Molten metal conveying means and method of conveying molten metal from one place to another in a metal-melting furnace using intermittent or pulsating insert gas feed

Description

BACKGROUND OF THE INVENTION
1. Field of the Invention
Movement of molten metal in a mass or pool of molten metal in a metal-melting furnace, establishing and maintaining efficient circulation of molten metal therein, movement of said molten metal from a hotter area to a colder area and thereby enhancing the efficient melting of metal chips in the molten metal mass or pool. Pump means for effecting the same.
According to the present invention, the efficiency of the molten metal pump and its operation are improved by employing intermittent or pulsed introduction or feed of the inert gas into the molten metal mass.
2. Prior Art
For the efficient melting of metal chips, especially scrap metal chips, particularly brass, aluminum, magnesium, titanium, and alloys thereof, by introduction of the same into a pool or mass of molten metal, usually the metal of which they are formed or an alloy thereof, as in the feed or charge well of a metal-melting furnace, e.g., a reverberatory furnace or the like, it is not only desirable but necessary to circulate molten metal from the hottest area of the metal-melting furnace, that is, the main chamber thereof, out into side chambers or wells, and especially into the feed or charge well, on a continuous basis. According to present practice of the art, a molten metal circulating pump, fabricated at least partially of graphite, is the means of choice. Such a pump comprises a submerged discharge scroll which houses an impeller mounted on a vertical shaft which rides in silicon carbide bearings. The shaft, upon which the pump impeller is mounted, is driven by an air or electric motor located atop the pump several feet above the molten metal bath or pool. An alternate use for the same type of pump is to elevate molten metal above the level of the molten metal bath or pool for transfer into other containers, such as a refractory-lined ladle or into a trough which is covered and sometimes heated, referred to in the trade as a "launder". Such a device is also employed to transfer molten metal from one furnace to another. Inasmuch as graphite is refractory, i.e., heat-stable and resistant to attack by most metal alloys as well as characterized by good non-wetting characteristics, such graphite metal circulating pumps have broad acceptance in the metal melting and reclaiming industry. However, due to the fragile nature of the graphite parts, the close tolerance of the pump parts, and the frequent requirement of pulling the pump for cleaning, the wear and breakage expenses account for very high maintenance costs, which on an annual basis often exceed twice the initial cost of the pump. Accordingly, the search for improvements in the molten metal circulating pump design and in general for some means of transporting or conveying molten metal from one place to another, especially in a molten metal bath or pool in a metal-melting furnace, has had high priority. Despite the efforts to date, no effective and economic means or method for moving or conveying molten metal from one place to another, especially in a molten metal bath or pool in a metal-melting furnace, have been devised, despite a long-standing need for the same in the industry.
The present invention represents a considerably advantageous improvement over my previous contribution to this art, as represented by U.S. Pat. No. 5,203,910, issued Apr. 20, 1993.
OBJECTS OF THE INVENTION
It is an object of the present invention to provide a novel method for the movement or conveyance of molten metal from one point to another, especially from one point in a molten metal pool or bath in a metal-melting furnace to another point in said molten-metal pool, or to a point outside of said molten metal pool, usually to a point adjacent said metal-melting furnace. A further object is the provision of apparatus for use in the process, and particularly such apparatus as will permit the attainment of the objectives set forth in the foregoing with relation to the method of the invention. A salient object of the present invention is to provide an improved method and apparatus whereby the conveyance of the molten metal is conveniently, efficiently, and economically effected by the employment of an intermittent or pulsating inert gas feed, rather than the continuous inert gas feed which was employed according to my previous practice. Other objects of the invention will become apparent hereinafter, and still other objects will be apparent to one skilled in the art to which this invention pertains.
SUMMARY OF THE INVENTION
What I believe to be my invention, then, inter alia, comprises the following, singly or in combination:
An improved method for the conveyance of molten metal from one place to another in a molten metal pool or mass in a metal-melting furnace or out of said molten metal pool, comprising the steps of:
providing an elongated conveying conduit having a lower end and an upper end, at least a portion of said conduit being inclined upwardly from the horizontal,
providing a gas feed means having a gas inlet port and a gas exit port,
positioning the exit port of said gas feed means with respect to the lower end of said conveying conduit so as to enable release of gas from said exit port into said conveying conduit at or adjacent its lower end,
submerging the exit port of said gas feed means and the lower end of said conveying conduit in a molten metal mass or pool,
intermittently introducing inert gas into said gas feed means through the gas inlet port thereof and causing said gas to emerge from the exit port thereof into said conveying conduit at or adjacent its lower end and to rise up the incline therein, and
inducing concomitant flow of molten metal in said conveying conduit by means of said gas exiting from the exit port of said gas feed means and into said conveying conduit at or adjacent its lower end and rising up the incline therein; such a
method wherein the method is carried out in a metal-melting furnace; such a
method wherein the molten metal is caused to be conveyed from a lower portion of said molten metal pool to a higher portion of said molten metal pool; such a
method wherein the molten metal is caused to be conveyed from a hotter portion of said molten metal pool to a colder portion of said molten metal pool; such a
method wherein the molten metal is caused to be conveyed from one well or chamber of a metal-melting furnace to another well or chamber thereof; such a
method wherein the molten metal is caused to be conveyed into a charge well of the furnace; such a
method wherein the molten metal is caused to be conveyed from a hotter portion of said molten metal pool into a colder portion of said molten metal pool in a charge well of said furnace; such a
method wherein the molten metal is caused to be conveyed from a hotter area in the main chamber of a metal-melting furnace to another chamber of said furnace; such a
method wherein the conveying conduit is located in a passageway in a wall of the metal-melting furnace; such a
method wherein the conveying conduit is provided as a part of a wall of the metal-melting furnace; such a
method wherein a plurality of conveying conduits are employed; such a
method wherein said plurality of conveying conduits are provided as a part of a wall of a metal-melting furnace; such a
method wherein the metal-melting furnace has chambers of different depths, the conveying conduit is positioned between chambers of different depths, and the molten metal is caused to be conveyed from the deeper of the two chambers into the chamber having the lesser depth; such a
method wherein the molten metal pool comprises magnesium or aluminum or an alloy thereof; such a
method wherein the inert gas comprises nitrogen or argon; such a
method wherein the submerged portion of said gas feed means and said conveying conduit are of high-temperature molten metal resistant refractory material; such a
method including the step of arranging the exit port of said gas feed means so as to be in communication with the interior of the conveying conduit at or adjacent the lower end thereof; such a
method wherein the temperature of the inert gas is between about -50.degree. and about -100.degree. F.; such a
method wherein the temperature of the inert gas is at about -80.degree. F.; such a
method wherein the pressure at which the inert gas is released at the exit port of the inert gas feed means is up to about 150 psi; preferably between about 20 and 150 psi; such a
method wherein the pressure at which the inert gas is released at the exit port of the inert gas feed means is between about 20 and about 60 psi; such a
method wherein the temperature of the molten metal bath is between about 1200.degree. and about 1500.degree. F.; such a
method wherein the temperature of the inert gas is between about -50.degree. and about -100.degree. F. and the pressure under which the inert gas is released from the exit port of the inert gas feed means is between about 20 and about 60 psi; such a
method wherein the temperature of the molten metal pool is between about 1250.degree. and about 1450.degree. F.; such a
method wherein the conveying conduit has an inclined reach from its lower end to its upper end; such a
method wherein the conveying conduit has an inclined reach and a substantially horizontal reach; such a
method wherein the conveying conduit has an inclined reach and a substantially horizontal reach at the upper end thereof; such a
method wherein the conveying conduit has an inclined reach and a substantially horizontal reach at both the upper end thereof and the lower end thereof; such a
method wherein the conveying conduit is in the form of a flattened Z; such a
method wherein the conveying conduit has an inclined reach and a substantially horizontal reach at an end of said inclined reach, and wherein the inclined reach and the substantially horizontal reach lie in different vertical planes; and such a
method wherein the conveying conduit has an inclined reach and a substantially horizontal reach at a lower end thereof, and wherein inert gas is introduced into said conveying conduit at or near the bottom or commencement of its inclined reach.
Moreover, improved molten metal conveying means suitable for conveying molten metal from one place to another in a molten metal pool or mass in a metal-melting furnace or out of said molten metal pool, comprising in combination:
intermittent inert gas feed means adapted for feeding inert gas intermittently and comprising a gas inlet port and a gas exit port, at least a portion thereof adapted to be submerged in a molten-metal bath comprising high-temperature and molten-metal resistant material,
an elongated conveying conduit of high-temperature molten-metal resistant material having a lower end and an upper end, at least a portion of said conduit being inclined upwardly from the horizontal,
the exit port of said inert gas feed means being associated with said conveying conduit at or near the lower end thereof so as to enable release of inert gas from said exit port of said gas feed means into said conveying conduit at or adjacent a lower end thereof, thereby to induce concomitant flow of molten metal in said conveying conduit; such a
means adapted to be mounted in a molten metal pool in the interior of a metal-melting furnace; such a
means supported in place in a molten metal mass or pool in a metal-melting furnace; such a
means wherein the molten metal mass or pool is in a metal-melting furnace having one chamber deeper than another chamber, and wherein the lower end of said conveying conduit is in the deeper chamber and the upper end of said conveying conduit is in said shallower chamber; such
means mounted in a passageway in a wall between chambers or wells of a metal-melting furnace; such a
means built into a wall between chambers or wells of a metal-melting furnace; such a
means comprising a single conveying conduit; such a
means comprising a plurality of conveying conduits; such a
means comprising a plurality of conveying conduits and wherein said gas feed means communicates with said plurality of conveying conduits at or near the lower end thereof; such a
means wherein the conveying conduit is supported in said wall by means of a sleeve around the exterior thereof; such a
means wherein the exit port of said gas feed means is in communication with the interior of the conveying conduit at or adjacent the lower end thereof; such a
means wherein the conveying conduit has an inclined reach from its lower end to its upper end; such a
means wherein the conveying conduit has an inclined reach and a substantially horizontal reach; such a
means wherein the conveying conduit has an inclined reach and a substantially horizontal reach at the upper end thereof; such a
means wherein the conveying conduit has an inclined reach and a substantially horizontal reach at both the upper end thereof and the lower end thereof; such a
means wherein the conveying conduit is in the form of a flattened Z; such a
means wherein a portion of the gas feed means is comprised as a part of a hanger adapted to support the conveying conduit in a molten metal pool; such a
means wherein the gas feed means comprises a block which supports said conveying conduit, said block having therein a passageway comprising the exit port of said gas feed means; such a
means wherein said passageway is a circular passageway surrounding said conveying conduit and wherein said exit port is located in said circular passageway; such a
means wherein the conveying conduit has an inclined reach and a substantially horizontal reach at an end of said inclined reach, and wherein the inclined reach and the substantially horizontal reach lie in different vertical planes; such a
means wherein the conveying conduit has an inclined reach and a substantially horizontal reach at a lower end thereof, and wherein inert gas is introduced into said conveying conduit at or near the bottom or commencement of its inclined reach; such a
means wherein the conveying conduit is at least partially in the form of a passageway in a block of refractory material; such a
means comprising a plurality of conveying conduits at least partially in the form of passageways in a block of refractory material, and such a
means wherein the gas inlet means also at least partially comprises a passageway in said block of refractory material.
Additionally, such a method wherein inert gas is retained at the surface of the molten metal mass to impede or prevent oxidation thereof and means for so doing, and such a
means wherein the inert gas feed means is adapted to provide a pressure of inert gas at the exit port of the inert gas feed means of up to about 150 psi, preferably between about 20 and about 60 psi.
Further such a method wherein the intermittent introduction of inert gas is controlled so as to provide substantially spherical inert gas bubbles in said conveying conduit, or alternatively so as to provide substantially cylindrical inert gas bubbles in said conveying conduit, and such a
method wherein the intermittent introduction of inert gas involves an "on" time between about 0.02 and 0.08 second and an "off" time between about 0.01 and 0.05 second, preferably wherein the intermittent introduction of inert gas involves an "on" time of about 0.05 second and an "off" time of about 0.03 second.
Finally, such a means wherein the means for intermittent inert gas feed is adapted to provide substantially spherical inert gas bubbles in said conveying conduit, or alternatively to provide substantially cylindrical inert gas bubbles in said conveying conduit, and such a
means wherein the means for intermittent inert gas feed is adapted to provide an "on" time between about 0.02 and 0.08 second and an "off" time between about 0.01 and 0.05 second, preferably wherein the means for intermittent inert gas feed is adapted to provide an "on" time of about 0.05 second and an "off" time of about 0.03 second.
DEFINITIONS
For purposes of the present invention and application, the following terms have the following meanings:
Convey--To cause to pass from one place to another, in the context of the present application from one place to another within a molten metal bath, usually contained in a metal-melting furnace, and frequently from one chamber thereof to another, or from the molten metal pool in the metal-melting furnace out of said molten metal pool, e.g., to an adjacent container, ladle, launder, or another metal-melting furnace.
Conduit--This term has its usual meaning of a pipe, tube, tile, or the like, and is frequently used herein as the second word in the term "conveying conduit", which is the essence of the present invention.
Concomitant--Accompanying, but not in a subordinate way.
Refractory material--Such material as is immune to reaction, especially to high temperatures and, in the present case, also to the molten metal involved and to which the material may be exposed.
Other terms will find their definitions at or near the point where employed in the Specification, and still other terms will require no explanation whatever as they will have their usual meanings and in any event will be readily understood by one skilled in the art.
GENERAL DESCRIPTION OF THE INVENTION
The present invention relates to apparatus for the movement, transport, or conveyance of molten metal from one place to another by means which involves no moving parts. This apparatus is capable of moving molten metal upwardly as well as horizontally, and utilizes a relatively low quantity of inert gas as the propellant, representatively argon and nitrogen, both of which are currently employed in the production of metal alloys and their refinement. Both of these inert gases may be satisfactorily employed according to the present invention. To assure a high purity of the inert gas, the gas may conveniently be maintained under high pressure at temperatures which may be as low as -100.degree. F., usually between about -50.degree. and -80.degree. F., which purity assures the absence of water vapor, which of course could result in explosive reactions if introduced into a molten metal bath or pool.
The present invention comprises an elongated conveying conduit which is inclined along at least a portion thereof, constructed of graphite or other suitable refractory material, inert gas feed means suitable for delivering the inert gas to the conveying conduit at or near the lower end thereof and usually from above the molten metal bath, and may advantageously include a control system for monitoring the delivery of the inert gas and the rate at which delivered through an exit port which is adjacent to and generally in communication with the interior of the conveying conduit at or near the lower end thereof. Inert gas under pressure up to about 150 psi or so, and generally between about 20 and about 60 psi, at the exit port, often conveniently about 30 psi at the exit port, is thus delivered to a location referred to as the exit port near the bottom of the gas delivery means, and at or near the lower end of the conveying conduit, where the inert gas is released from the exit port into the said conveying conduit. According to the present invention, the inert gas then forms a bubble equal to the inside diameter of the conveying conduit as it enters at or near the lower end thereof, and the pressure exerted on the bubble of inert gas, especially when the apparatus is located at or near the bottom of molten metal bath or pool in a metal-melting furnace, creates sufficient force to cause the gas bubble to seek lower pressure which commences to exist as the gas bubble rises up the inclined portion of the conveying conduit. As the inert gas rises, it not only pushes a column of molten metal in front of it, but it also creates a negative pressure or vacuum behind the bubble, causing the inlet of the conveying conduit at the lower end thereof and toward the bottom of the molten metal mass or pool in the metal-melting furnace to fill and refill with additional molten metal. As additional inert gas is provided by means of the gas feed means and released from the exit port thereof into the conveying conduit at or near the lower end thereof, a portion of the molten metal is lifted, causing a molten metal flow to occur from one location to another. A secondary boost in performance of this conveying means is achieved when the very cold inert gas (temperature usually between ca. -50.degree. and -100.degree. F.) is released into the molten metal, which is usually at a temperature between about 1200.degree. and 1500.degree. F., generally between about 1250.degree. and about 1450.degree. F., from the exit port of the gas feed means into the conveying conduit at or near the lower end thereof, which produces a thermodynamic force due to the rapid expansion of the gas as the cold inert gas mixes with the high temperature molten metal. By operating in this manner and employing the apparatus of the present invention, the method of the present invention is efficiently and economically achieved without the necessity of any moving parts, and the molten metal is conveniently transported or conveyed from one location to another either in the molten metal bath or pool or from a position in the molten metal pool out of the same.
As pointed out in the foregoing, the introduction of the cold inert gas into the hot molten metal results in a strong thermodynamic force, which also exerts its effect upon the efficiency of the method and apparatus of the invention, which results from the rapid expansion of the inert gas as it mixes with the high-temperature molten metal into which it is introduced.
The apparatus and method of the present invention have obvious and important application wherever molten metals require conveyance or transport or movement, and will find especially important applications wherever electricity is limited or unavailable, and particularly where high temperatures, corrosion, and abrasive materials such as molten metals are involved, and in any such cases where conveyance of the involved fluid in a vertical direction, that is, a direction inclined vertically from the horizontal, is or can be conveniently involved or employed.
According to the present invention, the pressure at which the inert gas is supplied to the molten metal mass is between about 20 and 150 psi, with between about 20 and 60 psi being most desirable. The higher the level of the molten metal mass in the furnace chamber above the inert gas exit port or entry nozzle E, the greater the gas pressure to be employed, as will be apparent to one skilled in the art, the pressure employed being of necessity sufficient to overcome the static head provided by the molten metal mass.
The intermittent or pulsed introduction of the inert gas according to the present invention involves a dwell time of, e.g., about 0.01 to 0.05 and preferably about 0.03 second between introduction cycles, and an introduction time of between about 0.02 and 0.08 and preferably about 0.05 second, which creates optimum efficiency when these ranges of 0.02 to 0.08 and preferably about 0.05 "on" or "flow" time and 0.01 to 0.05 and preferably about 0.03 second of "off" or "no flow" time are employed. In the higher range of "on" time, cylindrical bubbles, as will be described further hereinafter, are produced whereas, in the lower ranges of "on" time, more spherical bubbles are produced, as will again be more fully disclosed hereinafter. Such procedure produces an intermittent inert gas feed or pulsation effect, and may be conveniently effected, maintained, and controlled by using a simple on/off timer arrangement with time delay or dwell cycle being electrically, electronically, or otherwise controlled, as by a gas solenoid valve or other valve according to the system shown schematically in the drawings, especially in schematic FIG. 22.
Thus, when operating according to the present invention, employing the intermittent or pulsed inert gas introduction, an increase in total flow of molten metal, e.g., aluminum, can be conveniently effected while reducing by at least 50% the required volume of inert gas per pound of molten metal, e.g., aluminum, pumped.
It has been observed that the shape of the bubbles produced is controlled by the length of time employed for the introduction of the inert gas, as delivered through an exit port or ports (or a nozzle or nozzles) E located at or near the bottom of the molten metal pump or the conveying conduit CC thereof. Thus, by forming a bubble the shape of which is nearly spherical or alternatively nearly cylindrical, while avoiding the loss of inert gas out the bottom of the pump adjacent the inert gas exit port or nozzle E, and without increasing the physical diameter and area of the bubble more than is required for creation of a bubble the diameter of which is sufficient to essentially occupy the inside diameter of the conveying conduit CC of the pump, the bubble essentially in the form of a sphere or a cylinder inside the conveying conduit of the pump acts as a gaseous piston, pushing the molten metal ahead of it.
For purposes of explanation, when the bubble is essentially spherical, the operation is essentially as previously described. When the bubble created has a diameter which occupies or corresponds essentially to the inside diameter of the pipe of the pump, but the length of which may be greater, e.g., several times that diameter, this simply reduces the available area within the conveying conduit of the pump between inert gas bubbles and which available area is occupied by the molten metal being pumped. Intermittent or pulsed gas feed which creates a bubble, which is essentially spherical in shape, at a frequency which maintains the presence of two to four bubbles in the conveying conduit of the molten metal pump from beginning to end, appears to approach optimum efficiency, according to present findings. As already stated, the operation is entirely satisfactory, and even more rapid although perhaps somewhat less efficient since more gas may be required, when the bubbles created are more cylindrical in shape, which results from a longer period of inert gas feed "on" time than when essentially spherical bubbles are to be produced. The total molten metal depth in the well of a given furnace establishes the most desirable physical length and vertical rise of a molten metal pump employed according to the present invention, as usual, and the total vertical rise and corresponding head pressure of the inert gas employed establishes the rate of formation of inert gas bubbles and their size and precise shape, but also the rate at which a given bubble will rise per second, assuming a constant inert gas temperature at the inert gas exit port or nozzle and a constant molten metal, e.g., molten aluminum, temperature. The production of essentially spherical or essentially cylindrical bubbles presents no problem when operating within the dwell times between cycles and the on/off inert gas feed times as set forth in the foregoing.
Numerous modifications in both the method and apparatus of the invention, as well as specific embodiments and advantages thereof in a particular case, will be readily apparent to one skilled in the art, especially from the more detailed description of the invention which follows.

DESCRIPTION OF THE DRAWINGS
Reference is now made to the drawings, wherein:
FIG. 1 is a top plan view showing apparatus according to the invention and illustrating the method of the invention in association with a metal-melting furnace, in this case a reverberatory furnace having a main chamber, a circulation well, and a charge well, all in communication, the reverberatory furnace and its associated chambers and wells being shown partially schematically and partially in section, the conveying means of the invention being shown communicating between what is normally the circulation well and the charge well of the reverberatory furnace.
FIG. 2 is a front elevational view taken along line 2--2 of FIG. 1, showing apparatus according to the invention and employed in the method of the invention in location in a mass of molten metal and communicating between the usual circulation well and the charge well of the reverberatory furnace.
FIG. 3 is an enlarged detail view of the essential elements of the invention as shown in FIG. 2.
FIG. 4 is an end view of the apparatus of the invention taken along line 4--4 of FIG. 1.
FIG. 5 is like FIG. 3 and FIG. 6 is like FIG. 4, illustrating another embodiment of the conveying conduit apparatus of the invention.
FIGS. 7 and 8 are like FIGS. 3 and 4, illustrating a further embodiment of the conveying conduit apparatus of the invention.
FIGS. 9 and 10 are like FIGS. 3 and 4, illustrating a still further embodiment of the invention in which a double conveying conduit is provided.
FIG. 11 is like FIG. 1, in abbreviated form, being a plan view of an alternative form of the invention, advantageously employed in carrying out the method of the invention, wherein the conveying conduit is provided in triplicate and is built into a vertical wall separating the main or heating chamber of the furnace from the forward chamber of the furnace, there being no separate circulation well and charge well in the reverberatory furnace depicted.
FIG. 12 is a front elevational view along line 12--12 of FIG. 11, showing the triplicate conveying conduit embodiment of the invention from the front.
FIG. 13 is a side view of the embodiment of FIGS. 11 and 12 taken along line 13 of FIG. 11.
FIG. 14 is like FIG. 13, being a side view of a further embodiment of the invention, wherein the conveying conduit is shown in a metal-melting furnace having a deeper main chamber than its forward chamber, the lower end of the conveying conduit of the invention being located near the bottom of the main chamber and the upper end of the conveying conduit of the invention being positioned in the forward chamber of the furnace which has the shallower depth.
FIG. 15 is an end view, partially in section, like FIG. 4, illustrating another embodiment of the invention in which the conveying conduit is double hung and in which a hanger on one side of the conveying conduit comprises the gas inlet means as its exit port in a hollow circular doughnut surrounding the lower end of the conveying conduit, the said exit port communicating with the interior of the conveying conduit at its lower end.
FIG. 16 is a side view of the apparatus of FIG. 15 along the line 16--16 of FIG. 15.
FIG. 17 is a partial top plan view showing another embodiment of the invention, in fact, two separate embodiments of the invention, especially designed for conveying molten metal from within the molten metal pool of a reverberatory furnace to the outside, and FIG. 18 is a partial front view of the apparatus shown in FIG. 17 along the line 18--18 thereof.
FIG. 19 illustrates the type of bubbles produced in a continuous inert gas feed operation, wherein the inert gas is continuously fed into the system in accord with my previous practice and disclosure.
FIG. 20 is the same as FIG. 19, but the shape of the bubbles is essentially spherical in nature due to the intermittent inert gas feed employed according to the present invention.
FIG. 21 is like FIG. 20, the bubbles of inert gas in this case being of a generally cylindrical nature, this being a result of intermittent inert gas feed using a greater "on" time or a shorter dwell or "off" time between gas introduction cycles, which is somewhat less than employed when spherical bubbles of FIG. 20 are to be produced.
FIG. 22 is a schematic illustration of apparatus of the type required for efficient operation of the system employing intermittent inert gas feed or flow according to the present invention.
As shown in FIG. 19, with continuous feed of the inert gas, the bubbles are randomly dispersed and of relatively small size as compared, for example, with the essentially spherically bubbles shown in FIG. 20 when a maximum dwell time is employed between inert gas introduction cycles. From FIG. 21 is seen a relatively cylindrical type of bubble which is produced when the dwell time between cycles of inert gas introduction is somewhat less than that employed for production of the essentially spherical bubbles illustrated in FIG. 20.

DETAILED DESCRIPTION OF THE INVENTION
The present invention, in both its method and apparatus aspects, will be more readily understood from the following detailed description, particularly when taken in conjunction with the drawings, in which all of the significant parts are numbered and wherein the same numbers and letters are used to identify the same parts throughout.
A metal-melting furnace, as shown a reverberatory furnace, of refractory material or having the usual refractory lining and fired by combustion burners 14 fed by natural gas or fuel oil which throw flames into the interior of main chamber 18 thereof through flame-introduction means 16, is shown in the FIGS. at 10.
The furnace well comprises bottom wall 11 and side walls 12 and 13, with a mass of molten metal, preferably and usually aluminum or magnesium or an aluminum or magnesium alloy, therein being shown at 26. The base portions 11 of the furnace may be supported on the underlying floor by means of I-beam supports, neither of which are shown. Main chamber 18 is provided with main chamber extensions 19 in the form of what is normally circulation well 20 and charge well 22, connected with each other and with main chamber 18 by means of communicating passageways 24. Molten metal 26, e.g., brass, aluminum, magnesium, titanium, other metals, or alloys thereof, is contained in main chamber 18 and is circulated from the hottest part thereof, indicated at 38, through intermediate well 20 and charge well 22 via communicating passageways 24. A usual circulation means including electrically or otherwise driven motor and its associated circulating means, including associated heat-resistant, e.g., carbide or graphite, impeller, rotor, fan, or blade, may or may not be located in circulation well 20 and, in any event, is not shown because it is conventional in the art and forms no part of the present invention. According to the present invention, the necessary circulation is provided by means of the apparatus of the present invention, namely, the molten metal conveying conduit CC and associated elements, as will be further explained hereinafter, and the presence of a separate circulating means in what is normally the circulation well 20, as for example shown in U.S. Pat. No. 4,702,768 to Pre-Melt Systems, Inc., is rendered dispensable according to the method and apparatus of the present invention, and its presence or absence is therefore strictly optional depending upon the option of the operator in a particular case or depending upon the pre-existence of such equipment. Conveying conduit CC in this case has an inclined central portion and essentially horizontal portions at both ends thereof, being in the shape of a "Z" which has been stretched or flattened.
According to the flow pattern 36 as created by the conveying conduit CC, which provides the circulating means according to the present invention, molten metal 26 in furnace main chamber 18 is constantly and continuously moved from hottest point 38 in main chamber 18, through communicating passageways 24 and especially by means of conveying conduit CC into intermediate well 20, and thence into charge well 22 to approximately the coldest point 40, shown in charge well 22 at the point or a point adjacent to the normal point of introduction of a charge of new or used unmelted chips into charge well 22, as by chip-charging means of any suitable type, as illustrated for example in prior U.S. Pat. No. 4,702,768 or U.S. Pat. No. 4,872,907, the chip-delivery or chip-charging conduit means being shown in shadow lines at 100. The coldest portion of said molten metal pool in charge well 22, indicated by the number 40, is well known to be at or near the point at which fresh or used unmelted metal chips to be melted are introduced into the metal pool 26 in charge well 22, and the necessity of bringing hotter molten metal to this point by maintaining adequate circulation throughout the metal-melting furnace and in all chambers thereof is therefore well understood by one skilled in the art.
Also visible in FIG. 1 are the molten metal oxide 25, which ordinarily collects at the surface of the molten metal pool 26, this being shown in all of the wells of the metal-melting furnace 10.
The molten metal conveying conduit of the invention, whereby the molten metal is conveyed from one place to another in the molten metal bath, is shown as CC, having a lower end LE and an upper end UE, and being supported by hanger H on crossbar support S. The conveying conduit CC may have hanger H attached thereto by suitable high-temperature resistant adhesive, or by welding or the like, or by doughnut-shaped or other clamp, e.g., ring or block means, and in any case by means comprising material which is resistant to the molten metal and the high temperatures employed.
Conveying conduit CC may be supported by a single hanger H or by a plurality of hangers H, for example, one hanger or set of hangers near the bottom and one near the top thereof or, as shown, one on each side of the conveying conduit CC, as most convenient in a particular case. As will be apparent to one skilled in the art, the gas feed means P can be supplied as an internal portion of a hanger H, should that be desired and, when a plurality of hangers are employed at different points on CC, the lowermost-extending of which comprises the inner gas feed means P, it goes without saying that the other and especially the highermost hanger means will not include gas feed means P, since introduction of the inert gas into or adjacent the lower end LE of conveying conduit CC is of the essence of the present invention. Additionally, since the means whereby the hanger or hangers H are secured to the conveying conduit CC is immaterial, so long as it is operative, additional means may employ surrounding rings or blocks, in turn attached to a hanger or hangers H and supported from above by support S or, still alternatively, the means for securing conveying conduit CC to hanger or hangers H may be by suitable molten-metal and heat-resistant clamps which do not totally surround conveying conduit CC but which merely grip it securely at one or both ends. Alternatively, the hanger or hangers H may be supported from a cover positioned above the well or chamber involved, when such cover is included as a part of the metal-melting furnace employed. Due to the fact that the vertical reach of the gas feed means P is also subjected to the molten metal in the pool or bath and to the high temperatures employed, it is likewise advantageously constructed or clad with refractory material, at least to the extent of the portion adapted to be inserted into or submerged in the molten metal pool. For example, pipe P may be of metal clad with ceramic or, even more advantageously, of graphite clad with ceramic.
As shown, gas feed means in the form of a pipe P is shown adjacent to conveying conduit CC, having an inlet port I and an exit port E, the longest horizontal reach of which pipe P is connected to the vertical reach of P by coupling C and the exit port E of which communicates with an inlet to the interior of CC at a lower portion thereof at or adjacent lower end LE thereof by means of a further coupling C. As will be apparent to one skilled in the art, the apparatus of the present invention is disposed within a passageway 24 in vertical wall 12, and thus extends between what is ordinarily circulation chamber 20 and charge well 22 of the metal-melting furnace 10.
By means of inert gas provided through gas feed means P into conveying conduit CC at or adjacent lower end LE thereof, such inert gas being, for example, argon or nitrogen, the introduction and collection of gas bubbles within conveying conduit CC and the upward movement thereof, over the portion thereof which is inclined upwardly from the horizontal, creates a flow of gas in the upward direction toward upper end UE of conveying conduit CC, thereby creating a negative pressure or vacuum behind the gas bubbles in conveying conduit CC and inducing the flow of molten metal 26 into lower end LE of conveying conduit CC and out the upper end UE thereof, the conveying conduit thereby establishing communication between the chambers 20 and 22 and creating the necessary circulation or flow of molten metal 26 in and about the molten metal furnace from the hottest portion 38 thereof to the coldest portion 40 thereof, especially since it is well established that the lower portions of the molten metal mass 26 attain the hottest temperatures. The inert gases emerging from the upper end UE of conveying conduit CC may either be allowed to escape directly to the atmosphere or retained at the surface of the molten metal mass 26 to impede or prevent oxidation thereof or collected by a hood and vented through adequate environmental clean-up equipment and thence to the outside.
The enlarged views of this embodiment of the apparatus of the invention as shown in FIGS. 3 and 4 are given merely for a better understanding of the apparatus of the invention which will be readily understood by one skilled in the art.
The apparatus of the invention depicted in FIGS. 1-4 with its flattened "Z"-shaped design is of special value when a low arch exists in a furnace wall, as shown the divider wall which separates what has heretofore been regarded as the "circulation" well from the "charge" or "feed" well of a metal-melting furnace, or for moving molten metal from a position within the molten metal pool to point outside thereof, e.g., into another furnace, furnace well, ladle, launder, or the like.
The different embodiment shown in FIGS. 5 and 6 differs only from the embodiment of the previous figures in having no horizontal segments present in the conveying conduit CC of the embodiment there shown, comprising an inclined reach only, i.e., a reach inclined upwardly from the horizontal.
The embodiment of FIGS. 7 and 8 is in all material respects like the embodiment of FIGS. 1-3, but is characterized by a single horizontal reach in the conveying conduit CC of the invention at the upper portion thereof, terminating in the upper end UE thereof, whereas the lower end LE of the conveying conduit CC of this embodiment is located directly at the bottom of the inclined portion and not at the end of an extended horizontal portion or section thereof.
The embodiment of the invention depicted in FIGS. 7 and 8 adds a substantially horizontal upper section to the inclined reach of the conveying conduit depicted in FIGS. 5 and 6.
FIGS. 9 and 10 show a further embodiment of the invention, wherein two side-by-side conveying conduits CC are provided, each with its own upper end UE and lower end LE, and wherein the gas feed means P is located between the two conduits CC and communicated thereinto at or near the lower ends LE thereof by means of a T-fitting or T-passageway T, whereby inert gas is brought simultaneously to or near the bottom or lower ends LE thereof from the exit ports E of pipe P. The assembly, including conveying conduits CC, a passageway for pipe P, and either T-fitting or T-passageway T, is molded in or routed out of block BB, of graphite, ceramic, or the like, and block BB is supported by the usual hanger H which is in turn supported at its upper ends by means of cross-bar or similar support S. Once again, the assembly comprising the two side-by-side conveying conduits CC is shown as located between compartments or wells of the metal-melting furnace in a communicating passageway 24 thereof.
The embodiment of FIGS. 9 and 10 is representative of apparatus comprising a plurality, two or more, parallel inclined conveying conduits, with a single gas feed means which "T's" off at the bottom, providing two separate exit ports E therefrom which communicate with the parallel conveying conduits CC at or near the lower ends thereof.
Referring now to FIGS. 11-13, FIG. 11 is a top plan view of another metal-melting furnace 10, showing only the essentials required to illustrate the apparatus and the method of the present invention.
As seen from FIG. 11, three separate conveying conduits CC are located by preforming or providing tile or like ceramic in the vertical wall 13 between main chamber 18 and forward chamber 20/22 which, in this case, is not further divided into a circulating chamber and a charge well.
These three built-in inclined conveying conduits CC each have their lower end LE located on the side of the wall adjacent main chamber 18 and their upper ends UE located on the side of the wall adjacent forward chamber or well 20/22 and are sleeved into the wall 13 by means of ceramic or other suitable and preferably smooth close-fitting sleeve SL.
Gas feed means in the form of pipe P, having inlet port I and three separate exit ports E, one for each of the three separate conveying conduits CC, is simply supported from above by chain C. In this embodiment, the conveying conduit CC is, as will immediately be apparent, built directly into a wall of the metal-melting furnace 10, and therefore need not be provided as a separate unit, element, or assembly.
As best shown in FIG. 13, the conveying conduits CC are upwardly slanted or inclined from at or near their bottom portion or lower end LE adjacent the forward wall 13 of main chamber 18 and extend upwardly to near the upper surface of the molten metal pool 26 in the forward chamber 20/22.
The embodiment of the invention depicted in FIGS. 11-13 illustrates the apparatus of the invention employing multiple conveying conduits permanently cast into the hot wall, i.e., the wall opposite the combustion burner, of the main chamber of a metal-melting furnace, for the creation of a molten metal flow into the charge well of the metal-melting furnace by introducing gas through the gas feed means, in this case involving a multiple gas manifold as illustrated, through the exit ports thereof into the plurality of conveying conduits with which the exit ports are in communication (actually inserted thereinto) at or near the bottom of the inclined conveying conduits. When necessary, occasional cleaning of the conduits can be readily accomplished, even while the furnace is still hot, by standing above the charge well and manually rodding out the conduits with a simple furnace tool.
FIG. 14 is a view of another embodiment of the invention like the view of FIG. 13, taken from the side, showing a metal-melting furnace 10 wherein the main chamber of the furnace is of a greater depth than the forward chamber 20/22 thereof. Accordingly, mounting of the conveying conduit CC between main chamber 18 and forward chamber 20/22 through communicating passageway 24 in vertical wall 13, or by building in the conveying conduit CC as in FIGS. 11-13, permits the lower end LE of conveying conduit CC to be located at a considerably greater depth than the upper end UE of conveying conduit CC, thereby permitting greater force to be exerted by the rising inert gas bubbles, which accordingly must travel a greater distance within the inclined conveying conduit CC, thereby imparting or inducing a greater and more positive flow of molten metal from its lower end LE, located in the hot spot near the floor of the main chamber 18 adjacent vertical wall 13, and up to near the surface of the molten metal 26 in forward chamber 20/22 at the upper end UE thereof.
Inert gas is as usual provided through gas feed means in the form of pipe or tube P and from inlet port I and released at exit port E near the lower end LE of the inclined conveying conduit CC. As shown, gas feed means P is located outside of conveying conduit CC and communicates thereinto by means of a fitting or coupling C but, in an alternative embodiment, pipe P can be located interior of conveying conduit CC or can extend to a point below lower end LE of conveying conduit CC, in which case it is preferably provided with an angle just before its exit port E so as to bring the exit port E just below the lower end LE of conveying conduit CC.
The embodiment of FIG. 14 illustrates application of the apparatus and method of the invention in a metal-melting furnace having a special deep well as the main well thereof, which is designed specifically to permit increased vertical head pressure to be achieved, thereby simultaneously to attain significantly-better flow of molten metal from the deeper well to the shallower well.
FIGS. 15 and 16 show another embodiment of the invention in which the conveying conduit CC, having an inclined segment or reach and a substantially horizontal reach at the upper end thereof, is double hung by hangers H from a supporting plate S. The apparatus as shown is suspended in the molten metal mass 26 in passageway 24 of wall 13. A coupling C is shown at the top of the vertical reach of the gas inlet means and inlet port I, extending through coupling C communicates with the interior of vertical pipe P constructed in this case of graphite G and clad with ceramic cladding CG. Pipe P is threaded into lower graphite or other refractory block B which comprises a lower extension of the gas inlet means and a passageway constituting a continuation of the interior of pipe P, which passageway terminates in the form of a ring R, being a hollow excavation surrounding conveying conduit CC and comprising the exit port E of the gas feed means, which exit port E, as shown, communicates with an inlet to the interior of conveying conduit CC at the bottom side of the lower end LE thereof. The hanger H at the left-hand side of FIG. 15 is also screwed at its lower end into block B, but does not comprise the additional gas feed means elements just described as being comprised in the right-hand hanger H. Once again, the design of this particular embodiment of the invention is particularly suitable for the movement of a portion of the molten-metal mass or pool from a lower level to a higher level or from within the molten-metal pool to a point outside thereof, as to an adjacent container, ladle, launder, or metal-melting furnace.
Referring now to FIG. 17, this partial top plan view of a reverberatory furnace 10 shows in shadow lines at A a conveying conduit CC having the usual lower end LE and upper end UE, set in place in sidewall 12 of the main chamber 18 of the reverberatory furnace 10, thus leading to the outside. As shown partially broken off in FIG. 18, also in shadow lines, the conveying conduit CC is of the simplest type, having an inclined reach but no horizontal extensions or portions thereof at either its lower or upper ends which, of course, may be optionally provided if in the opinion of the operator or manufacturer any special advantage is to be attained thereby. The gas introduction means employed with this particular conveying conduit CC may conveniently be the same type as shown in detail in FIG. 13, using only a pipe P for introduction of the inert gas into the lower end of the conveying conduit CC in the usual manner as previously described.
Also shown in FIGS. 17 and 18 is an alternative embodiment AA, again especially arranged for the conveyance of molten metal from out of a molten metal pool of a reverberatory furnace 10 to the outside. In this case, the lower end LE of the conveying conduit CC is located in main chamber 18 and extends through passageway 24 into front chamber 20/22, where it takes a right-hand turn at the commencement of its incline, as best seen in FIG. 18, terminating in a substantially horizontal reach at the end of the incline and leading to its upper end UE above the furnace wall 12 and outside thereof. Gas introduction means in the form of pipe P has its exit port E at a lower portion of conveying conduit CC near the lower end LE thereof, but located so as to be at or near the bottom of the inclined reach thereof. Otherwise, the assembly is essentially the same as shown in previous FIGS. and as previously described, the most noteworthy aspects of the embodiment AA as illustrated in FIGS. 17 and 18 being that the conveying conduit CC is arranged in several different planes, a substantially horizontal plane at the bottom thereof commencing with the lower end LE thereof, an inclined plane at an approximately 45.degree. angle to the first plane commencing at the beginning of the incline thereof, and a parallel substantially horizontal plane at the end of said inclined portion leading to the upper end UE thereof. The conveying conduit CC also lies in a plurality of vertical planes, as shown two separate vertical planes, when viewed from above, namely, the plane in which the lower reach of CC lies and the plane approximately right-angled thereto in which the inclined and upper reaches of the conveying conduit CC lie. The two substantially horizontal segments thereof lie in parallel horizontal planes with the inclined portion lying therebetween being at an approximately 45.degree. angle therewith. It goes without saying that the upper substantially horizontal segment of the conveying conduit CC could also be further angled with respect to the inclined portion thereof, for example, it could lie in a vertical plane angled with respect to the plane of the inclined segment thereof.
Another particularly significant feature of the embodiment AA of FIGS. 17 and 18, as well as certain other embodiments shown and described herein, is the location of the exit port E of the inert gas feed means at the end of pipe P in the lower portion of the conveying conduit CC at or near commencement of the inclined reach thereof, rather than more adjacent to the lowermost end LE thereof, so as better to impart movement to the mass of molten metal by release of the inert gas at the commencement of the inclined portion of the conveying conduit CC, as will be readily understood by one skilled in the art.
The salient features of the present invention, and particularly as illustrated by FIGS. 19-22, involving the intermittent or pulsating flow of inert gas into the system, will be fully described at the end of the section entitled "OPERATION" which follows.
OPERATION
In operation, the metal-melting furnace, such as the reverberatory furnace described in more detail in the foregoing, is charged with the molten metal mass or pool in any suitable manner. According to past practice, the predried and usually degreased or delacquered metal chips, whether from recycled or new metal, have simply been thrown into a pre-existing molten metal pool in the charge well of the furnace. Such practice has, however, become passe or obsolete in view of the chip-charging devices or extruding briquetter devices disclosed in Pre-Melt U.S. Pat. Nos. 4,872,907 and 4,702,768. In addition, although metal chips must still be charged into the metal pool in the charge well or charge area of the furnace, it is no longer essential, according to a further Pre-Melt invention, that the chips be degreased or delacquered so long as a non-oxidizing atmosphere is maintained at the surface of the charge well or area and certain exit ports are established for the escape of gas evolved from vaporizable contaminants or impurities present on the chips charged into the molten metal pool which rise to the surface of the pool and usually flame upon entering the ambient air, which provides an oxidizing environment, and may be collected by a hood and associated conduitry and conducted to a point removed from the surface of the molten metal pool for disposal through suitable decontamination equipment before being released into the atmosphere.
In any event, the molten metal pool in the metal-melting furnace is constituted in any suitable or convenient manner, and circulation through the various passageways between the various chambers of the furnace established by employment of the apparatus of the present invention, with or without ancillary circulation equipment of the usual and previously-employed type, as previously described and which, as previously noted, forms no part of the present invention. Due to the proximity of the main chamber to the combustion burners and flame-introduction means usually located in the rear wall of the furnace at the rear of the main chamber, the hottest portion of the molten metal mass is clearly in the main chamber and generally adjacent the front wall of the main chamber. According to the invention, circulation is effected in the molten metal pool by the introduction of an inert gas through appropriate gas feed means having a gas inlet port and a gas exit port, the exit port of which is so located with respect to the lower end of the conveying conduit so as to enable release of gas from said exit port into the conveying conduit. The collection of gas in the conveying conduit and the rise of the accumulated gas bubbles in the conveying conduit induces a concomitant flow of molten metal in the conveying conduit and thereby conveys molten metal mass through the said conveying conduit from a lower level or portion of a well or chamber of the metal-melting furnace to a higher portion or level of the molten metal mass or pool in the same or a different chamber or well of the metal-melting furnace. As shown, a preferred embodiment of the invention involves the employment of the apparatus of the present invention to move a portion of the molten metal mass through the said conveying conduit from one chamber or well of the metal-melting furnace to another, and an especially preferred embodiment of the invention involves the employment of the apparatus of the present invention to move a portion of the molten metal mass from the hottest portion or a hot spot in the molten metal mass or pool to a cooler spot or area, for example, from the main chamber adjacent the forward wall thereof into any adjacent chamber or even out of the molten-metal pool if desired, and another particularly preferred embodiment of the invention involves the employment of the apparatus of the present invention for moving a portion of the molten metal mass from a hotter area or hot spot within the molten metal mass into a cooler portion or area adjacent the normal point of introduction of chips into the molten metal pool, e.g., into the charge well thereof. Moreover, the method of the invention involves the movement or conveyance of a portion of the molten metal mass from a lower portion or area thereof to a higher portion or area thereof, frequently and advantageously through a usual passageway between the various chambers or wells of the metal-melting furnace, or through such apparatus mounted in and/or forming an integral part of a furnace wall, e.g., a wall of the furnace between various chambers or wells thereof, and another particularly preferred embodiment as already stated involves the movement of a portion of the molten metal mass from a hotter portion or area thereof to a colder portion or area thereof, and particularly into the charge well to the point of or adjacent to the point of introduction of chips into the charge well.
By operating in the foregoing manner, whether by the employment of a single conveying conduit or a plural conveying conduit, and whether the conveying conduit or a plurality of conveying conduits are independently mounted in the molten metal mass, for example, in a passageway in a wall between chambers or wells of the metal-melting furnace, or whether a single conveying conduit or a plurality of conveying conduits are mounted directly in the wall or integrally therewith, the necessary circulation of molten metal mass within the metal-melting furnace is readily and conveniently effected and controlled, and portions of the molten metal mass are conveniently moved from a hotter area to a colder area and from a lower level to a higher level and, as already stated and shown in the drawings, from one chamber or well of the metal-melting furnace to another and particularly from a hotter portion of the molten metal mass to a colder portion of the molten metal mass, as in the charge well of the furnace, or even out of the molten-metal furnace if desired.
Thus, from my previous disclosure, the use of a continuous flow of inert gas into a conveying conduit is known to produce or promote a flow of molten metal, e.g., aluminum, through the conduit when present in a well of a metal-melting furnace. Now, according to the present invention, it has been determined that the flow of molten metal can also be achieved, and more economically, when the inert gas flow is not continuous, but rather in the form of short bursts or pulses of the gas. The pulses are controlled by energizing and de-energizing an actuated inlet gas control valve (AV) in the inert gas feed line, preferably located just ahead of inlet port I, as shown in FIG. 22.
Electrical or electronic timers may conveniently be employed to allow the period between bursts or pulses of the inert gas to be set according to predetermined standards, as well as the length of the burst or pulse itself. The adjustability of the intervals for the "on" time and the "off" or dwell time allows the bubble produced, and the shape thereof, to be regulated, thereby to achieve a predetermined performance of the conveying means or "pump".
This pulsated flow offers the advantage of increasing the efficiency of the molten metal conveying means or "pump". The regulated pulse or burst of inert gas, instead of a continuous bubble stream, allows the volumetric flow of gas to be decreased by-as much as fifty percent (50%), while maintaining the same molten metal volumetric flow. The increased efficiency lowers the operating cost associated with the inert gas flow. For example, test results indicate that an optimum time period of 0.05 second inert gas "on" time (A) and a 0.03 second "off" time (B) achieves the same molten metal flow as does a continuous gas feed.
This pulse timing is also useful in producing a desired shape of the bubble in the conveying conduit (CC) or tube of the pump. It has been found that a pulsed spherical bubble (PSB) which completely fills the cross-section of the conveying conduit (CC) or tube provides the best liquid flow result and efficiency. By adjusting the size and rate of the spherical bubble, the maximum ratio of molten metal flow to gas flow can be maintained. Alternatively, a pulsed cylindrical bubble (PCB) of possibly even greater efficiency may be formed and employed by utilizing a slightly greater "on" period and/or a slightly diminished "off" period.
Referring now to the drawings, FIG. 19 shows the inert gas entering the molten metal pump or conveying conduit CC at inlet port I. The gas passes through hanger H from coupling C through the interior of vertical pipe P. The inert gas then enters the conveying conduit CC at the exit port or nozzle E, after passing through the surrounding ring R in support block B. Upon entering the molten metal 26, random sized bubbles, i.e., continuous flow bubbles CFB, are formed and pass through conveying conduit CC and exit the same at upper end thereof UE. As the bubbles travel up the conveying conduit CC, the molten aluminum 26 is also drawn through the tube or conveying conduit CC, thereby creating a pumping action.
The improvement of the present invention is shown in FIG. 20. As illustrated in FIG. 20, the random bubbles CFB from a continuous gas feed are replaced by spherically-shaped bubbles PSB created by short bursts or pulses of the inert gas. The pulsed spherical bubbles PSB shown in FIG. 20 are formed and occupy essentially the entire cross-section of the conveying conduit CC. The resulting piston-type action is more efficient than when employing the random bubbles CFB from a continuous gas feed as illustrated in FIG. 19. The increased efficiency is readily measured by the decrease in operating cost, in particular the reduction in cost of the inert gas employed.
FIG. 21 illustrates another novel bubble configuration according to the present invention. Instead of pulsed round or spherical bubbles PSB, as illustrated in FIG. 20, the bubble shape in FIG. 21 is changed to an elongated cylinder of gas, i.e., a pulsed cylindrical bubble PCB. The PCB bubble occupies essentially the entire diameter of the conveying conduit CC and will draw molten metal into the conveying conduit CC at the lower end LE thereof, adjacent inert gas exit port E, and will then push the molten metal through the conveying conduit CC to exit therefrom at the upper end UE thereof. The individual cylindrical bubble PCB contains more gas than a corresponding spherical bubble PSB, but results in a faster travel speed of the molten metal as well as the inert gas through the conveying conduit CC, and therefore pushes a greater amount of molten metal through the conduit CC than a spherical bubble PSB during a given time period. By varying the shape of the bubble from that of CFB in FIG. 19 to PSB in FIG. 20 and PCB in FIG. 21, the performance and efficiency of the molten metal pump and the conveying conduit CC thereof can be conveniently altered and greatly improved with resulting economic advantage.
Suitable apparatus or means for providing and controlling the gas pulse is illustrated in FIG. 22, which is a schematic of a gas supply system which may conveniently be employed. The inert gas source IGS can be either a tank or a central supply of inert gas from any source. The inert gas must as usual be clean and completely free of water to avoid undesirable eruptions upon introduction of the inert gas into the molten metal mass 26. The operating pressure is set at a predetermined level by the gas pressure regulator GPR. The pressure required will vary, and is determined by the level of molten metal above the inert gas exit port or "nozzle" E. The gas supply pressure must of course be greater than the pressure head created by the molten metal. The feed or flow of gas into the conveying conduit CC via inlet port I, on the other hand, is controlled by the actuated valve AV, which can be any automatic valve capable of turning on and off rapidly as required to provide the gas pulsations, that is, the "on" and "off" segments of the gas-feed and gas-interruption cycles. The action of the valve AV as described is controlled by timers A, for "on" time, and B, for "off" time. The "on" timer A is used to form the bubble to a particular shape or size, such as the pulsed spherical bubble PSB or pulsed cylindrical bubble PCB. By adjusting the "on" timer A and the gas pressure regulator GPR, a bubble of predetermined spherical or cylindrical shape and size, as desired, can be formed in the conveying conduit CC. The "off" timer B controls the time between pulses of the inert gas. Varying the "off" time determines the distance or space between the bubbles PSB or PCB. A larger distance or space allows more room in the conveying conduit CC for the molten metal 26. The combined selection of "off" time, "on" time, and gas pressure is readily employed to establish any desired flow of molten metal in the conveying conduit CC, while at the same time reducing the volume of inert gas required to operate the metal conveying device or pump and its key conveying conduit CC according to the present invention, as will be well understood by one skilled in the art.
IN GENERAL
The method and apparatus of the present invention is particularly adapted for use in connection with the melting and recycling of nonmagnetic metal scrap such as brass, aluminum, aluminum alloys, and the like, and such nonmagnetic metal scrap may conveniently be separated from a mass of metal scrap including also ferrous, ferric, or other magnetic chips by the employment of magnetic separation means, as is now well known and established in the art.
The conveying conduit of the invention as well as the gas feed means of the invention are generally constructed of high-temperature molten metal-resistant ceramic, graphite, silica, or silicon carbide or the like, and the hangers supporting the same within the metal mass are bonded thereto as by welding, clamping, or ceramic or adhesive bonding around the exterior thereof or in some cases may be molded into the ceramic, graphite, silica, or silicon carbide material of construction, or in some cases may even be of mild or stainless or such steel coated or plated with a refractory material.
Where, in this Specification and claims, molten metal, a molten metal mass or pool, and "metal chips" are often referred to, the type of metal in the molten metal pool has already been described, and the term "metal chips" is to be understood as encompassing metal chips of various almost unlimited proportions, configurations, and dimensions, but particularly as including small pieces and/or particles, likewise of extremely variable dimensions, and in general the term "metal chips" is employed herein as having the usual meaning to one skilled in the art, being inclusive not only of parts, pieces, particles, and fragments of the usual type from scrap, but also previously-unused metal in standard or odd configurations remaining from previous molding, extruding, casting, rolling, or like metal processing operations, and it goes without saying that inconveniently large pieces can be reduced in size in any convenient manner and employed as metal chips and that, accordingly, any suitable metal, whether scrap or otherwise, can be converted into chips and employed in the method and apparatus of the invention, whether new metal or previously used metal, including even and especially new and used aluminum sheet and can scrap, when it is determined that such further processing into new metal is required or desired by the operator.
It is thereby seen from the foregoing that the objects of the present invention have been accomplished and that a novel, efficient, and economic method has been provided for the conveyance of a portion of the molten metal mass or pool in a metal-melting furnace employing only an inclined conveying conduit and associated gas feed means through which an inert gas is introduced, the flow of gas into and up the incline of the conveying conduit inducing flow of a portion of the molten metal mass upwardly along the inclined conveying conduit and thereby providing a novel method for providing circulation within the molten metal mass in a metal-melting furnace, including the conveyance of a portion of the molten metal mass from a lower area of the mass to an upper area or level of the mass, from one chamber of the metal-melting furnace to another, from a hotter area of the molten metal mass to a cooler area of the molten metal mass, or even out of the molten metal pool and to an adjacent container, ladle, launder, or furnace if desired, all as described in the foregoing, as well as apparatus for use in carrying out the said process, and whereby all of the previously-mentioned advantages have been attained and the shortcomings of the prior art have been obviated. With the pulsation or intermittent inert gas feed approach according to the present invention, the economic and operating efficiency advantages are still further increased and enhanced.
Although the preferred embodiments of the invention have been illustrated in the accompanying drawings and described in the foregoing description, it is to be understood that the invention is not limited to the embodiments disclosed or to the exact details of operation or exact compounds, compositions, methods, or procedures shown and described, inasmuch as the invention is capable of numerous modifications, rearrangements, and substitutions of parts and elements and other equivalents, whether metallurgical, chemical, or mechanical, without departing from the spirit or scope of the invention, as will readily be apparent to one skilled in the art, wherefore the present invention is to be understood as limited only by the full scope which can be legally accorded the appended claims.

Claims

1. An improved method for the conveyance of molten metal from one place to another in a molten metal pool or mass in a metal-melting furnace or out of said molten metal pool, comprising the steps of:
providing an elongated conveying conduit having a lower end and an upper end, at least a portion of said conduit being inclined upwardly from the horizontal,
providing a gas feed means having a gas inlet port and a gas exit port,
positioning the exit port of said gas feed means with respect to the lower end of said conveying conduit so as to enable release of gas from said exit port into said conveying conduit at or adjacent its lower end,
submerging the exit port of said gas feed means and the lower end of said conveying conduit in a molten metal mass or pool,
intermittently introducing inert gas into said gas feed means through the gas inlet port thereof and causing said gas to emerge from the exit port thereof into said conveying conduit at or adjacent its lower end and to rise up the incline therein, and
inducing concomitant flow of molten metal in said conveying conduit by means of said gas exiting from the exit port of said gas feed means and into said conveying conduit at or adjacent its lower end and rising up the incline therein.
2. The method of claim 1, wherein the method is carried out in a metal-melting furnace.
3. The method of claim 1, wherein the molten metal is caused to be conveyed from a lower portion of said molten metal pool to a higher portion of said molten metal pool.
4. The method of claim 1, wherein the molten metal is caused to be conveyed from a hotter portion of said molten metal pool to a colder portion of said molten metal pool.
5. The method of claim 2, wherein the molten metal is caused to be conveyed from one well or chamber of a metal-melting furnace to another well or chamber thereof.
6. The method of claim 2, wherein the molten metal is caused to be conveyed into a charge well of the furnace.
7. The method of claim 6, wherein the molten metal is caused to be conveyed from a hotter portion of said molten metal pool into a colder portion of said molten metal pool in a charge well of said furnace.
8. The method of claim 2, wherein the molten metal is caused to be conveyed from a hotter area in the main chamber of a metal-melting furnace to another chamber of said furnace.
9. The method of claim 2, wherein the conveying conduit is located in a passageway in a wall of the metal-melting furnace.
10. The method of claim 2, wherein the conveying conduit is provided as a part of a wall of the metal-melting furnace.
11. The method of claim 1, wherein a plurality of conveying conduits are employed.
12. The method of claim 11, wherein said plurality of conveying conduits are provided as a part of a wall of a metal-melting furnace.
13. The method of claim 2, wherein the metal-melting furnace has chambers of different depths, the conveying conduit is positioned between chambers of different depths, and the molten metal is caused to be conveyed from the deeper of the two chambers into the chamber having the lesser depth.
14. The method of claim 1, wherein the molten metal pool comprises magnesium or aluminum or an alloy thereof.
15. The method of claim 1, wherein the inert gas comprises nitrogen or argon.
16. The method of claim 1, wherein the submerged portion of said gas feed means and said conveying conduit are of high-temperature molten metal resistant refractory material.
17. The method of claim 1, including the step of arranging the exit port of said gas feed means so as to be in communication with the interior of the conveying conduit at or adjacent the lower end thereof.
18. The method of claim 1, wherein the temperature of the inert gas is between about -50.degree. and about -100.degree. F.
19. The method of claim 18, wherein the temperature of the inert gas is at about -80.degree. F.
20. The method of claim 1, wherein the pressure at which the inert gas is released at the exit port of the inert gas feed means is up to about 150 psi.
21. The method of claim 20, wherein the pressure at which the inert gas is released at the exit port of the inert gas feed means is between about 20 and about 60 psi.
22. The method of claim 18, wherein the temperature of the molten metal bath is between about 1200.degree. and about 1500.degree. F.
23. The method of claim 1, wherein the temperature of the inert gas is between about -50.degree. and about -100.degree. F. and the pressure under which the inert gas is released from the exit port of the inert gas feed means is between about 20 and about 60 psi.
24. The method of claim 23, wherein the temperature of the molten metal pool is between about 1250.degree. and about 1450.degree. F.
25. The method of claim 1, wherein the conveying conduit has an inclined reach from its lower end to its upper end.
26. The method of claim 1, wherein the conveying conduit has an inclined reach and a substantially horizontal reach.
27. The method of claim 1, wherein the conveying conduit has an inclined reach and a substantially horizontal reach at the upper end thereof.
28. The method of claim 1, wherein the conveying conduit has an inclined reach and a substantially horizontal reach at both the upper end thereof and the lower end thereof.
29. The method of claim 1, wherein the conveying conduit is in the form of a flattened Z.
30. The method of claim 1, wherein the conveying conduit has an inclined reach and a substantially horizontal reach at an end of said inclined reach, and wherein the inclined reach and the substantially horizontal reach lie in different vertical planes.
31. The method of claim 1, wherein the conveying conduit has an inclined reach and a substantially horizontal reach at a lower end thereof, and wherein inert gas is introduced into said conveying conduit at or near the bottom or commencement of its inclined reach.
32. Improved molten metal conveying means suitable for conveying molten metal from one place to another in a molten metal pool or mass in a metal-melting furnace or out of said molten metal pool, comprising in combination:
intermittent inert gas feed means adapted for feeding inert gas intermittently and comprising a gas inlet port and a gas exit port, at least a portion thereof adapted to be submerged in a molten-metal bath comprising high-temperature and molten-metal resistant material,
an elongated conveying conduit of high-temperature molten-metal resistant material having a lower end and an upper end, at least a portion of said conduit being inclined upwardly from the horizontal,
the exit port of said inert gas feed means being associated with said conveying conduit at or near the lower end thereof so as to enable release of inert gas from said exit port of said gas feed means into said conveying conduit at or adjacent a lower end thereof, thereby to induce concomitant flow of molten metal in said conveying conduit.
33. The means of claim 32, adapted to be mounted in a molten metal pool in the interior of a metal-melting furnace.
34. The means of claim 32, supported in place in a molten metal mass or pool in a metal-melting furnace.
35. The means of claim 34, wherein the molten metal mass or pool is in a metal-melting furnace having one chamber deeper than another chamber, and wherein the lower end of said conveying conduit is in the deeper chamber and the upper end of said conveying conduit is in said shallower chamber.
36. The means of claim 32, mounted in a passageway in a wall between chambers or wells of a metal-melting furnace.
37. The means of claim 32, built into a wall between chambers or wells of a metal-melting furnace.
38. The means of claim 32, comprising a single conveying conduit.
39. The means of claim 32, comprising a plurality of conveying conduits.
40. The means of claim 32, comprising a plurality of conveying conduits and wherein said gas feed means communicates with said plurality of conveying conduits at or near the lower end thereof.
41. The means of claim 37, wherein the conveying conduit is supported in said wall by means of a sleeve around the exterior thereof.
42. The means of claim 32, wherein the exit port of said gas feed means is in communication with the interior of the conveying conduit at or adjacent the lower end thereof.
43. The means of claim 32, wherein the conveying conduit has an inclined reach from its lower end to its upper end.
44. The means of claim 32, wherein the conveying conduit has an inclined reach and a substantially horizontal reach.
45. The means of claim 32, wherein the conveying conduit has an inclined reach and a substantially horizontal reach at the upper end thereof.
46. The means of claim 32, wherein the conveying conduit has an inclined reach and a substantially horizontal reach at both the upper end thereof and the lower end thereof.
47. The means of claim 46, wherein the conveying conduit is in the form of a flattened Z.
48. The means of claim 32, wherein a portion of the gas feed means is comprised as a part of a hanger adapted to support the conveying conduit in a molten metal pool.
49. The means of claim 32, wherein the gas feed means comprises a block which supports said conveying conduit, said block having therein a passageway comprising the exit port of said gas feed means.
50. The means of claim 49, wherein said passageway is a circular passageway surrounding said conveying conduit and wherein said exit port is located in said circular passageway.
51. The means of claim 32, wherein the conveying conduit has an inclined reach and a substantially horizontal reach at an end of said inclined reach, and wherein the inclined reach and the substantially horizontal reach lie in different vertical planes.
52. The means of claim 32, wherein the conveying conduit has an inclined reach and a substantially horizontal reach at a lower end thereof, and wherein inert gas is introduced into said conveying conduit at or near the bottom or commencement of its inclined reach.
53. The means of claim 32, wherein the conveying conduit is at least partially in the form of a passageway in a block of refractory material.
54. The means of claim 53, comprising a plurality of conveying conduits at least partially in the form of passageways in a block of refractory material.
55. The means of claim 53 or 54, wherein the gas inlet means also at least partially comprises a passageway in said block of refractory material.
56. The method of claim 2, 5, or 6, wherein inert gas is retained at the surface of the molten metal mass to impede or prevent oxidation thereof.
57. The means of claim 32, wherein the inert gas feed means is adapted to provide a pressure of inert gas at the exit port of the inert gas feed means of up to about 150 psi.
58. The means of claim 32, wherein the inert gas feed means is adapted to provide a pressure of inert gas at the exit port of the inert gas feed means of between about 20 and about 60 psi.
59. The method of claim 1, wherein the intermittent introduction of inert gas is controlled so as to provide substantially spherical inert gas bubbles in said conveying conduit.
60. The method of claim 1, wherein the intermittent introduction of inert gas is controlled so as to provide substantially cylindrical inert gas bubbles in said conveying conduit.
61. The method of claim 1, wherein the intermittent introduction of inert gas involves an "on" time between about 0.02 and 0.08 second and an "off" time between about 0.01 and 0.05 second.
62. The method of claim 1, wherein the intermittent introduction of inert gas involves an "on" time of about 0.05 second and an "off" time of about 0.03 second.
63. The means of claim 32, wherein the means for intermittent inert gas feed is adapted to provide substantially spherical inert gas bubbles in said conveying conduit.
64. The means of claim 32, wherein the means for intermittent inert gas feed is adapted to provide substantially cylindrical inert gas bubbles in said conveying conduit.
65. The means of claim 32, wherein the means for intermittent inert gas feed is adapted to provide an "on" time between about 0.02 and 0.08 second and an "off" time between about 0.01 and 0.05 second.
66. The means of claim 32, wherein the means for intermittent inert gas feed is adapted to provide an "on" time of about 0.05 second and an "off" time of about 0.03 second.

Parent Case Info

The present application is a continuation-in-part of my prior-filed copending application Ser. No. 07/799,114, filed Nov. 27, 1991, now U.S. Pat. No. 5,203,910, issued Apr. 20, 1993.

US Referenced Citations (1)

Number	Name	Date	Kind
3867132	Perry	Feb 1975

Continuation in Parts (1)

	Number	Date	Country
Parent	799114	Nov 1991

Molten metal conveying means and method of conveying molten metal from one place to another in a metal-melting furnace using intermittent or pulsating insert gas feed

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CPC

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Parent Case Info

US Referenced Citations (1)

Continuation in Parts (1)