EP4669782A1

EP4669782A1 - DEVICE AND METHOD FOR MELTING REFINING

Info

Publication number: EP4669782A1
Application number: EP24706396.9A
Authority: EP
Inventors: Terje Haugen; John Olav Fagerlie; Eddy Steinar Dale; Ivar Løve Vebenstad
Original assignee: Norsk Hydro ASA
Current assignee: Norsk Hydro ASA
Priority date: 2023-02-20
Filing date: 2024-02-19
Publication date: 2025-12-31
Also published as: AU2024225936A1; KR20250153208A; WO2024175530A1; JP2026506830A; NO20230169A1; MX2025008896A; CN120457223A; NO348214B1

Abstract

A system and equipment for melt refining, in particular molten aluminium or aluminium alloy, including a container with an outer shell or casing and a thermally insulated interior cladding or wall construction, a removable lid provided on top of the container to keep the container sealed during operation, and suction means for generating an under-pressure in the container during operation, the container is fluidly connected with a metal flow in a metal supply launder, the container comprises at least one dividing wall extending from a bottom of the container and upwardly to a pre-set height level of the container interior height and dividing the container into at least a first chamber having an inlet opening for receiving molten metal from a metal supply launder section and at least a second chamber having an outlet opening being fluidly connected with a downstream launder section, the downstream launder section is provided with a removable start-up closure downstream the outlet opening, the equipment further including a removable bypass closure arranged between the inlet opening and the outlet opening to control the flow of molten metal, and optionally a metal level sensor monitoring the metal level in the launder section, wherein at least one removable filter media is arranged in the at least first chamber or the at least second chamber at a hight lower than the pre-set height level of the dividing wall, and at least one means for degassing and refining the melt is arranged in the other of the at least first chamber or the at least second chamber.

Description

APPARATUS AND METHOD FOR MELT REFINING

TECHNICAL FIELD

The present invention relates to an apparatus and equipment for refining molten metal, and a method for refining of molten metal. In particular the invention relates to an apparatus and equipment, as well as a method for degassing, refining and filtering molten aluminium metal and aluminium alloys.

BACKGROUND ART

It is generally known to remove small inclusions from molten metal such as molten aluminium by filtration. A typical material used for such filters is porous ceramic, commonly referred to as CFF (Ceramic Foam Filters). These CF (Ceramic Foam) filters are not easily wetted by molten metal and since such materials have relatively fine pores, considerable difficulties are encountered in initiating the flow of metal through the filter (priming the filter). It is therefore generally known to use deep filter boxes to generate sufficient metal head by gravitation to force the metal through the filter.

EP3253897 describes a filtration principle where under-pressure is applied for priming of filter media from the underside as an alternative to the traditional gravity principle.

EP1081240 describes purification of metal by degassing of metal with under-pressure. Commonly Argon can be used as process gas.

Although the traditional metal refining solutions provide good quality of the molten metal to be subsequently casted, there is a desire for an improved metal refining equipment and apparatus which provides a more sustainable solution, and at the same time provide excellent in-line refining of the melt to be casted.

SUMMARY

The present invention provides a solution that achieves the above desires and have further advantages. According to a first aspect, the present disclosure relates to a system/equipment for melt refining, in particular molten aluminium or aluminium alloy, the refining system/equipment includes a container with an outer shell or casing and a thermally insulated interior cladding or wall construction, a removable lid provided on top of the container to keep the container sealed during operation, and suction means for generating an under-pressure in the container during operation, the container is fluidly connected with a metal flow in a metal supply launder, the container comprises at least one dividing wall extending from a bottom of the container and upwardly to a pre-set height level of the container interior height and dividing the container into at least a first chamber having an inlet opening for receiving molten metal from a metal supply launder section and at least a second chamber having an outlet opening being fluidly connected with a downstream launder section, the downstream launder section is provided with a removable start-up closure downstream the outlet opening, the equipment further including a removable bypass closure arranged between the inlet opening and the outlet opening to control the flow of molten metal, and optionally a metal level sensor monitoring the metal level in the launder section, wherein at least one removable filter media is arranged in the at least first chamber or the at least second chamber at a hight lower than the pre-set height level of the dividing wall, and at least one means for degassing and refining the melt is arranged in the other of the at least first chamber or the at least second chamber.

The equipment may comprise more than one dividing walls dividing the container into one or more additional chamber(s), in addition to the first chamber and the second chamber, each of the one or more additional chamber(s) being provided with a removable filter media or a means for degassing and refining the melt.

In an embodiment, the means for degassing and refining the melt is arranged in the first chamber and the removable filter media is arranged in the second chamber.

In another embodiment, the removable filter media is arranged in the first chamber and the means for degassing and refining the melt is arranged in the second chamber.

The means for degassing and refining the melt may comprise an agitator, such as a mixer or a rotor, and a means for supply of process gas and optionally particulate material. Preferably, the means for degassing and refining the melt is a degassing rotor mounted in the bottom of the chamber. Preferably, the degassing rotor delivers the process gas to the melt for refining treatment.

The removable filter media may be a ceramic foam filter. The ceramic foam filter may have a porosity grade from 30 to 50 ppi.

The equipment may further comprise a metal level sensor monitoring the metal level in the launder section.

According to a second aspect, the present disclosure relates to a method for refining metal melt, in particular molten aluminium or aluminium alloy, by using the system/equipment for melt refining according to the first aspect, the method comprises the following steps: a) closing the removable start-up closure; b) providing molten metal in the launder supply system; c) generating an under-pressure in the container by the suction means, thereby raising level of molten metal in the at least first chamber and the at least second chamber until a pre-defined metal level in the container allowing the molten metal to flow across the at least one dividing wall; d) activating the means for degassing and refining; e) closing the removable bypass closure, and f) opening the removable start-up closure thereby flowing the molten metal via the at least first chamber and the at least second chamber to a downstream casting system,

The sequence of steps c) and d) is not mandatory and may be performed simultaneously, or partly simultaneously.

The method may comprise monitoring the metal level in the launder section by a metal level sensor.

The opening of the removable start-up closure may be performed gradually for regulating the metal flow downstream the melt refining equipment towards the casting system, thereby regulating the residence time for the molten metal in the at least first chamber and that at least second chamber adapted to the downstream casting process capacity. The method may comprise collecting exhaust gas and dust particles in a closed filter system.

The method may further comprise a step g) opening the removable bypass closure and adjusting the under-pressure by the end of the casting, thereby draining the at least first chamber and the at least second chamber.

According to a third aspect, the present disclosure relates to an apparatus for refining metal melt, in particular molten aluminium or aluminium alloy, the apparatus comprises a container with an outer shell or casing and a thermally insulated interior cladding or wall construction, a removable lid provided on top of the container to keep the container sealed during operation and suction means for generating an under-pressure in the container during operation, the container being configured to be fluidly connected with a metal flow in a metal supply launder, the container comprises at least one dividing wall extending from a bottom of the container and upwardly to a pre-set height level of the container interior height and dividing the container into at least a first chamber having an inlet opening configured to be fluidly connected with a metal supply launder section and at least a second chamber having an outlet opening configured to be fluidly connected with a downstream launder section, wherein at least one removable filter media is arranged in the at least first chamber or in the at least second chamber at a hight lower than the pre-set height level of the dividing wall, and at least one means for degassing and refining the melt is arranged in the other of the at least first chamber or the at least second chamber.

The apparatus may comprise more than one dividing wall(s) dividing the container into one or more additional chamber(s), in addition to the first chamber and the second chamber, each of the one or more additional chamber(s) being provided with a removable filter media or a means for degassing and refining the melt.

In another embodiment, the removable filter media is arranged in the first chamber and the means for degassing and refining the melt is arranged in the second chamber. The means for degassing and refining the melt may comprise an agitator, such as a mixer or a rotor, and a means for supply of process gas and optionally particulate material. Preferably, the means for degassing and refining the melt is a degassing rotor mounted in the bottom of the chamber. Preferably, the degassing rotor delivers the process gas to the melt for refining treatment.

According to a fourth aspect of the present disclosure, the apparatus according to the third aspect is used in-line between a melting furnace and a casting machine for refining, degassing and particle removal of molten aluminium or aluminium alloy.

Surprisingly, by combining the degassing and refining and filtration in a single refining apparatus and equipment, a lower height of molten metal above the degassing and refining chamber was possible, compared with traditional degassing and refinement equipment, while achieving excellent purified molten metal to be casted. A lower metal height may reduce the performance requirement of the suction means for maintaining a sufficient level of under-pressure in the container. Furthermore, the remaining metal volume when draining the refining apparatus can be reduced. Another advantage by the lower metal hight is that maintenance of the apparatus can be performed via the top closure, eliminating need for a side door for service and maintenance of the apparatus.

Another important advantage of the refining apparatus and equipment, and the method according to the present invention is the combination of degassing and refining technology and the filtration technology into one single unit, thereby obtaining the purity of filtrated and degassed metal in one step. The refining apparatus and equipment combining degassing and filtering provides a better space utilization (i.e. significant reduced footprint) compared with two or more separate treatment installations, which is favourable in narrow casting lines. The refining apparatus with combination of both filtering, degassing and refining, utilises common casing (container), refractory lining, under-pressure system, PLC/control system, heating system, dust filter, filter frame and launder system, in one single unit. By combining filtering, degassing and refining in one unit and utilizing common under-pressure system, PLC/control system, heating system, dust filter, filter frame and launder system less infrastructure equipment is needed, which again provides a much more sustainable solution compared with the traditional technology.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be further described in the following with reference to the non-limiting drawings where:

Fig. 1 illustrates a side view of an empty refining apparatus/equipment before start-up or after draining.

Fig. 2 illustrates a side view of the refining apparatus/equipment during filling sequence of the container with arrows for illustrating the metal flow. Dotted horizontal line illustrates target of metal level.

Fig. 3 illustrates a side view of the refining apparatus/equipment with arrows for illustrating the metal flow during steady state operation.

Fig. 4 illustrates a top view of a refining apparatus/equipment with arrows for illustrating the metal flow during steady state operation.

Fig. 5 illustrates a side view of the refining apparatus during draining sequence of container with arrows for illustrating the metal flow.

DETAILED DESCRIPTION

The present disclosure will now be described with reference to the accompanying drawings, in which preferred example embodiments of the disclosure are shown. The disclosure may, however, be embodied in other forms and the invention should not be construed as limited to the herein disclosed embodiments and illustrating drawings. The disclosed embodiments are provided to fully convey the scope of the disclosure to the skilled person.

In the present disclosure, the description of the refining apparatus also applies to the corresponding constructional elements of the refining equipment, and vice versa. Therefore, a description of the refining apparatus should be understood to also describe the refining equipment, unless otherwise indicated. Correspondingly, a description of the refining equipment should be understood to also describe the refining apparatus, unless otherwise indicated.

In the present context, the container may also be denoted as a casing, filter box or simply box, which should be understood to have the same meaning unless other stated.

In the present application, the terms “removeable start-up closure” and “removable bypass closure” are to be understood as closure means which are able to stop and/or regulating the flow of molten metal in the lauder system. The closure may be a barrier or dam which can be lifted and lowered to regulate or stop the flow of metal. Thus, in the present disclosure the term “closure” may also be denoted “dam” which are intended to refer to the same structural elements.

In an embodiment of the refining equipment and apparatus as illustrated in Fig. 1 (see also Fig. 4) the refining apparatus includes a container 13, which may have a general box construction with four walls, a bottom (floor) and top. The container may be provided with an outer shell or casing, which can be made of metal or composite material, and an inner thermally insulated interior cladding or wall construction. The inner thermally insulated interior cladding or wall construction can be made of heat resistant insulation and refractory material (not shown in drawings). A removable lid 7 is provided on the top of the container 13, and is configured to keep the container sealed (air tight) during operation. A suction means 11 (also denoted ejector herein) is arranged in the upper part of the container for generating an under-pressure in the container during start-up and operation. A dust filter is arranged on the outside of the container, for filtering the exhaust and any particulates ejected with the process gas.

The container 13 illustrated in the drawings comprises a dividing wall 4 extending from the floor to a pre-set hight which is lower than the interior hight of the container. The dividing wall 4 divides the container into two chambers; a first chamber A and a second chamber B. The container has an inlet opening A’ for receiving metal from a metal supply launder 1 to the first chamber A, and the second chamber B is provided with an outlet opening B’ to which purified metal can be delivered to a launder T downstream the refining apparatus. A degassing and refining means 3, in the drawings represented by a degassing rotor, is arranged in the first chamber A and a filter media 5 is mounted the second chamber B. It should be noted that the filter media 5 may be placed in the first chamber A and the degassing and refinement means 3 may be placed in the second chamber B.

In alternative embodiments, the refining equipment and apparatus may comprise more than one dividing walls 4, thereby providing additional refining chambers in the container 13 in addition to the two illustrated chambers A and B in the Figs. 1-5. The refining equipment and apparatus may therefore comprise two or more chambers comprising degassing and refining means, such as degassing rotors. The refining equipment and apparatus may also comprise two or more chambers comprising filter media 5. In a refining equipment and apparatus comprising more than the two illustrated chamber A and B, the additional chambers comprising degassing and refining means 3, or filter media 5 may be arranged in parallel or in series. It should be understood that in a parallel arrangement additional refining chambers may have inlet fluidly communicating with the launder section. Furthermore, additional refining chambers may have outlet fluidly communicating with the downstream lauder section. An advantage of having more than two treatment chambers in the refining equipment and apparatus is the possibility of refining larger volumes of molten metal in-line in the launder system, e.g. for large volume casting processes.

The container may be equipped with openings 10 in the lower part for removal of any dross generated by the refining of the molten metal. Each chamber may have a separate opening 10 for dross removal. The dross removal openings may be arranged on the opposite side of the container compared with the inlet opening A’ and the outlet opening B’ for easy access, however other locations are possible such as at the lower side walls of the container.

Below it is given a listing with reference signs of the main structural components in the refining apparatus and refining equipment, see Fig. 1-5:

A First chamber

B Second chamber

A’ Inlet opening

B’ Outlet opening

1 Launder section (upstream)

T Launder section (downstream)

2 Removable bypass closure

3 Degassing rotor 4 Dividing wall

5 Filter media

6 Removable start-up closure

7 Sealable lid

8 Metal level sensor

9 Hold-down tool

10 Dross channel opening

11 Ejector and dust filter

12 Refining apparatus

13 Container

14 Pre-defined metal level

An example of operating the refining equipment and apparatus will be described in the following, with reference to the appended drawings. The example is not to be construed as limiting for the present invention.

FILLING OPERATION

During filling of the refining equipment and apparatus, the liquid metal is stopped towards the start-up dam by placing the removable start-up closure 6 in a closing position (Fig. 2). The removable bypass closure 2 is placed in open position such that molten metal flows into the first chamber A and the second chamber B. The metal level sensor 8 monitors the metal level in launder section 1 to secure coverage of metal above the inlet opening A’ and the outlet opening B’.

Under-pressure generated inside the container is based on ejector principle, by ejector 11, and with sealing gasket in the lid 7. With a vacuum sealed box (container) the level of liquid metal will gradually elevate inside the container, due to metal passing through inlet opening A’ and outlet opening B’ (see arrows in Fig 2), forcing the metal through the filter media 5 from the bottom and up, and continue to rise until a pre-defined metal level 14 is achieved inside the container 13. By forcing the metal upwards through the filter media the filter is primed before the steady-state flow of the molten metal via the refining apparatus and above the dividing wall 4. Due to the bottom- up priming a lower height of metal above the filter medium is needed to force the molten metal through the filter, compared with priming the filter media by flowing the molten metal from above using only gravitational forces. Priming force will vary due to the different filter media coarseness. A hold-down tool 9 is preventing the filter media 5 to float during the priming stage. Arrows in fig. 2. illustrates the metal flow direction during metal filling and filter priming.

The degassing rotor 3 will start the degassing and refining process of the liquid metal when reaching a defined under-pressure and/or metal level inside the container, creating small bubbles and microbubbles of the supplied process gas. The removable bypass closure 2 will close when metal level reaches the target for normal operation level, herein illustrated by dotted line 14, forcing the metal to enter the first chamber inlet A’, ascend upwards, above the dividing wall 4, through the filter media 5 and exit the second chamber via outlet B’ to the downstream launder section T.

The start-up dam 6 can be gradually opened for regulating the metal flow downstream towards the casting system. The residence time for the metal inside the refining apparatus 12 (metal throughput), may be determined or regulated by the downstream casting process capacity i.e. metal flow rate (ton/hour).

Metal level height (i.e. under-pressure) is calculated based on the formula: dP = -rgh where; dP differential pressure between metal surface inside the container versus metal surface outside in the launder. density of liquid metal (such as Aluminium) acceleration of gravity metal height in container compared to metal level in launder

STEADY STATE OPERATION

Arrows in Fig. 3 and 4 illustrates the metal flow direction during steady state operation of the refining apparatus and equipment 12. In the example, the inlet chamber A is applied for degassing and refining and the outlet chamber B is applied for filtering of the liquid aluminium. It should be understood that the order can be reversed. A connected launder section 1 to the refining apparatus 12 guides the metal towards the closed bypass dam 2, forcing the liquid metal to enter the inlet opening A’ into the first chamber A, wherein a spinning degassing rotor 3 is supplying process gas to the melt. Exhaust gas and dust can be collected in a closed filter system outside the container. The dust filter system is integrated with the suction means 11 (ejector) which maintains the under-pressure in the container.

The under-pressure created by the ejector maintains the metal inside the container at an elevated level such that the liquid metal is forced, due to the direction of metal flow, to pass above the dividing wall 4, separating the degassing and refining chamber and the filtering chamber, and further through the filter media 5 kept in position with a hold-down tool 9.

The liquid metal leaves the container through the outlet chamber opening B’.

The metal level sensor 8 is monitoring the metal level in the launder inlet position. An operator panel with HMI (Human Machine Interface) screen close to the unit can be used for manual operation of dams (closures), lid, and rotor, and for monitoring the system during operation. Operation time may vary due to the casting system downstream the refining apparatus. The metal level sensor 8 and the suction means 11 for maintaining the under-pressure are controlled during the steady state operation to regulate and optimize the treatment time of the molten metal in the refining apparatus in accordance with the capacity of the downstream casting process.

DRAINING

By the end of the casting process the bypass closure 2 opens to allow metal to be drain from both chambers towards the launder and casting system. By this the refining apparatus will be automatically drained at the end of the operation sequence. Metal drainage is controlled through the metal level sensor 8 and by regulating the under-pressure inside the container. Arrows in Fig. 5 illustrates the metal flow direction during the draining sequence.

After a complete draining, and empty refining apparatus (container), the chambers can be cleaned from the top side (with opened lid 7) and/or through the dross channel openings (10). The filter media 5 including the hold-down tool 9 can be lifted out together, e.g. by using a crane, and the equipment can be prepared for next casting operation.

Claims

1. Equipment (12) for melt refining, in particular molten aluminium or aluminium alloy, including a container (13) with an outer shell or casing and a thermally insulated interior cladding or wall construction, a removable lid (7) provided on top of the container (13) to keep the container sealed during operation, and suction means (11) for generating an under-pressure in the container during operation, the container (13) being fluidly connected with a metal flow in a metal supply launder (1 , T), the container (13) comprises at least one dividing wall (4) extending from a bottom of the container (13) and upwardly to a pre-set height level of the container interior height and dividing the container (13) into at least a first chamber (A) having an inlet opening (A’) for receiving molten metal from a metal supply launder section (1) and at least a second chamber (B) having an outlet opening (B’) being fluidly connected with a downstream launder section (T), the downstream launder section (T) is provided with a removable start-up closure (6) downstream the outlet opening (B’), the equipment (12) further including a removable bypass closure (2) arranged between the inlet opening (A’) and the outlet opening (B’) to control the flow of molten metal, and optionally a metal level sensor (8) monitoring the metal level in the launder section (1), wherein at least one removable filter media (5) is arranged in the at least first chamber (A) or the at least second chamber (B) at a hight lower than the pre-set height level of the dividing wall (4), and at least one means for degassing and refining (3) the melt is arranged in the other of the at least first chamber (A) or the at least second chamber (B).

2. Equipment (12) for melt refining, according to claim 1, comprising more than one dividing wall(s) (4) dividing the container (13) into one or more additional chamber(s), in addition to the first chamber (A) and the second chamber (B), each of the one or more additional chamber(s) being provided with a removable filter media (5) or a means for degassing and refining (3) the melt.

3. Equipment (12) for melt refining, according to any one of claims 1-2, wherein the means for degassing and refining (3) the melt is arranged in the first chamber (A) and the filter media (5) is arranged in the second chamber (B).

4. Equipment (12) for melt refining, according to any one of claims 1-2, wherein the filter media (5) is arranged in the first chamber (A) and the means for degassing and refining (3) the melt is arranged in the second chamber (B).

5. Equipment (12) for melt refining, according to any one of claims 1-4, where the means for degassing and refining (3) the melt is a degassing mixer or degassing rotor, and a supply of processing gas, and optionally means for supply of particulate material.

6. Equipment (12) for melt refining, according to claim 5, wherein the means for degassing and refining (3) the melt is a degassing rotor (3) which supplies the processing gas to the melt for degassing and refinement.

7. Equipment (12) for melt refining, according to any one of claims 1-6, wherein the filter media (5) is a ceramic foam filter having a porosity grade from 30 to 50 ppi.

8. A method for refining metal melt, in particular molten aluminium or aluminium alloy, by using the equipment (12) for melt refining according to any of the claims 1-7, the method comprises the following steps: a) closing the removable start-up closure (6); b) providing molten metal in the launder supply (1) system; c) generating an under-pressure in the container (13) by the suction means (11), thereby raising level of the molten metal in the at least first chamber (A) and the at least second chamber (B) until a pre-defined metal level (14) in the container (13) allowing the molten metal to flow across the at least one dividing wall (4); d) activating the means for degassing and refining (3); e) closing the removable bypass closure (2), and f) opening the removable start-up closure (6) thereby flowing the molten metal via the at least first chamber (A) and the at least second chamber (B) to a casting system.

9 A method for metal melt refining, according to claim 8, comprising monitoring the metal level in the launder section (1) by metal level sensor (8).

10. A method for metal melt refining, according to claims 8 or 9, comprising opening the removable start-up closure (6) gradually for regulating the metal flow downstream the melt refining equipment (12) towards the casting system, thereby regulating the residence time for the molten metal in the at least first chamber (A) and that at least second chamber (B) adapted to the downstream casting process capacity.

11. A method for metal melt refining, according to any one of claims 8-10, comprising collecting exhaust gas and dust particles in a closed filter system.

12. An apparatus (12) for refining metal melt, in particular molten aluminium or aluminium alloy, the apparatus comprises a container (13) with an outer shell or casing and a thermally insulated interior cladding or wall construction, a removable lid (7) provided on top of the container (13) to keep the container sealed during operation and suction means (11) for generating an under-pressure in the container during operation, the container (13) being configured to be fluidly connected with a metal flow in a metal supply launder (1,1’), the container (13) comprises at least one dividing wall (4) extending from a bottom of the container and upwardly to a pre-set height level of the container interior height and dividing the container into at least a first chamber (A) having an inlet opening (A’) configured to be fluidly connected with a metal supply launder section (1) and at least a second chamber (B) having an outlet opening (B’) configured to be fluidly connected with a downstream launder section (1’), wherein at least one removable filter media (5) is arranged in the at least first chamber (A) or the at least second chamber (B) at a hight lower than the pre-set height level of the dividing wall (4), and at least one means (3) for degassing and refining the melt is arranged in the other of the at least first chamber (A) or the at least second chamber (B).

13. The apparatus according to claim 12, comprising more than one dividing wall(s) (4) dividing the container (13) into one or more additional chamber(s), in addition to the first chamber (A) and the second chamber (B), each of the one or more additional chamber(s) being provided with a removable filter media (5) or a means (3) for degassing and refining the melt.

14. The apparatus according to claim 12 or 13, wherein the means (3) for degassing and refining the melt is a degassing mixer or degassing rotor, and a supply of processing gas, and optionally means for supply of particulate material.

15. The apparatus according to claim 14, wherein the means (3) for degassing and refining the melt is a degassing rotor mounted in the bottom of a refining chamber, the degassing rotor supplies the processing gas to the melt for degassing and refining treatment.

16. The apparatus according to any one of claims 12-15, where the removable filter media

(5) is a ceramic foam filter, having a porosity grade from 30 to 50 ppi.

17. Use of the apparatus according to any one of claims 12-16, in-line between a melting furnace and a casting machine for refining, degassing and particle removal of molten aluminium or aluminium alloy.