set of feeder lines 92 and 94 may be provided to connect another course of nozzles 86 on alternate spacing with the first course and radially inwardly therefrom.
[0023] Nozzles 86 in the described apparatus are of the type produced by Spraying Systems Co. under Model No. IJ-SUE-175B which, as shown in Figure 9, have a centrally disposed water discharge opening 96 surrounded by a plurality of smaller diameter steam discharge openings 98. Appropriate passages within the body of nozzles 86 connect the respective openings with the steam and water lines 82 and 84 respectively.
[0024] In practice the operation of this embodiment of the invention is substantially identical to that described above, the difference being that water atomization occurs externally of the nozzles 86 and, accordingly, apparatus 14' having an effective diameter camparable to that of the ladle mouth, is utilized for effective blanketing of the molten metal bath.
[0025] In the described arrangement extended spacing as at 100 may be provided between a pair of adjacent legs 76 to accommodate access of the furnace trough when the apparatus is positioned in close proximity to the ladle mouth.
[0026] Figures 10 and 11 illustrate yet another alternative form of apparatus adapted for the practice of the present invention. This apparatus, indicated generally as 14", comprises a gas line 102 of somewhat enlarged diameter angularly offset to define a generally horizontal leg 104 and a vertical leg 106. A lifting lug 108 connects with the horizontal leg for suspending the apparatus above a receiver vessel (not shown). At its free or inlet end 110 the leg 104 is adapted for connection to a pressurized gas source, contemplated primarily to be steam. A water line 112 adapted at 114 for connection to a source of pressurized water penetrates the leg 104 immediately downstream of the inlet end 110 and is angularly offset to dispose its discharge end in the form of a spray nozzle 116 substantially on the axis of the leg. Water issuing from the nozzle 116 is atomized by the gas admitted to the line 102 in a manner similar to that described above and the mixture delivered for discharge from the downwardly directed outlet 118.
[0027] Outlet 118 includes a conically formed divergent head 120 adapted to receive a baffle cone 122. The baffle cone 122 is mounted within the head 120 with its peripheral surface spaced from the facing surface of the head as at 124 to provide an annular discharge opening capable of producing a divergent spray in a hollow conical pattern. The cone 122 is adjustably mounted within the head by means of a support stud 126 having a threaded lower end 128 and an upper end weldedly attached to a diametric mounting plate 130 fixed to the leg 106. Attachment of the cone to the stud is effected by an adjustable nut 132. The cone 122 may be provided with a handle 134 to facilitate its manipulation during setup.
[0028] The operation of this alternative form of the inventive apparatus is substantially the same as those described hereinabove except that, due to the production of a hollow conical spray the apparatus 14" is positioned to direct the spray pattern such that it wipes the interior wall of the ladle. In this way a blanketing envelope is produced above the molten metal bath capable of preventing the entry of oxygen into the affected region and thereby to prevent the generation of fume.
[0029] Referring now to Figure 12, there is provided fume suppression apparatus 216 suspended by lugs 217 attaching chains 218 from an overhead support 219 in overlying relation to the mouth 220 of a vessel 210. The apparatus 216 comprises a plurality of burners 222, here shown as being four in number arranged on ninety degree spacing, depending from a horizontally disposed elongated header assembly including parallel fuel and air headers 224 and 226 respectively. The headers 224 and 226 are formed by three serially connected legs defining a generally C-shaped member. The open side of the assembly conveniently accommodates the molten metal stream issuing from the discharge spout 212 of furnace 214. The fuel and air headers 224 and 226 are capped, as at 228 and 230, at their respective leading ends and at their trailing ends connect through risers 232 and 234 containing regulating valves 236 and 238 to sources of fuel and compressed air respectively. It is contemplated that any fluid fuel may be utilized in the operation of the apparatus, however, gaseous fuels such as natural gas and gases obtained as by-products from the operation of coke ovens and blast furnaces may be advantageously employed.
[0030] As shown in Figures 14 and 15, each burner apparatus 222 comprises concentrically disposed fuel and air supply tubes 240 and 242, that communicate at one end each with the fuel header 224 and air header 226, respectively. The fuel supply tube 240 surrounds the discharge end of air supply tube 242 such that air discharged under pressure from header 226 serves to inspirate fuel from the header 228 and mix therewith in the fuel supply tube 240 prior to ejection from the discharge end thereof into the interior of the vessel 210 for burning therein.
[0031] In an operative installation fuel in the form (55kPa) of natural gas, at a line pressure of about eight psi, (62tkPa) and compressed at a line pressure of about ninety psi/are supplied to the burners 222 for ejection into the interior of the vessel 210 as molten metal is poured therein. Gas and air are ejected from the burners 222 at a rate to insure the delivery of fuel and combustion thereof at least in close proximity to the surface of the molten bath that develops in the bottom of the vessel 210.
[0032] Although the mechanism by which suppression of fume is accomplished is not completely understood, it is believed that the effect is largely accomplished by the expurgation of ambient air from that region of the vessel interior immediately adjacent the bath thereby preventing oxygen-contact with the molten metal. Expurgation of air may be accomplished by the combustion gases produced by the burning fuel physically displacing the air from the vicinity of the bath. Alternatively, it is believed than an oxygen-free atmosphere adjacent the molten metal bath may be achieved by the fuel's consuming the ambient air during combustion. Whatever the reason the generation of a flame within the receiver has a very substantial effect on suppressing fume that is otherwise attendant in the pouring of molten metal.
[0033] In achieving the above advantageous results, it is further believed that the function of the compressed air is simply to provide a vehicle or carrier for delivering the fuel gas to the surface of the bath. This may be borne out by the fact that the supply of compressed air to the burners 222 can be reduced in response to the rising level of metal in the bath as pouring proceeds without adversely affecting fume suppression.
[0034] Not suprisingly, therefore, where adequate fuel pressures, for example, of the order of about (104 kPa) fifteen psi/are available, the advantageous results of the invention have been achieved by the introduction of gaseous fuel without compressed air to the receiver. Thus, in Figures 16 and 17 is shown an alternative form of burner apparatus indicated as 222', capable of producing results similar to those achieved from use of the burners 222 of Figures 12 through 15. In this form of the invention, fuel from the fuel header 224' is discharged via supply tubes 240' into the vessel interior as molten metal is supplied thereto. As shown, the discharge ends of the supply tubes 240' may each be advantageously enclosed by a cylindrical sleeve 244 that is concentrically spaced from the tube by radially extending ribs 246 to define an annular space through which ambient air about the respective burners 222' can be aspirated into the gas flow stream for mixing therewith in order to promote combustion and to extend the flame produced thereby into the vessel interior.
[0035] Figure 18 illustrates schematically a system 310 of runners 312 for conducting molten metal from a process furnace, typically a blast furnace (not shown), to receiver ladles 314, for which the fume suppression apparatus of the present invention is particularly adapted for application. Only so much of the molten metal processing system is shown as is necessary for an understanding of the invention. Not shown is the furnace trough which discharges the molten burden from the furnace into the runner system or the skimmer and slag runner system that operates to segregate the pig iron product conducted by the runners 312 from the slag which, as is well known, is a by-product of the production process. It should be understood however, that the apparatus described herein is equally adaptable for application to a blast furnace trough and to the slag runners as well as to any other elongated conductor of molten metal from which oxide fume may emanate. Removable gates 316 as shown in Figure 18 enable the discharge of molten pig iron from the furnace sequentially into the ladles 314, indicated as A, B & C, respectively.
[0036] As is well known, the flow of molten metal from a blast furnace, or the like, along a runner system is accompanied by the generation of undesirable oxide fume from the surface of the flowing metal. Such fume comprises essentially finely divided oxide particles of the metal being conducted through the runners and creates a polluting atmosphere in the surrounding area. A comprehensive description of the mechanism involved in the generation of fume from systems of the type described herein is contained in the paper, "The Formation of Iron Oxide Fume", by E. T. Turkdogan, et al., Journal of Metals, July 1962.
[0037] Fuel burner assemblies, identified respectively as 318 in the drawings, are disposed at longitudinally spaced locations along the runner system. As best shown in Figures 19, 20 and 21 each of these burner assemblies -318 comprises a burner head 320 adapted to be disposed in close, overlying relation to the molten bath 322 flowing in the runners 312. The burner head 320 is conveniently formed of a horizontally extending, generally cylindrical member defining a cylindrical, open ended mixing chamber 324 having concave, downwardly directed baffle structures 326 emanating from each end thereof. A fuel supply pipe 328 is weldedly connected to the head 320 with its discharge end communicating with the mixing chamber 324. The other end of the supply pipe 328 is connected via shutoff valve 330 and a flow regulator 332 with a source 333 of gaseous fuel, preferably natural gas. In the arrangement illustrated in Figure 19, a flexible hose 334 is provided between the regulator 332 and the pipe 328 in order to accommodate pivotal displacement of the burner assembly 318 away from the runner 312 as hereinafter described.
[0038] Within the mixing chamber 324 is positioned a T-shaped fitting 336 adapted for the axial discharge of pressurized air along the burner head 320. As shown, the fitting 336 is open at both ends and is disposed in substantial concentrically spaced relation to the interior wall of the mixing chamber 324 adjacent the discharge end of the fuel supply pipe 328. Air under pressure is supplied to the fitting 336 through air supply pipe 338 and line 340, the latter being connected to the former via reducing fitting 342. As shown, the line 340 penetrates the burner head 320 to connect with the upstanding opening of the T-fitting 336. The other end of the air supply pipe 338 connects with a source 344 of pressurized air through shut-off valve 346 and flow regulator 348. A flexible hose 350, similar to hose 334, connects the pipe 338 with the regulator 348 in order to accommodate pivotal movement of the burner assembly 318.
[0039] In erecting the burner assembly 318, the supply pipes 328 and 338 are parallelly disposed and connected by braces or brackets 352 in order to be moved in unison from the assembly's operative position over the runner 312. This is desirable in order to have unobstructed access to the runner for its maintenance or repair. Pivoting of the assembly 318 is accomplished in the described apparatus by mounting the ends of the supply pipes 328 and 338 opposite the burner head 320 on a pad 354 laterally removed from the runner 312 by means of swivel unions 356, 358.
[0040] With the burner assemblies 318 disposed over the runners 312 as shown in the solid lines in Figure 19 and prior to the flow of molten metal through the runner system, fuel is admitted to all of the burners in amounts just sufficient to sustain a flame, the ignition of which is obtained by igniter apparatus (not shown). Thereafter, as molten metal is discharged from the blast furnace into the runner system, pressurized air is admitted to each burner assembly in sequence so as to increase the intensity of the flame and exple it outwardly from both ends of the respective burner heads 320 over the adjacent region of the runners 312. It has been determined that with fuel in the form of (55kPa) natural gas available at pressures of up to 8 psi (55KPa) and air available at pressures from 70 to 90 psi flame can be expelled from each burner assemblv approximately (2.1 to 2.4 metres) seven to eight feet from each end of the mixing chamber 324 thereby permitting fume suppression along the entire runner system with burner assemblies disposed on approximately fifteen feet spacing.
[0041] It will be appreciated that the flame with unconsumed gas that is expelled over the runner system is operative to combine with the ambient air within the runners 312 thereby consuming the air and starving the metal vapors of available oxygen from which to generate metallic oxides and, concomitantly, in this way, the oxide fumes that would otherwise emerge from the surface of metal flowing along the runners is suppressed.
[0042] It should further be appreciated that although the apparatus is described in connection with use over the metal-conducting runners in a blast furnace cast house, such apparatus has comparable utility when disposed over a blast furnace trough which conducts the molten burden, upon tapping, from the furnace to the runners. The apparatus may also be utilized over slag runners that conduct slag separated from the material discharged from the trough to disposal.
[0043] From the foregoing, it should be appreciated that the hereindescribed invention affords a simple, yet effective means for abating a serious pollution problem that exists substantially everywhere that molten metal is poured from a source to a receiver. The apparatus required for practice of the invention is, moreover, inexpensive to install and to operate as compared with prior art apparatus previously employed for the purpose of abating pollution attendant with molten metal pouring.
1. A method of suppressing the emission of fume from a vessel containing a molten
metal bath exposed to the atmosphere, wherein an inert gas is supplied to the vessel
above the surface of the bath, characterised in that a mixture of the inert gas and
atomised water is ejected into the vessel to form a blanket above the surface of the
bath therein sufficient substantially to prevent atmospheric air from combining with
the metal of the bath.
2. A method according to claim 1, wherein the water is atomized by the inert gas.
3. A method according to claim 1 or 2, wherein the mixture is ejected into the vessel
from a level not substantially below the mouth of said vessel.
4. A method according to claim 3, in which said mixture is ejected in the form of
divergent sprays from a plurality of sources disposed in spaced array about the mouth
of the vessel.
5. A method according to any one of claims 1 to 4, wherein said inert gas is steam.
6. A method according to any one of claims 1 to 4, wherein said inert gas is nitrogen.
7. A method according to any one of claims 1 to 4, wherein said inert gas is argon.
8. An apparatus for suppressing the emission of fugitive fume from a vessel (10) for
receiving a stream of molten metal, comprising a frame (18;50), means (15) for supporting
said frame, and fluid ejector means (40;86) affixed to said frame, characterised in
that the support means (15) is adapted to support the frame (18;50) adjacent the mouth
of the vessel, and the ejector means (40;86) is adapted to eject a mixture of inert
gas and atomized water into said vessel to form a blanket above the surface of the
body of molten metal therein.
9. An apparatus according to claim 8, wherein said fluid ejector means includes a
plurality of nozzles (40;86) capable of delivering divergent spray streams of a mixture
of the inert gas and water admitted thereto, and disposed in spaced array about the
vessel mouth.
10. An apparatus according to claim 9, wherein said frame includes hollow, fluid conducting
members (78,80) some of which conduct inert gas and others of which conduct water,
and means (78,80) for connecting one each of said gas conducting members and said
water conducting members to each of said nozzles (86).
11. An apparatus according to claim 10, wherein each of said nozzles comprises a water
discharge opening (96) in fluid communication with said water conducting member (78)
and a gas discharge opening (98) in fluid communication with said gas conducting member
(80), said gas discharge opening being so positioned relative to the water discharge
opening as to atomize the water discharged therefrom.
12. An apparatus according to claim 11, wherein each of said nozzles comprises at
its discharge end a substantially centrally disposed water discharge opening (96)
and a plurality. of gas discharge openings (98) circumferentially spaced about said
water discharge opening.
13. An apparatus according to claim 10, wherein the frame includes a centrally disposed
manifold (52), a partition (54) in said manifold dividing the same into a water compartment
(56) and a gas compartment (58), at least one leg (76) emanating from said manifold
including a tubular water line (78) connecting with said water compartment and a tubular
gas line (80) connecting with said gas compartment, and a nozzle (86) interposed between
said water line (78) and said gas line (80) containing water and gas flow passages
connecting each with said water line and said gas line respectively.
14. An apparatus according to claim 9, wherein the frame includes hollow, fluid conducting
members forming an annular header (20), said nozzles (40) connecting with said header
at circumferentially spaced locations thereabout, means (34-38) upstream of said header
for mixing inert gas and water, and means (22) for delivering the gas/water mixture
to said header.
15. An apparatus according to claim 14, wherein said frame includes at least one gas
line (22) connecting with said manifold, a water line (30,34) for delivering water
to said gas line, and a water atomizing nozzle (38) at the nexus between said water
line and said gas line.
16. An apparatus according to claim 8, wherein said frame comprises a gas line (102),
and water ejector means (116) communicating with the interior of said gas line, said
gas line having an outlet (118) defined by a divergent conical head (120), and a conical
body (122) being disposed within said head with the peripheral surface thereof spaced
from the facing surface of said head to define an annular discharge opening (124).
17. An apparatus according to claim 16, wherein said conical body (122) is adjustably
mounted within said head (120) to vary the size of said discharge opening (124).
18. An apparatus according to claim 17, wherein said outlet (118) from said gas line
includes a concentric, fixedly mounted stud (126) with a threaded lower end (128),
the stud extending through an opening in said conical body and receiving a threaded
connector to retain said body adjustably thereon.
19. A method of suppressing the emission of fume from a receiver into or along which
molten metal is transferred, characterised in that fuel is injected into the receiver
and burned in the vicinity of the surface of the molten metal therein.
20. A method according to claim 19, wherein the injected fuel is a fluid.
21. A method according to claim 20, wherein said injected fuel is gaseous.
22. A method according to any one of claims 19 to 21, wherein said fuel is injected
into said receiver into wiping relation with the surface of the molten metal therein.
23. A method according to claim 22, wherein the fuel is injected into said receiver
from a pressurized source.
24. A method according to any one of claims 19 to 22, wherein the fuel is injected
into a stream of compressed air for delivery to an operative level in said receiver.
25. A method according to claim 24 in which the mixture of fuel and air injected into
said receiver contains no more than a stoichiometric amount of oxygen.
26. A method according to claim 25 in which said mixture of fuel and air is fuel-rich.
27. A method of suppressing the emission of fume from a receiver vessel into which
molten metal is transferred, characterised in that at least one burner is mounted
over the mouth of the vessel for combusting fuel and pressurized air supplied thereto,
fuel and air are supplied simultaneously to said burner as molten metal is poured
into said vessel, and gradually reducing the supply of air to said burner as the level
of molten metal rises in said vessel.
28. An apparatus for suppressing the emission of fume from an open receiver (210;312)
into or along which molten metal is transferred, characterised by a fluid fuel burner
(222) for positioning in close superposed relation to the surface of the metal in
said receiver, said burner including means (240;336) for discharging fluid fuel into
said receiver against the surface of the molten metal therein and in amounts sufficient
to combine with ambient air in the region of said surface for combustion.
29. An apparatus according to claim 28, wherein said burner includes means (242;336)
for dispersing said fluid fuel in an expansive pattern to cover an extended region
over said surface.
30. An apparatus according to claim 29 in which said fuel-dispersing means comprises
means (242;336) for discharging air under pressure in intimate relation with the discharged
fuel.
31. An apparatus according to claim 30 wherein said burner is adapted for combustion
of gaseous fuel.
32. An apparatus according to claim 30, wherein said burner (320) comprises an elongated
burner head defining a baffle structure (326) substantially open in facing relation
to the surface of said molten bath and a mixing chamber (324) intermediate the ends
of said baffle structure, a fuel supply pipe (328) communicating with said mixing
chamber (324), and means (336) within said mixing chamber for dispersing fuel longitudinally
of said baffle structure, said means including means (336) for discharging pressurized
air into intimate, mixing relation with said fuel and for directing the same longitudinally
of said baffle structure (326).
33. An apparatus according to claim 32, wherein said burner head comprises a generally
cylindrical mixing chamber (324) open at its ends and said baffle structure includes
downwardly directed arcuate plates (326) emanating from each end of said mixing chamber,
said fuel supply pipe (328) being attached to said burner head in communication with
said mixing chamber (324) and said fuel dispersing means (336) having a T-shaped body
concentrically spaced from the wall of said mixing chamber and disposed adjacent the
discharge end of said fuel supply pipe, and said T-shaped body being open at its ends
and being connected with a source of pressurized air.
34. An installation in which molten metal is conducted along runners (312) from a
furnace to a ladle (314), comprising apparatus for suppressing the emission of fume
from said runners, characterised in that the fume suppressing apparatus comprises
fuel combusting burners (320) disposed at longitudinally spaced locations along said
runners, and each of said burners comprises an elongated burner head disposed in overlying
relation to the surface of the molten metal flowing in said runners and including
a generally cylindrical openended mixing chamber (324) having its axis disposed generally
parallel to the subjacent runner, a baffle structure including downwardly concave
plates (326) emanating from each end of said mixing chamber, a fuel supply pipe (328)
attached to said burner head with its discharge end in communication with said mixing
chamber, a T-shaped body (336) concentrically spaced from the wall of said mixing
chamber and disposed adjacent the discharge end of said fuel supply pipe, said body
being open ended and substantially coaxially disposed with respect to said mixing
chamber, and means (340) for supplying pressurized air to said T-shaped body.
35. An apparatus according to claim 34,,wherein the fuel supply pipe (328) is connected
to a source of gaseous fuel.