US2716843A

US2716843A - Slag foaming

Info

Publication number: US2716843A
Application number: US213201A
Authority: US
Inventors: John C K Stuart
Original assignee: Denman Enterprises Ltd
Current assignee: Denman Enterprises Ltd
Priority date: 1951-02-28
Filing date: 1951-02-28
Publication date: 1955-09-06
Anticipated expiration: 1972-09-06

Description

Sept. 6, 1955 .J. c. K. STUART SLAG FOAMING 2 Sheets-Sheet Filed Feb. 28 1951 INVENTOR John C. K. Stuart BY %M RMQ ATTORNEY Sept. 6, 1955 J. c. K. STUART SLAG FOAMING 2 Sheets-Sheet Filed Feb. 28,. 1951 L "an INVENTOR John C. K. Stuart ATTORNEY SLAG FOAMING John C. K. Stuart, Toronto, Ontario, Canada, assignor, by mesne assignments, to Denman Enterprises, Limited, Hamilton, Ontario, Canada, a corporation of Canada Application February 28, 1951, Serial No. 213,201

Claims. (Cl. 49-1) The present invention relates to the production of foamed slag of lightweight cellular structure for use in the manufacture of insulation products. More particularly, the invention contemplates the provision of an improved process of the type employing a foaming pit for the treatment of blast furnace slags of varying temperatures, viscosities and mineral compositions. The invention further contemplates the provision of improved apparatus for use in producing foamed slag products.

It is well known that, by bringing molten slag into contact with controlled quantities of water or other suitable liquid medium, the slag will be puffed by the action of steam generated through contact of the molten slag with the liquid to produce an expanded body having relatively thin walls enclosing innumerable small cells which is ideally suited for use in the manufacture of insulation products.

This principle has been applied in the past in processes employing various mechanical arrangements to effect the foaming act-ion which are generally referred to as the machine processes, and in the less expensive sand-foaming process, wherein the molten slag is poured into an open sand pit which has been well-moistened with foaming liquid prior to the pouring operation. The former processes, while providing high-quality products, are inherently expensive because of the high maintenance costs of mechanical parts, and, consequently, they are not suitable for large scale operations. In the basic sand-forming process, it is difficult to contact a controlled amount of foaming liquid with the slag during the foaming operation, and, consequently the foamed slags obtained by the process are either too heavy or are of a granulated composition unsuitable for use as commercial products.

In an effort to overcome the inherent disadvantage of the sand-foaming process, an arrangement has been suggested which employs a network of pipes buried beneath the porous surface of the sandpit which pipes are provided with outlet jets for supplying foaming liquid to the sand during the foaming operation. This type of arrangement, while an improvement over the basic sandfoamed process, is not capable of producing foamed slags of the quality obtained by the more expensive machine foaming processes. This is due primarily to the fact that the extremely high temperatures of the slag entering the pit immediately consumes the available moisture present at the surface of the sand and produces a surface layer of dry sand which acts to prevent additional moisture from reaching the slag.

As a modified form of the above arrangement, there has been suggested a construction employing a porous honey-combed concrete bed having the supply pipes and outlet jets embedded in the concrete below the top surface of the bed. This type of construction insures the delivery of an ample supply of foaming liquid to the molten slag, but the extreme temperature variations encountered between periods when the pit is idle and in use, causes expansion and contraction of the concrete bed which results in destruction of the bed in a relatively short period of time.

nited States Patent In addition to the numerous structural disadvantages discussed above the pit type of foaming operations heretofore customarily employed in the industry are subject to the danger or explosions resulting when molten iron present in the slag ladles contacts the foaming liquid in the pit. In an attempt to avoid such explosions, a special type of pouring ladle is employed which is tapped at a point above the anticipated level of molten iron in such manner as to allow for collection of the iron at the bottom of the ladle. This not only prevents use of the full capacity of the ladles during the pouring operation but also necessitates relatively slow pouring of the molten slag to insure retention of the iron in the bottom portion of the ladle.

It is a primary object of the present invention to provide an improved slag foaming process which is not subject to the disadvantages of the heretofore known processes.

It is also an object of the invention to provide a process and apparatus of the class described which permit substantial savings in operational costs and provide greater product yields than have been realized from similar operations in the past.

A further object of the invention is to provide a static type of foaming apparatus which is ideally suited for use in the large scale production of high-quality foamed slags.

The above-mentioned and other features and objects of the invention and the manner of attaining them will become more apparent and the invention itself will be better understood by reference to the following description of an embodiment of the invention in conjunction with the accompanying drawings, wherein:

Fig. l is a plan view of a slag foaming pit incorporating the principles of the present invention;

Fig. 2 is a sectional side view of the foaming pit, taken along the line 22 of Fig. 1;

Fig. 3 is an enlarged sectional view of a portion of the foaming pit, taken along the line 33 of Fig. 1;

Fig. 4 is an enlarged plan view of the portion of the foaming pit illustrated in Fig. 3, taken along the line 4-4 of Fig. 3; and

Fig. 5 is a detailed sectional view of a portion of the foaming pit bottom, taken along the line 5-5 of Fig. 4.

Figs. 1 and 2 show a foaming pit comprising a substantially rectangular bed 10 enclosed on two sides by perpendicular walls 11 and provided with

inclined end surfaces

12 and 13 respectively.

The bed or bottom surface 10, the side walls 11 and the inclined surface portion 12 are formed of dense concrete. A portion 14 of the bottom surface 10 is formed of reinforced concrete having steel reinforcing members 15 embedded therein and extending in different directions through the concrete, as shown in Fig. 4.

A plurality of evenly distributed outlet jets 16 are embedded in the reinforced concrete portion 14 of the bottom surface and extend to the surface of the reinforced concrete. The outlet jets 16 are supplied from a network of pipes 17 embedded in the concrete below the reinforced surface thereof. The pipes 17 in turn connected to a lead-in main 18 which may be supplied with foaming liquid from'a supply tower or any other suitable pressurized source. The lead-in main 18 is provided with a control valve 19, Fig. l, for controlling the flow of foaming liquid to the supply pipes 17 and outlet jets 16. If desired, the supply pipes 17 may each be provided with an individual control valve for selectively controlling the supply of foaming liquid to small areas of the foaming pit.

The reinforced portion 14 of the bottom surface is also provided with a plurality of evenly distributed porous drain channels 20 which empty into drainage passages 21 provided in the concrete below the reinforced surface thereof. The drain channels 20 are preferably formed by inserting blocks of wood or similar material along the line of the drainage passages 21 when the reinforced concrete slab is cast. The blocks are removed after the concrete sets and the resulting holes are then filled with porous concrete or any other suitable porous material. The drainage passages 21 extend through the bottom of the pit and are provided with removable covers 22 at each side of the pit for cleaning purposes.

The inclined end surface 12 of the pit is also formed of dense concrete and is provided with steel reinforcing members 15 running in both directions through the concrete. Embedded in the concrete and emptying directly onto the surface 12 are a plurality of evenly distributed outlet jets 23 which are slightly larger than the outlet jets 16 in the bottom surface. In practice, I have found that outlet jets of approximately two inches in the bottom surface 14 and approximately three inches in the inclined surface 12 give good results. The outlet jets 23 are supplied with foaming liquid from a network of supply pipes 24 which are connected to the lead-in main 18 and which may be provided with an individual control valve as previously pointed out with respect to the pipes 17.

Molten slag is supplied to the inclined surface 12 of the pit from supply ladles 25 which are mounted on a carriage 26 movable on rails 27 positioned at right angles to the pit above the surface 12. The ladles 25 may be of conventional design including a mechanism on the carriage 26 for tilting the ladles into a full pouring position such as to empty the ladles in approximately ten to twentyfive seconds. The outwardly extending side walls 28 of the inclined surface 12 insure an even distribution of the slag as it flows onto the bottom surface of the pit.

The position of the ladles 25 above the inclined surface 12 of the pit is such as to provide an initial pouring head sufficient to move the slag in a unidirectional flow across the bottom of the pit, with at least a portion of the slag overflowing the inclined surface 13 at the opposite end of the pit. I have found that by providing the inclined surface 12 with a slope of not less than one foot in three feet of length and by imparting an initial pouring head of approximately fourteen feet to the molten slag, the slag will flow smoothly across the bottom of the pit and onto the inclined surface 13 at the opposite end of the pit, with a portion of the slag overflowing the pit and foaming on the ground adjacent the pit. Under such conditions of operation the inclined surface 13 functions to arrest the motion of the slag flow without causing undesirable backwash of the slag.

In operation, foaming liquid is initially introduced di- F rectly into the pit from the

outlet jets

16 and 23 to provide a relatively shallow layer of liquid in the pit prior to the introduction of the molten slag. The slag is then poured onto the inclined surface 12 where the outlet jets 23 function to continuously supply foaming liquid during the pouring operation. The foaming liquid on the surface 12 lubricates the flow of slag into and across the pit and starts the slag foaming immediately upon leaving the ladle. I have found that this immediate foaming action of the slag functions to suppress any explosion that might otherwise occur from molten iron present in the ladle contacting foaming liquid in the pit.

The foaming slag moves in a unidirectional flow across the bottom portion 14 of the pit containing the outlet jets 16 and is preceded by a thin wall of foaming liquid resulting partly from the foaming liquid supplied from the outlet jets 23 on the inclined surface 12 and partly from the foaming liquid present in the pit prior to the pouring operation. As the slag flows across the outlet jets 16, additional foaming liquid is introduced directly into the slag until it is determined that the slag is foamng properly at whch time the supply of foaming liquid is stopped. The slag moves onto the plain surface of the pit bottom and thence onto the inclined surface 13, which functions to arrest the motion of the slag. A portion of the slag may overflow the pit and continue foaming on the surface adjacent the pit as has been previously pointed out above. The slag is left in the pit until the foaming action resulting from liquid which is entrapped beneath the slag is completed, at which time the bank slag may be removed by drag lines or a bulldozer.

In similar processes of this type which have been heretofore customarily employed in the industry, it has been impossible to foam more than approximately five tons of slag at one pour. By employing the principles of the present invention, I have been able to foam more than three times this volume of slag at each pouring operation or approximately sixteen and one half tons of slag, with substantial savings in time and product cost. The foamed slags obtained from such operations are of high quality, ideally suited for use in the manufacture of insulating uni s.

In thus practicing the invention, I employed a foaming pit having a bottom surface approximately fifty-two feet long and thirty-five feet wide of which approximately thirty-two feet of the length was reinforced concrete containing surface outlet jets which were supplied with water as the foaming medium. A single pit of this size produced approximately two hundred tons per day over an extended period of time without damaging the bottom surface of the pit and requiring very little maintenance otherwise. While I have described above the principles of my invention in connection with specific apparatus, it is to be clearly understood that this description is made only by way of example and not as a limitation to the scope of my invention.

I claim:

1. Apparatus for use in carrying out an operation of the type in which molten slag is contacted with a liquid capable of vaporizing under the influence of heat contained in the slag and in which vapor produced as a result of contact of the slag and liquid causes swelling of the slag with the production of porous plastic mass of bank slag of substantially greater volume than the volume of the molten slag, which comprises a foaming plt having a solid bottom surface of substantially moisture impervious material and provided throughout a portion of its length with a plurality of liquid outlet jets extending to the surface of the bottom at spaced intervals thereof, an inclined end surface of solid material joined to the bottom surface adjacent the liquid outlet jets and provided with a plurality of similar liquid outlet jets extending to the surface at spaced intervals thereof, means for supplying a controlled amount of liquid under pressure to said liquid outlet jets, a plurality of porous drain channels formed integral with the solid bottom surface and positioned at spaced intervals adjacent the liquid outlet jets, and means for introducing a mass of molten slag onto the inclined end surface of said pit from an initial pouring head sufiicient to spread the slag in a unidirectional flow across the portion of the bottom surface containing the liquid outlet jets and substantially across the remainder of the bottom surface of the pit.

2. Apparatus for use in carrying out an operation of the type in which molten slag is contacted with a liquid capable of vaporizing under the influence of heat contained in the slag and in which vapor produced as a result of contact of the slag and liquid causes swelling of the slag with the production of a porous plastic mass of bank slag of substantially greater volume than the volume of the molten slag, which comprises a foaming pit having a solid bottom surface of substantially moisture impervious material reinforced throughout a portion of its length and provided with a plurality of liquid outlet jets extending to the surface of the bottom at spaced intervals in the reinforced portion thereof, an inclined end surface of reinforced material joined to the reinforced portion of the bottom surface and provided with a plurality of similar liquid outlet jets extending to the surface at spaced intervals thereof, means for supplying controlled amounts of liquid under pressure to said liquid outlet jets, a plurality of porous drain channels formed integral with the solid bottom surface and positioned at spaced intervals in the reinforced portion thereof, and means for introducing a mass of molten slag onto the inclined end surface of said pit from an initial pouring head sufficient to spread the slag in a unidirectional flow across the portion of the bottom surface containing the liquid outlet jets and substantially across the remainder of the bottom surface of the pit.

3. Apparatus for use in carrying out an operation of the type in which molten slag is contacted with a liquid capable of vaporizing under the influence of heat contained in the slag and in which vapor produced as a result of contact of the slag and liquid causes swelling of the slag with the production of a porous plastic mass of bank slag of substantially greater volume than the volume of the molten slag, which comprises a foaming pit having a solid bottom surface of substantially moisture impervious material and provided throughout a portion of its length with a plurality of liquid outlet jets extending to the surface of the bottom at spaced intervals thereof, an inclined end surface of solid material joined to the bottom surface adjacent the liquid outlet jets and extending from the bottom surface at a slope of not less than one foot in three feet of length, said end surface having a plurality of similar liquid outlet jets extending to the surface at spaced intervals thereof, means for supplying controlled amounts of liquid under pressure to said liquid outlet jets, a plurality of porous drain channels formed integral with the solid bottom surface and positioned at spaced intervals adjacent the liquid outlet jets, and means for introducing a mass of molten slag onto the inclined end surface of said pit from an initial pouring head sufiicient to move the slag in a unidirectional flow across the portion of the bottom surface containing the liquid outlet jets and substantially across the remainder of the bottom surface of the pit.

4-. Apparatus for use in carrying out an operation of the type in which molten slag is contacted with a liquid capable of vaporizing under the influence of heat contained in the slag and in which vapor produced as a result of contact of the slag and liquid causes swelling of the slag with the production of a porous plastic mass of bank slag of substantially greater volume than the volume of the molten slag, which comprises a foaming pit having a bottom surface of dense concrete reinforced throughout a portion of its length and provided with a plurality of liquid outlet jets embedded in the reinforced portion of the bottom surface and extending to the surface of the bottom at spaced intervals thereof, an inclined end surface of reinforced concrete joined to the reinforced portion of the bottom surface and provided with a plurality of similar liquid outlet jets extending to the surface at spaced intervals thereof, means for supplying controlled amounts of liquid under pressure to said liquid outlet jets, a plurality of porous drain channels formed integral with the reinforced portion of the bottom surface and positioned at spaced intervals adjacent the liquid outlet jets, an inclined concrete end surface joined to the opposite end of the bottom surface, and means for introducing a mass of molten slag onto the end surface containing the liquid outlet jets in such volume and from an initial pouring head sufficient to spread the slag in a unidirectional flow across the portion of the bottom surface containing the liquid outlet jets and onto the remainder of the bottom surface with at least a portion of the slag overflowing the opposite end surface of the pit.

5. The method of treating molten slag by contact with a liquid capable of vaporizing under the influence of heat contained in the slag to cause swelling of the slag with the production of a porous mass of foamed slag having a substantially greater volume than the volume of the molten slag, which comprises pouring a mass of molten slag onto an inclined ramp and providing a continuous supply of foaming liquid from beneath the descending mass of molten slag and directed under pressure into the molten slag during the entire pouring operation from outlet jets opening onto the surface of the inclined ramp to initiate substantial foaming within the slag on the inclined ramp, flowing the foaming mass of molten slag from the inclined ramp by means of gravity flow into a pit having a substantially moisture-impervious bottom surface, initially introducing foaming liquid directly into the pit through outlet jets provided at the surface of the pit bottom to provide a relatively shallow layer of foaming liquid over the entire bottom surface of the pit prior to the introduction of the molten slag therein, progressively flowing the slag across the bottom of the pit under its own momentum in a substantially uni-directional flow preceded by a thin wall of foaming liquid while introducing additional controlled amounts of foaming liquid directly into the slag from the outlet jets provided at the surface of the pit bottom, and relatively gently arresting the motion of the slag flow to permit complete foaming thereof through the' action of foaming liquid entrapped beneath and within themass of slag, arrestment of the motion of the moving mass of slag being effected by permitting the forward portion of the moving mass to mount a relatively gently inclined slope provided at the output end of the pit with at least a portion of the slag and foaming liquid overflowing the slope and foaming on the ground adjacent the pit, thereby avoiding backwash of foaming liquid and slag within the pit.

References Cited in the file of this patent UNITED STATES PATENTS 1,865,367 Gorsuch June 28, 1932 2,000,484 James May 7, 1935 2,024,308 Schol Dec. 17, 1935 2,210,999 Bartholomew Aug. 13, 1940 2,212,962 Stuart et al. Aug. 27, 1940 2,443,103 Gallai-Hatchard June 8, 1948 FOREIGN PATENTS 273,519 Germany May 6, 1914 563,655 Great Britain Aug. 24, 1944

Claims

1. APPARATUS FOR USE IN CARRYING OUT AN OPERATION OF THE TYPE IN WHICH MOLTEN SLAG IS CONTACTED WITH A LIQUID CAPABLE OF VAPORIZING UNDER THE INFLUENCE OF HEAT CONTAINED IN THE SLAG AND IN WHICH VAPOR PRODUCED AS A RESULT OF CONTACT OF THE SLAG AND LIQUID CAUSES SWELLING OF THE SLAG WITH THE PRODUCTION OF POROUS PLASTIC MASS OF BANK SLAG OF SUBSTANTIALLY GREATER VOLUME THAN THE VOLUME OF THE MOLTEN SLAG, WHICH COMPRISES A FORMING PIT HAVING A SOLID BOTTOM SURFACE OF SUBSTANTIALLY MOISTURE IMPERVIOUS MATERIAL AND PROVIDED THROUGHOUT A PORTION OF ITS LENGTH WITH A PLURALITY OF LIQUID OUTLET JETS EXTENDING TO THE SURFACE OF THE BOTTOM AT SPACED INTERVAS THEREOF, AN INCLINED END SURFACE OF SOLID MATERIAL JOINED TO THE BOTTOM SURFACE ADJACENT THE LIQUID OUTLET JETS AND PROVIDED WITH A PLURALITY OF SIMILAR LIQUID OUTLET JETS EXTENDING TO THE SURFACE AT SPACED INTERVALS THEREOF, MEANS FOR SUPPLYING A CONTROLLED AMOUNT OF LIQUID UNDER PRESSURE TO SAID LIQUID OUTLET JETS, A PLURALITY OF POROUS DRAIN CHANNELS FORMED INTEGRAL WITH THE SOLID BOTTOM SURFACE AND POSITION AT SPACED INTERVALS ADJACENT THE LIQUID OUTLET JETS, AND MEANS FOR INTRODUCING A MASS OF MOLTEN SLAG ONTO THE INCLINED END SURFACE OF SAID PIT FROM AN INITIAL POURING HEAD SUFFICIENT TO SPREAD THE SLAG IN A UNIDIRECTIONAL FLOW ACROSS THE PORTION OF THE BOTTOM SURFACE CONTAINING THE LIQUID OUTLET JETS AND SUBSTANTIALLY ACROSS THE REMAINDER OF THE BOTTOM SURFACE OF THE PIT.

5. THE METHOD OF TREATING MOLTEN SLAG BY CONTACT WITH A LIQUID CAPABLE OF VAPORIZING UNDER THE INFLUENCE OF HEAT CONTAINED IN THE SLAG TO CAUSE SWELLING OF THE SLAG WITH THE PRODUCTION OF A POROUS MASS OF FORMED SLAG HAVING A SUBSTANTIALLY GREATER VOLUME THAN THE VOLUME OF THE MOLTEN SLAG, WHICH COMPRISES POURING A MASS OF MOLTEN SLAG ONTO THE INCLINED RAMP AND PROVIDING THE CONTINUOUS SUPPLY OF FOAMING LIQUID FROM BENEATH THE DESCENDING MASS OF MOLTEN SLAG AND DIRECTED UNDER PRESSURE INTO THE MOLTEN SLAG DURING THE ENTIRE POURING OPERATION FROM OUTLET JETS OPENING ONTO THE SURFACE OF THE INCLINED RAMP TO INTIATE SUBSTANTIAL FOAMING WITHIN THE SLAG ON THE INCLINED RAMP, FLOWING THE FOAMING MASS OF MOLTEN SLAG FROM THE INCLINED RAMP BY MEANS OF GRAVITY FLOW INTO A PIT HAVING A SUBSTANTIALLY MOISTURE-IMPREVIOUS BOTTOM SURFACE, INTIALLY INTRODUCING FOAMING LIQUID DIRECTLY INTO THE PIT THROUGH OUTLET JETS PROVIDED AT THE SURACE OF THE PIT BOTTOM TO PROVIDE A RELATIVELY SHALLOW LAYER OF FOAMING LIQUID OVER THE ENTIRE BOTTOM SURFACE OF THE PIT PRIOR TO THE INTRODUCTION OF THE MOLTEN SLAG THEREIN, PROGESSIVELY FLOWING THE SLAG ACROSS THE BOTTOM OF THE PIT UNDER ITS OWN MOMENTUM IN A SUBSTANTIALLY UNI-DIRECTIONAL FLOW PRECEDED BY A THIN WALL OF FOAMING LIQUID WHILE INTRODUCING ADDITIONAL CONTROILLED AMOUNTS OF FOAMING LIQUID DIRECTLY INTO THE SLAG FROM THE OUTLET JETS PROVIDED AT THE SURFACE OF THE PIT BOTTOM, AND RELATIVELY GENTLY ARRESTING THE MOTION OF THE SLAG FLOW TO PERMIT COMPLETE FOAMING THEREOF THROUGH THE ACTION OF FOAMING LIQUID ENTRAPPED BENEATH AND WITHIN THE MASS OF SLAG, ARRESTMENT OF THE MOTION OF THE MOVING MASS OF SLAG BEING EFFECTED BY PERMITTING THE FORWARD PORTION OF THE MOVING MASS TO MOUNT A RELATIVELY GENTLY INCLINED SLOPE PROVIDED AT THE OUTPUT END OF THE PIT WITH AT LEAST A PORTION OF THE SLAG AND FOAMING LIQUID OVERFLOWING THE SLOPE AND FOAMING ON THE GROUND ADJACENT THE PIT, THEREBY AVOIDING BACKWASH AND FOAMING LIQUID AND SLAG WITHIN THE PIT.