DROSS HANDLING METHODS AND APPARATUS

Abstract

A compressing element, devices for using such a compressing element and methods of use are provided, in which the compressing element has: a upper surface provided with an inlet and an outlet; a lower surface; an at least partially hollow interior provided between the upper surface and the lower surface, the hollow interior being connected to the inlet and the outlet; the hollow interior being provided with: one or more fluid flow constraining surfaces provided by one or more walls of the follow interior; and one or more fluid flow control elements provided in the hollow interior, the one or more fluid flow control elements being additional to the one or more fluid flow constraining surfaces provided by the one or more walls of the hollow interior. The arrangement of inlet, outlet, fluid flow constraining surfaces and fluid control elements provides for improved cooling of the compressing element, for instance when used to press molten metal processing by-products to extract molten metal.

Claims

1-14. (canceled)

15. A device for handling a molten metal processing by-product, the device comprising a metal from by-product separator including: an enclosure, in use, the enclosure receiving a container unit containing metal and by-product to be separated; a compressing element, in use, the compressing element compressing by-product in the container unit; an actuator connected to the compressing element; wherein the compressing element includes: an upper surface provided with an inlet and an outlet; a lower surface; an at least partially hollow interior provided between the upper surface and the lower surface, the hollow interior being connected to the inlet and the outlet; the hollow interior being provided with: one or more fluid flow constraining surfaces provided by one or more walls of the hollow interior; and one or more fluid flow control elements provided in the hollow interior, the one or more fluid flow control elements being additional to the one or more fluid flow constraining surfaces provided by the one or more walls of the hollow interior.

16. (canceled)

17. A method of handling a molten metal processing by-product, the method including: providing a device comprising: an enclosure; a compressing element; and an actuator connected to the compressing element; wherein the compressing element includes: an upper surface provided with an inlet and an outlet; a lower surface; and an at least partially hollow interior provided between the upper surface and the lower surface, the hollow interior being connected to the inlet and the outlet; the hollow interior being provided with: one or more fluid flow constraining surfaces provided by one or more walls of the hollow interior; and one or more fluid flow control elements provided in the hollow interior, the one or more fluid flow control elements being additional to the one or more fluid flow constraining surfaces provided by the one or more walls of the hollow interior; providing metal and by-product to be separated in a container unit; providing the container unit in the enclosure; moving the compressing element to compress the by-product in the container unit; and; cooling the compressing element by providing a fluid flow into the inlet, along the one or more flow constraining surfaces and one or more flow control elements and out of the outlet.

18. (canceled)

19. The method of claim 17, wherein: the one or more fluid flow constraining surfaces provided by one or more walls of the hollow interior are those parts of the upper surface and lower surface that face the hollow interior, and the one or more flow constraining surfaces provide the bounds of the hollow interior through which there is fluid flow; or the one or more fluid flow control elements are or include one or more elements defining a surface in opposition to the inside surface of the lower surface of the compressing element.

20. The method of claim 17, wherein the one or more fluid flow control elements include one or more baffles, and the one or more baffles are provided at a constant separation from the inner surface of the lower surface of the compressing element or are provided within a limited range of separation values.

21. The method of claim 20, wherein the limited range of separation values is from 20 mm to 80 mm.

22. The method of claim 17, wherein the compressing element includes a gap between one side of the compressing element and the other side of the compressing element at one or both ends of the compressing element and/or one or more intermediate locations.

23. The method of claim 17, wherein the one or more fluid flow control elements include one or more ribs or other projections, the one or more fluid flow control elements extending in a radial direction relative to the junction of the inlet with the hollow interior and/or the junction of the outlet with the hollow interior.

24. The method of claim 17, wherein the one or more fluid flow control elements have different lengths, widths, heights, and/or profiles.

25. The method of claim 17, wherein the inlet is provided between the centre of the compressing element and the periphery of the compressing element, the inlet being provided between 40% and 60% of the way between the centre and periphery.

26. The method of claim 17, wherein the outlet is provided between the centre of the compressing element and the periphery of the compressing element, the outlet being provided between 40% and 60% of the way between the centre and periphery.

27. The method of claim 17, wherein the compressing element includes: a press head for molten metal and/or molten metal processing by-products; wherein the lower surface includes one or more outwardly extending protrusions or surfaces.

28. The device of claim 15, wherein: the one or more fluid flow constraining surfaces provided by one or more walls of the hollow interior are those parts of the upper surface and lower surface that face the hollow interior, and the one or more flow constraining surfaces provide the bounds of the hollow interior through which there is fluid flow; or the one or more fluid flow control elements are or include one or more elements defining a surface in opposition to the inside surface of the lower surface of the compressing element.

29. The device of claim 15, wherein the one or more fluid flow control elements include one or more baffles, and the one or more baffles are provided at a constant separation from the inner surface of the lower surface of the compressing element or are provided within a limited range of separation values.

30. The device of claim 29, wherein the limited range of separation values is from 20 mm to 80 mm.

31. The device of claim 15, wherein the compressing element includes a gap between one side of the compressing element and the other side of the compressing element at one or both ends of the compressing element and/or one or more intermediate locations.

32. The device of claim 15, wherein the one or more fluid flow control elements include one or more ribs or other projections, the one or more fluid flow control elements extending in a radial direction relative to the junction of the inlet with the hollow interior and/or the junction of the outlet with the hollow interior.

33. The device of claim 15, wherein the one or more fluid flow control elements have different lengths, widths, heights, and/or profiles.

34. The device of claim 15, wherein the inlet is provided between the centre of the compressing element and the periphery of the compressing element, the inlet being provided between 40% and 60% of the way between the centre and periphery.

35. The device of claim 15, wherein the outlet is provided between the centre of the compressing element and the periphery of the compressing element, the outlet being provided between 40% and 60% of the way between the centre and periphery.

36. The device of claim 15, wherein the compressing element includes: a press head for molten metal and/or molten metal processing by-products; wherein the lower surface includes one or more outwardly extending protrusions or surfaces.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0134] Various embodiments of the invention will now be described, by way of example only, and with reference to the accompanying drawings in which:

[0135] FIG. 1 illustrates a first embodiment of a dross pressing head according to the present invention in plan view;

[0136] FIG. 2 illustrates the dross press head of FIG. 1 in a cross-sectional side view;

[0137] FIG. 3 illustrates the dross press head of FIG. 1 in cross-sectional plan view;

[0138] FIG. 4 illustrates a second embodiment of a dross pressing head according to the present invention in plan view;

[0139] FIG. 5 illustrates the dross press head of FIG. 4 in a cross-sectioned side view;

[0140] FIG. 6 illustrates the dross press head of FIG. 4 in cross-sectional side view;

[0141] FIG. 7a illustrates a dross press according to an embodiment of the invention;

[0142] FIG. 7b illustrates the dross press of FIG. 7 with the door closed;

[0143] FIG. 8a illustrates the dross press of FIGS. 7a and b with a first container unit loaded therein;

[0144] FIG. 8b illustrates the dross press of FIGS. 7a and b with a second different container unit loaded therein;

[0145] FIG. 9 illustrates the container unit with a closure element provided;

[0146] FIG. 10 is a sectional side view of the air flow through the enclosure in an embodiment of the invention; and

[0147] FIG. 11 is a sectional side view of the fluid flow through a compression element according to an embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0148] During primary and secondary operations which involve the generation of molten aluminium in a furnace, a slag or dross forms on the surface of the molten metal. The dross contains various waste components arising from the processing of the feed material. As well as waste components, the dross also includes significant aluminium content. As a result, when the aluminium stream and dross stream are separated following handling in the furnace, the dross stream is often fed to a dross press.

[0149] The dross press provides a container unit for the dross and a press head which is forced into the dross. Such an arrangement is shown in GB2314090. The mechanical force applied to the dross forces the still molten aluminium from the dross and out of the container unit and hence recovers that aluminium as further aluminium stream.

[0150] Existing designs face issues with the limits on the rate at which they cool the dross. The rate of cooling is important in obtaining high dross processing throughputs and in maximising the amount of useful metal recovered. The existing designs also have limits on the effectiveness and versatility of their control systems.

[0151] Cooling

[0152] In FIG. 1, a plan view from above of one embodiment of a press head 1 is provided. The press head 1 includes a substantially planar upper surface 3 and a central tube 5 at which location the actuator, not shown, for moving the press head up and down is provided. A pin 7 which passes through the tube 5 allows for the press head 1 is pivot relative to the actuator. Four braces 9 extend radially from the tube 5 to stiffen the press head 1. The press head 1 is provided with two loops 11 which can be used to lift the press head 1 during assembly, maintenance and the like.

[0153] Also provided on the upper surface 3 are mounts 13 for connection to air pipes, not shown. The air pipes are connected to the outside of the dross press. One of the mounts 13 provides an inlet 15 into the press head 1. The other mount 13 provides an outlet 17 from the press head 1. The inlet 15 and outlet 17 are used to flow cooling air through the inside of the press head 1.

[0154] Because the air is taken from the environments around the dross press, is fed through an air pipe to the press head 1, is fed out of the press head 1 along an air pipe and is returned to the environments of the dross press, that air does not come into contact with the air and dust inside the dross press. As a result, the risk of particulate material entering the press head 1 and interrupting flow with time is avoided. Additionally, the air leaving the press head 1 is not contaminated with dust and/or off gases from the dross press and so needs no or minimal treatment before it is return to the environments of the dross press. Any air flow from the environments into the dross press enclosure which comes into contact with such dust and off gases is handled separately through an outlet on the enclosure and appropriate dust and/or off gas treatment units.

[0155] In the cross-sectional views of FIG. 2 and FIG. 3, the air flow within the press head 1 is illustrated.

[0156] The press head 1 has a lower surface 19 which is dome shaped. The lower surface 19 has protrusions 21 which extend therefrom. In this embodiment these form a X shaped pair of protrusions 21 in the press head 1. Other protrusion configurations are possible. The press head 1 has a hollow 23 inside. The hollow 23 includes an upper surface 25, exemplified by an upper baffle which causes the air entering through inlet 15 to flow downwards towards inside of the wall 27 of the lower surface 19. The upper baffle 25 is provided by a 3 mm thick plate, and includes an inner surface 26. The lower surface 19 is the part of the press head 1 which receives the most heat in use and so the cooling air is hence directed towards the hottest location so as to have maximum effect.

[0157] The wall 27 has a series of baffles in the form of ribs 31 provided on its inner surface 38. The ribs 31 cause the air to radiate outward from the inlet 15 and so reach all parts of the wall 27 in the half of the press head 1. The ribs are 25 mm high off the inner surface 38 and have a 25 mm gap between their top surface and the bottom of the upper baffle 25. A baffle 33 divides the inlet half from the outlet half, but has openings 35 at either end to allow air flow into the outlet half. Further baffles under the planar surface 3 are used to control the flow back to the outlet 17 and ensure that the air contacts all parts of the inner surface 33 in the outlet half too.

[0158] The overall effect of the baffle structure is to direct the air flow widely and to the hottest parts so as to give best cooling of the press head 1.

[0159] In FIG. 4, a plan view from above of another embodiment of a press head 101 is provided. The press head 101 includes a substantially planar upper surface 103 and two tubes 105 at which locations the actuator, not shown, for moving the press head up and down are provided. A pin 107 which passes through the tube 105 is provided in each case to allow for the press head 101 is pivot relative to the actuator. Three braces 109 extend radially from each tube 105, together with a linking centre line rib 110 so as to stiffen the press head 101. The press head 101 is provided with two pairs of loops 111 which can be used to lift the press head 101 during assembly, maintenance and the like.

[0160] Also provided on the upper surface 103 are mounts 113 for connection to air pipes, not shown. The air pipes are connected to the outside of the dross press. One of the mounts 113 provides an inlet 115 into the press head 101. The other mount 113 provides an outlet 117 from the press head 101. The inlet 115 and outlet 117 are used to flow cooling air through the inside of the press head 101.

[0161] In the cross-sectional views of FIG. 5 and FIG. 6, the air flow within the press head 1 is illustrated.

[0162] The press head 101 has a lower surface 119 which is dome shaped. The lower surface 119 has protrusions 121 which extend therefrom. In this embodiment the protrusions 121 are provide with one ending from end to end along the long axis of the press head 101, with two protrusions 121 at 90° thereto extending across the narrower width of the press head 101. Other protrusion configurations are possible.

[0163] The press head 101 has a hollow 123 inside. The hollow 123 includes an upper baffle 125 which causes the air entering through inlet 115 to flow downwards towards inside of the wall 127 of the lower surface 119. The lower surface 119 is the part of the press head 101 which receives the most heat in use and so the cooling air is hence directed towards the hottest location so as to have maximum effect.

[0164] The wall 127 has a series of baffles in the form of ribs 131 provided on its inner surface 133. The ribs 131 cause the air to radiate outward from the inlet 115 and so reach all parts of the wall 127 in the half of the press head 101. A baffle 138 divides the inlet half from the outlet half, but has openings 135 at either end to allow air flow into the outlet half. Further baffles under the planar surface 103 are used to control the flow back to the outlet 117 and ensure that the air contacts all parts of the inner surface 138 in the outlet half too.

[0165] The overall effect of the baffle structure is to direct the air flow widely and to the hottest parts so as to give best cooling of the press head 101.

[0166] Load, Process and Unload Control

[0167] An example of a dross press 700 is shown in FIG. 7. It includes a side wall 702a, further side wall 702b, base 704 and roof 706. The rear wall and front wall 708 complete the structure.

[0168] In the roof 706 is an outlet 710 for air passing through the inside of the dross press 700. The outlet 710 leads to dust and/or off gas treatment units, not shown. Also in the roof are openings through which the actuators 712 can act upon the press head provided within the dross press 700.

[0169] The front wall 708 includes a door 714. This slides up and down within the front wall 708. As shown in FIG. 7, the door 714 is in the raised position.

[0170] The sequence of operations for the dross process 700 is as follows, according to this embodiment.

[0171] Firstly, a container unit 30 is provided. The container unit 30 provides a support structure 32 for a container 34. The container 34 is deepest in the middle and shallower at the periphery. The container 34 has an oval profile in plan, but other profiles can be used.

[0172] The support structure 32 includes a pair of recesses 38a, 38b which are configured to receive the lifting fork of a forklift truck, not shown. Other forms of lifting vehicle and/or apparatus could be used, such as cranes, but a forklift truck is most suited to the later operations.

[0173] The container unit 30 is brought to a loading location to receive the pile of dross. The dross may be loaded to the container 34 direct from a previous process, such as a furnace.

[0174] The container unit 30 is of metal, with steel alloy container 34. The materials can withstand temperatures in excess of 1600° C. The container 34 is constructed to encourage heat loss to the environment of the container unit 30.

[0175] Once loaded with dross, the container unit 30 is carried by the fork lift truck from the loading location to the dross press 700.

[0176] The door 714 on the dross press 700 is opened. The forklift truck advances the container unit 30 into the enclosure 718. As it does so, a part of the forklift and/or container unit 30 breaks a light beam across the mouth of the open door 714. This starts a sequence of events the controller for the dross press 700 expects.

[0177] The forklift truck is able to deposit the container unit 30 on a support surface 720.

[0178] The forklift truck can then be detached from the container unit 30 and all parts thereof exit the enclosure 718. As a result, the controller detects that the light beam across the mouth of the door is not longer being broken. This triggers the next step.

[0179] Until the light beam is restored, a safety interlock applies which prevents the door closing and/or the press head moving. The subsequent steps may progress automatically, subject to a correct situation being observed in each check.

[0180] In the next step, a further light beam is used to sense the level of the container unit 30, preferably in terms of the surface 722 around the top of the container 34. The level detected is interpreted by the controller and results in the identification of type of container unit 30 provided within the enclosure 718. For different types of container unit 30 and/or press head, the controller applies different forms and/or durations and/or sequences of subsequent steps. In particular, the level detected will be a factor in the extent of movement the actuators 712 go through to bring the press head towards the container unit 30.

[0181] FIGS. 8a and 8b illustrate two situations where different levels apply. In the first case, a deeper container 34 is provided into which the press head 800 requires a first extent of insertion. In FIG. 8b, a shallower container 34 is provided and a consequentially smaller press head 800 is used. This requires a lower extent of insertion and hence the detection of the different levels is important.

[0182] The system also provides for a check that the container unit 30 and hence the container 34 are in the correct position on the support surface 720 and/or relative to the press head above.

[0183] As a first step in the dross pressing, the controller closest the door 714. The door 714 slides down until the closed position is reached. The closed position, shown in FIG. 8, still provides a 15 cm gap between the bottom edge of the door and the support surface 720. This allows a flow path for cooling air into the enclosure 718 and out via the outlet 710.

[0184] Sensors may be provided which confirm to the controller than the closed position for the door has been reached before other steps are permitted.

[0185] The controller then triggers movement of the actuators 712. These have a press head mounted on them, inside the enclosure 718. Further movement of the actuators 712 and press head downward cause the press head to push into the dross in the container 34. The dross is compressed as a result. The downward motion continues until the press head reaches the lowest position allowed by the controller. This may be a position and/or when the press head or a part thereof contacts the container unit 30 or a part thereof.

[0186] During the time in the container 34 molten metal is able to drain from the container 34 through one or more apertures provided in it. The molten metal collects in a sow mould beneath, in the support structure 32. The drainage of molten metal particularly occurs when the dross is compressed by the press head. The press head also provides for the cooling of the dross.

[0187] The controller applies the press head to the container 34 and contents for a desired time and at a desired load or load profile. The controller may provide for rotation and/or other motion being applied to the press head.

[0188] The controller then brings the actuators 712 and hence press head up out of the dross and out of the container 34. The door 714 is then opened on the command of the controller.

[0189] The forklift truck returns, engages with the container unit 30. Once again, the breaking of the light beam causes the controller to active the interlock preventing door 714 movement and/or movement of the press head. If the forklift truck withdraws without the container unit 30, the light beam configuration indicates that the container unit 30 has not been withdrawn and so the interlock remains. Only if the container unit 30 is withdrawn is the controller able to recognise another sequence of the method starting.

[0190] Once withdrawn from the enclosure 718, the container unit 30 is moved to a storage location to complete its cooling. At this stage, the forklift truck brings a closure element 900 and places it on the container unit 30. The closure element 900 can be seen in FIG. 9.

[0191] The closure unit 900 is in the form of a cover element 902 which is substantially planar in terms of its upper surface 904. The upper surface 904 has a pair of recesses 904a, 904b which are configured to receive the lifting fork of a forklift truck, not shown. The extent of the upper surface 904 is such as to cover the receiving location within the container 34. A contact surface on the underside of the closure element 900 abuts a contact surface on the upper of the container unit 30.

[0192] The upper surface 904 is provided with a series of protrusions 906 which increase the surface area of thereof and hence increase heat loss to the environments of the apparatus formed by the container unit 30 and closure element 900 combination.

[0193] The under surface of the closure element 900 is provided with a series of further protrusions which extend into contact with the dross. These serve to increase the area of the dross in contact with the closure element 900 and hence increase heat transfer to the closure element 900.

[0194] Once the dross has cooled to the required degree, the dross may be extracted and reprocessed. Each closure element 900 is provided with a pair of recesses 904a, 904b for this purpose to allow it to be lifted off the container unit 30 to allow emptying.

[0195] Air Flow Management

[0196] As shown in FIG. 10 and FIG. 11, the cooling air 1000 for the press head 1002 is kept completely separate from the cooling air 1004 for the space 1006 within the enclosure 1008. The cooling air 1004 for the space 1006 also has a role in dust collection and control and in off gas collection and control.

[0197] In more detail, the cooling air 1004 for the space 1006 within the enclosure 1008 is drawn through the enclosure 1008 as a result of an air pump or blower, not shown, generating a pressure below atmospheric in conduit 1010. The conduit 1010 leads to an off-gas and dust treatment unit. The majority of the air flow into the enclosure 1008 from the environment 1012 in which the enclosure 1008 is positioned, is through the upper gap 1014. A lower proportion is drawn through lower gap 1016. As a consequence, the air velocity through the upper part of the enclosure 1008 is higher to ensure all off-gas and dust is effectively swept from the enclosure 1008.

[0198] The ratio of the volume of air passing through the upper gap compared with the lower gap may be in excess of 1.5 to 1, preferably in excess of 1.75 to 1, more preferably in excess of 2.5 to 1 and ideally in excess of 3.5 to 1.

[0199] The velocity of air in the upper gap may be at least 2 times that in the lower gap, preferably at least 3 times, more preferably at least 4 times and ideally at least 5 times. As shown in FIG. 11, the cooling air 1000 for the press head 1002 is drawn through feed conduit 1020 to a blower 1022 and then to flow conduit 1024. The air flow entering the conduit 1020 is preferably taken from outside of the plant or another dust free environment. The flow may be filtered to ensure it is dust free. The flow conduit 1024 enters the enclosure 1008 and through flexible connectors 1026 passes the cooling air 1000 into the top of the press head 1002. The cooling air 1000 is in contact with the inside surface of the domed press head surface which contacts the hot by-product. The cooling air 1000, now at a raised temperature, leaves the press head and passes through flexible connector 1028, then out of the enclosure 1008 and through exit conduit 1030. The exit conduit may feed the cooling air 1000 to a treatment unit, but generally this is not necessary as the cooling air 1000 is kept apart from the dust and off-gases all the time it is within the process plant.