SLAG LADLE FOR SEPARATION AND RECOVERY OF MOLTEN IRON FROM SLAG

Abstract

In an implementation, an apparatus for separation and recovery of a molten metal (106) from a slag (108) includes a device (400) attached to a slag ladle (100). The device (400) having a lower edge (404) and free edge (402) is fitted over a part of the slag-ladle (100) holding the molten metal (106) and the slag (108). The device (400) acts as a barrier for the flow of molten iron (106) such that the slag (108) is allowed to flow over the device (400) while the molten metal (106) is retained in the slag-ladle (100). The device (400) has a sluice gate (406) and a chute (408) for indicating the flow of the slag (108) in the form of a pipe-like stream.

Description

TECHNICAL FIELD

The present subject matter relates, in general, to the field of steel making and, in particular, to separation of molten metal from slag.

BACKGROUND

Steel is made by purifying metallic iron charge in the form of, individually or in some combination of, molten pig iron, solid sponge iron and iron/steel scrap. Slag is generally produced as a waste by-product during the steel-making process. Slag occurs in a molten state and is essentially a mixture of various oxides of silicon, calcium, iron and other metals. Molten refined steel is obtained by separating the slag from the molten refined steel at the end of the steel-making process. Effective steel-making process requires that at the end of the process, the molten refined steel is separated cleanly from the slag for further processing of molten refined steel either by direct casting or by secondary refining and then casting. The process of separation of slag varies with different steel-making processes. For instance, in an electric arc furnace process, most of the slag is separated during the steel-making operation itself whereas in a converter process, the slag remains with the molten refined steel during the steelmaking-operation and is separated at the end by tapping selectively the molten refined steel. Also, materials having density higher than that of density of slag but lower than that of density of molten refined steel are used for effective separation of slag. However, it is not possible to cleanly separate the slag from the molten refined steel in either of the steel-making processes described above. During the separation of slag, a small amount of molten refined steel is allowed to remain with the slag. The slag, thus separated from the molten refined steel, contains a perceptible amount of molten iron in the form of partially or fully refined steel. Thus, there is a net loss of iron in the steel making process.

Various processes have been developed to recover the iron that inevitably goes with the slag. These processes typically recover the iron after the mixture of slag and iron has been cooled and solidified. For example, the separated slag is poured in slag pits and is subsequently allowed to cool and solidify naturally or by spraying cold water on the dumped slag. As a result, boulders are formed entrapping iron in the solidified slag due to the subsequently allowed to cool and solidify naturally or by spraying cold water on the dumped slag. As a result, boulders are formed entrapping iron in the solidified slag due to the development of mechanical and chemical bonds between the slag and iron. The entrapped iron is recovered from the solidified slag by first crushing the solidified slag to a suitable size to liberate the iron particles from the solidified slag, and by subsequent magnetic separation of the liberated iron from the non-magnetic slag. However, it is not possible to liberate all the iron particles from the solidified slag as some slag invariably remains attached with the magnetically separated iron particles. Thus, the magnetically separated iron is invariably contaminated with slag. Equally a part of iron remains attached with the main bulk of the solidified slag and goes finally to waste. Further, during cooling and solidification of the slag, some part of iron is lost due to oxidation.

Furthermore, the solidified slag can not be ground to fine particles to better recover the iron particles as there is an economically acceptable limit for grinding the solidified slag so that the separated iron can be reused as a source of iron-metallic in the steel-making furnace. Thus, the process of iron separation and recovery by the magnetic separation results in only 60-70 percent recovery of useful iron contained in the solidified slag. The remaining iron is practically lost in the wasteful slag, without any more possibility of its economic recovery.

Moreover, the magnetic separation process of recovering iron from the solidified slag is quite cumbersome and costly due to the requirements of installation and operation of magnetic separation plant of considerable size, land for such installation, considerable amount of power, and other mechanical and human resources. Also, the crushing of the solidified slag and its handling causes attendant pollution problems.

SUMMARY

This summary is provided to introduce concepts related to slag-ladle for the separation and recovery of molten iron from slag, which is further, described below in the detailed description with respect to steel-making process. It should be understood that the same concepts can be extended to separation and recovery of any other metal or non-ferrous metal from slag in molten conditions during any of smelting and refining operations. The separation of the iron from the slag in molten conditions is achieved by attaching a device to a slag-ladle and modifying the process of slag pouring in pits. In an implementation, the slag-ladle typically used for separation and recovery of iron is modified. The device takes into consideration the differential forces of surface tensions, densities, viscosities, and fluid flow characteristics of slag and molten iron in the slag.

Method(s) and an apparatus for separation of iron from slag during molten conditions are described herein. In an implementation, a device is attached on to an edge of the slag-ladle, which is used for separation of molten slag and recovery of molten iron from the molten slag. The device differentiates the momentums of flow of molten slag and molten iron during slag pouring process and prevents the flow of molten iron associated with the molten slag along with the flow of molten slag during the slag pouring process and collection process thereafter.

This summary is not intended to identify essential features of the claimed subject matter nor is it intended for use in determining or limiting the scope of the claimed subject matter.

BRIEF DESCRIPTION OF THE DRAWINGS

The detailed description is described with reference to the accompanying figures. In the figures, the left-most digit(s) of a reference number identifies the figure in which the reference number first appears. The same numbers are used throughout the drawings to reference like features and components.

FIG. 1 illustrates a slag ladle containing the slag and the molten iron as known in the prior art.

FIG. 2 and FIG. 3 illustrate disposal of the slag and the molten iron from the slag ladle as known in the prior art.

FIGS. 4a, 4b, and 4c illustrate a device to be attached to the slag ladle, in accordance with different embodiments of the present subject matter.

FIGS. 5a, 5b, and 5c illustrate the elevated and plan view of the exemplary device, in accordance with the embodiments of FIGS. 4a, 4b, and 4c of the present subject matter.

FIGS. 6a, 6b, and 6c illustrate the elevated and plan view of the exemplary device, in accordance with the embodiments of the present subject matter.

FIG. 7 illustrates the operation of the device, in accordance with the embodiments of the present subject matter.

FIGS. 8a, 8b, 8c, and 8d illustrate the device as attached to the slag ladle, in accordance with the embodiments of the present subject matter.

FIGS. 9a, 9b, and 9c illustrate a modified slag-ladle, in accordance with yet another embodiment of the present subject matter.

FIGS. 10a, 10b, and 10c illustrate a modified device to be attached to the modified slag ladle, in accordance with the embodiments of FIG. 9a of the present subject matter.

FIGS. 11a, 11b, and 11e illustrate the elevated and plan view of the modified device, in accordance with the embodiments of FIGS. 10a, 10b, and 10c of the present subject matter.

FIGS. 12a, 12b, and 12c illustrate the elevated and plan view of the modified device, in accordance with another embodiment of the present subject matter.

FIGS. 13a, 13b, 13c, and 13d illustrate the modified device as attached to the modified slag-ladle, in accordance with the embodiments of the present subject matter.

DETAILED DESCRIPTION

Generally, two major processes of steelmaking are used for making refined steel on large scale, where both slag and refined steel are produced in clear molten state, namely the Basic Oxygen Furnace (BOF) or the Converter Process and the modern Electric Arc Furnace (EAF) process of steelmaking. In BOF process of steelmaking slag, at the end of refining, molten refined steel is tapped out through a tap hole while leaving the slag inside the furnace along with small amount of molten refined steel. The slag, along with the small amount of molten steel, is then poured in a slag-ladle for its eventual disposal. The small amount of molten steel so sacrificed during tapping goes with the slag. The amount of small amount of molten steel so sacrificed to go with the slag is minimized by the use of floats, which has a density in between that of the slag (2.5 gm/cc) and molten iron (7.5 g/cc). The float settles in between the flowing streams of the slag and the small amount of molten steel at the tap hole and minimizes flowing of slag with the molten steel. The small amount of molten steel so lost in the slag is recovered universally by the magnetic separation process after cooling and solidification of the slag.

In EAF process of steelmaking, the slag is allowed to flush out of the furnace during the refining operation itself. However, small amount of molten steel gets mechanically entrapped and entrained with flushing slag. The small amount of molten steel thus ends up with the slag that is collected. Additionally, floats as described above are used to minimize flowing of slag with small amount of molten steel. Alternatively, certain sizable proportion of refined steel is allowed to stay back, along with the leftover slag in the EAF, to act as the heel, for the next heat. But again, some small amount of molten steel always ends up in the flushing slag that is produced.

In both the processes, the molten refined steel and the slag are not clearly obtained as two physically distinct products. The slag along with small amount of molten iron, in the form of the molten refined steel, is collected in a slag-ladle and transported to a slag pits for subsequent separation and recovery of the small amount of molten iron. The slag-ladle is tilted on one side with the ladle axis in the vertical plane such that the slag flows over the lower edge of the slag-ladle. The slag-ladle is tilted continually till the slag-ladle is turned almost upside down and the slag is completely dumped into the slag pits. The term iron in the slag that is used is to denote essentially the metallic iron of whatever composition as distinct from the slag containing only the oxides.

FIG. 1 illustrates a typical slag-ladle 100 in an erect position along with the ladle-axis 102 as vertical and apparent ladle edges 104a and 104b. The apparent ladle edges 104a and 104b appear as surface 104 in the plan view. The slag-ladle 100 is a massive steel construction. In normal vertical position of the slag-ladle 100, molten iron 106, being heavier, settles at the bottom and the slag 108, being relatively lighter than the molten iron 106, settles above the molten iron 106. The molten iron 106 and the slag 108 are immiscible liquids and hence appear as two distinct layers one below the other because of their widely different densities. The molten iron 106 and the slag 108 will always take the shape of the slag-ladle 100 while maintaining a top surface level 110 as always horizontal with respect to their heights in the slag-ladle 100.

FIG. 2 illustrates the tilting of the slag-ladle 100 for pouring of the molten iron 106 and the slag 108 into a slag pit. The tilting of the slag-ladle 100 results in slowly changing the shape taken by the molten iron 106 and the slag 108 in the slag-ladle 100, while maintaining the top surface level 110 as always horizontal due to basic physical properties of liquids. Due to the difference in densities of the molten iron 106 and slag 108, the molten iron 106 will always remain at the bottom of the slag-ladle 100 and the slag 108 will remain on top of the molten iron 106. The continued tilting of the slag-ladle 100 causes the slag 108 to reach the lowermost open top-edge-tip 112 of the slag-ladle 100 first. Further tilting of the slag-ladle 100 results in an outflow of the slag 108 from the slag-ladle 100. The more the slag-ladle 100 is tilted, the more will be the rate of flow of the slag 108 from the slag-ladle 100. The molten iron 106 shall always remain below the slag 108 while maintaining a top surface of the molten iron 106 and a top surface of the slag 108 as always horizontal.

With further increase in the tilting and subsequent outflow of the slag 108, the top surface of the molten iron 106 reaches the lowermost open top-edge-tip 112 of the slag-ladle 100 at a specific angle of tilt depending upon the actual amount of molten iron 106 in the slag-ladle 100 and the design of the slag-ladle 100. At this specific angle of tilt, the apparent ladle-wall edges 104a and 104b in the vertical plane containing the ladle axis is almost horizontal, as illustrated in FIG. 3. Any further tilt of the slag-ladle 100 results in flowing of the molten iron 106 from the slag-ladle 100 and with a higher momentum of flow than the momentum of flow of slag 108 due to the differences in densities and viscosities. The tilting of the slag-ladle 100 is continued till all the molten iron 106 is poured out, albeit along with some of the slag 108. As a result, a small part of the slag 108 may lag behind and flow out even after the molten iron 106 has fully flown out because of high viscosity of the slag 108. Typically, the pouring of the molten iron 106 and the slag 108 takes place very rapidly and are completed in a very short duration.

This process of pouring the slag 108 and the molten iron 106 together results in intermixing of the two immiscible liquids in the slag pit. The extent of intermixing of the molten iron 106 and slag 108 differs from case to case. The extent of intermixing depends upon the process of pouring the slag 108 and various parameters, such as height of the slag-ladle 100 above the ground, rate of tilting, rate of cooling, relative proportion of molten iron 106 and slag 108, and so on. Water spray is used to cool the slag 108 faster to the extent otherwise possible. Additionally the slag 108 is turned upside down several times with a shovel to hasten the cooling and solidification of the slag 108. All these factors result in development of mechanical and few chemical bonding between the slag 108 and the molten iron 106, resulting in formation of boulders of the slag 108 with specific gravity in between that of the slag 108 and molten iron 106. Further, a part of the molten iron 106 gets oxidized on its exposure to atmospheric oxygen and water spray. The semi-hot slag 108 boulders are transported to a slag yard, where the slag 108 is cooled to room temperature and then subjected to further processing, such as magnetic separation of iron from the cooled slag 108. For magnetically separating iron from the cooled slag 108, the cooled slag 108 is crushed to liberate iron particles contained therein and the crushed slag 108 is then subjected to magnetic separation of the iron from the non-magnetic slag 108. As the iron particles are distributed in the crushed slag 108, the entire mass of the crushed slag 108 is subjected to magnetic separation. This traditional process of slag cooling, transportation, crushing and subjecting the slag 108 to magnetic separation is a time consuming, power consuming, cumbersome, ineffective and inefficient process. Also a large magnetic separation plant with equally large-power requirements is required for this process of iron recovery by magnetic separation, thereby making the entire process very costly.

Further, during the magnetic separation, magnetic oxide of iron is formed due to oxidation of molten iron 106 while the slag 108 is being cooled in open atmosphere with water spray. The magnetic oxide of iron thus formed tends to be a part of slag 108 like other oxides in the mass of the slag 108. Due to the magnetic nature of the magnetic oxide of iron, the magnetic oxide of iron picked up along with the iron as a magnetic fraction during the magnetic separation. This magnetic oxide of iron therefore erroneously increases the weight of iron recovered from magnetic separation and subsequently inflates the iron recovery figures and the attendant costs of payment for iron.

Furthermore, the process of magnetic separation for the recovery of iron from slag 108 is practiced in a retrograde process, i.e., after cooling and solidification of the molten iron 106 and the slag 108 mixture. Also, some part of iron gets oxidized during cooling and is therefore lost in the slag 108 as its own constituent. Additionally, the formation of magnetic oxide tends to blur the demarcation of magnetic iron and non-magnetic slag 108, at least to some extent, thereby making clean iron separation more difficult. Moreover, some part of the total iron 106 is left in solid slag 108 and is finally lost with the remaining slag 108 as the iron can not be economically recovered by the magnetic separation process.

To overcome all the disadvantages as stated above, an apparatus and a method in accordance with the present subject matter is designed to recover the molten iron 106 or any other metal, from the slag 108 in a molten state when both the molten iron 106 and slag 108 exist almost as two distinct phases in the slag-ladle 100. The apparatus, according to the present subject matter, comprises a device fitted over a part of a top-edge of the slag-ladle 100. The apparatus is designed for separation and recovery of molten iron 106 or any other metal from the slag 108. The method, according to the present subject matter, ensures that the molten iron 106 and slag 108 are separated before they get intermixed during the process of pouring the slag 108. This method of separation and recovery of the molten iron 106 from the slag 108 in the molten state is based on differential forces of surface tensions, densities, viscosities, and fluid flow characteristics of the molten iron 106 and the slag 108. Due to these differential forces, relatively different momentums of fluid flow of molten iron 106 and the slag 108 are generated during the process of pouring the slag 108. With the attachment of the device, as designed in accordance with one embodiment of the present subject matter, on to the slag-ladle 100, and by suitably modifying the traditional process of pouring the slag 108, molten iron 106 and slag 108 can be effectively separated as two almost fairly distinct products such that one product consists of essentially most of the slag 108 and other product consists of essentially all the molten iron 106 along with small amount of slag 108.

Exemplary Device

The device in accordance with the present subject matter is designed to develop differential momentums of the flow of slag 108 and of molten iron 106 by restricting the flow of the molten iron 106 along with the slag 108 during the process of pouring the slag 108 in slag pits for cooling and solidification. The device is designed such that when the device is attached to the slag-ladle 100, and when in operation, the device suitably and partially closes the circular opening of the slag-ladle 100, so as to relatively decrease the momentum of flow of molten iron 106 while allowing the slag 108 to gain momentum. Thus, the device creates a partial barrier for the molten iron 106 such that the molten iron 106 is retained in the slag-ladle 100 while the slag 108 flows over the barrier. Further, when most of the slag 108 has flown out of the slag-ladle 100, the device then acts as a chute to allow the flow of molten iron 106 into the required mould for its collection as almost a separate product, fairly free of slag.

The device, in accordance with one embodiment of the present subject matter, is designed such that the device is defined by two distinct edges, a lower edge and an open edge. The lower edge is designed in a circular profile such that the circular profile conforms to shape, size, and dimensions of a pre-determined segment of an open top-edge of the slag-ladle 100. In one implementation, the open top-edge of the slag-ladle 100 is circular in shape. The pre-determined segment of the top-edge of the slag-ladle 100 is the place from where the slag 108 flows out of the slag-ladle 100 upon tilting as described earlier. The lower edge of the device is then attached securely at the pre-determined segment of the top-edge of the slag-ladle 100. The open edge of the device, hereinafter referred to as the free edge, may be designed as having one of a straight profile, circular profile, and a profile having a plurality of short edges or a multi-hedral profile. The height of the device is defined as the maximum distance between the free edge and the lower edge in a vertical plane, when attached to the slag-ladle 100 and in operation. In another embodiment of the present subject matter, the device may be designed such that the lower edge has a flat profile and the free edge has one of the straight profile, the circular profile, and the profile having a plurality of short edges.

FIGS. 4a, 4b, and 4c illustrates the isometric view of a device 400 with three probable profiles in accordance with one embodiment of the present subject matter. However, it is to be understood that various other profiles can be used, and that the profile of the device can vary according to the requirements of the slag-ladle 100 used at different plants.

FIG. 4a illustrates the isometric view of the device 400 with a free edge 402 having a straight profile and a lower edge 404 having a circular profile. The area covered by the device 400 is essentially a pre-determined segment of the top-edge of the slag-ladle 100 defined by a certain secant. The straight-line length of the free edge 402 of the device 400 having the straight profile is equal to the size and shape of the secant of the top-edge of the slag-ladle 100. The circular profile of the lower edge 404 of the device 400 is equal in shape and size to the top-edge of the slag-ladle 100. A small open sluice gate 406 having one of a square, a rectangular, and a semi-circular cross section, is provided at the centre of the free edge 402 of the device 400. The sluice gate 406 is very useful to identify the near-end of only the flow of slag 108 and the beginning of the flow of molten iron 106 from of the slag-ladle 100 during tilting, for preventing the flow of molten iron 106 with the slag 108 into the slag pit. In one implementation, two sluice gates at suitable distance from each other are provided on the free edge 402 of the device 400 in an instance when volume of the molten iron 106 is proportionally higher than volume of the slag 108. In another implementation, the device 400 is designed without any sluice-gate 406 for smaller sizes of slag-ladle 100. In such implementation, the free edge 402 is designed having a circular profile in stead of a straight profile for joining smoothly with the top-edge of the slag-ladle 100 and for controlling over-flow of the slag 108 over the free edge 402.

The sluice gate 406 is provided with a small chute 408 conforming to the shape of sluice gate 406 and projecting outwards from the sluice gate 406. The chute 408 is required for pouring the molten iron 106 in mould to collect the molten iron 106 and cast the molten iron 106 into massive ingots. The chute 408 helps to direct the stream of falling molten iron 106 into the mould where the molten iron 106 will solidify into the shapes and weights of desired iron ingots. The chute 408 is designed such that the molten iron 106 flows out smoothly and in entirety on tilting of the slag-ladle 100 without any hindrance. The mould may be then lifted and inserted for collection of molten iron 106 by the use of a separate carrier designed and operated for the same purpose.

In yet another implementation, the free edge 402 of the device 400 may be designed having a beaker-edge profile to enable pouring of the molten iron 106 into the moulds in a more directed way. In such implementation, a conical portion in the centre of the beaker-edge profile acts as a chute. The beaker-edge profile of the device 400 is useful when the slag 108 has a low viscosity and the volume of the molten iron 106 is relatively smaller than the volume of the slag 108.

FIG. 4b illustrates the isometric view of the device 400 with the free edge 402 having a circular profile. In the circular profile, the free edge 402 of the device 400 is blown up such that the shape of the free edge 402 is changed from a straight edge to a circular edge of appropriate dimensions with appropriate slope of the face of the device 400 for joining smoothly with the top-edge of the slag-ladle 100. The lower edge 404 of the device 400 is designed having a circular profile conforming to a circular top-edge of the slag-ladle 100. Further, the sluice gate 406 having the chute 408 is provided at the center of the free edge.

FIG. 4c illustrates the isometric view of the device 400 with the free edge 402 having a multi-hedral profile. In the multi-hedral profile, the free edge 402 of the device 400 is modified such that the shape of the free edge 402 is changed from circular to a shape having a plurality of straight lines joined together to form a curved length of the free-edge 402. The free edge 402 may also be made circular at the ends for joining smoothly with the top-edge of the slag-ladle 100. The lower edge 404 of the device 400 is designed having a circular profile conforming to a circular top-edge of the slag-ladle 100. Further, the sluice gate 406 having the chute 408 is provided at the center of the free edge.

FIG. 5a illustrates the elevated view 500 and the plan view 502 of the device 400 with the free edge 402 having a straight profile attached to the circular top-edge of the slag-ladle 100.

FIG. 5b illustrates the elevated view 504 and the plan view 506 of the device 400 with the free edge 402 having a circular profile attached to the circular top-edge of the slag-ladle 100.

FIG. 5c illustrates the elevated view 508 and the plan view 510 of the device 400 with the free edge 402 having a multi-hedral profile attached to the circular top-edge of the slag-ladle 100.

In another embodiment of the present subject matter, a collar can be provided on the device 400. During the pouring of molten iron 106, the collar may be useful for better and efficient pouring of the molten iron 106 when the amount of molten iron 106 in the slag 108 is large. In such embodiment, the collar can be a segment of a cylindrical shape whose diameter conforms to the circular top-edge of the slag-ladle 100 and to the lower edge 404 of the device 400 having a circular profile. However, the collar can be of any suitable design according to the shape of the device 400. The collar can be attached separately to the device 400 using any method known in the art, or the collar can be provided with the device 400 during manufacturing the device 400. The collar can be designed such that the collar is firmly attached to the top-edge of the slag-ladle 100 at the pre-determined segment from where slag 108 flows out during the pouring of slag 108. The curved length of the collar should conform to the length of the free edge 402 of the device 400 such that the collar is securely attached to the device 400. In one implementation, the collar is first securely attached to the slag-ladle 100 and then the device 400 is securely attached to the collar.

FIG. 6a illustrates the elevated view 600 and the plan view 602 of the device 400 with the free edge 402 having a straight profile and a collar 604 attached to the circular top-edge of the slag-ladle 100.

FIG. 6b illustrates the elevated view 606 and the plan view 608 of the device 400 with the free edge 402 having a circular profile and the collar 604 attached to the circular top-edge of the slag-ladle 100.

FIG. 6c illustrates the elevated view 610 and plan view 612 of the device 400 with the free edge 402 having a multi-hedral profile and the collar 604 attached to the circular top-edge of the slag-ladle 100.

The device 400 may be securely attached with the slag-ladle 100 by using suitable methods known in the art, such as welding, riveting, bolting, and so on. The device 400 may be replaced as and when the device 400 gets damaged. In one implementation, the device 400 is securely attached with the slag-ladle 100 at the apparent ladle edge 404b over which the slag 108 flows on tilting. It is symmetrical with respect to the imaginary point, where the vertical plane in which the axis of the slag-ladle 100 rotates, cuts the lower part of the apparent ladle edge 404b during tilting. The thickness of the device 400 may be equal to or less than the thickness of the wall of the slag-ladle 100. Height 407 of the device 400 may be conformed to the design and capacity of the slag-ladle 100 and the amount of molten iron 106 to be separated and recovered from the slag 108. Further, the height 407 of the device 400 should be such that the amount of the molten iron 106 present with the slag 108 is contained in the slag-ladle 100 until the apparent conical edge of the slag-ladle 100 on a lower side in a tilted position is almost horizontal. This amounts, that the volume contained by the slag-ladle 100 and the horizontal plane passing through the bottom edge of the sluice gate 406 of the device 400 shall contain whole of the molten iron 106 inside the ladle, while allowing most of the slag 108 to flow out. Furthermore, the circular profile of the lower edge 404 of the device 400 is made to conform to the circular top-edge of the slag-ladle 100.

The sluice gate 406 placed at the center of the free edge 402 of the device 400 is designed in relation to the capacity of the slag-ladle 100 and the amount of the molten iron 106 present within the slag-ladle 100. The molten iron 106 flows out of the sluice gate 406 into the mould meant to collect the separated molten iron 106. The size of the sluice gate 406 is designed to ensure that all the molten iron 106 flows out into the mould on further tilting without spilling over the molten iron 106 into the already separated slag 108 and in a shortest possible time. This design ensures avoidance of delay fraught with danger of solidification of some of the molten iron 106 in the slag-ladle 100.

The device 400 may be manufactured using the same material as of the slag-ladle 100 such that the service life of the device 400 may be equal to that of the slag-ladle 100. The device 400 may be manufactured as an assembly of various parts including the slag-ladle 100 or may be manufactured in the form of a modified design as an integral part of the slag-ladle 100 depending upon the various design parameters of slag-ladle 100. The process of manufacture in either case does not have any influence on the performance of the modified slag-ladle 100.

FIG. 7 illustrates the process of pouring the slag 108 from the apparatus when the device 400 is attached in position with the slag-ladle 100. In an implementation, the device 400 is symmetrically attached to the slag-ladle 100 at the lowermost tip 112 of the slag-ladle 100, over which the slag 108 flows out in a tilted position of the slag-ladle 100. The device 400 is designed to create a critical volume space in the slag-ladle 100, defined by the lower part of the slag-ladle 100 and the imaginary horizontal plane passing through the bottom of the sluice gate 406 provided in the free-edge 402 of the device 400, at any position of the slag-ladle 100. The volume space is critical in separating the slag 108 from the molten iron 106. At a give position of the slag-ladle 100, the volume space is determined based on the height 407 of the device 400. The volume space decreases with further tilting of the slag-ladle 100. At any position of the slag-ladle 100, upon tilting of the slag-ladle 100, the slag 108 in excess of the volume space and placed above the molten iron 106 flows out of, the slag-ladle 100 over the free edge of the device 400. With further tilting of the slag-ladle 100 all the slag 108 flows out of the slag-ladle 100. The molten iron 106, being heavier, remains confined in the volume space generated by the device 400 up to the horizontal level of the bottom of the sluice gate 406. With carefully controlled tilting, molten iron 106 does not flow out upon further tilting till almost all the slag 108 flows out of the slag-ladle 100. Finally, the last remaining slag 108 flows out in a pipe-like stream only through the sluice gate 406.

As discussed in FIG. 2, the tilting of the slag-ladle 100 causes the slag 108 to flow out from over the lower-most tip 112 of the slag-ladle 100. However due to the placement of the device 400 in this position, the excess slag 108 over that occupying the space created by the ladle walls and the horizontal plane passing through the bottom of the sluice gate 406 in the device 400, flows above the device 400 on continuously increasing tilting. With further tilting the above volume space goes on decreasing. Initially, the rate of flow of slag 108 increases on tilting of the slag-ladle 100 but soon the rate of flow of slag 108 begins to decrease. At a specific angle of tilt, the rate of flow of the slag 108 over the free edge 402 of the device 400 becomes negligible. Then, the slag 108 flows out practically only through the sluice gate 406 in the form of a small pipe-like stream. The instant when the slag 108 flows through the sluice gate 406 is an indication that very little of slag 108 is left in the slag-ladle 100 and that further tilting may result in molten iron 106 flowing out through the sluice gate 406 over the chute 408. This instant marks the end of selective separation of the slag 108 by pouring out most of the slag 108 while retaining almost all molten iron 106 inside the slag-ladle 100.

As discussed in FIG. 3, at the specific angle of tilt during tilting of the slag-ladle 100, the molten iron 106 starts flowing before the remaining slag 108 because of the higher differential momentum of the molten iron 106 than the slag 108. However, when the device 400 is used, at the time when the molten iron 106 just starts flowing out of the sluice gate 406, further tilting is immediately stopped. The flow of the molten iron 106 can be visually identified immediately by an operator and the slag-ladle 100 is tilted backwards a little to prevent molten iron 106 from flowing out. The slag-ladle 100 may then be carried to the mould of desired size and shape where the molten iron 106 and the remaining slag 108 are poured into the mould to produce iron ingots. The remaining slag 108 that goes with molten iron 106 gets solidified in the mould along with the molten iron 106 and generally becomes a separate and superficial phase on the iron ingots. The slag 108 may be then chipped off from the iron ingot after their cooling and solidification. Thus, the remaining slag 108 can be separated efficiently from the molten iron 106 and the separated slag 108 is not required to be processed further for the recovery of molten iron 106 at any later stage by any other process of recovery.

In one implementation, a separate carrier may be used to insert mould in the falling stream of the slag 108, at an appropriate time, to collect the molten iron 106 in the mould along with the remaining slag 108 for producing the iron ingots. The remaining slag 108 which gets along with molten iron 106 may be chipped off after solidification of the molten iron 106, as most of the remaining slag 108 will be present only on the surface of the ingots.

After the entire process of separation of the molten iron 106 and recovery of iron in an ingot form is properly established by manual control, the entire process can be appropriately controlled by suitable automation of the process. The automated process may include the following steps in the same order as in manual process, i.e., tilting of the slag-ladle 100 for pouring the slag 108, identifying flow of the slag 108 in a pipe-like stream, stopping the tilting of slag-ladle 100, inserting a mould to collect molten iron 106 in the mould and tilting the slag ladle 100 for collecting the molten iron 106 in the mould. The automated process will ensure an effective and efficient method for separation and recovery of molten iron 106 without any perceptible loss of molten iron 106 in slag 108. Further, the automate process will avoid any human error, attendant loss of iron, and presence of extra slag 108 with the iron in the mould.

FIG. 8a illustrates the device 400 with the free edge 402 having a straight profile as attached to the slag-ladle 100.

FIG. 8b illustrates the device 400 with the free edge 402 having a straight profile and a collar as attached to the slag-ladle 100.

FIG. 8c illustrates the device 400 with the free edge 402 having a circular or multi-hedral profile as attached to the slag-ladle 100.

FIG. 8d illustrates the device 400 with the free edge 402 having a circular or multi-hedral profile with a collar as attached to the slag-ladle 100.

In accordance with one another embodiment of the present subject matter, the slag-ladle 100 can be suitably modified by providing a contour at the pre-determined segment of the top-edge of the slag-ladle.

FIG. 9a illustrate a modified slag-ladle 100 with a contour 901 having a straight profile attached to the slag-ladle 100 in accordance with one another embodiment of the present subject matter.

FIG. 9b illustrate a modified slag-ladle 100 with a contour 911 having a circular profile attached to the slag-ladle 100 in accordance with one another embodiment of the present subject matter.

FIG. 9c illustrate a modified slag-ladle 100 with a contour 921 having a multi-hedral profile attached to the slag-ladle 100 in accordance with one another embodiment of the present subject matter.

The device 400 is then attached to the contour. The lower edge 404 of the device 400 is correspondingly modified according to the profile of the contour such that the profile of the lower edge 404 conforms to the ladle edge contours for the secure fitment of the device 404 with the slag-ladle 100 as described above.

FIG. 10a illustrates the isometric view of the device 400 with the free edge 402 having a straight profile and the lower edge 404 having a straight profile conforming to the straight profile of the contour 901.

FIG. 10b illustrates the isometric view of the device 400 with the free edge 402 having a circular profile and the lower edge 404 having a straight profile conforming to the straight profile of the contour 901.

FIG. 10c illustrates the isometric view of the device 400 with the free edge 402 having a multi-hedral profile and the lower edge 404 having a straight profile conforming to the straight profile of the contour 901.

FIG. 11a illustrates the elevated view 500 and the plan view 502 of the device 400 with the free edge 402 having a straight profile and the lower edge 404 having a straight profile conforming to the straight profile of the contour 901.

FIG. 11b illustrates the elevated view 504 and the plan view 506 of the device 400 with the free edge 402 having a circular profile and the lower edge 404 having a straight profile conforming to the straight profile of the contour 901.

FIG. 11c illustrates the elevated view 508 and the plan view 510 of the device 400 with the free edge 402 having a multi-hedral profile and the lower edge 404 having a straight profile conforming to the straight profile of the contour 901.

As described earlier, in one implementation of the present embodiment, a collar may also be attached to the device 400 with a lower edge 402 having a straight profile.

FIG. 12a illustrates the elevated view 600 and the plan view 602 of the device 400 with the free edge 402 having a straight profile, the lower edge 404 having a straight profile conforming to the straight profile of the contour 901 and the collar 604 attached to the top-edge of the slag-ladle 100.

FIG. 12b illustrates the elevated view 606 and the plan view 608 of the device 400 with the free edge 402 having a circular profile, the lower edge 404 having a straight profile conforming to the straight profile of the contour 901 and the collar 604 attached to the top-edge of the slag-ladle 100.

FIG. 12c illustrates the elevated view 610 and the plan view 612 of the device 400 with the free edge 402 having a multi-hedral profile, the tower edge 404 having a straight profile conforming to the straight profile of the contour 901 and the collar 604 attached to the top-edge of the slag-ladle 100.

FIG. 13a illustrates the device 400 with the free edge 402 having a straight profile and the lower edge 404 having a straight profile conforming to the straight profile of the contour 901 as attached to the slag-ladle 100.

FIG. 13b illustrates the device 400 with the free edge 402 having a straight profile and the lower edge 404 having a straight profile conforming to the straight profile of the contour 901, and a collar as attached to the slag-ladle 100.

FIG. 13c illustrates the device 400 with the free edge 402 having a circular or multi-hedral profile and the lower edge 404 having a straight profile conforming to the straight profile of the contour 901 as attached to the slag-ladle 100.

FIG. 13c illustrates the device 400 with the free edge 402 having a circular or multi-hedral profile and the lower edge 404 having a straight profile conforming to the straight profile of the contour 901, and a collar as attached to the slag-ladle 100.

As discussed in the subject matter, the apparatus having the device 400 attached with the slag-ladle 100 and the modified process of pouring the slag 108 provides an efficient and effective method of separating and recovering almost the entire molten iron 106 present and associated with the slag 108 in the slag-ladle 100. Further, the need for the costly, cumbersome, and elaborate crushing and magnetic separation of iron from solid slag is thus completely eliminated. Additionally, the dust otherwise generated in magnetic separation process is eliminated thereby preventing any of the attendant problems of dust pollution. Thus, the slag-ladle 100 with the device 400 attached and the modified process of pouring the slag 108 paves the march on the path for development of green steel plants, in its own right. Also, the part of molten iron 106 that oxidizes during pouring of the slag 108 and its solidification is almost eliminated as the molten iron 106 is separated from the slag 108 before any possibility of oxidation during cooling and solidification in open atmosphere aided by water. Almost all molten iron 106 is recovered by the adoption of the device 400 and the modified process of process of pouring the slag 108. Also, the inevitable loss of molten iron 108 in the remaining slag 108, after the magnetic separation, is almost completely eliminated. Hence no magnetic separation of iron from solidified slag 108 is any more necessary.

Further, the modified process of pouring the slag 108 does not interfere with the steel-making process in any way. It is thus easier to adopt with the steel making processes minimizing the loss of molten iron 106 going with the final slag 108 to pits. Moreover, the electric-power consumed during crushing and magnetic separation is totally eliminated and which can bring in carbon-credit to steel plant adopting the device 400 and the modified process of pouring the slag 108 for its cooling and disposal. Furthermore, the slag-ladle 100 with device 400 and modified process of pouring the slag 108 transforms the present process of slag cooling, solidification, crushing and magnetic separation into a simple physical process of separation and recovery of molten iron 106. Also, almost all the molten iron 106 that is originally lost from the steel-making process and collected in slag-ladle 100 along with the slag 108 in molten state is recovered without practically any loss of iron in a quite inexpensive, effective, and efficient way.

Further, the device 400, as discussed in the present subject matter, helps in recovering a clean molten iron 106 present with the slag 108 without practically any loss and wastage due to atmospheric oxidation and due to unrecoverable iron in the slag 108 of the magnetic separation process. Moreover, the molten iron 106 recovered through the modified process of pouring of the slag 108 is clean and in massive lump-form without practically any contamination of the slag 108. Also, even after attaching the device 400 to the slag-ladle 100, no additional equipments are needed in the modified process of pouring the slag 108 and subsequent disposal of the slag 108.

Further, the use of the device 400 and the modified process of pouring of the slag 108 enable the recovery of that part of the molten iron 106, which oxidizes on exposure to open atmosphere during cooling and solidification of the slag 108. Similarly, that part of molten iron 106 which can not be recovered by magnetic separation, owing to the inherent inefficiency of magnetic separation, and as a result goes with the remaining slag 108 as waste, is recovered using the device 400 without any additional input of raw materials, thereby conserving corresponding amount of the raw materials for traditional iron making processes.

Although embodiments for separation of molten iron from slag have been described in language specific to structural features and/or methods, it is to be understood that the invention is not necessarily limited to the specific features or methods described. Rather, the specific features and methods are disclosed as exemplary embodiments for the separation of molten iron from slag.

Claims

1. An apparatus for separation and recovery of molten metal (106) from slag (108), the apparatus comprising:

a slag-ladle (100) to hold the slag (108) and the molten metal (106); and

a device (400) fitted over a part of a top-edge of the slag-ladle (100) to form a partial closure on the slag-ladle (100), the device (400) having a lower edge (404) conforming to an edge of the part of the slag-ladle (100) and a free edge (402), wherein the device (400)

creates a barrier for the molten metal (106) to be retained in the open-top vessel (100); and

enables flow of the slag (108) over the barrier while retaining the molten metal (106) when the slag-ladle (100) is tilted.

2. The apparatus as claimed in claim 1, wherein the device (400) is fitted firmly with the slag-ladle (100) by joining the lower edge (404) of the device (400) with the top-edge of the slag-ladle (100).

3. The apparatus as claimed in claim 2, wherein the free edge (402) of the device (400) conforms to the top-edge of the slag-ladle (100).

4. The apparatus as claimed in claim 1, wherein the device (400) is formed as an integral part of the slag-ladle (100).

5. The apparatus as claimed in claim 1, wherein the free edge (402) has a profile that is one of a straight-line profile, a circular profile, a multi-hedral profile, and a beaker profile.

6. The apparatus as claimed in claim 1, wherein the free edge (402) includes at least one sluice gate (406) to direct flow of the slag (108) and the molten metal (106).

7. The apparatus as claimed in claim 6, wherein the free edge (402) includes the at least one sluice gate (406) at the centre of the free edge (402).

8. The apparatus as claimed in 6, wherein the free edge (402) includes a chute (408) that projects outwards from the at least one sluice gate (406) to direct flow of the molten metal (106).

9. The apparatus as claimed in claim 1, wherein the device (400) comprises a collar (604) conforming to a part of the top-edge of the slag-ladle (100) such that the device (400) is attached securely with the slag-ladle (100) via the collar (604).

10. A method for separation of molten metal (106) from slag (108), the method comprising:

tilting the apparatus holding the slag (108) and the molten metal (106) in a first direction to pour the slag (108) into a slag pit;

allowing the slag (108) and the molten metal (106) to pass through a free edge (402) of the apparatus, wherein the flow is such that a barrier of the apparatus restricts the flow molten metal (106) while retaining the molten metal (106) inside the apparatus;

identifying a flow of the slag (108) in the form of a pipe-like stream;

tilting the apparatus in a second direction based on the identification of the stream of the molten metal (106) to stop the molten metal (106) from flowing into the slag pit; and

tilting the apparatus in the first direction to pour the molten metal (106) in a mould

11. The method as claimed in claim 10, wherein the apparatus comprises:

a slag-ladle (100) that holds the slag (108) and the molten metal (106); and

a device (400) fitted over a part of the slag-ladle (100) to form a barrier on the slag-ladle (100), the device (400) having a lower edge (404) conforming to an edge of the part of the slag-ladle (100) and the free edge (402), wherein the slag (108) flows over the free edge (402) of the device (400) while the barrier retains the molten metal (106) in the slag-ladle (100);