Patent Application
20210138539
The present application relates to a melt transfer system for receiving, transporting and feeding molten metal. The present invention furthermore relates to a corresponding method.
Transportable systems by way of which molten metal can be received and transferred are known from prior art. JP4190786, for example, shows a transport vessel to which molten metal can be fed. The molten metal can be transported in the vessel and fed out of the vessel by way of a set pressure difference between the interior of the vessel and the surrounding area.
So as to apply the pressure difference for emptying the vessel, for example, air can be introduced under pressure into the interior of the vessel. As a result, pressure can be applied to the molten metal present in the vessel so that the molten metal rises in a flow duct, in particular a riser, connecting the interior of the vessel and the surrounding area and can be fed out of the vessel. The pressure is typically increased steadily in the process, so that the molten metal is fed through the flow duct or the riser to the outside. At a point in time at which the molten metal present in the furnace has already been largely fed from the interior to the outside, the molten metal being fed to the outside may mix with air during emptying of the vessel. The hot molten metal can be drastically accelerated as a result of the admixed air, so that the molten metal may splash uncontrolled at an outlet of the holding furnace. Such hot molten metal splash is dangerous, in particular for operating staff, but also for sensitive devices present in the surrounding area of the transportable vessel.
In JP4190786, the filling process and the emptying process of the melt transfer device are controlled by a control unit, which analyzes the weight data of the melt transfer device. Based on the weight of the melt transfer device, it can be established how much molten metal is present in the vessel of the device. When the control unit establishes that the molten metal in the interior of the melt transfer device is running low, an emptying process of the vessel of the melt transfer device is ended.
It is the object of the present invention to provide an alternative melt transfer system. It is preferably an object of the present invention to provide a melt transfer system that enhances the occupational safety for operating staff and facilitates the work of operating staff. It can be a further object of the present invention to provide a corresponding method that achieves this object.
The above object is achieved by a method and/or a melt transfer system according to claim 1 and an additional independent claim. Advantageous refinements are described in the dependent claims.
The melt transfer system can be used to receive, transport and transfer hot molten metal into another vessel or into a furnace. For this purpose, the melt transfer system comprises a transportable vessel for receiving the molten metal, a vessel cover arranged on the vessel for closing the vessel in an air-tight manner, and a flow duct. The vessel cover preferably includes a closable filling opening for filling the vessel with the molten metal and a corresponding filling opening cover. As an alternative, the vessel cover can comprise a filling device for filling the vessel with molten metal through a filling pipe or through the flow duct.
The flow duct can, for example, be designed as a flow line or as a pipe, and preferably as a riser. The flow duct can have round or angular cross-sections. The flow duct preferably comprises a refractory material so that hot molten metal can flow through the flow duct. The flow duct has a first end arranged in the vessel, and a second end arranged outside the vessel for feeding the molten metal from the molten metal vessel. The melt transfer system preferably comprises a pneumatic unit for introducing air into the vessel. The air is introduced into the vessel under pressure. The pressure can be at least 0.1 bar, and preferably at least 0.2 bar.
Molten metal can be pushed out of the vessel through the flow duct or the riser and fed out of the vessel by way of a pressure difference between a pressure prevailing in the vessel and ambient pressure prevailing outside thereof. So as to maintain the feeding process when the vessel is being emptied, the pressure difference is typically increased. The feeding process can be interrupted or ended by lowering, or completely eliminating, the pressure difference. A control of the pressure application and a setting of the pressure difference can be manually settable by an operator. Preferably, however, a control unit controls the emptying of the vessel by setting the pressure difference between the first and second ends of the flow duct. The control unit controls a pneumatic unit, for example, which is designed to apply air pressure to the vessel interior.
The melt transfer system of the present application can furthermore comprise a measuring unit comprising at least one pressure sensor for measuring a pressure in the vessel during the feeding, as well as a control unit for controlling the feeding of the molten metal out of the vessel through the flow duct. The control unit may be configured and designed to halt the feeding of the molten metal in the event of a drop of the measured pressure. The control unit can furthermore be configured to determine a pressure profile over time from the pressure measured by the measuring unit.
So as to at least partially empty the melt transfer system, the molten metal can be fed out of the vessel through the flow duct. To this end, the control unit, for example, sets the pressure difference between the first and second ends of the flow duct. During the feeding, a pressure can be determined in the vessel, preferably by way of the control unit and a measuring unit comprising at least one pressure sensor. For example, the pressure can be measured directly in the vessel or in the aforementioned pneumatic unit. The pressure sensors are preferably arranged so as to measure the pressure of a vessel interior space in which the molten metal is located. The pressure sensors preferably do not make contact with the molten metal in the process. The at least one pressure sensor can be arranged on an inner side of the vessel cover, or in a pneumatic unit. The control unit can determine the pressure in the vessel from the measured pressure.
The feeding of the molten metal can be halted when a pressure difference between a pressure determined at a first point in time and a pressure determined at a second point in time is negative, wherein the negative pressure difference is preferably greater, in absolute terms, than a previously established threshold value. The first point in time is earlier compared to the second point in time, the second point in time being accordingly later than the first point in time. The pressure difference is ascertained by subtracting the pressure at the first point in time from the pressure at the second point in time. The threshold value is preferably, in absolute terms, at least 1 mbar, and particularly preferably at least 2 mbar, wherein the threshold value can be selected depending on the time lag between the first and second point in time.
A pressure profile over time can be determined based on the determined pressure. In particular, the control unit can be configured and designed to determine this pressure profile over time. This pressure profile over time can be recorded and monitored, for example by the control unit designed and configured for this purpose. The control unit typically carries out the control in such a way that air is continuously supplied to the vessel for continuously emptying the vessel so that the pressure in the vessel increases. The feeding of the molten metal can be halted in the event of a drop of the measured pressure. The control unit can be configured and designed to record and register such a pressure drop, and to thereupon halt the feeding of the molten metal. For this purpose, the control unit can control the pneumatic unit so as not to apply further pressure to the vessel and/or vent the vessel, so that the pressure difference remains constant or drops.
The control unit is designed and configured to carry out the control process steps described hereafter, and to halt the feeding of the molten metal, in particular by control of the pneumatic unit. Based on the pressure profile over time, the control unit is able to ascertain a pressure difference between at least two consecutive pressures.
The feeding of the molten metal can in particular be halted when the pressure difference is negative, that is, when the pressure ascertained later is lower than the pressure ascertained earlier, or when the mean value of two or more pressures ascertained later is lower than the mean value of two or more pressures ascertained earlier.
The pressures can be measured at defined time intervals. The intervals are preferably identical. The time intervals between the pressure measurements can, for example, be a maximum of 500 ms, preferably a maximum of 100 ms, and particularly preferably a maximum of 50 ms. The control unit can be designed and configured to carry out the pressure measurement at the time intervals, and to register the pressure values. The control unit can be designed and configured to set the time intervals of the measurements.
The time derivative dp/dt of the pressure profile can be ascertained from the pressures measured at defined time intervals. The feeding of the molten metal can, in particular, be halted when the derivative dp/dt is negative. A threshold value S can preferably be determined prior to or during the feeding of the molten metal, so that the feeding of the molten metal is only halted when the derivative is smaller than the threshold value S, wherein the threshold value S is smaller than zero. One criterion for halting the feeding of the molten metal can thus be when dp/dt<0 applies, or when additionally dp/dt<S<0 applies. The threshold value S can be ascertained empirically, for example. A threshold value has the advantage that minor pressure fluctuations, for example due to vortex effects, friction losses and/or measuring inaccuracies, do not necessarily result in an immediate shutdown of the feeding of the molten metal. The threshold value should, on the one hand, be selected so that minor pressure fluctuations do not result in a shutdown, but, on the other hand, it is to be established by way of the threshold value that the molten metal level inside the vessel is near the first end of the flow duct. The feeding of the molten metal can preferably be shut off when air penetrates into the first end of the flow duct, and before the air reaches the second end of the flow duct. In the pressure profile over time, this point in time, when air penetrates into the first end of the flow duct, is marked by a pressure drop. The pressure profile at this very point in time typically has a time derivative that, in absolute terms, is greater than 1 mbar/s. As a result, a threshold value can advantageously be, in absolute terms, at least 1 mbar/s, preferably at least 5 mbar/s, and particularly preferably at least 10 mbar/s. Typically occurring vortex effects or manual, brief interruptions in the feeding can be taken into consideration with the threshold value and be included in a threshold value ascertainment.
A deviation or tolerance of the shutdown is preferably no more than 4% of a fill weight of the vessel with molten metal. Particularly preferably, a deviation is no more than 2% of a fill weight of the vessel with molten metal.
A second pressure can be measured in a second location so as to identify measuring errors. The second measured pressure preferably correlates with a pressure in the vessel, with a pressure in the pneumatic unit for setting a pressure difference between an ambient pressure and a pressure in the vessel and/or with a pressure in the flow duct. For example, the second pressure can be compared to the first measured pressure for agreement or correlation.
In each case, at least two, and preferably at least three, consecutively measured pressures can be averaged. The time derivative dp/dt can then be ascertained based on the averaged pressures. In this way, the derived pressure curve can be smoothed, so that fluctuations and measured value outliers can be counteracted. In this way, the functional reliability of the evaluation can be increased. The control unit can preferably be configured and designed to average the measured values and/or to determine a pressure profile over time based on the averaged measured values.
The pressure profile over time can also be filtered with respect to the frequency thereof. For example, a bandpass filter, and in particular a bandpass filter having the frequencies 5 Hz and 25 Hz, can be used for this purpose. The amplitude of the filter output signal can be used as a shutdown criterion. The control unit can preferably be configured and designed to control a feeding of a molten metal based on the output signal of the bandpass filter.
So as to halt the feeding of the molten metal, the pressure difference between a pressure prevailing in the vessel and an ambient pressure prevailing outside thereof can be reduced, in particular as soon as the ascertained derivative of the pressure profile is negative and preferably, in absolute terms, is greater than the previously established threshold value. The control unit can be configured and designed to set this pressure difference and, in particular, to reduce it for halting the feeding of the molten metal.
The control unit can furthermore be designed and configured to determine the time profile over time p(t) from the measured pressure, to ascertain the time derivative of the pressure profile dp/dt, and to halt the feeding of the molten metal when the derivative of the pressure profile dp/dt is negative, and preferably when the derivative, in absolute terms, is greater than the previously established threshold value.
In the described melt transfer system, typically some melt remains in the vessel after the described emptying process. As a result, this residual melt may block, or even destroy, the flow duct after having cooled and solidified. The blocking of the first end of the flow duct can in particular be problematic during renewed heating of the solidified melt, since the flow duct, in particular in the form of a riser, can advantageously serve as a chimney when heating the described melt transfer system. It can therefore be an object of the invention to prevent this problem.
For this purpose, the melt transfer system can comprise an oblique positioning device for tilting the vessel. The vessel can be tilted by way of the oblique positioning device in such a way that the remaining melt at the bottom of a vessel inner side flows into a side facing away from the first end of the flow duct. The first end of the flow duct can thus be displaced upwardly with respect to a plane on which the melt transfer system is located. In this way, the remaining melt can expose the first end of the flow duct and solidify in the vessel. During renewed heating of the vessel interior space, for example by way of a gas burner, the flow duct, in particular in the form of a riser, can thus be used as a chimney. This may be advantageous, in particular, compared to electrically preheating approaches from the prior art, since the flow duct, or the riser, is likewise heated in the process. In this way, a solidification of melt in the flow duct, or in the riser, can be counteracted. Melt that has solidified in the flow duct, or in the riser, can lead, at least regionally, to clogging of the flow duct, or of the riser, during a feeding of the molten metal. It can thus be the object of the described melt transfer system to improve a molten metal transfer.
The oblique positioning device can comprise at least one base connected to the vessel in an articulated manner, and a vessel-side locking device for locking the base in a functional position. The base can be connected to the vessel directly or indirectly, for example via at least one component coupled to the vessel. The base can be brought from an idle position into a functional position, wherein the base can protrude over a vessel underside in the functional position. The melt transfer system can also comprise multiple oblique positioning devices. It may be particularly advantageous if at least two oblique positioning devices that are spaced apart from one another are present, which each comprise at least one base. In this way, the melt transfer system can, for example, be tilted in a statically determinate manner.
The vessel-side locking device can comprise a detent, clamping or snap-fit mechanism or a locking pin. Other locking mechanisms are, of course, also conceivable.
In one embodiment, the vessel can comprise a first flange including a first flange-side borehole. The base can include a first base-side borehole, which is aligned coaxially to the first flange-side borehole in the functional position. In this way, for example, the locking pin can be pushed through the first flange-side borehole and the first base-side borehole for locking the base in the functional position. The locking pin can accordingly be designed in such a way that a pin diameter corresponds to a diameter of the first flange-side borehole and the first base-side borehole. A diameter of the locking pin can, for example, be at least 10 mm, and preferably at least 15 mm. The locking pin, the base and/or the flange are preferably made of steel.
The flange can preferably be welded to the vessel. The flange can also be joined to the vessel in another manner, for example by way of a screw joint or a plug connection.
The base can include a second base-side borehole, which is aligned coaxially to the first flange-side borehole in the idle position. The locking pin can thus be pushed through the first flange-side borehole and the first base-side borehole for locking the base in the idle position.
The base can be pivotable from the idle position into the functional position, and vice versa. A pivoting can have the advantage that a defined movement option of the base is predefined, which is easy for an operator to comprehend and carry out. The base can furthermore be pivotably connected to the vessel in such a way that no loose individual parts can be lost. The base can, of course, also be designed to be unscrewed, folded out or extended, for example in a telescoping manner.
In one embodiment, the oblique positioning device can comprise a fastening pin that rotatably connects the base to the flange. A rotational axis can be defined along a fastening pin longitudinal direction, about which the base can be pivoted from the idle position into the functional position, and vice versa. The fastening pin can simply be pushed into the flange-side borehole or boreholes, or comprise a bearing, for example a ball bearing. The fastening pin can be rigidly connected to the flange, or rigidly connected to the base, or rotatably connected to the base and the flange.
In an advantageous embodiment, the oblique positioning device can comprise a second flange, which is preferably designed to correspond to the first flange. The base can then, in particular, be arranged between the two flanges. This can increase a stability of the oblique positioning device.
In one embodiment, the melt transfer system can comprise a supporting frame comprising a swivel joint unit. The vessel can be pivotably connected to the supporting frame by way of the swivel joint unit in such a way that the vessel can be tilted about a rotational axis of the swivel joint unit in relation to the supporting frame. In the tilted position, the vessel can be supported by the base locked in the functional position. This can have the advantage that the vessel can be tilted by the same angle substantially independently of an uneven floor on which the melt transfer system is located. The vessel can be tilted in relation to the supporting frame by way of the oblique positioning device by an angle of at least 1°, preferably at least 3°, and particularly preferably at least 5°. The vessel can be tilted in relation to the supporting frame by way of the oblique positioning unit by an angle of no more than 30°, preferably no more than 10°, and particularly preferably no more than 6°. In this way it can be ensured that the flow duct, in particular in the form of a riser, cannot be clogged and/or destroyed by cooling residual melt.
In one embodiment, the supporting frame can comprise a supporting frame-side locking device for locking the base in the functional position. Similarly to the vessel-side locking mechanism, this locking mechanism can, for example, be designed as a detent, clamping or snap-fit mechanism or, for example, comprise a further locking pin. It is also possible to use a combination of different locking mechanisms, both for the vessel-side and for the lower, supporting frame-side locking device. As a result of the supporting frame-side locking mechanism, the vessel can be transported in the tilted position. Furthermore, a more secure footing and safer transport can be ensured in the functional position.
The base can include a third borehole, which can be designed to receive a second locking pin in the functional position. The lower locking device can include at least one supporting frame-side borehole, which can be arranged coaxially with the third base-side borehole in the functional position. In this way, the second locking pin can be pushed into the third base-side borehole and the supporting frame-side borehole of the lower locking device for fastening the base to the lower supporting frame.
In one embodiment, the supporting frame can comprise at least one pair of, preferably box-shaped, fork pockets for receiving forklift truck tines. In this way, the melt transfer system can be transported in a simple manner. The melt transfer system can furthermore be raised in a simple manner. In the raised position, the oblique positioning device can be moved from an idle position into a functional position in a simple manner. In particular, the melt transfer system can, in this way, be brought by a single operator into a tilted position in a simple manner. The fork pockets can preferably be box-shaped, and in particular at least two boxes can be provided. It is also possible for a box comprising rails or a rib-like separation to be provided so as to guide the forklift tines during the insertion into the fork pockets. Particularly advantageously, it may be provided that the fork pockets are designed in such a way that a forklift truck can approach the melt transfer system from four sides and pick it up.
The melt transfer system can furthermore comprise an alignment device for setting a vessel inclination and/or a supporting frame inclination. This alignment device can preferably be provided in addition to an oblique positioning device. For example, the alignment device can comprise at least three threaded rods, which can each comprise feet that can be adjustable in a height, preferably independently of one another. In this way, the melt transfer system can be aligned on an uneven floor so that the melt transfer system can have a uniform melt level, for example, compared to the vessel inner side bottom during operation.
The vessel of the melt transfer system can be tilted or obliquely positioned as follows. Initially, the melt transfer system can be raised to such an extent that the base can be brought into a functional position. The melt transfer system can be raised at least 5 cm, and preferably at least 10 cm in the process. Furthermore, a raising of no more than 30 cm may be advantageous. So as to facilitate an operability for a user, the device, however, can also be raised considerably higher, so that the user, for example, does not have to bend down to bring the base into the functional position. In this way, ergonomical working can be enhanced. Thereupon, the base can be brought from an idle position into a functional position in such a way that the base protrudes over an underside of the vessel. The base can be locked in the functional position. Thereafter, the melt transfer system can be lowered. The raising and lowering of the melt transfer system can preferably be carried out by way of a forklift truck. Prior to lowering, the base is preferably locked in relation to the supporting frame by way of the supporting frame-side locking device.
In known systems for preheating transport vessels, the entire vessel cover has to be removed from the vessel for preheating. For example, a relatively heavy cover, corresponding to the vessel cover in terms of the size thereof, can then be placed on, the cover comprising an integrated burner. In other known systems, the preheating takes place by way of electrical heating elements. Both approaches are associated with a lot of effort.
It is the object of the system described here to preheat the transport vessel together with the vessel cover and with the preferably complete flow duct or riser, wherein the effort for setting up the heating is comparatively low. For this purpose, the vessel cover of the melt transfer system can include a heating opening, comprising a connecting flange surrounding the heating opening for flange-mounting a preheating device and for flange-mounting a heating opening cover, and a heating opening cover for closing the heating opening in an air-tight manner. So as to preheat the transport vessel and the flow duct or riser, hot gases are introduced through the heating opening into the vessel, wherein the hot gases are generated by a gas burner, for example. The hot gases are discharged through the flow duct or the riser into the surrounding area, and thus also preheat the flow duct or the riser. The heating opening cover can be detachably fastened to the vessel cover, for example by way of screws or clamps, and can close the heating opening in an air-tight manner. Such a heating opening has the advantage that a preheating device can be mounted on the vessel in a simple manner, and can then heat a melt solidified in the vessel and/or preheat a vessel interior space.
Moreover, it may be sufficient for preheating to remove the comparatively small heating opening cover, which is lightweight compared to the vessel cover, so as to heat the vessel interior space. A removal of the large vessel cover can thus be avoided.
The heating opening can be round, rectangular, or polygonal. The inner diameter or hydraulic diameter thereof (4*cross-sectional surface divided by the circumference) can be at least 4 cm, preferably at least 6 cm, and particularly preferably approximately 9 cm. It can maximally be half the inner diameter of the vessel opening, and preferably maximally 20 cm.
The heating opening can, for example, be maximally half as large as the filling opening. The heating opening can preferably be approximately ⅓ the size of the filling opening, and particularly preferably approximately ⅙ of the size of the filling opening.
The following numerical value information shall not be interpreted to be limiting, but only by way of example, and only show possible embodiments of the melt transfer system. The filling opening can have a diameter of at least 20 cm, and preferably at least 30 cm, and/or a diameter of no more than 100 cm, and preferably no more than 80 cm. The vessel cover can have a diameter of at least 50 cm, and preferably at least 70 cm, and/or a diameter of no more than 250 cm, and preferably no more than 175 cm.
The vessel cover, the filling opening cover and/or the heating opening cover can in particular comprise steel. Furthermore, the vessel cover, the filling opening cover and/or the heating opening cover can also comprise thermally insulating layers made of refractory materials, such as fiber mats and/or refractory concrete. The vessel cover, the filling opening cover and/or the heating opening cover can comprise the same or different materials. The heating opening cover can comprise a blind flange, for example, for closing the heating opening. The heating opening cover can be fastened to the vessel cover by way of clamps and/or screws. This has the advantage that the heating opening cover can be mounted to and be removed from the vessel cover in a simple manner.
In one embodiment, the connecting flange can project on a cover upper side in such a way that a flange plane is spaced apart from the cover upper side. A projecting flange can in particular facilitate a mounting of the burner on the flange. The flange structure can furthermore be better insulated.
The flange plane can form an angle with the cover upper side (angled flange-mounting plane). The angle can be formed in such a way that the imaginary extension of the axis of the flange-mounted burner strikes the surface of the solidified residual metal in the vessel. It can also be formed so as to strike the bottom of the vessel approximately in the center thereof. It can also be formed so as to have the maximum distance from the vessel walls at approximately half the height of the vessel (that is, alignment with the center of the vessel interior space).
The flange plane can form an angle with the cover upper side of at least 10°, preferably at least 20°, and particularly preferably at least 30°, and/or of no more than 90°, preferably no more than 80°, and particularly preferably no more than 70°. In one embodiment, the flange plane can also form an angle with the cover upper side of at least 40° or of at least 50°. An angled flange-mounting plane can have the advantage that a burner that is flange-mounted on the connecting flange can be aligned in the direction of a vessel interior space center, or in the direction of a vessel side, for example a region in which solidified residual melt is arranged.
In one embodiment, the heating opening cover can comprise a handle for better handling. This handle can, for example, be thermally insulated so that the cover can be operated by an operator even after the vessel interior space has been heated.
In one embodiment, the connecting flange can be designed in such a way that a corresponding flange of a preheating device, and in particular of a gas burner or of an electronic heating element, for preheating the vessel interior space can be flange-mounted on the flange by way of clamps or screws. This has the advantage that the preheating device can be mounted to and removed from the vessel cover in a simple manner.
The melt transfer system can comprise a burner cover that comprises a preheating device, preferably a gas burner, and a mounting flange that corresponds to the connecting flange of the heating opening.
Advantageous exemplary embodiments are shown in the figures. Only features of the different embodiments disclosed in the exemplary embodiments can be claimed combined with one another and individually.
Advantageous exemplary embodiments are shown in the figures. Only features of the different embodiments disclosed in the exemplary embodiments can be claimed combined with one another and individually.
In the drawings:
The melt transfer system 1 moreover comprises fork pockets 11 in which the forklift tines can engage. The fork pockets 11 are box-shaped and designed so as to be approachable from 4 sides. The melt transfer system furthermore comprises an oblique positioning device 12, comprising a base 12.2 and a supporting frame 12.1 including a swivel joint unit 12.1.1.
In areas II, IV and VI, negative derivatives dp/dt of the pressure profile p(t) arise due to the brief or longer-lasting pressure drops. In addition to the pressure profile 20,
Smoothing of the time derivative curve 21 can be advantageous for a functionally reliable evaluation of the pressure values, so that incorrect evaluation results due to pressure fluctuations can be avoided to the extent possible. When a simple comparison of pi and pi-1 is carried out, the profile of the time derivative oscillates. For a smoothing of the pressure gradient, it is advantageous to average the last three or more pressure readings, so that the measured values measured by the pressure sensor are filtered. The control unit 16 is configured and designed to carry out this averaging.
The more values are used for filtering, the smoother the profile of the time derivative becomes. A smoother profile, however, also causes the response time to become longer. The response time is the time that the control unit requires to identify the pressure drop.
The control unit can be designed to determine the filtered derivative as follows:
where
This profile is illustrated in
After the feeding of molten metal 17 has been shut off, residual molten metal 17 typically remains in the vessel 2. So as to prevent this, after solidifying, from clogging the first end 8.1 of the riser 8, the melt transfer system 1 is advantageously equipped with an oblique positioning device 12.
The application includes, among other things, the following aspects:
| Number | Date | Country | Kind |
|---|---|---|---|
| 18151512.3 | Jan 2018 | EP | regional |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2019/050698 | 1/11/2019 | WO | 00 |
