WO2004102096A1

WO2004102096A1 - Improvements in and relating to pumping

Info

Publication number: WO2004102096A1
Application number: PCT/GB2004/002124
Authority: WO
Inventors: Alan Michael Peel; Roger Howitt
Original assignee: Emp Technologies Limited
Priority date: 2003-05-16
Filing date: 2004-05-17
Publication date: 2004-11-25
Also published as: GB0311282D0; CA2526095A1; US20070140868A1; EP1631782A1

Abstract

A pump and a method of moving molten metal is provided in which a tube open at one end and closed at the other end cooperates with a secondary tube received within it, open at both ends, to pump metal from the open end of the tube down a space between the tube and secondary tube to the closed end of the tube and then return the metal up the centre of the secondary tube. A simpler way of providing circulation of molten metal is provided.

Description

IMPROVEMENTS IN AND RELATING TO PUMPING

This invention concerns improvements in and relating to pumping, particularly of molten metal.

A variety of prior art systems for pumping or otherwise moving molten metal from one location to another exist. These systems are based around a layout which includes a conduit leading into the pump from one side, the pumping location and a further conduit leading away from the pump on another side. The conduit and further conduit are separate from one another and separately connected to the location or locations from which the pump receives the metal to be pumped and to which the pump pumps the metal.

Such systems take up significant space and require two sets of appropriate connections and conduits.

The present invention has amongst its aims to provide an alternative molten metal mover. The present invention has amongst its aims to provide a pump for molten metal which requires less space to operate and/or requires less connections to operate.

According to a first aspect of the invention we provide a pump for molten metal, the pump comprising a tube, the tube being open at one end and closed at the other end, one or more side walls extending between the open and closed ends, an electrical conductor being wrapped around the tube, a secondary tube being provided within the tube, the secondary tube having a through aperture extending from a first end to a second end and being spaced from at least a part of the side wall of the tube and at least a part of the closed end of the tube.

The internal profile of the tube may be configured to promote flow into the tube at the periphery of the tube and/or to promote flow out of the tube at the centre of the tube, preferably at the same time.

According to a second aspect of the invention we provide a pump for molten metal, the pump comprising a tube, the tube being open at one end and closed at the other end, one or more side walls extending between the open and closed ends, an electrical conductor being wrapped around the tube. The internal profile of the tube may be configured to promote flow into the tube at the periphery of the tube and/or to promote flow out of the tube at the centre of the tube, preferably at the same time.

Preferably a secondary tube is provided within the tube. The secondary tube may have a through aperture extending from a first end to a second end. The secondary tube may be spaced from at least a part of the side wall of the tube and at least a part of the closed end of the tube.

The first and/or second aspects may further include the following features, options or possibilities.

The tube may be of refractory, for instance silicon carbide. The tube may extend along an axis. The tube may be of circular cross-section. Preferably the tube is of constant cross-section between the open end and the start of the closed end.

The open end of the tube maybe of circular cross-section, preferably perpendicular to its axis. The open end of the tube maybe connected to a vessel, for instance a furnace, holding furnace or the like. A mounting element provided around at least a part of the open end may be used to mount the pump on the vessel. The open end of the tube may abut a part of the vessel, for instance a refractory lining. The open end of the tube may have a diameter of between 10 to 50cm.

The closed end of the tube may be formed by a tapering of the side walls and/or cross-sectional shape of the tube. The closed end maybe formed of a series of circular cross- sections of decreasing diameter. The closed end of the tube maybe dome shaped, particularly a dome in which the internal profile of the dome is exposed to the inside of the tube. The closed end of the tube may initially dome inwards, and preferably has a middle portion which extends back towards the open end of the tube. The middle portion may be dome shaped, particularly a dome in which the external profile of the dome is exposed to the outside of the tube.

Preferably the tube has a single side wall.

The electrical conductor is preferably wrapped around the tube in a single coil. The electrical conductor may be spaced from the tube, for instance by an insulator and/or magnetic field enhancing material. The electrical conductor may be clamped in position, preferably relative to the tube. The clamping may be provided by a framework which encloses the tube and conductor. Locations for mounting the pump on a vessel may also be provided on the framework.

Preferably connections are provided for attaching the electrical conductor to a power supply.

The secondary tube may be of refractory material, for instance silicon carbide. The secondary tube may extend along an axis, preferably the same axis as the tube. The secondary tube may be of circular cross-section. Preferably the secondary tube is of constant cross- section between its open ends.

The first and or second open ends of the secondary tube maybe of circular cross- section, preferably perpendicular to its axis. The first open end of the tube may be in fluid connection with a vessel, for instance a furnace, holding furnace or the like, and particularly the same vessel as the tube is in fluid location with. Preferably both the open end of the tube and the first open end of the secondary tube are in fluid connection with the vessel through a single opening in the vessel. The first and/or second open ends of the secondary tube may have a diameter of between 5 to 25cm. Preferably the first and/or second open ends of the secondary tube have a diameter half the diameter of the tube. Preferably the open end of the tube has a cross-sectional area which is between 3 and 5 times the cross-sectional area of the first and/or second open ends of the secondary tube.

Preferably the secondary tube has a central axis and ideally a central axis which corresponds with the central axis of the tube. Preferably the first end of the secondary tube is flush with or recessed relative to the open end of the tube.

Preferably the through aperture is of circular cross-section. Preferably the through aperture is of consistent cross-section throughout. Preferably the through aperture extends from proximate the open end of the tube to proximate the closed end of the tube. The through aperture may start within 5 to 30cm of the closest part of the closed end of the tube to it. The through aperture may extend to or within 10cm of a plane defined by the end surface of the open end of the tube.

The secondary tube may be spaced from the tube by one or more spanning portions. The one or more spanning portions may span the gap between the outside of the secondary tube and the inside of the tube. Preferably at least three spanning portions are provided. Preferably the spanning portions are evenly spaced around the secondary tube. The spanning portions may be separate from one another and/or separate from the tube and secondary tube or may be an integral part of the tube or are preferably an integral part of the secondary tube. The spanning portions may be provided along part of the length of the tube and/or secondary tube. The spanning portions may be provided for between 50% and 90% of the length of the secondary tube. The spanning portions may have an outer surface at least a part of which has a profile configured to match the internal profile of at least a part of the tube. The part may have a profile configured to match the side wall of the tube. The part may have a profile configured to match at least a part of the closed end of the tube. The spanning portions may be in the form of pillars provided on the secondary tube.

Preferably the secondary tube is spaced from the tube at all locations other than those of the spanning portions. Preferably the spacing defines one or more passageways between the inside of the tube and the outside of the secondary tube. A passageway may be defined between each pair of spanning portions. Preferably the secondary tube is spaced from the tube equally in all radial directions. The spacing between the side of the secondary tube and the side of the tube maybe between 15cm and 50cm. Preferably the second end of the secondary tube is spaced from the closed end of the tube in all directions. The second end of the secondary tube may have a spacing of between 5cm and 30cm relative to the closed end of the tube.

According to a third aspect of the invention we provide a method of moving molten metal, the method comprising providing a pump in fluid communication with a volume of molten metal, the pump comprising a tube, the tube being open at one end to the molten metal and closed at the other end, one or more side walls extending between the open and closed ends of the tube; passing an electric current through a conductor wrapped around the tube, the electromagnetic field produced causing molten metal to flow into the tube at the periphery of the tube and to flow out of the tube at the centre of the tube.

The internal profile of the tube may be configured to promote the flow into the tube at the periphery of the tube and/or to promote the flow out of the tube at the centre of the tube, preferably at the same time.

Preferably the method includes providing a secondary tube within the tube. Preferably the secondary tube separates the flow into and flow out of the tube and/or assists in the promotion of the stated flow. Preferably the molten metal flows into the tube along one or more spaces defined between the inside of the tube and outside of the inner tube. Preferably the molten metal flows out of the tube through the secondary tube. Preferably the molten metal flows in a first direction into the tube and out of the tube in a second direction. Preferably the first direction and second direction are the opposite of one another. Preferably the molten metal under goes a change in direction at or near the closed end of the tube. Preferably the change in direction is caused by the closed end of the tube. Preferably the closed end of the tube is configured to promote the change of direction.

Preferably the flow velocity within the secondary tube is higher than the flow velocity in the passageway between the tube and secondary tube.

Preferably the method includes introducing the flow from the secondary tube into a vessel to which the pump is attached, preferably the same vessel as the metal is received from. The flow may be used to promote circulation within the vessel and/or evening out of temperature and/or evening out of composition within the vessel.

Various embodiments of the invention will now described, by way of example only, and with reference to the accompanying drawings in which: -

Figure 1 illustrates a prior art pumping system for circulating metal within a furnace;

Figure 2 illustrates in cross-section an embodiment of a pump according to the present invention;

Figure 3 illustrates an end view of the pump of Figure 2;

Figure 4 shows the velocity profile across a conduit through which material is being electromagnetically pumped; and

Figure 5 illustrates a pumping system for circulating metal within a furnace incorporating the pump of Figure 2.

In a variety of circumstances it is desirable to cause flow of metal within a furnace or the like. The flow, for instance, improves the temperature and chemical homogeneity of the metal.

In prior art systems, the flow is usually generated by the type of configuration illustrated in Figure 1 in plan view. The furnace 1 contains a volume of molten metal 3. An aperture 5 is provided through the refractory 7 lining the wall 9 of the furnace 1. The aperture 5 leads to a conduit 11 which is also lined with refractory 13. A flange 15 on the furnace wall 9 opposes a flange 17 on the conduit 11 and allows the two to be connected. A flange 19 at the other end of the conduit 11 is similarly connected to a flange 21 on the pump 23. On the other side of the pump 23, a further flange 25 is used to connect the pump 23 to the outlet conduit 27 via its flange 29. Finally the flange 31 on the other end of the conduit 27 connects to flange 33 on the wall 9 of the furnace 1 to complete the circuit. To cause flow in the furnace 1, metal is pumped out of the pump 23 into conduit 27 and hence into the furnace 1, whilst metal flows from the furnace 1 via the conduit 11 to replace it. The speed of circulation through the pumping system causes flow and hence disturbance within the furnace 1.

A significant problem with such a system is the amount of floor space it occupies due to the need for different inlet and outlet connections and the respective limitations imposed by the inlet and outlets from the pump. Another significant problem arises with the number of connections which must be provided and maintained between the junctions of the various components.

In Figure 2, an embodiment of a pump according to the present invention is provided. This pump 100 includes within it a refractory tube 102, for instance of silicon carbide, with an open end 104 and closed end 106. The tube 102 has a circular cross-section along most of its length so as to define a cylindrical portion 108. Towards the closed end 106 the side wall 110 curves inwards so as to form a dome like structure for the end 106.

Within the refractory tube 102 is a secondary refractory tube 112, potentially of silicon carbide. The secondary refractory tube 112 is also open at the end 114 at which the tube 102 is open, as well as being open at the end 116 at which the tube 102 is closed. The open end 114 of the secondary refractory tube 112 ends at the same plane 118 as the end 104 of the tube 102. The other open end 116 of the secondary tube refractory 112 is spaced from the end 106 of the tube 102 so as to define a space 120. The position of the secondary tube 112 within the tube 102 is maintained by three radial pillars 122a, 122b, 122c which extend outward from the tube 112. The radial extent of the pillars 122a, b, c is such that they contact the wall 110 of the tube 102. The surfaces 124 of the pillars which define their radial extent are curved so as to match the curvature of the side wall 110 of the tube 102. The part 126 of these surfaces 124 nearest the end 116 of the secondary tube 112 curves inward so as to match the start of the domed end 106 of the tube 102.

With the secondary tube 112 positioned within the tube 102, and referring to Figure 3, three passageways 128 between the tube 102, secondary tube 112 and a pair of the three pillars, 122a, 122b; 122b, 122c; 122c, 122a are defined. These extend continuously from outside 134 the pump 100 to the space 120 between the ends 106 and 116 of the tube 102 and secondary tube 112 respectively. The through aperture 130 within the secondary tube 112 extends from space 120 to the outside 128 of the pump 100.

Around the refractory tube 102 a single wound coil 132 is provided. This is clamped in position relative to the tube 102 by a framework. The coil 132 forms the electromagnetic pump which is used to move the molten metal.

To date, electromagnetic pumps, as with other pumps, have been used to transport material along an inlet conduit on one side of the pump, through the pump conduit around which the coil is wound and then along a separate outlet conduit on the other side of the pump. Pumping substantially along an axis therefore occurs.

Within a conduit, Figure 4, the molten metal has a velocity profile which varies across the width of the conduit due to the force applied to it by the electromagnetic pump. Towards the edge of the conduit the velocity is at its highest, decreases towards the centre and is at its lowest at the centre. The profile is generally symmetrical.

This difference in velocity profile with position is harnessed in the present invention. By defining the outer passageways 128 and inner through aperture 130 in the correct proportion the average force applied by the electromagnetic field to the metal in the outer passageways 128 is significantly greater than the average force applied by the electromagnetic field in the through aperture 130. The net effect of these forces is that the metal flows from the outside 134 into the passageways 128 into the space 120 and back to the outside 134 along through aperture 130. The force on the metal in the outer passageways 128 is converted by the shape of the domed end 106 into a force in the opposing direction and this swamps the more limited electromagnetic force on the metal in the through aperture 130 and causes the flow of material in the described direction. The provision of the secondary tube 112 helps in establishing and maintaining this flow pattern, but some flow of this type may occurs even without such a tube, particularly once initiated. By using a further reduced width of through aperture compared with that needed to achieve the desired flow direction, the metal can even be caused to flow down the outside at low speed, but flow through the through aperture at much higher speed because of the reduced unit area the metal must flow through.

An implementation of this pump system into a furnace is shown in Figure 5. In this case, the pump system 500 is fitted to a side wall 502 of a furnace 504. The side wall 502 is lined with a refractory 506. The fitting is achieved using a single flange 508 on the wall 502 and single flange 510 on the pump system 500. No other connections are needed and as a consequence a simple system is achieved. Because the inlet and outlet conduits of the pump system 500 are provided entirely within the profile of the pump system 500 the floor space occupied is very low.

In operation, metal 512 in the furnace 504 is drawn into the outside passageways 514 passes down them, into space 516 and through the aperture 518 back to the furnace 504. The relative cross-sectional areas of the inlet and outlet passages are such that a high speed jet 520 of molten metal is sent back to the furnace 504. This causes significant flow, disturbance and hence desirable operation across a large part of the furnace 504. The pump system is particularly suited for use on holding furnaces and the like.

Because of its simple design and need for only a single connection through the furnace wall to the molten metal, the pump system is easy to instal on new equipment and to retro-fit to existing situations. The low floor plan occupied also makes it easy to incorporate around existing equipment.

Claims

CLAIMS:

1. A pump for molten metal, the pump comprising a tube, the tube being open at one end and closed at the other end, one or more side walls extending between the open and closed ends, an electrical conductor being wrapped around the tube, a secondary tube being provided within the tube, the secondary tube having a through aperture extending from a first end to a second end and being spaced from at least a part of the side wall of the tube and at least a part of the closed end of the tube.

2. A pump for molten metal, the pump comprising a tube, the tube being open at one end and closed at the other end, one or more side walls extending between the open and closed ends, an electrical conductor being wrapped around the tube.

3. A pump according to claim 2 in which the internal profile of the tube is configured to promote flow into the tube at the periphery of the tube and/or to promote flow out of the tube at the centre of the tube, preferably at the same time.

4. A pump according to claim 2 or claim 3 in which a secondary tube is provided within the tube, the secondary tube has a through aperture extending from a first end to a second end and the secondary tube is spaced from at least a part of the side wall of the tube and at least a part of the closed end of the tube.

5. A pump according to any preceding claim in which the tube is of constant cross- section between the open end and the start of the closed end.

6. A pump according to any preceding claim in which the closed end of the tube is formed by a tapering of the side walls and/or cross-sectional shape of the tube.

7. A pump according to any preceding claim in which the closed end of the tube is dome shaped.

8. A pump according to any preceding claim in which the closed end of the tube is initially dome inwards and has a middle portion which extends back towards the open end of the tube.

9. A pump according to any preceding claim in which the secondary tube extends along the same axis as the tube.

10. A pump according to any preceding claim in which the secondary tube is of constant cross-section between its open ends.

11. A pump according to any preceding claim in which both the open end of the tube and the first open end of the secondary tube are in fluid connection with the vessel through a single opening in the vessel.

12. A pump according to any preceding claim in which the open end of the tube has a cross-sectional area which is between 3 and 5 times the cross-sectional area of the first and/or second open ends of the secondary tube.

13. A pump according to any preceding claim in which the through aperture of the secondary tube is of consistent cross-section throughout.

14. A pump according to any preceding claim in which the secondary tube is spaced from the tube by one or more spanning portions between the outside of the secondary tube and the inside of the tube.

15. A pump according to claim 14 in which the spanning portions have an outer surface at least a part of which has a profile configured to match the internal profile of at least a part of the tube. The part may have a profile configured to match the side wall of the tube.

16. A pump according to claim 14 or claim 15 in which the spanning portions are in the form of pillars provided on the secondary tube.

17. A pump according to any preceding claim in which the spacing defines one or more passageways between the inside of the tube and the outside of the secondary tube.

18. A pump according to any preceding claim in which the secondary tube is spaced from the tube equally in all radial directions.

19. A pump according to any preceding claim in which the second end of the secondary tube has a spacing of between 5cm and 30cm relative to the closed end of the tube.

20. A method of moving molten metal, the method comprising: providing a pump in fluid communication with a volume of molten metal, the pump comprising a tube, the tube being open at one end to the molten metal and closed at the other end, one or more side walls extending between the open and closed ends of the tube; passing an electric current through a conductor wrapped around the tube, the electromagnetic field produced causing molten metal to flow into the tube at the periphery of the tube and to flow out of the tube at the centre of the tube.

21. A method according to claim 20 in which the internal profile of the tube is configured to promote the flow into the tube at the periphery of the tube and or to promote the flow out of the tube at the centre of the tube.

22. A method according to claim 20 or claim 21 in which the method includes providing a secondary tube within the tube, the secondary tube separates the flow into and flow out of the tube and/or assists in the promotion of the stated flow.

23. A method according to any of claims 20 to claim 22 in which the molten metal flows into the tube along one or more spaces defined between the inside of the tube and outside of the inner tube and / or the molten metal flows out of the tube through the secondary tube.

24. A method according to any of claims 20 to 23 in which the molten metal under goes a change in direction at or near the closed end of the tube.

25. A method according to any of claims 20 to 24 in which the flow velocity within the secondary tube is higher than the flow velocity in the passageway between the tube and secondary tube.