US3715203A

US3715203A - Melting of metals

Info

Publication number: US3715203A
Application number: US00100758A
Authority: US
Inventors: Bie E De
Original assignee: Societe Generale Metallurgique de Hoboken SA
Current assignee: Societe Generale Metallurgique de Hoboken SA
Priority date: 1969-12-24
Filing date: 1970-12-22
Publication date: 1973-02-06
Anticipated expiration: 1990-02-06
Also published as: LU60094A1; DE2062144C3; CA922902A; FR2074168A5; ZA708461B; FI54930B; GB1327490A; FI54930C; BE760452A; DE2062144A1; DE2062144B2; JPS5426489B1

Abstract

The invention relates to a process for melting and refining copper in a vertical furnace by direct contact of copper pieces with hot gases produced by combustion of a non-solid fuel with an oxygen-containing gas ignited before coming into contact with the copper pieces, the said gas being substantially neutral, the variation around the neutral point being such that the oxygen contents shall be lower than about 0.5 percent of O2 and the hydrogen contents shall be lower than about 0.5 percent of hydrogen, and the pressure being such that the ignited has leaving the burners shall be capable of piercing the liquid mass situated at the level of the burners.

Description

United States Patent De Bie [451 Feb. 6, 1973 MELTING OF METALS Primary ExaminerDewayne Rutledge [75] Inventor: Edouard De Bie, Antwerp, Belgiuin. Asmmm Legru Hm Attorney-Fred C. Phllpitt [73] Assignee: Metallurgie Hoboken-overpelt, Brus- Belglum 57 ABSTRACT Fl d: D .2 [22] 16 cc 2 1970 The invention relates to a process for melting and [211 Appl. No.: 100,758 refining copper in a vertical furnace by direct contact of copper pieces with hot gases produced by com- [30] Foreign Application Priority Data bustion of a non-solid fuel with an oxygen-containing gas ignited before coming mto contact with the copper Dec. 24, Luxembourg pieces the Said gas being ubstantially neutral the variation around the neutral point being such that the [52] US. Cl. ..75/76, 75/65, 75/72 Oxygen contents Shall be lower than about 5 percent [51 lnLCl. ..C22b 15/00, C22b 15/14 of O2 and the hydrogen contents shall be lower than [58 Field of Search ..75/7276 about 05' percent of hydrogen, and the pressure being such that the ignited has leaving the burners shall be [561 References cued capable .of piercing the liquid mass situated at the UNITED STATES PATENTS level Ofthe bumam 3,199,977 8/1965 Phillips ..75/76 1968mm; 'giDrawuiii'iFi'gwiis PATENTEUFE 5 ma SHEET 3 OF 4 sum u or 4 PATENTEU FEB 6 I973 MELTING F METALS This invention relates to a-process and to an apparatus for melting copper with hot gases resulting from the combustion of any liquid or gaseous fuel with any sulphur content, in a vertical furnace, the liquid metal thus melted in the said furnace being admitted in one or several holding furnaces in which the usual refining operations for casting copper in the form of anodes used in electrolytic refining take place.

More particularly, the present invention relates to the melting of impure copper or blister copper with said gases in a vertical furnace, which makes use of the advantage of heat transfer by convection instead of a transfer by radiation such as occurring in reverberatory furnaces.

The present invention also relates to the new industrial product, i.e., a copper anode obtained by this process.

Heretofore there have been many attempts to melt impure copper in a vertical furnace which was fired with a liquid or gaseous fuel. These prior attempts, however, failed because of the difficulty to discharge the slags resulting either from the impurities in the blister copper and in the impure copper, or from the reaction products of these impurities with the refractory lining of the furnace, Hence, it has never been possible to melt in a economical way blister copper and impure copper scrap in a vertical furnace which is fired with a liquid fuel or a gaseous fuel.

Up to now, melting such copper was primarily done either in electrical furnaces, or more generally in conventional reverberatory furnaces employing radiant heat coming from burners using fuel with a low content of sulphur, which element is deleterious for copper.

The present invention is particularly useful for melting impure copper and for casting anodes.

Those skilled in the art know that copper electrodes are produced industrially in an electrolytic refining process by employing relatively impure copper as anodes, a suitable electrolyte, and copper sheets, called starting sheets," as starting cathodes.

During the electrolysis, copper dissolves from the anodes into the electrolyte from which it is deposited as pure copper on the starting sheets to form the copper cathodes.

In practice, anodes and cathodes of the same general size and shape are employed. Anodes are generally of rectangular or square shape.

The present invention relates to a process for melting and refining copper in a vertical furnace, equipped at its upper part with a charging device to feed the pieces to be melted, and at its lower part adjacent the bottom of the furnace, with an opening to discharge the liquid material to a holding furnace, the melting of the said pieces in the vertical furnace being carried out by direct contact of the copper pieces with a stream of hot gases originating from the combustion of a liquid or gaseous fuel with an oxygen-containing gas injected through burners which are mounted along the perimeter of the furnace, the melting and refining process being characterized in that the said gas resulting from the combustion and ignited before coming into contact with the impure copperpieces, is a substantially neutral gas, the variation around the neutral point being such that the oxygen contents shall be lower than about 0.5

percent to 0 and the hydrogen contents shall be lower than about 0.5 percent of hydrogen, and the pressure being such that the ignited gas leaving the burners shall be capable of piercing the liquid mass situated at the level of the burners.

The pressure of the combustion gas which is injected is preferably comprised between and 380 grlcm and still more preferably is of about gr/cm.

According to the present invention a vertical furnace is employed for melting copper, which furnace is equipped at its upper portion with a device for chargiifi the copper pieces to be melted and at its lower portion, adjacent the bottom the furnace, has an opening for discharging the liquid material, the melting of the said copper pieces in the vertical furnace being carried out by direct contact of the said pieces with a stream of hot gases originating from the combustion of a liquid or gaseous fuel with an oxygen-containing gas injected through burners arranged on the perimeter of the furnace, the combustion gas which is ignited before coming into contact with the impure copper pieces being substantially neutral, the oxygen contents being of about 0.5 percent and the hydrogen contents being lower than about 0.5 percent and under a pressure higher than the ambient atmospheric pressure, the said pressure being at least at a level permitting that the combustion gases shall pierce the barriers of liquid metal.

Still according to the present invention, the heat input rate from this combustion gas, is at least equal to 300 Kcal/kg, together with a pressure at least equal to 40 inches of water column, so that a fast surface melting of the copper pieces is obtained and that direct discharging of the thus molten mass is forced under pressure, a formation of a great amount of slag being avoided due to thefast surface melting of the copper pieces at the level of the burners and owing to the discharging under high pressure of the molten mass.

Gas pressure in the furnace at the level of the burners and of the discharge opening (tap hole) is such that the flow of metal leaving the furnace is a jet under pressure, driving out of the furnace liquid material comprising liquid slag and solid matter. in order to obtain such a jet under pressure, it is necessary to provide, in addition to the sufficient pressure of the combustion gas at the level of the burners a sufficient stacking height of the copper pieces, so as to obtain a sufficient resistance to the passage of the combustion gases and to provide the required pressure at the level of the burners and of the tap hole. A stacking height of the copper pieces of at least 6 meters has been found to be advantageous.

Still according to the present invention, the molten copper and the slags originating from the impurities in the copper discharged through the tap hole of the vertical furnace, are conveyed to one or more reverberatory furnaces or to one or more tilting furnaces or even to several furnaces arranged one after the other in which the molten copper can be subjected to the other, to remove the impurities, which are nevertheless collected in the form of slags which are then removed, followed by poling in order to regulate the oxygen content and to give to the copper the required quality before employing the reverberatory furnace or furnaces or the tilting furnace or furnaces for casting anodes of the required quality.

An important advantage of the present invention is that impure copper pieces can be melted in a vertical furnace which is fired with a liquid or a gaseous fuel in which any sulphur content is allowable, at a higher speed than by conventional melting processes in a reverberatory furnace. With the present process, sulphur which might be contained in the liquid or gaseous fuel, and, if present, Zn, As, Sn, Pb are evacuated with the fumes resulting from the combustion gases and which leave the furnace at its top part. This fuel can be either a gaseous hydrocarbon such as butane, propane or a natural gas or a liquid hydrocarbon such as heavy fuel. In employing a reverberatory furnace as holding furnace after the above mentioned vertical furnace, for instance 300 tons of impure copper can be melted, refined and cast in less than 18 hours, whereas the conventional process generally lasts more than 24 hours.

For instance, with a unit consisting of a vertical furnace followed by a reverberatory furnace which can contain more than 300 tons of copper and in which refining, poling and casting has been possible, the following cycle was obtained duration of melting 5 hours 30 minutes refining 4 hours poling 2 hours casting 6 hours 30 minutes complete cycle 18 hours,

whilst in the conventional way this cycl e is generally as follows:

melting duration 9 hours refining 7 hours poling 2 hours casting 6 hours 30 minutes complete cycle 24 hours 30 minutes.

The duration of the cycle can thus be reduced by saving time in the melting point and also in the refining period since, as it will be explained hereafter, the formation of slags resulting from the impurities of the copper can be reduced to a minimum, and their removal is facilitated.

Another important advantage is that the practice of the present invention enables impure copper to be melted in such a way that an amount of molten copper is produced which is sufficient to feed several reverberatory furnaces by means of only one vertical furnace, .which allows of speeding up still more the production of anodes, owing to the possibility of casting without interruption thanks to the possibility of successive feeding of a rapid casting machine by means of several holding furnaces.

The present invention may be carried out to provide a desired way of surface solidification of the copper. The process which is generally applied is either casting in conventional closed bottom moulds, or any other plate casting process which produces such anodes.

Another important advantage of the present inven- "tion is that copper can be molten in a vertical furnace heated with a liquid or gaseous fuel in which any sulphur content is allowable, without producing great quantities of slags. Owing to the rapid surface melting and to the direct discharging under pressure of the molten mass, the formation of slags can indeed be reduced to a minimum, by the use of a combustion gas of sub stantially neutral composition. Impurities resulting from coke, which in the melting in a vertical furnace increase the quantity of slags, are also avoided.

Another advantage is reduction of the consumption of refractories to a level which is lower than with prior processes of anode production since the anode refining and casting furnace will be fed mainly with liquid metal and will not be subjected to melting operations any more, its life will be considerably prolonged. Reduced consumption of refractory bricks also has a favorable influence on the quantity of slag produced.

Another advantage of the invention is that a desired flow of molten copper can be obtained within minutes of starting the vertical furnace and the flow of copper can likewise be stopped in a matter of minutes so that molten copper can be supplied as needed.

Still another advantage is that by regulating the combustion to provide a substantially neutral atmosphere, many impurities of copper such as zinc, lead, tin, and other impurities are volatilized and can be recovered separately in a dust collector mounted on the flue of the furnace, which, moreover, helps considerably in reducing the quantity of slag formed and collected in the refining furnace, thus leading to a greater facility of refining and to a considerable reduction of the cost of re-treating the metals drawn with the slag.

Another advantage is that capital investment and operating costs of copper anode production can be substantially reduced by comparison with conventional processes.

The stream of combustible gas is ignited and substantially burned adjacent the exit of the burners and in the ports situated at the outer end of the latter, before its contact with the above mentioned copper pieces. The gas current is discharged under such a pressure that it can pierce barriers or liquid metal and pass through the liquid metal. It has a heating value which is sufficient to melt the copper and the slag resulting from the impurities contained in the impure copper. The material thus molten is conveyed under pressure to a holding furnace in order to remove the slag which will float on the surface of the bath, and to refine and cast the copper in the form of anodes. Satisfactory results are obtained by fixing the oxygen contents of the gas stream approximately between 0 and 0.5 percent. It has been found that the total heat input rate from the combustion gas which is injected in the said furnace should be at least equal to 300 Kcal/kg of copper and not higher than 900 Kcal/kg of copper and that the heat input rate should be at least equal to 1,200,000 Kcal/per burner, for a furnace of a capacity of about 300 tons.

The gaseous stream may be slightly oxidizing, the contents of oxygen being of about 0.5 percent'if the charge does not contain an amount of iron sufficient to form magnetite. If such an amount of iron were present, silica may be added and then the combustion gas used may be slightly oxidizing (about 0.5% 0

The vertical melting furnace designed for-melting impure copper comprises a charging device for the copper to be molten, which is located at the upper portion of the furnace, a device adjacent the lower portion to discharge the molten copper and a set of burners mounted in the wall of the furnace, arranged in one or more rows one above the other all along the walls, the lowest row being mounted as near as possible to the bottom of .the furnace which is generally formed by a hearth inclined towards the exit opening (tap hole) and in sucha way that the plane of the exit centers of the parts of the burners, which is inclined in the same direction as the hearth, shall be located above the tap hole. The slope of the hearth is determined in such a way that it is adapted to the natural flow slope of the molten mass. As regards the lowest rows of burners, the plane of the'centers of the ports of the burners is inclined on the horizontal line in the same way as the hearth, whereas for the upper rows this plane is horizontal. Each row consists of the greatest possible number of burners which is compatible with the space required for the latter and one or two burners are located above the exit openings (tap hole) and directed towards the hearth in such a way that a converging stream of hot gases strikes the hearth inside the tap hole.

The pressure inside the furnace forces a discharging of the liquid materials containing slag and even pieces of solid material, through the tap hole and prevents plugging of the said hole. Consequently, the metal jet leaving the melting furnace shall be under such a pressure that the contents of the furnace are violently driven out through the tap hole. As regards the stream of combustion gas, it has been found that the pressure, which would make the burners of the lower row function as imme-rged tuyeres when they are in contact with liquid copper, should be at least equal to 180 g/cm (70 inches of water column) and may be as high as 380 g/cm (150 inches of water column). A good functioning of the furnace requires a pressure in the furnace at the level of the burners and of the tap hole of at least 65 gr/cm (25 inches of water column).

A burner may be used for the furnace, comprising means for effecting the mixture of fuel and oxygen-containing gas, the said burners having a tube closed at its ends by two plates, the said two plates being interconnected inside the said tube by a series of conduits serving for the passage of air, the plate corresponding to that side where the air leaves, being provided with a series of small orifices for the escape of gases introduced into the said tube, the said gas orifices being inclined relative to the said air conduits to project the leaving gas above the outlets of the air conduits, the number of gas conduits being sufficient to feed each air conduit, and means being provided for mixing the air and gas at the outlet of each air conduit.

The conduits provided for the passage of air may be inclined relatively to the non-inclined orifices for the passage of the gas.

In the drawings FIG. 1 shows the lay-out of the hearth and of the lower row of burners, and the water-cooling systems of It has been found that for obtaining good melting results, several rows of burners should be employed and that the exit holes of the burners of the lower row should be arranged as near as possible to the bottom of the furnace, which is generally formed by a hearth inclined towards the tap hole. 1

The distance between the lower edge of the opening for the passage of the burner and the hearth is advantageously comprised between 3 and 10 cm and preferably is equal to about 7 cm.

The slope of the hearth is adapted to the natural flow slope of the molten mass such a slope may be of between 6 and 18, and yields the best results with an angle of 12.

The planes of the centers of the exit holes of the burner ports of the two lowermost rows should also be inclined in the same way as the hearth, i.e., towards the tap hole.

FIG. 1 enables better to understand the relation between these various planes and that of the hearth. In FIG. 1 the reference number 1 represents the hearth of the vertical furnace, 2 the tap hole, 3 and 3a the burners, 4 the walls of the furnace, 4a the cooling jackets, 10 the outside walls of the furnace, 5 the centers of the exit holes of the burner ports through which the combustion gases under pressure escape; at 6 a line has been drawn connecting the centers 5 of the exit holes of the burner ports and representing the plane 6 containing these centers. It will be noted that the plane 6 is inclined in the same way as the hearth l and that it is located above the upper wall 7 of the tap hole 2. A slope of the hearth of 12 which corresponds in most cases to the natural flow slope of the molten mass requires a smaller slope of the plane 6, which comprises the centers of the exit holes of the ports of the burners of the lowerrows, for instance 8; the ratio of the two inclinations on the horizontal line is about 8/12 0.66. It has been found that a good functioning of the furnace is ensured when the said ratio is kept between 1 and 0.50.

Generally, the furnace is equipped with four rows of burners, the two lower rows having their plane of centers of the exit holes of the burner ports inclined on the horizontal line, as explained above, the two upper rows being horizontal.

In order to cover the whole section of the furnace, each burner ofeach row must be inclined downwards so that heat can be distributed all over the section. It has been found that the slope on the horizontal line of the burners should be at least equal to the slope of the hearth; a steeper slope on the horizontal line than the slope of the hearth yields better results; The best results are obtained when the relation between the slope of the burners on the horizontal line and the slope of the hearth is chosen between I and L40.

In order to keep the hole for discharging the liquid material constantly open and free from solid matter and mentions, one or two burners (3a) are mounted above the said hole and directed towards the hearth in such a way that a converging stream of very hot gases strikes the hearth inside the tap hole (see FIG. 1

In order to keep the hole clear and to facilitate the discharge of materials, it is recommended to provide a hole of a width which is large in comparison with its height. The best results are obtained with a square hole or with a rectangular hole, the large base of which is parallel to the hearth.

FIG. 2 shows one way of carrying the vertical furnace into effect.

The parts which have already been described in connection with FIG. 1 are met again 1 shows the hearth of the furnace, 2 the tap hole, 3 the burners arranged in the plane 6 passing through the centers of the exist holes of the port 3 is a burner arranged in the tap hole 2.

At 4 the lower part has been shown, which has a conical form tapering towards the bottom of the furnace and is connected to the upper part 8 which has an upward conical form, by means of a cylindrical zone 9. The walls of the furnace, as they are shown at 4, 9 and 8, are made of refractory bricks, preferably of silicon carbide. The outer surface of the furnace in the region of the burners may be formed of water-cooled sleeves into which the refractory bricks holding the burners are introduced, so as to reduce the wear of the refractories.

The tap hole may also be a water-jacketted member into which the refractory bricks holding the burners are introduced. Four rows of burners have been shown, the upper row being located in the cylindrical zone 9. At 10 the outside lining is shown. The charging devices of the furnace and the fumes collecting devices, located above the upper zone 11, are omitted. In order to avoid obstructions when charging, the upper part of the furnace has an upward conical form.

The melting of impure copper blocks of various sizes, some of them oflarge size, requires a certain number of precautions. In a furnace for melting such charges, the column of material must be sufficiently high to ensure a sufficient heat exchange over its total height and to obtain a sufficient resistance to the passage of the said combustion gases so that the required pressure can be present at the level of the burners and of the tap hole.

Owing to the voids between the blocks forming the said column, the height of the column should be such that the combustion gases shall have the required pressure at the tap hole and at the level of the burners. For a furnace with 4 rows of burners this height should be higher than 8 m in any case it must be higher than approximately 6 m.

The temperature of the stream of very hot gases, when the latter arrives above the said column, can thus be kept between 300 and 500 C, provided that no volatile or combustible elements originating from the molten material will burn above the said column.

FIG. 3 shows a gas burner which is particularly suitable for melting a copper column, such as above described. At 12 a mixing chamber has been shown, which will be described in detail in FIG. 4 the lower plate of the chamber 12 is shown at 13 and the upper plate of the same chamber, which is perforated with holes 15, is shown at 14. The

plates

13 and 14 of the chamber 12 are connected by conduits 16 in which the combustion air is admitted and which is heated by known means and comes from a conduit 17. The gas is also heated by known means and is introduced at 18 (for instance natural gas or butane).

The holes 15 in the plate 14 are inclined towards the exit of the conduits 16 so as to carry out the air-gas mixture.

FIG. 4 shows the lay-out of the air conduits 16 and of the holes 15 which are bored in the plate 14. The air and the gas are admitted through conduits l7 and 18 respectively, on which are mounted regulating valves with remote control, of a conventional type (not shown). At 19 a conduit is shown connecting the gas exit of the mixing chamber 12 with a conduit 20 inside which a fixed ring with blades 21 is mounted in order to complete the mixture of air and fuel before the latter is introduced in the body of the burner 22 at the end of which the mixture is ignited by a conventional spark plug 23. The ignited gas burns in the conduit 24 which is the entry of the port 3 and which is mounted in the wall 4 of the furnace. At 25 a hole for measuring the oxygen or hydrogen contents of the burners is shown. The regulation of the burners is very easy.

The diagram of FIG. 5 shows the distribution of the oxygen or hydrogen contents in the section shown at the right hand of each hole 25. An advantage of the present process is that the heating equipment is extremely simple.

FIG. 6 shows a complete anode production unit. At 26 the vertical furnace has been shown with four rows of burners 3 and a tap hole 2. The hearth 1 inclined towards the tap hole 2 is in this case directly connected with the reverberatory furnace 27, which is equipped in a conventional way. At 28 the chimney for the exhaust of gases from the reverberatory furnace is shown, which chimney may be equipped with a heat recuperator 29. The charging of the impure copper is done in the vertical furnace at 30.

At 31 are shown the chimney and the regulator for discharging the gases originating from the burners 3, after having passed through the continuous charge column in the furnace 26.

FIG. 7 shows a copper anode production unit comprising a vertical furnace 26 feeding two reverberatory furnaces 27. This arrangement allows a better utilization of the melting capacity of the vertical furnace the melting process proceeds in order to charge one of the reverberatory furnaces, whilst in the other reverberatory furnace the refining and anode casting operations are going on. In the laying out of FIG. 7 it will be noted that the furnace 26 and the reverberatory furnace 27 are connected by means of a spout 32, which connects the tap holes 2 of the vertical furnace to the hole 33 of the reverberatory furnace. With a view to speeding up the oxidizing refining of copper, this laying out enables injecting in 33, below the copper jet, a stream of oxygen-containing gas in such a quantity as to oxidize the impurities in the copper. If the copper is very impure, the blowing of oxygen-containing gas may cause pulverization of the copper jet when the latter enters the reverberatory furnace.

FIG. 8 shows a continuous anode production unit consisting of a vertical furnace 27 which feeds alternately via the spouts 35, two tilting furnaces 34, in which the conventional processes of oxidizing refining and skimming take place. These processes take place in one of the two furnaces as the charging goes on, the refining and the slagging being finished when the furnace is full. Meanwhile the other furnace is emptied via the spout 36 into a poling unit 37, which feeds continuously the circular or

rectilinear casting units

38 or 39.

The cycle is regulated in such a way that one of the poling and casting furnaces is empty when the other one is full.

What I claim is:

1. A process for melting and refining copper in a vertical furnace zone which comprises:

A. charging the copper pieces to be melted to the upper part of said vertical furnace zone;

B. injecting a stream of hot gases into said vertical furnace zone through burners mounted along the perimeter of said vertical furnace zone;

C. directly contacting said stream with said copper pieces to melt said pieces;

D. said stream of hot gases originating from the combustion of a non-solid fuel with an oxygen-contain ing gas, and wherein said gas resulting from the combustion and ignited before coming into contact with the copper pieces, is a substantially neutral gas, the variation around the neutral point being such that the oxygen content is lower than about 0.5 percent of O and the hydrogen content is lower than about 0.5 percent of hydrogen;

E. the pressure of said gas being such that the ignited gas leaving the burners shall be capable of piercing the liquid mass situated at the level of the burners; and

F. discharging the molten material into a holding furnace zone through a tapping hole at the lower part of said vertical furnace zone, adjacent to the bottom of said vertical furnace zone; and wherein G. the pressure of the gas in the vertical furnace zone at the level of the burner'and at the level of the tapping hole for the molten material is between 35 and 130 gr/cm so as to violently expel the molten material containing small pieces and unmolten slag from the vertical furnace zone.

2. A process as claimed in claim 1 in which the pressure of the ignited gas leaving the burners and injected into the vertical furnace zone is between 100 and 380 gr/cm 3. A process as claimed in claim 1 wherein the pressure of the ignited gas leaving the burners and injected into the vertical furnace zone is about 180 gr/cm.

4. A process as claimed in claim 1 in which the nonsolid fuel contains sulfur.

5. A process as claimed in claim I in which sand, silica or a silica containing compound are used for melting the copper pieces when impure copper rich in iron is treated.

6. A process as claimed in claim 1 in which the pieces of copper to be melted are stacked sufficiently high so that a high resistance to the upwards passage of the combustion gas is obtained.

7. A process as claimed in claim 6 in which the height of the stacked pieces of copper is of at least 6 meters.

8. A process as claimed in claim 1 in which the total heat output of the ignited gas injected into the vertical furnace zone is between 250 and 900 Kcal per Kg of copper.

9. The process of claim 1 wherein the molten material is caused to flow in the hearth zone of said vertical furnace zone towards the tapping hole at a slope adapted to the natural flow slope of the molten material and further comprising injecting stream of said hot gases into said vertical furnace zone through row of urners at the lower part of the vertical furnace zone wherein the plane containing the centers of the outlet orifices of the burners of said row of burners is inclined in the direction of the flow of the molten material in the hearth zone and remaining as near as possible above the upper edge of said tapping hole.

10. The process of claim 1 wherein the molten material is caused to flow in the hearth zone of said vertical furnace zone towards the tapping hole at an angle between 6 and 18.

1 1. The process of claim 10 wherein said angle is 12.

12. The process of claim 9 in which the distance between the lower edge of the openings for the burners of said row and the hearth zone of the furnace is between 3 and 10 cm.

13. The process of claim 9 wherein the ratio between the angle of slope of the horizontal line relative to the plane containing the centers of the outlet orifices of the burners of said row of burners and the angle of the slope of the flow of the molten material in the hearth zone towards the tapping hole is between 1 and 0.5.

14. The process of claim 1 which comprises injecting streams of said hot gases into said vertical furnace zones through four rows of burners and wherein the planes passing through the centers of the outlet orifices of the burners of the upper two rows of burners are horizontal.

15. The process of claim 1 which further comprises injecting stream of said hot gases through at least one burner directly into the tapping hole.

16. The process of claim 1 which further comprises conducting the molten material from the vertical furnace zone to two furnace zones whereby said molten material is subjected to an oxidizing-refining in one of said two furnace zones and whereby said molten material is subjected to poling in the other of said two furnace zones.

17. The process of claim 9 in which the streams of hot gases leave the burners in each row in a direction inclined relatively to the hearth.

18. The process of claim 17 wherein the ratio between the slope relative to a horizontal line of each burner in each row and the slope of the hearth zone towards the tapping hole is comprised between 1 and 1.40.

Claims

1. A process for melting and refining copper in a vertical furnace zone which comprises: A. charging the copper pieces to be melted to the upper part of said vertical furnace zone; B. injecting a stream of hot gases into said vertical furnace zone through burners mounted along the perimeter of said vertical furnace zone; C. directly contacting said stream with said copper pieces to melt said pieces; D. said stream of hot gases originating from the combustion of a non-solid fuel with an oxygen-containing gas, and wherein said gas resulting from the combustion and ignited before coming into contact with the copper pieces, is a substantially neutral gas, the variation around the neutral point being such that the oxygen content is lower than about 0.5 percent of O2 and the hydrogen content is lower than about 0.5 percent of hydrogen; E. the pressure of said gas being such that the ignited gas leaving the burners shall be capable of piercing the liquid mass situated at the level of the burners; and F. discharging the molten material into a holding furnace zone through a tapping hole at the lower part of said vertical furnace zone, adjacent to the bottom of said vertical furnace zone; and wherein G. the pressure of the gas in the vertical furnace zone at the level of the burner and at the level of the tapping hole for the molten material is between 35 and 130 gr/cm2 so as to violently expel the molten material containing small pieces and unmolten slag from the vertical furnace zone.

2. A process as claimed in claim 1 in which the pressure of the ignited gas leaving the burners and injected into the vertical furnace zone is between 100 and 380 gr/cm2.

3. A process as claimed in claim 1 wherein the pressure of the ignited gas leaving the burners and injected into the vertical furnace zone is about 180 gr/cm2.

4. A process as claimed in claim 1 in which the non-solid fuel contains sulfur.

5. A process as claimed in claim 1 in which sand, silica or a silica containing compound are used for melting the copper pieces when impure copper rich in iron is treated.

9. The process of claim 1 wherein the molten material is caused to flow in the hearth zone of said vertical furnace zone towards the tapping hole at a slope adapted to the natural flow slope of the molten material and further comprising injecting stream of said hot gases into said vertical furnace zone through row of burners at the lower part of the vertical furnace zone wherein the plane containing the centers of the outlet orifices of the burners of said row of burners is inclined in the direction of the flow of the molten material in the hearth zone and remaining as near as possible above the upper edge of said tapping hole.

10. The process of claim 1 wherein the molten material is caused to flow in the hearth zone of said vertical furnace zone towards the tapping hole at an angle between 6* and 18*.

11. The process of claim 10 wherein said angle is 12*.