Pit furnace for smelting copper and method therefor

Abstract

The invention relates to a pit furnace (1) for smelting a charge into molten copper, comprising a vertically arranged steel shell (2) and a refractory furnace lining (3) arranged in the steel shell, the steel shell (2) having at least one charge opening (4) for supplying the charge into the pit furnace (1) and an outlet opening (5) for removing molten copper from the pit furnace (1), burners (6), preferably a plurality of burners (6), are arranged in a predetermined plane of the pit furnace (1) between the charging opening (4) and the discharging opening (5), which burners (6) are arranged in a plurality of planes and in rows around the pit furnace (1) for heating the charge and for smelting copper, characterized in that the burners (6) are arranged in the plurality of planes and in rows around the pit furnace (1). According to the invention, the steel shell (2) of the pit furnace (1) is cylindrical at least in an upper region (7) above the uppermost burners (6) or the uppermost row of burners (6), and the refractory furnace lining (3) comprises a series of cylindrical sub-sections (8a-8e) in the upper region (7) from top to bottom, which sub-sections are arranged concentrically to one another and whose diameters increase by sub-sections (8). The invention also relates to a method for smelting a charge into molten copper in such a pit furnace.

Description

Technical Field

[0001] The invention relates to a pit furnace for melting a charge material, in particular a copper cathode, into molten copper, the pit furnace having a vertically arranged steel shell and a protective lining arranged in the steel shell, wherein the steel shell has at least one charging port for supplying the charge material into the pit furnace and a discharge port for allowing the molten copper to flow out of the pit furnace. A burner is arranged in a predetermined plane of the pit furnace between the charging port and the discharge port, preferably a plurality of burners are arranged, which are arranged in a row and in a plurality of planes around the pit furnace for heating the charge material and melting the copper. The invention also relates to a method for melting a charge material, such as a copper cathode, into molten copper in such a pit furnace. Background Art

[0002] Methods and pit furnaces (also called vertical furnaces) for smelting copper have been known in the prior art for decades. In this process, the copper is charged in solid form via an upper charging opening and heated and smelted by burners, for example gas burners, arranged in the lower region of the pit furnace and finally discharged from the pit furnace via a discharge opening arranged in the lower region of the pit furnace, for example via a connecting channel into a holding furnace (Halteofen) or directly to a corresponding casting device. As the charge passes through the pit furnace from top to bottom, it is continuously heated and reaches the minimum temperature of about 1250 degrees Celsius required for smelting copper in the region of the smelting zone. A pit furnace usually consists of a cylindrical steel shell and a protective lining arranged in the steel shell.

[0003] Such a pit furnace and its method of operation are known, for example, from patent document DE 2 062 144 A1. Patent document CN 214701690 U likewise describes a vertical furnace for producing copper with a vertically arranged furnace body.

[0004] It is known from the prior art to monitor the filling level of a pit furnace with the aid of a camera, which should preferably be filled with copper cathodes at least up to 1 m below the charging opening. If the filling level drops, the operator loads new cathodes into the furnace. The steel structure of the furnace and the refractory lining between the loading area and the burner area are usually cylindrical. The bricks of the refractory lining are designed here so that the long sides preferably correspond to the radius of the combustion chamber formed by the steel shell. It is necessary here to avoid blockages during the filling process, such as getting stuck when sliding down in the shaft, wherein any deviations from the cylindrical shape of the steel shell of the pit furnace or from the shaped bricks adapted to the furnace geometry are complicated in terms of production, assembly and statics.

[0005] Furthermore, the setting of the burner power is usually designed in such a way that the burner power is set entirely as a function of the filling level of the subsequent holding furnace, which serves as a reservoir for the downstream casting plant.

[0006] The molten copper flows continuously through the usually inclined bottom area of ​​the pit furnace below the bottom row of burners and is introduced into the connecting channel to the holding furnace via a built-in tapping opening embedded in the furnace wall. The dimensions of the tapping opening are based on empirical values.

[0007] A disadvantage of the prior art known from practice is that monitoring the filling level by means of a camera requires constant attention from the plant operator. The operator is usually responsible for pouring the newly loaded cathodes into the furnace in a timely manner by means of a loading device. If loading takes place too early, the cathodes cannot be positioned in the preferred vertical orientation by means of the loading device and lie obliquely or horizontally in the shaft. This can hinder an optimal heat exchange between the exhaust gas and the descending cathode material during subsequent operation. On the other hand, if loading takes place too late, the furnace lining can be damaged where the cathodes strike the refractory lining from an excessively high descent height. Furthermore, if the furnace is not continuously filled completely, the energy efficiency is reduced.

[0008] During loading, the cathodes fall onto the previously loaded cathode layer in a relatively random orientation. The burners in the lower region of the furnace melt the cathodes, and the melt flowing out at the bottom of the furnace flows out through the discharge opening. The cathodes slide continuously from top to bottom, wherein the temperature rises continuously from top to bottom. In this process, the furnace lining and the cathodes expand and often get stuck. The cathodes usually only slide when additional cathodes are loaded from above or when stuck material deforms and loosens. This results in the supply to the burner area no longer being carried out continuously, but in batches, so that the melting rate of the pit furnace changes.

[0009] Frequent interruptions of the continuous decline known from practice and the resulting fluctuating melting rates make automated operation of the furnace difficult or even impossible, since the burner powers have to be frequently varied and the power distribution between the individual burners has to be changed.

[0010] The geometry of the tapping opening is also very important for the energy balance of the furnace and its reliability. For example, if the tapping opening is too large, too much energy can escape through the tapping opening into the adjacent connecting channel and cause problems there, such as overheating of the burner located there. On the other hand, if the tapping opening is too small, there is a risk of clogging and freezing of copper in the bottom area of ​​the pit furnace. In the prior art to date, the geometry of the tapping opening could only be subsequently optimized after the furnace had been shut down and the furnace lining had been refinished. Summary of the invention

[0011] The object of the invention is therefore to monitor the furnace filling level automatically, ideally and to replace the user control. Furthermore, it should be achieved according to the invention that the blocking of the cathode can be avoided in order to achieve a targeted and continuous melting rate in the pit furnace. The invention should enable an automatic regulation of the burner power instead of the previously known manual readjustment of the burner power. Finally, the geometry of the discharge opening should be able to be changed and optimized from the outside without affecting the actual lining of the pit furnace, thereby ultimately achieving a continuous and stable operation of the pit furnace, preferably with significantly reduced energy consumption.

[0012] In the sense of the invention, this object is achieved by a pit furnace comprising the features of claim 1 and by a method comprising the features of claim 15. Advantageous embodiments of the invention are defined in particular in the dependent claims.

[0013] According to the present invention, a pit furnace for melting a charge into molten copper is provided, the pit furnace having a vertically arranged steel shell and a refractory lining arranged in the steel shell. The pit furnace has at least one charging port for supplying the charge into the pit furnace and a discharge port for allowing the molten copper to flow out of the pit furnace. A burner is arranged in a predetermined plane between the charging port and the discharge port of the pit furnace, preferably a plurality of burners are arranged, which are arranged in a plurality of planes and in rows around the pit furnace for heating the charge and for melting copper. According to the present invention, the steel shell of the pit furnace is cylindrical at least in the upper region above the uppermost burner or the uppermost row of burners, and the refractory lining in the upper region includes a series of cylindrical subsections from top to bottom, which are arranged concentrically with each other and have corresponding diameters that increase from subsection to subsection.

[0014] Therefore, in the sense of the invention, a pit furnace is provided, the inner diameter of which gradually increases at least in partial areas, preferably in the main part of the pit above the burner (greater than 70% of the pit length, preferably greater than 80% of the pit length), in particular in that part of the pit which is connected to the area below the charging port and extends to the uppermost burner plane, and particularly preferably over the entire length of the pit above the burner, so that a continuous and undisturbed downward slide of solid charge material, for example in the form of copper cathode plates, is possible despite the heating of both the refractory lining and the charge material during operation of the pit furnace.

[0015] It is particularly preferred if the pit furnace has at least three, preferably at least five, such subsections which are successive and adjoining one another, wherein the inner diameter of the refractory lining increases.

[0016] This ensures that, despite the thermal expansion of the furnace lining and cathodes, the cathodes can be prevented from getting stuck in the pit furnace, while maintaining the cylindrical steel shell. The loaded cathodes can slide down despite the thermal expansion and ensure continuous furnace operation. The continuous temperature increase from top to bottom in the pit furnace ensures an optimal heat exchange between the exhaust gas from the burner and the descending cathode material.

[0017] In a preferred embodiment of the invention, the diameter of the cylindrical subsection of the refractory lining is designed such that the thermal expansion of the refractory material, preferably the thermal expansion of the refractory material and the charge material, is at least compensated under the operating conditions of the pit furnace. This ensures trouble-free operation of the pit furnace, wherein the charge material, in particular the copper cathode, can be reliably passed through when transferring from a first subsection of the refractory lining to an adjacent second subsection arranged below the first subsection, without the cathode material having difficulty sliding down due to jamming. In the sense of the invention, the terms "first subsection" and "second subsection" include any pair of two subsections that are arranged one above the other and adjacent to one another.

[0018] Preferably, the difference in diameter between the first subsection and the second subsection is at least 16 mm, preferably at least 20 mm.

[0019] In another preferred embodiment of the invention, at least one sensor, preferably three sensors arranged one above the other, are provided for measuring the filling level of the charge of the pit furnace. The sensors are particularly preferably arranged above the uppermost burner plane and directly below the charging opening, and particularly preferably, for the uppermost sensor, it is arranged no more than 1 m below the charging opening. In a very preferred embodiment of the invention, at least one sensor, preferably three sensors, is each assigned a receiver, which is particularly preferably arranged opposite the respective sensor in the plane of the respective sensor at the pit furnace. This enables a simple and reliable measurement of the filling level of the pit furnace, which does not require visual inspection.

[0020] The sensor thus measures the filling level of the pit furnace horizontally and can determine whether the pit furnace is filled in the corresponding plane covered by the sensor and the receiver which is possibly connected to the sensor. Preferably, a warning signal is emitted when the filling level falls below a predetermined threshold value, which indicates whether a new charge is required. In this regard, it is particularly preferred to connect the sensor to a device which automatically triggers refilling by the charging system when the predetermined threshold value is fallen below. This makes it possible to achieve a higher degree of automation than in pit furnaces known hitherto for melting the charge material into molten copper by particularly simple means.

[0021] Ideally, three sensors are arranged in the pit furnace below the charge plane at a distance of preferably 400-600 mm, in particular 450-550 mm, very particularly preferably 500 mm relative to one another and measure whether charge is present in the scanned plane. In this region of the pit furnace, in which copper is heated from room temperature almost to melting temperature, the copper cathode or any other charge is prevented from getting stuck, i.e., by at least compensating for the thermal expansion of the charge by increasing the diameter of the refractory material stepwise from top to bottom. The thermal expansion of copper is 16.5×10 -6 / K, and the thermal expansion of the furnace lining is about 5×10 -6 / K. The furnace lining is designed in such a way that, on the one hand, the cost-effective cylindrical shape of the steel shell and the refractory material above the burner row is retained and, on the other hand, the load-bearing capacity of the refractory lining is ensured and the production of precast bricks is kept as cost-effective as possible.

[0022] According to the invention, it is preferred that a measuring sensor, preferably a measuring probe connected to the pit furnace, is arranged in the region of the discharge opening for measuring the temperature of the molten copper when it leaves the discharge opening. In particular, when the current productivity of the downstream casting plant is also measured, the heat balance of the pit furnace can be calculated with the aid of a process model and the currently required gas quantity or burner power of each burner or burner row can be determined. This gives the basic setting of the burners: the burner power is usually set so that the burners in the corresponding row work at the same power and the power distribution of the individual rows is preset. In particular, when the current weight of the copper melt and the weight change are determined in the holding furnace downstream of the pit furnace, these values ​​can be used to continuously correct the above settings. With this regulation, in particular after the pit furnace has been started, there is no need for further manual intervention in the burner settings, and the operation of the pit furnace is preferably carried out completely automatically.

[0023] It is also preferred that the refractory lining for the discharge opening is designed to protrude from the area of ​​the refractory lining and protrude from the inside to the outside through the steel shell beyond the longitudinal extension of the steel shell. Here, the height of the discharge opening is preferably defined by a profiled brick, which is laterally engaged in the adjacent refractory bricks and fixed from above by further bricks. In this regard, it is particularly preferred that the refractory lining, in particular the profiled bricks and the refractory bricks surrounding the profiled bricks, which protrude beyond the steel shell of the pit furnace, are surrounded by a steel jacket or steel frame, by which the sealing of the area of ​​the opening of the pit furnace around the profiled bricks can be ensured. In this regard, it is particularly preferred that a part of the steel jacket or steel frame, in particular the upper steel plate, is detachably connected to the steel jacket or steel frame. The detachable connection of the steel plate to the rest of the steel jacket or steel frame can preferably be achieved by clamping or threaded engagement. After removing the steel plate, the refractory bricks and / or profiled bricks embedded in the steel jacket or steel frame can be approached unhindered without affecting the furnace interior of the pit furnace.

[0024] According to the invention, it is also particularly preferred that a holding furnace is arranged downstream of the discharge opening of the pit furnace, which is connected to a sensor, preferably a weighing unit, for measuring the weight of the melt in the holding furnace and for detecting weight changes in the holding furnace. This allows particularly simple means to obtain measurement parameters that allow the heat balance of the pit furnace to be calculated with the aid of a process model and the currently required gas quantity or burner power to be determined in connection therewith.

[0025] It is particularly preferred if the power of each burner row, preferably each individual burner, can be regulated or controlled individually and preferably automatically.

[0026] In another preferred embodiment of the invention, a plurality of thermocouples are arranged in the region of the refractory lining, in particular in the region of the burner and / or in a shaft arranged above the burner, for detecting the temperature of the refractory lining. The measured values ​​detectable in this way can be used to optimize the temperature of the lining with regard to the service life of the lining and to preferably automatically operate the pit furnace.

[0027] Furthermore, it is preferred that the control or regulating unit is set up and designed to control or regulate, preferably automatically, the filling level of the pit furnace and / or the melting rate of the pit furnace, in particular to ensure a continuous supply of charge material and / or a melting rate that is as constant as possible. All this serves to increase the efficiency of the pit furnace and to achieve the highest possible thermal efficiency.

[0028] According to another aspect of the invention, a method for smelting a charge into molten copper in a pit furnace according to the first aspect of the invention is provided. The method according to the invention is characterized in that a control or regulation unit preferably automatically controls or regulates the charge of the pit furnace, the filling level in the pit furnace and the power of each row of burners, preferably each individual burner.

[0029] In this context, it is particularly preferred if the control or regulating unit calculates the heat balance of the pit furnace based on the measured parameters and using the process model.

[0030] The measured parameters used for this purpose include the filling level of the pit furnace, the temperature of the molten copper when it leaves the tapping opening and preferably also the weight and / or weight change of the molten copper in a holding furnace arranged downstream of the tapping opening, and particularly preferably also the productivity of the casting plant downstream of the pit furnace.

[0031] In this context, it is particularly preferred if the measured parameters for calculating the heat balance of the pit furnace are input into a process model, by means of which the currently required burner power, in particular the required fuel quantity per burner, is determined.

[0032] The geometry of the tapping opening determines the energy balance of the furnace, which also applies to the reliability of the overall operation of the pit furnace. The geometry of the tapping opening significantly limits the amount of hot air that is discharged from the pit furnace into the connecting guide groove. The lower this amount of hot air, the higher the energy efficiency of the overall operation of the pit furnace. At the same time, it must be taken into account that slag in particular hinders the discharge of molten copper from the tapping opening. It is therefore particularly advantageous if the components that define the tapping opening, such as molded bricks and refractory bricks surrounding the molded bricks, are arranged so as to be easily accessible and are located outside the steel shell. In addition, the provision of a steel jacket or a steel frame around the part of the tapping opening that protrudes from the steel shell makes it possible to effectively limit the undesirable discharge of hot air. Access to all components of the tapping opening can still be easily achieved using preferably removable steel plates at the steel jacket or steel frame.

[0033] According to the invention, it is thus possible to ensure that the melting rate of the pit furnace does not vary or varies only minimally. In addition, it is possible to ensure that the pit furnace is optimally filled, so that a high thermal efficiency can be achieved. By continuously supplying the combustion chamber with charge material, an effective regulation of the melting rate of the pit furnace can be achieved, while an automatic setting of the burner can be carried out by the implemented regulation. Finally, by optimizing the discharge port height, the energy balance of the furnace can also be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The present invention is explained in more detail below with reference to five figures, wherein these figures show preferred embodiments of the present invention, which do not limit the scope of protection of the present invention. In the figures:

[0035] Figure 1 shows a schematic cross-sectional view of a pit furnace according to the invention;

[0036] Figure 2 Shown according to Figure 1 Detailed view of the upper area of ​​the pit furnace;

[0037] Figure 3 A cross-sectional view of a refractory lining in the region of a discharge opening of a pit furnace according to the invention is shown;

[0038] Figure 4 shows a schematic cross-sectional view of a system for measuring fill levels in three planes; and

[0039] Figure 5 The schematic diagram of the automatic burner control in the pit furnace according to the invention is shown. DETAILED DESCRIPTION

[0040] Figure 1A cross-sectional view of a pit furnace 1 for smelting a charge into molten copper according to the present invention is shown. The pit furnace 1 consists of a vertically arranged steel shell 2 and a refractory lining 3 arranged in the steel shell. The steel shell 2 has a charging port 4 arranged in the upper part of the pit furnace 1 for supplying the charge into the pit furnace 1 and a discharge port 5 for allowing the molten copper to flow out of the pit furnace 1. In the lower region of the pit furnace 1, burners 6 are arranged in rows or layers around the pit furnace 1, wherein three rows of burners 6 are provided in the current embodiment. The upper two rows of burners 6a, 6b are arranged in a horizontal plane in the pit furnace 1, while the plane of the lower row of burners 6c is substantially parallel to the inclined bottom plane 7 in the pit furnace 1, along which the molten copper is guided toward the discharge port 5 in the region of the burners 6. Above the region of the burners 6, the pit furnace 1 has a shaft region 7, in which the essentially solid charge in the form of a copper cathode is conveyed from top to bottom by gravity and is continuously heated there from the charging temperature to the melting temperature. In the present case, the shaft region 7 of the pit furnace 1 above the burners 6 has a height of about 9 m and a minimum inner diameter of 1804 mm. The shaft region 7 of the pit furnace 1 above the burners 6 consists of a plurality of cylindrical subsections 8a-8e, the diameter of which increases by 20 mm from subsection to subsection 8. The diameter of the subsection 8 is designed in such a way that even when the refractory material is heated, there is a temperature gradient from top to bottom and from inside to outside, and it is ensured that the charge slides reliably from top to bottom through the plurality of subsections 8a-8e of the refractory lining 3.

[0041] Figure 2 Shows Figure 1 Detailed view of the upper region of the pit furnace 1 in FIG. In the region of the charging opening 4, the cylindrical section of the refractory lining 3 has a diameter of 1804 mm, which adjoins downwards in the direction of gravity the first subsection 8a of the refractory lining 3. Next, a further subsection 8b is arranged in the refractory lining 3, which has an inner diameter which is again 20 mm larger than the upper adjoining subsection 8a, and thus is 1844 mm.

[0042] Figure 3 A cross-sectional view of the region of a pit furnace (not shown) in the region of the discharge opening 5 is shown. The discharge opening 5 is defined by profiled bricks 5a, which are surrounded at the top and bottom by rows of refractory bricks 5b. The profiled bricks 5a and the refractory bricks 5b directly adjacent to the profiled bricks 5a are arranged in such a way that at least a portion of the profiled bricks 5a protrudes beyond the longitudinal extension of the steel shell 2 beyond the pit furnace 1. The protruding sections of the profiled bricks 5a and the refractory bricks 5b surrounding them are surrounded by a steel jacket or steel frame connected to the steel shell 2. An integral component of the steel jacket or steel frame is an upper steel plate 5c, which is detachably connected to the steel jacket or steel frame by clamping elements. If the steel plate 5c is removed, those parts of the refractory composition of the discharge opening 5 that protrude beyond the steel shell 2 are essentially accessible without hindrance.

[0043] Figure 4 A schematic partial view of the upper region of a pit furnace 1, approximately 1 m below a charging opening (not shown), is shown. On the outside of the steel shell 2, three sensors 12a to 12c and three receivers 13a to 13c operatively connected thereto are shown in three planes 10a to 10c, approximately 1 m below a charging opening (not shown) and at a distance of approximately 500 mm from one another. The sensors 12a to 12c can thus determine whether solid charge material is present in the pit furnace 1 at the level of the sensors 12a to 12c and the receivers 13a to 13c.

[0044] Figure 5 The schematic diagram of the automatic regulation of the burner power in the pit furnace 1 according to the invention is shown. The temperature of the molten copper discharged from the discharge opening 5 is measured by the measuring unit 9a and the weight of the molten copper in the holding furnace 14 is measured by the measuring unit 9 and fed to the control or regulating unit 15, by which the power of the corresponding burner 6 in the pit furnace 1 is set taking into account the current production rate of the downstream and not shown casting equipment. Thus, with preferably constant burner power and a constant flow of molten copper from the discharge opening 5 into the holding furnace 14, constant operation of the pit furnace 1 is ensured essentially automatically.

[0045] Reference numerals list

[0046] 1 Pit furnace

[0047] 2 Steel shell

[0048] 3 Refractory lining

[0049] 4 loading port

[0050] 5 Discharge port

[0051] 5a Molded bricks

[0052] 5b Refractory Bricks

[0053] 5c Steel Plate

[0054] 6 Burner

[0055] 7 Bottom plane

[0056] 8 Well Area

[0057] 9 Measurement units

[0058] 9a Measuring unit

[0059] 10a-10c Sensor plane

[0060] 12a-12c Sensors

[0061] 13a-13c Receiver

[0062] 14. Holding furnace

[0063] 15 Control or regulating unit.

Claims

1. A pit furnace (1) for smelting a charge into molten copper, the pit furnace having a vertically arranged steel shell (2) and a refractory lining (3) arranged in the steel shell, wherein: The steel shell (2) has at least one charging port (4) for supplying the charge material into the pit furnace (1) and a discharge port (5) for allowing the molten copper to flow out of the pit furnace (1), wherein a burner (6) is arranged in a predetermined plane between the charging port (4) and the discharge port (5) of the pit furnace (1), preferably a plurality of burners (6) are arranged, which are arranged in multiple planes and in rows around the pit furnace (1) for heating the charge material and for smelting copper, characterized in that the steel shell (2) of the pit furnace (1) is constructed as a cylinder at least in the upper area (7) above the uppermost burner (6) or the uppermost row of burners (6), and the refractory lining (3) in the upper area (7) includes a series of cylindrical sub-segments (8a-8e) from top to bottom, the sub-segments are arranged concentrically with each other, and their diameters increase from sub-segment (8) to sub-segment (8).

2. The pit furnace (1) according to claim 1, characterized in that The diameter of the cylindrical subsections (8a-8e) of the refractory lining (3) is designed such that thermal expansion of the refractory material (3), preferably of the refractory material (3) and of the charge material, is at least compensated under operating conditions of the pit furnace (1).

3. A pit furnace (1) according to any one of the preceding claims, characterised in that The diameter of the second subsection (8b) adjacent to the first subsection (8a) is at least 16 mm, preferably at least 20 mm, greater than the diameter of the first subsection (8a).

4. A pit furnace (1) according to any one of the preceding claims, characterised in that The cylindrical subsections ( 8 a - 8 e ) each have a height of at least 1200 mm, preferably greater than 1300 mm, in particular between 1300 mm and 1400 mm.

5. Pit furnace (1) according to any one of the preceding claims, characterized in that At least 4, preferably 5, cylindrical subsections (8a-8e) are arranged one on top of the other.

6. Pit furnace (1) according to any one of the preceding claims, characterized in that At least one sensor (12), preferably three sensors (12a-12c) stacked on top of each other, for measuring the filling level of the pit furnace (12) with the charging material in the pit furnace (1) are preferably arranged above the uppermost burner plane (6a), in particular immediately below the charging port (4), and particularly preferably, the uppermost sensor (12a) is arranged no more than 1 m below the charging port (4).

7. The pit furnace (1) according to claim 6, characterized in that The at least one sensor (12), preferably the three sensors (12a-12c), are each assigned a receiver (13), which is arranged on the pit furnace (1) in a plane (10) of the sensor (12), preferably opposite the respective sensor (12).

8. Pit furnace (1) according to any one of the preceding claims, characterized in that In the region of the tapping opening (5), a measuring sensor, preferably a measuring probe connected to the pit furnace, is arranged for measuring the temperature of the molten copper as it leaves the tapping opening (5).

9. Pit furnace (1) according to any one of the preceding claims, characterized in that The refractory lining (3) is arranged in the region of the discharge opening (5) to protrude laterally beyond the steel shell (2) of the pit furnace (1) from the inside to the outside.

10. Pit furnace (1) according to any one of the preceding claims, characterized in that The refractory furnace lining (3) has at least one shaped brick (5a) in the area of ​​the discharge port (5) which defines the height of the discharge port (5), and the shaped brick is surrounded from above, below and from the side by bricks (5b) of the refractory furnace lining (3) adjacent to the shaped brick (5a), wherein the discharge port (5), in particular the shaped brick (5a) and the refractory bricks (5b) surrounding the shaped brick are arranged to protrude beyond the steel shell (2) and are surrounded by a steel jacket or a steel frame, and the steel jacket or the steel frame has a steel plate (5c), preferably a steel plate (5c) arranged at the upper part of the steel jacket or the steel frame, and the steel plate is detachably connected to the steel jacket or the steel frame.

11. The pit furnace (1) according to claim 10, characterized in that The connection between the steel plate (5c) and the steel sleeve or the steel frame is achieved by clamping or threaded connection.

12. Pit furnace (1) according to any one of the preceding claims, characterized in that A holding furnace (14) is arranged downstream of the discharge port (5) of the pit furnace (1), and the holding furnace is connected to a sensor, preferably a weighing unit (9), for measuring the weight of the melt in the holding furnace (14) and detecting weight changes in the holding furnace (14).

13. A pit furnace (1) according to any one of claims 6 to 12, characterised in that The sensor (12) is connected to a monitoring unit which is designed and arranged to emit at least one warning signal when the charge material filled in the pit furnace (1) falls below a predetermined threshold value and preferably to emit an instruction for loading the pit furnace (1) with charge material, in particular automatically.

14. Pit furnace (1) according to any one of the preceding claims, characterized in that The pit furnace is connected to a control or regulating unit (15) which calculates the heat balance of the pit furnace (1) based on the measured parameters and using a process model and thereby determines the currently required burner power, preferably the currently required fuel quantity.

15. The pit furnace (1) according to claim 14, characterized in that The control or regulation unit (15) is designed and configured to control or regulate the power of each row of burners (6a-6c), preferably each individual burner (6), individually and preferably automatically.

16. Pit furnace (1) according to any one of the preceding claims, characterized in that A plurality of thermocouples are arranged in the region of the refractory lining (3), in particular in the region of the burner (6) and / or in a shaft (7) arranged above the burner, for detecting the temperature of the refractory lining (3).

17. A pit furnace (1) according to any one of claims 14 to 16, characterised in that The control or regulating unit (15) is set up and designed to control or regulate, preferably automatically, the filling level of the pit furnace (1) and / or the melting rate of the pit furnace (1), in particular to ensure a continuous supply of charge material and / or a melting rate that is as constant as possible.

18. Method for smelting a charge into molten copper in a pit furnace (1) according to any one of the preceding claims, characterized in that The control or regulation unit (15) preferably automatically controls or regulates the loading of the pit furnace (1), the filling level in the pit furnace (1) and the power of each row of burners (6a-6c), preferably each individual burner (6).

19. The method according to claim 18, characterized in that The control or regulating unit (15) calculates the heat balance of the pit furnace (1) based on the measured parameters and using a process model.

20. The method according to claim 19, characterized in that The measured parameters include the filling level of the pit furnace (1), the temperature of the molten copper when it leaves the discharge port (5), and preferably also the weight and / or weight change of the molten copper in a holding furnace (14) arranged downstream of the discharge port (5), and particularly preferably also the productivity of the casting equipment downstream of the pit furnace (1).

21. The method according to claim 19 or 20, characterized in that The measured parameters for calculating the heat balance of the pit furnace (1) are input into a process model, by means of which the currently required burner power, preferably the required fuel quantity per burner (6), is determined.

22. The method according to any one of the preceding claims 18 to 21, characterized in that The height of the discharge opening (5) and / or its geometry, in particular the size of the discharge opening (5) and, associated therewith, the amount of hot air or hot gas discharged from the pit furnace (1) per unit time, can be varied.

23. The method according to any one of the preceding claims 18 to 22, characterized in that The operation of the pit furnace (1) takes place automatically at least after its start-up.

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