MXPA00009123A - Metal scrap submergence system for scrap charging/melting well of furnace - Google Patents

Abstract

metal scrap melting submergence device for a chargewell of a melting furnace comprises an open top chamber (116) including walls of a heat resistant material, an inlet (126) positioned in a side wall of the chamber, an outlet (124) positioned in the base of said chamber, and a sloped ramp (121) adjacent said side wall of the chamber. The ramp rises from a base (120) spirally along the chamber circumference and includes an inner wall (122) from an inner edge of the ramp. The top edge of said inner wall will be at approximately the same height as the terminal edge of the ramp.

Description

METAL SCRAP DIVING SYSTEM FOR FOUNDRY OVEN LOADING WELL BACKGROUND OF THE INVENTION The present invention is directed to a scrap immersion system of the type typically employed in metal recycling processes, particularly, the recycling of aluminum. In the recycling of metals, it is necessary to melt pieces of scrap for treatment and processing. A large portion of scrap aluminum pieces is thin-walled as a result of the mechanical forming action by which they are formed, such as filings, drills and cold rolling. The melting of thin-walled scrap parts is particularly difficult since (i) prolonged exposure to the hostile atmosphere in a traditional melting furnace results in a large oxidation loss and (ii) rapid immersion in molten metal is severely hampered due to the fact that the thin-walled scrap pieces float on the molten metal ("floating scrap"). In a typical smelting operation used to convert floating scrap into ingots, a smelting furnace is provided with a closed hearth and a connected open side well. Normally the lateral well is divided into a pump well and a smelting bay.

A pump or other metal flow inducing apparatus is placed externally to the casting bay (eg, in the pump well), and causes the molten metal to flow from the home to the casting bay. Typically, the melting bay is further divided into a loading well and a slag well. Scrap pieces of metal are fed into the casting bay, particularly in the loading well component. A variety of devices have been used in the casting bay (specifically in the loading well) to facilitate the immersion of metal scrap under the surface of the molten metal bath. There are three main types. The first includes mechanical systems consisting mainly of a rotor which creates a flow of molten metal from the upper surface. Examples of these devices are presented in U.S. Patents 3,873,305; 3,997,336; 4,128,415; and 4,930,986. The second type of systems uses a mechanical device to physically push the scrap under the surface of the melt (pit walkers / elephant legs). The third type of system depends on the shape of the chamber without rotation of a rotor to create a metal flow which immerses the pieces of scrap in the loading well. Particularly, the flow of molten metal into the loading well is manipulated in such a way that a vortex is obtained which pulls the particles from the upper surface into the bath. These systems include, for example, United States Patents 3,955,970; 3,984,234; 4,286,985 and the application serial number 08 / 784,832, each of which are incorporated herein by reference. The present invention is directed to this third type of scrap immersion system. However, the present invention is directed to a novel system which obtains a high degree of load and a high degree of recovery with minimum maintenance requirements (three important requirements). While the present invention is directed to the third type of immersion devices, the present invention contrasts the traditional design by obtaining a vortex with an initial flow with downward flow adjacent to the outer walls of the feed bay. In contrast, in U.S. Patent 4,286,985, a loading well includes an upper inlet and a lower outlet which are positioned to create a downward flow of molten metal adjacent to the side walls of the well to form a vortex. Similarly, with reference to serial number 08 / 784,832, a loading well is designed to include a singular wedge placed in one of the walls of the feed bay to create a downward flow of molten metal and vortex. In both systems, the intention of the design is to create a downward flow in the molten metal pattern as it circulates to form the vortex pattern inside the loading well. SUMMARY OF THE INVENTION Accordingly, it is a primary objective of this invention to provide a new and improved metal scrap immersion device. It is an advantage of this invention to provide a new and improved metal scrap immersion system that can operate without mechanically moving components. A further advantage of this invention is to provide a new and improved metal scrap immersion device that improves the efficiency of scrap immersion. Another advantage of this invention is to provide a new and improved metal scrap immersion device that is effective with floating pieces of scrap. A further advantage of the invention is associated with the use of an easily manufactured body with no moving parts, which provides longevity. In addition, the invention is easy to maintain and clean and minimizes the working depth of the molten metal. Further objects and advantages of the invention will be set forth in part in the description that follows and in part will be obvious in the description, or may be learned in the practice of the invention. The objects and advantages of the invention can be realized and obtained by means of the instrumentation and the combinations particularly indicated in the appended claims. In order to achieve the foregoing objects and in accordance with the purpose of the invention as embodied and broadly described herein, the scrap immersion device of this invention comprises an open chamber in the upper part including walls constructed of Generally, the chamber can be described as an arrangement with lower entrance and lower exit.A ramp is formed adjacent to the walls, spirally upwards of it.Preferably, the metal scrap immersion device will be built in a manner which places the lower edge of the ramp at the base of the chamber adjacent to the ramp In a particularly preferred form of the invention, the ramp will be spiral through at least 180 °, preferably 270 °, of The circumference of the chamber In a particularly preferred form of the invention, the ramp will include a portion that has a gradient of rca of 5o, preferably between 10 ° and 15 °. However, it should be understood that the slope may vary along the dimension of the ramp. In fact, the geometry of the preferred embodiment (cylindrical) is such that the outer edge of the ramp adjacent to the wall and the inner edge of the ramp have the same slope, but cover a slightly different distance. Therefore, the outer edge and the inner edge of the ramp will exhibit different slopes correspondingly - the outer edge will be somewhat less than the inner edge. Therefore, the future reference to the slope can be referred to the lower degree along the outer edge. In a further preferred embodiment of the invention, a wall will extend from the inner edge of the ramp, helping to define an entrance to the exit. Preferably, the upper edge of the wall will be approximately the same height as the terminal edge of the ramp. BRIEF DESCRIPTION OF THE DRAWINGS The invention consists of parts, construction, arrangements, combinations and novel improvements, shown and described.

The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate one embodiment of the invention and together with the description, serve to explain the principles of the invention. From the drawings: FIGURE 1 is a schematic representation of a molten metal recycling furnace; FIGURE 2 is a cross-sectional view of the components of the pump well and the furnace loading well of FIGURE 1; FIGURE 3 is a top plan view of the loading well of FIGURE 2; FIGURE 4 is a cross-sectional view of an alternative embodiment of the loading well of the invention; FIGURE 5 is a top plan view of the loading well of FIGURE 4. DETAILED DESCRIPTION OF THE INVENTION Reference will now be made in detail to the preferred embodiment of the present invention, for example of which is illustrated in the accompanying drawings. While the invention will be described in connection with a preferred embodiment, it will be understood that it is not intended to limit the invention to that embodiment. On the contrary, it is intended to cover all alternatives, modifications and equivalents that may be included within the spirit and scope of the invention defined in the appended claims. With reference to FIGURE 1, an aluminum recycling furnace 10 is presented. The furnace 10 includes a main home component 12 which is heated, for example, with gas or oil burners or by any other means known in the art. Adjacent and in fluid communication with the home 12, is the primary recycling area composed of a pump shaft 14, a loading well 16 and a slag pit 18. Although not shown, the walls of the hearth 12 are opened at pump well 14, to the loading well 16, to the slag well 18 and back to the hearth 12 to allow the circulation pattern indicated by the arrows 5. The pump well includes a molten metal pump of any known type for those with skill in the art. The molten metal pump circulates the molten metal from the hearth 12 to the loading well 16 where pieces of scrap to be recycled are deposited on the melt surface. Molten metal from the loading well 16 flows into the slag pit 18 where the impurities in the form of slag are removed from the surface before the melt flows back to the hearth 12. This invention in particular is directed to an improved design of the loading well 16, this being a lower entry-lower exit design. With reference to FIGURE 2, a side elevation elevation view of the pump well 14 and the loading well 16 of FIGURE 1 is provided. Specifically, the pump 20 is placed in the pump well 14 and takes the molten aluminum of the hearth 12 forcing it into the loading well 16. With reference to FIGURE 3, it can be seen that the rotation of the impeller 22 draws molten aluminum from the bath 24 towards the pump 16 and drives it through the outlet 26, through the passage 28 and through the inlet 30 into the loading well 16. Molten aluminum flows up the ramp 32 into the loading well 16, passing over an inner edge 34 towards the cavity 36 and exits through the exit 38. it prefers that the front edge 44 of the ramp 32 be positioned adjacent the inlet 30 of the loading well 16. While it is beneficial that the ramp 32 be inclined, this does not require that it be achieved by a constant inclination. Instead, as shown in the embodiment of FIGURES 2 and 3, the ramp 32 is inclined in a first portion at 180 ° 40, but is horizontal on the final portion of 120 ° 42. Accordingly, the invention is intended to understand all the versions of an inclined ramp. Similarly, the invention is intended to comprise a ramp comprising 45 ° of the circumference of the loading well 16 to 360 °. However, it is preferred that the ramp extends between 180 ° and 270 °. Because the present invention is applicable as a component to remodel existing cargo wells, it can be seen from FIGURE 2 that the design includes a base section 46 of refractory material which raises the cavity 36 to provide space for an outlet 38 that allows molten metal to flow into the slag pit 18 in FIGURE 1. is recognized by those of ordinary skill in the art, the metal pieces being recycled are deposited on the surface of the melt 48 in the loading well 16. Referring now to an alternative embodiment of the invention, reference is made to the FIGURES 4 and 5. In this embodiment, a scrap casting device 100 is comprised of a block of refractory material 102 which is constructed of a suitable size to provide a coupling with relatively tight tolerance with the dimensions of the existing loading well. (example: loading well 16 of FIGURE 1). Preferably, the block 102 is constructed of cured material such as an alumina-silica refractory or other moldable material known to those skilled in the art. In a preferred form of the invention, the surfaces of the molded body will be treated with boron nitrite before the heat treatment. Again with reference to FIGURES 4 and 5, the block 102 includes a chamber 116 which generally has a cylindrical side wall 118, a base 120 including a ramp 121, with an internal wall 122 forming a centrally located cavity 123 leading to the outlet 124 and the outlet conduit 125. The ramp 121 again starts with a leading edge 124 adjacent to the entrance 126 of the chamber 116. In this instance, the entrance 126 includes a thinned opening 128. Without the desire to be restricted by theory, it is believed that the present invention provides superior results by creating an upward flow adjacent to the outer walls of the chamber and a downward flow of vortex in the central portion of the chamber resulting in a bending action in the chamber. the interface of the flows down and up. It has been determined that this design improves the amount of scrap melted per hour and the variety of scrap particles which can be submerged within the molten metal bath. Scrap of molten metal, particularly aluminum, can be difficult to submerge based on the variety of characteristics such as the size of the scrap particles and the presence of oil or other organic material on its surface. More specifically, the size of the pieces and the organic content can greatly influence the flotation of the material and adversely affect the ability of the scrap immersion system to submerge the scrap. In this respect, scrap that does not submerge and float on the surface typically will not melt, and can actually burn. Therefore, rapid immersion of scrap particles is an essential feature of any system. As indicated above, it is believed that the present invention obtains superior results due to the flow mode. In addition, the waves collapse, and in this case, in a centripetal rather than linear configuration, this wave mode action is beneficial because it covers the unmelted scrap resulting in increased scrap loading ratios. However, it is not the intention to limit this invention to this flow pattern because the device has been found to be very effective even when this mode action is not demonstrated. In addition, a further feature of the present invention is the creation of a vortex that has a large surface area. Theoretically, the more surface is provided by the vortex, the greater the exposed area available on which the pieces of scrap metal can be dropped. In addition, the vortex in the present system is wide but not very deep. If the vortex is too deep, there is a possibility that air will be trapped causing excessive oxidation of the metal. The following examples are provided to facilitate the explanation of the invention but are not intended to limit the invention to the specific embodiments disclosed herein. EXAMPLES Model with Water The tests with water models of the present system were carried out to evaluate the immersion operation and the optional ramp angles. Specifically, an immersion well of the type presented in FIGURES 3 and 3 was created. The operation was evaluated based on the force of the downward flow acting on the surface of the vortex. The reason for the pump flow, liquid depth and other operating conditions were consistent with the standards of the molten metal industry. Generally, the optimum performance was with a ramp angle between 5 and 10 degrees, however, immersion was achieved through varying degrees of angles.

Evaluations with Cast Metal A loading well of the type indicated in FIGURES 4 and 5 was constructed with Premier Aluguard 60 and was evaluated in a molten metal furnace of the type indicated in FIGURE 1. Again, operation was determined using conditions consistent with standards of the molten metal industry. The operation was evaluated based on the effective immersion and the casting of thin thickness scrap, based on the maintenance requirements of the system and the speed at which the scrap is immersed in order to avoid oxidation. It was noted that the scrap immersion ranges were very high and exceeded the melting capacity of the furnace. In several tests, immersion ratios of up to 10,000 pounds per hour (453.6 g / hour) of low density scrap were obtained using a Metaullics L355D pump operating at 600 rpm. The immersion speed was excellent, with no evidence of oxidation of the scrap in the loading well. The melt loss by oxidation was measured and determined as substantially below what is generally acceptable in the industry. Particularly, while the rate of recovery or loss of melt are equal or more important than the production ratios, they are more difficult to quantify and confuse in the production environment. Additionally, its definition, both in mathematical approaches and in general approaches, generally varies from plant to plant. Further complicating such analysis, these results are not generally shared since their financial impact on a plant is a vital component. Therefore, comparing these values for different operations can be difficult. Factors such as scrap thickness, magnesium content and melting temperature can greatly influence the result. Finally, the type of scrap immersion system also has a significant impact on recovery. In addition, minimizing time off for maintenance is a long-term benefit which can not be quantified in a short-term test. Taking into account the variations of any immersion analysis, the present invention was evaluated in a load test with two tons where the recovery ratio was quantified using a melt loss calculation. The load was added 160 pounds (73 Kg) of flux salt. After properly conditioning the melt to standard melt practices, 273 pounds (123.8 kg) of slag was removed.

The additional material obtained in the slag was equal to 77 (34.9 Kg) pounds or a melt loss of approximately 2%. It is estimated that this result may be an improvement over the popular immersion system comprised of mechanical elements used to push scrap under the surface of the melt into the loading well, assuming that an identical scrap material is used. If said melt loss can be maintained throughout the life of the system, and if said melt loss provides a 1% improvement over previous apparatuses, the system of the invention in a plant that produces 15 million pounds (6.8 million of kilos) per month gets an increase to the monthly income of $ 100,000 (dollars) at the current price of $ 0.67 (dollars) per pound of aluminum. Additionally, the plant will obtain a lower cost for slag recovery since less slag is generated. Demonstrating further advantages of the present invention, the loading well remained free of maintenance for a long period of the production cycle and did not present residual material in the loading well during periods of production interruption. Therefore, it is apparent that, according to the invention, a scrap immersion device has been provided that fully satisfies the objectives, goals and advantages indicated above. While the invention has been described in conjunction with specific embodiments thereof, it is evident that various alternatives, modifications and variations will be apparent to those skilled in the art in light of the foregoing description. Accordingly, it is the intention to cover all such alternatives, modifications and variations that are within the spirit and broad scope of the appended claims.

Claims (15)

1. CLAIMS A scrap immersion device comprising an open chamber including side and base walls of heat resistant material, an inlet in a side wall of the chamber, an outlet in the base of said chamber and a ramp adjacent to said wall side of the camera. The immersion device of claim 1 wherein said inlet is approximately at the same horizontal level within said chamber as said outlet. The immersion device of claim 1 wherein said ramp includes a front edge near the inlet. The immersion device of claim 1 wherein said chamber is formed on a block of said refractory material, an outlet conduit is provided in said block in fluid communication with said outlet of the chamber. The immersion device of claim 1 wherein said ramp traverses at least 180 ° of said wall of the chamber. The immersion device of claim 5 wherein said ramp passes through at least 270 ° of said wall of the chamber. The ramp according to claim 1, which includes a substantial portion having a slope of at least 5o. The immersion device of claim 1 wherein a wall extends from an interior face of said ramp to define an entrance to said outlet. 9. The immersion device of claim 8 wherein said wall extends 360 ° to form a passage. The immersion device of claim 9 wherein said passage is cylindrical in shape. The immersion device of claim 9 wherein said passage is thinned to a diameter approximately equivalent to said outlet of the chamber. 12. The scrap immersion device of claim 1 is composed of refractory material. 13. The scrap immersion device of claim 1 includes a pump for providing a flow of molten metal to the inlet. 14. The scrap immersion device of claim 1 forms a component of a loading well of an aluminum recycling furnace. The scrap immersion device of claim 7 wherein the ramp includes a portion having a slope of at least about 10 °. . A scrap immersion device comprising a body of heat-resistant material including a base and a side wall defining an open cylindrical chamber, an entrance to said chamber in the side wall, an outlet in the bottom of said chamber leading to an outlet conduit in said base providing a flow outlet of said device, a ramp adjacent said side wall of the chamber, said ramp includes a first edge proximate said bottom of the chamber and adjacent said entrance and generally in spiral in around a cylindrical opening formed by an inner wall of said ramp. . A method for melting metal scrap comprising depositing metal parts in a molten metal bath in an open chamber including walls of heat resistant material, an inlet placed in a side wall of the chamber, an outlet placed in the base of said chamber and a ramp adjacent said side wall of the chamber, pumping molten metal within said inlet to create a vortex in said bath which absorbs said metal parts in said bath. . A metal scrap immersion device composed of a body of heat-resistant material including a base and a side wall defining an open cylindrical chamber, an entrance to said chamber in a side wall adjacent said base, and an outlet thereto. camera approximately in the center of said base.