US1402363A - Method of casting slag - Google Patents

Description

W. T. HURST.

METHOD OF CASTING SLAG.

APPLICATION FILED NOV. 29, 1919.

Patented Jan. 3,- 1922,

ENVEN'WMR FELL lTED STATES WILLIS T. BURST, or PITTSBURGH, PENNSYLVANIA, 'Ass1G1ton. -To SLAG iaooxl MACHINE COMPANY, or PITTSBURGH, PENNSYLVANIA, A. congonarroit or PENNSYLVANIA.

METHOD or CASTING SLAG.

Patented Jan. 3, 11922.

Application filed November 29, 1919. Serial No. 341,478.

To all whom it may concern:

Be it known that I, VILLIS T. HURsT, a resident of Pittsburgh, in the county of Allegheny and State of Pennsylvania, have invented a new and useful Improvement in Methods of Casting Slag, of which the following is a specification.

This invention relates to the handling of slag -'from blast furnaces. The particular objects of the invention are to handle such slag as fast as it is produced and drawn off, and in such manner that it is reduced in the handling to a hard dense product suitable for use as ballast for railroads, the construction of streets and highways, as an ingredient of concrete, and in general any use to which broken stone or gravel may be put. In general the method consists in cooling the slag quickly in thin layers, said layers being of a predetermined thickness depending on the time available for cooling. The latter element in turn depends on the time elapsing between flushings of the furnace.

Furnace slag is disposed of in a number of different ways. For example it is reduced to granular form by plunging it into water. Or it may be transported in slag cars to a dump, where it is allowed to cool normally in the air. This results in a slag that is light and porous. By the-method of the present invention slag is sotreated that when cold it is reduced to a dense hard mass having very nearly the physical properties of stone, and therefore useful for purposes to which crushed stone may be applied.

The drawings show diagrammatically a form of apparatus suitable for carrying out the method. Fig. 1 is a plan view of a layout suitable for cooling slag from a single blast furnace; and Fig. 2 is a vertical section on the line 2-2 of Fig. 1.

The slag is led from a furnace by a runner. In the present case this runner is divided into troughs 1 and 2, the first of which is used to receive slag when taking a cast from the furnace while the other, 2, is used to receive slag when it is tapped off from the cinder notch. In the runner 1 is a separator 3 which serves to catch any molten iron that may still remain in the slag. This is necessary in order to prevent the burning of the molds or pans hereinafter described and also to prevent the slag from sticking thereto. The slag overflows into the runner 4, which communicates with branch runners 5 and 6. These branches carry the molten slag to the several-cooling receptacles below described. A gate or deflector 7 is placed at the point where the runner 4 enters the branches 5 and 6, and this may be used to direct the necessary quantity of slag into each branch. A wall 8 forms a pit which is preferably divided by cross walls 9 into a series of compartments 10 in each of which water is maintained at a predetermined height. A series of receptacles 11, formed of sheet metal or the like, are floated in these compartments. These receptacles may be in the form of pans, molds or boxes, and preferably are of such dimensions that four of them will take all of the slag coming from a single flushing of the furnace without getting too great a depth of slag in each pan, although different numbers may be used.

Preferably these receptacles are in the form of pans, having their side and end walls flared slightly, so that the solidified slag will be discharged therefrom when they are turned upside down. These pans normally float in the tanks 10. The branch runners or gutters 5 and 6 extend along the tops of the dividing walls 9 to substantially midway thereof, and at their ends are provided with spouts 12,which project over the edges of the dividing walls and into position to discharge the molten slag into the middle portions of the receptacles 11, as illustrated. At the junction of each of the spouts 12 with the branch runners is a de flector or valve 13, pivotally mounted at 14 and provided with a handle or other operating means 15, so that it can be moved into either of two positions, to direct the flow of molten slag first into the pan or receptacle on one side of the dividing wall and then into the pan or receptacle on the other side. The molten slag is run into one receptacle until that is filled to the desired depth, and then it is deflected and caused to flow into the other pan. As the pan is loaded it gradually sinks into the water until it comes to rest upon supports 16 in the bottom of the compartment 10. The height of the pan is such that when it has settled down upon'these supports it will not be submerged, but will be surrounded by water on its bottom and all sides. By this means the receptacle and its contents are a dump and there inverted.

subjected to a very rapid cooling. As soon as a solid crust forms over the top of the slag, water may be played over the surface by means of spray nozzles 18 from water pip-es 17 which are placed along the sides of the transverse walls 9. \Vater is not admitted to the spray pipes until the top surface of the slag has been solidified, and therefore the slag is not granulated by contact with the water as would be the case if the water were sprayed while the slag is in molten condition.

By this means, the water cooling of a comparatively thin sheet of slag exposed over its entire under surface to water cooling, and by playing water over its solidified upper surface, there is produced a quick cooling of the entire mass of slag. The result is that the mass sets in a dense, solid, hard form, and not in a porous or spongy mass such as results when such material is allowed to air cool.

\Vhen the slag is solidified the pans are removed by any suitable means, and taken to The solidified slag will drop out, due to contraction from cooling and because of the tapered shape of its containers. It is then broken into pieces and crushed to any desired size and can be utilized in many ways.

To produce this hard rock like slag by the present method, and in such manner as to continuously take care of the normal flushings of a blast furnace. there are three elements to be considered. These are the time available for cooling the slag. the depth to which it is poured in the cooling pan, and the temperature to which it is exposed.

Slag is made continuously in the reduction of ore to metallic iron and collects and rests upon the liquid iron in the hearth of the furnace. \Vhen sufiicient slag has been made it reaches the cinder notch which is located above and to the side of the iron tap-hole. The slag hole is opened and the accumulation of slag above the cinder notch is drawn off. This process is repeated two or more times between each cast of iron. 'hen the iron tap-hole is opened the liquid iron is drawn off and as the iron nears the end of the drawing off or casting period slag below the level of the cinder notch follows the iron through the iron tap-hole and is deflected from the path of the molten iron to the slag runner by means of a skimmer. The volume of slag following the iron at a cast is larger than the fiushings between casts. The intervals between castings and tlushings vary somewhat at different furnaces but the normal time between flushings is forty-five minutes minimum and two hours maximum. The longer time elapses between flushings taken just after a cast of metal has been made from the furnace. and the minimum time is just before a cast is made. In order to be commercially practical, this process of handling slag and rcducing it to a particular form, must be capable of taking care of a flushing of slag in a period of less than forty-five minutes. The average temperature of the water in this practice will be approximately 150 Fahr. and the temperature of the molten slag is nearly constant and averages close to 2500 Fahr.

In the present method the thickness of the layer of slag poured into each pan is varied according to the time that is available between flushings of the furnace. For example, when the next flushing is to occur forty-five minutes later, the slag is run into the pan in a comparatively thin layer, three to four inches; whereas if two hours are available it maybe run to a depth of approximately six inches. In the latter case the time necessary for solidification of the slag is much longer, I have determined by experiment that a layer of slag exposed to water cooling as described in this specification when poured to a thickness of four inches will require approximately thirty minutes to solidify. A thickness of six inches will require approximately ninety minutes to solidify, and a thickness of nine inches will require approximately five hundred and forty minutes to solidify. Therefore it is evident that the thickness of the layer must be varied according to the time that is available for solidification, that is before the slag must be removed to make place for the next flushing.

Consequently. in the practice of this method the slag drawn off at completion of a cast from the furnace will fill the pans to a depth of nearly six inches. and there is available nearly two hours before the next flushing will normally occur. This slag will have been solidified and may be removed after an hour and a half. As the time between normal flushings grows smaller. untiljust before the next cast it is approximately forty-five minutes. the layer of slag poured will be' made less. so that the last one will be four inches deep. or may be less. In this latter case it will have been solidified and may be removed after thirty minutes.

Thus in the practice of this method the three elements of depth of layer of slag.- time of exposure to cooling. and temperature to which exposed have to be considered. The initial temperature of the slag is nearly always the same. and the temperature of the water may be considered constant. (onscquently the depth of layer and time of exposure are the elements 'aried. Andparticularly the thickness is varied with the time element.

The pans themselves are made considerably deeper than is necessary for taking care of a four to six inch layer of slag. This is done for two reasons. First in order to prevent any water in the pits from flowing over the tops of the pans when they have settled down onto their supports, and second in order to be able to take care of an excess amount of slag such as occasionally results when the cinder notch becomes plugged and the excess of slag has to be drawn off through the iron notch of the furnace. This, however, has nothing to do with the normal practice of the invention.

I claim:

1. The method of treating molten slag t0 producea dense hard slag, consisting in pouring the molten slag into a shallowmeceptacle or mold, water cooling said receptacle or mold, and when the surface of the slag in said receptacle or mold has solidi fied, introducing water onto said surface, thereby quickly cooling the entire mass.

2. The method of treating molten slag to produce dense hard slag, consisting in separating any iron from the slag, pouring the molten slag into a pan or receptacle, and water cooling said pan or receptacle to thereby quickly cool the slag.

In testimony whereof, I have hereunto set my hand.

WILLIS T. HURST.

Witnesses:

ALICE A. TRILL,

HOWARD L. SNIVELY.

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