US3869112A

US3869112A - Method and apparatus for melting metals, especially scrap metals

Info

Publication number: US3869112A
Authority: US
Inventors: Khaled M Habayeb
Original assignee: Wabash Alloys Inc
Current assignee: CONNELL INDUSTRIES LP ONE MASS TECH CENTER BOSTON MA 02128; Avondale Industries Inc
Priority date: 1973-09-18
Filing date: 1973-09-18
Publication date: 1975-03-04
Anticipated expiration: 1992-03-04
Also published as: FR2296154A1; FR2296154B1

Abstract

A method for melting metals, and an apparatus in which metals, particularly scrap metals, are melted, especially scrap metal which are contaminated with substances, such as oil or the like, which will give off hydrocarbon emissions when the metal is heated. Advantageously, the apparatus collects the hydrocarbon emissions and supplies the emissions to a place of combustion which may be, for example, the burners which are supplying heat to the respective furnace, to the base of the stack of the furnace, to the furnace downstream of the burners, or to burners for another furnace, or to a burner for a heated ladle. The furnace is so constructed that the chamber in which the metal is melted extends beyond the furnace enclosure to form a charging well and an enclosure is erected around the charging well which, at the top, forms a hood in which the emissions are collected and from which the emissions are withdrawn at least as rapidly as the emissions are generated from the metal introduced into the charging well. Advantageously, the furnace is heated by gas burners and the emissions are supplied to the gas burners as combustion air. During periods of hydrocarbon emissions from the metal being melted which exceed the requirements of the burners for combustion air, at least some of the emissions can be conveyed from the enclosure surrounding the charging well to another burner, for example, a burner for another furnace, or for a ladle in which molten metal is transported to a place of use. The emission can also be burned by injection thereof into the furnace or the base of the stack of the furnace. The result of collecting the emissions and conveying the emissions to a place of combustion, is a great reduction in the emissions from a melting furnace of the nature referred to a level well below the allowable level established by pollution control codes while, at the same time, a substantial economy can be realized if the emissions are burned where the heat therefrom is useful.

Description

United States Patent [1 1 Habayeb 1 Mar. 4, 1975 1 METHOD AND APPARATUS FOR MELTING METALS, ESPECIALLY SCRAPMETALS [75] Inventor: Khaled M. llllabayeb, Wabash, Ind.

[73] Assignee: Wabash Alloys 1nc., Wabash, 1nd.

122] Filed: Sept. 18, 1973 [21] Appl. No.: 398,336

[52] US. Cl. 266/33 S, 75/44 S, 75/43 [51] Int. Cl. F27b 19/00 [58] Field of Search 266/15, 16, 19, 33 R, 33 S;

[56] References Cited UNITED STATES PATENTS 1,675,542 7/1928 Frazier 266/33 R 2,065,207 12/1936 Betterton 266/33 R 2,092,145 9/1937 Wanner 266/33 R 2,204,173 6/1940 Bowser.... 266/33 R 2,264,740 12/1941 Brown 266/33 R 2,465,545 3/1949 Marsh 266/33 R' 2,562,441 7/1951 Stroman 266/33 R 2,987,391 6/1961 Foster et a1. 266/33 R 3,614,079 10/1971 Harrison et a1 266/33 S 3,645,516 2/1972 Turpin et a1. 266/16 3,667,747 6/1972 Graybill et al 266/33 S Primary Examiner-Gerald A. Dost I Attorney, Agent, or Firm-Albert L. Jeffers; Roger M. Rickert [57] ABSTRACT A method for melting metals, and an apparatus in which metals, particularlyscrap metals, are melted, especially scrap metal which are contaminated with substances, such as oil or the like, which will give off hydrocarbon emissions when the metal is heated. Advantageously, the apparatus collects the hydrocarbon emissions and supplies the emissions to a place of combustion which may be, for example, the burners which are supplying heat to the respective furnace, to the base of the stack of the furnace, to the furnace downstream of the burners, or to burners for another furnace, or to a burner for a heated ladle. The furnace is so constructed that the chamber in which the metal is melted extends beyond the furnace enclosure to form a charging well and an enclosure is erected around the charging well which, at the top, forms a hood in which the emissions are collected and from which the emissions are withdrawn at least as rapidly as the emissions are generated from the metal introduced into the charging well. Advantageously, the furnace is heated by gas burners and the emissions are supplied to the gas burners as combustion air. During periods of hydrocarbon emissions from the metal being melted which exceed the requirements of the burners for combustion air, at least some of the emissions can be conveyed from the enclosure surrounding the charging well toanother burner, for example, a burner for another furnace, or for a ladle in which molten metal is transported to a place of use. The emission can also be burned by injection thereof into the furnace or the base of the stack of the furnace. The result of collecting the emissions and conveying the emissions to a place of combustion, is a great reduction in the emissions from a melting furnace of the nature referred to a level well below the allowable level established by pollution control codes while, at the same time, a substantial economy can be realized if the emissions are burned where the heat therefrom is useful.

7 Claims, 6 Drawing Figures PATENTEWR 5 3,869,112

sum 2 or 3 F "El. 3

IO 20 I6 J 0- 24 56 66 65 3 I 50 65 64 I 62 g f ,52. m 68 m Q' 66 42 I8 58 5 FIELB Z8 9O iffiFiFFtU 45975 SHLU 3 Ui 3 FIEA- FIE 5 FIEE METHOD AND APPARATUS FOR MELTING METALS, ESPECIALLY SCRAP METALS The present invention relates to a method and apparatus for melting metals, particularly scrap metals contaminated with oil and the like which generate hydrocarbon emissions upon the heating of the metal.

The melting of scrap metals for reuse is a wellknown procedure but, quite often, the scrap metals are contaminated with oils, such as cutting oils, and the like, and the contaminating material will be volatilized when the metal is heated and will pass off from the metal as an undesireable atmospheric pollutant. Such emissions, due to the fact that the principal contaminant of scrap metal is oil, are essentially hydrocarbon in nature and are quite objectionable when discharged directly into the atmosphere.

A number of different schemes have been proposed for collecting such emissions to prevent them from entering the atmosphere, but heretofore, arrangements for accomplishing this have been expensive and imperfect in operation and have represented no economy whatsoever in respect of the melting of the scrap metal for reuse.

With the foregoing in mind, a primary objective of the present invention in the provision of a method and apparatus for melting metals, particularly scrap metals, in which emissions from the metals being heated, particularly hydrocarbon emissions, are collected and conveyed away from the region where the emissions are generated to a place of combustion while, furthermore,

the emissions are employed in such a manner that the heat content thereof is realized in a useful manner.

Another object of the present invention is the provision of a melting furnace, especially for scrap metals, which is particularly constructed to eliminate emissions to the outside atmosphere from metals which are placed in the furnace to be melted.

Still another object is the provision of a furnace arrangement of the nature referred to in which emissions from the metal being melted, particularly hydrocarbon emissions, are utilized as combustion air either in the burners for the furnace in which the metal is being melted or in another furnace or other instrumentality having a burner therein.

BRIEF SUMMARY OF THE INVENTION According to the present invention a furnace, such as a reverberatory furnace is provided in which the metal is melted in a chamber in the bottom of the furnace. According to the present invention the chamber is extended beyond the end wall of the furnace which is opposite the end wall having the furnace burners and stack and this extended portion of the melting chamber forms a charging well into which the metal to be melted is introduced.

According to the present invention an enclosing structure is erected about the charging well having a hood portion at the top to collect emissions that are given off by metal placed into the charging well to be melted. The hood portion of the enclosure erected about the charging well has, at the top, at least one duct leading therefrom which is connected to the suction side of a blower. The end wall of the furnace opposite the end from which the charging well projects is provided with burners, preferably gas burners, and the discharge side of the aforementioned blower is connected to these burners to supply the combustion air thereto, or leads to other burners, or to the base of the stack of the respective furnace.

The. enclosure erected about the charging well has an operators opening, or window, through which an operator can observe the conditions of the metal in the melting chamber and also has an opening through which the metal to be melted is introduced into the charging well. This last mentioned opening may be large enough to admit a powered lift truck or the like which conveys batches of metal to the charging well but, alternatively, the metal could. be supplied to the charging well by a conveyer arrangement thereby permitting the opening in the enclosure through which metal is conveyed to be smaller.

It is proposed to shield both openings provided in the enclosure by air curtains so that no emissions escape from the enclosure whereby all of the emissions are withdrawn from the enclosure by the duct or ducts connected to the upper hood portion thereof.

Under normal circumstances, all of the emissions can be conveyed to the aforementioned gas burners as combustion air for the gaseous fuel supplied thereto but, if the emissions from the metal supplied to the charging well exceed the amount that can be delivered to the gas burners, at least a portion of the emissions can be conveyed either to other gas burners, or are injected into the base of the stack leading from the furnace, or are injected into the furnace downstream from the burners. In every case, except where the emissions are injected into the stack, the heat of combustion of the emissions is realized in respect of heating metal.

It has been found that, by supplying the emissions to a place of combustion as referred to above, the total emissions from a furnace of the nature referred to are reduced to a fraction of the maximum allowed by pollution codes while, at the same time, a substantial fuel economy is also realized.

The objects referred to above, as well as other objects and advantages of the present invention, will become more apparent upon reference to the following detailed specification taken in connection with the accompanying drawings in which:

FIG. 1 is a perspective view showing a pollution control device according to the present invention associated with a reverberation melting furnace.

FIG. 2 is a plan section indicated by line 2-2 on FIG. 1.

FIG. 3 is a longitudinal vertical section indicated by line 3--3 on FIG. 2.

FIG. 4 is a fragmentary view showing a conveyor arrangement for charging the furnace.

FIG. 5 is a fragmentary perspective view showing the manner in which emissions can be introduced into the base of the furnace stack.

FIG. 6 is a fragmentary perspective view showing how the emissions can be injected in the furnace downstream from the main furnace burners.

DETAILED DESCRIPTION OF THE INVENTION:

Referring to the drawings somewhat in more detail, FIG. 1 somewhat schematically illustrates an arrangement of the nature with which the present invention is concerned. At the left side of the arrangement shown in FIG. I, and indicated generally at 10, is a substantially conventional reverberatory furnace having an end wall 52 in which gas burners l4 and 16 are mountedTheseburners are supplied with

gasby conduits

18 and 20 and each is supplied with combustion air by

respective duct

22, 24. The ducts 22 and. 24 lead to the discharge side of a blower 26, the inlet side of which is connected to a further duct 28. Duct 28 leads to an upper portion of a fume collecting hood 30 forming the upper part of an enclosure generally designated 32, at the right side of FIG. 1, and which may be sheet metal supported on a suitable steel frame.

Enclosure 32 has an opening 34 therein in the end facing away from furnace of the size to admit a lift truck, or the like, and which is adapted for conveying metal to be melted which is to be delivered into the melting chamber forming a part of the furnace 10.

One side wall of enclosure 32 is provided with an opening 38 adjacent which is an operators platform 40. An operator on platform 40 can observe the melting chamber through window 38 and perform agitating operations of the metal melt or control other devices as will become more apparent hereinafter.

' Each of the

openings

34 and 38 is provided with air curtain means, a portion of which is indicated at 42 for opening 34, and at 44 for opening 38. The air curtains may be substantially conventional in design and consist of means for projecting a high velocity jet, or curtain, of air across the respective opening and which air may be collected by a suction fitting at the opposite side of the opening and then recirculated. In any event, the devices at 42 and 44 represent means for maintaining a curtain of air at each of the openings 34 and- 38 which will prevent the escape from the enclosure of emissions generated therein.

In respect of the main opening 38, it is of advantage to connect the suction side of the air curtain blower 39 to the side of enclosure 32 adjacent device 44 by a duct 41. The air curtain for opening 38 is thus formed by gassesfrom within enclosure 32 drawn therefrom by blower 39 and' then projected at high velocity across opening 38. I

Reference to FIGS. 2 and 3 will show in more detail the construction of the furnace and the arrangement of the enclosure about the charging well portion of the melting chamber of the furnace.

In FlGS. 2 and 3 it will be noted that the furnace comprises a refactory bottom wall 50, a refractory end wall 52, a refactory top wall 54, and refractory side walls 56. and 58. The end wall 52 is the wall in which the

gas burner

14 and 16 are mounted and also connected to this wall at a location between the burners is a discharge stack 60 from which the products of combustion leave the furnace.

Spaced from end wall 52 is a second end wall 62 extending from side to side in the furnace between

side walls

56 and 58 and extending downwardly from top wall 54. The bottom portion of the furnace forms a melting chamber and the melting chamber is extended beyond end wall 62 to form a charging well region 64. It is into the charging well region that the metal to be melted is delivered.

The end wall 62 has two or more posts at the bottom defining a pair of ports, openings, or slots 66 extending upwardly in end wall 62 from the bottom wall of the furnace. Slideably mounted on wall 62 are refractory doors 68 which can be adjusted vertically so as to expose ports 66 or so as to depend below the upper edges of ports 66. The effective area of ports 66 for the circulation of metal between the melting and charging chambers can be varied by adjusting doors 68 while, also doors 68 can seal the furnace chamber off from the enclosure 32. Guides 65 guide doors 68 and a mechanism can be provided for moving the doors vertically and for holding the doors in adjusted positions thereof.

FIG. 3 will also show that there is a tap hole 70 provided in the furnace near the bottom and beneath the

burners

14, 16 adapted for being closed by plug 72. When the desired amount of melt is accumulated in the melting chamber of the furnace, plug 72 can be withdrawn to release the molten metal. This metal can be poured into molds to form'pigs, or sows, or it can be delivered to a ladle in which it is maintained molten and in which ladle the metal is conveyed from the furnace to a place of use. Such a ladle is shown, for example, in the Thakar, et. al., US. Pat. No. 3,400,859.

In operation, it is preferable always to maintain at least a small amount of molten metal in the melting chamber because this facilitates the melting of new metal supplied to the charging well of the melting chamber.

Assuming that a scrap metal such as aluminum is to be melted, a quantity of aluminum up to as much as 2,000 pounds at a time can be introduced into charging well 64. v

The

burners

14, 16, supply about 12 to 19 million btus per hour and the temperature developed in the furnace immediately above the metal in the melting chamber will reach about 2,200to about 2,300 F.

Within the enclosure 32, however, which is substantially completely isolated from the hot blast from the burners by end wall 62, the temperature will only reach about degrees F. in the lower region thereof, while at the top of the enclosure in the collecting hood portion, the temperature will only reach about 200 to 250 F.

Assuming that the quantity of scrap metal to be melted has been dumped into the charging well, there will be an interval of at least about 10 seconds before the emissions therefrom reach a maximum. Thus, even if a lift truck is employed for conveying the scrap metal into the charging well, the operator has ample time to back completely out of the enclosure about the charging well before the emissions from the charged-in scrap metal reach a .maximum.

Within about five minutes after dumping a new charge of scrap metal into the charging well, the atmosphere within the enclosure about the charging well will again be relatively clear.

The emissions, together with air, are withdrawn from the fume collecting hood 30 at the top of the enclosure by duct 28 and are conveyed to blower 26 and then to

burners

14, 16, as combustion air at a temperature of up to about 250 F., and the hydrocarbons in the emissions will be substantially completely burned. The solids passing off of the furnace via stack 60 will be quite small. It is estimated that the maximum amount of solids passing out of stack 60 when the furnace is operating at maximum capacity will be about one-third of what is allowable under pollution codes. While, by the practice of the present invention, unburned volatilized hydrocarbon emissions to the atmosphere is completely prevented.

The arrangement described above utilizes a lift truck for conveying the scrap metal to the charging well. Scrap metal thus conveyed might be in a box and be discharged from the box into the charging well or it could be in the form of a bale and be delivered in bale form into the charging well. In bothcases, the metal is supplied in batches of substantial volume.

It is also possible, however, to provide for a more uniform rate of supply of the metal to the charging well, thereby providing for a more uniform rate of generation of emissions and this can be accomplished by supplying the metal to the charging well by a conveyor arrangement such as is shown in FIG. 4.

In FIG. 4, the conveyor 80 is supplied with scrap metal externally of enclosure 32 and conveys the metal through the opening 82 in the enclosure wall to adjacent the charging well and discharges the material into the charging well either directly or via, for example, an inclined vibratory plate. By utilizing a conveyor, as shown in FIG. 4, the rate of charging of the furnace can be made substantially uniform and thereby provide for a uniform rate-of discharge of the emissions from the charged-in metal to be conveyed to the burners for combustion air.

Even when the best regulated conditions are maintained, the amount of contaminant in the metal being melted will vary and, likewise, the specific rate at which the metal is charged into the charging well will vary, especially when the metal is charged into the well in large batches, as by a lift truck. For these reasons, the rate at which emissions are given off, or generated, at the charging well may vary quite widely. Under certain conditions the amount of emissions given off the metal at the charging well might be in excess of what can be utilized as combustion air for the burners pertaining to the furnace. In such a case, a certain amount of the emissions may be diverted through a diverting duct 90 connected either to the fume collecting hood 30 or to duct 28 upstream from the inlet of blower 26.

These diverted emissions may be conveyed to burners for another furnace as combustion air or may be conveyed to a burner pertaining to a ladle which conveys molten ,metal to a point of use, or to another place of combustion.

As a measure of the amount of emissions given off at the charging well, a thermostat 92 could be provided in the fume collecting hood 30. It follows that, at the temperature at which the metal delivered to the charging well willmelt, there will be some burning of the emitted vapors, or of the hydrocarbon contaminants of the metal, and such burning will cause the temperature in the fume collecting hood 30 to vary.

Variations in this temperature can be detected by thermostat 92 and this thermostat can then be employed to regulate the amount of the-emissions that is diverted from

burners

14, 16. This diversion might take the form of varying a damper 91 in diverting duct 90, when the duct is under suction, or of controlling a blower 93, or by controlling both of the damper and blower. It is preferable for the diverting to take place on the upstream side of blower 26 so that the blower will always supply the required volume of combustion air to the burners.

The emissions diverted from fume collecting hood 30 can be injected into the base of stack 60 as shown in FIG. 5 as by a duct 95 through which some or all of the emissions from fume collecting hood 30 are injected into the base of stack 60. The exhaust gases from the furnace entering the base of stack 60 are at about l,800 F. and, at this temperature, the emissions from the hood 30 which areinjected into the stack will burn. The added heat in the stack will reduce the pollutants that will be discharged from stack 60.

FIG. 6 shows an arrangement which includes a duct 98 for injecting emissions directly into the furnace compartment downstream from burners l4 and 16. The emissions will be introduced into a temperature ranging up to about 2,300 F., and will readily burn with the heat developed thereby being useful in heating the metal in the melting chamber.

It is also contemplated to supply the diverted emissions to another burner, or burners, to serve as combustion air therefor, such as burners associated with an other furnace or with a ladle in which molten metal is conveyed to a point of use. i

The arrangement of the present invention is such that, at all times, the emissions given off by the metal being melted are completely collected and conveyed away to a place of combustion and which place of combustion may be a place where the heat developed by the burning hydrocarbon material is useful.

The specific temperatures given above are for aluminum although it will be understood that other metals can be melted in the apparatus of the present invention, and according to the process of the present invention, merely by adjusting the temperatures to that desired.

In arriving at a melt, a sample of the molten metal will be taken from the furnace and analyzed and, then, additives can be supplied to the melt, via the charging well, for example, in order to bring the melt to the proper metallurgical consistency. When the melt is at the proper metallurgical consistency, the furnace is tapped in the manner referred to above. Preferably, the furnace is only tapped to the point that the level of molten metal is reduced substantially therein leaving at least a small amount of molten metal in the melting chamber so that metal newly added to the melting chamber at the charging well-end will quickly melt.

The operator previously referred to who observes the melt through the side window opening 38 in the enclosure can perform certain useful operations. For example, the operator can control the adjustment of the ver' tically moveable doors 68 to control the ports in the end wall 62 and, furthermore, the operator can effectively agitate the melt when this is necessary as, for example, by a wand supplied with an inert gas such as nitrogen under pressure.

The gases from stack 60 may be cleaned in any conventional manner, if desired, as by passing the gases through a cyclone, or through a bag cleaner, or through a scrubber, or any combination thereof.

A typical arrangement according to the present invention might be about 28 feet long and about 15 feet wide with the enclosure having a heigth of about 12 feet. Such an installation could produce a melt of as much as 125,000 pounds, although smaller melts can be made when necessary. These figures are, however, only exemplary.-

Modifications may be made within the scope of the appended claims.

What is claimed is:

1. A reverberatory furnace having bottom, end, side and top walls and having a melting; chamber portion in the lower region thereof, one of said end walls being provided with port means extending upwardly from the bottom and terminating near the top of said chamber portion, said chamber portion extending beyond said from said furnace, an enclosure surrounding said.

charging well and including a dome at the top for collecting emissions given off by contaminated metal charged into the said charging well, blower means having suction means connected to said dome and having discharge means connected to said burner means to supply combustion gas thereto, said enclosure having at least one opening through which metal to be charged into said charging well is conveyed into saidenclosure from the outside, and an air curtain forming an air screen at said opening to prevent the escape of emissions from said enclosure via the opening.

2. A reverberatory furnace according to claim 1 wherein the burner means includes two burners in laterally spaced relation, and a stack for exhaust gases being positioned on said other end wall between the two laterally spaced burners.

3. A reverberatory furnace according to claim 1 wherein said blower means includes a first blower having a discharge connected to said burner means to supply combustion gas thereto and a second blower means having the suction side connected to said dome and having a discharge side connected to the melting chamber portion of said furnace downstream from said burner means.

4. A reverberatory furnace according to claim 3 wherein the discharge side of the second blower means is connected to both the melting chamber and said stack.

5. A reverberatory furnace according to claim 3 which includes control means for controlling the volume of gas withdrawn from said enclosure by said second blower.

6. A reverberatory furnace according to claim 3 wherein the discharge side of the second blower means is connected to the stack.

7. A reverberatory furnace according to claim 1 wherein said enclosure includes a further opening adjacent said one end wall for access to said charging well so that an operator can perform agitating operations of the metal melt, and a further air curtain screening said further opening.

Claims

1. A reverberatory furnace having bottom, end, side and top walls and having a melting chamber portion in the lower region thereof, one of said end walls being provided with port means extending upwardly from the bottom and terminating near the top of said chamber portion, said chamber portion extending beyond said one end wall to form a charging well into which metal to be melted is charged, burner means positioned in the other end wall and a stack connected to said other end wall adjacent the burner means to convey exhaust gases from said furnace, an enclosure surrounding said charging well and including a dome at the top for collecting emissions given off by contaminated metal charged into the said charging well, blower means having suction means connected to said dome and having discharge means connected to said burner means to supply combustion gas thereto, said enclosure having at least one opening through which metal to be charged into said charging well is conveyed into said enclosure from the outside, and an air curtain forming an air screen at said opening to prevent the escape of emissions from said enclosure via the opening.