US3603571A

US3603571A - Apparatus for melting scrap metal

Info

Publication number: US3603571A
Application number: US659946A
Authority: US
Inventors: Lewis J Geiger Jr; James W Estes
Original assignee: Air Reduction Co Inc
Current assignee: Airco Inc
Priority date: 1967-08-11
Filing date: 1967-08-11
Publication date: 1971-09-07
Anticipated expiration: 1988-09-07

Abstract

In a shaft furnace, method and apparatus for melting low density metallic scrap. Burners and/or tuyeres are located at two different levels in the body portion of the furnace. The charge is preheated by hot gases rising in the furnace stack, and melted at the upper burner level. As the molten metal trickles down over a support bed, which may either be coke, other types of carbon, or a refractory material, it is superheated to the desired spout temperature, and to provide a product of the desired analysis. A feature is the configuration of burners which imposes a swirling motion on gases entering the furnace.

Description

ts it [72] Inventors Lewis 11. Geiger, Jr.

Edison; James W. Estes, Piscataway, both of, NJ. [2]] Appl No. 659,946 221 Filed Aug.lll, 1967 [451 Patented Sept. 7,1971 [73] Assignee Air llteduction Company, incorporated New Yorlli, NY.

[54] APiPAllMTUS FOR MELTING SClltAlP METAL 15 Claims, 3 Drawing Figs.

[52] 11.5. CI 266/25, 75/43, 263/29 [51] 11nt.Cl C216 7/16 [50] Field of Search 266/14, 25, 40,41, 24,29,13, 27, 33, 1 1; 263/29; 75/41,43

[56] References Cited UNITED STATES PATENTS 455,458 7/1891 Eames 266/25 X 485,392 11/1892 Koneman 266/25 X 3,418,108 12/1968 Von Stroh 75/43 1,880,012 9/1932 Brassert 266/25 X 2,052,928 9/1936 Harris 266/25 X 2,184,300 12/1939 Hodson et a1 266/25 X 3,350,084 10/1967 Lucarell 266/41 580,427 4/1897 Sattmann 266/1 1 1,948,696 2/1934 Brassert et al. 266/11 2,161,180 6/1939 Marx 266/25 X 2,788,964 4/1957 Schnyder 266/25 3,199,977 8/1965 Phillips et al. 1. 266/33 X FOREIGN PATENTS 994,395 6/1965 Great Britain 75/43 Primary Examiner.l. Spencer Overho1ser Assistant Examiner-.lohn S. Brown Attorneys-Francis B. Henry, Edmund W. Bopp and H. Hume Mathews MESTNACT: In a shaft furnace, method and apparatus for melting low density metallic scrap. Burners and/or tuyeres are located at two different levels in the body portion of the furnace. The charge is preheated by hot gases rising in the furnacc stack, and melted at the upper burner level. As the molten metal trickles down over a support bed, which may either be colte, other types of carbon, or a refractory material, it is superheated to the desired spout temperature, and to provide a product of the desired analysis. A feature is the configuration of burners which imposes a swirling motion on gases entering the furnace.

PATENTED SEP 7 l9?! SECTION AT LOWER BURNERS FIG. 28 SECTION AT UPPER BURNERS J. w. ESTES gi L. J. 65/651? #1? f ATTORNEY APPARATUS lFOllt MELTIING SCRAP METAL BACKGROUND OF INVENTION This relates in general to the processing or melting of metal in shaft furnaces, and more particularly to the melting of low density metallic scrap to liquid metal of specified analyses.

In the prior art, it has been difiicult to process scrap comprising borings, turnings, and other types of low density metallic material, because of the excessive oxidation which such materials sustain, and also, because of the high volume-toweight ratio in materials of this type. Accordingly, certain preconditioning processes were necessary, such as, for example, binding together a group of materials called bundling," which ultimately raised the expense of the process. Moreover, under prior practices, it has been difficult to regulate the final tap temperature of the molten metal product, or the volume of the gas passing through the furnace, so as to precisely control the analysis of the final metal product. Finally, metal melting operations as carried out in the prior art are known to contribute heavily to air pollution.

Accordingly, it is the general object of this invention to provide a process of improved efficiency over the prior art for melting low density scrap, such as borings, turnings, sheet bundles, tube mill scrap, bunchings, and sheet trimmings, which are melted with difficulty. More particular objects of the invention are to more precisely control the superheating of the molten charge, and hence, the analysis of the final product. Another object of the invention is to reduce air pollu tion products contributed by metal processing furnaces.

BRIEF DESCRIPTION OF THE INVENTION These and other objects are accomplished in accordance with the present invention in a shaft furnace having a preheating zone, a melting zone, and a superheating zone. The metal charge, which is preheated by rising gases in the stack portion, is melted in the melting zone by heat supplied from upper level oxyfuel burners. The molten metal then trickles down over a porous support bed, and is simultaneously superheated to the desired spout temperature by heat supplied from a lower set of burners or tuyeres.

In one example of practice of the present invention, metal scrap, comprising, for example, a major portion of iron, is charged into the top of the furnace. One row of oxyfuel burners which is disposed at a level above a bed of coke, serves together with rising gases to preheat the charge and to provide a major part of the latent heat of fusion. A second row of tuyeres, at a substantially lower level in the coke bed, serves either to house oxyfuel burners, or to convey separately highly enriched air to support combustion of the coke, thereby superheating the molten metal, as it trickles down through the coke, to the desired spout temperature. It will be understood that at either the upper or lower level, the burners can be employed with or without an auxiliary airblast through the tuyeres.

In accordance with a modification of the invention, the coke bed can be replaced with inert refractory material, such as magnesia, lime, calcium carbide, or alumina, which is also heated by means of oxyfuel burners in the lower set of tuyeres for the purpose of superheating the molten metal as it descends. The purpose of this modification is to remove from the furnace certain components which may be detrimental to the metallic product, and add others which may be beneficial. For example, the presence of sulfur in coke is detrimental to the melting of copper; hence, the coke is replaced with a support bed of alumina. In another example, special support media such as calcium oxide and calcium carbonate have been found to contribute to the desulfurization and dephosphorization of scrap steel.

One feature of the processes of the present invention is that the melting rate of the molten metal can be controlled by the firing rate of the oxyfuel burners firing directly on the preheated scrap as it descends into the melting zone.

Another feature of the invention is the arrangement of the burners to impose a swirling motion on gas passing into the furnace. In accordance with a particular configuration disclosed, each of the burner barrels is so directed that it makes an angle of approximately 15 with the radius of the circular cross-sectioned furnace. In a preferred arrangement, the burner barrels at one furnace level are directed at clockwise angles with the radius, whereas at the other level, they are oppositely directed, thus causing the entering gases to swirl in opposite directions. Moreover, the burners are each directed downwardly at an angle of between 10 and 15 with the horizontal. Because of this particular burner configuration, the contact time between hot burner gases and the scrap charge is substantially increased over that usual in the prior art.

In accordance with another feature of the invention, the atmospheres produced in the various zones can be varied at will to produce oxidizing, reducing or neutral conditions, depending on the metal melted. For example, brass scrap can be pre' heated and melted above the support bed under oxidizing con ditions to remove zinc from the brass, to leave copper. The lower burners can then be operated to produce reducing or neutral conditions in the superheating zone to prevent oxidation of the remaining copper in the original brass alloy.

A further feature of this invention is the ability to separately regulate the thermal energy input at each level to accommodate the differences in metal melting requirements. Each metal requires a different level of thermal energy input and each metal requires a percentage of this total for preheating, melting and superheating, as demonstrated by the data of Table l in the detailed specification hereinafter.

Still another feature of the invention is the ability to control flame temperature at each of the two burner levels to suit the metal being melted. Flame temperature at each zone can be controlled by varying the percentage of air in the tuyere. In the case where burners are not used at the lower tuyere level, oxygen enrichment of the blast air can be varied to produce desired flame temperatures in the coke bed.

Some of the advantages of the techniques of the present invention over the teachings of the prior art are as follows:

I. Light, low density scrap, comprising, for example, borings and turnings, are melted without excessive oxidation.

2. Low density scrap can be charged without prior conditioning, such as bundling.

3. The degree of superheating, that is, the final tap tempera ture at which the liquid metal arrives, can be regulated independently ofthe melting rate.

4. The volume of gas passing through the furnace can be changed independently of the total heat input.

5. The process can be continuously varied in accordance with different requirements to provide a product of the desired analysis.

6. Air pollution resulting from the furnace use is substantially reduced, since the high flame temperature resulting from oxyfuel burner use, the reduction of nitrogen in the shaft, and the increase of shaft cross section above the melting zone all contribute to a reduced smoke and particle emission.

It is contemplated that the processes and apparatus of the present invention are not necessarily limited to metals of the types which in the prior art have been processed in shaft furnaces; but, that they will apply to all commonly processed scrap metals.

These and other objects, features, and advantages of the invention will be apparent to those skilled in the art by a detailed study of the drawings with reference to the specification hereinafter.

SHORT DESCRIPTION OF THE DRAWINGS FIG. l is a longitudinal sectional showing of a shaft furnace modified in accordance with the teachings of the present invention to include upper and lower rows of oxyfuel tuyere burners;

FIG. 2A is a section in the plane of the arrows 2A-2A of FIG. ll, showing the disposition of the oxyfuel burners at the lower level; and

FIG. 2B is a section in the plane of the arrows 2B-2B of FIG. 1, showing the disposition of the oxyfuel burners at the upper level.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS In FIG. 1 of the drawings, there is shown a shaft furnace for processing scrap of low density comprising, for example, borings, turnings, sheet bundles, tube mill scrap, bunchings, and sheet trimmings, of any well-known metals, such as, for example, iron, copper, etc.

The design of the furnace construction of the present embodiment, as shown in FIG. 1, will be seen to differ from the ordinary cupola known in the prior art in that the sidewalls taper outwardly above the coke bed, at an angle of about 15 with the principal vertical axis of the furnace, thereby preventing overheating of the sidewalls and permitting a larger volume of low density scrap to be loaded into the furnace. This angle may vary over the range to 30.

It will be further apparent from a study of FIGS. 2A and 2B, which will be described in detail hereinafter, that the angles of burner placement at the upper and lower levels are such as to contribute a swirling motion to the gas streams in the shaft. Moreover, as will be described hereinafter, both sets of tuyeres and the enclosed burners are designed to project inwardly, forming an angle of about 15 with the cross-sectional radius of the furnace, and at a downward angle of to in order to prevent the molten liquid from entering into the tuyeres.

Referring to FIG. 1, there is shown in longitudinal section a shaft furnace which rises to in excess of 30 feet above the ground, the stack extending to whatever height is necessary to carry the combustion products above the adjacent building structures. The furnace of the present embodiment is of circular cross section. Through the hearth section, the furnace has an outer diameter of 8-2/3 feet, not including an enclosing steel water jacket, 116 inches in outer diameter, which provides an annular clearance of four inches for water cooling. The furnace is supported on a number of metal support columns 1, each about a foot in diameter, which are mounted in a concrete base. The hearth section comprises a shell of boiler plate, about 1 inch thick, lined with fire bricks to a thickness of about 1-1/3 feet, and having an inner lining of carbon about 4 inches thick. This is built up to a height of about 4 feet above the cast iron base to form a well, the bottom of which is lined with sand in which is formed a channel for the molten iron and slag. A pair of metal doors 2, which are held shut by means of a metal door prop 3, support the contents of the furnace. The slag which floats on top of the molten iron is drawn off through the slagging spout 4a, whereas the molten iron is drawn off through tapping spout 4. The cupola well is completely lined with coke. At the lower end of the water jacket is a water-discharge spout 6. A second, slightly frustoconical section of the furnace comprising boiler plate having walls about inches thick, rises concentrically above the hearth portion to a height of 7 and 1% feet. The lower cross-sectional dimension of this section is seven feet, narrowing to 6 feet at the top of the section.

Entering the furnace in a plane about 4 feet above the base of the furnace, where the inner cross-sectional diameter is 84 inches, is a first array of tuyeres. In the present example these are six in number, being located symmetrically around the periphery of the furnace in the configuration indicated in FIG. 2A of the drawings. In the present example it will be seen that the tuyeres are not directed radially in the horizontal plane, as in most prior art configurations, but rather with their respective axes each making an angle of, for example, 15 in a clockwise direction with the radius of the circle. It will be apparent that each opposing pair of tuyeres in the present example is so directed that instead of being diametrically opposite, they are pointed along parallel lines which are spaced two feet apart. In addition to this, each of the tuyeres is directed downwardly from the horizontal plane at an angle of 10 to 15, as indicated hereinbefore.

In the present example, the double-walled tuyere pipes are of copper, 2 feet long, 8 inches in outer diameter, and 6 inches in inner diameter, comprising concentric shells spaced 1 inch apart and fused together at the inner ends to form a closed, annular water cooling compartment which is connected to the water cooling system. A portion of the tuyere projects along its centerllnc a distance of, say, 1 foot, into the furnace. To the outer end of the tuyere pipe 7 is riveted, welded, or screwed a tuyere-extension pipe 70, which is 22 inches long and 8 inches in diameter, which is sealed at the outer end by a flat annular closure. The tuyere extension pipe 7a is connected to a windpipe 13 through the 6-inch inner diameter downcomer pipe 13a, which extends upwardly and outwardly at an angle of about 60 with pipe 7a. The 21-inch diameter windpipe 13 surrounds the outer periphery of the furnace concentrically, at a distance about two feet above the top of the tuyere pipes 7 where the latter enter the furnace. Wind is supplied to the windpipe 13 through a conventional centrifugal-type blower 14 at a rate of, for example, between 200 and 4,000 standard cubic feet per minute. windpipe 13 and the six connected downcomer pipes 13a may be formed of steel.

Arranged concentrically within the tuyere 7 and tuyere extension pipe 7a is the oxyfuel burner 9. In the present example, this comprises a barrel about 3 inches in outer diameter, extending from just inside the outer Pat. of the tuyere 7, a distance of 18 inches outwardly and terminating in a burner body assembly which includes the oxyfuel burner fuel inlet 9a, the oxyfuel burner water inlet 10a and outlet 10b, and the oxyfuel burner oxygen inlet 11. The oxyfuel burner 9 may comprise one of the types well known in the art, such as, for example, types known as rocket burners, or self-atomizing tip-mix burners. Suitable types, for the purposes of the present invention, are specifically disclosed in the copending application Ser. No. 602,381 now Pat. No. 3,547,624 of B. G. Gray, filed Dec. 16, 1966. Alternative types of burners which may be adapted to the purposes of the present invention are disclosed, for example, in T. L. Shepherd U.S. Pat. No. 3,092,166 issued Jan. 4, 1963; or in W. B. Moen, et al. US. Pat. No. 3,135,626, issued June 2, 1964.

Moreover, the supply systems respectively connected to the fuel inlet 9a, the oxygen inlet 11, and the water inlet and

outlet

10a, 10b, are substantially similar to the systems described in detail in the patent of B. G. Gray, supra.

Entering the furnace at a plane substantially 6 feet above the center of the horizontal plane of the tuyere 7, where the inner cross-sectional dimension of the furnace is 72 inches, is an additional set of tuyeres 15 which are arranged in a configuration substantially as shown in FIG. 2B of the drawings. The plane at which the tuyeres 15 enter the furnace is approximately l- /z inches below the lower end of the bosh section of the furnace. The tuyeres 15 are substantially similar in material and construction to the tuyeres 7 described hereinbefore. The principal difference between the arrangements of the tuyeres l5 and that of the lower set of tuyeres 7 is that the two sets are arranged in offset relation, so that each of the tuyeres in the upper set protrudes into the furnace at a position which lies in a vertical plane approximately half way between the vertical planes of the nearest burners of the lower set of tuyeres. One of the burners of the upper group is mounted directly above the spout 4a; whereas the spout 4a lies between two burners of the lower group. The axis of each of the tuyeres 15 forms a counterclockwise angle in the horizontal plane of 15 with the radial direction; and, the tuyeres are inclined downwardly at angles which are uniform and between 10 and 15 with the horizontal. It will be noted that the angular disposition of the tuyeres at the two levels is different, being clockwise with reference to the radial direction at the lower level, and counterclockwise at the upper level. This is a particular feature of the invention which causes a swirling action of the gases injected into the furnace which aids the melting and superheating action. The high capacity oxyfuel burners 16 at the upper tuyere level are substantially similar to those described with reference to the lower set of burners, except that they are designed to accommodate volumes of oxygen and fuel roughly three times as great as those accommodated by the lower set of burners. The upper burners are likewise fed with oxygen and fuel through similar outlets, and from similar supply systems to those described with reference to the lower set of burners, and disclosed in detail in B. G. Gray application Ser. No. 602,381, now U.S. Pat. No: 3,547,624 supra.

The tuyeres are connected througli'the downcomcr pipes 1% to a Ill inch diameter wind pipe 19 which surrounds the furnace at the upper level about two feet above the top of the tuyeres 115, where theyenter the furnace. The dimensions and construction of tuyeres 115, downcomer pipes We and windpipe 19 are substantially the same as their counterparts at the lower tuyere level. Likewise, the centrifugal blower 20, which is connected to supply wind to the wind pipe W, is similar to blower 1d at the lower level.

It will be noted that whereas the present illustrative example shows the tuyere burner levels approximately 6 feet apart, this distance can be varied to suit individual metal requirements and furnace size or melt rate requirements.

The outwardly flaring bosh section 2ll is a particular feature of the furnace of the present invention. This comprises a double-walled water jacket Zia. Each of the walls comprises a steel plate about /4-inch thick. The interior is lined with refractory material, such as alumina, to a thickness of 4' inches. This section, which has an overall diameter of about 7 feet at its lower end, expands in cross section to about 1 1 feet at its upper end through a vertical rise of about 8 feet, flaring outwardly at an angle about 30 with the vertical. At the lower end of the bosh section is a water curtain distributor ring T3 for the lower section, which is fed by a pipe Elba. Pipes 22a and 22b, respectively, serve as inlet and outlet to the bosh section water jacket Ella. Water pipe 22c surrounds the upper end of the bosh section so that a water curtain is provided through external openings for both the bosh section and the tuyere section of the furnace.

The stack portion of the furnace is substantially 9 /2 feet in outer diameter, comprising a brick wall 6 inches thick which is encased in a steel shell la-inch thick. As pointed out previously, the shaft or stack portion, which serves to preheat the charge, rises to whatever height is necessary to carry the combustion products above the surrounding structures. At a height of, say, 10% feet above the lower end of the stack portion, is an opening 25, which is 72 inches wide and 100 inches high, which serves for charging into the furnace the low density scrap metal 23, together with the coke 26, to be processed.

in accordance with the present embodiment, coke comprising chunks having a median diameter of, say, 6 inches, first charged into the furnace to a level just below the level of the second ring of tuyeres l5. This coke bed serves two functions. The first is to provide a support medium for the charge above and hot areas of contact to transfer superheat to the descending droplets of molten metal which were melted in the zone adjacent the top burner row. The second function of the colte, particularly in the case of the iron cupola, is to provide a source of carbon to allow solutions of carbon to enter into the melted molten iron or steel droplets. Above the support bed is charged a layer of metal scrap material to be processed, comprising, for example, scrap steel, scrap iron, pig iron, and the like. At alternate planes in the furnace, which are usually 2 feet or more apart, are interposed layers of coke.

It will be apparent in accordance with the present invention that the scrap material moving down through the stack of the furnace comes in contact with the hot gases which are rising to the top of the furnace, thereby causing this material to become preheated. When the scrap metal charge has moved downwardly in the furnace through the bosh section to the upper level of the tuyeres l5, it absorbs a sufficient amount of heat, particularly from the latter set of tuyeres, to bring it up to the melting point. Accordingly, it leaves the level of the tuyeres 115 in the form of molten metal, trickling down over the layers of coke which fill the furnace up to that point. in the body portion of the furnace, the molten metal is superheated and purified by contact with hot gases rising from the lower set molten charge, depending on the ratio of oxygen to fuel in the burners.

it will be understood that in accordance with variations of the present invention, the burners can be removed from the lower plane of tuyeres, in which case the tuyeres serve merely as vehicles for bringing air in from the respective windpipe 13 or W, either hot or cold, at higher or lower velocities, depending on the requirements of thc specific material to be processed.

in accordance with another alternative, either the upper or lower set of burners may be operated without auxiliary air.

in accordance with a further alternative, instead of coke or graphite, refractory material such as, for example, lumps'of magnesia, lime, calcium carbide or alumina, may be used to fill the lower portion of the furnace approximately up to the level of the tuyeres 15 so that certain undesirable components, such as, for example, sulfur and phosphorus, which are present in the coke, do not come in contact with the charge. Such an arrangement is particularly beneficial when the charge comprises a major portion of copper.

in addition, another example of the use of the charge support medium for desulfurization or dephosphorization is evident in the case in which steel scrap is melted over a sup port bed of limestone, which has been previously calcined in situ to provide a support bed of calcium oxide. Molten steel droplets passing over the bed are superheated and desulfurized by the rapid movement over the hot calcium oxide when heated with reducing gases from the lower tuyere burners.

Under these conditions, the following reaction occurs:

2Ca O+S-+2CaS+O 1 The calcium sulfide is absorbed in the slag. Assuming that the burners have been adjusted to create a reducing atmosphere, the oxygen is removed as carbon dioxide and water vapor.

Assuming that the burners and tuyeres are adjusted to produce an oxidizing environment instead of a reducing environment in the furnace containing the calcium oxide support bed, dephosphorization will occur in accordance with the fol lowing reaction:

4l-l-5Ct; 2P O (2) 2P O +4CaO+Of lCal O (3) The calcium phosphate becomes a component of the slag.

Furthermore, special support media such as lump calcium carbide can be used to effect simultaneous desulfurization and carburization. Makeup support media material can be added with the charge to replace material which has become slagged or eroded away.

A unique feature of the present invention is that the two levels of oxyfuel burners may be operated in conjunction with separate Wind supplies to provide separate functions. The uppermost row of burners, used with or without air, functions as previously described to provide heat for preheating the charge to the melting point and for supplying a substantial portion of the latent heat of fusion. The function of the lower row of burners, which also may be used with or without air, is to supply the heat required for superheating the material to the proper spout temperature.

A number of metals and their melting requirements is shown in the table below for reference purposes.

TABLE l British Thermal Units Requirements PerTon of Metal Millions Su erheat to Pour 1n the prior art, a conventional water cooled cupola requires that approximately 3.5 million B.t.u., be expended to melt one ton of cast iron. This figure is slightly improved in a refractory lined cupola which normally requires only 2.7 million B.t.u. per ton of iron. Since case iron theoretically requires only 1.165 million B.t.u. per hour, the efficiencies of these prior art systems are only 33.3 percent and 43.2 percent, respectively.

1t is estimated that efficiencies of operation of the shaft furnace of the present invention approximate 75 percent. Moreover, it is estimated that the lower burners contribute about one-third of the latent heat of fusion, plus the superheat; while the upper burners provide two-thirds of the latent heat requirements, plus all of the preheat requirements.

In accordance with a specific example of operation of the present invention, to melt cast iron using a coke charge of about 5 percent of the metal charge and a melting rate of 40 tons per hour, the required firing rate per hour at each of the burner rows is as follows:

Upper Row ofTuyere Burners 40 tons X .830 40 tons x .083 X 55 33.20 Million B.t.u.

2.21 Million B.t.u.

Preheat Fusion 40 tons X .083 X ls Superheat 40 tons X .252 10.10 Million B.t.u.

Total 11.21 Million B.t.u.

= 15.00 Million B.t.u.

Per Hour Actual Firing Rate ll.2l/.75

To supply the British Thermal Units for the upper burners, it is estimated that a fuel oil having a heating value of 145,000 B.t.u. per gallon is added at the rate of 326.5 gallons per hour. Pure oxygen is added to provide 60 percent of the stoichiometric requirement of oxygen for combustion. This amounts to 326.5X280XO.60=54,700 standard cubic feet per hour. The additional oxygen required is 326.5X280X0.40 =36,600 standard cubic feet per hour. This is supplied by blast air in the amount of 2,930 standard cubic feet per minute.

The lower burner fuel requirement is 103.3 gallons per hour. Pure oxygen to provide 60 percent of the stoichiometric requirement amounts to 103.3X280X0.60=17,400 standard cubic feet per hour. Additional oxygen is l03.3X280X0.40= 11,600 standard cubic feet per hour. This is supplied by blast air in the amount of 925 standard cubic feet per minute.

The total separated oxygen required at both levels of burners is 54,700 standard cubic feet per hour plus 17,400 standard cubic feet per hour or 72,100 standard cubic feet per hour or an equivalent of 1,800 standard cubic feet per ton of iron melted.

In accordance with another example, the furnace of the present invention is used for the melting of copper mill scrap. 1n this case, coke would not be used and the charge support material preferably comprises large lumps of alumina refractory or in some cases, graphite. It is estimated that the efficiency is higher than the iron case, approximately 85 percent. The British Thermal Units requirements are as follows to melt at the rate of 30 tons per hour:

Up er Row of'l'uycrc Burnerl 30 tons X .394 30 tons X .1112 X 51! 11.81 Million B.t.u. 3.65 Million B.t.u.

Preheat Fusion Total 15.46 Million B.t.u.

= 18.20 Million B.t.u.

Per Hour Actual Firing Rate 15.46/

Lower Row ol'l'uyere Burners 1.82 Million B.t.u. 1.98 Million B.t.u.

30 tons X .182 X M 30 tons X .066

Fusion Superheat Total 3.80 Million B.t.u.

= 4.48 Million B.t.u.

Per Hour Actual Firing Rate 3.8!.85

This assumes the natural gas employed has 1,000 B.t.u. per cubic feet; and, that percent stoichiometric oxygen equals two volumes 0; per one volume gas.

From the above it will be apparent that the consumption of separated oxygen amounts to 758 cubic feet per ton of copper.

It will be noted that a particular feature of the furnace construction in accordance with the present invention, is that it differs from the ordinary prior art cupola in that the sidewalls taper outward above the coke bed, thereby preventing their overheating, and permitting more low density scrap to be loaded into the furnace.

Another feature of the invention is the swirling motion impressed on the gas streams in the shaft by the particular angles at which the burners are disposed in accordance with the present invention, being rotated in a clockwise direction from the radius at one tuyere level and level counterclockwise direction at the other tuyere level, combined with an inclination through an angle of 10 to 15 in each case.

It will be apparent to those skilled in the art that the present invention is not confined to the particular examples described herein by way of illustrative example; but, that the invention is defined in the scope of the appended claims.

We claim:

1. In a shaft-type furnace for melting charge comprising scrap metal which comprises in combination a hearth portion including a spout, a body portion extending to a substantial height above said hearth portion, a bosh portion flaring out wardly to a substantial height above said body portion and terminating at its upper end in an upwardly extending stack,

a plurality of tuyeres located at a first level at the bottom of said body portion just above said hearth portion,

a plurality of tuyeres located at a second level near the top of said body portion just below said bosh portion, windpipe means for directing blast air to said first and second level tuyeres,

oxyfuel burners disposed in at least some of the second level tuyeres, the nozzle of each said burner being located within its respective tuyere,

means supplying fuel and substantially pure oxygen to fire said oxyfuel burners,

an opening in said stack for loading charge including said scrap metal into said stack,

a supporting media for said scrap metal disposed in said hearth and in said body portion, said media being porous to allow the melted charge to pass therethrough, said second level of tuyeres being located above said support ing media,

the tuyeres at said second level being directed and arranged to impart to the gases passing into said furnace at said second level a swirling motion in a given direction about the axis of said furnace, the tuyeres at said first level being constructed and arranged to impart to the gases passing into said furnace at the first level a swirling motion in an opposite direction,

said tuyeres being substantially equally spaced around a periphery of said furnace at said first level and at said second level, wherein the position of each of said tuyeres in said second level lies substantially intermediate the position of the adjacent tuyeres in said first level and wherein at one of said levels each of said tuyeres is directed so that the principal axis thereof forms an angle of approximately l in a clockwise direction with the radius of said furnace, and wherein at the other said level each of said tuyeres is directed so that the axis thereof forms an angle of approximately 15 in a counterclockwise direction with the radius of said furnace,

whereby said charge is preheated in said staclt, is melted in the area of said second level of tuyeres dripping down through the supporting media, and is superheated in the area of said first level of tuyeres to a desired spout temperature.

2. The combination in accordance with claim i wherein tuyeres at each of said levels contain oxyfuel burners.

3. The combination in accordance with claim it wherein said supporting media comprises coke.

d. The combination in accordance with claim ll wherein said supporting media comprises refractory material.

5. The combination in accordance with claim l wherein said supporting media comprises material selected from the group consisting of aluminum oxide, magnesium oxide, calcium oxide and calcium carbide, or combinations thereof.

ti. The combination in accordance with claim t wherein the sides of said bosh portion flare outwardly from the direction of the principal vertical axis of said furnace at an angle within the rang of up to 30 7. The combination in accordance with claim It wherein each of said tuyeres is inclined downwardly at an angle of from 10 to with the horizontal.

8. The combination in accordance with claim "i wherein said oxyfuel burner are substantially coaxially disposed in each of said tuyeres, wherein each of said tuyeres is disposed to protrude a substantial distance into said furnace, and wherein each of said burners is withdrawn into its respective tuyeres a substantial distance from the inner face of said furnace.

9. A shaft-type furnace for melting charge comprising metal which comprises in combination a hearth portion including a lltll spout, a body portion extending to a substantial height above said hearth portion, a bosh portion above said body portion and terminating at its upper end in an upwardly extending stack,

a plurality of oxyfuel burners located at a first level in the bottom of said body portion just above said hearth portion,

a plurality of oxyfuel burners located at a second level near the top of said body portion just below said bosh portion,

a source of substantially pure oxygen and a source of carbonaceous fuel,

each of said burners respectively connected to said sources of oxygen and carbonaceous fuel for firing said burners, the was of each of said burners making an angle with a radius of the furnace so as to impart a swirling motion to the gates passing into the furnace,

an opening in said stack for loading charge including said metal into said stack,

a supporting media for said metal disposed in said hearth and in said body portion, said media being porous to allow the melted charge to pass therethrough, said second level of burners being located above said supporting media,

said burners being substantially equally spaced around the periphery of said furnace at saidl first level and at said second level, wherein the position of each of said burners in said second level lies substantially intermediate the positions of the adjacent burners in said first level and wherein at one of said levels each of said burners is directed so that the principal axis thereof forms an angle of approximately 15 in a clockwise direction with the radius of said furnace and wherein at the other said level each of said burners is directed so that the principal axis thereof forms an angle of approximately 15 in a counterclockwise direction with the radius of said furnace,

whereby said charge is preheated in said stack is melted in the area of said second level of burners dripping down over the material of said supporting media, and is superheated in the area of said first level of burners to a desired spout temperature.

it). The combination in accordance with claim 9 wherein said supporting media comprises a major portion of one of the alternative types of carbon including coke and graphite.

ill. The combination in accordance with claim 9 wherein said supporting media comprises a major portion of refractory material.

112. The combination in accordance with claim 9 wherein said metal is scrap and comprises primarily steel and wherein said supporting media comprises a substantial portion of calcium oxide.

13. The combination in accordance with claim 9 wherein said metal is scrap material and comprises primarily steel and said supporting media comprises a substantial portion of lump calcium carbide M. The combination is accordance with claim 9 wherein the sides of said bosh portion flare outwardly at an angle within the rang of up to 30 relative to the principal vertical axis of said furnace.

115. The combination in accordance with claim 9 wherein each of said burners is inclined downwardly at an angle of from 10 to 15 to the horizontal.

Column Column Column Column Column Column Patent No.

Inventor(s) It is certified that error appears in the aboveidentified patent and that said Letters Patent are hereby corrected as shown below:

Column 2, line Column 10, line 16, "gates" should read --gases--.

Signed and sealed this 11th day of April 1972.

(SEAL) Attest:

UNITED STATES PATENT OFFICE CERTIFICATE OF

CORRECTION

3, 3,57 Dated September 7, 1971 L. J. Geiger and J. W. Estes 5, the hyphen is missing after "circular" 57, the hyphen is missing between "cross section".

36, the hyphen is missing between "cross section". 26, 3

line

the second figure in last column should read 1380 "case" should read --cast--.

line

23, after "percent" insert --of the stoichiometric and delete "B.t.u." line 2 L, after "50" insert and delete "equals". line 56, "level" (second occurrence) should be deleted and insert --a--.

line 51, line 56, line 59, line 61,

line 57, "rang" should read --range-.

EDWARD M.FLETCHER,JR. Attesting Officer ORM PO-1050 110-69) ROBERT GOT'I'SCHALK Commissioner of Patents USCOMM-DC GOB'IO-PBQ w u s. sovenumzm rnnmue crnc: 19" 0-305-334

Claims

1. In a shaft-type furnace for melting charge comprising scrap metal which comprises in combination a hearth portion including a spout, a body portion extending to a substantial height above said hearth portion, a bosh portion flaring outwardly to a substantial height above said body portion and terminating at its upper end in an upwardly extending stack, a plurality of tuyeres located at a first level at the bottom of said body portion just above said hearth portion, a plurality of tuyeres located at a second level near the top of said body portion just below said bosh portion, windpipe means for directing blast air to said first and second level tuyeres, oxyfuel burners disposed in at least some of the second level tuyeres, the nozzle of each said burner being located within its respective tuyere, means supplying fuel and substantially pure oxygen to fire said oxyfuel burners, an opening in said stack for loading charge including said scrap metal into said stack, a supporting media for said scrap metal disposed in said hearth and in said body portion, said media being porous to allow the melted charge to pass therethrough, said second level of tuyeres being located above said supporting media, the tuyeres at said second level being directed and arranged to impart to the gases passing into said furnace at said second level a swirling motion in a given direction about the axis of said furnace, the tuyeres at said first level being constructed and arranged to impart to the gases passing into said furnace at the first level a swirling motion in an opposite direction, said tuyeres being substantially equally spaced around a periphery of said furnace at said first level and at said second level, wherein the position of each of said tuyeres in said second level lies substantially intermediate the position of the adjacent tuyeres in said first level and wherein at one of said levels each of said tuyeres is directed so that the principal axis thereof forms an angle of approximately 15* in a clockwise direction with the radius of said furnace, and wherein at the other said level each of said tuyeres is directed so that the axis thereof forms an angle of approximately 15* in a counterclockwise direction with the radius of said furnace, whereby said charge is preheated in said stack, is melted in the area of said second level of tuyeres dripping down through the supporting media, and is superheated in the area of said first level of tuyeres to a desired spout temperature.

2. The combination in accordance with claim 1 wherein tuyeres at each of said levels contain oxyfuel burners.

3. The combination in accordance with claim 1 wherein said supporting media comprises coke.

4. The combination in accordance with claim 1 wherein said supporting media comprises refractory material.

5. The combination in accordance with claim 4 wherein said supporting media comprises material selected from the group consisting of aluminum oxide, magnesium oxide, calcium oxide and calcium carbide, or combinations thereof.

6. The combination in accordance with claim 1 wherein the sides of said bosh portion flare outwardly from the direction of the principal vertical axis of said furnace at an angle within the rang of up to 30 *.

7. The combination in accordance with claim 1 wherein each of said tuyeres is inclined downwardly at an angle of from 10* to 15* with the horizontal.

8. The combination in accordance with claim 7 wherein said oxyfuel burner are substantially coaxially disposed in each of said tuyeres, wherein each of said tuyeres is disposed to protrude a substantial distance into said furnace, and wherein each of said burners is withdrawn into its respective tuyeres a substantial distance from the inner face of said furnace.

9. A shaft-type furnace for melting charge comprising metal which comprises in combination a hearth portion including a spout, a body portion extending to a substantial height above said hearth portion, a bosh portion above said body portion and terminating at its upper end in an upwardly extending stack, a plurality of oxyfuel burners located at a first level in the bottom of said body portion just above said hearth portion, a plurality of oxyfuel burners located at a second level near the top of said body portion just below said bosh portion, a source of substantially pure oxygen and a source of carbonaceous fuel, each of said burners respectively connected to said sources of oxygen and carbonaceous fuel for firing said burners, the axis of each of said burners making an angle with a radius of the furnace so as to impart a swirling motion to the gates passing into the furnace, an opening in said stack for loading charge including said metal into said stack, a supporting media for said metal disposed in said hearth and in said body portion, said media being porous to allow the melted charge to pass therethrough, said secOnd level of burners being located above said supporting media, said burners being substantially equally spaced around the periphery of said furnace at said first level and at said second level, wherein the position of each of said burners in said second level lies substantially intermediate the positions of the adjacent burners in said first level and wherein at one of said levels each of said burners is directed so that the principal axis thereof forms an angle of approximately 15* in a clockwise direction with the radius of said furnace and wherein at the other said level each of said burners is directed so that the principal axis thereof forms an angle of approximately 15* in a counterclockwise direction with the radius of said furnace, whereby said charge is preheated in said stack is melted in the area of said second level of burners dripping down over the material of said supporting media, and is superheated in the area of said first level of burners to a desired spout temperature.

10. The combination in accordance with claim 9 wherein said supporting media comprises a major portion of one of the alternative types of carbon including coke and graphite.

11. The combination in accordance with claim 9 wherein said supporting media comprises a major portion of refractory material.

12. The combination in accordance with claim 9 wherein said metal is scrap and comprises primarily steel and wherein said supporting media comprises a substantial portion of calcium oxide.

13. The combination in accordance with claim 9 wherein said metal is scrap material and comprises primarily steel and said supporting media comprises a substantial portion of lump calcium carbide

14. The combination is accordance with claim 9 wherein the sides of said bosh portion flare outwardly at an angle within the rang of up to 30* relative to the principal vertical axis of said furnace.

15. The combination in accordance with claim 9 wherein each of said burners is inclined downwardly at an angle of from 10* to 15* to the horizontal.