GB1565389A

GB1565389A - Skimmer

Info

Publication number: GB1565389A
Application number: GB5319076A
Authority: GB
Original assignee: Esmil Envirotech Ltd
Current assignee: Esmil Envirotech Ltd
Priority date: 1976-12-20
Filing date: 1976-12-20
Publication date: 1980-04-23

Description

(54) SKIMMER (71) We, ESMIL-ENVIROTECH LIMITED., a British Company of Station Road, St.

Neots, Huntingdon, Cambridgeshire PEl9 100, do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed to be particularly described in and by the following statement:- The invention relates to a skimmer for use with a liquid-containing tank, preferably circular, and to a tank equipped with a skimmer.

It is generally known to use skimming devices for treating a liquid containing floating solids e.g. scum, which are to be removed. A conventional way of removing the floating material is by sweeping it with a rotating radial arm, which is provided with a flexible or hinged blade, into a discharge box having an opening slightly above the liquid level. Other known means of removal of floating material employ, for example, specially adapted belt-conveyors and slotted tubes.

It has been proposed to employ a radially extending element or arm having the cross sectional shape of a spiral, this element or arm being rotated about its axis. The purpose of this shape and this movement is to scoop up the floating material and then discharge it in the axial direction through the rotating arm.

It is the object of the present invention to provide a skimming device, which can have an improved efficiency for skimming floating materials.

According to this invention, there is provided a skimmer for use with a liquidcontaining tank, having an elongated hollow member which when installed for use extends radially across the liquid surface from a central vertical axis in the tank, first drive means for rotating the member around said vertical axis and second drive means for rotating the member about a second axis extending radially from said vertical axis, wherein the member carries a plurality of scoops which are arranged around its periphery, and a launder is provided which extends longitudinally within said member and, when the skimmer is positioned in the tank and in use, is stationary with respect to said second axis but moves with the member around said vertical axis, the member having openings so that in use material picked up by the scoops is deposited into the launder as the member rotates about the second axis.

In this arrangement a plurality of scoops is used to collect the floating material, which discharge into the launder when they rotate about the second axis of the member. As this launder is mounted stationary with respect to the axis of the member within the skimmer assembly, it may collect the floating material from all the scoops, and discharge them at one end. Preferably the launder slopes downwardly in the radially inward direction towards said vertical axis.

The member is preferably of cylindrical form. The cylinder may either be a single construction made of a perforated metal sheet or plate, or it may consists of axially spaced supporting rings for the scoops. In both cases the cylinder should be constructed with sufficient open surface that the material discharged from the scoops should completely fall into the launder.

In principle the member could be driven around its axis in either direction, irrespective of the direction of travel of the member as it sweeps around the tank. Yet it has been found that best results are obtained if the two said drive means are connected to the member so that in use the scoops in their lowermost position during their movement around said second axis move in the same direction of travel as the member in its movement around the said vertical axis.

Although the launder may slope in either radial direction, the easiest manner of discharge of the collected material is obtained by having it slope inwardly as mentioned above. In that case the launder may be made to discharge into a vertical duct which is centrally arranged in the tank.

Depending upon the type and the amount of the floating material with respect to the quantity of liquid to be treated, the speed of rotation of the member around the said second axis and/or around the vertical axis may be adapted in order to obtain optimal results. A further improvement may be obtained if detecting means are provided for monitoring the flow volume being discharged by the launder, said detecting means controlling the speed of rotation of the member around said second axis and/or the vertical axis. It is clear also that the level of the liquid and/or the floating material with respect to the path of travel of the scoops may influence the efficiency of the installation. Therefore it may be advantageous also to provide means for varying said level. Usually the easiest way to do so is to control an overflow weir.

Although the skimming device may be used separately, it may also be employed in combination with a supplementary clarifies installation, e.g. one of the usual type equipped with a bottom-raking mechanism.

One embodiment of the invention will now be described by way of example with reference to the accompanying diagrammatic drawings, in which: Figure 1 is a diagrammatic plan view of a part of an apparatus including a skimming device embodying the invention Figure 2 is a sectional view on the line II-II in Figure 1, and Figure 3 is a diagrammatic sectional view on the line III-III in Figure 2.

In Figure 1, reference number 1 indicates the peripheral wall of a conventional circular liquid-containing tank, having an overflow at 2.

A radially extending skimming element 3 is mounted to rotate around a centre bearing 4 on a column 4a and is provided with scoops 5. A skimmer drive means 6 is provided to rotate the element 3 around its own axis, and a further traction drive means 7 is provided to move the element 3 around the central bearing 4. The traction drive means 7 rests upon and moves along the upper edge of the wall 1.

It is remarked, however, that in an alternative possible design, centre drive means may be used for element 3 instead of peripheral drive means. whether peripheral drive means or central drive means are to be preferred depends upon the dimensions and the application of the installation.

Around the columns 4a and below the central bearing 4 a centre well 8 is provided, the function of which will be explained later.

Referring to Figures 2 and 3, it can be seen that the element 3 consists of a drum or cylinder 9 of steel sheet or plate having perforations in the form of slots, carrying scoops 5, and contains a collecting trough or launder 10 which discharges into the centre well 8. The launder 10 is V-shaped and the scoops have their openings directed so that the direction of scooping is tangential to the cylinder surface. Each scoop extends substantially the whole length of the drum 9.

The launder 10 is mounted by supports 10a so that it does not rotate with the drum 9 about the second (horizontal) axis, but it does rotate with the drum about the vertical axis. The bottom of the launder slopes downwardly towards the well 8 and ends above an outwardly flaring end portion 9a of the drum.

Arrow 11 (Figures 1 and 3) indicates the direction of movement of the whole skimmer around the tank and arrow 12 (Figures 1 and 3) indicates the direction of rotation of the drum 9 about its axis. It can be seen that the scoops 5 are moving around the horizontal axis of the drum in the same direction of movement as the whole skimmer around the central vertical axis when they are in their lowermost positions, i.e. are picking up floating matter. Preferably as shown in Figure 3, the scoops just dip below the liquid level 13 which is desirably maintained at the correct level to achieve this. As the scoops pass above the launder in their rotation, they deposit picked up material through the perforated drum into the launder.

Skimmers of the invention suitably designed for the particular purpose, are applicable in very many fields where floatable solids or liquids, are to be skimmed from a fluid. Typical applications are fibre recovery in pulp or paper plants, cleaning of industrial or mixed wastes, and oil or emulsion separation from liquids.

WHAT WE CLAIM IS: l. Skimmer for use with a liquid-containing tank, having an elongated hollow member which when installed for use extends radially across the liquid surface from a central vertical axis in the tank, first drive means for rotating the member around said vertical axis and second drive means for rotating the member about a second axis extending radially from said vertical axis, wherein the member carries a plurality of scoops which are arranged around its periphery, and a launder is provided which extends longitudinally within said member and, when the skimmer is positioned in the tank and in use, is stationary with respect to said second axis

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **.

radial direction, the easiest manner of discharge of the collected material is obtained by having it slope inwardly as mentioned above. In that case the launder may be made to discharge into a vertical duct which is centrally arranged in the tank.

Depending upon the type and the amount of the floating material with respect to the quantity of liquid to be treated, the speed of rotation of the member around the said second axis and/or around the vertical axis may be adapted in order to obtain optimal results. A further improvement may be obtained if detecting means are provided for monitoring the flow volume being discharged by the launder, said detecting means controlling the speed of rotation of the member around said second axis and/or the vertical axis. It is clear also that the level of the liquid and/or the floating material with respect to the path of travel of the scoops may influence the efficiency of the installation. Therefore it may be advantageous also to provide means for varying said level. Usually the easiest way to do so is to control an overflow weir.

Although the skimming device may be used separately, it may also be employed in combination with a supplementary clarifies installation, e.g. one of the usual type equipped with a bottom-raking mechanism.

One embodiment of the invention will now be described by way of example with reference to the accompanying diagrammatic drawings, in which: Figure 1 is a diagrammatic plan view of a part of an apparatus including a skimming device embodying the invention Figure 2 is a sectional view on the line II-II in Figure 1, and Figure 3 is a diagrammatic sectional view on the line III-III in Figure 2.

In Figure 1, reference number 1 indicates the peripheral wall of a conventional circular liquid-containing tank, having an overflow at 2.

A radially extending skimming element 3 is mounted to rotate around a centre bearing 4 on a column 4a and is provided with scoops 5. A skimmer drive means 6 is provided to rotate the element 3 around its own axis, and a further traction drive means 7 is provided to move the element 3 around the central bearing 4. The traction drive means 7 rests upon and moves along the upper edge of the wall 1.

It is remarked, however, that in an alternative possible design, centre drive means may be used for element 3 instead of peripheral drive means. whether peripheral drive means or central drive means are to be preferred depends upon the dimensions and the application of the installation.

Around the columns 4a and below the central bearing 4 a centre well 8 is provided, the function of which will be explained later.

Referring to Figures 2 and 3, it can be seen that the element 3 consists of a drum or cylinder 9 of steel sheet or plate having perforations in the form of slots, carrying scoops 5, and contains a collecting trough or launder 10 which discharges into the centre well 8. The launder 10 is V-shaped and the scoops have their openings directed so that the direction of scooping is tangential to the cylinder surface. Each scoop extends substantially the whole length of the drum 9.

The launder 10 is mounted by supports 10a so that it does not rotate with the drum 9 about the second (horizontal) axis, but it does rotate with the drum about the vertical axis. The bottom of the launder slopes downwardly towards the well 8 and ends above an outwardly flaring end portion 9a of the drum.

Arrow 11 (Figures 1 and 3) indicates the direction of movement of the whole skimmer around the tank and arrow 12 (Figures 1 and 3) indicates the direction of rotation of the drum 9 about its axis. It can be seen that the scoops 5 are moving around the horizontal axis of the drum in the same direction of movement as the whole skimmer around the central vertical axis when they are in their lowermost positions, i.e. are picking up floating matter. Preferably as shown in Figure 3, the scoops just dip below the liquid level 13 which is desirably maintained at the correct level to achieve this. As the scoops pass above the launder in their rotation, they deposit picked up material through the perforated drum into the launder.

Skimmers of the invention suitably designed for the particular purpose, are applicable in very many fields where floatable solids or liquids, are to be skimmed from a fluid. Typical applications are fibre recovery in pulp or paper plants, cleaning of industrial or mixed wastes, and oil or emulsion separation from liquids.

WHAT WE CLAIM IS: l. Skimmer for use with a liquid-containing tank, having an elongated hollow member which when installed for use extends radially across the liquid surface from a central vertical axis in the tank, first drive means for rotating the member around said vertical axis and second drive means for rotating the member about a second axis extending radially from said vertical axis, wherein the member carries a plurality of scoops which are arranged around its periphery, and a launder is provided which extends longitudinally within said member and, when the skimmer is positioned in the tank and in use, is stationary with respect to said second axis

but moves with the member around said vertical axis, the member having openings so that in use material picked up by the scoops is deposited into the launder as the member rotates about the second axis.
2. Skimmer according to claim 1 wherein the launder is disposed within said member so that when the skimmer is positioned in the tank said launder slopes downwardly in the radially inward direction with respect to the said vertical axis.
3. Skimmer according to claim 1 or claim 2 wherein said member is cylindrical in shape.
4. Skimmer according to claim 3 wherein said member is formed of perforated metal sheet or plate.
5. Skimmer according to claim 3 wherein the member comprises a plurality of axially spaced supporting rings for said scoops.
6. Skimmer according to any one of the preceding claims wherein the two said drive means are connected to the member so that in use the scoops, in their lowermost position during their movement around said second axis, have the same direction of travel as the member in its movement around the said vertical axis.
7. Skimmer according to any one of the preceding claims wherein each scoop extends longitudinally substantially the full length of said member.
8. Skimmer substantially as herein described with reference to and as shown in the accompanying drawings.
9. A tank for liquid, preferably a circular tank, having a skimmer according to any one of the preceding claims.
10. A tank according to claim 9 wherein the launder of the skimmer discharges into a vertical duct centrally arranged in the tank.
11. A tank according to claim 9 or claim 10 wherein detecting means are provided for monitoring the flow volume being discharged by the launder, said detecting means controlling the speed of rotation of the member around said second axis and/or around the said vertical axis.
12. A tank according to any one of claims 9 to 11 which is combined with a supplementary clarifier installation.
13. A tank substantially as herein described with reference to and as shown in the accompanying drawings.