CA1036816A - Method and apparatus for removing slag from molten metal by suction - Google Patents

Abstract

Abstract of the Disclosure For removing slag from molten metal a port of a suction pipe is located at a predetermined level above the slag to suck it up. Water is caused to flow in a cooling jacket around the port and out of orifices around the periphery of the port to impinge against the slag being sucked up and pelletize it. The resulting pellets are introduced into a separator for separating the slag and water from vapor and air. The separator consists of a separator hopper and an auxiliary hopper having a discharge po?t arranged to be opened only when a similar discharge port of the separator hopper has been closed. The separator hopper is evacuated to suck the slag into it, the slag thus collected being transferred to the auxiliary hopper by opening the discharge port of the separator hopper, during which time air-tightness in the separator hopper is maintained by the auxiliary hopper. The slag in the auxiliary hopper is removed when the discharge port of the separator hopper has been closed, so that the separated slag can be intermittently removed from the separator while continuously effecting the suction of slag.

Description

~0368~6 The present invention relates to a method and apparatus for removing slag from molten metal by suction.
Various methods have been developed for removing slag in Heroult electric furnaces, from ladles used in making steel, from low frequency induction furnaces and reverberatory furnaces, from ladles for cupolas, slag produced in making rimmed steel and slag produced in melting metals. For example, there are a blow system in which slag is blown off, an adsorption system using a chain, wire, plate or the like to which slag is caused to stick, and a mechanical method in which slag is ladled out or drained off. However, all of these methods are inefficient and, in particular, the mechanical methods have many dis-advantages including causing thermal deformation.
The present invention provides a method and an apparatus for removing slag on the basls of a suction system wherein the ~uction portion of a suction pipe is prevented from being damaged by heat from the molten metal or by heat from high temperature slag, the sucked slag being formed into pellets that are suitable for transport within the suction pipe and subsequent separation.
Thus, the method according to the invention is characterized in that it comprises locating a suction port of a suction pipe at a predetermined level above slag to suck up the latter, causing water to flow out from around the periphery of said suction port against the sucked slag to pelletize said slag, and introducing the resulting pellets into separating means whereby the slag and water are separated from the vapor and air.

j4_ 1 -' -.~

10368~6 In an apparatus aspect, the invention consists of an apparatus for removing slag, comprising a suction pipe, a water cooling iacket provided at least around the outer periphery of a front end suction port of said suction pipe, a plurality of circumferentially spaced orifices for the flow of water from said cooling jacket to said suction port, separator means communicating with said suction pipe, and exhaust means communicating with said separator means for spplying suction to said suction pipe.

- la -The preferred embodiment employs a suction system using a vacuum pump or a rotary blower and also provides a method enabling slag to be continuously sucked and separated, which has been a problem in connection with the past employment of such system.
More particularly, the invention may use as said separator means a separator hopper and an auxiliary hopper having an openable and closable discharge port arranged to be opened only when an openable and closable port of sa~d separator hopper has been closed, said separator hopper being evacuated to suck slag into said separator hopper, the slag collected in the separator hopper being transferred to the auxiliary hopper by opening the dis-charge port of the separator hopper, during which time air-tightness in the separator hopper is maintained by said auxiliary hopper, the slag in the auxiliary hopper being removed when the discharge port of the separator hopper has been closed whereby separated slag can be lntermittently removed from the separating means while continuously effecting the suction of slag.
In embodying th~ method of the invention described above, it is preferable to use a suction head for slag removal comprising a suction pipe, a water cooling jacket defined at least around the outer periphery of a suction port of said suction pipe, and a plurality of circumferen-tially spaced orifices through which water in the jacket can flow into said suction port. ~ith such a suction head, at least the end portion of the suction pipe can be positively cooled by the water in the water cooling jacket while the water in the jacket can be utilized for quick cooling and pelletization of tile sucked slag.

~036816 Further, according to a preferred embodiment of the invention, the suction port is embodied in a suction mouthpiece removably mounted on the suction pipe. This arrangement is economical in that the end portion of the suction pipe, which is most likely to be affected by heat, can be replaced depending upon its condition. Moreover inspection and maintenance of the suction port are easy.
By using suction mouthpieces different in the cross-sectionsl shape and size of their suction port, it is 1~ possible to change the suction conditions depending upon the circumstances.
In the case of an arrangement wherein orifices are formet in the peripheral wall of an inner pipe constituting said ~acket, and water is allowed to flow out through said orifices obliquely downwardly toward the slsg suction port, such orifices have to be bored in the inner pipe of the iacket at an angle (about 60), so that the machining and maintenance are difficult and the sucked alag tends to clog in the orifices. There is another disadvantage in that the point where the sucked slag and the water flowing out through the orifices are mixed is remote from the surface of molten metal.
As the point of mixing with water is made nearer to the slag sucking-up surface, that is, to the opening side of the slag suction mouthpiece, the quick cooling and pelletization of the slag become faster and more reliable, preventing overheating of the slag suction mouthpiece and ensuring that the suction force will act on the pellets of slag more positively to improve the slag suction effect.

According to another embodiment of the present invention, this problem is taken into consideration by using a suction head having orifices formed in the lower end.periphery of the water cooling jacket so as to be downwardly directed, the suction mouthpiece being pro~ided with a surface whereby water flowing out through these orifices is deflected to the center of the suction port.
With such a suction head, not only are machining, lnspection and maintenance of the orifices easy, but also 1'0 the suction mouthpiece is forcibly cooled to improve its durability. Moreover, the point where the water flowing out through the orifices and the slag being sucked up are mixed can be made sufficiently close to the open end ~f the suction port, thus minimizing the risk of the orifices getting clogged.
Numerous other features of embodiments of the present invention will be described with reference to the accompanying drawings, in which:
Figure 1 is an elevational view, partly broken away, showing a basic embodiment of the present invention;
Figure 2 is a longitudinai section of separating means used in said embodiment;
Figures 3 through 8 are longitudinal sections showing other embodiments of a suction head;
Figure 9 is an exploded view, partly broken away, of the principal portions of the suction head shown in Figure 8;
Figure 10 is a view as indicated at X-X in Figure 9;
Figure 11 is a section taken on the line XI-XI

in Figure 9;

1036Bi6 Figures 12A, 12B and 12C are sectional views showing the principal portions of alternative suction mouthpieces f or use in the suction head shown in Figure 8;
Figure 13 is an elevational view, partly broken away, showing how the suction head shown in Figure 8 is used;
Figure 14 is a longitudinal section showing snother embodlment of separating means;
Figure 15 is a plan view of Figure 14; and Figure 16 is a time chart indicating the phases of operations of the various parts of the separating means.
In Figure 1, the numeral 1 designates a ladle;

2, molten metal; and 3 desigaates slag. A slag suction pipe 4 has an enclosure 6 secured around the periphery of its end suction port 4a to define a jacket 5. Connected to the ~acket S are a water supply pipe 7 and a drain pipe 10 having an air-e5cape valve 8 and a safety valve 9. The inner wall of the ~acket 5 is provided with a plurality of circumferentially spaced orifices 11 opening to the interior of the suction pipe 4.
A separator hopper 12, at its upper central region, receives an open lower end 13a of an exhaust connector pipe 13. Tangentially connected to the peripheral wall of the hopper and disposed laterally of the opening 13a is an air suction connector pipe 14 to which the suction pipe 4 is connected.
The separator hopper 12 has a discharge port 15 at its lower end, to which the upper end of an auxiliary hopper 16 is connected. The discharge port 15 of the sepa-rator hopper and the discharge po ~ of the auxiliary hopper are provided with openable lids 18 and 19, respect-ively. These lids 18 and l9 are fixed on rotary shafts 20a and 20b supported for rotation laterally of the discharge ports 15 and 17 respectively, these rotary shafts 20a and 20b being operatively connected to an opening and closing mechanism 22 through arms 21a and 21b. The mechanism 22 comprises a cam 23 for rotation by a motor ant connecting rods 24a and 24b for transmitting the 10 motion of the cam 23 to the arms 21a and 21b, respectively.
The connecting rods 24a and 24b are arranged on opposite gides of the cam 23 so that rotation of the cam 23 causes the lids 18 and 19 to be opened and closed alternately.
The numeral 25 designates supports for the sliding movement of the connecting rod 24a or 24b; 26 are cam rollers; and 27a and 27b are springs for normally urging the lids 18 and 19 to their closed positions. The separator hopper 12 and the auxiliary hopper 16 are also provided with water-cooling ~ackets 28a and 28b, re8pectively, which, as shown in Figure 2, communicate with each other, the upper end o the jacket 28b and the lower end of the jac~et 28b being provided with a drain port 29 and a water supply port 30, respectively.
The numeral 31 designates a slag discharging chute. Further, as shown in Figure 2, the water jacket 28b may be connected to the lid 18 by a flexible pipe 32 to cool this lid.
The manner in which this apparatus is used will now be described.
The suction pipe 4 is connected to the air suction connector pipe 14 of the separator hopper 12 through a flexible pipe 33, while the exhaust connector pipe 13 is connected to suction means 36 such as a vacuum pump or a blower, through an on-off valve 34 and a pressure gage 35.
In addition, the numerals 37 and 38 designate an on off valve and a pressure gage respectively, provided in the water supply pipe 7.
When the suction means 36 i5 operated, the suction port 4a of the pipe 4 is evacuated through the separator hopper 12, so that, by positioning this suction port 4a at a suitable level above the slag 3, the latter i8 sucked up into the pipe 4. Since water is supplied to the ~acket 5 by the water supply pipe 7 and flows into the 8uction port 4a through the orifices 11, the slag 3 is qulckly cooled and thereby pelletized and transferred to the separator hopper 12 through the pipes 4 and 33. The pelletlzed slag is separated and accumulates on the lid 18 which closes the port 15.
The cam 23 is rotated by any suitable means ~not shown) either continuously, or intermittently at regular intervals, whereby the lids 18 and 19 are select-ively opened. When the lid 18 i9 opened, the slag collected in the separator hopper 12 falls into the auxiliary hopper 16 whose discharge port 15 is now closed, where it is temporarily stored. After the lid 18 is closed again, the lid 19 is opened so that the slag collected in the auxiliary hopper 17 is discharged onto the chute 31. By reason of the fact that the lids 18 and 19 are alternately opened the separated slag can be intermittently and automatically discharged to the exterior without risk of opening the suction system from the port 4a to the suction means 36 to atmosphere through the discharge ports 15 and 17 simul-taneously, with consequent loss of pressure. Thus, the slag 3 is continuously sucked and separated.
Since the separator hopper 12, the auxiliary hopper16 and its lid 18 are cooled by the cooling water flowing from the water supply port 30 through the jackets 28b and 28a and out through the drain port 29, even if the sucked and separated slag is at a high temperature, the hoppers 12 and 16, the lids 18, 19 and the mechanism 22 will not be damaged by heat.
Figure 3 shows a modification in which the suction port 4a ls funnel-shaped, such funnel-shaped portion being provided with orifices 11. Figure 4 shows another modifica-tion in which the enclosure 6 of the jacket 5 is formed by a torus-shaped pipe.
Another embodiment relating to the slag suction head i8 shown in Figures 5 and 6. A suction head 41 has a water-cooling ~acket 43 and internally a slag suction passage 42. The jacket 43 is of double pipe construction comprising inner and outer pipes 44 and 45, the outer pipe 45 carrying annular end plates 46 and 47 at its upper and lower ends, respectively, interconnecting the inner and outer pipes to seal the space therebetween. Further, the jacket is provided with an air-escape valve 48 and a safety valve 50, and is adapted to be supplied with water through a water supply pipe connector 49. The inner pipe 44 of the jacket 43 is longer than the outer pipe 45 and extends above the latter, so that, after the slag has been sucked through the slag suction passage 42, it is transferred to a separator hopper such as the one shown in Figure 1 through a bent pipe 52 removably connected to the pipe 44 by a sleeve 51.

~036816 The lower end of the inner pipe 44 extends somewhat below the lower end of the outer pipe 45 to define a skirt portion 53. Secured to the end plate 47 is a sleeve 55 having an externally threaded portion 54. Inside the sleeve 55, the end plate 47 is provided with a plurality of circum-ferentially regularly spaced orifices 56 extending at right angles therethrough. A slag suction mouthpiece 57 having sn internally threaded portion 58 is threadedly fitted over the sleeve 55. The numeral 59 designates an abutment 9urface provided on the slag suction mouthpiece 57 for engaging the lower end of the sleeve 55. When the surface 59 abuts the sleeve 55, there is a clearance 61 between the skirt portion 53 and the inner inclines surface 60 of the mouthpiece 57 so that, as the water from the orific~s 56 passes through this clearance 61, the flow is towards the center of the suction port 62 of the mouthpiece 57.
The operation will now be described. With the 8uction head 41 positioned with its suction port 62 disposed immediately above the molten metal, water is supplied to the jacket 43 through the water supply pipe connector 49.
Air is drawn through the suction port 62 by a vacuum pump or the like (not shown), whereby the slag is sucked up through the suction port 62, slag suction passage 42 and pipe 52 and is transferred to the separator tank. Con-currently therewith the.water in the jacket 43 flows against the inclined surface 60 of the mouthpiece 57 through the orifices 56. As it passes through the clearance 61 its direction of flow is changed so that it flows along the inclined surface 60, thus flowing laterally toward the suction port 62. Therefore, as the slag is sucked through the suction port 62, it is quickly cooled by the action of g _ the water flowing inwardly from around its periphery and is pelletized. Thus the point where the slag and water are mixed together is located immediately before the slag enters the slag suction passage 42.
The suction head itself ls cooled by the water supplied to the jacket 43. Since the water from the orifices 56 iB directed against the inner wall surface of the slag ~uction mouthpiece 57, the latter is constant~y cooled, thereby preventing such mouthpiece from being overheated by the heat of radiation and transmission from the slag.
Purther, since the water flows transversely and laterally of the slag being sucked up, there is no danger of the slag clogging in the mouthpiece 57. The skirt portion 53 prevents the slag from clogging the orifices 56. Also the water flowing towards the suction port 62 produces a ~ilencing effect. Without this flow of water there would be a very strong metallic jet sound.
The skirt portion 53 and/or sleeve 55 can be omitted. In this ca9e, as shown in Figure 7, an externally threaded portion 63 may be provided on the outer periphery of the lower end of the outer pipe 45 of the jacket 43, so that the slag suction mouthpiece 64 is directly mounted on the outer pipe 45 through its internally threaded portion 65. In the arrangement shown in Figure 7, no inclined surface 60 is provided. Instead, a flat recess 67 is formed in the mouthpiece 64 so that an annular water flow passage 66 extending at right angles to the direction of slag suction is defined between the lower end of the ~acket 43 and the mouthpiece 64. Thus water from the orifices 56 has its direction of flow changed through 90 :1036816 degrees 50 as to be directed against the slag being sucked up .
Now referring to Figures 8 to 12 a suction head 70, like the suction head 41 shown in Figure 5, is provided with a water-cooling jacket 75 defined by an inner pipe 71, an outer pipe 72 and upper and lower annular plates 73 and 74. A safety valve 77 and an air-escape valve 78 ~re connected to the ~acket 75 through a branch pipe 76.
Al~o connected to the ~acket is a water supply pipe 79.
A curved pipe 80 is removably connected to the upper end of the inner pipe 71 by a socket 81. In connecting the pipe 80, an upper end flange 83 of a protective sleeve 82 is located in the inner pipe 71 and extending along the entire length of the latter is clamped between the end surfaces of the pipe 80 and the pipe 71 so that the sleeve 82 ls fixed. The sleeve 82 can be removed from the inner pipe 71 for replacement by a new one. The inner pipe 71 ls provided with a plurality of circumferentially spaced orifices 84 which are disposed ad~acent the lower end of the water-cooling jacket 75 near the lower end of the inner pipe. Holes 85 aligned with said orifices 84 are formed in the sleeve 82.
A suction mouthpiece 86 has an engagement portion 87 adapted to be fitted over a sleeve portion 71a of the inner pipe 71 projecting below the lower annular plate 74.
The engagement portion 87 is provided with two slits 89 adapted to receive two locking projections 88 fixed to the sleeve portion 71a and annular plate 74. The outer peripheral surface of the engagement portion 87 and the outer edge of the projections 88 are respectively provided i036816 with grooves 90 and 91 in such a manner that they form a single continuous annular groove when the engagement portion 87 is fitted over the projecting sleeve portion 71a with said slots 89 receiving the locking projections 88. The suction mouthpiece 86 is thus removably attached to the suction head 70 by a ring ~2 removably fitted in the continuous groove 90, and 91. The mouthpiece 86 has a ~uctlon port 94 teflned by lts lnner surface 93 which is contlnuous wlth the lnner surface of the sleeve 82, said inner surface 93 belng curved and flaring.
The sucking condition for the slag may be option-ally changed by replacing the suction mouthpiece 86 shown in Figure 8 by a suction mouthpiece 97 shown in Figure 12A
having a suction port 96 defined by an inner surface 95 having a conical flare; a suction mouthpiece 100 shown in Flgure 12B having a suctlon port 99 deflned by an inner cyllndrlcal surface 98; a suction mouthpiece 103 shown in Figure 12C havlng a suctlon port 102 deflned by an inner ~urface 101 in the form of a converging cone; or any other suitable suction mouthpiece.
A static pressure tube 104 (Figure 13) is provided at its lower end with an air injection nozzle 105 which opens in the same direction as the suction port 94 of the suction mouthpiece 86 and is arranged beside the suction head 70. One end of a detection tube 106 arranged beside the tube 104 opens into the tube 104 adjacent the nozzle 105.
The manner in which the suction head 70 is used will now be described with reference to Figure 13.
The pipe 80 is connected to a separator hopper 108 through a flexibl~ pipe 107, said hopper having a suction pipe 109 connected to suction means such as a vacuum pump (not shown). The water supply pipe 79 is connected to a water pipe 112 provided with an on-off valve 110 and a pressure gage 111. With the suction mouthpiece 86 facing the slag 115 on the molten metal 114 in a laddle 113 at a predetermined level above said slag, suction is started, whereupon air (vapor) and slag are sucked into the suction mouthpiece 86 and the sleeve 82 which follows it. At this time the cooling water under pressure supplied from the wster supply pipe 112 fills the jacket 75 and, while cooling the inner pipe 71 and sleeve 82, also flows into the suction mouthpiece 86 from the orifices 84 and holes 85. As a result the slag sucked into the mouthpiece 86 contacts the water and is thereby cooled and momentarily pelletized. The pellets are then passed through the pipes 80 snd 107 into the separator hopper 108, where they fall under their own weight and collect.
Standart data for the apparatus described above 20 are as follows. The rate of supply of water is 0.04-0.5 liters/sec; the supply water pressure is about 1.5kg/cm for 0.2 liter/sec; water flows from orifices 84 of diameter of 1.4-3mm (preferably about ~.5mm); the rate of suction flow in the suction mouthpiece 86 and sleeve 82 is about ~0-60m/sec; and the partlcle size of pellets of slag formed by the action of water jets is about 3-30mm.
If the static pressure tube 104 is provided, it can be utilized for automatically controlling the level of the air supply means (not shown) to blow air at a constant pressure from the nozzle 105. The static pressure in the -- 1~ --10368~6 tube 104 changes with the distance between the nozzle 105 and the slag 115 on the molten metal 114, i.e., the level of the suction mouthpiece 86 above the molten metal. This static pressure may be detected through the detection pipe 106. For example, one end of a U-tube 116 containing a liquid such as mercury may be connected to said detection tube to produce a head corresponding to the static pressure.
A swltch 117 may be used to open or close in response to the magnitude of such head, the switch automatically con-trolling a motor 118 for driving a rack and pinion mechanism or screw ~ack mechanism whereby the suction mouthpiece 86 is automatically maintained at the predeter-mined level.
Another embodiment of the separator means for 8eparating sucked slag will now be described with reference to Figures 14 through 16.
In Figures 14 and 15, the numeral 121 designates a separator hopper, and disposed in the upper central region thereo~ is the lower end opening 122a of an exhaust pipe connector pipe 122. A suction connector pipe 123 is tsngentially connected to the peripheral wall of the hopper laterally of the opening 122a. When a vacuum pump or the like is connected to the pipe 122 and air is sucked, a negative pressure is produced in the separator hopper 121 - and the slag and water sucked in through the suction connector pipe 123 are separated from the mixture of gas, air and vapor by cyclone effect and fall downwardly of the separator hopper 121. The separator hopper 121 has a lower end opening 124 having connected thereto an intermediate hopper 125 to which a bottom hopper 126 is connected, thus 10;~6816 providing a three-chamber arrangement. Disposed below the discharge port 127 of the intermediate hopper 125 is an air lock valve 128 adapted to be moved up and down by air pressure to close and open the discharge port 127, while at the discharge port 129 of the bottom hopper 126 there is disposed a damper 130 for opening and closing such discharge port. The valve 128 and damper 130 are arranged to be opened and closed alternately with each other.
The intermediate hopper 125, which perfects the separating effect by allowing the slag to be quickly discharged from the separator hopper 121, serves temporarily to retain the fallen slag. Within the intermediate hopper 125 there is a baffle plate 131 disposed immediately below the lower end opening 124 of the separator hopper to prevent reverse flow of the slag. The air lock valve 128 has an umbrella-like valve body 133 vertically movably fitted over an upright pipe portion 132a of an air supply pipe 132 in the bottom hopper 126, thè arrangèment being such thst when an automatic valve Vl is opened to admit air under pressure in the direction of the arrow A, the valve body 133 is pressed against a valve seat of the discharge port 127 thereby sealing the intermediate hopper 125 and separator hopper 121.
The damper 130 is connected through a link 135 to a rotary shaft 134 rotatably supported laterally of the discharge port 129. By rotating the rotary shaft the discharge port 129 is opened and closed. In this embodiment the end of a cam lever 136 extending from the shaft 134, as shown in Figure 15, abuts a cam 137. By rotating the 30 cam 137 by a motor 138 through a speed reduction mechanism - 139, the damper 130 is vertically swung around the axis of the shaft 134, but any other suitable means using air pressure or the like may be employed to carry out this open-ing and closing operation. The numeral 140 designates a balance weight and 141 designates a discharge chute.
The opening and closing operation and mechanism of the air lock valve 128 and damper 130 will now be te~cribed. A cam disc 142 is attached to the cam 137 and there are provided limit switches LSl and LS2 adapted to be separately actuated as the cam disc 142 is rotated. The limit switch LSl is connected to the automatic valve Vl and the switch LS2 is connected to automatic valves V2 and V3. The automatic valves V2 and V3 are placed in a balance pipe 143 which connects the air pressure supply pipe 132 ant the bottom hopper 126 to the connector pipe 122. The balance pipe 143 assists the valve body 133 in falling under its own weight by supplying air pressure to the air lock valve 128, and maintains the valve body in its open position. Further, the balance pipe 143 serves to equalize the pressures in the separator hopper lZl, the intermediate hopper 125 and the bottom hopper 126.
The opening and closing cycle effected by such mechanism will now be described with reference to Figure 16.
As the cam disc 142 and cam 137 each begins to make one complete revolution, the air lock valve 12~ closed and the damper 130 is opened to discharge slag through the bottom hopper 126. Subsequently the damper 130 is closed and the air lock valve 128 opened to discharge slag from the intermediate hopper 125 into the bottom hopper 126. That 0 is, during the time the~cam disc 14~ is rotated through a constant angle (90 in the embodiment shown) from thereference angular position, the limit switch LSl is in - its operative position to maintain the automatic valve Vl in its open position so that the air lock valve 128 is positively maintained in its closed position. This position is maintained until the disc cam is rotated through 120~. On the other hand, the damper 130 is maintained in its open position by the cam 137 while the latter is being rotated from its 15 position to its 105 position.
During rotation of the cam between 120 and 345, the limit switch LS2 is in its operative position to maintain the automatic valves V2 and V3 in their open positions so that the air lock valve 128 is positively maintained in its open position, this position being maintained until the cam is rotated to 360. During this time the damper 130 is maintained in its closed position for the rotational angle of the cam from 105 through ~60 to 15. Therefore, when the damper is in its open region from 15 to 105, the slag is discharged from the bottom hopper 126 to the outside of the system, and when the air lock valve 128 is in its open region from 120 to 360, the slag is discharged from the intermediate hopper 125 into the bottom hopper 126. It will thus be seen that, since the air lock valve 128 and the damper 130 are not both open at the same time, the slag can be discharged while maintain-ing the vacuum in the separator hopper.
The slag being sucked is in the form of pellets of molten slag and, in view of the fact that these slag pellets are stilL at a relatively high temperature while they pass through the separator hopper 121 and stay in the ~ .

intermediate and bottom hoppers 125 and 126, there i8 provided a cooling water jacket 146 defined by upper and lower outer sleeves 144 and 145. Water is supplied thereto through a water supply port 147 and discharged through a water discharge port 148, thereby cooling the same. The numeral 149 designates a drain port and 150 designates a communication pipe which establishes communication between the upper and lower outer sleeves 144 and 145. Although the air lock valve 128 is sub~ected to relatively high temperatures, since it is operated by air pressure, it will be cooled by that air. Since the air lock valve 128, the damper 130 and the lower portion 125a of the inter-mediate hopper 125 might be damaged by heat, they are constructed so that they can be replaced. The air lock valve may be actuated by means other than air pressure.

Claims (15)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A method of removing slag from molten metal comprising locating a suction port of a suction pipe at a predetermined level above the slag to suck up the latter, causing water to flow out from around the periphery of said suction port against the slag being sucked up to pelletize the latter, and introducing the resulting pellets into means for separating the slag and water from vapor and air.

2. A method of removing slag as set forth in claim 1, wherein said separating means comprises a separator hopper and an auxiliary hopper having an openable and closable discharge port arranged to be opened only when an openable and closable discharge port of said separator hopper has been closed, said separator hopper being evacuated to suck slag into said separator hopper, the slag collected in the separator hopper being transferred to the auxiliary hopper by opening the discharge port of the separator hopper, during which time air-tightness in the separator hopper is maintained by said auxiliary hopper, the slag in the auxiliary hopper being removed when the discharge port of the separator hopper has been closed whereby separated slag can be intermittently removed from the separating means while continuously effecting the suction of slag.

3. A suction head for slag removal, comprising a suction pipe, a water cooling jacket defined at least around the outer periphery of a suction port of said suction pipe, and a plurality of circumferentially spaced orifices through which water in the jacket can flow into said suction port.

4. A suction head for slag removal as set forth in claim 3, wherein said suction port is defined by a suction mouthpiece removably mounted on said suction pipe.

5. A suction head for slag removal as set forth in claim 3, including a protective sleeve removably fitted in said suction pipe.

6. A suction head for slag removal as set forth in claim 3, wherein beside the suction head is a static pressure tube having at an end an air injection nozzle opening in the same direction as the suction port, and a detection pipe branching off from said tube at a location adjacent said nozzle.

7. A suction head for slag removal as set forth in claim 4, wherein said orifices are provided around a lower end periphery of said water cooling jacket and are downwardly directed, said suction mouthpiece being provided with a surface whereby water flowing out of said orifices is deflected to the center of the suction port.

8. A suction head for slag removal as set forth in claim 4, wherein a lower end of said suction pipe projects beyond a lower end of the water cooling jacket, said suction mouthpiece being provided with an engagement portion adapted to be fitted over such projecting pipe portion, the suction pipe being provided with locking projections adapted to be fitted in slots formed in the engagement portion, the peripheral surface of said engagement portion and the outer sides of said locking projections being provided with grooves that form a single continuous groove when said engagement portion is fitted over the projecting pipe portion with said locking projections fitted in said slots, there being provided a ring to be fitted in such single continuous groove for holding said suction mouthpiece in position.

9. An apparatus for removing slag, comprising a suction pipe, a water cooling jacket provided at least around the outer periphery of a front end suction port of said suction pipe, a plurality of circumferentially spaced orifices for the flow of water from said cooling jacket to said suction port, separator means communicating with said suction pipe, and exhaust means communicating with said separator means for applying suction to said suction pipe.

10. An apparatus for removing slag, comprising a suction pipe, a water cooling jacket provided at least around the outer periphery of a suction port of said suction pipe, a suction head provided with a plurality of circumferentially spaced orifices through which water in the jacket can flow into said suction port, separator hopper means communicating with said suction pipe, exhaust means for evacuating said separator means, sealed auxiliary hopper means connected to a lower end of said separator hopper means, control means including a valve body for opening and closing a discharge port of said separator hopper means communicating with the auxiliary hopper means and a second valve body for opening and closing a discharge port of said auxiliary hopper means whereby said discharge ports are opened and closed alternately, and a water cooling jacket provided externally of said two hopper means.

11. An apparatus for removing slag as set forth in claim 10 wherein said two valve bodies are spring-loaded to close their respective associated discharge ports, and said control means comprises a driven rotary cam and two cam followers associated with said cam to move said valve bodies to their open positions.

12. An apparatus for removing slag as set forth in claim 10 including cooling means for cooling with water at least the valve body which opens and closes the discharge port of the separator hopper means.

13. An apparatus for removing slag as set forth in claim 10 wherein in order to form an enlarged slag storage chamber immediately above the discharge port which is opened and closed by the valve body, said separator hopper means comprises a downwardly converging separator hopper and an intermediate hopper for forming said slag storage chamber.

14. An apparatus for removing slag as set forth in claim 10 wherein the valve body which opens and closes the discharge port of said separator hopper means is pneumatically raised to close said discharge port.

15. An apparatus for removing slag as set forth in claim 14, including changeover valves for selectively changing over a pipe leading to said valve body between the pressurized air source and an exhaust line leading from the interior of the separator hopper means.